1.0.1 This code is prepared for improving design level of industrial metallic pipeworks and ensuring their design quality.

1.0.2 This code is applicable for industrial metallic pipings and those with non-metallic lines working at a nominal pressure below or equal to 42MPa.

1.0.3 This code is not applicable for design of the following pipings:

10.3.1    The pipings attached to the equipment or machines in a whole plant designed by a manuacturer;

1.0.3.2             Special pipings in a nuclear power unit;

1.0.3.3             Long-distance delivering pipings;

1.0.3.4             Pipings in a mine;

1.0.3.5   Pipings for heating, ventilating, and air conditioning, as well as pipings with a noncircular section;

1.0.3.6   The underground or indoor water supply and drainage pipings, and fire extinguishing purpose water supply pipings;

1.0.3.7             Pipings for foam, carbon dioxide, or other type fire extinguishing systems.

1.0.4 The pressure used in this code all mean gauge pressures unless otherwise specified.

1.0.5 Design of any industrial metallic piping should meet the stipulations in current national standards concerned, in addition to executing this code.

 

 

 

2.1.1  Category A1 fluid

For the purpose in this code, it refers to the highly toxic fluid that can seriously poison the individual who contacts with or inhale the fluid when a small amount of the fluid leaks out, and cannot be cured even he/she contacts it no any longer. The fluid is corresponding to the (extremely hazardous) toxic substance in Grade I stipulated in for the current national standard “Classification of health hazard levels from occupational exposure to toxic substances”, GB5044.

2.1.2  Category A2 fluid

For the purpose in this code, it refers to the toxic fluid that can poison the individual who contacts it to different extents, but he/she may be cured after being out of contact. The fluid is corresponding to the (high, moderately, or lightly hazardous) toxic substance in Grade II or stipulated below in for the current national standard “Classification of health hazard levels from occupational exposure to toxic substances”, GB5044.

2.1.3  Category B fluid

For the purpose in this code, it refers to the fluid that may be a gas or a liquid that can generate a gas by flash evaporation in the circumstance or under the operation condition. The fluid can be ignited and continuously burn in air.

2.1.4  Category D fluid

For the purpose in this code, it refers to the incombustible, and nontoxic fluid that is used in the case of the design pressure below or equal to 1.0MPa and design temperature between –20 and 186℃.

2.1.5  Category C fluid

For the purpose in this code, it refers to the incombustible, and nontoxic fluids excluding those fluids falling Category D.

2.1.6  Piping

So-called piping means a facility that consists of piping components, pipe supports and hangers, and others, and is used to deliver, distribute, mix, separate, drain, measure, or control flow of a fluid.

2.1.7  Piping system

A piping system means a set of pipings connected each with other and classified according to the type of fluid and the design condition.

2.1.8  Piping components

Piping components are components, including pipes, pipe fittings, flanges, gaskets, fasteners, valves, and piping specialties, used to connect or assemble into a piping.

2.1.9  Piping specialties

So-called piping specialties refer to non-standard piping components, which are specially manufactured in light with the engineering design condition, including expansion joints, compensators, special valves, rupture disks, fire arrestors, filters, flexible connectors, hoses, and others.

2.1.10  Minter bends

A welded bend made (elbow) of pipes or steel sheets, is spliced from pipe runs with mitre weldings not perpendicular to the vertical axis of the pipes.

2.1.11  Branch connections

A structure connecting one or more branch(es) onto a main pipe, including integrally -reinforced pipe fittings and the branch connections with or without reinforced welded structure.

2.1.12  Raised face

This is one of seal face forms for flanges. The bulgy flat seal face is within the internal side of the boltholes as assembling. Its symbol is RF.

2.1.13  Full face

It is one of seal face forms for flanges, within which outer diameter the entire area is a flat seal face. Its symbol is FF.

2.1.14  Liquid collecting pocket (drip leg)

A condensate-collecting purpose pocket-like device set the low point of a gas or vapor piping.

2.1.15  Pipe Supports and hangers

A generic name used to entitle various structures supported pipings or restricted displacement of pipings as a whole, excluding civil structures.

2.1.16  Anchors

A support that not only can make a piping system produce neither linear displacement nor angular displacement at a supporting point, but also may bear various loads on the piping in different directions.

2.1.17  Sliding support

A rack with the sliding supporting face may restrict vertically downward displacement of a piping, but does not restrict horizontal displacement of the piping for thermal expansion or contraction, and bears the vertical load including of the deadweight of the piping.

2.1.18  Rigid hangers

A pipe rack structure with a hinged hanging rod, may restrict vertically downward displacement of a piping, but does not restrict horizontal displacement of the piping for thermal expansion or contraction, and bears the vertical load including of the deadweight of the piping.

2.1.19  Guides

A rack that may prevent rotation caused from a moment of force or a torsional moment, guide one or more direction(s), but the piping still may move in the given axial direction. When it is used in a horizontal piping, the guide bears the vertical load including of the deadweight of the piping in addition to the above-mentioned function. Usually, the structure of a guide has a spacing function in one or two axial direction(s).

2.1.20  Restraints

A rack that can restrict the displacement, which may be linear or angular displacement in one or more direction(s), of the piping in the designated direction at a point. The restraint with a prescriptive displacement value is called the setting value restraint.

2.1.21  Vibrating eliminators

A device that can control high-frequent and low-amplitude vibration or low-frequent and high-amplitude shake of a piping system, but does not restrain its thermal expansion or contraction.

2.1.22  Snubbers (dampers)

A device that can control instantaneous impact load upon a piping or highspeed vibration displacement of a piping system, but does not restrain their thermal expansion or contraction.

2.1.23  Severe cyclic condition

This refers to such conditions that the maximum displacement stress range,σ_E, calculated for a piping exceeds 0.8 times of the allowable displacement stress range, that is 0.8[σ]_A, and the number of equivalent cycles, N, is larger than 7,000 or a design-decided condition produced an equivalent effect.

2.1.24  Stress intensification factor

The ratio of the maximum bending stress leading fatigue failure of a component of a non-straight piping for the sake of a bending moment to the maximum bending stress leading fatigue failure of a component of a straight piping with the same diameter and thickness under action of the same bending moment is called stress intensification factor. There are two types of stress intensification factors, in-plane and out-plane, according to different planes the bending moment and the component are in.

2.1.25  Displacement stress range

The stress that is calculated from the displacement caused from thermal expansion of a piping is called displacement stress range. The stress calculated from the full compensation value from the lowest temperature to the highest temperature is called the calculated maximum displacement stress rang.

2.1.26  Externally imposed displacements

This refers to the displacement of the calculated piping system imposed from the end of the piping system due to thermal expansion of the equipment or other connected piping, or another displacement.

2.1.27  Cold spring

The so-called cold spring refers to such a process that an elastic deformation is imposed upon the piping prior to its installation to produce an anticipated displacement and stress, and reduce the acting force and the moment on the piping end under the initial thermal condition.

2.1.28  Flexibility factor

This factor represents the extent by which the flexibility of a piping component increases as it bears a moment relative to a straight piping. That is, in a piping component, the ratio of the angular deformation of the component per unit length generated under action of a given moment to the angular deformation of a straight piping with the same diameter and thickness under action of the same moment.

2.1.29  Utility piping

Forming a contrast with the process piping, the utility piping means those pipings for common fluids in various operations of a factory or unit.

2.1.30  Piping and instrument diagram

The piping and instrume

This diagram is called P&ID or PID for short. There are the symbols indicating the piping system, and instrument and gauges connected, and the identification codes for different pipings, in addition to equipment and apparatus shown on this diagram.

 

A A1     A2     A3 A4 A5     Ak B C1t   C1m   C1r   C C1     C2 Cf Ch Cp Cs Cv C.S.C.(L.C.) C.S.O.(L.O.) d d0 d1   dG   dX   DN Di DiL DiS Do DOL DOS Dr Ec Ej Eh E20 FH fr   fs f g h h1 h2 h3 hx i ii io is k K K1 K2 K3 KR KS KT L Le Lf Ls LSL   LSS   M MA   MB       ME M’E   Mi Mo Mt MX MY MZ n N   NE   Nj   P PA Pm PN PT QL   QS   R R1 Rc   Rc1   RE   Rh   Rm r r0 r1, r2, r3 rj     rm rp rx   S T T1 T2 Tc   Tt Tm t tb tc teb tFn tL tL1 tL2 tLc tLL tLS tm tp tpd tr ts tsd tse tsn tt ttn tx   tw υ υc W WB Wo X Xmin Y Ys a   a1 a0 β θ     θn δ δave δmax δ1 δ2 D DPf DPk DPt h ρ λ σb   σbt σ tD σE σj   σL   σnt   σs(σ0.2)   σst(σ0.2t)   σT [σ]T [σ]t [σ]0   [σ]1 [σ]2 [σ]A [σ]c   [σ]h   [σ]x   [σ] tRP [σ] tM

— —     —     — — —     — — —   —   —   — —     — — — — — — — — — — —   —   —   — — — — — — — — — — — — — —   — — — — — — — — — — — — — — — — — — — — — — — — —   —   — —   —       — —   — — — — — — — —   —   —   — — — — — —   —   — — —   —   —   —   — — — — —     — — —   — — — — —   — — — — — — — — — — — — — — — — — — — — — — — —   — — — — — — — — — — —   — — — —     — — — — — — — — — —— — — —   — —   — —   —   —   —   —   —— — —   — — — —   —   —   —   —

The reinforced area needed for the open on a main pipe. The redundant metallic area of a main pipe within the reinforced range, excluding both the calculated thickness and the additional thickness used to bear internal and external pressures. The redundant metal area of a branch within the reinforced range, excluding both the calculated thickness and the additional thickness used to bear internal and external pressures. The area of the fillet weld within the reinforced rang. The area of the additional reinforcing plate within the reinforced rang. The redundant metallic area of an extruded branch within the reinforced range, excluding both the calculated thickness and the additional thickness used to bear internal and external pressures. Impact power upon a material. The effective width of a reinforced zone. The allowance for the possibly attenuated (minus deviation) of a branch in the thickness. The allowance for the possibly attenuated (minus deviation) of a main pipe in the thickness. The allowance for the possibly attenuated (minus deviation) of a reinforcing plate in the thickness. The sum of all allowances. The allowance for the possibly attenuated in the thickness, including minus deviations caused from processing, fluting, depth of thread, and material thickness. The allowance for corrosion or abrasion. A correction factor The tolerance factor in piping pressure loss. Constant-pressure specific heat Cold spring ratio. Constant-volume specific heat. Lock in closed state (not allow to open without approval). Lock in opened state (not allow to close without approval). The inner diameter of a branch after deducting the allowance in thickness. The nominal diameter of a branch. The major diameter of the diagonal cut joint on a main pipe after deducting the allowance in thickness. The inner diameter of the gasket for a female or face flange, or average diameter of a ring groove gasket. The inner diameter of an extruded branch after deducting the allowance in thickness. The nominal diameter of a pipe or pipe fitting. The inner diameter of a pipe or pipe fitting. The inner diameter of the larger end of a reducer. The inner diameter of the smaller end of a reducer. The outer diameter of a pipe or pipe fitting. The outer diameter of the larger end of a reducer. The outer diameter of the small end of a reducer. The outer diameter of a reinforcing plate. The quality factor of a casting. Weld joint factor. Elastic modulus of a piping material at the higher or lowest temperature. Elastic modulus of a piping material at the installation temperature. Working load. The ration between the allowable stresses of the materials for the reinforcing plate and the main pipe. Changing factor of load. Reduction factor of the displacement stress range of a piping. Acceleration of gravity. Dimension factor. The normally reinforced effective height at the outer side of a main pipe. The effective reinforced height for a branch. The inward dented depth of a flat cap. The height of a extruded branch. Stress intensification factor. Stress intensification factor in a plane. Stress intensification factor out a plane. Gradient of a piping. The adiabatic index of a gas. Flexibility factor. A factor related to the structure of a flat cap. Empirical value for a minter bend. The reinforcing factor for an extruded branch. Resistance coefficient. The stiffness of a spring. Allowable stress factor. The length of a piping. The equivalent length of valves and pipe fittings. The shorter edge length of the end section of a minter bend. Spacing between supports or hangers. The length of the reinforced section of a straight pipe connected to the larger end of a reducer. The length of the reinforced section of a straight pipe connected to the smaller end of a reducer. The molecular weight of a gas. The resultant moment from action of the deadweight and other continuous external load on the section of the piping. The resultant moment from action of accidental load caused from the counterforce of the safety valve or relief valve, transient change of flow and pressure in a piping, wind force, or earthquake on the section of the piping. The equivalent resultant moment of thermal expansion. The resultant moment in which the stress intensification factor is not counted. The bending moment from thermal expansion in the plane. The bending moment from thermal expansion out the plane. The twisting moment from thermal expansion. The moment in the direction of X- coordinate axis. The moment in the direction of Y- coordinate axis. The moment in the direction of Z- coordinate axis. Ordinal. The equivalent number of full displacement cycles in the estimated service life of a piping system. The cyclic number related to the calculated maximum displacement stress range,σE. The cyclic number related to the displacement stress range,σj calculated for a value less than the full displacement. The design pressure. The allowable stress at the design temperature. The maximum allowable inner pressure of a minter bend. The nominal pressure. The test pressure. The stress intensification factor for connection of the larger end of a reducer with a straight pipe. The stress intensification factor for connection of the smaller end of a reducer with a straight pipe. The curvature radius of a circular arc bend. The curvature radius of a minter bend. The force and moment acted by a piping on the equipment or the end point at the installation temperature in the initial period of operation. The force and moment acted by a piping on the equipment or the end point at the installation temperature after self-recovery The force and moment acted by a piping on the end point that is calculated based on E20 and full compensation The force and moment acted by a piping on the equipment or the end point at the highest or lowest temperature in the initial period of operation. The average radius of the main pipe. The fillet radius in the flat cap. The average radius of a pipe or pipe fitting. The transitional radius of the reinforced position of the branch. The ratio of the displacement stress range,σj calculated for a value less than the full displacement to the calculated maximum displacement stress range,σE. The average radius of a branch. The outer radius of the reinforced position of a branch. The curvature radius at the corner of the outer profile in the plane of the axes of a main pipe and its branch. The spacing at the central line of the miter section of a minter bend. Gas temperature. The thickness of a butt weldment at the thiner side. The thickness of a butt weldment at the thicker side. The thickness of a tee at the round corner (the intersection position of the main pipe and the branch) . The calculated thickness of the main pipe. The nominal thickness of the main pipe. The thickness of the end of a half coupling. The effective thickness of a branch at the reinforced position. The calculated effective thickness of a fillet weld. The effective thickness of the branch of a tee. The nominal thickness of a pipe fitting. The nominal thickness of a reducer. The nominal thickness of a reducer at the larger end. The nominal thickness of a reducer at the smaller end. The calculated thickness of a reducer at the conic position. The calculated thickness of a reducer at the larger end. The calculated thickness of a reducer at the smaller end. The calculated thickness of a blind flange. The calculated thickness of a flat cap. The design thickness of a flat cap or blind flange The nominal thickness of a reinforcing plate. The calculated thickness of a straight pipe. The design thickness of a straight pipe. The effective thickness of a straight pipe. The nominal thickness of a straight pipe. The calculated thickness of a branch. The nominal thickness of a branch. The effective thickness for extruding a branch on the outer surface of the main pipe after reducing the allowance for thickness. The dimension of a sockolet. The average flow velocity. The sound velocity or the critical flow velocity of a gas. The cross section factor. The net section factor of a reduced tee branch. Mass flow rate. The dimension of the fillet leg weld inside a flange. The minimum dimension of a fillet weld leg. A coefficient. The bending deflection of a piping due to its deadweight. The angle by which the direction of a welding line on a minter bend changes (the included angle between the two adjacent miter lines). The included angle between the axes of the branch and the main pipe. The average linear expansion coefficient of a metallic material. The included angle between the bevel edge and the axial line of a reducer. A half of the angle by which the direction of a welding line on a minter bend changes (a half of the included angle between the two adjacent miter lines). The transitional angle at the reinforced position of a branch. The maximum calculated elongation of fiber. The average value of the unfitness of a butt joint. The maximum value of the unfitness of a butt joint. The nominal thickness of a parent metal. The effective thickness of a coating metal after reducing the allowance. The vertical thermal displacement of a piping. The pressure loss due to friction on a straight piping. The local pressure loss due to friction. Total pressure loss of a piping A coefficient related to the structure of a flat cap. The density of a fluid. The friction coefficient of a fluid. The lower limit value of the tensile strength of a material at standard temperature-pressure. The tensile strength of a material at the design temperature. The average value of the creep rupture strengths of a material at the design temperature for 100tousand hrs in a creep test. The calculated maximum displacement stress range. The displacement stress range calculated for a value less than the full displacement. The sum of the longitudinal stresses produced by pressure, gravity, and other continuous load in the piping. The creep limit of a material at a creep rate of 1% at the design temperature for 100tousand hrs in a creep test. The yield point of a material at the standard normal temperature (or 0.2% yield strength). The yield point of a material at the design temperature (or 0.2% yield strength). The hoop stress of a component under the test condition. The allowable stress of a material at the test temperature. The allowable stress of a material at the design temperature. The allowable stress of an integrally clad metallic material at the design temperature. The allowable stress of the parent metal at the design temperature. The allowable stress of the coating metal at the design temperature. The allowable displacement stress rang. The allowable stress of a metallic material in cold status (at the estimated lowest temperature) in the analyzed displacement cycle. The allowable stress of a metallic material in hot status (at the estimated highest temperature) in the analyzed displacement cycle. The allowable stress of a material at the calculated temperature adopted when the thickness of a component is determined. The allowable stress of the material used for a reinforcing plate at the design temperature. The allowable stress of the material used for a main piping at the design temperature.

 

 

 

 

3.1.1 Design of a piping should be performed according to process conditions, such as pressure, temperature, characteristics of the fluid and other, taking the circumstance and various load conditions in account.

3.1.2 Determination of the design pressure should meet the following stipulations:

3.1.2.1 The design pressure of a piping and each component of its should not be less than the pressure occurred when a severest condition appears due to coupling of an internal pressure or an external pressure with temperature in operation. The severest condition should be taken as a parameter for calculation of the largest thickness of the piping component is required, and of the highest nominal pressure in the strength calculation. But, the above-said design pressure should not include the non-recurrently fluctuant value of pressure allowed in this section.

3.1.2.2 For any of the following pipings in special conditons, its design pressure value should be taken to compare with the result selected as Clause 3.1.2.1, whichever is larger.

3.1.2.3 A vacuum piping should be designed according to the external pressure it may bear, if equipped with a safety control device, its design pressure should be 1.25 times of the difference between the internal and external pressures, or 0.1MPa, whichever is lower; if with no safety control device, its design pressure should be taken to be 0.1MPa.

3.1.2.4 The design pressure of a piping with the pressure-relieving device should not be less than the pressure under which the pressure-relieving device opens.

3.1.3 Determination of the design temperature should meet the following stipulations:

3.1.3.1 The design temperature of a piping should be the temperature occurred when a severest condition appears due to coupling of pressure with temperature in operation. For the piping operated at a temperature below 0℃, influence of the fluid in it and the ambient temperature should be taken into account. In this case, the design temperature should be equal to or below the lowest temperature the material of the piping may reach.

3.1.3.2 For the piping heated by its tracer or jacketed pipe, the externally heating temperature or the temperature of the fluid inside the pipingshould be taken as the design temperature, whichever is higher.

3.1.3.3 In the piping without thermo-insulating layer, different piping components may be at different temperatures, their design temperatures should meet the following stipulations:

（1）In the case of a fluid temperature below 65℃, the design temperature of a piping component may be the same as that of the fluid;

（2）In the case of a fluid temperature equal to or over 65℃, the design temperature of a piping component should not be less than the following value, unless calculated as heat transfer or there is an lower average wall-temperature determined by the test:

95% of the fluid temperature for valves, pipes, flange spools, welded pipe fittings, and other piping components with the similar thickness;

90% of the fluid temperature for flanges, including those on the pipe fittings and valves, but excluding loose flanges;

85% of the fluid temperature for loose flanges;

80% the fluid temperature for the fasteners for flanges.

3.1.3.4 The design temperature of a piping with external thermo-insulation should be determined as Clauses 3.1.3.1 and 3.1.3.2. Other temperature may be adopted if there otherwise is a calculated, tested, or measured result available.

3.1.3.5 The design temperature of a piping with internal thermo-insulation should be determined based on heat transfer calculation or test.

3.1.3.6 For a piping with a non-metallic material liner, its design temperature should be taken to equial to the highest working temperature of the fluid. When there is no external thermo-insulating layer, the design temperature of the external metal may be determined by heat transfer calculation, or test, or as Clause 3.1.3.3.

3.1.4 Effective measures should be taken to copy with the following environmental influences:

3.1.4.1 For cooling of gas or vapor in a piping, its pressure drop value should be determined. When a vaccum generates in the piping, which should be able to withstand the external pressure at the low temperatire, or the effective preventive measure should be taken to destroy vaccum.

3.1.4.2 A piping component should be able to withstand or eliminate the increasing pressure due to thermal expansion of the static fluid, otherwise, the effective preventive measure should be taken.

3.1.4.3 For the piping its temperature may be below 0℃, proper measures should be taken to prevent the external surfaces of shutoff valves, control valves, pressure–relieving devices, and the moving parts of other piping components from icing up.

3.1.5 A piping should be able to withstand the following dynamic loads:

3.1.5.1 A piping should be able to withstand impact loads caused from hydraulic impact, strike of liquid or solid, and others.

3.1.5.2 An outdoor abovegrade piping should be able to withstand the wind load.

3.1.5.3 The piping located in an earthquake region should be able to withstand the horizongtal force cuased by the earthquake, and should conform to the stipulations in current national aseismatic standard concerned.

3.1.5.4 The design on piping arrangement and support should be able to eliminate influence of harmful vibration caused from impact, pressure fluctuation, resonance of machines, and wind load on the pipings.

3.1.5.5 The design on piping arrangement and support should make them be able to withstand the counterforce caused from pressure reduction and discharge of the fluid.

3.1.6 The static load born by th piping should include fixed loads and live loads. Live loads should include the gravity of the delivered fluid or of the fluid for test, the gravity of ice, and/or snow in a cold region, and other temporary live loads. Fixed loads should include deadweights of piping components and thermo-insulating materials, and other permanent loads born by the piping.

3.1.7 Influence of the following thermal expansion or contraction should be analyzed in design:

3.1.7.1 The force and moment from thermal expansion or contraction acted upon the restrained or fixed piping.

3.1.7.2 The stress in and load upon the piping wall from galloping temperature change, or uneven temperature distribution on the piping wall.

3.1.7.3 For the clad or lined piping consists of two different materials, the load caused from difference between the parent layer material and the coating layer material in their thermal expansion properties, and the load caused from difference between the internal and external pipes in a jacketed piping in their temperatures.

3.1.8 Fatigue failure caused from pressure cycling load, temperature cycling load, and/or other cyclingly alternating loads upon the piping should be avoided in design.

3.1.9 The displacements of piping racks and connected equipment should be used as design conditions. They include those caused from thermal expansion of equipment or racks, setting of ground, flow of tidewater, wind load and others.

3.1.10 In the case of welding, heat treatment, processing and shaping, bending, and low temperature operation, as well as chilling action generated by suddently pressure reduction of the light volatile fluid, deterioration of tenacity of the material used should be ensured within the allowable limit.

3.1.11 When the working temperature of a fluid is below –191℃, either an external coating layer should be determined or corresponding measures should be taken according to the possibility that air can condense and oxygen can be concentrated in the circumstance in selection of the materials for the pi, ping, including thermo-insulating material.

3.2.1 The pressure-temperature parameter values of a piping component should conform to the following stipulations:

3.2.1.1 Unless otherwise herein stipulated, any current national standard may be used as the design basis of this code, provided that the standard has stipulated the nominal pressure of the piping component and corresponding working pressure-temperature parameter values (or grades). The reference parameter values stipulated in for the standard on the piping component should not be lower the design pressure and design temperature of the piping.

For the components including valves, pipe fittings, and others only required to indicate their nominal pressure values, their allowable stresses at te design temperature may be calculated as the following equation, unless otherwise stipulated:

PA = PN	[σ]t	（3.2.1）
	[σ]x

Where, P_A — The allowable stress at the desihgn temperature (MPa);

PN — The nominal pressure (MPa);

[σ]^t — The allowable stress of the material at the design temperature (MPa);

[σ]_x — The allowable stress of the material at the temperatire that is used to calculate the thickness of the piping component (MPa).

3.2.1.2 For the piping components which pressure-temperature parameter and nominal pressure are not stipulated in any current national standard, the pressure-temperature parameter values of the piping components may be determined by calculation with the allowable stresses of the material at the design temperature and the effective thicknesses of the components (reducing all thickness allowances from the nominal thickness).

3.2.1.3 When two pipings in which two fluids with different pressure-temperature parameters are deliered are connected together, the parameter of the valve isolating the two fluids should be determined as the severer condition, while the piping located at either side of the valve should be designed according to its delivering condition.

3.2.1.4 When more than one piping with different design pressures and design temperatures use identical piping components, their design should be performed according to the pressure and tremperature condition of a piping under severest condition due to coupling of pressure with temperature.

3.2.2  The allowable fluctuating ranges of pressure and temperature of the piping in operation should meet the following stipulations:

3.2.2.1 For the metallic piping in operation, if its pressure, or temperature, or the both non-recurrently fluctuate, and the following stipulations may all be met, this case should be considered to be in the allowable range. Otherwise, the design must be performed according to the severest work condition when pressure and temperature couple in their varying process.

（1）The pressurized component without cast iron and non-ductile metal.

（2）The stress generated by the nominal pressure should not exceed the yield point at the design temperature.

（3）The longitudinal stress should not exceed the limit stipulated in for this code.

（4）Within the service life period of a piping, the total number of pressure-temperature fluctuates out of the design condition should not exceed 1,000.

（5）In no case the highest pressure in variation should exceed the test pressure of the piping.

（6）The non-recurrent variation out of the design condition should meet one of the following limits.

The extent to allow exceed the pressure parameter value or raise the temperature is commensuat with allowing increase of the value of the allowable stress. The stipulations on it are as follows:

It is not allowed that the unremittingly varying time per 24hrs exceeds 1%, and the raise of the allowable stress exceeds 20%;

It is not allowed that the unremittingly varying time per 24hrs exceeds 10%, and the raise of the allowable stress exceeds 15%.

（7） The change, no matter which property, unremittingly or periodic, has no influence on service performances of all components in a system. For example, variation of pressure has no influence on seal property of parts including the valve seat.

（8）The temperature after variation should not be lower than the lowest service temperature stipulated in for Appendix A of this code.

3.2.2.2  For non-metalliclined pipings, their allowable varying values of pressure and tempearture may be used only after their successful application experiences are gotten or they are proved to be reliable.

3.2.3  The allowable stress should meet the following stipulations:

3.2.3.1 The allowable stresses of metallic piping materials in Appendix A of this code refers to allowable tensile stresses, their application should meet the following stipulations:

（1）For the materials of welded piping compinents, a weld joint factor, E_j, should be additionally counted in when the allowable stresses in Appendix A of this code are adopted.

（2）For castings, their quality factor, E_j, which value is 0.8, has been counted in the allowable stresses in Tables A.0.5~0.7 in Appendix A of this code.

3.2.3.2  Allowable shear stresses are 0.8 times of the allowable stresses in Appendix A of this code; The allowable compression stresses on bearing faces are 1.6 times of the allowable stresses; The allowable compression stresses just are the allowable stresses in the table in Appendix A of this code.

3.2.3.3  The bases to determine allowable stresses:

（1）The allowable stresses of bolt materials should be determined as Table 3.2.3-1.

（2）Except bolt and cast iron materials, the allowable stresses of other materials for the purpose of this code should be determined as Table 3.2.3-2.

（3）The allowable stress of grey cast iron at the design temperature should not exceed the lower in the listed below:

1/10 of the lower limit value of standard tensile strength;

1/10 of the tensile strength at the design temperature.

（4）The allowable stress of malleable cast-iron at the design temperature should not exceed the lower in the listed below:

1/5 of the lower limit value of standard tensile strength;

1/5 of the tensile strength at the design temperature.

Allowable stresses of bolt materials           Table 3.2.3-1

Material	Diameter of bolt, d (mm)	Heat treatment	Allowable stress (MPa) The smallest in the listed below
Carbon steel	d≤M22 M24≤d≤M48	Hot rolling, normalization	σ ts/2.7 σ ts/2.5	σ tD/1.5
Low alloy steel, martensite high-alloy steel	d≤M22 M24≤d≤M48 d≥M52	Tempering	σ ts(σt0.2)/3.5 σ ts(σt0.2)/3.0 σ ts(σt0.2)/2.7	σ tD/1.5
Austenic high-alloy steel	d≤M22 M24≤d≤M48	Solution	σ ts(σt0.2)/1.6 σ ts(σt0.2)/1.5

Material	Allowable stress (MPa) The smallest in the listed below
Carbon steel and low alloy steel		sb			ss				σ ts			σ tD		σ tn
		3.0			1.6				1.6			1.5		1.0
High-alloy steel		sb		ss(s0.2)				σ ts(σt0.2)				σ tD		σ tn
		3.0		1.5				1.5				1.5		1.5
Non-ferrous metal		sb		ss(s0.2)				σ ts(σt0.2)				—		—
		4.0		1.5				1.5

 

Note: For Austenic high-alloy steel piping components, the allowable stress may be reasonably heightened to 0.9 times ofσ ts(σ^t_0.2), but should not exceed 0.667 times ofσ_s (σ_0.2) when the design temperature is lower than the creep temperature rang, and tiny residual deformation is allowed. However, this stipulation is not applicable for flanges or other situations where even a tiny residual deformation will cause leakage or failure.

Symbols in this table mean:

σb σS (σ0.2)   σ ts (σt0.2)   σ tD   σ tn

— —   —   —   —

The lower limit value of the standard tensile strength of a material (MPa); The normal yield point of a material at the normal temperature (0.2% of the yield strength) (MPa); The normal yield point of a material at the design temperature (0.2% of the yield strength) (MPa); The aveage value of the creep rupture strengths of a material at the design temperature for 100 thousand hrs in a creep test. The creep limit of a material at a creep rate of 1% at the design temperature for 100 tousand hrs in a creep test.

3.2.4  Quality factors, E_c, of castings should meet the following stipulations:

3.2.4.1  Quality factors, E_c, of castings may be used for the cast components which pressure –temperature parameters are not stipulated in current national standards.

3.2.4.2  The quality factories, E_c, of grey cast iron elements and malleable cast-iron elements meeting the material standard are taken to be 0.8.

3.2.4.3  For other static metal castings, cast steel elements of valves, flanges, pipe fittings, and other components meeting the material standard and passing visual examination, their quality factories, E_c, are taken to be 0.8.

3.2.4.4  In centrifugally casted elements, for those only meeting chemical analysis, tensile strength, hydraulic test, flattening test, and visual examination in the required examinations in the stipulations, their quality factories, E_c, are taken to be 0.80.

3.2.4.5  The values of quality factories, E_c, of castings may be heightened to the values listed in Table 3.2.4 if corresponding supplementary tests are added. However, in no case a quality is allowed to exceed 1.00.

Test method of casting	Ec
(1) Inspection after machining the surface	0.85
(2) Magnetic particle examination or liquid penetration inspection	0.85
(3) Ultrasonic or radiographic inspection	0.95
(1)+(2) above	0.90
(1)+(3) or (2)+(3) above	1.00

3.2.5  The weld joint factor, E_j, should be determined according to the type, and welding method of a weld joint, as well as requirements for examination of the weld joints of table 3.2.5. For 100% nondestructive inspection (NDI) of argon metal-arc welding of non-ferrous metallic pipings, the weld joint factor is 0.85 for a single-welded butt joint, or 0.90 for a double-welded butt joint; while for local nondestructive inspection, the weld joint factor for butt joints is the same as the listed in Table 3.2.5.

Welding method and requirement for examination		Single-welded butt welding	Double-welded butt welding
Electric welding	100% nondestructive inspection	0.90	1.00
	Local nondestructive inspection	0.80	0.85
	No nondestructive inspection requirement	0.60	0.70
Electric resistance furnace welding		0.65（No NDI）; 0.85 (100% eddy current inspection)
Heatin furnace welding		0.60
Automatic spiral welding		0.80~0.85 (No NDI)

Note: So-called non-destructive inspection means examination by using or radiographic ultrasonic inspection.

3.2.6  The calculated stress of a continuous load should meet the following stipulations:

3.2.6.1 The stress caused from internal pressure should be considered safe provided that the thickness and reinforncing calculation of a piping component meets the requirements in this code.

3.2.6.2 The stress caused from external pressure should be considered safe provided that the thickness and stability calculation of a piping component meets the requirements in this code.

3.2.6.3 The sum of longitudinal stresses, σ_L, caused from pressure, gravity, and other continuous loads in a piping should not exceed the allowable stress, [σ] _h, of thematerial at the estimated highest temperature.

3.2.7 The calculated maximum displacement stress range, σ_E, should not exceed the allowable displacement stress range, [σ]_A, determined by the following equation:

Equivalent number of cycles, N	Factor, f
N ≤7,000	1.0
7,000＜ N ≤14,000	0.9
14,000＜ N ≤22,000	0.8
22,000＜ N ≤45,000	0.7
45,000＜ N ≤100,000	0.6
100,000＜ N ≤200,000	0.5
200,000＜ N ≤700,000	0.4
700,000＜ N ≤2,000,000	0.3

(2)  The equivalent numbert of cycles, N, should be calculated as Equation (3.2.7-3):

3.2.7.2  Calculatuion of the allowable displacement stress range should meet the following supplementary stipulations:

（1）For a casting, its allowable stresses, E_c, in cold and hot statuses should be counted into the quality factor of the casting. For a longitudinal weld joint, its allowable stress, [σ]_c and [σ]_h, in cold and hot statuses do require to be multiplied by a weld joint factor, E_j;

（2）The reduction factor of the displacement stress range of the piping, f, is mainly used for the piping with good corrosion resistance. In the case of high number of cycles of main stress, anti-corrosive materials should be used.

3.2.8 The stress caused from an accidental load or a continuous load should meet the following stipulations:

3.2.8.1 In its work condition, the sum of the longitudinal stresses on a piping produced by the internal pressure, deadweight, other continuous, and accident loads should meet the the requirement in the following equation, and 0.75 times of the stress intensification factor, i, in the equation should not be less than 1.

PD2i	+ 0.75 i	MA	+ 0.75 i	MB	≤KT [s]h                                                                   （3.2.8）
Do2 – Di2		W		W

Note: For the steel piping used for the fluid but those in Category A1, the value of K_T may be heightened to 1.33 when the sum of longitudinal stresses caused from wind force, or earthquake exceeds the stipulation in Equation (3.2.8).

3.2.8.2  The stress generated in a test condition is allowed to be out of the limit of Clauses 3.2.6 and 3.2.7 of this code, and may count no other temporary load into.

3.2.8.3  Checking computations are necessary if there is a seismic intensity of magnitude 9 or over.

3.2.8.4  It is not required to take the possibility of simultaneous occurrence of a wind load and an earthquake load into account.

 

 

4.1.1 Selection of the material used for a piping must be based on service condition of the piping, including the design pressure, design temperature, and type of the fluid used, and cost, corrosion resistance, as well as weldability, workability, and other properties of the material.

4.1.2 The specification and performances of the material for a piping should meet the stipulations in current national standards.

4.1.3 Application of the materials that are not listed in this code should meet the stipulations in current national standards on the corresponding materials in chemical composition, physical and mechanical properties, manufacturing process and method, heat treatment, and test, as well as other aspects in this code.

4.2.1 In addition to meeting the stipulation in Appendix A of this code, the service temperature of a material should be determined according to influences on corroson of the fluid intended to use, and on performances of the material.

4.2.2 The upper and lower limits of the material should meet the following stipulations:

4.2.2.1 The service temperature of the material should not be out of the upper and lower temperature limits stipulated in for Appendix A of this code.

4.2.2.2 The material unlisted in Appendix A of this code, determination of its service temperature should meet the following stipulations:

（1）The applicability and reliability of the material under the service temperature condition should be ensured;

（2）The material should have sufficient resistance against influences form the fluid and enternal environment at the service temperature;

（3）The allowable stress of the material should be determined as the stipulated in for Caluse 3.2.3 of this code.

4.3.1 For the carbon steel, low-alloy steel, middle-alloy steel, and high-alloy ferrite steel used for the piping which design temperature is below or equal to -20℃ and higher than the lower limit of the service temperature in Appendix A of this code, their ex-factory materials, weld deposited metals of surface welding, and heat-influence zones should be subject to a low temperature impact test.

4.3.2 For austenic stanless steel with a carbon content over 0.1% used for the piping which design temperature is below or equal to -20℃ and higher than the lower limit of the service temperature in Appendix A of this code, its ex-factory material, weld deposited metal of surface welding, and heat-influence zones should be subject to a low temperature impact test.

4.3.3 Austenic high-alloy steel used in the circumstance equal to or higher than -196℃ may be exempted from the low temperature impact test.

4.3.4 Materials used for pipings, if meet one of the following conditions, may be exempted from the low temperature impact test:

4.3.4.1 When the service temperature is equal to or highetr than -45℃ and not lower than the lower limit of the service temperature of the material in Appendix A of this code, and the test piece of 5mm thick cannot be prepared due to limit of the thickness of the material.

4.3.4.2 When the material, except the rolled steel and bolt materials with a lower limit value of tensile strength over 540MPa, is used under a low temperature and low stress work condition, if the sum of its design temperature plus 50℃is higher than –20℃.

Note: So-called low temperature and low stress work condition means such a work condition that the pressurized piping component which design temperature is lower than or equal to -20℃, and which hoop stress is smaller than or equal to 1/6 of the yield point in the standard on the rolled steel and not larger than 50MPa.

4.3.5 The material required to heat treat should be subject to an impact test after its heat treatment.

4.3.6 The pipe or pipe fitting made of steel sheet under the following condition should additionally be subject to a low temperature impact test.

（1）When the service temperature is lower than 0℃:           20R with athickness over 25mm;

The low-alloy steel with a thickness over 38mm listed in Table A.0.2 in Appendix A of this code.

（2）When the service temperature is lower than -10℃:        20R with a thickness over 12mm;

16MnR, 15MnVR, and 15MnVNR with a thickness over 20mm.

4.3.7 When a non-ferrous metal or its alloy material is used over the lower temperature limit, if the composition of the fillet metal differs from that of the base metal, the weld joint should be subject to a low temperature impact test, and its extensibility should meet the stipulated in for its design.

4.3.8 The material that has accepted the impact test in the manufacturer, if underwent heat treatment after its processing, should be subject to a low temperature impact test.

4.3.9 The low temperature impact test on the heat-influence zone in a welded structure may substitute for the impact test on the matrix material.

4.3.10 The method for an impact test of a material should be in light of the stipulations in the current national standard “Metallic Materials－Charpy Notch Impact Test”, GB/T229. The value of the impact work at the low temperature should meet the stipulations in the standards on cryogenic materials or in Table 4.3.10. When the matrix materials with different impact works are welded together, the energy used for its impact test should meet the requirement for the matrix material with the lower tesile strength.

Material	Lower limit of normal tensile strength of the material, σb (MPa)	Number of test pieces	Impact work, Ak (J)
Carbon steel and low alloy steel	σb≤450	Average value of three test pieces The smallest of them	≥18 12.6
	450＜σb≤515	Average value of three test pieces The smallest of them	≥20 14
	515＜σb≤650	Average value of three test pieces The smallest of them	≥27 18.9
Austenic high alloy steel		Average value of three test pieces The smallest of them	≥31 21.7

Notes: ① The values of impact works in this table are applicable for the standard test pieces. If small test pieces are adopted, these values of impac works listed in this table should be multiplied by the ratio of the actual width of the test pieces to the standard width (10mm).

② The data from the impact tests on carbon steel and low alloy steel are applicable for killed steel.

③ For rolled steel with a tensile strength over 650MPa, its impact work is the same as that of materials with a tensile strength of 650MPa.

4.3.11 All test pieces should be prepared with the material having the same lot number and the same specification, and processed, welded, and heat-treated under the same processing conditions.

4.4.1 The rolled steel used to manafacture piping components shoul meet the following stipulations:

4.4.1.1 Q235-A material is applicable for Categories C and D fluids with a design pressure not larger than 1.6MPa. Q235-A·F material is applicable for Category D fluids with a design pressure not larger than 1.0MPa.

4.4.1.2 When the service temperature of austenic stainless steel is higher than 525℃, the carbon content in it should not be smaller than 0.04%.

4.4.1.3 When pressurized piping components adopt the steel sheets listed in Table A.0.2 in Appendix A of this code, the following steel sheets should be subject to the ultrasonic inspection sheet by sheet:

（1）The low-temperature steel sheet with a thickness over 20mm.

（2）20R and 16MnR sheets with a thickness over 30mm.

（3）Other low alloy steel sheets with a thickness over 25mm.

The steel sheet above should not be below Grade III in quality.

（4）Regardless of its thickness, all hardened and tempered steel sheets should be subject to examination, and they should not be below Grade II in quality.

4.4.1.4 Steel sheets supplied after hardened and tempered should be subject to a normal or low temperature impact test as the design condition.

4.4.1.5 Service type of rolled steel should be determined according to the stipulation in Appendix A of this code. Any supplied status designated in the design document, if differes from the stipulated in for the current national standard, should be indicated in the design document.

4.4.1.6 The rolled steel used for low-temperature pipings should adopt killed steel.

4.4.2 The service range of cast iron materials should meet the following stipulations:

4.4.2.1 When spheroidal graphite cast iron is adopted to manufacture a pressurized component, its design temperature should not exceed 350℃, design pressure should not exceed 2.5MPa. In the normal temperature, it is inadvisable that the design pressure exceeds 4.0MPa.

4.4.2.2 It is not allowable that the service temperature of austenic spheroidal graphite cast iron is below -196℃.

4.4.2.3 It is inadvisable to use the following cast irons under the severe cyclic condition. In the case that necessary measures to prevent from overheat, mechanical virbration, and misoperation are taken, they may be confined to use in the following ranges:

（1）It is inadvisable to use grey cast iron to manufavture the piping for a Category B fluid delivery. When such doing is inevitable in a special circumstance, its design temperature should not be higher than 150℃, design pressure should not exceed 1.0MPa; It is inadvisable similarly that the design pressure exceeds 1.6MPa, the design temperature exceeds 230℃ for the greay cast iron element in the piping for a Category C fluid delivery;

（2）For the malleable cast-iron used in the piping for a Category C fluid delivery, its design temperature should not be higher than 230℃, design pressure should not be higher than 2.5MPa; or its design pressure should not be higher than 2.0MPa if a design temperature of 300℃ is adopted; when used in the piping for a Category B fluid delivery, its design temperature should not be higher than 150℃, design pressure should not be higher than 2.5MPa;

（3）It is prohibited to use high silicon cast iron for a Category B fluid delivery.

4.4.3 Application of other metallic materials should meet the following stipulations:

4.4.3.1 It is unadvisable to use cupper, aluminium materials in a fire hazard potential zone.

4.4.3.2 It is prohibited to use lead, stannum and/or their alloy pipings for Category B fluid delivery.

4.4.3.3 When cupper, or aluminium is connected to other metallic materials, the possibility to generate electrochemical corrosion should be taken into account if there is an electrolyte.

4.4.4 Application of clad metals and lined materials should meet the following stipulations:

4.4.4.1 When a piping component is made of an integrally clad steel sheet meeting the requirement in the standard on the material, its parent (outer layer) and coating metals should meet the stipulations in Clause 4.1 of this code.

（1）The compression strength of a piping made of an integrally cald material may be calculated according to the total thickness of the parent and the coating metals after all thickness allowances are deducted.

（2）The allowable stresses of the parent metal and the coating metal may be in ligjht of the stipulated in for Appendix A of this code. But the allowable stress value of the coating metal should not larger than that of the parent metal.

The allowable stress of the integrally clad material may be calculated as Equation (4.4.4):

[σ]0 =	[σ]1δ1 + [σ]2δ2	（4.4.4）
	δ1 +δ2

where, [σ]₀ ­— The allowable stress of an integrally clad metallic material at the design temperature（MPa）;

[σ]₁ — The allowable stress of the parent metal at the design temperature（MPa）;

[σ]₂ — The allowable stress of the coating metal at the design temperature（MPa）;

δ₁ — The nominal thickness of the parent metal (mm);

δ₂ — The effective thickness of the coating metal after deducing the allowance (mm).

4.4.4.2 For the non-integrally constructed cald metal or lined piping component, the thickness of its parent metallic material should be in line with the thickness from its compression strength calculation, and the calculated thickness should include neither thickness of the coating nor of the liner.

4.4.4.3 In addition to the requirement in this clause, various limitations on piping materials for different fluid delivery in this code are not applicable for the clad materials or lined materials for piping components. Clad or lined materials, and parent materials, as well as adhesive used should be selected according to the design condition and properties of the fluid.

4.4.4.4 In the case of the cald layer made of austenic stainless steel, is inadvisable that its service temperature exceeds 400℃.

4.4.4.5 The service temperature of non-metallicliner materials may be as the stipulated in for Appendix C of this code.

4.4.5 The connection joints, and auciliary materials, such as daub, solvent, soldering materials, filler, gasket and O-ring, lubricant and sealant for screw thread, and others selected to construct or for a sealed joint should have good compatibility with the above-said materials and the fluid deliveried.

 

 

5.1.1 Piping components should meet the stipulation on pressure resistence design in this code, in addition to the stipulations in current national standards concerned.

5.1.2 The requirement for molding and postwelding heat treatment of piping components should meet the stipulation in Appen, dix G of this code.

5.1.3 Examination of piping components should meet the stipulation in Appendix J of this code.

5.1.4 Materials used for piping components should meet the stipulations on material standards in Section 4 and Appendix A of this code.

5.2.1 Straight welded steel pipes, if are aopted, should meet the stipulations in Appendix J and Table 3.2.5 in the text of this code.

5.2.2 It is advisable that pipings in severe operation condition adopt seamless steel pipes, as well as cupper, aluminium, titanium, and nickel seamless pipes. If the straight electrcally welded steel pipes are adopted, they should meet the stipulation in Clause 5.2.1 in this section.

5.2.3 The extra strong pipe in the current national standards “Welded steel pipe for low pressure service”, GB / T3092, and “Welded steel pipe for low pressure liquid delivery”, GB / T3091, may be used to deliver Category C fluids with a design pressure of 1.6MPa or below and a design temperature between 0 ~ 200℃. Pipes with normal thickness are only used for Category D  fluids.

5.2.4 If seamless steel pipes are used in the case of a design pressure of 10MPa or over, their manufacture and examination should meet the stipulations in the current national standard “Seamless steel tubes and pipes for high pressure boiler”, GB5310, the requirement for examination of stailess steel pipes should not be inferior to the stipulation in the current national standard “Stainless steel seamless pipes for fluid transport”, GB/T14 976.

5.2.5 The minimum thickness of steel pipes should meet the stipulation in Appendix D of this code.

5.2.6 It is advisable that the inner pipe of a jacketed pipe adopts the seamless pipe.

5.2.7 The pipe for Oxygen delivery should meet the related safety stipulation in this code.

5.3.1 Application of a circular arc bend should meet the following stipulations:

5.3.1.1 For a bend after manufactured and bended as curremnt national standards, the thickness at its outside attenuated position should not be smaller than the sum of the calculated thickness of a straight pipe and the corrosion allowance.

5.3.1.2 No corrugated bend is allowed to use in any piping.

5.3.1.3 The roundness of the section of a steel pipe after bended should met the following stipulations:

(1)   When bearing an internal pressure, the difference between the maximum outer diameter and the minimum outer diameter should not exceed 8% of the nominal outer diameter;

(2)   When bearing an external pressure, the difference between the maximum outer diameter and the minimum outer diameter should not exceed 3% of the nominal outer diameter

5.3.2 Adoption of a miter bend should meet the following stipulations:

5.3.2.1 A miter bend which strength calculation, manufacture and weld all are performed as the stipulated in for this code may be used in the same operation condition as that for the straight pipe that is used to manufacturing it. However, it is unadvisable that the design pressure of the miter bend exceeds 2.5MPa.

5.3.2.2 A miter bend, if the angle,α, of direction change of one of its welding lines is larger than 45°, only may be used for Category D fluid delivery, but is not allowed to use for delivering fluids in other categories.

5.3.2.3 When a miter bend is adopted in the piping that will is used under a severe cyclic condition, the angle of direction change of one of its welding lines should not be larger than 22.5°.

5.3.2.4 For the inner pipe of a jacketed piping, the circular arc elbow or bend but the miter bent should be adopted.

5.4.1 The pipe fittings used under a severe operation condition should meet the following conditions:

5.4.1.1 Adopting forged elements and rolled seamless pipe fittings;

5.4.1.2 For a rolled welded element, its weld joint factor should be larger than or equal to 0.9;

5.4.1.3 For a cast steel elements, its casting quality factor E_c should not be smaller than 0.90, and should meet the stipulation in Clause 3.2.4 of this code;

5.4.1.4 The thickmess of a stainless steel butt weld pipe fitting should meet the stipulation in Caluse D.0.1 of Appendix D.

5.4.2 Selection of common pipe fittings and non-standard reducers should meet the following stipulations:

5.4.2.1 So-called common pipe fittings include the standard pipe fittings manufactured in plants, such as elbow, tee-joints, double tees, reducers, and caps.

5.4.2.2 When selecting the circular arc bend with butt ends, the bent with a long radius (the curvature radius is 1.5 times of the nominal diameter) should be adopted. The bend with a short radius only may be used to meet some particular need in a special arrangement.

5.4.2.3 When the pipe fitting that is hot-press molded and assembly-welded (assembled by welding both halves) from steel sheets is adopted, the stipulation in Clause J.1.1 in Appendix J of this code should be followed.

5.4.2.4 In the case of no special requirement, it is advisable to adopt preferentially steel pipe fittings. It is advisable to used approved malleable cast-iron pipe fittings with threaded ends in the ground pipings for Category D fluid delivery.

5.4.2.5 The outer diameter series and end nominal thicknesses of standard pipe fittings with butt weld ends should be designated in the engineering design document. The internal thickness of a pipe fitting should be determined according to the design pressure, design temperature, and corrosion allowance condition by the manufacturer. A pipe fitting is allowed to thicken inside locally, however, the thickness at no position is allowed to be smaller than the thickness at either end.

5.4.2.6 For the non-standard reducer made by roll-welding steel sheet, its design pressure should be calculated as this code, but a design pressure over 2.5MPa is considered unadvisable.

5.4.3 Selection of the prefabricated flange spools should meet the following stipulations:

5.4.3.1 The requirement in this clause is only applicable for separately manufactured flange spools, neither for special pipe fittings nor for the end-integrally-forged flange.

5.4.3.2 The flange spools processed by welding, if meet the following conditions, may be applicable for the same operation condition as other pipes connected with it.

(1)   The outer diameter of the flanges must meet the dimension requirement for the flange spools in the flange standards concerned or the standard on flange designated in the design document.

(2)   The thickness of a flange should not be smaller than the nominal thickness of the pipe connected with it.

(3)   It is advisable that a flange spool adopts the same material as that of the pipe.

(4)   They should be processed as the requirement for the flange spool (see Figure 5.4.3) processed by welding.

 

 

Figure 5.4.3  The flange spool processed by welding

Note: The flange part should be mechned, and roughness of the sealing face should meet the requirement in the flange standard concerned after welded. Examination of the welding line should meet the stipulation in Clause J.1 of Appendix J.

5.4.3.3 The integrally flared and cupring flange spools, if meet the following conditions, may be used in the same operation condition as the pipe connecting with it.

（1） The outer diameter of the flanges must meet the dimension requirement for the flange spools in the related flange standards or the standard on flange designated in the design document.

（2） The fillet radius of the cupring should adapt matching with the corresponding flange.

（3） The thickness of the flange measured at any point should not smaller than the ratio of the product of 95% of the minimum pipe wall thickness with the outer radius of the pipe to the radius at the cupring thickness measuring point.

5.4.3.4 The flange spool under the severe cyclic operation condition.

（1） The flange spool (see Figure 5.4.3) processed by welding used under the severe cyclic operation condition should be processed as the type of (d) or (e) in the figure, and should meet the requirement in Clause 5.4.3.2.

（2） The integrally flared cupring flange spool is prohibited to use under the severe cyclic condition.

5.4.4  Selection of welded braches and prefabricated brach connectors should meet the following stipulations:

5.4.4.1  The following branch connectors may be adopted according to the requirement in this clause in addition to the tees and double tees in Clause 5.4.2 of this section.

（1）Welded braches, see Figures 5.4.4-1(a), (b), (c) and (d);

（2）Half couplings, see Figure 5.4.4-2;

（3）Weldolet, see Figure 5.4.4-3;

（4）Insert type branch, see Figure 5.4.4-1(e).

(a) wleded branch                                               (b)  wleded branch

 

(c) wleded branch with                          (d) wleded branch with                      (e) insert type branch

reinforcing plate                      reinforcing plate

Figure 5.4.4-1 Types of branch connector welding lines

Notes: ① T_tn.— The nominal thickness of the main pipe (mm); t_tn—The nominal thickness of the branch (mm); t_c—The calculated effective thickness of the fillet weld, may take to be 0.7 t_tn or 6.5mm, whichever is larger; t_r— The nominal thickness of the reinforcing plate (mm).

② The dimension values shown is the acceptable minimum welding line dimension.

③ When adopting the connecting types in Figures 5.4.4-1(c) and (d), aф5 air-bleed hole

should be opened at a high position of the reinforcing plate; the reinforcing plate should be jointed with both the main pipe and the branch. When adopting the connecting types in Figures 5.4.4-1(a) and (c), the deviation between the inner diameter of the main pipe and the diametr of the hole opened on the main pipe should not be larger than 3mm.

 

Figure 5.4.4-2  Half couplins

 

 

 (a) thredolet                                                                 (b) sockolet

 

(c) buttolet

Figure 5.4.4-3  Weldolet

5.4.4.2  The branch connector should meet the requirement for the structure of the welding line type (Figure 5.4.4-1) for the branch connector. Reinforcement should meet the stipulation in this code. If there a severe cyclic operation condition, the structure of (b), (d), or (e) in Figur es 5.4.4-1 should be adopted.

5.4.4.3  If a main branch on a piping with a design pressure over 6.3 MPa is a reducing one, then it is unadvisable to adopt an in-situ manufactured welded branch; in this case it is a better solution to adopt a tee, or drill a hole on the main piping and weld a weldolet onto it. It is advisable to adopt a tee if the main branch is isodiametric.

5.4.4.4  It is unadvisable that the nominal diameter of a half couling is larger than 50 mm when it is adopted as a branch connector.

5.4.4.5  For the piping in a virbration circumstamce, tees, weldolets, or inser type branches may be adopted, but no welded branch is allowed to adopt.

5.4.4.6  When the ratio of the outer diameter of the main piping to the thickness, [D₀/(T_tn-C_1n)], is larger than or equal to 100, the outer diameter of the branch should be smaller than 1/2 of the outer diameter of the main piping.

5.5.1 The type, and structure of the valves used for varioud categories of fluids, and materials used for their parts should be selected according to characteristics of the fluid used, design temperature, design pressure, and the stipulation in Clause 3.2.1 of this code.

5.5.2 When a hand valve is adopted, it is advisable to adopt a gear operating mechanism if the opening force of the valve is larger than 400N.

5.5.3 The valve with less than 4 bolts for connection between the bonnet and the body should only be used in the piping for Category D fluid delivery. No bonnet connected by screw thread is allowed to use in the steam piping with a nominal pressure over 1.6MPa.

5.5.4 For the valves used for high temperature or low temperature fluids, it is advisable to adopt a bonnet-extended structure type improving the service condition of packings.

5.5.5 The spherical valve with a fire-proof (or fire-retardant) structure should be adopted in the case that a spherical valve with a soft seals is required to use in the piping for Category B fluid delivery.

5.5.6 Materials for valves should meet the stipulation in Chaper 4 of this code. Valve seats and valve cores should adopt anti-abrasive materials if they are used for strong abrasive fluids. Gate valves should be those with an open spindle structure if they are used for abrasive fluids.

5.5.7 Except the requirement in anti-abrasive characteristics, it is advisable to adopt the valves with steel bodies in the piping for Category B fluids.

5.5.8 For the small valve that is connected by welding its ends, if the valve seat may deform during its welding and heat treatment process, A valve with a long body, or spools at its ends should be adopted.

5.5.9 The fast valve should not be used in the piping for oxygen delivery. The gaskets and packings in the valve should not be made of any material being debris and/or fiber falling-off prone, or of any combustible material.

5.6.1 Determination of the nominal pressure of a standard flange should meet the stipulation in Clause 3.2.1.1 of this code.

5.6.2 When a non-standard flange is adopted, it must be subject to a compression strength calculation as the stipulation in this code.

5.6.3 The piping under any of the following conditions should adopt the welding neck flange, but the slip on (boss) flange is not allowed to use.

5.6.3.1 The piping that is anticipated to be under a frequently and cyclic large amplitude vibration condition;

5.6.3.2 The piping being under a severe cyclic condition.

5.6.4 It is advisable to set the jacking screw on the flange when there is a requirement to set the blind flange on a piping which rigidity is so large that disassembly and assembly are inconvenient, or which nominal diameter is larger than or equal to 400mm.

5.6.5 For the flange with non-metallic gaskets, it is advisable that the roughness of its seal face is taken to be 3.2~6.4μm. The flange with spiralwound gaskets should have a smooth seal face which rouighness preferably is 1.6~3.2μm, and adopt a nominal pressure larger than or equal to 2.0MPa.

5.6.6 When a metallic flange is connected to a non-metallic flange, or the flange made of hard brittle material is adopted, both the flanges all should be the full face (FF) ones. When the raised face (RF) flange must be adopted, the measure to prevent the flange from demage caused from overload of the bolts should be taken.

5.6.7 In the case of frequently and large amplitude temperature cycle it is unadvisable to use the socket-welding flange and the screwed flange at a temperature over 260℃ or below – 45℃.

5.7.1 Selection of gaskets should adapt the required sealing load to the design pressure and the seal face of the flange, the strength of the flange and its bolt connection, and the material of the gasket should adapt the property of the fluid and the operation condition.

5.7.2 It is advisable that the spiralwound gasket is equipped with an inner guide ring for using on a male and female flange, or with an outer guide ring for using on a raised face (RF) flange.

5.7.3 The gasket used in the full face flange should be a full face non-metallic one.

5.7.4 For a non-metallic gasket, its outer diameters may be larger than the outer diameter of the seal face of the raisd face (RF) flange, and is made into a “self-centering” one.

5.7.5 For the non-metallic gasket used for the stainless steel flange, its chlorine ion content is not allowed to exceed 50×10^-6.

5.8.1 Fasteners used in pipings include hexagon headed bolts, bolt studs, nuts, gaskets, and the like.

5.8.2 Standard fasteners should be selected from those listed in current national standards and the materials used for them should be selected from the materials stipulated in for Appendix A of this code.

5.8.3 The material used for the fastener to connect flanges should meet the stipulations in current national standards on flanges and adapt the type of gasket used.

5.8.4 It is unadvisable that the screw-pitch of the thread section of a fastener used to connect flanges is larger than 3mm. The fastener with a diameter over M30 may adopt fine thread.

5.8.5 The Carbon steel fastener should meet the service temperature stipulated in for current national standards on flanges.

5.8.6 The fastener used for different flanges should meet the following stipulations:

5.8.6.1 If there is a flange made of cast iron, brone, or another cast flange in a pair of flanges connected each to other, then the material used for the fastener on the strength-lower flange should be used. However, the material used for the fastener may be selected in light of any flange in the case of the following condition.

（1）Both the flanges all are FF, and adopt full face gaskets;

（2）Taking factors in continuous load, displacement strain, temporary load, strength of the flange, and other aspects into account, the sequency and the torsional moment to tight bolts has been stipulated.

5.8.6.2 When two flanges that respectively fall into different grades are bolted together, the torsional moment to tight bolts should meet the requirement for the flange at a lower grade.

5.8.7 Under a severe cyclic condition, the bolts or studs to connect the flanges shoul be made of an alloy steel material.

5.8.8 When threaded holes are made on a metallic piping component to screw studs directly, these threaded holes should have an efficient depth, which at least should be equal to the diameter of the nominal thread if the components are made of steel, or should not be smaller than 1.5 times of the diameter of the nominal thread if the components are made of cast iron.

5.9.1 Selection of the weld joint should meet the following stipulations:

5.9.1.1 The groove of a wedl joint should meet the stipulations in the current national standards “ Basic forms and sizes of weld grooves for gas welding, manual arc welding and gas-shielded arc welding”, GB/T985, and “Basic forms and sizes of weld grooves for submerged arc welding”，GB/T986.

5.9.1.2 Selection of the socket welded joints:

（1）It is unadvisable that their nomnal diameters are larger than 50mm. The connection structures should meet the stipulation in Clause H.1 in Appendix H of this code.

（2）They are prohibited to use in the fluids work condition with crevice corrosion.

（3）The joints with a pipe diameter over DN40 are not allowed to use under the severe cyclic condition.

5.9.1.3 Selection of the butt-welded joints:

（1）Except for there is a disassembling demand for repair in a steel piping, the butt-welded joint should be adopted.

（2）When the piping components with an identical material strength and different thicknesses are coupled by butt-welding, and the internal wall or external wall at the the thicker end forms a unfitness of butt joint over 2mm or is out of the value stipulated in the design document, the stipulation in Clause H.2 in Appendix H of this code should be met.

5.9.1.4 Welding of the slip on (boss) flange should meet the stipulation in Clause H.1.4 in Appendix H of this code.

5.9.2 Selection of the threaded connection joints should meet the following stipulations:

5.9.2.1 They are prohibited to use under the fluids work condition with crevice corrosion.

5.9.2.2 No sealing material is allowed to use in the threaded connection joints required seal welding.

5.9.2.3 They should not be used in the piping with a large torsional moment or vibration. Preventive measures should be taken in the case that the thread may be loosed due to thermal expansion.

5.9.2.4 Under a severe cyclic condition, threaded connection is confined to use only for thermowells (connection with thermometric elements).

5.9.2.5 The structure connected by a straight thread coupling or taper thread is only used for the piping delivering Category D fluids.

5.9.2.6 Except the both thicknesses including common thickness and extra strong in the standard on steel pipes said in Clause 5.2.3 of this code, the minimum thickness of steel pipes and pipe fittings with male thread should meet the stipulation in Clause D.0.2 in Appendix D of this code.

5.9.2.7 When the pipings for Category B fluid delivery are connected by taper thread, their nominal diameters should not be larger than 20mm, and should adopt seal welding.

5.9.2.8 For the joint sealed by taper thread, it is unadvisable that its design temperature is larger than 200℃; When it is used in the piping delivering Category C fluids, its design pressure should not be larger than 4MPa for a nominal diameter between 32 ~ 50mm, 8Mpa for a nominal diameter of 25mm, or 10MPa for a nominal diameter below or equal to 20mm. Seal welding should adopted for a design pressure over the above-said values.

5.9.3 Application of other types of connection joints should meet the following stipulations:

5.9.3.1 The cement-filled cast iron pipe bell and spigot joint is confined to use only for Category D fluids. The piping should be equipped with reasonal supports to prevent the joint from loosing.

5.9.3.2 No soldered joint is allowed to use under a severe cyclic condition and in the piping for Category B fluid delivery.

5.9.3.3 No bonded joint is allowed to use in the pressurized metallic piping.

5.9.3.4 Except the pipe end sealed with the sight glass purpose seal gasket, the pipe end that is used as a seal face to impact into the gasket by protruding out of the threaded flange face (Figure 5.9.3-1) is confined to use only in the piping for Category D fluid delivery.

5.9.3.5 When a straight threaded joint sealed by means of a gasket on the end face but a thread (Figure 5.9.3-2) is welded with the main pipe together, deformation of the seal face should be prevented. The structure shown in Figure 5.9.3-2(a) is not allowed to use for Category B fluids.

 

Figure 5.9.3-1  The structure in which a pipe end is used as the seal face

by protruding out of the threaded flange face

 

(a) The seal face of the gasket may deform

(b) The seal face of the gasket may not deform

(c) The seal face of the gasket may not deform

Figure 5.9.3-2  Typical straight threaded joints

5.10.1 The compensator with the packing seal should not be used in the piping for Catergory B fluid delivery.

5.10.2 Neither corrugated expansion joint nor flexible metal hose is allowed to use if there is possibility to be twisted.

5.10.3 When a corrugated expansion joint is intended to use, it should be reasonably selected according to performances of corrugated expansion joints of different types. Its service life and counterforce should be calculated in design. If there is cold spring, it should be indicated in the design document. Besides, it should be taken into account that problems brought by condensation and icing of the fluid when the environmental temperature lowers.

5.10.4 The temporary filter may be set in the inlet piping only when safe guarding work of the rotary equipment is carried out on-stream.

5.10.5 The permanent filter should be set in the piping such as the inlet of a steam trap, shower nozzle, or ejector, and the pump inlet related to a solution preparing system.

5.10.6 The size of the screen mesh of a filter should be determined according to the process requirement.

5.11.1 Selection of the piping component with the non-metallic liner should meet the stipulation in Clause 4.4.4 of this code.

5.11.2 It is advisable to adopt a metallic flanged connection in the end connection structure of a piping component with non-metallic liner. Except the refractory material liner, all liners should be extended to cover the entire flange seal face, and should be securely and flat bonded with the base metal.

5.11.3 The requirements for selection of the base metal parts of all piping components should meet the stipulations in Clauses 5.2 through 5.6 and 5.9 of this section.

5.11.4 There should be preventive measures for application of a non-refractory material used in a fire hazard potential zone.

5.11.5 Specially manufactured backing rings may be used to adjust the installtion length of a piping with the non-metallic liner.

 

6．CALCULATION OF PRESSURE-RESISTANCE

STRENGTH OF METALLIC PIPING COMPONENTS

 

6.1.1 calculation methods listed in this section is suitable for design and calculation of pipe components which are necessary in engineering project design. For pipe components that have been clearly specified with nominal pressure, calculation is not necessary to be done per this section.

6.1.2 Requirement of pressure resistance of standard butt weld pipe components shall be in accordance with 5.4.2.5 of 5.4.2 in this code.

6.1.3 For the calculated thickness of pressure-resistance strength (hereinafter simplified as calculated thickness), the designed thickness is the sum of calculated thickness and the additional thickness; and the nominal thickness refers to the thickness based on calculated thickness plus an additional amount, and then with which a round sum that matches the standard size of the material in use for that component is taken. The effective thickness is the difference from the nominal thickness minus the additional amount. The minimum thickness is the sum of calculated thickness plus the additional amount for corrosion or abrasion.

 

6.2.1 Calculation of straight pipe that bears internal pressure shall meet the following stipulations:

6.2.1.1 When calculated thickness ts is smaller than 1/6 of the external diameter of the pipe, the calculated thickness of the straight pipe shall not be the value calculated by formula (6.2.1-1). The designed thickness shall be calculated as per formula (6.2.1-2):

ts =	PDo	（6.2.1-1）
	2（[s]t Ej +PY）

                                                t_sd = t_s + C                                                                                                                                            （6.2.1-2）

                                                C = C₁ + C₂                                                                                                                                                                                        （6.2.1-3）

When coefficient Y is to be decided, it shall meet the following stipulations.

When t_s< D_o/6, it shall be selected from table 6.2.1;

When ts>or = Do/6,  Y =	Di + 2C	（6.2.1-4）
	Di + Do +2C

Where:  t_s——calculated thickness of straight pipe (mm);

        P——designed pressure (MPa)

        D_o—— external diameter of pipe (mm);

        D_i——internal diameter of pipe (mm);

       [σ]^t——permitted stress to use for material at designed temperature (Mpa);

        E_j——weld joint coefficient;

        t_sd——designed thickness of straight pipe (mm);

        C——sum of additional amount for thickness

        C₁——an additional amount for thickness reduction, including reduction from

              fabrication, groove making, and depth of thread as well minus tolerance of

              materials (mm);

        C₂—— an additional amount for material corrosion or abrasion (mm);

         Y—— coefficient.

                       Value of coefficient Y          table 6.2.1

Material	Temperature (℃)
	≤482	510	538	566	593	≥621
ferrite steel	0.4	0.5	0.7	0.7	0.7	0.7
austenitic steel	0.4	0.4	0.4	0.4	0.5	0.7
Other tough metals	0.4	0.4	0.4	0.4	0.4	0.4

Note：①The temperature value that locates between the intermediate temperatures listed in the

        table may be got by means of inter-plotting.

②For cast iron, Y = 0.

6.2.1.2  When thickness of the calculated straight pipe t_s is bigger than or equal to 1/6 of the external diameter of the pipe D_o, or when the ratio (P/[s]^tE_j) between the designed pressure P and the product found from multiplication of permitted stress at designed temperature [σ]^t and the weld joint coefficient E_j is bigger than 0.385, calculation of the straight pipe shall be performed specially considering factors such as the cracking theory, fatigue and heat stress.

Thickness requirement of reinforcing, of straight pipe which is subjected to external pressure shall be conform to current National Standard GB150 “Steel Pressure Vessel”.

 

6.3.1  Pressure resistance calculation for miter bends (figure 6.3.1) which subjected to internal pressure shall be in accordance with the following stipulations:

6.3.1.1  This section suitable for strength calculation of miter bends which is formed by a pipe section, of which the change of direction has an angle αbigger than 3 degrees. When the miter bend’s angle is smaller than 3 degrees, strength calculation is allowed to be omitted.

 

(a)    miter bend which has thickness same to that of straight pipe

(b) weld structure at both ends of the miter bend, of which the thickness id bigger than that of straight pipe.

Figure 6.3.1  miter bend

 

6.3.1.2   Permitted internal pressure P_m of a miter bend that has more than one weld seams shall be taken from formula 6.3.1-1 or 6.3.1-2, whichever is smaller.

	（6.3.1-1）
	（6.3.1-2）

t_se = t_sn – C                                                                                                                                   （6.3.1-3）

Where:  q——1/2(°) of the changing angle a of one of the weld seams of a miter bend.

        r_o——average diameter of pipes (mm);

        R₁——bending radius (mm);

        P_m——Maximum permitted strength of miter bend (MPa);

        t_se——effective thickness for straight pipe (mm);

        t_sn——nominal thickness of straight pipe (mm)

6.3.1.3  Calculation of maximum permitted internal pressure of single joint seam miter bend shall meet the following stipulations:

（1）For single joint seam miter bend with angle θsmaller than or equal to 22.5 degrees, calculation of maximum permitted internal pressure P_m shall be performed per formula:   (6.3.1.1).

（2）For single joint seam miter bend with angle θbigger than 22.5 degrees, calculation of maximum permitted internal pressure P_m shall be performed per formula (6.3.1-4)

（6.3.1-4）

6.3.1.4 Curvature radius of miter bend R1 shall be in accordance with stipulations in formula （6.3.1.5）

（6.3.1-5）

In this formula, K₂, being a value coming from experience, is to be determined with the effective thickness of the straight pipe and should tally with stipulations in table 6.3.1.

             Experimental value K2 used for miter bend (mm)     table 6.3.1

tse	K2
tse≤12.5	25
12.5< tse<22	2 tse
tse≥22	[2 tse/3]+30

It is suitable that the frequently used curvature radius R₁ locates between 1.0 time and 1.5 times of the nominal diameter DN, which is not suitable to be less than 300 mm.

6.3.1.5  Weld seam at the end of the miter bend as shown in figure 6.3.1 is necessary only when

its thickness being bigger than that of the straight pipe connected to it, or when an item that was prefabricated in a workshop is adopted. The value calculated out from formula (6.3.1-6) or formula (6.3.1-7), whichever is bigger, shall be adopted as length L_f for the shorter side of the end of the miter bend.

                        L_f = 2.5（r_ot_se）^0.5                                                                                                                                                        （6.3.1-6）

                        L_f = tgq（R₁ – r_o）                                                                                                                                           （6.3.1-7）

Where:  L_f ——length of the shorter side of the end of miter bend.

6.3.1.6  The calculated result of the maximum permitted internal pressure P_m of the miter bend must be bigger than or equal to the designed pressure P_o. If this is not the case, weld seams should be increased and calculate again. When there is some special requirement, it can be treated by increasing thick, ness of the miter bend.

6.3.2  For miter bend that is subjected to external pressure, its thickness may be determined according to the method treating a straight pipe as is specified in 6.2.2 of this code.

6.4.1  Calculation of reinforcement of weld branch pipe shall be in accordance with the following stipulations:

6.4.1.1  The structural type ( see figure 6.4.1) is that the axis of branch pipe crosses the axis of

main pipe resulting an angle of α1 being used within 45 ~ 90 degrees, as is shown in the figure. When the main pipe is of a seam welded one, the weld seam should be located below the main pipe inclining against the main pipe.

 

Figure 6.4.1  reinforcement for branch connections

6.4.1.2 Calculation for reinforcement of hole in the main pipe

（1）Area A, needed for reinforcement of the main pipe hole, shall be determined per the following formula (6.4.1-1):

                        A = T_t d₁（2 – sina₁）                                                                                                                                     （6.4.1-1）

                        d₁ = d / sina₁                                                                                                                                                                （6.4.1-2）

                        d = d_o – 2 t_m + 2（C_1t + C₂）                                                                                                               （6.4.1-3）

（2）Calculation for effective range of reinforcement of hole cutting

B =	2d1	（6.4.1-4）
	d1 + 2（Ttn + ttn）– 2（C1m + C1t + 2C2）

The bigger amount between the above two results shall be taken.

h1 =	2.5（Ttn – C1m – C2）	（6.4.1-5）
	2.5（ttn– C1t – C2）+ tr

The smaller amount between the above two results shall be taken

Where:  T_t —— calculated thickness of main pipe (mm);

        A —— reinforce area needed for weakening from hole cutting of the main pipe (mm);

        a₁ —— included angle between axis of main pipe and axis of branch pipe (degree);

        d_o —— nominal external diameter of branch pipe (mm);

        d₁ —— the longer diameter of the inclining hole of the main pipe after the additional

               thickness is deducted (mm);

        d—— internal diameter of branch pipe after the additional thickness is deducted (mm);

        C_1t—— an additional amount for thickness reduction of the branch pipe (minus

deviation) (mm);

        C_1m —— an additional amount for thickness reduction of the main pipe (minus

               deviation） (mm);

        C₂ ——an additional amount for corrosion or abrasion (mm);

        t_r —— nominal thickness of the reinforcement plate (mm);

        B —— effective width of reinforcing plate (mm);

        T_tn —— nominal thickness of main pipe (mm);

        t_tn—— nominal thickness of branch pipe (mm);

        h₁—— effective height at the normal direction from outside the main pipe (mm).

（3） Each reinforcing area is to be calculated according to the following formulae; rib plate, if any, shall not be included in the reinforcement calculation.

                        A₁ =（B – d₁）（T_tn – T_t – C_1m – C₂）                                                                                                   (6.4.1-6)

                        A₂ = 2h₁（t_tn – t_t – C_1t – C₂）/ sina₁                                                                                                     (6.4.1-7)

A₃ shall be calculated according to the practical cross section area of the angular weld seam.

                        A₄ =（D_r – d_o / sina₁）（t_r – C_1r）f_r                                                                                                       (6.4.1-8)

                        f_r = [σ]^t_RP / [σ]^t_M                                                                                                                                                        (6.4.1-9)

When [σ]^t_RP≥ [σ]^t_M, f_r = 1.

（4）The result of calculation of reinforcing area shall be in accordance with the following stipulations:

A₁ + A₂ + A₃ + A₄ ≥A                                                                                      （6.4.1-10）

 Where:    A₁ —— surplus metal area (mm²) from the main pipe after bearing internal and

                   external pressures within the range of reinforcement in addition to the

                   necessary calculated thickness and thickness additional amount;

           A₂ —— surplus metal area (mm²) from the branch pipe after bearing internal and

                   external pressures within the range of reinforcement in addition to the

                   necessary calculated thickness and thickness additional amount;

           A₃ —— angular weld seam area (mm²) with reinforcement zone;

           A₄ —— area ( mm² ) of other reinforcing items in addition to that within the

                   reinforcing zone;

           t _t —— calculated thickness of branch pipe ( mm );

           C_1r —— an additional amount for thickness reduction of reinforcing plate ( minus

                   deviation ) (mm );

           D_r —— external diameter of reinforcing plate (mm );

           f_r —— ratio between permitted stress of reinforcing material and that of main

                  pipe material;

         [σ]^t_RP—— permitted stress of reinforcing material at designed temperature (MPa);

         [σ]^t_M—— permitted stress of main pipe material at designed temperature (MPa);

6.4.2  Reinforcement for main pipe when there are more than one branch pipe shall be in       accordance with the following stipulations;

6.4.2.1 When the distance between centers of more than two adjacent cut holes in the main pipe is less than two times of the average diameter of the two adjacent holes and the reinforcing zone is overlapped (see figure 6.4.2 ), reinforcement of the two or more than two cut holes shall be calculated per 6.4.1 of this code and reinforced in combination.

 

Figure 6.4.2   reinforcement for multi-cut holes

6.4.2.2  When combined reinforcement is adopted, the total area of reinforcement shall not be less than the sum of the reinforcement areas of each individual reinforced holes. The reinforced area between two adjacent holes must be equal to at least 50% of the sum of the total areas of each hole necessary for reinforcement; more, distance between the two centers of holes shall be at least equal to 1.5 times of the average diameter of the two cut holes.

6.4.2.3  When reinforcing area is being calculated, no cross section area is allowed to be included repeatedly.

6.4.3  Reinforcement for a branch pipe that is drawn out by means of extruding and pressuring

shall be in accordance with the following stipulations:

6.4.3.1  The extruded branch pipe, including the curvature radius, shall be formed directly from the main pipe by means of pressuring and extruding using one or some pressuring mold.

6.4.3.2  Axis of branch pipe must cross axis of main pipe perpendicularly. Height h_x of the branch pipe that has been extruded from the main pipe, and that is over the main pipe surface, shall be equal to or bigger than the curvature radius r_x, which is located within the flat surface constructed by the axis of the main pipe and axis of the branch pipe.

6.4.3.3  Within the plane constructed by main pipe and branch pipe, the curvature radius at the turning of outside contour has relation to the nominal external diameter do of branch pipe, and shall be in accordance with the following stipulations:

（1）Minimum value of r_x：take r_x as 0.05 do, or 38mm, whichever is less.

（2）Maximum value of r_x：When d_o < DN200, r_x shall not be more than 32mm;

                       When d_o ≥ DN200, r_x shall not be more than 0.1d_o + 13mm.

（3）When the outside contour consists of several radiuses, the above requirements of (1) and (2) is suitable for a maximum radius, which is a radius with the best match of a transitional connection with a 45 degree round corner.

6.4.3.4  This article does not suit various pipe ports that uses other reinforcing parts such as reinforcing ring, cushion plate or saddle plate.

6.4.3.5  Calculation of reinforcement shall be in accordance with figure 6.4.3 and the following stipulations:

（1）effective range of reinforcement.

（6.4.3-1）

Where:  B —— effective width of reinforcing zone (mm);

        h₂ —— effective height of branch pipe (mm);

        d_o —— nominal external diameter of branch pipe (mm);

        t_x —— effective height of extruded branch pipe at the external surface of the main

pipe after additional thickness amount is deducted (mm);

        d_x —— internal diameter of extruded branch pipe after additional thickness amount

               is deducted (mm ).

 

Figure 6.4.3  type of extruded branch pipe

Note: This drawing shown the symbols adopted in clause 6.4.3, however, this does not mean that it is a detailed drawing, neither is it a perfect structural scheme to be adopted.

(2) Area A that needs to be reinforced.

                        A = K₃ (T_t) (d_x )                                                                                                (6.4.3.2)

Where: K₃ —— reinforcing coefficient of extruded branch pipe;

When d_o / D_o > 0.6, K₃ = 1.0

When 0.15 < d_o / D_o ≤ 0.6, K₃ = 0.6 +2（d_o / D_o）/ 3

When d_o / D_o ≤ 0.15, K₃ = 0.7

(3) reinforcement area, which can be made use of.

                        A₁ =（B – d_x）（T_tn – T_t – C_1m – C₂）                                                                                      （6.4.3-3）

                        A₂ = 2h₂（t_tn – t_t – C_1t – C₂）                                                                                                               （6.4.3-4）

                        A₅ = 2r_x（t_x + C_1t + C₂ – t_tn）                                                                                                               （6.4.3-5）

Where:  A₁ —— surplus metal area (mm²) besides both of calculated thickness needed for

internal and external pressure and additional thickness amount which is within the reinforcement zone and born by the main pipe.

        A₂—— surplus metal area (mm²) besides both of calculated thickness needed for

internal and external pressure and additional thickness amount which is within the reinforcement zone and born by the branch pipe.

        A₅ ——surplus metal area (mm²) besides both of calculated thickness needed for

internal and external pressure and additional thickness amount which is within the reinforcement zone and born by the extruded branch pipe.

        r_x——      curvature radius at the round corner of outside contour, which is located

               within the plane constructed by the axes of main pipe and branch pipe(mm).

（4）calculated result of reinforcing area shall meet the stipulations of the following formula:

                                   A₁ + A₂ + A₅ ≥ A                                                             （6.4.3-6）

6.4.4  When distance between centers of any two adjacent holes of several extruded branch pipe is less than two times of the average diameter of the two adjacent holes, stipulations for reinforcement will be the same to that of 6.4.2 in this code.

6.4.5  Requirement for reinforcement of other connecting part(s) of the branch pipe shall meet

the following stipulations:

6.4.5.1 When semicanal joint is more than or equal to nominal diameter 50 mm and 1/4 of nominal diameter of the main pipe, meanwhile, when designed pressure is less than or equal to 10 Mpa, and thickness at the smallest part of the joint end is more than or equal to thickness t shown in table 6.4.5-1 and meets the pattern in figure 5.4.4-2, calculation for reinforcement can be exempted.

                         

DN	Thickness t, minimum
15	4.1
20	4.3
25	5.0
32	5.3
40	5.5
50	6.0

6.4.5.2  When branch pipe joint preparation is to be selected among butt welding, screw connection or socket ( spigot ) welding (see Figure 5.4.4-3 ), reinforcement shall be performed entirely according to pressure – temperature parameter condition. Thickness at the end of branch pipe joint of butt-welding shall be equal to the thickness of the branch pipe.

6.4.5.3  Under the circumstances that the designed temperature is lower than or equal to 400℃ and designed pressure is lower than or equal to 7.1 MPa, socket (spigot) branch pipe joint may be used ( see Figure 6.4.5 ). When the nominal diameter is less than or equal to 50 mm and t_w meets table 6.4.5-2, calculation for reinforcement may be exempted.

Figure 6.4.5  socket (spigot) branch joint

               Size of socket (spigot) branch pipe joint t_w（mm）    table 6.4.5-2

Nominal diameter DN	Size tw minimum
15	4.8
20	5.6
25	6.4
40	7.1
50	8.7

6.5.1 Design of non-standard reducer without folded edge (figure 6.5.1) shall be in accordance with the following stipulations:

6.5.1.1 Reducer without folded edge can be fabricated by means of rolling steel plate and then welding. Welding seam of eccentric reducer is better to be located at the position shown in figure 6.5.1（b）.

 

（a）concentric     （b）eccentric    （c）reducer that has reinforced sections at both ends

Figure 6.5.1  reducer without folded edge

6.5.1.2 Designed pressure of reducer without folded edge shall meet stipulations in 5.4.2.6 of 5.4.2 of this code.

6.5.1.3 For concentric reducer, the included angle b between the hypotenuse and the axis shall be better not bigger than 15 degrees. For eccentric reducer, the included angle b between the hypotenuse and the axis shall be better not bigger than 30 degrees.

6.5.2 Thickness of reducer that is subjected to internal pressure and without folded edge shall be in accordance with the following stipulations:

6.5.2.1 Calculation of thickness at each part of the reducer shall be performed in accordance with  included angle b between designated hypotenuse and axis by means of the following three formulae, and then select the biggest one.

tLC =	PDOL	（6.5.2-1）
	2（[s]tEj +PY）cosb

 

tLL =	QLPDiL	或tLL =	QLPDOL	（6.5.2-2）
	2[s]tEj – P		2[s]tEj +（2QL – 1）P

 

tLS =	QSPDiS	或tLS =	QSPDOS	（6.5.2-3）
	2[s]tEj – P		2[s]tEj +（2QS – 1）P

 

Where:  t_LC —— calculating thickness at the tapered part of reducer (mm)

        t_LL—— calculated thickness of bigger end of reducer (mm);

        t_LS —— calculated thickness of smaller end of reducer (mm);

        P —— designed pressure (Mpa);

        D_OL—— external diameter of bigger end of reducer (mm);

        D_OS —— external diameter of smaller end of reducer (mm);

        b —— included angle between hypotenuse and axis of reducer (°);

        D_iL —— internal diameter of bigger end of reducer (mm);

        D_iS —— internal diameter of smaller end of reducer (mm);

        Q_L—— stress increasing coefficient for connection of the bigger end of reducer to

               straight pipe (see figure 6.5.2-1);

        Q_S ——stress increasing coefficient for connection of the smaller end of reducer to

               straight pipe (see Figure 6.5.2-2)

 

 

Figure 6.5.2-1  Q_L value at joint between the bigger end of reducer and cylinder

 

Note：The curve lines were plotted according to maximal stress intensity（main being axial bending stress），the controlled value being 3[s]^t.

 

Figure 6.5.2-2  Q_S value at joint between the smaller end of reducer to cylinder

Note: The curve lines were plotted based on the fact that each side from the joint has a film stress intensity being within the range of 0.25 √0.5D_iSt_LS (which is resulted from calculation based on average circular tensile stress and average radial pressing stress), the controlled value being 1.1[σ]^t.

6.5.2.2  Selection of reducer thickness:

（1）When the maximum value of thickness being calculated is less than or equal to the effective thickness t_se of the straight pipe that is connected to the bigger end, nominal thickness of reducer may be taken as per the same nominal thickness of the straight pipe.

（2）When the calculated maximum thickness value is bigger than the effective thickness t_se of the straight pipe that connects the bigger end of reducer, it should be dealt with as follows:

If arrangement of piping allows to reduce the included angle b between the hypotenuse and the axis, recalculate;

If the included angle b between the hypotenuse and axis is impossible to change, the maximum calculated thickness listed in 6.5.2.1, meanwhile, the structure shown in figure 6.5.1(c) of 6.5.1 shall be adopted. This reducer shall have a straight pipe with reinforced sections at both ends connected to it.

（3）Nominal thickness t_L of the reducer shall be the sum of calculated thickness, thickness additional amount C and the round figure value of material thickness.

6.5.2.3 Length of the reinforced straight pipe shall be decided according to the following:

	（6.5.2-4）
	（6.5.2-5）

Where:  L_SL—— length of reinforced straight pipe which is connected to the big end of the

                reducer (mm);

        L_SS—— length of reinforced straight pipe which is connected to the small end of the

                Reducer（mm）.

6.5.3 The requirement of thickness and reinforcement of the reducer which is subjected to external pressure shall be in accordance with the current National Standard GB150: “<Steel Pressure Vessel>”.

 

6.6.1 Thickness of flat cover without welding seam shall be calculated according to formula       6.6.1-1 and formula 6.6.1-2.

                        t_p = K₁（D_i + 2C）[ P /（[s]^t h）]^0.5                                                                                                   （6.6.1-1）

                        t_pd = t_p + C                                                                                                                                                                    （6.6.1-2）

Where:   t_pd —— designed thickness of the flat cover(mm);

         t_p —— calculated thickness of the flat cover(mm);

         D_i —— internal diameter of the pipe (mm);

       K₁, h—— a coefficient related to the structure of the flat cover to be selected from table

                6.6.1;

         P —— designed pressure (MPa);

        [σ]^t —— permitted stress (MPa) for the material under designed temperature;

         C —— sum of added thickness (mm)

                         Type coefficient of flat cover structures                   table 6.6.1

Type of flat cover	Requirement of structure	Coefficient K1	Coefficient h		note
			h3>2tsn	2tsn> h3>tsn
	h3≥tsn V-welding seam	0.4	1.05	1.00	①

Type of flat cover	Requirement of structure	Coefficient K1	Coefficient h		note
			h3>2tsn	2tsn> h3>tsn
	V-welding seam plus angular welding ditto	0.6	0.85		①②
		0.4	1.05		①③
	V-welding seam plus angular welding ditto	0.6	0.85		①④

 

Note:    ①        Groove size shall be in accordance with 5.9.1.1 of 5.9.1 of this code.

②   Used for piping whose nominal pressure is lower than 2.5 MPa and nominal diameter less than 400mm.

③   Only used for hydraulic test, when the nominal diameter is less than or equal to 400mm.

④   Used for piping whose nominal pressure is lower than 2.5 MPa and nominal diameter less than 40 mm.

6.6.2  When a hole is to be drilled in the center of the flat cover, calculation for reinforcement shall be performed in accordance with the current National Standard GB150 “ Steel Pressure Vessel”.

 

6.7.1  Non-standard flange with specific requirement may be designed in accordance with the current National Standard GB150 “Steel Pressure Vessel”.

6.7.2  Calculated thickness of a blind flange sandwiched between two flanges (figure 6.7.2) may be determined according to formula 6.7.2-1. When this plate is made with a whole piece of steel plate, the welding joint coefficient E_j ia equal to 1. For a permanent blind flange, an additional thickness shall be added to in accordance with formula 6.7.2-2.

t_m = 0.433d_G [P/（[s]^t·Ej）]^0.5                                                                                                              （6.7.2-1）

t_pd = t_m + 2C₂ + C₁                                                      （6.7.2-2）

Where:  t_m —— calculated thickness of the blind flange (mm);

        d_G —— inter, nal diameter of concave gasket or gasket of flat flange, or the average

               diameter of ring-grooved gasket (mm);

        P —— designed pressure (Mpa);

        [σ]^t —— permitted stress for material at designed temperature (Mpa);

        E_j —— coefficient of weld joint;

       t_pd —— designed thickness of blind flange (mm);

        C₂ —— additional thickness for corrosion or abrasion (mm);

        C₁ —— additional amount for thickness reduce (mm).

 

 

 

 

Figure 6.7.2  blind flange sandwiched between two flanges

 

 

 

7.1.1 diameter of pipe shall be determined according to the flow rate, characteristics, and flow speed and permitted pressure of the pipe.

7.1.2 Determination for diameter of pipe made of alloy steel and with big diameter shall be done by compression for construction cost and operation cost.

7.1.3 Except for those stipulated otherwise, pipe nominate diameter less than 25 mm shall not be used for liquid which is likely choke the pipe.

7.1.4 Except for those specially required, pipe diameter can be decided per the following methods:

7.1.4.1 Set the average flow velocity, and calculate the internal diameter initially per the following formula, then readjust it according to engineering designing specification, in which pipe size series is designated, to get the actual internal diameter. Finally, recheck actual average flow velocity.

                        D_i = 0.0188 [W_o / nr]^0.5                                                                                                                                                                                   （7.1.4）

Where:   D_i —— internal diameter of the pipe (m);

         W_o —— matter flow rate (kg/h);

         n —— average flow speed (m/s);

         r —— density of fluid (kg/m³).

7.1.4.2 Pressure loss of piping shall be calculated and checked by means of actual internal diameter of the pipe D_i and the average flow speed so as to confirm the feasibility of the chosen pipe diameter. If the pressure loss does not satisfy, a recalculation shall be performed.

7.1.5 Selection of the average flow speed of piping shall be in accordance with the following stipulations:

7.1.5.1 Average flow speed shall be selected according to the characteristics and condition of the fluid as well as the permitted pressure loss of the piping.

7.1.5.2 Flow speed in the emptying pipe which locate behind the valve shall not be higher than the sound speed calculated according to the following formula:

                                    n_c = 91.20（KT / M）^0.5                                                                                                                      （7.1.5-1）

k =	Cp	（7.1.5-2）
	Cv

Where: n_c —— sound speed or critical flow speed of gas （m/s）；

       k —— index of heat-isolation of gas

C_p, C_v—— heat capacity under fixed pressure, heat capacity under fixed capacity

[J/ (g·K)];

       T —— gas temperature（K）；

       M—— gas molecular weight.

 

7.2.1 The content of this section is only suitable for calculating the piping pressure loss of fluid of Newton Pattern, including pressure loss due to friction inside straight pipe and partial (local) pressure loss due to friction such as in valves and piping components, excluding calculation for acceleration loss and static pressure loss, etc.

7.2.2  Calculation for friction loss of piping for liquid shall meet the following stipulations:

7.2.2.1  Piping friction pressure loss of liquid shall be calculated according to formula (7.2.2-1)

DPf =10-5	lrn2	·	L	（7.2.2-1）
	2g		Di

where:  DP_f —— friction pressure loss of straight pipe (Mpa);

        L —— piping length (m );

        g —— gravity acceleration (m / s²);

        D_i —— pipe internal diameter (m );

        n —— average flow velocity ( m / s);

        r —— fluid density (kg / m³)

        l —— friction coefficient of fluid.

7.2.2.2     Equivalent length approach or resistance coefficient approach can be used to calculate

local friction loss.

（1）Equivalent length approach:

DPk =10-5	lrn2	·	Le	（7.2.2-2）
	2g		Di

（2）Resistance coefficient approach:

DPk =10-5·KR	rn 2	（7.2.2-3）
	2g

  Where:  DP_k —— local pressure loss due to friction（MPa）；

          L_e —— equivalent length of valve and piping components (m)；

          K_R —— resistance coefficient.

7.2.2.3     Total pressure loss in piping for liquid is the sum of friction loss of straight pipe and

local pressure loss due to friction, and shall be added with a suitable margin, of the factor is better to be taken between 1.05~1.15.

          DP_t = C_h（DP_f +DP_k）                                                           (7.2.2-4)

   Where:  DP_t —— total pressure loss in piping (Mpa);

           C_h —— margin factor of piping pressure loss.

7.2.3  Calculation of pressure loss in piping containing gas shall meet the following stipulations:

7.2.3.1  When the total pressure loss is less than 10% of the initial pressure, formula 7.2.2 in this code can be used to calculate pressure loss due to friction.

7.2.3.2  When the total pressure loss is within 10% ~ 20%, formula 7.2.2 is still valid, but the average density shall be based on.

7.2.3.3  For some system, of which the total pressure loss is larger than 20%, the piping should be divided into several sections and then calculate individually, then sum up. Each section of piping is also calculated with formula 7.2.2 of this code.

 

7.3.1  In the mixture of gas and liquid, when gas phase volume (gas content per volume) is within the range of 6% ~ 98%, it will be better to calculate pressure loss by means of dual-phase flow approach.

7.3.2  When pressure loss in piping is calculated for piping in which the flow contains gas and liquid phases, first set the pipe diameter and judge out the flow pattern. If it is a column type flow or a piston type flow, the pipe diameter should be reduced so as to turn it into a circumferential flow or dispersed flow.

7.3.3  Calculation for pressure loss of gas-liquid dual-phase flow in piping shall be performed according to an approach that has been proved practical. The total pressure loss (calculate value) shall be multiplied by a tolerate coefficient 0f 1.3 ~ 3.0.

7.3.4  If the gas-liquid dual-phase is of a flashing pattern, there will be a deviation of calculated pressure loss due to change of gas-content when the matter flows through the piping. Such deviation has to be analyzed. When the above-mentioned gas-content in matter changes with more than 5%, calculation can be performed per individual sections; the method of such calculation is the same to that used in non-flashing pattern multi-phase flow piping.

 

 

 

I.   General stipulations

8.1.1 Layout of piping shall meet requirement of processing, piping and instrument flow chart.

8.1.2 Layout of piping shall meet requirement of production operation, installation and maintenance. It is suitable to lay the piping overhead with planning and arrangement in neat order. In areas of workshop or processing unit where maintenance is not convenient, piping used for transmitting media which are strong corrosive or category B fluid is not suitable to lay underground.

8.1.3 Piping that tends to expand from heating and contract from cooling shall be laid with flexibility calculation, for which the flexibility range shall not be smaller than that stipulated in this code and stipulations for engineering designing.

8.1.4 Piping layout should be made according to the controlled vibration of piping required by the clause 3.1.5 in this code.

 

II.                  Net overhead height and net distance between pipes

8.1.5 When overhead piping crosses road, railway and sidewalks, the net overhead height refers to the height of the lowest height of piping insulation layer or supporting members. Net overhead height shall meet the following stipulations:

  (1) for electric railway, beyond track surface                        ≥6.6m

  (2) over rail track surface                                       ≥5.5m 

  (3) for road           (recommended)    ≥5.0m       (minimum) 4.5m

(4) under bottom surface of horizontal beam of piping supporting        ≥4.0m

   frame in production unit

(5) bottom layer piping under another piping path and over man path     ≥3.2m

(6) man path beside road                                        ≥2.2m

(7) man path in production unit zone                               ≥2.0m

(8) Crossing net distance between piping and electric power line shall

   be laid in accordance with present National Standard.

8.1.6 When piping is to be laid on overhead supporting frame in open area, the horizontal distance between frame edge and buildings or other facilities shall meet current National Standard “Fire Fighting Procedure for Petrochemical Enterprises” (GB50160), “Design Procedure For Overall Plane Of Industrial Enterprise” (GB50187) and Fire “Fighting Procedure in Civil Construction Design” (GBJ16)

   Horizontal distance between piping supporting frame edge and the following facilities:

   (1) to outside of railway                              ≥3.0m

   (2) to edge of road                                        ≥1.0m

   (3) to edge of side walk                                ≥0.5m

   (4) to center of plant zone fencing wall                    ≥1.0m

   (5) to outside wall of buildings with doors and windows      ≥3.0m

   (6) to outside wall of buildings without doors and windows             ≥1.5m

8.1.7  When piping is laying out, path for operational personnel and for maintenance shall be reasonably planned. Path for operational personnel shall not be narrower than 0.8 m.

8.1.8 For laying two parallel pipes, net distance from any extruded position to extruded part or outside surface of insulation cover shall not be less than 25mm. For bare pipes, net distance from wall to wall shall not be less than 50mm. Insulation cover shall not be touched one another after bit shift due to heat (cooling).

 

III  General requirement for layout

8.1.9 Space between layers of multi-layer installed piping shall meet piping installation requirement. Piping loaded with corrosive liquid shall be laid in the bottom layer of the rack. Piping subjected to high temperature shall not be arranged at lower position where its heat influences electric cables.

8.1.10  Piping that goes along ground surface, when it has to cross man path, a cross overpass shall be equipped.

8.1.11  Valve, flange, screw joint, and buffer with packing materials shall not be located in the

section of the pipe that goes over road and railway.

8.1.12  Piping going along wall shall not affect opening and closing doors and windows.

8.1.13  Piping loaded with corrosive liquid shall not be laid over equipment in revolving operation.

8.1.14  Piping of pump shall meet the following requirement:

8.1.14.1  Arrangement of pump inlet pipe shall give the pump a net positive suck pressure (cavitation erosion margin)

8.1.14.2  Inlet pipe of dual-sucking centrifugal pump shall try to avoid drift due to unsuitable pipe fitting.

8.1.14.3  Horizontal eccentric reducer at inlet of centrifugal pump is usually arranged top flat, however, under the circumstance that the reducer is directly connected to an upward elbow, a bottom flat arrangement can be adopted. The reducer shall be installed as close to the pump inlet as possible.

8.1.15  Layout of piping that connects vessels shall meet the following stipulations:

8.1.15.1  Orientation of pipe port of non-standard type equipment shall be arranged considering the internal structure and requirement of processing.

8.1.15.2  When pipe port elevation and position of the first supporting frame is being considered,  the piping shall be able to endure sink of the vessel foundation.

8.1.15.3 Fixed and movable supporting base of horizontal vessel and heat exchanger shall be specified clearly according to requirement of piping layout, the fixed supporting base shall benefit calculating flexibility of the piping.

8.1.16  When laying out piping, space shall be reserved for maintenance, operation, loading and unloading packing materials of revolving equipment as well as for fire engine to pass.

8.1.17  Pipe shall not be arranged in lifting openings, neither in the area where internal parts are to be drawn out or where flange is to be disconnected.

8.1.18  Setting of interface of instrument shall meet the following stipulations:

8.1.18.1  Position of interface of local indication instrument shall be set at an elevation from where the operator can see clearly.

8.1.18.2  Instrument interface shall be set according to requirement of instrumentation profession and satisfy the space necessary for fitting and unfitting instrument elements.

8.1.18.3  For steam piping, of which the designed pressure not higher than 6.3 MPa or designed temperature not higher than 425℃, the nominal diameter of instrument interface shall not be larger than 15mm. Piping that is more serious than above or is subjected to vibration, not less than 20mm. When the main pipe has a nominal diameter less than 20mm; if nominal diameter of main pipe is less than 20mm, the instrument interface shall not be less than that of the main pipe.

8.1.19  Structure of piping shall meet the following stipulations:

8.1.19.1  Space between two butt welding seams shall not be less than three times of thickness of the member to be welded. If post heat treatment is need, the space shall not be less than six tine of thickness of the member to be welded. Furthermore, it shall meet the following requirements:

For Piping whose nominal diameter is less than 50mm, space between weld seams shall not  be less than 50mm; for those have nominal diameter more than or equal to 50mm, the space shall not be less than 100mm.

8.1.19.2  Circumferential weld seam shall be better not to locate within the scope of piping supporter. For weld seams that needs to be heat treated, the net distance from outside of the seam to supporter frame edge shall be better for five times of the weld seam width, however shall not be less than 100mm.

8.1.19.3  It is unsuitable to cut holes and connect branch pipes on pipe weld seam. If inevitable, it must be checked for strength.

8.1.19.4  When a pipe is being bent at site, bending radius shall not be less than 3.5 times of external diameter of the pipe; the initial point of bending shall be away from weld seam by 100mm, however not be less than external diameter of the pipe.

8.1.19.5  For piping connected with screw threads, each section shall be equipped with a movable union swivel adjacent to elements such as valve, etc. However, union swivel may be omitted if connection is done by flanges.

8.1.19.6  With exception of butt-welded pipe elements that has a straight section at end, standard butt-welded pipe shall not be connected directly to sliding sleeved flanges.

8.1.20  Supporting frames of steam piping or piping loaded with condensable gas shall be better to connect over the main pipe. Branch pipe for steam condensate shall be connected in from over the main recovery pipe.

8.1.21  When piping is laying out, temporary openings for commissioning, construction, surging shall be preserved.

8.1.22  Jacketing pipes shall be equipped when pipe goes through safety isolating wall. Pipe section inside the jacket shall not have weld seam. Space between the pipe and jacket shall be fully packed with soft non-combustible materials.

 

IV.  Requirement for layout of category B fluid piping

8.1.23  Category B fluid piping is not allowed to install in such workshop, over indoor roof, or sandwiched layers in buildings where ventilation is poor.

8.1.24  Outdoor category B gas piping that is loaded with gas whose density is higher than that of outdoor atmosphere and has piping components such as flange, screw connection or packing structure shall not laid out closely near buildings with doors and windows. It may be treated in accordance with 8.1.6 in this code.

8.1.25  Category B fluid piping is not allowed to go through buildings that has nothing to do with it.

8.1.26  Category B fluid piping shall not be laid out adjacent to both sides of high temperature piping, neither over high temperature piping where heat influence exists.

8.1.27  When category B fluid piping is laid out adjacent to cables for power or instrument, the parallel net space shall not less than 1m. When cable is laid out beneath, net cross-space shall not be less than 0.5m. When piping adopts welding joint and no valves, the net parallel space may be halved. (50%).

8.1.28  Discharge of Category B liquid shall meet requirement of sections concerned in this code. Water containing oil shall be first drained into an oil-water separator.

8.1.29  The net parallel space between category B fluid and oxygen piping shall not be less than 500mm, crossing net space not less than 250mm. When piping adopts welding joint and no valves, the net parallel space may be halved.(50%).

V.  Layout of valves

8.1.30  Whether the valve is to be installed horizontally, vertically or with the valve stem upward depends on the structure, principle, correct flow direction of the valve, as well as requirement of the manufacturer.

8.1.31  Position of all safety valves, pressure reducing valves and regulating valves shall be such that they are convenient to adjust and maintenance, and space for drawing out the valve core shall be preserved. Platform shall be equipped for valves installed high overhead. All manually operated valves shall be positioned within an elevation that is easy to access,

8.1.32  Valves shall be arranged in an area where shift due to heat is as small as possible.

8.1.33  When a nozzle, which needs to fit with valve, is located on removable cover of equipment, removable pipe section shall be provided and a stop valve shall be arranged at the outside of end cover disassemble area.

8.1.34  Such as heat exchanger, a pipe section that is possible to dismantle shall be provided, while the shut valve shall be located at outside of dismantle area of the cover.

8.1.35  When piping of safety valve is arranged, the counter reaction force and its direction shall be considered. Position of it shall be such that supporting frame for outlet pipe is easy to design. The connecting pipe of the valve shall have sufficient strength against moment.

VI. Setting of discharging gas at high point and discharging liquid at low point

8.1.36  Ports for discharging gas and liquid shall be provided at high point and low point respectively and these points shall be easy to access. If there (at same elevation) is other interface that can be made use of, individual discharging point may be defaulted. With exception of piping on the piping rack, for piping whose nominal diameter is less than 25mm, discharging port may be defaulted, and at low position where steam-traced pipe winds along discharging port can be defaulted too.

8.1.37  Minimal nominal diameter of gas discharging pipe at high point shall be 15mm; for liquid discharging pipe at low point, 20mm. Equal diameter pipe may be used when nominal diameter of the main pipe is 15mm.

8.1.38  Valve is not necessary for gas discharging port of gas pipe, of which the opening shall be covered with blind flange or pipe cap.

8.1.39  All lowest points of liquid discharging ports shall be at least 150mm away from ground surface or platform surface.

8.1.40  Liquid collecting drum or steam trap sets shall be provided at low point of piping that is loaded with saturated steam.

 

VII.  Position of vents

8.1.41  Distance between vent pipe outlet and as well as safety valve release vent of category B gas and platform or building shall meet existing National Standard “Procedure for designing fire-fighting in Petrochemical enterprises” (GB50160) article 4.4.9.

8.1.42  For position of emptying port, in addition to the above requirement, the existing National Standard “technical approach for designating local standard for discharging atmospheric pollution matter” (GB/T3840) shall also be observed.

 

8.2.1  Piping in ditch shall meet the following stipulations:

8.2.1.1     Layout of piping shall be convenient for maintenance and replacing piping components.

For assuring safety run, water-discharging measures shall be available in ditch. In areas where has high underground water level and high potential of water accumulation in ditch while no reliable water prevention measures to be taken, piping arranged in ditch is unsuitable.

8.2.1.2  Distance between ditch and railway, road, and building shall be determined based on conditions of building structure, road foundation and piping layout depth, pipe diameter fluid pressure and piping well stricture. And meet stipulations stipulated in annex F.

8.2.1.3  Layout of ditch in parallel under the main pass way should be avoided.

8.2.1.4  Articles in 8.1 of this code for arrangement of piping, structure. ventilating gas and discharging water also suit for piping in ditches.

8.2.2  Piping layout in going-through ditch shall meet the following stipulations:

8.2.2.2  Net width of path in ditch shall not be less than 0.7m, net height not less than 1.8m.

8.2.2.3  Safety entrance shall be provided for long ditches, manholes and vertical ladders shall be equipped with space of 100m between each two ones, handholes for installation shall be provided if necessary.

8.2.3  Layout of piping in not-going-through ditches shall meet the following stipulations:

8.2.3.1  When valves that is to be operated rather frequently are arranged in the ditch, the valve should be located at the place which does not affect human to pass by. If necessary, elongated valve stem may be devised so as to raise the stem wheel up to the height over the movable ditch cover.

8.2.3.2  Category B fluid piping is not to be arranged in sealed ditches. Category B gas (with density higher than ambient atmosphere is not suitable to be set in open ditches. If inevitable, the ditches shall be filled full with fine sand and use of piping should be inspected periodically.

 

8.3.1  Minimum distance between buried piping and railway, road and building shall meet the stipulations in table F, annex F of this code.

8.3.2  The minimum horizontal distance between piping and piping, piping and cable shall meet the stipulations in existing National Standard “Design Procedure For Overall Plane Of Industrial Enterprise” (GB50187).

8.3.3  When piping with large diameter is to be buried deep, requirement of stability and rigidity under soil pressure shall be satisfied.

8.3.4  Piping going across from underground road, shall at least 0.7 m below road surface.

8.3.5  Jacket pipe should be provided for piping that goes across under railway; the space from the jacket pipe top surface to bottom rail surface shall not be less than 1.2m.

8.3.6  Net space between a cable and a piping going across it shall not be less than 0.5m. The cable in better to be laid under the piping that emits heat, or beyond the piping that is loaded with corrosive medium in.

8.3.7  Net across space from category B fluid piping, piping loaded with oxygen, and heat dynamic piping to other piping shall not be less than 0.25m; for category C and D piping, such space shall not be less than 0.15m.

8.3.8  Piping shall be buried into a depth below the freezing level. If it is impractical, reliable freezing prevention measures shall be taken.

8.3.9  When there are buffers, valves and other piping components that need maintenance, they should be arranged in wells, cabinets in conformity with safety requirement, where at least a space of 0.5m wide for maintenance is provided.

8.3.10  Piping with heating line ( heat tracing pipe, for example) shall not be buried directly, but arranged in ditch instead.

8.3.11  Requirement for earth excavation and piping laying out shall be in conformity with “Design Procedure For Overall Plane Of Industrial Enterprise” (GB50187).

8.3.12  When laying piping with heat isolation layer and piping  with external protective jacket,  sufficient flexibility and a margin for heat expansion of the internal pipe within the outside pipe shall be given. Approach for compensation-free direct burying may be used for category D fluid piping that runs under temperature less than or equal to 120℃, for which design and construction work shall be in accordance with existing National Standard.

 

OF METALLIC PIPING

 

9.1.1  Reaction force and moment from piping against machines that connect the piping shall meet the permitted reaction force and moment put forward by the manufacturer of equipment. In case the specified value is surpassed but possible be solved by discussing, a written permission issued by the manufacturer is needed. Reaction force and moment from piping against the port of pressure vessel shall functions as a mandatory condition in checking the vessel’s strength.

9.1.2  When calculation of flexibility proves that the piping has strong cycling condition, it should be checked with this code for selection of piping components. If the result does not satisfy the requirement, the design should be revised to lower down position-shift stress scope so as to turn the strong cycling condition into a non-strong cycling condition.

 

9.2.1  Application scope of calculation for flexibility shall meet the following stipulations:

9.2.1.1  Scope of calculation for flexibility includes piping whose designed temperature being lower than or equal to –50℃, or higher than or equal to 100℃.

9.2.1.2  The scope of nominal diameter in calculation of for flexibility shall be determined in accordance with designed temperature and circumstance of piping layout when engineering design is being performed.

9.2.1.3  Piping not included in the condition described in 9.2.1.1 and meets one of the following conditions shall be listed in the scope of calculation for flexibility:

（1）Long piping without heat insulation being affected by outdoor ambient temperature;

（2）Piping with additional position shift at ends and its flexibility is not able to be judged by experience.

（3）When a small branch pipe is to be connected to a big branch pipe and the big one has position shift which affects judgement of flexibility. In this case the small branch pipe shall be calculated together with the big one as well.

9.2.1.4  Analysis for flexibility can be exempted if piping is with one of the following conditions:

（1）The piping is completely identical with some piping that runs perfectly well;

（2）The piping has been compared with one that had been analyzed for flexibility proving almost no change.

9.2.2  Approach for flexibility analysis shall meet the following stipulations:

9.2.2.1  Piping that is connected to important sensitive machine or equipment, or runs under high pressure, temperature, or its cycle number equivalence is as large as up to 7000, and is required for serious engineering design conditions should be computed for flexibility by means of computer program.

9.2.2.2  Verification with approach of table listing, diagrams can be used for simple L type, II type and Z type piping. However the table listed and diagram shall have been verified to be valid.

9.2.2.3  When a local part of piping without branch pipe or piping system is used as initial

judgement before flexibility is computed by computer, a simplified analysis may be used.

 

9.3.1  Division of calculation for piping system shall meet the following stipulations:

9.3.1.1  Piping system may be divided into several subsystems according to connection points of equipment or fixed points. Each subsystem shall include all its piping components and various supporting frames and hangers.

9.3.1.2  To calculate a crotch piping division by division from crotch, which is usually unsuitable, is only practical when rigidity of the crotch branch pipe is extremely different from that of the main pipe (i.e., the small pipe has little diversion on the big pipe and can be neglected ) However, in this case, precise line shift and angle shift, which is added by the main pipe upon the port of branch pipe, shall be included when the branch is being calculated.

9.3.2  Calculation of flexibility shall meet the following stipulations:

9.3.2.1  When piping is connected to equipment, the additional position shift at piping ends, including line shift and angle shift, shall be involved in.

9.3.2.2  When piping components being calculated, flexibility coefficient and stress increasing coefficient shall be involved in according to annex E of this code.

9.3.2.3  Function of various supporting frames and hangers shall be involved in calculation;

9.3.2.4  Various work conditions may appear in piping operation. Such conditions shall be calculated respectively.

9.3.2.5  Any hypothesis and simplification during calculation shall not affect the calculation result with unfavorable or unsafe factors.

9.3.2.6  When supporting frames and hangers root onto equipment that has position shift, such heat position shift value shall be included in calculation.

 

9.4.1  When moment at various points of piping is being calculated, a total compensation value from installation temperature to maximum temperature shall be adopted, and the coefficient of linear expansion listed is table B0.2 in this code and the Young’s modulus of the piping at installation temperature listed in table B0.1 in this code can be used.

9.4.2  Calculation for equivalence composition moment of each point shall meet the following stipulations:

9.4.2.1  When point for calculation is located at the bent pipe or the elbow:

（1）When bending is being performed within or out of a plane and different stress increment is taken, calculation for equivalence composition moment should be done according to the moment of the bent pipe or elbow (see figure 9.4.2.1); and formula (9.4.2.1).

M_E = [(i_i M_i)² +(i_o M_O)² +M_t²]^0.5                                                                                                                                          （9.4.2-1）

Where:  M_E —— composition moment of hear expansion equivalence (N·mm);

        M_i —— heat expansion bending moment within the plane (N·mm);

        M_O —— heat expansion bending moment outside the plane (N·mm);

        M_t —— heat expansion twisting moment (N·mm);

        i_i —— stress intensification factor, see annex E；

        i_o —— stress intensification factor, see annex E.

（2）When bending is being performed within or out of a plane and identical stress increment is taken, i.e., when the stress intensification factor is taken from within or outside the plane, whichever is larger. the composition moment should be calculated based on the moment of the bent pipe or elbow (see figure 9.4.2-2) and formula (9.4.2-2).

   M?_E = (M_X² + M_Y² +M_Z² )^0.5                                                                                                                             （9.4.2-2）

 Where:  M?_E —— Composition moment that is not included in stress intensification factor

                                                  （N·mm）；

         M_x —— Moment along coordinate axis X direction（N·mm）;

         M_Y —— Moment along coordinate axis Y direction（N·mm）;

         M_Z —— Moment along coordinate axis Z direction（N·mm）.

 

 

Figure 9.4.2-1  Moment of bent pipe or elbow when different value of stress intensification factor is taken from within or outside the plane.

Figure 9.4.2-2  Moment of bent pipe or elbow when the stress intensification factor is taken from within or outside the plane, whichever is larger.

 

9.4.2.2  When the point to be calculated is at the crossing point of a Tee-branch:

（1）When different stress intensification factor within and out of the plane is taken, the    composition moment acted from each connection branch upon the Tee-branch point shall be   calculated according to the moment of the tee-branch (see figure 9.4.2-3) and formula    (9.4.2-1)

（2）When bending is being performed within or out of a plane and identical stress increment is taken, i.e., when the stress intensification factor is taken from within or outside the plane, whichever is larger. the composition moment that is acted upon the crossing point of the Tee-branch according to moment of the Tee-branch (see figure 9.4.2-4) and formula (9.4.2-2).

 

 

Figure 9.4.2-3  Moment of Tee-branch when value of stress intensification factor within the plane is different from that outside the plane.

Figure 9.4.2-4  Moment of the Tee-branch when value of stress intensification factor within the plane is either within or outside the p, lane, whichever is larger.

Note:    ①        In the above diagram, position of moment is only a sketch for general view.

Moment acts on each crossing point of Tee-branch shall be mandatory.

         ②        Every three composition moment at each crossing point of the Tee-branch shall be

        used for stress calculation respectively

         ③        The above calculation can also be used for calculating branch connection of other

        types.

9.4.2.3  When the point to be calculated locates at a straight pipe, the intensification factor for calculation of equivalence composition moment shall be taken as 1, and calculated according to formula 9.4.2.1.

9.4.3  Calculation for section factor shall meet the following stipulations:

9.4.3.1  Section factors of straight pipe, bent pipe, elbow, main pipe and branch pipe of equal-diameter Tee branch and main pipe of reducing branch shall be calculated according to formula (9.4.3-1):

W =	p	（Do4 – Di4）                                                                                         （9.4.3-1）
	32Do

Where:    D_o —— external diameter of pipe (mm);

          D_i —— internal diameter of pipe (mm);

          W —— section factor (mm³)

9.4.3.2  The effective section factor of branch pipe of reducing branch shall be calculated according to formula (9.4.3-2).

                                    W_B = p (r_m)² t_eb                                                                                                                                     （9.4.3-2）

Where:    W_B —— effective section factor of branch pipe of reducing Tee-branch (mm³);

          r_m —— average radius of branch pipe (mm);

          t_eb —— effective thickness of branch pipe of Tee-branch, taken from either Ttn or

                  i_it_tn, whichever is smaller (mm);

          T_tn —— nominal thickness of main pipe (mm);

          t_tn —— nominal thickness of branch pipe (mm).

   Note: T_tn and t_tn shall be the nominal thickness of corresponding main pipe and branch pipe

        respectively.

9.4.4  Calculation of stress range of pipe position shift shall meet the following stipulations:

9.4.4.1  When different stress intensification factor is adopted for bending within and outside the plane, the displacement stress range at connection point of branch pipe of reducing branch or of other welded type components, shall be calculated according to formula (9.4.4-2) , while stress range for position shift at other piping components shall be calculated according to formula (9.4.4-1).

sE =	ME	（9.4.4-1）
	W

 

sE =	ME	（9.4.4-2）
	WB

Where: s_E —— calculated maximum displacement stress range (MPa)

9.4.4.2  When identical stress intensification factor is adopted for bending within and outside the plane, the displacement stress range at connection point of branch pipe of reducing branch or of other welded type components, shall be calculated according to formula (9.4.4-4) , while stress range for position shift at other piping components shall be calculated according to formula (9.4.4-3).

sE =	iM?E	（9.4.4-3）
	W

 

sE =	iM?E	（9.4.4-4）
	WB

Where:  i —— stress intensification factor.

9.4.5  The standard for evaluation of stress range of piping displacement is the maximum displacement range σE, which must meet formula (9.4.5),the following stipulations:

                                    s_E≤[s]_A                                                                                                                                                                      （9.4.5）

where:  Stress range of the permitted position shift [s]_A shall meet the rule specified in 3.2.7 of this code.

9.5.1  When piping is being designed, acting force and moment shall be calculated according to various work conditions, including initial operation period, operation, work condition after shutoff, flaccidity, and action of occasional load respectively. When friction force of sliding supporting rack id not included in computer program, reaction force of piping end(s) shall be revised (meliorated) by manual calculation.

9.5.2  When there is no cool tensile existing or cool-tensile ratios are identical in various directions, calculation of acting force and moment of piping upon end point(s) or equipment interface can be performed per the following stipulations, and is suitable to adopt simple system that has no restraint in between, but only two fixed end points.

9.5.2.1  At maximum or minimum temperature, acting force and moment of the piping against equipment or end point shall be calculated according to formula (9.5.2-1).

Rh = – [ 1 –（2/3）×CS]	Eh	RE                        （9.5.2-1）
	E20

9.5.2.2  At temperature when installation is done, acting force and moment of the piping against equipment or end point shall be calculated according to formula (9.5.2-2) and (9.5.2-3).

                                    R_C = C_S – R_E                                                                                                                                        （9.5.2-2）

or

（9.5.2-3）

 

When	[s]h	×	E20	<1, the larger value of RC and RC1 shall be taken.
	sE		Eh

 

When	[s]h	×	E20	≥1, RC shall be taken as force and moment that act against pipe end and
	sE		Eh

joint of equipment at temperature at which the piping is being installed.

Where:   C_S —— cool tensile ratio, which is to be determined by the designer and may be

                 selected between 0% ~ 100%;

         E_h —— Young?s modulus of the pipe material at maximum or minimum

                 temperature, usually Young’s modulus (MPa);

         E₂₀ —— Young?s modulus (MPa) of the pipe material at temperature at which the piping

                  is being installed , usually Young’s modulus at 20℃ can be adopted.

         R_h —— Force (N) and moment (N·mm) that the piping acts upon equipment or end

                 point at maximum or minimum temperature during initial run.

         R_c —— Force (N) and moment (N·mm) that the piping acts upon equipment or end

                 Point at temperature at which the piping is being installed.

         R_E —— Force (N) and moment (N·mm) that the piping acts upon end point, which

                 has been calculated on the basis of E₂₀ and the total-compensated value.

         R_C1—— Force (N) and moment (N·mm) that the piping, after self-equalization, acts

                upon equipment or end point at the temperature at which the piping is being

                installed.

         [s]_h ——Permitted applicable stress (MPa) of metallic material at hot condition

                (predicted temperature) within the position shift cycle in analysis.

          s_E —— calculated displacement stress scope (MPa)

9.5.3  When the piping being calculated is a complex piping system with multi-fixed points, or is adopted with different cool tensile ratio along different coordinate axes, force and moment of the piping acts upon equipment or end point shall be calculated by means of deformation coefficient of pipe element(s) at the temperature at which the piping is running in the initial period. This calculated result shall be compared with the force (N) and moment (N.mm) of the piping acts upon equipment or end point at the temperature after the piping has been installed and after self-equalization calculated according to the formula 9.5.2-3 in this code and then take the larger value of the two as force and moment of the piping acts upon equipment or end point at installation temperature.

Force and moment of the piping acts upon equipment or end point at maximum or minimum temperature shall be calculated according to the following formula:

Rh = – [ RE –（2/3）×RC]	Eh	（9.5.3）
	E20

 

9.6.1  In designing, position shift due to bending or twisting of the piping itself can be made use of to compensate heat expansion or cool contraction. If the flexibility is not sufficient, the following approaches may be adopted to improve flexibility of piping:

9.6.1.1  To adjust position of supporting frame or hanger rack;

9.6.1.2  To change layout direction of piping.

9.6.2  When approaches introduced in 9.6.1 of this code is impossible to adopt for improvement of flexibility due to restrained condition, compensation devices can be used in accordance with design parameters.

 

 

10.1.1  In design of piping support and hangers, the vertical stress of piping shall meet stipulations in 3.2.6 and 3.2.8 of this code.

10.1.2  It is preferential to select standard and universal supports and hangers. Parts and components of supports and hangers that are subjected to stress shall be calculated for strength and rigidity.

 

10.2.1  Location and type of supports and hangers shall meet the requirement of situation of piping layout and flexibility calculation. Effective, including special type, supporting racks can be selected to control piping position shift and to prevent piping from vibration.

10.2.2  Piping installed with expansion compensation buffers, device such as fixed rack, direction guiding rack and position-retarding rack shall meet products’ characteristics and requirement of application.

10.2.3  When supports and hangers are rooted in components of buildings or construction structures, such components shall have sufficient strength and rigidity.

10.2.4  Setting up supports and hangers shall not impact operation and maintenance of the piping.

10.2.5  When there are components that have huge gravity exist in piping, space between every two supports and hangers shall be calculated and rechecked, otherwise additional supports and hangers shall be provided.

10.2.6  Setting up supports and hangers shall control bending moment adjacent to branch pipe connection point and flange connection to be within safety range.

10.2.7  Maximum space between every two horizontal supports and hangers shall meet strength and rigidity conditions. The mandatory condition for strength is to control that the bending stress of piping itself due to its gravity shall not be beyond 50% of the permitted stress of the material at designed temperature. Condition for rigidity is to restrain the deflection, which shall not be beyond 15mm for usual piping. Deflection of piping outside the processing unit may be somehow liberalized but shall not be beyond 38mm. For steam piping without slope, no more than 3 mm.

When less deflection is necessary for piping that has special requirement, it can be determined in accordance with existing stipulations stipulated by Government Authority.

10.2.8  For piping with slope that is not allowed to accumulate liquid in, its supports and hangers, in addition to that the space between every two rack shall meet requirement in10.2.7 of this code, the relation between deflection and slope shall meet the requirement in formula (10.2.8)

（10.2.8）

Where:  Y_S —— bending deflection due to gravity of piping (mm);

        L_S —— space between every two racks (mm);

        i_S —— slope of piping.

10.2.9  For piping with pressure pulse, when space between every two racks is being made, its natural frequency shall be checked so as to prevent resonance from happening.

 

10.3.1  In designing, supports and hangers shall bear the following loads:

10.3.1.1  It shall bear various gravity as well as gravity of components of supports and hangers stipulated in clause 3.1.6 of this code.

10.3.1.2  It shall bear the following loads that may change during operation:

（1）Reactions and moment due to heat expansion, cool contraction and other position shift;

（2）Transferred loads from elastic supports and hangers upon rigid supports and hangers;

（3）Internal pressure force and elastic force from unbalanced bellow expansion joint or compensation buffer with packing gland;

（4）Friction force of sliding supports and hangers.

10.3.1.3  After flexibility of piping has been calculated, load of supports and hangers shall be consistent with calculated result of flexibility. If friction force of sliding supporting rack or other load have not been considered in flexibility computing program, it shall be included in calculation of the load of supports and hangers.

10.3.1.4  Occasional and incidental loads such as gravity coming from hydraulic test, purging, passivation, stress due to fluid sudden change inside piping, reacting force due to fluid discharging, wind and earthquake shall be included in calculation according to the situation of engineering project.

10.3.2  The load combination of supports and hangers shall be calculated according to various situations individually, and all loads that act on the supports and hangers simultaneously shall be combined and then select the worst condition as basis for calculation.

10.4.1  Materials used for supports and hangers shall meet the following stipulations:

10.4.1.1  Materials used for supports and hangers of piping shall meet the stipulations in section 4 in this code.

10.4.1.2  Materials used for parts and components of supports and hangers that directly contacts piping components shall be selected per temperature identical to designed temperature of piping; materials used for parts and components of supports and hangers that is welded onto components of piping shall be compatible with the materials for components of piping.

10.4.1.3  Cast iron is not suitable to be used at the place where tensile load existing; Ductile cast iron shall not bear impact load.

10.4.1.4  Wood block used as cushion for piping with cool insulation shall be of red Canadian pine or hard timber, which is not easy to crack from, dry, and shall be treated for rot-protection.

10.4.2  Permitted stress of tensile and pressure of supports and hangers components shall

be selected according to 3.2.3 and annex A of this code/ Other permitted stress shall meet the following stipulations:

10.4.2.1  Permitted shearing stress shall be preferentially 0.6 of the permitted stress of the material.

10.4.2.2  Permitted tensile stress of screw threaded tensile rod shall be no lower than permitted stress of the material by 25%.

 

10.5.1  Pipe cushion of supports and hangers and structure of its sliding part shall meet the following stipulations:

10.5.1.1  For piping without heat insulation layer, except for big pipe (nominal diameter of piping carrying liquid bigger than or equal to 500mm, and 600mm for piping carrying gas) that is attached with pipe cushion or cushion plate, piping can be directly put on the beam of piping gallery..

10.5.1.2  Sliding surface and movable part of splice shall be exposed out of heat insulation layer.

10.5.1.3  When spiral welded pipe is out on beam of pipe gallery or other structure, pipe cushion is needed.

10.5.1.4  When sliding piping cushion is being designed, the length shall be corresponding to what is necessary for heat shift of the piping position. If off-center installation is adopted, amount and direction of off-center shall be described in designing document.

10.5.2  For components of supports and hangers that directly contact components of the piping, there shall not be relative position shift between the former and the latter. When those components are being designed, stress upon pipe wall shall be controlled to prevent local plastic deformation of the piping.

10.5.3  Components of supports and hangers that contact the components of the piping, it impossible to dismantle, shall meet the following stipulations:

10.5.3.1  Local stress at the joint between components of supports and hangers and components of the piping shall be under control.

10.5.3.2  Material for pipe cushion, hanger plate, direction guiding plate, lifting lug that are directly welded onto components of the piping shall be identical to that of components of the piping. Welding, preheating and heat treatment shall meet stipulations of this code.

10.5.4  Components of supports and hangers, if possible to dismantle, shall meet the following stipulations:

10.5.4.1  Sliding motion between weight-bearing clamps on vertical piping and components of piping shall be prevented. For this purpose, stopping blocks may be welded onto components of the piping, or ribs may be welded along axis direction.

10.5.4.2  Components of supports and hangers made of carbon steel shall not directly contact components of piping made of nonferrous metal; nonmetallic material may be used as isolation layer in between, or other corresponding measures may be taken.

10.5.5  Design of connection parts of supports and hangers shall meet the following stipulations:

10.5.5.1  The maximum allowed load on screw thread bracket may be calculated according to its allowable stress and the sectional area of screw root. The diameter of lifting rod shall not be less than 10mm.

10.5.5.2  Permitted stress and the cross section area at the root of screw thread. Diameter of lifting rod shall not be less than 10mm. When there is horizontal position shift in lifting rack, both ends of the bracket shall be of splice and sufficient length should be provided between two splicing points. For rigid bracket rack, the movable bracket shall not be shorter than 20 times of horizontal position shift at the lifting point, and the angle between lifting bracket and the vertical perpendicular line shall not be bigger than 3 degrees; for elastic lifting rack, length of movable bracket shall not be shorter than 15 times of horizontal position shift at the lifting point, the angle between lifting rod and the vertical perpendicular line shall not be bigger than 4 degrees.

10.5.5.3  Lifting rod of the lifting rack shall have screw thread with sufficient length, and nut (it can be fastened or loosened freely) can be setup if necessary. Latch nut shall be provided at thread joint.

10.5.6  Selection of elastic supports and hangers, damping and buffing devices shall meet the following stipulations:

10.5.6.1  Force changeable elastic supports and hangers may be used where the piping supports and hangers has vertical position shift and bearing gravity load from that direction. Under any work condition the spring shall not bear load that is beyond permitted value. Force changeable elastic supports and hangers may be selected according to existing National Standard and shall meet the following requirement:

（1）Load change coefficient due to heat position shift along vertical direction of the piping shall be calculated according to formula (10.5.6):

fS =	D·KS	×100%                                                                                                                           (10.5.6)
	FH

Where:     f_S —— load change coefficient;

           D —— vertical heat position shift of piping (mm);

           K_S —— rigidity of spring (N/mm);

           F_H —— work load (N)

Load change coefficient shall not be more than 35%, for important piping and piping connected to sensitive equipment , no more than 25%.

（2）Force changeable elastic supports and hangers shall have stroke indicator and position locking unit and shall be only used within the range indicated by the indicator. When it is at the locked position, twice of maximum workload is allowed to add on. Simple force changeable elastic supports and hangers without external cylinder can only be used under the condition that accurate calculation for load and position shift is not necessary.

（3）Measure shall be taken so that eccentricity bending or eccentric load of spring or unexpected invalidity can be prevented.

10.5.6.2  When huge amount of position shift occurs along vertical direction at the point where the piping is being lifted, constant force elastic supports and hangers can be used, which shall meet the following stipulations:

（1）Indicator for load and stroke as well as position lock unit shall be equipped. When it is at locked position, the component shall be able to bear as twice as usual maximum load .

（2）Structures that may readjust load at site, added or subtracted amount of readjustment shall not be less than 10% of designed load;

（3）When nominal position shift amount of constant force elastic supports and hangers is being selected, in addition to meeting the requirement of calculation of position shift of supports and hangers, a margin shall be reserved according to different accuracy requirement of calculation of load and position shift.

10.5.63  Selection of damping and buffing units shall meet the following stipulations:

（1）Elastic damping can be selected for damping unit for piping, for which the structure shall be better to meet the following stipulations:

It should bear vibration force of the piping instead of gravity of the piping, with maximum    vibration-preventing force not less than the value required by engineering designing and    shall have adjustable structure.

The maximal stroke shall be determined according to such factors as its adjustable vibration-proof ability, piping displacement, etc.

（2）Structure design of buffing unit shall be better to meet the following stipulations:

It should not restrict heat expansion and cool contraction of the piping, neither bear gravity of the piping;

It should be able to bear transient maximum dynamic load that is required by dynamic analysis of piping, and should have high damping function under that work condition;

Working medium in hydraulic damping unit shall be fire-retarding oil;

The effective stroke shall be bigger than the position shift value along axis direction of the damping unit due to piping position shift.

10.5.7  Design of steel structure, which is connected to civil engineering items or equipment, shall meet the following stipulations:

10.5.7.1  Shall meet the requirement of strength at maximum load.

10.5.7.2  Shall meet the requirement of rigidity condition:

（1）When used for fixed supporting rack, position-restraining and buffing units, the maximum deflection of beam shall not be bigger than 0.002 times of the calculated length of the beam;

（2）When used for other supporting racks, the maximum deflection of beam shall not be bigger than 0.004 times of the calculated length of the beam;

（3）When projecting beam is used, the jib arm shall be better not longer than 800mm.

10.5.7.3  When non-symmetric structural section steel is used and the acting point of bearing does not go through the bending center, influence of twisting distortion due eccentric reaction shall be checked during designing.

COMPONENTS FABRICATION, PIPING

CONSTRUCTION AND INSPECTION

 

11.1.1  For requirement on project construction and inspection, in addition to meeting stipulations in this code, it shall also meet stipulations in existing National Standard “ Procedure for Project Construction and Inspection-acceptance of Industrial Metallic Piping” (GB50235).

 

11.2.1  Selection of welding materials and preheat before welding shall meet the regulation of existing National Standard “ Welding Project Construction and Inspecting Acceptance for Construction Site Equipment and Industrial Metallic Piping” (GB50236)

11.2.2  Valves whose ends are to be welded to connect shall be welded per such procedure of welding and heat treatment that damage of leak tightness shall be prevented.

11.2.3  Welding of branch pipe shall meet stipulations in 5.4.4.2 in 5.4.4 of this code , in which the type of welding branch pipe in shown (see figure 5.4.4-1).

11.2.4  Welding structure shall meet stipulations in annex H of this code.

 

11.3.1  Heat treatment for pipe and piping components after being formed, in addition to meeting stipulations in article G.1 of annex G, when heat treatment is needed for piping that is subjected to stress corrosion and other piping that is seriously required to release residual stress, details shall be clearly described in designing documents.

11.3.2  Thickness of piping components that needed to be post heat treated after welding shall meet stipulations in article G.2 of annex G in this code.

 

11.4.1  The designer shall sort the piping being designed according to fluid category, designed pressure, designed parameter of temperature and whether extreme vibration exist. Such sorting shall be listed in designing document as base of inspection.

11.4.2  Except for those are under special requirement, nondestructive inspection may be performed according to stipulations in annex F of this code.

11.4.3  Inspection for piping fabrication shall meet stipulations in 5.2.1 and 5.2.4 in this code.

11.5.1  Pressure for hydraulic and air pressure test of piping that is subjected to internal pressure shall meet existing National Standards. Piping tested under air pressure shall be designated in designing document.

11.5.2  For piping containing gas, if hydraulic test in whole is not available, it can be tested hydraulically in sections and then accept 100% nondestructive inspection at fixed ports after installation, but a leak-tightness test shall be performed after above inspection is passed.

11.5.3  Under conditions of hydraulic test or air pressure test, internal pressure circle stress of components shall not be beyond stipulations in formula (11.5.3-2) and (11.5.3-3). If this is not the case, testing pressure shall be lowered down. Under testing condition the circular stress shall be calculated per formula (11.5.3-1):

sT =	PT [Do –（tsn – C）]	(11.5.3-1)
	2（tsn – C）

for hydraulic test,                    s_T≤0.9E_js_s                                                             (11.5.3-2)

for air test,                   s_T≤0.8E_js_s                                                      (11.5.3-3)

Where:       s_T —— circular stress of components under testing condition(MPa);

             D_o —— external diameter of pipe (mm);

             t_sn —— nominal thickness of pipe (mm);

             C —— Sum of all thickness additional amount (mm);

             E_j —— coefficient of welding joint;

             P_T —— testing pressure (MPa);

             s_s ——standard yield point of material of material (MPa).

11.5.4  Hydraulic test for piping that is subjected to external pressure shall meet the following stipulations:

11.5.4.1  Vacuum piping may be tested with pressure equivalent to internal pressure of 0.2MPa. For large diameter piping that needs to be tested for stability, the stability shall be tested through calculation and check by means of testing pressure.

11.5.4.2  Internal pipe inside jacketing pipe shall first be hydraulically tested, only those passed the test can the jacket be worked with. The jacketing pipe shall be hydraulic tested according to 11.5.1 in this code.

11.5.4.3  Internal pipe inside jacket shall be tested with internal pressure, which shall be the higher pressure of both internal and external sides. However, the designer should check stability of the internal pipe under the condition that an external pressure test is being done.

11.5.5  Alternative test is allowed for piping if both hydraulic or air test is not available. This shall be clearly described in the designing document. Piping being treated with alternative test shall meet the following stipulations:

11.5.5.1  All circular weld seams shall 100% tested by radiography;

11.5.5.2  Air tightness shall be performed after inspection.

11.5.5.3  Nondestructive inspection for piping component shall be performed according to annex J in this code.

11.5.6  Piping that requires air tightness test shall meet the following stipulations:

11.5.6.1  For piping containing category B fluid, air tightness testing pressure equals to esigned pressure, at which flanges, screws and gaskets shall be checked for leakage; if no bobbles appear, the test is proved qualified. Piping used for transmitting gases with low vaporizing temperature such as refrigerating medium shall also be tested for air tightness.

11.5.6.2  For vacuum piping, a vacuum degree test shall be performed for 24hours after hydraulic test if finished and passed. If pressure increment is not more than 5%, it proves vacuum degree is qualified.

 

11.6.1  Temporary spot welding for fixing component position is not allowed. Any structural parts of instrument or electric device are not allowed to weld onto sliding supporting rack.

11.6.2  When smaller diameter branch pipe is introduced out of a main pipe where heat position shift exists, the type and structure of the smaller branch pipe shall meet requirement of design and shall not restrain position shift of the main pipe. Any supporting structure to be decided at site is limited within ambient temperature scope and pipe whose nominal diameter less than or equal to 40mm.

11.6.3  When piping of large storage tank (or large water pool) connected to pump or other equipment with independent foundation, or when piping under bottom of the storage tank is laid onto racks along the ground surface, influence of foundation sedimentation must be noticed and taken care of. Such kind of storage tank is required to install after hydraulic test is qualified, or the flanges at joint port of the storage tank shall be connected after hydraulic test and the initial stage of foundation sedimentation.

11.6.4  Except for piping that is internally lined with refractory material is required to weld according to design, other nonmetallic internal lining of piping shall not be welded at construction site. Component of supports and hangers that is to be welded onto piping components shall have been welded in factory during prefabrication.

11.6.5 For final length of each sealed pipe that has nonmetallic lining, the pipe should be measured at site before delivering to the fabricating factory, or measures conformed by other design or stipulated in 5.11.5 of this code.

11.6.6  Small piping that has not been shown in piping layout drawing, whose layout direction is to be decided at construction site, including tracing pipe and instrument pipe, shall be arranged neatly and tidy with reasonable layout direction, and installed after other piping installation is finished. Such small piping shall be installed according to regulation of project, designing documents.

INSULATION, NOISE ELIMINATION

AND ANTI CORROSION

12.1  Heat Insulation

12.1.1 The calculation, material selection and structural requirements regarding heat insulation and cold insulation of piping may be designed according to the existing State standards of General Technical Stipulations for Heat Insulation of Equipment and Piping GB/T4272, Guiding Stipulations for the Design of Heat Insulation of Equipment and Piping, GB/T8175, General Technical Stipulations for the Cold Insulation of Equipment and Piping GB/T11790 and Specifications for the Engineering Design of Heat Isolation of Industrial Equipment and Piping GB50264.

12.1.2 Galvanized heat insulation auxiliary material is strictly prohibited to contact stainless steel pipe.

12.1.3 The structure of heat insulation for heat coupling piping shall be in conformity with following stipulations:

12.1.3.1 Heat coupling pipe of carb, on steel shall be isolated with non-metal material from stainless steel pipe.

12.1.3.2 When local over heat is not allowable to the fluid or piping material, heat insulation pieces shall be used to separate heat coupling pipe from the pipe coupled.

12.1.4  In case the heat insulation material, such as rock wool or other mineral wool, is used to austenite stainless steel pipe, its content of chloride shall not exceed the value looked over from Figure 12.1.4.

Figure 12.1.4 The Relationship Between the Allowable Chloride Content and the Content of  (Na + SiO₃) in Heat Insulation Material of Rock Wool and Mineral Wool.

12.1.5 The outer protection layer of the heat insulation structure shall effectively prevent heat insulation layer from any rain entering.

 

12.2  Acoustical Insulation and Noise Elimination

12.2.1 The requirements for anti noise shall be in conformity with the stipulations in existing State standard GBJ87 the Design Specifications for the Control of Noise in Industrial Enterprises.

12.2.2 For the piping connected to centrifugal compressors, screw compressors and axial-flow compressors and the piping with pressure reducing valves of large pressure differential, measures for acoustical insulation shall be taken when noise exceeds 90db.

12.2.3 In general, if soft material is used to make acoustical insulation layer, the outer protection layer may use the same material as the outer protection layer of heat insulation structure.

12.2.4 The out door acoustical insulation structure shall be able to prevent any rain entering.

12.2.5 The acoustical insulation material for stainless steel pipe shall be in conformity with the stipulations in 12.1.4 of this code.

12.2.6 Silencers shall be installed to vent piping if the noise exceeds the specified value.

 

12.3  Anti Corrosion and Painting

12.3.1 The out surface of buried steel piping shall have anti corrosion layer. The number of anti corrosion layer shall be determined according to the conditions of the piping designed and the soil as well. When necessary, cathode protection measures may be added to the long distance piping in an area, which is not convenient for checking and maintenance.

12.3.2 For the anti rust of the outer surface of on-ground piping, in general, paint application is adopted. The category of the coating shall be able to resist the corrosion of environmental atmosphere.

12.3.3 The primer and the finishing paint of the coating shall be used in association. For the piping with outer heat insulation layer, in general, just primer is applied. Paint may not be applied to stainless steel, non-ferrous metal and galvanized steel piping.

12.3.4 The cleaning of the outer surface of the piping prior to the application of painting shall be in conformity with relevant requirement of the coating products. If there is special requirement, it shall be specified in the design documents.

12.3.5 For the color and the mark of the painting, the existing State standard The Basic Identification colors and identification Symbols for Industrial Piping BG7231 and relevant standards may apply. If there is any supplementary requirement, it shall be specified in engineering design documents.

 

13.  SUPPLEMENTARY STIPULATIONS FOR  PIPING

DELIVERING CATEGORY A1 FLUID AND

CATEGORY A2 FLUID

 

13.1  Supplementary Stipulations for Piping Delivering Category A1 Fluid

13.1.1  The design conditions shall be in conformity with following supplementary stipulations:

13.1.1.1  When any temperature other than fluid temperature is used as design temperature, calculation for heat transmission shall be made or lab verified.

13.1.1.2  In piping design, analysis of dynamic load shall be made to minimize the harmful vibration and pulse to the degree of no harm.

13.1.1.3  Severe cyclic condition may be prevented through piping layout and piping components selection.

13.1.1.4  The design shall not be made according to 3.2.2 of this code.

13.1.1.5  The maximum release pressure for pressure releasing devices shall not exceed 1.1 times of the designed pressure.

13.1.2  The selection of materials shall be in conformity with following supplementary stipulations:

13.1.2.1  No fragile material shall be used.

13.1.2.2  Lead, tin and their alloys are only used as lining.

13.1.3  The selection of piping components shall be in conformity with following supplementary stipulations:

13.1.3.1  The selected of welded steel pipe shall be in conformity with stipulations in Appendix J of this code。

13.1.3.2  The change of the direction of one welding beam of miter bend shall not exceed 22.5°.

13.1.3.3  Requirements for the selection of end expanded and edge over turned flange nipple:

（1）The application temperature shall not exceed 200℃ and the application pressure shall not exceed the allowable pressure for standard flange of carbon steel with nominal pressure of 2.0MPa;

（2）The pipe diameter shall not be larger than 100mm nominal diameter. The wall thickness before end expansion shall not be smaller than following values:

   Nominal Diameter   15~20mm    Min. Wall Thickness       2.5mm

                                    25 ~ 50mm                              3.0mm

                                    65 ~100mm                             3.5mm

13.1.3.4  For branch connections, standard tees shall be priority. Secondly, the branch platform or embedded type branch shall be selected.

13.1.3.5                       Requirements for selection of valves:

（1） Valves, of which the leakage at valve stem packing could be prevented, shall be used, including cock type or other valves with reliable sealing structure.

（2） Valve bonnet shall be flange connection with at least 4 bolts. The connection type of straight thread with sufficient mechanical strength shall be adopted. Seal welding shall be made to the sealing structure of metal to metal contact.

13.1.3.6  Requirements for selection of flanges:

（1） Flat welded (plain plate type) flanges shall not be used;

（2） When selecting the nominal pressure of flanges, an allowance equals to or more than 25% but not less than 2.0MPa shall be provided.

（3） When soft gaskets are used, flanges with concave-convex surfaces or groove and tongue surfaces shall be selected.

13.1.3.7  Socket welded piping fittings shall only be used to piping with nominal diameter less than or equal to 40mm.

13.1.3.8  Conical thread sealing structures shall only be used to piping with nominal diameter less than or equal to 20mm and seal welding is used as well.

13.1.3.9  When structures of straight thread with gasket sealing are used, the structures of which the sealing surfaces of the components will not relatively rotate at and after tightening shall be used. For example, the structures of (b) and (c) in Figure 5. 9. 3-2 of 5.9.3 of this code.

13.1.3.10  Requirements for selection of piping joints:

（1）Branze welded joints shall not be used;

（2）Bonded joints, expansion - connected joints and joints with packing filled into the joint shall not be used;

（3）Lining ring of several pieces shall not be used in butt welds.

13.1.3.11  Compensating pieces with packing sealing shall not be used.

13.1.3.12  The selection of the thickness of the stainless steel butt-welded fittings shall be in conformity with what specified in D.0.1 in Appendix D of this code.

13.1.4  The arrangement of piping shall be in conformity with following supplementary stipulations:

13.1.4.1  Piping should not be installed under the ground in an area of inconvenient maintenance except reliable safety measures are provided. When the process requires the underground installation, safety measures for leakage monitoring, corrosion prevention and harmful fluid collection shall be provided.

13.1.4.2  For the piping installed in safety isolation walls and isolation plates, their manual valves shall use extension levers to be extended and operated out of the walls or plates.

13.1.4.3  Piping for category A1 fluid shall not be arranged in passable pipe trenches.

13.1.4.4  Category A1 fluid shall be drained into a closed system, not to sewage or atmosphere directly.

13.1.5  The calculation of flexibility shall not use simplified analysis method.

13.1.6  The construction and inspection of piping shall be in conformity with following supplementary stipulations:

13.1.6.1  Post weld heat treatment shall be performed when the wall thickness of carbon steel pipe is ≥19mm.

13.1.6.2  Airtight test shall be made to the piping.

13.1.6.3  The non-destructive inspection of the piping construction shall be in conformity with what specified in Appendix J of this code.

 

13.2  Supplementary Stipulations for Piping Delivering Category A2 Fluid

13.2.1  High silicon cast-iron shall not be used to the piping for category A2 fluid.

13.2.2  Valves with reliable sealing structure to prevent leakage at valve stem packing shall be used.

13.2.3  Apart from the requirements for corrosion resistant, valves of steel body shall be used.

13.2.4  Safety protection measures shall be taken for glass levels and sight glasses.

13.2.5  The air vent ports shall be in conformity with environment protection requirements. Liquids shall not be drained directly into sewage.

13.2.6  Flat welded (plain plate type) flanges shall not be used.

13.2.7  When using thread sealing, it shall not be larger than 20mm nominal diameter and it shall be seal welded.

13.2.8  Compensating pieces with packing sealing shall not be used.

13.2.9  Article 8.1.2 of this code also applies to category A2 fluid.

13.2.10  Piping for category A2 fluid shall not be arranged in passable pipe trenches.

13.2.11  Airtight test shall be made to the piping for category A2 gas.

13.2.12  The non-destructive inspection of the piping shall be in conformity with what specified in Appendix J of this code.

13.2.13  For the piping for category A2 fluid of Class II (high) hazardous, in addition to meeting what specified in 13.2.1 to 13.2.12 of this code, it shall also be in conformity with what specified in (3) of clause13.1.3.6 of article13.1.3, clause 13.1.3.9 of article 13.1.3 and (2) of clause 13.1.3.10 of article 13.1.3.

 

14. SAFETY STIPULATIONS FOR PIPING SYSTEM

 

14.1  General Stipulations

14.1.1  For the requirement of the safety design of piping system, apart from the stipulations in this section, it shall also be in conformity with stipulations of relevant safety stipulations in existing State standard.

 

14.2  Over Pressure Protection

14.2.1  Pressure release devices shall be installed for piping system of which the pressure may be exceeded during operation, in addition to stipulations in 3.2.2 of this code. The pressure release devices may use safety valves, blow up blades or the combination of the two.

14.2.2  Blow up blades may be used in those cases in which safety valves are not suitable. When designing the blow up blades, certain allowance should be given to the difference between the designed blow up pressure and the maximum normal working pressure of the blow up blades. This value of difference shall be determined according to the material of blow up blades and the pulse of working pressure.

14.2.3  Safety valves shall be selected according to the gas (vapor) or liquid vented or drained and the influence of the back pressure shall also be taken into consideration.

14.2.4  The opening pressure (setting pressure) for safety valves shall be 1.1 times normal working pressure as maximum and 1.05 times normal working pressure as minimum otherwise the process specified. However the opening pressure for the piping stated in clause 3.1.2.2 of article 3.1.2 of this code shall take the condition of article 3.1.2 of this code and the greater value of the designed pressure for that piping.

14.2.5  The pressure loss on the inlet pipe of the safety valve should not be 3% less than the opening pressure while the pressure loss on the outlet pipe of the safety valve should not be 10% higher than the opening pressure.

14.2.6  The maximum release pressure for safety valves should not exceed 1.1 times the designed pressure of the piping. In fire accident, the maximum release pressure shall not exceed 1.21 times the designed pressure.

14.2.7  Cut-off valves should not be installed on the inlet pipes or outlet pipes of the safety valves or blow up blades. If the process specially requires the installation of cut-off valves, by-pass valves and local pressure gauges shall be provided. In normal working condition, the cut-off valves at the inlets or outlets of safety valves or blow up blades shall be locked at open status. The by-pass valves shall be locked at close status. Following symbols shall be noted in engineering design drawings:

L.O. or C.S.O = Locked at open status (must not be closed without permission).

    L.C. or C.S.C = Locked at close status (must not be opened without permission).

14.2.8  When Tee type conversion valves are installed at inlets and outlets of dual safety valves, reliable interlocking mechanism shall be provided between the two conversion valves. Empty draining measures shall be provided to the piping between the safety valves and the conversion valves.

14.2.9  When selecting and designing the pressure release devices, detailed data should be provided to manufacturers and the manufacturers shall guarantee that the performance of the products meets the requirement of the data sheet.

 

14.3  Valves

14.3.1  Check valves shall be installed on the piping where the reverse flow of the fluid should be avoided.

14.3.2  For those valves which must be strictly controlled at open or close position during normal operation, the requirements of locking or lead sealing shall be additionally added in the design and noted in drawings with symbols stated in 14.2.7 of this code. These valves are only allowable to be operated at maintenance time under strict supervision with prior permission of relevant responsible person.

 

14.4  Blind Flanges

14.4.1  When the inside of the unit is stopped for maintenance, there is probability or requirement for piping outside the unit to continue running. In addition to the installation of cut-off valves at battery limit of the unit, the blind flanges shall also be installed to valve flanges at the side of the unit.

14.4.2  During operation, in case some equipment needs to be cut off for maintenance, blind flanges shall be installed to flange connections between valves and the equipment. For category B fluid piping, if small vent valves are installed between valves and blind flanges, the piping after the vent valves shall be lead to safety places.

14.4.3  Blind flanges shall be provided to the places, which are necessary to be blocked during pressure test and airtight test.

14.4.4  Split type blind flanges, i.e. insert plates and cushion rings, should be used for the cases where the fluid temperature is lower than -5℃ or the atmospheric corrosion is severe, “8” type blind flanges should not be used.

14.4.5  Identification marks shall be provided to insert plates and cushion rings and they shall be extended out of flanges.

 

14.5  Drainage

14.5.1  The drainage of different fluids shall be in conformity with following stipulations:

14.5.1.1  Category B fluid shall be drained to a closed collection system and the direct draining to sewage is strictly prohibited.

14.5.1.2  Category B gases with density larger than that of environmental air shall be vented to flare system. Category B gases with density less than that of environmental air may be vented to atmosphere provided that no installation of flare system is permitted and they meet sanitary standard.

14.5.1.3  No-flash liquids of Category C and Category D may be drained to sewage provided that they meet sanitary standard and meet the conditions of application temperature of sewage channel materials and they are not corrosive.

14.5.2  The diameter of the process discharge pipe shall be determined according to the volume of discharge and the working pressure. The flow rate at discharge port shall be in conformity with stipulations in article 7.1.5 of this code.

14.5.3  Bird proof nets shall be provided to vent ports of normal pressure, which are not frequently used.

 

14.6  Other requirements

14.6.1  Under cold weather conditions, following anti freezing measures shall be taken for outdoor piping:

14.6.1.1  Anti freezing by pass pipe or other anti freeze measures shall be provided to the end of the cooling water header and to the inlet and outlet piping of the cooler.

14.6.1.2  In cold areas, when there is possibility of forming of condensate in gas piping or there is dead area of liquid piping (including instrument piping) or there is possibility of freezing of liquid draining pipe, the heat coupling pipe should be installed.

14.6.2  Safety protection measures shall be taken for the weak components on the piping delivering category B fluid indoor installed, such as glass level and sight glass, etc.

14.6.3  The static electricity produced in piping system may be grounded via grounding network of the equipment and civil structures. Other requirements for anti static electricity shall be in conformity with stipulations in State existing standard General Guiding Stipulations for Prevention from Static Electricity Accidents GB12158.

14.6.4  In case the fluid is not allowable to be interrupted during the operation of major equipment, safety measures of dual-pipe or installation of ring type pipe net with isolation valves should be adopted.

14.6.5  Fire blocking facilities shall be provided for following cases:

14.6.5.1  The piping for category B gases after pressure release connected to naked fire equipment, including flare piping;

14.6.5.2  When it is necessary to isolate the flammable piping (including vent piping) from the equipment connected.

14.6.6  The design of the piping for oxygen shall meet following specifications:

14.6.6.1  For the piping for the fluids of strong oxidation (oxygen and fluorine), prior to the installation and after the fabrication, de-grease shall be done section by section or by pieces in accordance with State existing standard Specification for the Construction and Acceptance of De-grease Engineering. The surfaces of all components contacting fluid shall be de-greased. The piping components after de-greasing shall be purged with nitrogen or air and then closed to avoid re-pollution. It shall be avoided that the de-greasing media  are mixed with oxygen to form a dangerous explosive mixture.

14.6.6.2  The selection of piping components for oxygen , apart form the stipulations in other sections of this codes, shall also meet following supplementary stipulations:

（1）Seamless pipes and fittings within the product series should be selected.

（2）The welding of the pipes and fittings shall adopt argon welding to make the bottom.

（3）In case the design pressure is larger than 3MPa, austenite stainless steel pipe should be used.

（4）In case pressure regulation valves are installed on the carbon steel piping and low alloy steel piping, austenite stainless pipes and fittings should be used within 1.5m before and after the pressure regulation valves.

（5）The selection of valves shall meet what specified in 5.5.9 of this code.

14.6.6.3  It is strictly prohibited to connect the piping for oxygen to the piping for category B fluid otherwise process specially designed or reliable safety measure guaranteed.

14.6.6.4 The design requirements for the flow rate limit, static electricity grounding and piping layout of the piping for oxygen shall be in conformity with State existing standard The Design Specification for Oxygen Station GB50030 and the stipulations in relevant safety technical stipulations for oxygen.

16.6.7  When jacket piping is used, following structures shall be selected according to the freezing point of the fluid, other physical changing conditions and process requirements:

14.6.7.1  Full jacket ——  jackets are provided to all pipes, fittings, flange necks (backs) and valves;

14.6.7.2  Partial jacket —— jackets are provided to all places other than flange necks (backs), valves and connection places of branches;

14.6.7.3  Simple jacket —— jackets are provided to pipes (straight pipes) and circumferential welding seams should be out of the jackets.

 

 

 

Appendix A  Allowable Stress for Metal Piping Material

 

A.0.1  For the allowable stress of normal use steel pipes, see Table A.0.1

Allowable Stress of Normal Use Steel Pipes                                                                                                   Table A.0.1

Steel No.	Standard No.	Application status	Thickness (mm)	Strength index at ambient temperature		Allowable stress (MPa) at following temperatures (℃)																Lower limit of application temperature (℃)	Notes
				sb (MPa)	ss (MPa)	≤20	100	150	200	250	300	350	400	425	450	475	500	525	550	575	600
Carbon steel pipe (welded pipe)
Q235-A Q235-B	GB/T14980 GB/T13793		≤12	375	235	113	113	113	105	94	86	77	—	—	—	—	—	—	—	—	—	0	①
20	GB/T13793		≤12.7	390	（235）	130	130	125	116	104	95	86	—	—	—	—	—	—	—	—	—	-20	⑤①
Carbon steel pipe (seamless pipe)
10	GB9948	Hot rolled，Normalized	≤16	330	205	110	110	106	101	92	83	77	71	69	61	—	—	—	—	—	—	-29 Normalized status	③
10	GB6479 GB/T8163	Hot rolled，Normalized	≤15	335	205	112	112	108	101	92	83	77	71	69	61	—	—	—	—	—	—
			16~40	335	195	112	110	104	98	89	79	74	68	66	61	—	—	—	—	—	—
10	GB3087	Hot rolled，Normalized	≤26	333	196	111	110	104	98	89	79	74	68	66	61	—	—	—	—	—	—
20	GB/T8163	Hot rolled，Normalized	≤15	390	245	130	130	130	123	110	101	92	86	83	61	—	—	—	—	—	—	-20	③ ⑤
			16~40	390	235	130	130	125	116	104	95	86	79	78	61	—	—	—	—	—	—
20	GB3087	Hot rolled，Normalized	≤15	392	245	131	130	130	123	110	101	92	86	83	61	—	—	—	—	—	—
			16~26	392	226	131	130	124	113	101	93	84	77	75	61	—	—	—	—	—	—
20	GB9948	Hot rolled，Normalized	≤16	410	245	137	137	132	123	110	101	92	86	83	61	—	—	—	—	—	—
20G	GB6479 GB5310	Normalized	≤16	410	245	137	137	132	123	110	101	92	86	83	61	—	—	—	—	—	—
			17~40	410	235	137	132	126	116	104	95	86	79	78	61	—	—	—	—	—	—

                                                                                                                                                                                                                                                                

Table A.0.1

Steel No.	Standard No.	Application status	Thickness (mm)	Strength index at ambient temperature		Allowable stress (MPa) at following temperatures (℃)																Lower limit of application temperature (℃)	Notes
				sb (MPa)	ss (MPa)	≤20	100	150	200	250	300	350	400	425	450	475	500	525	550	575	600
Low alloy steel pipe (seamless pipe)
16Mn	GB6479 GB/T8163	Normalized	≤15	490	320	163	163	163	159	147	135	126	119	93	66	43	—	—	—	—	—	-40
			16~40	490	310	163	163	163	153	141	129	119	116	93	66	43	—	—	—	—	—
15MnV	GB6479	Normalized	≤16	510	350	170	170	170	170	166	153	141	129	—	—	—	—	—	—	—	—	-20	⑤
			17~40	510	340	170	170	170	170	159	147	135	126	—	—	—	—	—	—	—	—
09MnD	—	Normalized	≤16	400	240	133	133	128	119	106	97	88	—	—	—	—	—	—	—	—	—	-50	④
12CrMo 12CrMoG	GB6479 GB5310	Normalized plus tempered	≤16	410	205	128	113	108	101	95	89	83	77	75	74	72	71	50	—	—	—	-20	⑤
			17~40	410	195	122	110	104	98	92	86	79	74	72	71	69	68	50	—	—	—
12CrMo	GB9948	Normalized plus tempered	≤16	410	205	128	113	108	101	95	89	83	77	75	74	72	71	50	—	—	—	-20	⑤
15CrMo	GB9948	Normalized plus tempered	≤16	440	235	147	132	123	116	110	101	95	89	87	86	84	83	58	37	—	—
15CrMo 15CrMoG	GB6479 GB5310	Normalized plus tempered	≤16	440	235	147	132	123	116	110	101	95	89	87	86	84	83	58	37	—	—
			17~40	440	225	141	126	116	110	104	95	89	86	84	83	81	79<, /DIV>	58	37	—	—
12Cr1MoVG	GB5310	Normalized plus tempered	≤16	470	255	147	144	135	126	119	110	104	98	96	95	92	89	82	57	35	—
12Cr2Mo 12Cr2MoG	GB6479 GB5310	Normalized plus tempered	≤16	450	280	150	150	150	147	144	141	138	134	131	128	119	89	61	46	37	—
			17~40	450	270	150	150	147	141	138	134	131	128	126	123	119	89	61	46	37	—
1Cr5Mo	GB6479 GB9948	Annealed	≤16	390	195	122	110	104	101	98	95	92	89	87	86	83	62	46	35	26	18
	GB6479		17~40	390	185	116	104	98	95	92	89	86	83	81	79	78	62	46	35	26	18
10MoWVNb	GB6479	Normalized plus tempered	≤16	470	295	157	157	157	156	153	147	141	135	130	126	121	97	—	—	—	—
			17~40	470	285	157	157	156	150	147	141	135	129	121	119	111	97	—	—	—	—

                                                                                                          

Table A.0.1

Steel No.	Standard No.	Application status	Thickness (mm)	Allowable stress (MPa) at following temperatures (℃)																				Lower limit of application temperature (℃)	Notes
				≤20	100	150	200	250	300	350	400	425	450	475	500	525	550	575	600	625	650	675	700
High alloy steel pipe
0Cr13	GB/T14976	Annealed	≤18	137	126	123	120	119	117	112	109	105	100	89	72	53	38	26	16	—	—	—	—	-20	⑤
0Cr19Ni9 0Cr18Ni9	GB/T12771 GB/T14976	Solid solution	≤14 ≤18	137	137	137	130	122	114	111	107	105	103	101	100	98	91	79	64	52	42	32	27	-196	②①
				137	114	103	96	90	85	82	79	78	76	75	74	73	71	67	62	52	42	32	27
0Cr18Ni11Ti 0Cr18Ni10Ti	GB/T12771 GB/T14976	Solid solution or stabilization	≤14 ≤18	137	137	137	130	122	114	111	108	106	105	104	103	101	83	58	44	33	25	18	13		②①
				137	114	103	96	90	85	82	80	79	78	77	76	75	74	58	44	33	25	18	13
0Cr17Bi2Mo2	GB/T12771 GB/T14976	Solid solution	≤14 ≤18	137	137	137	134	125	118	113	111	110	109	108	107	106	105	96	81	65	50	38	30		②①
				137	117	107	99	93	87	84	82	81	81	80	79	78	78	76	73	65	50	38	30
0Cr18Ni12Mo2Ti	GB/T14976	Solid solution	≤18	137	137	137	134	125	118	113	111	110	109	108	107	—	—	—	—	—	—	—	—		②
				137	117	107	99	93	87	84	82	81	81	80	79	—	—	—	—	—	—	—	—
0Cr19Ni13Mo3	GB/T14976	Solid solution	≤18	137	137	137	134	125	118	113	111	110	109	108	107	106	105	96	81	65	50	38	30		②
				137	117	107	99	93	87	84	82	81	81	80	79	78	78	76	73	65	50	38	30
00Cr19Ni11 00Cr19Ni10	GB/T12771 GB/T14976	Solid solution	≤14 ≤18	118	118	118	110	103	98	94	91	89	—	—	—	—	—	—	—	—	—	—	—		②①
				118	97	87	81	76	73	69	67	66	—	—	—	—	—	—	—	—	—	—	—
00Cr17Ni14Mo2	GB/T12771 GB/T14976	Solid solution	≤14 ≤18	118	118	117	108	100	95	90	86	85	84	—	—	—	—	—	—	—	—	—	—		②①
				118	97	87	80	74	70	67	64	63	62	—	—	—	—	—	—	—	—	—	—
00Cr19Ni13Mo3	GB/T14976	Solid solution	≤18	118	118	118	118	118	118	113	111	110	109	—	—	—	—	—	—	—	—	—	—		②
				118	117	107	99	93	87	84	82	81	81	—	—	—	—	—	—	—	—	—	—

Notes: The allowable stress for intermediate temperature may be obtained by interpolation according to the values of this table.

① The allowable stress for welded steel pipe in GB12771, GB13793 and GB14980 does not take the factor of welding joints into it. See the stipulations in 3.2.3 of this code.

② The allowable stress in that line only applies to the elements, which are permitted to have micro permanent deformation.

③ The upper limit of application temperature should not exceed the limit of blocked line. The values above the blocked line are only used to special conditions or for short period.

④ The technical requirements for the steel pipes shall meet what specified in Appendix A of Steel Made Pressure Vessels GB150.

⑤ For materials with low limit of application temperature of -20℃, according to the stipulations in 4.3.1 of this code, they should be used under the condition above -20℃ and no low temperature toughness test is needed.

A.0.2  For the allowable stress of normal use steel plates, see Table A.0.2

Allowable Stress of Normal Use Steel Plates                                                                                      Table A.0.2

Steel No.	Standard No.	Application status	Thickness (mm)	Strength index at ambient temperature		Allowable stress (MPa) at following temperatures (℃)																Lower limit of application temperature (℃)	Notes
				sb (MPa)	ss (MPa)	≤20	100	150	200	250	300	350	400	425	450	475	500	525	550	575	600
Carbon steel plate
Q235-A·F	GB/T912	Hot rolled	3~4	375	235	113	113	113	105	94	—	—	—	—	—	—	—	—	—	—	—	0	①
	GB/T3274		4.5~16	375	235	113	113	113	105	94	—	—	—	—	—	—	—	—	—	—	—
Q235-A	GB/T912	Hot rolled	3~4	375	235	113	113	113	105	94	86	77	—	—	—	—	—	—	—	—	—	0	①
	GB/T3274		4.5~16	375	235	113	113	113	105	94	86	77	—	—	—	—	—	—	—	—	—
			>16~40	375	235	113	113	107	99	91	83	75	—	—	—	—	—	—	—	—	—
Q235-B	GB/T912	Hot rolled	3~4	375	235	113	113	113	105	94	86	77	—	—	—	—	—	—	—	—	—	0	①
	GB/T3274		4.5~16	375	235	113	113	113	105	94	86	77	—	—	—	—	—	—	—	—	—
			>16~40	375	235	113	113	107	99	91	83	75	—	—	—	—	—	—	—	—	—
Q235-C	GB/T912	Hot rolled	3~4	375	235	125	125	125	116	104	95	86	79	—	—	—	—	—	—	—	—	0
	GB/T3274		4.5~16	375	235	125	125	125	116	104	95	86	79	—	—	—	—	—	—	—	—
			>16~40	375	235	125	125	119	110	101	92	83	77	—	—	—	—	—	—	—	—
20R	GB6654	Hot rolled or normalized	6~16	400	245	133	133	132	123	110	101	92	86	83	61	—	—	—	—	—	—	-20	③⑤
			>16~36	400	235	133	132	126	116	104	95	86	79	78	61	—	—	—	—	—	—
			>36~60	400	225	133	126	119	110	101	92	83	77	75	61	—	—	—	—	—	—
			>60~100	390	205	128	115	110	103	92	84	77	71	68	61	—	—	—	—	—	—