HG/T 20646.5-1999 Technical regulations for design of piping materials for chemical plants
Some standard content:
Chemical Plant Pipe Material Design Technical Regulations HG/T20646.5-1999
This regulation is a guiding technical document for the preparation of professional documents for pipeline material control in chemical engineering design. 1.2 Scope
1.2.1 This regulation is only applicable to the pipelines shown on the process pipeline instrument flow diagram (PID), excluding instrument pipelines and automatic control valves and ventilation, water supply and drainage, fire protection and other pipelines. 1.2.2 This regulation does not apply to the following scope: 1 When the pipeline is connected to the equipment
1) When connected to the equipment pipe mouth, the equipment manufacturer is required to provide flanges that match its pipelines 2) When the pipeline provided by the equipment manufacturer as part of the equipment is connected to the pipeline of this design, the manufacturer shall provide flanges, gaskets and fasteners that match it. 3) Matching flanges, gaskets, and fasteners for special purposes on the equipment pipe mouth. 2This regulation does not include special pipe fittings proposed by the system professionals, such as steam traps, safety valves, flow restriction orifices, burst plates, filters, sight glasses, emergency eyewashes, flame arresters, hydraulic valves, electric valves, pressure reducing valves, compensators, flexible hoses, silencers, etc.
3 Regulations for thermal insulation design and painting design.
The design of pipeline materials shall comply with ASMEB31.3 "Process Piping" and HG20695 "Chemical Piping Design Specifications" standards.
Manufacturing, tolerances, testing and inspection shall be carried out in accordance with the adopted standards and specifications. 10.7
3 Key points for the formulation and classification of pipeline material grades
3.1 Formulation of pipeline material grades
Based on the conditions provided by the system professionals, the pipeline material grades of the device area shall be compiled according to the type of conveyed fluid, temperature, pressure, corrosion characteristics, etc., so that they can be divided into different categories and grades. Then, according to the divided grades, their material standards are determined, and the specifications, ranges, characteristics, materials and standards of the pipes, valves, flanges, pipe fittings, fasteners, gaskets, etc. used in each grade are clearly defined. The pipeline material grade code uses numbers and English letters to represent the pressure grade and main material category of the pipeline respectively.
The contents specified in the pipeline material grade table are the guidelines that all relevant professionals should follow. The reference format and compilation regulations of the pipeline material grade table can be found in Chapter 3 of HG/T20646.2 "Chemical Plant Pipeline Material Design Engineering Regulations", and the regulations on pipeline material grade codes can be found in Chapter 1 of HG/T20646.2 "Chemical Plant Pipeline Material Design Engineering Regulations".
3.2 Temperature and pressure range
General metals, pipe fittings, etc. can use the temperature and pressure rating table of flanges. It refers to the maximum non-impact working pressure that can be borne at different working temperatures. Especially for pipe fittings used at high temperatures, the temperature and pressure rating table is an extremely important parameter in the design.
The allowable design pressure at the design temperature can be calculated as follows: (a)t
PA-PNx
×(0)x
PA is the allowable design pressure at the design temperature, MPa; PN—nominal pressure, MPa;
(o)—the allowable stress of the material at the design temperature, MPa#(α)—the allowable stress of the material at the calculation temperature used to determine the thickness of the component, MPa. Since the standards of various countries have different reference temperatures for different materials, the flanges with the same nominal pressure value have different allowable working pressures at the same temperature. Similarly, when the operating temperature is different from the reference temperature, the allowable working pressure 110
is also different from the nominal pressure.
When compiling the pipeline material grade table, this point must be paid attention to. The temperature-pressure rating of non-metallic and lined pipelines must be tested and have usage experience before they can be used. 3.3
Boundary points and ranges of pipeline material grades
3.3.1 Classification of process pipeline grades
Classification of process pipeline grades must follow the different grade boundaries marked on the PID. 1 Pressure grade of pipelines connected to high and low pressure systems 1) When a pipe is connected to another pipe of different material or pressure, the valve or flange connecting the two pipes shall be selected according to the material or pressure grade of the pipe with the higher grade specification. 2) When two fluids with different pressure and temperature parameters are connected together, the selection of the valve that separates the two fluids shall be determined by the conditions at the most serious end. The pipeline on either side of the valve shall be selected according to the conveying conditions it is connected to.
3) When multiple pipelines with different pressures and temperatures are connected to the same component. The component shall be divided according to a set of temperature and pressure under the most serious conditions of the combination of pressure and temperature. 4) When butt welding valves are used, welding rods of the material on the higher grade side shall be selected for welding. 5) After using a regulating valve or a pressure reducing valve, when the pressure and temperature of the medium change, the cut-off valve and bypass valve after the regulating valve should be considered according to the pressure level before the regulating valve or the pressure reducing valve. HL
6) When a throttle valve or a flow limiting orifice plate is used to produce a low-temperature effect, the throttle valve should be considered according to the material of the low-temperature valve, and the pressure level should be selected according to the pressure before throttling.
7) When the material changes after passing through the check valve, the material of the check valve should be selected from high-end materials. 8) When the equipment discharge pipeline is to the ditch or discharged to the atmosphere, the valve should be used as the boundary, and the valve should be high-grade. 2 Welding connection of different metals at high temperature and flange connection of austenitic steel and carbon steel 1 When flange connection is used between austenitic stainless steel and carbon steel, an austenitic stainless steel flange is used at one end of the carbon steel pipe, and the stainless steel flange is welded to the carbon steel pipe. HT
2) When the equipment is a reactor using stainless steel or high alloy steel, and the pipeline is another alloy or carbon steel, a transition short pipe should be designed. The alloy contained in the transition short pipe appears at both ends of the short pipe or between the two materials. When welding the transition short pipe, use high-end welding rods. 3) The material of the assembly clamps and pipe rack pads welded on the pipes and pipe fittings should be the same as the parent material. 4) When the flanges in the aluminum pipeline are fastened with steel bolts and nuts, washers should be provided for isolation. Avoid corrosion caused by electrochemical effects caused by different materials.
Corrosion allowance
4.0.1 The corrosion allowance of the pipeline in the project should be based on the values listed in the "Material Memorandum". 4.0.2 The value of the corrosion allowance is determined according to the experience of the process plant manufacturer and the test data of the laboratory. In engineering design, it is generally determined by multiplying the annual corrosion rate (mm/a) of the material in the fluid by the service life of the device (generally 8 to 15 years).
The relationship between corrosion rate and material selection is shown in Table 4.0.2. Table 4.0.2 The relationship between corrosion rate and material selection Selection
Annual corrosion rate
Corrosion degree
Corrosion allowance mm
Can be fully used
No corrosion
Can be used
0.05~0.005
Light corrosion
Try not to use
Usually, the corrosion allowance of materials in non-corrosive fluids is selected as follows: Carbon steel
Low alloy steel
Stainless steel
High alloy steel
Non-ferrous metals
Heavy corrosion
>5~6
For carbon steel and low alloy steel pipelines with compressed air, steam and cooling water as the fluid, the minimum corrosion allowance is 1.27mm.
4.0.4 When the fluid is highly corrosive, the wall thickness should be increased accordingly when calculating the wall thickness. Sometimes, although the service life is only 2 to 5 years, it is allowed to be replaced regularly because it is cheaper than stainless steel. This requires a technical and economic comparison and a clear description in the technical documents, regular measurement of wall thickness and replacement of pipes. 4.0.5 When stainless steel is used, non-metallic materials or lining materials can be used to replace stainless steel in parts where the temperature is not high.
When using carbon steel pipes with a large corrosion margin, stainless steel can be used for pipes below DN50. 113
Restrictions on the use of pipe diameters
5.0.1 The pipe diameter is determined by the system professionals based on production scale, flow, pressure, flow rate and other conditions. The minimum diameter of the pipelines usually taken is as follows:
Process pipelines (medium and low pressure)
(high pressure)
Public material pipelines
Pipes on the pipeline gallery
Underground pipelines
Underground drainage pipelines
Pipes with high viscosity and easy to block fluids
Drain pipes
High-point vent pipes
DN20 (when the main pipe is DN15, a DN15 drain pipe can be used) DN15
Steam accompanying pipes and instrument pipes, high-pressure equipment leak detection pipes are selected according to needs. 5.0.2
5.0.3 Avoid using pipes and pipe fittings of specifications such as DN32, DN65, DN125, DN175, DN225, DN550, DN650, DN750, DN850, and DN950 for process equipment pipelines. 5.0.4 When the imported equipment adopts the British standard, avoid using pipes and fittings with specifications such as 1%, 2%, 3, 5″, and 9\.
5.0.5 When the size of the equipment connection port is the above specifications, a reducer should be used at the equipment port to immediately adjust it to the standard specifications (except for reasons such as specific flow rates in process pipelines). 114
Requirements for end connections
The end connections of metal pipes can be divided into flanges, butt welding, sockets, threads, ferrules, clamps and other connection types. Flange connections are further divided into flat welding, butt welding, sockets, threads and other types, and non-metallic pipes also have bonding connections. For pipe fittings and valves, the shapes are different due to different connection methods, and are divided into four connection types: flanges, butt welding, sockets, and threads.
6.1 Flange connection
Mainly used for the connection of pipes with equipment, valves and pipe fittings. For cast iron pipes and metal lined pipes, flange connections must be used due to manufacturing technology. Flanges also have different connection methods and different sealing types. 6.2 Butt-welding connection
6.2.1 Scope
Butt-welding connection type pipe fittings and valves are generally used for pipes of DN50 and above. 6.2.2 End bevel requirements
1 The bevel type and size of pipe welding joints shall comply with the provisions of HG20225 "Chemical Metal Pipe Engineering Construction and Acceptance Specifications".
2 The bevel of necked butt-welding flanges shall comply with the provisions of HG20605 and HG20606 "Steel Pipe Flanges, Gaskets, Fasteners".
3 The bevel and roughness of butt-welding pipe fittings shall comply with the provisions of GB/T12459 "Steel Butt-welding Seamless Pipe Fittings". 4 For the bevel of butt-welding valves, the standard type of "same pipe bevel" shall be requested when ordering. 5 If the engineering design adopts American standards, the size and processing of the bevel shall comply with the provisions of ASMEB16.25 "Butt-welding Ends".
Special types of grooves must be illustrated in drawings. 6.3 Socket connection
6.3.1 Scope
Usually used for pipes of DN40 and below. 115
6.3.2 Requirements for socket ends
1 The socket ends are flat.
2 When installing the socket ends, the pipe should be inserted into the bottom of the socket of the pipe fitting first, and then the pipe should be pulled out a little to make a 2mm gap at the socket, and then welded. 3Except where otherwise noted, the roughness of the remaining machined surfaces is 6:3/. 4The requirements for the socket ends shall comply with HG/T21634 "Forged Steel Socket Welding Pipe Fittings". 5If the engineering design adopts American standards, it shall comply with the provisions of ASMEB16.11 "Socket Welding and Threaded Forged Steel Pipe Fittings".
6.4 Threaded connection
6.4.1 Scope
Threaded pipe fittings are usually used for nominal diameters less than DN50. The design temperature of the taper pipe thread sealed joint should not be greater than 200℃. For non-flammable and non-toxic fluids, when the nominal diameter is 32-50mm, the design pressure should not be greater than 4MPa; when the nominal diameter is 25mm, the design pressure should not be greater than 8MPa; when the nominal diameter is less than or equal to 20mm, the design pressure should not be greater than 10MPa. Sealing welding should be used for pressures higher than the above. 6.4.2 Thread standard
my country's GB/T12716 "60° tapered pipe thread" standard is equivalent to the NPT part of the American standard "Pipe Threads General Purpose (INCH)\" ANSI/ASME B1.20.1. For cast iron pipe fittings and galvanized pipe fittings, the taper pipe thread of the GB7306 "Pipe thread sealed with thread" standard is used, and its tooth angle is 55°. The angles and pitches of these two threads are different and cannot be matched with each other. Requirements for threads should be put forward during design and procurement. 6.4.3 Due to the different angles and pitches of tapered pipe threads, attention must be paid when selecting connections for equipment and machinery in different countries.
6.4.4 The thread tolerance shall be in accordance with the selected standard. 6.4.5 The processed thread must be concentric with the pipe axis. 6.5 Ferrule connection
Generally used for pipes with an outer diameter of less than or equal to 25mm, suitable for steam tracing pipes, leak detection pipes and instrument control systems. 116
6.6 Clamp connection
Used to insert metal pipes into non-metallic pipes, and tighten them with metal hoops at the sockets. Applicable to public material stations, clean pipes that need to be temporarily and frequently disassembled and cleaned, with O-rings between pipes and metal hoops tightened on the outside of the flanges. 117
7.1.1 Principles
7 Selection of Common Components
7.1 General Requirements
According to the design conditions proposed by the process system professionals, according to the design temperature, design pressure and fluid properties of the conveyed fluid, and to meet the working conditions during the start-up such as pressure testing, purging, and trial running, economical and safe balance should be made, and cheap materials should be selected comprehensively to save investment, especially when expensive materials are used, technical and economic comparisons should be made. 7.1.2 Material Standards
Pipes and components and their materials should be selected in accordance with the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. Nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
Nominal diameter is the nominal diameter of the pipe.
British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Wall thickness series representation methods
There are two ways to express wall thickness
1) Use pipe schedule (Sch) to express wall thickness;www.bzxz.net
2) Use millimeters (mm) to express wall thickness, that is, pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be based on the operating conditions proposed by the process system professionals, and after calculation by the pipeline machinery professionals: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professionals shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For welded pipe types, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, pipes of the Ia series outer diameter and various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of the relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and the temperature-pressure level is determined according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.1 Flange connection
Mainly used for the connection between pipes and equipment, valves and pipe fittings. For cast iron pipes and metal lined pipes, flange connection is necessary due to manufacturing technology. Flanges also have different connection methods and different sealing types. 6.2 Butt welding connection
6.2.1 Scope
Butt welding type pipe fittings and valves are generally used for pipes of DN50 and above. 6.2.2 End groove requirements
1 The groove type and size of pipe welding joints shall comply with the provisions of HG20225 "Chemical Metal Pipe Engineering Construction and Acceptance Specifications".
2 The groove of neck butt welding flange shall comply with the provisions of HG20605 and HG20606 "Steel Pipe Flanges, Gaskets, Fasteners".
3 The groove and roughness of butt welding pipe fittings shall comply with the provisions of GB/T12459 "Steel Butt Welding Seamless Pipe Fittings". 4 For the groove of the butt-welded valve, the standard type of "same as the pipe groove" shall be requested when placing an order. 5 If the engineering design adopts the American standard, the size and processing of the groove shall comply with the provisions of ASMEB16.25 "Butt-welded ends".
Special grooves must be illustrated with drawings. 6.3 Socket connection
6.3.1 Scope
Usually used for pipes of DN40 and below. 115
6.3.2 Requirements for socket ends
1 The socket end is flat.
2 When installing the socket end, the pipe should be inserted into the bottom of the socket of the pipe fitting first, and then the pipe should be pulled out a little to make a 2mm gap at the socket, and then welded. 3 Unless otherwise specified, the roughness of the remaining processed surfaces is 6:3/. 4 The requirements for the socket end shall comply with HG/T21634 "Forged Steel Socket Welding Pipe Fittings". 5 If the engineering design adopts American standards, it shall be in accordance with the provisions of ASMEB16.11 "Socket Welding and Threaded Forged Steel Pipe Fittings".
6.4 Threaded Connection
6.4.1 Scope
Threaded pipe fittings are usually used for nominal diameters less than DN50. The design temperature of the taper thread sealed joint should not be greater than 200℃. For non-flammable and non-toxic fluids, when the nominal diameter is 32-50mm, the design pressure should not be greater than 4MPa; when the nominal diameter is 25mm, the design pressure should not be greater than 8MPa; when the nominal diameter is less than or equal to 20mm, the design pressure should not be greater than 10MPa. Sealing welding should be used for pressures higher than the above. 6.4.2 Thread Standard
my country's GB/T12716 "60° Tapered Pipe Thread" standard is equivalent to the NPT part of the American standard "Pipe Threads General Purpose (INCH)\" ANSI/ASMEB1.20.1. For cast iron pipe fittings and galvanized pipe fittings, the taper pipe thread of GB7306 "Pipe Thread Sealed with Thread" standard is used, and its tooth angle is 55°. The angles and pitches of these two threads are different and cannot be matched with each other. Requirements for threads should be put forward during design and procurement. 6.4.3 Due to the different angles and pitches of taper pipe threads, attention must be paid when selecting connections for equipment and machinery in different countries.
6.4.4 The thread tolerance shall be in accordance with the selected standard. 6.4.5 The processed thread must be concentric with the pipe axis. 6.5 Ferrule connection
Generally used for pipes with an outer diameter of less than or equal to 25mm, suitable for steam accompanying pipes, leak detection pipes and instrument control systems. 116
6.6 Clamp connection
Used for inserting metal pipes into non-metallic pipes, and tightened with metal hoops at the socket. Applicable to public material stations, clean pipes that need to be temporarily and frequently disassembled and cleaned, with O-rings between pipes and metal hoops tightened on the outside of the flange. 117
7.1.1 Principles
7 Selection of Common Components
7.1 General Requirements
According to the design conditions proposed by the process system professionals, according to the design temperature, design pressure and fluid properties of the conveyed fluid, and to meet the working conditions during the start-up such as pressure testing, purging, and trial running, economical and safe balance should be made, and cheap materials should be selected comprehensively to save investment, especially when expensive materials are used, technical and economic comparisons should be made. 7.1.2 Material Standards
Pipes and components and their materials should be selected in accordance with the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. Nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
Nominal diameter is the nominal diameter of the pipe.
British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Wall thickness series representation methods
There are two ways to represent wall thickness
1) Use pipe schedule (Sch) to represent wall thickness;
2) Use millimeters (mm) to represent wall thickness, that is, pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be based on the operating conditions proposed by the process system professionals, and after calculation by the pipeline machinery professionals: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professionals shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For welded pipe types, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, the outer diameter of the pipe of the Ia series and the pipes of various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and to determine its temperature-pressure level according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.1 Flange connection
Mainly used for the connection between pipes and equipment, valves and pipe fittings. For cast iron pipes and metal lined pipes, flange connection is necessary due to manufacturing technology. Flanges also have different connection methods and different sealing types. 6.2 Butt welding connection
6.2.1 Scope
Butt welding type pipe fittings and valves are generally used for pipes of DN50 and above. 6.2.2 End groove requirements
1 The groove type and size of pipe welding joints shall comply with the provisions of HG20225 "Chemical Metal Pipe Engineering Construction and Acceptance Specifications".
2 The groove of neck butt welding flange shall comply with the provisions of HG20605 and HG20606 "Steel Pipe Flanges, Gaskets, Fasteners".
3 The groove and roughness of butt welding pipe fittings shall comply with the provisions of GB/T12459 "Steel Butt Welding Seamless Pipe Fittings". 4 For the groove of the butt-welded valve, the standard type of "same as the pipe groove" shall be requested when placing an order. 5 If the engineering design adopts the American standard, the size and processing of the groove shall comply with the provisions of ASMEB16.25 "Butt-welded ends".
Special grooves must be illustrated with drawings. 6.3 Socket connection
6.3.1 Scope
Usually used for pipes of DN40 and below. 115
6.3.2 Requirements for socket ends
1 The socket end is flat.
2 When installing the socket end, the pipe should be inserted into the bottom of the socket of the pipe fitting first, and then the pipe should be pulled out a little to make a 2mm gap at the socket, and then welded. 3 Unless otherwise specified, the roughness of the remaining processed surfaces is 6:3/. 4 The requirements for the socket end shall comply with HG/T21634 "Forged Steel Socket Welding Pipe Fittings". 5 If the engineering design adopts American standards, it shall be in accordance with the provisions of ASMEB16.11 "Socket Welding and Threaded Forged Steel Pipe Fittings".
6.4 Threaded Connection
6.4.1 Scope
Threaded pipe fittings are usually used for nominal diameters less than DN50. The design temperature of the taper thread sealed joint should not be greater than 200℃. For non-flammable and non-toxic fluids, when the nominal diameter is 32-50mm, the design pressure should not be greater than 4MPa; when the nominal diameter is 25mm, the design pressure should not be greater than 8MPa; when the nominal diameter is less than or equal to 20mm, the design pressure should not be greater than 10MPa. Sealing welding should be used for pressures higher than the above. 6.4.2 Thread Standard
my country's GB/T12716 "60° Tapered Pipe Thread" standard is equivalent to the NPT part of the American standard "Pipe Threads General Purpose (INCH)\" ANSI/ASMEB1.20.1. For cast iron pipe fittings and galvanized pipe fittings, the taper pipe thread of GB7306 "Pipe Thread Sealed with Thread" standard is used, and its tooth angle is 55°. The angles and pitches of these two threads are different and cannot be matched with each other. Requirements for threads should be put forward during design and procurement. 6.4.3 Due to the different angles and pitches of taper pipe threads, attention must be paid when selecting connections for equipment and machinery in different countries.
6.4.4 The thread tolerance shall be in accordance with the selected standard. 6.4.5 The processed thread must be concentric with the pipe axis. 6.5 Ferrule connection
Generally used for pipes with an outer diameter of less than or equal to 25mm, suitable for steam accompanying pipes, leak detection pipes and instrument control systems. 116
6.6 Clamp connection
Used for inserting metal pipes into non-metallic pipes, and tightened with metal hoops at the socket. Applicable to public material stations, clean pipes that need to be temporarily and frequently disassembled and cleaned, with O-rings between pipes and metal hoops tightened on the outside of the flange. 117
7.1.1 Principles
7 Selection of Common Components
7.1 General Requirements
According to the design conditions proposed by the process system professionals, according to the design temperature, design pressure and fluid properties of the conveyed fluid, and to meet the working conditions during the start-up such as pressure testing, purging, and trial running, economical and safe balance should be made, and cheap materials should be selected comprehensively to save investment, especially when expensive materials are used, technical and economic comparisons should be made. 7.1.2 Material Standards
Pipes and components and their materials should be selected in accordance with the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. Nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
Nominal diameter is the nominal diameter of the pipe.
British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Wall thickness series representation methods
There are two ways to represent wall thickness
1) Use pipe schedule (Sch) to represent wall thickness;
2) Use millimeters (mm) to represent wall thickness, that is, pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be based on the operating conditions proposed by the process system professionals, and after calculation by the pipeline machinery professionals: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professionals shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For welded pipe types, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, the outer diameter of the pipe of the Ia series and the pipes of various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and to determine its temperature-pressure level according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.2 Requirements for socket ends
1 The socket ends are flat.
2 When installing the socket ends, the pipe should be inserted into the bottom of the socket of the pipe fitting first, and then the pipe should be pulled out a little to make a 2mm gap at the socket, and then welded. 3 Unless otherwise specified, the roughness of the remaining machined surfaces is 6:3/. 4 Requirements for socket ends shall comply with HG/T21634 "Forged Steel Socket Welding Pipe Fittings". 5 If the engineering design adopts American standards, it shall comply with the provisions of ASMEB16.11 "Socket Welding and Threaded Forged Steel Pipe Fittings".
6.4 Threaded connection
6.4.1 Scope
Threaded pipe fittings are usually used for nominal diameters less than DN50. The design temperature of the joint sealed by the tapered pipe thread should not be greater than 200℃. For non-flammable and non-toxic fluids, when the nominal diameter is 32-50mm, the design pressure should not be greater than 4MPa; when the nominal diameter is 25mm, the design pressure should not be greater than 8MPa; when the nominal diameter is less than or equal to 20mm, the design pressure should not be greater than 10MPa. Sealing welding should be used for pressures higher than the above. 6.4.2 Thread standard
my country's GB/T12716 "60° tapered pipe thread" standard is equivalent to the NPT part of the American standard "Pipe Threads General Purpose (INCH)\" ANSI/ASMEB1.20.1. For cast iron pipe fittings and galvanized pipe fittings, the tapered pipe thread of the GB7306 "Pipe thread sealed with thread" standard is used, and its tooth angle is 55°. The angles and pitches of these two threads are different and cannot be matched with each other. Requirements for threads should be put forward during design and procurement. 6.4.3 Due to the different angles and pitches of tapered pipe threads, attention must be paid when selecting connections for equipment and machinery in different countries.
6.4.4 The thread tolerance shall be in accordance with the selected standard. 6.4.5 The processed thread must be concentric with the pipe axis. 6.5 Ferrule connection
Generally used for pipes with an outer diameter of less than or equal to 25mm, suitable for steam tracing pipes, leak detection pipes and instrument control systems. 116
6.6 Clamp connection
Used to insert metal pipes into non-metallic pipes, and tighten them with metal hoops at the sockets. Applicable to public material stations, clean pipes that need to be temporarily and frequently disassembled and cleaned, with O-rings between pipes and metal hoops tightened on the outside of the flanges. 117
7.1.1 Principles
7 Selection of Common Components
7.1 General Requirements
According to the design conditions proposed by the process system professionals, according to the design temperature, design pressure and fluid properties of the conveyed fluid, and to meet the working conditions during the start-up such as pressure testing, purging, and trial running, economical and safe balance should be made, and cheap materials should be selected comprehensively to save investment, especially when expensive materials are used, technical and economic comparisons should be made. 7.1.2 Material Standards
Pipes and components and their materials should be selected in accordance with the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. Nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
Nominal diameter is the nominal diameter of the pipe.
British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Wall thickness series representation methods
There are two ways to express wall thickness
1) Use pipe schedule (Sch) to express wall thickness;
2) Use millimeters (mm) to express wall thickness, that is, pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be based on the operating conditions proposed by the process system professionals, and after calculation by the pipeline machinery professionals: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professionals shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For welded pipe types, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, pipes of the Ia series outer diameter and various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of the relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and the temperature-pressure level is determined according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.2 Requirements for socket ends
1 The socket ends are flat.
2 When installing the socket ends, the pipe should be inserted to the bottom of the socket of the pipe fitting first, and then the pipe should be pulled out a little to make a 2mm gap at the socket, and then welded. 3 Unless otherwise specified, the roughness of the remaining machined surfaces is 6:3/. 4 Requirements for socket ends shall comply with HG/T21634 "Forged Steel Socket Welding Pipe Fittings". 5 If the engineering design adopts American standards, it shall comply with the provisions of ASMEB16.11 "Socket Welding and Threaded Forged Steel Pipe Fittings".
6.4 Threaded connection
6.4.1 Scope
Threaded pipe fittings are usually used for nominal diameters less than DN50. The design temperature of the joint sealed by the tapered pipe thread should not be greater than 200℃. For non-flammable and non-toxic fluids, when the nominal diameter is 32-50mm, the design pressure should not be greater than 4MPa; when the nominal diameter is 25mm, the design pressure should not be greater than 8MPa; when the nominal diameter is less than or equal to 20mm, the design pressure should not be greater than 10MPa. Sealing welding should be used for pressures higher than the above. 6.4.2 Thread standard
my country's GB/T12716 "60° tapered pipe thread" standard is equivalent to the NPT part of the American standard "Pipe Threads General Purpose (INCH)\" ANSI/ASMEB1.20.1. For cast iron pipe fittings and galvanized pipe fittings, the tapered pipe thread of the GB7306 "Pipe thread sealed with thread" standard is used, and its tooth angle is 55°. The angles and pitches of these two threads are different and cannot be matched with each other. Requirements for threads should be put forward during design and procurement. 6.4.3 Due to the different angles and pitches of tapered pipe threads, attention must be paid when selecting connections for equipment and machinery in different countries.
6.4.4 The thread tolerance shall be in accordance with the selected standard. 6.4.5 The processed thread must be concentric with the pipe axis. 6.5 Ferrule connection
Generally used for pipes with an outer diameter of less than or equal to 25mm, suitable for steam tracing pipes, leak detection pipes and instrument control systems. 116
6.6 Clamp connection
Used to insert metal pipes into non-metallic pipes, and tighten them with metal hoops at the sockets. Applicable to public material stations, clean pipes that need to be temporarily and frequently disassembled and cleaned, with O-rings between pipes and metal hoops tightened on the outside of the flanges. 117
7.1.1 Principles
7 Selection of Common Components
7.1 General Requirements
According to the design conditions proposed by the process system professionals, according to the design temperature, design pressure and fluid properties of the conveyed fluid, and to meet the working conditions during the start-up such as pressure testing, purging, and trial running, economical and safe balance should be made, and cheap materials should be selected comprehensively to save investment, especially when expensive materials are used, technical and economic comparisons should be made. 7.1.2 Material Standards
Pipes and components and their materials should be selected in accordance with the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. Nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
Nominal diameter is the nominal diameter of the pipe.
British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Wall thickness series representation methods
There are two ways to represent wall thickness
1) Use pipe schedule (Sch) to represent wall thickness;
2) Use millimeters (mm) to represent wall thickness, that is, pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be based on the operating conditions proposed by the process system professionals, and after calculation by the pipeline machinery professionals: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professionals shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For welded pipe types, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, the outer diameter of the pipe of the Ia series and the pipes of various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and to determine its temperature-pressure level according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.2 Material standards
Pipes and components and their materials should be selected according to the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. The nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
The nominal diameter is the nominal diameter of the pipe.
The British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Methods of expressing wall thickness series
There are two methods of expressing wall thickness
1) Expressing wall thickness by pipe schedule number (Sch);
2) Expressing wall thickness by millimeters (mm), i.e., pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be made by the process system professional who proposes operating conditions, and after calculation by the pipeline machinery professional: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professional shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For the type of welded pipe, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, pipes of the Ia series outer diameter and various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of the relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and the temperature-pressure level is determined according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.2 Material standards
Pipes and components and their materials should be selected according to the latest national standards and industry standards issued by the state. For imported projects and foreign-related projects, it is recommended to use ANSI, ASME, API, ASTM, MSS and other standards or adopt relevant standards according to the contract provisions.
7.1.3 Temperature-pressure level
The wall thickness of pipes, pipe fittings, valves, flanges, etc. is calculated based on the allowable stress of the selected material. The nominal pressure usually refers to the highest non-impact working pressure at a specific temperature. The nominal pressure refers to the design given pressure related to the mechanical strength of the pipeline components. my country stipulates that the nominal pressure is represented by the code PN, and the nominal pressure unit is expressed in MPa. 7.2 Pipes
7.2.1 Determination of pipe diameter and wall thickness
1 Determination of pipe diameter
The nominal diameter is the nominal diameter of the pipe.
The British series dimensions are expressed in inches. Metric series dimensions are expressed in millimeters (mm). 2 Methods of expressing wall thickness series
There are two methods of expressing wall thickness
1) Expressing wall thickness by pipe schedule number (Sch);
2) Expressing wall thickness by millimeters (mm), i.e., pipe outer diameter × wall thickness. 3 Determination of pipe wall thickness
The determination of pipe wall thickness shall be made by the process system professional who proposes operating conditions, and after calculation by the pipeline machinery professional: 118
Submit the "Pipeline Wall Thickness Calculation Table", and the pipeline material control professional shall round and select the standard pipe wall thickness (except for the wall thickness of special material pipes).
For the type of welded pipe, the wall thickness calculation is selected, and the weld quality coefficient E is shown in Table 7.2.1. Table 7.2.1 Weld quality factor E
Methods and inspection requirements
100% nondestructive testing
Local nondestructive testing
No nondestructive testing
Resistance welding
Heating furnace welding
Spiral seam automatic welding
Single-sided butt welding
Double-sided butt welding
0.65 (no nondestructive testing) 0.85 (<100% eddy current testing) 0.60
0.80~0.85 (nondestructive testing)
Note: Nondestructive testing refers to the use of X-ray or ultrasonic testing. 7.2.2 Pipe selection
my country has compiled HG20553 "Series of seamless and welded steel pipe sizes for chemical piping". In engineering design, pipes of the Ia series outer diameter and various pipe schedules should be used first. For the commonly used pipe standards and scope of use, please refer to the provisions of the relevant standards. 7.2.3 Calculation of the theoretical weight of the pipe:
W=0.02466(Dt)t
D is the outer diameter of the pipe, mm
t is the wall thickness of the pipe, mm;
W is the weight of the pipe, kg/m.
7.3 Pipe fittings
The selection of pipe fittings is mainly based on the purpose: the occasion of use, etc. to determine the type of pipe fittings, and the temperature-pressure level is determined according to the design pressure and design temperature of the pipeline. The level of the pipe fitting is indicated by the nominal pressure or pipe gauge or wall thickness.
7.3.1 Long radius elbows with a bending radius of DN1.5 are preferred for elbows. Elbows with other bending radii can be selected in special cases.
7.3.2 Generally, butt-welded pipe fittings are used for pipes of DN50 and above. Socket fittings or threaded fittings are used for pipes of DN40 and below.
7.3.3 When a branch pipe is drawn from a main pipe: when the ratio of the branch pipe diameter to the main pipe diameter is greater than or equal to 0.5, a 119-diameter reducer is used.
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