GB/T 20801.4-2020 PDF English
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Pressure piping code - Industrial piping - Part 4: Fabrication and assembly
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| GB/T 20801.4-2006 | English | 150 |
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Pressure piping code -- Industrial piping -- Part 4: Fabrication and assembly
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GB/T 20801.4-2020: Pressure piping code - Industrial piping - Part 4: Fabrication and assembly---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT20801.4-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.040
J 74
Replacing GB/T 20801.4-2006
Pressure Piping Code - Industrial Piping - Part 4.
Fabrication and Assembly
Issued on. NOVEMBER 19, 2020
Implemented on. JUNE 1, 2021
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative References... 5
3 Terms and Definitions... 6
4 General Rules... 9
5 Inspection and Acceptance Inspection of Pipework Components and
Materials... 10
6 Fabrication of Piping... 13
7 Welding... 20
8 Preheating... 36
9 Heat Treatment... 39
10 Assembly and Erection... 49
11 Stainless Steel and Non-ferrous Metal Piping... 58
12 Piping Cleaning, Purging and Rinsing... 60
Appendix A (Informative) Evaluation Method for Misalignment of Piping at
Closure Point... 63
Appendix B (Informative) Flange Joint Bolt Tightening Method and Erection
Target Load... 71
1 Scope
This Part of GB/T 20801 specifies the basic requirements for the fabrication and
assembly of pressure piping. These basic requirements include regulations on
fabrication, welding, preheating, heat treatment, assembly, erection and piping
cleaning, etc.
This Part is applicable to the fabrication and assembly of pressure pipework
components defined in the scope of GB/T 20801.1.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 985.1 Recommended Joint Preparation for Gas Welding, Manual Metal Arc
Welding, Gas-shield Arc Welding and Beam Welding
GB/T 985.2 Recommended Joint Preparation for Submerged Arc Welding
GB/T 985.3 Recommended Joint Preparation for Gas-shield Arc Welding on Aluminum
and Its Alloys
GB/T 985.4 Recommended Joint Preparation for Welding on Clad Steels
GB/T 13927 Industrial Valves - Pressure Testing
GB/T 20801.1-2020 Pressure Piping Code - Industrial Piping - Part 1.General
GB/T 20801.2-2020 Pressure Piping Code - Industrial Piping - Part 2.Materials
GB/T 20801.3-2020 Pressure Piping Code - Industrial Piping - Part 3.Design and
Calculation
GB/T 20801.5-2020 Pressure Piping Code - Industrial Piping - Part 5.Inspection and
Testing
GB/T 20801.6-2020 Pressure Piping Code - Industrial Piping - Part 6.Safeguarding
GB 50236 Code for Construction of Field Equipment, Industrial Pipe Welding
Engineering
NB/T 47014 Welding Procedure Qualification for Pressure Equipment
TSG ZF001 Safety Technical Supervision Regulation for Safety Valves
TSG Z6002 Examination Rules for Welding Operators of Special Equipment
3 Terms and Definitions
What is defined in GB/T 20801.1-2020, GB/T 20801.2-2020, GB/T 20801.3-2020,
GB/T 20801.5-2020 and GB/T 50801.6-2020, and the following terms and definitions
are applicable to this document.
3.1 Manufacture
Manufacture refers to the manufacturing process of pipes, piping components or pipe-
supporting elements, etc.
3.2 Fabrication
Fabrication refers to the preparation work before piping erection.
3.3 Assembly
Assembly refers to the process of connecting two or more piping components
(including piping pre-fabrication) with bolts, welding, bonding, threading, brazing,
soldering or using sealing elements in accordance with the provisions of the design
documents.
3.4 Erection
Erection refers to the process of completely fixing a piping system on a designated
position and support in accordance with the provisions of the design documents.
3.5 Isometric Diagram
Isometric diagram refers to the drawing of each piping into an isometric drawing of
piping represented by single lines in accordance with the drawing method of
axonometric projection.
3.6 Hot Bending
Hot bending refers to the process of fabricating bent pipes when the temperature is
higher than the metal critical point AC1.
4 General Rules
4.1 The organization manufacturing, fabricating and erecting the piping shall have an
administrative license that complies with the requirements of relevant laws and
regulations for pressure piping safety supervision. The organization fabricating and
erecting the piping shall establish a corresponding quality assurance system and
comply with the following stipulations.
4.2 The fabrication and erection of the piping shall be carried out in accordance with
the design documents and the stipulations of this Part. When it is necessary to modify
the design documents and substitute engineering materials, it shall be approved by the
original design organization, and a written document shall also be issued.
4.3 The organization fabricating and erecting the piping should adopt a piping welding
information management system, and timely input and save the relevant data of
pipework components, welding, heat treatment, inspection and testing, etc.
5 Inspection and Acceptance Inspection of Pipework
Components and Materials
5.1 Material Marking and Acceptance of Quality Certification Documents
The marking and quality certification documents of pipework components and
materials shall receive the acceptance inspection in accordance with the design
documents and the stipulations of 9.1 and 9.2 in GB/T 20801.2-2020.In addition, they
shall also satisfy the following requirements.
5.2 Appearance Inspection
The pipework components and materials shall be checked for their materials,
specifications, models and quantities in accordance with the stipulations of the design
documents and product standards. In addition, the inspection and acceptance
inspection of appearance quality and geometric dimensions shall be carried out one
by one. The results shall comply with the stipulations of the design documents and the
corresponding product standards.
5.3 Material Inspection
For piping components made of chromium-molybdenum alloy steel, nickel-containing
low-temperature steel, stainless steel, nickel and nickel alloy, titanium and titanium
alloy materials, before use, positive material identification (PMI) or other methods shall
be adopted to check the contents of main alloy elements. The quantity shall satisfy the
following requirements.
5.4 Valve Pressure Test
5.5 Other Inspections
When the design documents put forward other inspection and acceptance inspection
requirements (such as. non-destructive testing and hardness inspection, etc.) for the
pipework components and materials, they shall be satisfied. The inspection methods,
quantities and inspection results shall comply with the stipulations of the design
documents and the relevant standards.
5.6 Disposal of Non-Conforming Products
5.7 Material Storage
During the fabrication and erection process, the pipework components and materials
shall be properly kept, and shall not be mixed or damaged. During the storage,
stainless steel and non-ferrous metal pipework components and materials shall not
come into contact with carbon steel or low-alloy steel. The orifices of the pipes, valves
and fittings that are not temporarily installed shall be closed.
6 Fabrication of Piping
6.1 Cutting and Joint Processing
6.1.1 The cutting processing of the pipework components and materials may adopt the
method of cold cutting or hot cutting. If the method of hot cutting is used, after cutting,
the method of mechanical processing or polishing shall be used to eliminate the
surface slag and the surface layer that affects the quality of piping welding.
6.1.2 Carbon steel and carbon-manganese steel may adopt the method of mechanical
processing or flame cutting to cut and prepare the joints. Low-temperature nickel steel
and alloy steel should adopt the method of mechanical processing to cut and prepare
the joints.
6.2 Mark Transference
6.2.1 During the fabrication of the piping components, the original marks of the
materials shall be verified and kept as much as possible. When it is impossible to keep
the original marks, the method of transference shall be adopted to re-mark the
materials. The material marking may also adopt the uniform engineering codes or color
codes of the piping components.
6.2.2 The use of marking method shall be based on the principle of not causing
damage or contamination to the materials. Hard-printed markings shall not be used for
low-temperature steel, stainless steel and non-ferrous metals. When austenitic
stainless steel and non-ferrous metal materials are marked with color codes, the
printing color shall not contain substances that may cause damage to the materials,
such as. sulfur, lead and chlorine, etc.
6.2.3 If other marking methods other than hard printing or engraving are adopted, the
fabricator shall ensure that there is no mixture of different materials, for example,
through the method of separate processing (time and location) or distinguishing color strips.
6.3 Bent Pipes
6.3.1 When fabricating bent pipes, appropriate bending techniques and equipment
shall be adopted in accordance with the properties of the pipe material, the working
conditions of the conveying fluid and the bending radius of the pipes.
6.3.2 The fabrication of bent pipes may adopt two methods. hot bending and cold
bending.
6.4 Plate Welded Pipes
6.4.1 The fabrication of the plate welded pipes shall comply with the stipulations of the
design documents and the product standards.
6.4.2 When fabricating and erecting plate welded pipes with a nominal diameter not
less than 400 mm, they shall comply with the following stipulations.
6.5 Miter Elbows
7 Welding
7.1 Welding Procedure Qualification and Welding Performance Qualification
7.1.1 The welding of piping pressure-bearing parts and pressure-bearing parts, as well
as the welding of pressure-bearing parts and non-pressure-bearing parts, shall adopt
qualified welding procedures and be welded by qualified welders.
7.1.2 The welding procedure qualification shall comply with the stipulations of NB/T
47014.The impact test requirements shall comply with the stipulations of 8.2 in GB/T 20801.2-2020.
7.1.3 When the materials required for the welding procedure qualification cannot
satisfy the stipulations of 7.1.2, with the consent of the designer and the proprietor, it
is allowed to use the mode of technical review of the pre-welding procedure
specification to replace the welding procedure qualification, but the following conditions
shall be satisfied at the same time.
7.2 Welding Materials
7.2.1 The welding materials shall comply with the stipulations of the design documents
and the relevant standards, and pass the welding procedure qualification verification.
When there is no stipulation in the design, the selection of welding materials shall be
comprehensively determined in accordance with the chemical composition,
mechanical properties, welding performance, pre-weld preheating, post-weld heat
treatment, service conditions and on-site construction conditions of the base material,
and comply with the following stipulations.
7.3.4 When welding in rainy and snowy days, effective protective measures shall be
taken, otherwise, welding shall be prohibited.
7.4 Preparation before Welding
7.4.1 Preparation of joints
7.4.2 Cleaning
7.4.2.1 For weldment joints, and the internal and external surfaces, before welding,
paint, oil stains, rust spots, slag, oxide scale and other detrimental substances shall be
removed.
7.4.3 Assembly
7.4.3.1 The assembly of butt joints shall comply with the following stipulations.
7.7 Fillet Weld
7.7.1 The fillet welds (including socket welds) may be concave and convex, and the
weld size shall comply with the stipulations of Figure 7.
7.7.2 The fillet welds of flat welded flanges or socket welded flanges shall comply with
the stipulations of Figure 8.The minimum weld size of other socket welded joints shall
comply with the stipulations of Figure 9.
7.8 Welded Connection of Branch Pipes
7.8.1 The welded connection between the branch pipe and the main pipe shall comply
with the stipulations of weld form and weld size of the branch pipe connection shown
in Figure 10.
7.8.2 The joints of the placed welded branch pipes or the plug-in welded branch pipes,
including the integrally reinforced branch pipe seats, shall be fully welded; the
thickness of the fillet weld of the cover surface shall be not less than the effective
thickness of the fillet weld [see Figure 10a) and Figure 10b)].
7.8.3 The welding of the reinforcement ring or the saddle-shaped reinforcement shall
comply with the following stipulations.
7.8.7 The branch pipe seat and the main pipe shall be fully welded; the thickness of
the fillet weld of the cover surface shall be not less than the effective thickness tc of the
fillet weld [see Figure 10g)]. The fillet weld of the cover surface shall smoothly transit
to the main pipe.
7.9 Welding of Attachments
7.10 Seal Welding
Seal welding shall be performed by qualified welders. The sealing weld shall cover all
exposed threads.
7.11 Weld Repair
8 Preheating
8.1 General Rules
8.1.1 The preheating requirements specified in this Chapter apply to all types of piping
welding, including tack welding, repair welding and seal welding of threaded joints.
8.1.2 The preheating temperature and other requirements shall be specified in the
welding procedure specification or the design documents, and verified by the welding
procedure qualification.
8.1.3 When the method of thermal processing is used for the cutting, joint-opening,
root cleaning, grooving or temporary welding of welds, the preheating requirements
shall also be considered.
8.2 Preheating Temperature
8.2.1 The preheating temperature shall comply with the requirements of the design
documents. When there is no such stipulation in the design documents, the minimum
preheating temperature of the various materials shall comply with the stipulations of Table 6.
8.2.2 During the welding of materials with different requirements for the preheating
temperature, the higher preheating temperature in Table 6 shall be selected.
8.2.3 For multi-layer (pass) weldments that require preheating, the interpass
temperature shall be not lower than the preheating temperature, but shall comply with
the following requirements.
8.2.4 The base material temperature of tack weld shall be not lower than the minimum
preheating temperature specified in Table 6; the preheating range shall be no less than
25 mm from the two ends of the tack weld.
8.2.5 For repair welding, the preheating temperature shall be appropriately higher than
that of the original weld.
8.3 Measurement of Preheating Temperature
8.4 Welding Interruption
8.4.1 When the welding is interrupted, the cooling rate shall be controlled, or other
measures shall be taken to prevent it from adversely affecting the piping.
8.4.2 Before the welding is resumed, the interrupted weld shall be cleaned, inspected
and confirmed. In addition, in accordance with the stipulations of the welding procedure
specification, preheating shall be re-performed.
9 Heat Treatment
9.1 General Rules
9.1.1 This Chapter specifies the basic requirements for the welding, bending and post-
forming heat treatment of pressure piping.
9.1.3 This Part does not restrict the use of lower or even exempt heat treatment
requirements, but it shall comply with the requirements of 9.7.
9.2 Heat Treatment after Bending and Forming
9.6 Hardness Inspection
9.6.1 For welded joints, and piping components processed through bending and
forming that require post weld heat treatment, after the heat treatment, the hardness
value shall be determined. The hardness determination area of welded joints shall
include welds and heat-affected zone. The determination area of the heat-affected
zone shall be close to the fusion line.
9.6.2 For each heat treatment in the furnace, at least 10% shall be spot-checked for
the determination of the hardness value. For partial heat treatment, 100% shall be
tested for the hardness value.
9.6.3 Unless it is otherwise specified in the design, the hardness values of welded
joints and piping components processed through bending and forming after heat
treatment shall comply with the following stipulations.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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