GB/T 20801.2-2020Pressure piping code - Industrial piping - Part 2: Materials (English PDF)

3.1 Low temperature and low stress service

The working conditions, that need to meet the following conditions, at the same time.

3.2 Low temperature and lower stress service

The working conditions that need to meet the following conditions, at the same time.

3.3 Electric-resistance welded pipe; ERW

The pipe, which is continuously butt-welded, under the action of pressure, by the use of the pipe (coil) itself as the current loop, through electric resistance heating.

3.4 Electric-fusion welded pipe; EFW

The pipe, which is longitudinally butt-welded on the preformed blank, by the use of automatic arc welding or manual arc welding.

3.5 Plate welded pipe

An electrofusion welded pipe, is preformed from a flat plate into a tubular shape AND has one or two longitudinal straight welds.

3.6 Inspection certificate

A form of material quality certification (inspection document). It is an inspection document, which is indicated of the results, by the independently authorized departments or personnel outside the production department of the manufacturer, after inspection and test on the delivered products (or sampling), according to the provisions of the standard and contract.

4.1 Material selection

The owner or designer shall select appropriate materials for piping components, according to the specific use conditions (including manufacturing, fabrication and installation, media, operating conditions, working environment, testing, etc.)

AND the material use requirements and restrictions specified in this Part, considering the risk of material damage.

4.2 Material and technical requirements

4.2.1 Table A.1 and Table A.2 of Appendix A specify the designations, allowable

stress and application range of the piping component materials. The materials, which are used for the piping components, shall comply with the requirements of the material standards, as listed in Table A.1 and Table A.2.

4.2.2 In addition to the materials listed in Table A.1 and Table A.2, the following

materials can be used for piping components; however, they shall meet the requirements and use restrictions for corresponding materials in this Part.

4.2.3 Materials with unknown designations shall not be used for piping

components.

4.2.4 The recovered materials shall not be used in piping components.

4.2.5 The selection of other materials shall be subject to technical appraisal and

review & approval, by institutions with corresponding qualifications.

5.1 The materials, which are used for pressure components (except bolts), shall

have sufficient strength, plasticity, toughness. They shall have sufficient resistance to brittle fracture, at the lowest use temperature. When brittle materials, which have an elongation rate of less than 14%, are used, it shall take necessary safety protection measures.

5.2 The selected materials shall have sufficient stability, including chemical

properties, physical properties, corrosion and wear resistance, fatigue resistance, organizational stability.

5.3 When selecting materials, it shall consider the applicability of the materials

under possible open flames, fires and extinguishing conditions, as well as changes in material properties and secondary hazards, which are brought about by this.

5.4 The selected materials shall be suitable for the corresponding

manufacturing, production, installation, including welding, cold and hot processing, heat treatment requirements.

5.5 When several different materials are used in combination, it shall consider

the possible adverse effects.

5.6 Materials shall be available and economical.

6.1 Nodular cast iron, gray cast iron, malleable cast iron

6.1.1 Nodular cast iron

6.1.1.1 When nodular cast iron is used for piping components, its elongation

shall not be less than 15%; the use temperature shall not be higher than 350 °C, but it shall be higher than -20 °C. The use restrictions of nodular cast iron piping components, which are listed in Table 13 of GB/T 20801.3-2020, shall comply with the corresponding requirements of GB/T 13295.

6.1.1.2 Except for GC3 grade pipes, nodular cast iron shall meet the impact

performance requirements of GB/T 1348; the pressure rating shall not exceed

5.0 MPa.

6.1.2 Gray cast iron and malleable cast iron

6.1.2.1 When the gray cast iron and malleable cast iron, which are listed in

Table A.1, are used for piping components, they shall meet the following

requirements.

6.1.2.2 In addition to meeting the requirements of 6.1.2.1, the applicable

pressure-temperature ratings of gray cast iron and malleable cast iron pipes, fittings, pipe flanges, valves shall also meet the requirements of the corresponding standards, in Table 13 of GB/T 20801.3-2020.

6.2 Carbon structural steel

The restrictions on the use of carbon structural steel shall meet the following requirements.

6.3 Pipeline steel

6.3.1 Table A.1 includes carbon steel and pipeline steel pipes, butt-welded pipe

fittings, flange forgings for long-distance pipelines including GB/T 9711, as shown in Table 2.

6.3.2 The product specification level (PSL) of pipeline steel shall meet the

following requirements.

6.3.3 The minimum use temperature of PSL1 carbon steel, which is listed in

6.4 Pipes and butt-welded pipe fittings

6.5 Carbon steel and chromium-molybdenum alloy steel

6.6 Austenitic stainless steel

6.7 Plate-welded pipe

6.7.1 Plate-welded pipes shall be formed by longitudinal coils of steel plates, which have one or two longitudinal straight welds. Limited by the width of the steel plate, plate-welded pipes of larger diameter can be formed by lateral rolling the steel plates.

6.8 Aluminum and aluminum alloy

6.8.1 The mechanical properties of aluminum and aluminum alloys are related

to thickness and delivery status. The properties and allowable stresses, which are listed in Table A.1, are only applicable to the specified range of the corresponding standards.

6.8.2 If the material standard does not specify the tensile and yield strength, this Part requires supplementation in the purchase contract.

6.8.3 The welding structure of the material, in the work-hardened state, shall

adopt the allowable stress of the corresponding designation in the annealing state; the welding structure of the material, in the precipitation hardened state, shall adopt the allowable stress of the corresponding designation in the welding state.

6.9 Nickel and nickel alloys

6.9.1 The mechanical properties of nickel and nickel alloys are related to the

processing and heat treatment conditions. The properties and allowable stresses, which are listed in Table A.1, are only applicable to the specified range of the corresponding standards.

6.10 Pipe support material

6.10.1 The standards, materials, allowable stresses, which are listed in Table

A.1 and Table A.2, also apply to pipe supports.

6.10.2 The other requirements of the pipe support material shall be in

accordance with the provisions of Chapter 8 of GB/T 20801.3-2020.

6.11 Low melting point metals

7.1 Upper limit of material's use temperature

7.1.1 Table A.1 and Table A.2 specify the upper limit of the material's use

temperature, under normal circumstances.

7.1.2 When determining the upper limit of the use temperature of the material, it shall consider the influence of the medium and the environment.

7.2 Principles for the selection of high-temperature materials

7.2.1 General requirements

7.2.2 The use of carbon steel and chromium-molybdenum alloy steel

under high temperature conditions

7.2.2.1 The high-temperature strength reduction factor W of welded joints,

7.2.3 The use of stainless steel under high temperature conditions

7.2.3.1 Under the high-temperature creep conditions (see 3.2 of GB/T 20801.3-

2020), the high-temperature strength reduction factor W of stainless steel welded joints shall be in accordance with the provisions of 4.2.7 in GB/T 20801.3-2020.

7.2.4 Use of other materials under high temperature conditions

7.2.4.1 Titanium and titanium alloys should not be used at temperatures above 316 °C.

8.1 Minimum use temperature and exemption of impact test

8.1.1 General provisions (except for cast iron)

8.1.1.1 In addition to the provisions of exempting the impact test in 8.1.1.4, 8.1.3, 8.1.4, 8.1.5, 8.1.6, the material and its welded joints shall be subjected to an impact test.

8.1.1.2 The impact test of the material and its welded joints shall be carried out, in accordance with 8.2.

8.1.1.3 When determining the minimum design temperature, it shall consider

the fluid throttling effect and the influence of ambient temperature.

8.1.1.4 The carbon steel materials, which are used for GC3 grade pipelines, can be exempted from the impact test.

8.1.2 Cast iron

The minimum use temperature of nodular cast iron, gray cast iron, malleable cast iron shall meet the requirements of 6.1.

8.1.3 Carbon steel, low temperature steel, chromium-molybdenum alloy

steel, ferritic stainless steel, duplex stainless steel

8.1.3.1 The minimum use temperature and exemption conditions for impact test,

8.1.3.2 The welding procedure qualification of materials shall meet the

requirements of Table 8, Table 11, Table 12.

8.1.4 Austenitic stainless steel

8.1.4.1 The minimum use temperature of austenitic stainless steel shall meet

the requirements of Table A.1.

8.1.4.2 When the use temperature is lower than or equal to -20 °C, the

austenitic stainless steel shall be subjected to the low temperature impact test.

However, the low temperature impact test can be exempted, if the following requirements are met at the same time.

8.1.5 Nickel, nickel-based alloys, titanium alloys, aluminum alloys

The minimum use temperature of nickel, titanium, aluminum and its alloys shall meet the requirements of Table A.1; the conditions for exempting impact test shall meet the requirements of Table 7.

8.1.6 Bolt material

8.2 Impact test

8.2.1 Impact test of base metal

Except for the materials, which are exempted from the impact test in accordance with 8.1, the base metal shall be subjected to the impact test in accordance with the requirements of 8.2.3, 8.2.4, 8.2.5.

8.2.2 Impact test of welded joints

The impact test of welded joints shall meet the following requirements.

8.2.4 Impact test temperature

The impact test temperature shall meet the following requirements.

8.2.5 Qualification criteria

The qualification criteria of the impact test shall be determined, in accordance with the following relevant requirements.

9.1 Material marking

9.1.1 The marking of materials shall comply with the requirements of the

corresponding standards and contracts.

9.1.2 The content of the marking shall include at least the manufacturer's mark

and the name of the material (code). The marking of the following piping components shall also include the furnace batch number or code of the material.

a) Piping components for GC1 grade pipelines;

b) The piping components subjected to the impact test according to the requirements of this Part;

c) Chromium-molybdenum alloy steel (except bolt materials) piping components;

9.1.3 Materials shall be marked piece by piece. The markings shall be clear and

firm. Materials, which have a nominal diameter less than or equal to DN40, can be marked with labels or other alternative methods.

9.2 Quality certification

The quality certification of the material shall meet the following requirements.