Inspection procedures of pipe fittings arrival

1. General

In order to standardize the inspection and acceptance of pressure pipelines and pipe fittings upon arrival, and ensure the quality of pressure pipeline installation and use, this regulation is specially formulated.
This regulation is applicable to pressure pipeline projects undertaken by the company.
The arrival inspection of pipes and pipe fittings should not only comply with this regulation, but also comply with the technical requirements of current national standards, specifications, and design drawings.

2. Compilation basis

• GB50235-97: Code for Construction and Acceptance of Industrial Metal Pipeline Engineering
• HG20225-95: Code for Construction and Acceptance of Chemical Metal Pipeline Engineering
• SH3501-2002: Code for Construction and Acceptance of Highly Toxic and Combustible Medium Pipeline Engineering in Petrochemical Industry
• SH/T3517-2001: Process Standards for Petrochemical Steel Pipeline Construction Engineering
• DL/T5031-94: Technical Specification for Construction and Acceptance of Electric Power Construction (Pipeline Section)
• GB50369-2006: Code for Construction and Acceptance of Oil and Gas Long Distance Pipeline Engineering
• SY/T0466-97: Code for Construction and Acceptance of Natural Gas Gathering and Transportation Pipelines
• SY0460-2000: Code for Construction and Acceptance of Natural Gas Purification Equipment and Pipeline Installation Engineering
• SY0470-2000: Code for Construction and Acceptance of Oil and Gas Pipeline Crossing Engineering
• SY0402-2000: Code for Construction and Acceptance of Process Pipeline Engineering in Petroleum and Natural Gas Stations
• SY/T0422-97: Code for Construction and Acceptance of Oilfield Gathering and Transportation Pipelines
• CJJ28-2004: Code for Construction and Acceptance of Urban Heating Pipeline Network Engineering
• CJJ33-2005: Code for Construction and Acceptance of Urban Gas Transmission and Distribution Engineering
• CJJ63-2008: Technical Specification for Polyethylene Gas Pipeline Engineering

3. Inspection Procedure

Inspection of product quality certificate → Inspection of factory mark → Appearance inspection → Verification of specifications and materials → Material re-inspection → Non destructive inspection and testing → Identification → Warehousing and storage

Note: Material re-inspection is only carried out under the following conditions:

• ① Alloy steel pipes and fittings;
• ② If it is found that the quality certificate does not match the steel grade identification of the received material or there is no steel grade on the label;
• ③ The data in the certificate of conformity is incomplete or questionable.

4. Inspection requirements for pipes, fittings, and valves upon arrival

4.1 General regulations

4.1.1 General provisions

• Steel pipes, fittings, and valves should be ordered according to the model, specifications, and technical parameters specified in the design. If changes are required, technical visas must be obtained from the design unit and visa procedures must be promptly processed with the construction unit or engineering supervisor.
• When steel pipes, pipe fittings, and valves arrive, they should be inspected and accepted according to the supply contract and factory quality certificate, and should be labeled and properly stored.
• Steel pipes, pipe fittings, and valves must have a quality certificate from the manufacturer, and their quality requirements must not be lower than the current national standards.
• Steel pipes, fittings, and valves should undergo visual inspection before use, and those that do not meet the standards should not be used.
• The design documents require materials to undergo low-temperature impact toughness testing, and the supplier shall provide a document of the low-temperature impact toughness test results, with indicators not lower than those specified in the design documents.
• The design documents require stainless steel pipes and fittings to undergo intergranular corrosion testing. The supplier shall provide a document of the results of the intergranular corrosion test, with indicators not lower than those specified in the design documents.

4.1.2 Inspection of steel pipes
Steel pipes (including rolled tube plates) must have a product quality certificate, which generally indicates: supplier name (or factory logo), buyer name, delivery date, contract number, standard number, steel number, furnace number, batch number, delivery status, weight and quantity, variety name, size, level, various test results (including reference indicators) specified in the standard, and the seal of the technical supervision department.
Steel pipe markings should meet the following requirements:

• 1) Each steel pipe with an outer diameter greater than or equal to 36mm should be marked. The marking should generally include steel number, product specification, product standard, and supplier’s stamp, etc. Alloy steel pipes should also have furnace number and batch number;
• 2) Each bundle (or box) of bundled or boxed steel pipes should have a label, which should indicate the supplier’s trademark (or seal), steel number, furnace number, batch number, contract number, product standard number, weight, number of pieces, manufacturing date, and technical supervision department seal.

4.1.3 Inspection of pipe fittings
The flange sealing surface should be smooth and clean, without radial grooves, and without pores, cracks, burrs, or other defects that reduce strength and connection reliability.
Flanges with male & female faces or male & female rings should naturally fit, and the height of the boss should not be less than the depth of the groove.
The supporting part of the bolts connected to the flange end face should be parallel to the flange joint surface to ensure uniform force on the end face during flange connection.
The threads of bolts and nuts should be complete and free from defects such as scratches and burrs. The bolts and nuts should fit well without looseness or jamming.
Asbestos rubber gaskets should have a flexible texture, no aging, deterioration, or layering, and the surface should not have defects such as folds or wrinkles.
The surface of the metal gasket should be visually inspected with a flat ruler and should be in good contact, free from defects such as cracks, burrs, rust, and rough machining. Its hardness should be lower than that of the flange.
The metal wrapped and spiral wound gaskets should not have defects such as radial scratches or looseness.
The working surface of the sliding bracket should be smooth, flexible, and free from jamming.
The appearance and geometric size inspection of pipeline support and hanger springs should meet the following requirements

• 1) The surface of the spring should not have defects such as cracks, folds, layering, rust, scratches, etc;
• 2) The deviation of spring size should meet the requirements of the drawing;
• 3) The deviation in the number of working coils of the spring should not exceed half a turn;
• 4) In the free state, the pitch of each coil of the spring should be uniform, and its deviation should not exceed ± 10% of the average pitch;
• 5) The supporting surfaces at both ends of the spring should be perpendicular to the spring axis, and the deviation Δ should not exceed 2 % of the free height ( as shown in Fig.1 ).

Figure.1 Schematic diagram of the deviation between the perpendicularity of the spring end face and the axis

The spring of pipeline supports and hangers should have factory certification. If the support and hanger springs lack factory certificates, the following tests should be conducted before installation:

• 1) Full compression deformation test: Compress until the spring coils come into contact with each other, and maintain for 5 minutes. After unloading the load, the permanent deformation should be at most 2% of the original height. If it exceeds, a second full compression should be performed. The total permanent deformation after two experiments should not exceed 3% of the original height. Those who do not meet the above requirements should not be used;
• 2) Working load compression test: Under the working load, the spring compression amount should meet the design requirements, and the allowable deviation is shown in Table 1.

Table.1 Allowable Deviation of Spring Compression

Effective circle number of spring	The allowable deviation of compression amount
2-4	±12%
5-10	±10%
>10	±8%

4.1.4 Inspection of valves

• Before installation, valves should undergo visual inspection and be free of defects such as cracks and sand holes. The sealing surfaces of the valve stem and flange should be flat and smooth, and the valve stem threads should be free of burrs or scars. If there is packing, it should be inspected, and the tightened gland bolts should have sufficient adjustment allowance. Valve testing should be carried out in accordance with the provisions of the “Specification for Inspection and Installation of Valves” SY/T 4102. When the working medium is water or steam, use water for the pressure test medium. When the working medium is oil and gas, kerosene should be used as the pressure testing medium.
• Valves that pass the test should be promptly drained of internal water and blown dry. Except for valves that require degreasing, the sealing surface should be coated with anti-rust oil, the valve should be closed, the inlet and outlet should be sealed, obvious markings should be made, and the “Valve Test Record” should be filled out.
• For valves with steam jackets, the jacket part should be subjected to a strength test at 1.5 times the working pressure or according to the product manual.
• The operating mechanism and transmission device of the valve should be inspected according to the design requirements, requiring flexible action and correct indication.
• When there are special requirements for inspection and pressure testing in the design documents or valve technical conditions, special requirements should be followed.

4.2 Inspection of long-distance pipelines, fittings, and valves upon arrival

The pipes used in the crossing project should comply with the provisions of GB/T 8163-99 “Seamless Steel Pipes for Fluid Transportation”, GB/T 9711.1/2/3 “Technical Conditions for Delivery of Steel Pipes for Petroleum and Natural Gas Industries”, and SY 5036 “Spiral Seam Submerged Arc Welding Steel Pipes for Pressure Containing Fluid Transportation”.
The steel pipes used in the crossing project should be sampled for mechanical properties and chemical composition re-inspection, and the results should comply with the provisions of Article 4.2.1 of this regulation. The sampling quantity should be 20% of the total number of steel pipes crossed, but at least one.
The re-inspection of high-pressure steel pipes for natural gas gathering and transportation should be carried out in accordance with the following regulations:

• All steel pipes should be numbered one by one and their hardness should be checked, and their hardness values should comply with the current national standards;
• One steel pipe with the highest and lowest hardness should be selected from each batch of steel pipes (6 samples should be prepared for each steel pipe, including 2 tensile samples, 2 impact samples, and 2 flattened or cold bent samples) for mechanical performance testing. The testing requirements should comply with the current national standards.

During the re-inspection of high-pressure steel pipes for natural gas gathering and transportation, if there are any unqualified items, a double inspection should be conducted. The re-inspection will only be conducted on items that still need to pass the original re-inspection. The rechecked samples were taken from the previously unqualified steel pipe and another steel pipe with the closest hardness to that steel pipe. When there are still unqualified items in the recheck results, the batch of steel pipes should be inspected one by one, and unqualified ones should not be used.
High-pressure steel pipes for natural gas gathering and transportation should have the manufacturer’s ultrasonic inspection certificate. If there is no inspection certificate from the manufacturer, ultrasonic testing should be carried out one by one. Ultrasonic testing should be carried out in accordance with the current JB1151 “Ultrasonic Testing of High-Pressure Seamless Steel Pipes”.
When repairable defects are found during the inspection of steel pipes, they should be gradually polished until the defects disappear. The actual wall thickness after removing defects should be at least 90% of the nominal wall thickness of the steel pipe, and should be at least the designed calculated wall thickness. Steel pipes with severe corrosion and delamination shall not be used.
The deviation between the outer diameter and wall thickness of steel pipes should comply with the current national standards.
The pipes and fittings used in natural gas gathering and transmission stations shall comply with the relevant provisions of SY/T 0599-2006 “Requirements for Metal Materials for Sulfide Stress Cracking Resistance of Natural Gas Ground Facilities”.
The technical requirements for high-pressure pipe fittings and fasteners used in natural gas gathering and transmission stations shall comply with the relevant provisions of JB/T 450-1992 “Technical Conditions for pN16.0-32.0MPa Forged Angle High-Pressure Valves, Pipe Fittings, and Fasteners”. The technical requirements for pipe fittings and fasteners with a nominal pressure less than 16MPa should comply with national or industry standards.
The quality of the elbow should meet the following requirements:

• The appearance of the elbow should not have defects such as cracks, layering, wrinkles, or excessive burning;
• The thickness reduction of the elbow wall should be less than 10% of the thickness, and the measured thickness should not be less than the designed calculated thickness;
• The ovality of the curved part should be less than 1% of the nominal diameter;
• The inclination deviation of the two ends of the elbow is less than 1% of the outer diameter of the steel pipe and not more than 1.5mm;
• The bending angle error of the elbow shall not exceed ± 1 °.

The elbows, cold bends, and elastic-laid pipe sections of the pipeline route shall comply with the provisions of Table 2.
Table.2 Regulations for Bend, Cold Bend and Elastic Laying Pipe Sections

Type		Curvature radius R	Appearance and main dimensions
Elbow		≥5D	No wrinkles, cracks, double skin, or mechanical damage; When the ellipticity is less than or equal to 2.0% and R is equal to 5D, the wall thickness reduction rate is less than or equal to 9.0%.
Cold Bend	D≤323.9mm	≥30D	No wrinkles, cracks, double skin, or mechanical damage; The ovality of the bend is less than or equal to 2.0%.
	D>323.9mm	≥40D
Elastic laying pipe section		≥1000D	No wrinkles, cracks, double skin, or mechanical damage; The ovality of the bend is less than or equal to 2.0%.

Note: D – Outer diameter of pipeline

The longitudinal welds of straight seam steel pipe hot bending elbows and bends should be located at position 450 of the inner arc of the elbow and bend. The deformation rate of any part of the pipe diameter should not exceed 4.9% of the nominal diameter of the pipe, and it should meet the size requirements for passing through the pig (ball). Each elbow and bend end should be marked with parameters such as bending angle, steel pipe outer diameter, wall thickness, curvature radius, and material model. Other requirements should comply with the provisions of Table.2.
It is strictly prohibited to use fold bends or shrimp waist bends in natural gas gathering and transportation pipelines.
The vertical deviation of welded or drawn tee branch pipes should not exceed 1% of their height and should not exceed 3mm. The allowable deviation of the vertical length of each end face shall not exceed 1% of the outer diameter of the steel pipe and shall not exceed 3mm.
 The centerline of both ends of the concentric reducer should overlap, and its eccentricity value (a1-a2)/2 should not be greater than 1% of the outer diameter of the large end and should not be greater than 5mm, as shown in Figure 2:

Figure.2 Concentric reducer
The pipe head should be elliptical or spherical, and its quality should comply with the following regulations:
The minimum wall thickness of the head should be at least 90% of the nominal wall thickness of the head and not less than the design wall thickness.
The allowable deviation for the roundness of the inner or outer diameter of the head should be ± 2mm, the allowable deviation for the height of the curved surface should be ± 4mm, and the allowable deviation for the height of the straight edge should be +5/-3mm; Use a 300mm long sample to check the surface roughness, and the gap should not exceed 2mm.
Flat cover heads should be used for pipelines with a design pressure less than 10MPa, and their thickness and structure should comply with the “Design Regulations for Steel Petrochemical Pressure Vessels” issued by China National Petroleum and Chemical Corporation.
When the wall thickness of elbows, reducers, and tees exceeds 3.5mm, a groove of 300-350 should be cut at the end and a blunt edge of 1-2mm should be left.
Standard flanges should comply with the current national standards, while non-standard flanges should comply with the following regulations:

• The allowable deviation of the center circle diameter of the bolt hole is ± 0.3mm;
• The allowable deviation of the center distance between bolt holes (calculated based on chord length) is ± 0.3mm for adjacent holes. When the nominal diameter of any two holes is less than or equal to 500mm, it is ± 1mm; When the nominal diameter is 600-1200mm, it is ± 1.5mm.

Insulated joints or flanges shall undergo hydraulic testing. The test pressure is 1.5 times the design pressure, and the stabilization time is 5 minutes. It is qualified if there is no leakage. After the pressure test, residual water should be wiped dry for insulation testing. The detection should be measured using a 500V megohmmeter, and its insulation resistance should be greater than 2M Ω.
Valves must have a product qualification certificate. High-pressure valves, electric valves, pneumatic valves, and gas-liquid linkage valves should have product user manuals.
Valves that are required to undergo low-temperature sealing tests in design should have a certificate of conformity from the manufacturer for low-temperature sealing tests.
Valve strength test, using clean water as the medium, with a test pressure of 1.5 times the nominal pressure and a pressure stabilization of not less than 5 minutes. If the shell and packing do not leak, the strength test is qualified. If there are austenitic stainless steel components inside the valve, the chloride ion content of the clean water used for the test should be less than 25 ppm.
Electric, hydraulic, and pneumatic ball valves, orifice valves, and parallel double gate valves should undergo necessary strength, sealing, and operational performance tests according to the requirements in the manual.
The driving device of hydraulic ball valves should be inspected according to the manufacturer’s instructions, and all components should be intact. The pressure oil should be at 2/3 of the oil mark, and the driving should be flexible.
The inspection of electric valves should meet the following requirements:

• The gearbox should be cleaned, the transmission gears should be free of rust and cracks, the meshing should be suitable, the motor should not be affected by moisture, the lubricating oil should be added sufficiently, and the transmission mechanical and electrical parts should be flexible and easy to use.
• Adjust the limit switch according to the manufacturer’s requirements and conduct a trial run if necessary.
• The cut-off valves of oil and gas pipelines should undergo visual inspection, valve startup inspection, and hydraulic test, and their requirements should comply with the provisions of Table 3.

Table.3 Inspection and Test Regulations for Block Valves

Project		Inspection and test content		Inspection standards
Visual inspection		Housing	Trachoma	No sand hole
			Crack	No cracks
		Auxiliary equipment		Complete and intact
		Anticorrosive coating for buried valves		Spark leakage detection: No leakage points
Opening and closing inspection		Opening and closing		Flexible
		Opening and closing indicator		Accuracy
Hydrostatic test	Shell strength test	1.5 times the maximum working pressure, stabilized for 5 minutes		No leakage
	Valve tightness test	1.1 times the maximum working pressure, stabilized for 2 minutes		No leakage

The number of strength and tightness test inspections for valves in natural gas gathering and transmission stations is generally carried out in the following proportions:

• Valves with a nominal diameter less than or equal to 50mm and a nominal pressure less than or equal to 1.6MPa should be sampled by 10% from each batch, with no less than 1 valve. If there are any unqualified valves, an additional 20% should be sampled. If there are still unqualified valves in the further sampling, each batch of valves should be tested one by one.
• All valves with a nominal diameter greater than 50mm or a nominal pressure greater than 1.6MPa should be tested.
• Various anti-corrosion materials, including primer, primer, patching and patching materials, should be subjected to spot checks for coating or coating according to relevant technical standards or design requirements before use. If the test fails, the number of samples should be doubled for spot checks. If it still fails, it should not be put into use.

4.3 Inspection of industrial pipelines, fittings, and valves upon arrival

When inspecting the appearance of steel pipes, their quality should meet the following requirements;
The surface shall be free from defects such as cracks, folds, folds, delamination, hair lines, and scars;
No defects such as rust, pitting, pits, and mechanical damage exceed the negative deviation of wall thickness.
Steel pipes for Class A or Class I pipelines should be sampled by 10%, and Class B or Class II pipelines should be sampled by 5%, with no less than one pipe, for outer diameter and wall thickness measurement. The allowable deviation of the size of carbon steel seamless steel pipes should comply with the provisions of GB/T 8163-99 “Seamless Steel Pipes for Fluid Transportation”. The allowable deviation of the size of stainless steel seamless steel pipes should comply with the provisions of GB/T 14976-2002 “Stainless Steel Seamless Steel Pipes for Fluid Transport”.
In SHA grade pipelines, for pipes with design pressure greater than or equal to 10MPa, the outer surface should be subjected to non-destructive testing one by one according to the following methods, and there should be no linear defects:

• Magnetic particle testing should be used for magnetic steel pipes with an outer diameter greater than 12mm;
• Nonmagnetic steel pipes should undergo penetration testing.

Surface defects found through magnetic particle or penetration testing of pipes are allowed to be ground, and the actual wall thickness after grinding should not be less than 90% of the nominal wall thickness of the pipe.
In SHA grade pipelines, for pipes transporting extremely hazardous media with a design pressure less than 10MPa, 5% and no less than one pipe should be sampled from each batch (referring to the same batch number, furnace number, material, and specification) for external surface magnetic particle or penetration testing, and there should be no linear defects. When the sampling inspection fails, double the sampling inspection. If there are still unqualified samples, the batch of pipelines shall not be used.
The quality certificate of pipes conveying highly toxic media should include ultrasonic testing results. Otherwise, supplementary tests should be conducted one by one according to the current GB/T 5777 “Ultrasonic Testing Methods for Seamless Steel Pipes”.
Alloy steel bolts and nuts used for pipelines with design pressure greater than or equal to 10MPa should undergo rapid spectral analysis one by one. Two pieces should be sampled from each batch for hardness inspection. If there are any unqualified pieces, double the sampling should be conducted. If there are still unqualified pieces, the bolts and nuts from that batch should not be used.
Alloy steel bolts and nuts for low-temperature pipelines with a design temperature lower than or equal to -29 ℃ should be inspected by rapid spectral analysis one by one, and two bolts from each batch should be selected for low-temperature impact performance testing. If there are any nonconformities, double the sampling inspection. If there are still nonconformities, the batch of bolts and nuts shall not be used.
For rapid spectral analysis of other alloy steel pipe components, 5% of each batch should be sampled and at least one piece should be inspected. If there are any nonconformities, double the sampling inspection. If there are still nonconformities, the batch of pipeline components shall not be used.
The valves of the following pipelines should undergo shell pressure tests and sealing tests one by one. Those who do not meet the standards shall not be used.

• Valves for pipelines transporting highly toxic, toxic, and flammable fluids;
• Valves for transporting noncombustible and non-toxic fluid pipelines with a design pressure greater than 1MPa or a design pressure less than or equal to 1MPa and a design temperature less than -29 ℃ or greater than 186 ℃.

Valves for transporting noncombustible and non-toxic fluid pipelines with a design pressure of less than or equal to 1MPa and a design temperature of -29 ℃ -186 ℃ should be sampled from 10% of each batch, and at least one valve should be tested for shell pressure and sealing. When unqualified, double sampling should be conducted. If still unqualified, the batch of valves should not be used.
The shell test pressure of the valve should be at least 1.5 times the nominal pressure, and the test time should be at least 5 minutes. It is qualified if there is no leakage of the shell filler. The sealing test should be conducted at nominal pressure, and it is qualified if the sealing surface of the valve disc is not leaking.
Gate valves with a nominal pressure less than 1MPa and a nominal diameter greater than or equal to 600mm may not undergo separate shell pressure tests and gate sealing tests. The shell pressure test can be conducted according to the test pressure of the pipeline system during the system pressure test. The sealing test of the gate can be inspected using methods such as color printing, and the color printing on the joint surface should be continuous.
For various types of valves, when the construction unit has contractual requirements or the manufacturer ensures product quality and provides product quality and usage guarantee, disassembly and tightness test inspection may not be carried out. Otherwise, the following valves must be disassembled and inspected before installation:

• Used for valves with a design temperature greater than or equal to 450 ℃;
• Safety and throttle valves;
• Valves that fail the tightness test.

Before disassembling the valve, the dirt and debris should be cleaned up. Otherwise, opening and closing operations and disassembly are not allowed. When disassembling and inspecting valves with special structures, the disassembly sequence specified by the manufacturer should be followed to prevent damage to components or affecting personal safety.
The disassembled valve should be inspected as follows:

• The internal parts of alloy steel valves should undergo spectral re examination (the components may not be marked, but the inspection results should be recorded);
• Whether the connection between the valve seat and the valve shell is firm and whether there is any looseness;
• Check if the joint surface between the valve core and valve seat matches and if there are any defects on the joint surface;
• Whether the connection between the valve stem and the valve core is flexible and reliable;
• Whether the valve stem is bent or corroded, whether the tightness between the valve stem and the packing gland is appropriate, and whether there are defects such as broken threads on the valve stem;
• Joint condition of valve cover flange surface;
• The opening and closing stroke and terminal position of the throttle valve should be checked, and markings should be made as much as possible.

After inspection and elimination of defects, the valve should meet the following requirements:

• The material of alloy steel components meets the design requirements;
• The assembly is correct, the action is flexible, and the opening indicator indicates correctly;
• The specifications and quality of all gaskets and fillers meet the technical requirements;
• The filler assembly is correct, and the interface must be cut into inclined openings, and the interfaces of each layer should be staggered from each other; After the packing is compressed, it should maintain sealing and not hinder the opening and closing of the valve stem.

Valves used in the oil system should be cleaned of their flow parts, removed from molding sand and paint, and replaced with oil resistant packing and gaskets.
When reassembling gate and globe valves after disassembly and inspection, the valve disc must be in the open position before tightening the valve cover screws.
After disassembling and reinstalling the valve, a tightness test should be conducted.
Safety valves should be debugged according to the opening pressure specified in the design documents. The pressure should be stable during pressure regulation, and the opening and closing tests of each safety valve should not be less than 3 times. After debugging, the “Initial Debugging Record of Safety Valve” should be filled out.

4.4 Inspection of public pipelines, fittings, and valves upon arrival

The equipment and pipeline components used in the gas transmission and distribution project should comply with the current national product standards and must have product qualification documents from the quality inspection department of the production plant.
For materials required to undergo low-temperature impact toughness test in the design documents, the supplier shall provide a document of the low-temperature impact toughness test results. Otherwise, the test shall be conducted in accordance with the requirements of the current national standard GB/T 229 “Metal Low Temperature Impact Test Method”, and its indicators shall not be lower than the lower limit of the specified value.
The quality of elbows, tees, and reducing joints of gas steel pipes should comply with the current national standard GB 12459 “Steel Butt Welded Seamless Pipe Fittings”.
The inspection of ductile iron pipes and fittings should meet the following requirements:

• The surface of pipes and fittings shall not have cracks or uneven defects that affect their use.
• When using rubber sealing rings for sealing, their performance must meet the requirements for the use of gas transmission media. The rubber ring should be smooth and have a clear contour, and there should be no defects that affect the sealing of the interface.
• The dimensional tolerance of pipes and fittings should comply with the current national standards GB 13295 “Centrifugal Cast Ductile Iron Pipes” and GB 13294 “Ductile Iron Fittings”.

Before connecting polyethylene and steel skeleton polyethylene composite pipelines, the specifications and pressure levels of the pipes and fittings to be connected should be checked. The surface of the pipes should be checked to ensure that there are no bumps or scratches, and the depth of the scratches should not exceed 10% of the wall thickness of the pipes.
Before installing the valve of the gas heating pipeline, the opening and flexibility of the valve core should be checked.
The inspection of valves used in the heating pipeline network before installation should comply with the following regulations:

• The valves used in the heating pipeline network project must have a product qualification certificate from the manufacturer.
• The valves used in the main line of the primary pipeline network and the valves directly connected to the main line of the primary pipeline network, as well as the valves and other important valves that serve as closing and protecting functions at the head end of the branch line and the inlet of the heating station, should be subjected to strength and tightness tests by a qualified testing department. They should be inspected and qualified, stored separately, positioned for use, and valve test records should be filled out.

The inspection of the compensator should check the following contents:

• The compensator used should comply with the relevant provisions of the current national standards GB/T 12777 “General Technical Conditions for Metal Bellows Expansion Joints”, CJ/T 3016 “Bellows Compensators for Urban Heating Pipelines”, and CJ/T 3016.2 “Welded Sleeve Compensators for Urban Heating Compensators”.
• Inspect the appearance of the compensator;
• Verify the model and installation position of each compensator according to the design drawings;
• Check the installation length of the product to ensure it meets the design requirements of the pipeline network;
• Check the size of the connecting pipe to ensure it meets the design requirements of the pipeline network;
• Proofread the product qualification certificate.

For compensators that require pre deformation, the pre deformation amount should meet the design requirements and the pre deformation amount of the compensator should be recorded.
During the acceptance of pipes and fittings in polyethylene gas pipelines, samples should be taken from the same batch, and the specifications, dimensions, and appearance performance should be inspected in accordance with the current national standards “Buried Polyethylene Pipes for Gas” and “Buried Polyethylene Pipes for Gas”. If necessary, comprehensive testing should be conducted.
When cement is used as sealing filler for the socket joint of ordinary cast iron pipes, ordinary Portland cement or Portland expansion cement with a grade of 32.5 or higher should be used; When constructing in cold seasons, it is advisable to use cement with an early strength of 42.5 grade or higher; When the pipeline interface may be subject to chemical corrosion, corrosion-resistant cement of grade 42.5 or higher should be used according to the design requirements. The cement used should meet the requirements of current relevant standards and be within its effective storage period. Before use, it should be ensured that it is not affected by moisture, does not deteriorate, and does not mix with other materials.
When using lead as sealing filler, it is required to have a lead content greater than 99.9% and comply with the current national standard GB 469 “Lead Ingots”.
The oil hemp thread used for interface sealing should be made of flax, linear hemp, and white hemp that are free of impurities, have long fibers, and have good flexibility. They should be immersed in diesel or similar mineral oil, and then taken out and air dried.
When using rubber sealing rings for sealing, their performance must meet the requirements for the use of gas transmission pipes.

5. Identification

For the convenience of management and correct shipment, pipes and fittings should be stacked in different categories and labeled with labels, labels, or writing methods for stacking classification. The identification should indicate the name, model, specification, material, and inspection and testing status of the material separately. The colors of material labels and labels are specified as follows:

• Use white for qualified products;
• Yellow color is used for products to be inspected or processed;
• Scrap products are reported in red.

To implement traceability, after passing the inspection of pipes and fittings, color markings shall be applied to the materials, as specified in Tables 4 and 5.

Table.4 Management Regulations for Steel Pipe Color Band Marking

Serial Number	Name and material	Color Band Regulations	Paint Color
1	20	About 20mm wide, 1 strip, actual length	Green
2	20G	About 20mm wide, 1 strip, actual length	Yellow
3	12CrMov	About 20mm wide, 1 strip, actual length	Red
4	16Mn	About 20mm wide, 1 strip, actual length	White
5	1Cr5Mo	About 20mm wide, 2 strips, physical length	Red+White
6	12CrMo	About 20mm wide, 2 strips, physical length	Red+Green
7	15CrMo	About 20mm wide, 2 strips, physical length	Red+Blue
8	0Cr19Ni9	About 20mm wide, 2 strips, physical length	Green+Green
9	0Cr18Ni9Ti	About 20mm wide, 2 strips, physical length	Lan+Lan
10	1Cr18Ni9Ti	About 20mm wide, 2 strips, physical length	Yellow+Yellow

Note:

① The color code of pipe fittings of the same material is the same as that of steel pipes;

② Regulations on the marking position of pipe fittings with color bands: Tee, full length of main pipe; Big and small heads, from big to small;
Elbow, along the middle; Head, along the diameter of the semicircle; Flat head, marked at the edge; Other pipe fittings should be clearly marked in a prominent position.

Table.5 Management Regulations for Fastener Color Spots

Name	Material	Color dot regulations	Paint color
Bolt	25#	Head and tail	Brown
Nut		Periphery
Bolt	35#	Head and tail	Red
Nut		Periphery
Bolt	30CrMoV(A)	Head and tail	Yellow
Nut		Periphery
Bolt	35CrMo(A)	Head and tail	Green
Nut		Periphery
Bolt	25CrMoV(A)	Head and tail	Ash
Nut		Periphery
Bolt	0Cr17Ni12Mo2	Head and tail	White
Nut		Periphery

If there is only one type of material for pipes and fittings, color identification may not be required; If there are multiple types of materials, the material that accounts for the majority of the materials and the material that is significantly different from other materials may not be marked with color.

6. Warehousing and storage

The storage and storage of pipes and fittings shall be carried out in accordance with Q/CNPC-YGS C7.14-2009 “Material Handling and Storage Control Procedure”.