1. General
In order to standardize the inspection and acceptance of pressure pipes and pipe fittings upon arrival and to ensure the quality of the installation and use of pressure pipes, this regulation has been specially formulated.
This regulation applies to pressure pipeline projects carried out by the company.
Inlet inspection of pipes and pipes appropriate s must not only comply with this regulation, but also comply with the technical requirements of the national standards, specifications and construction drawings in force.
2. Compilation base
- GB50235-97: Code for design and acceptance of industrial metal piping
- HG20225-95: Code for construction and acceptance of metallic chemical pipelines
- SH3501-2002: Code for construction and acceptance of pipelines for highly toxic and flammable media in the petrochemical industry
- SH/T3517-2001: Process standards for construction of petrochemical steel pipelines
- DL/T5031-94: Technical specification for construction and acceptance of power plants (section of pipeline)
- GB50369-2006: Code for construction and acceptance of oil and gas transmission systems
- SY/T0466-97: Code for construction and acceptance of natural gas collection and transportation pipelines
- SY0460-2000: Code for construction and acceptance of natural gas processing plants and pipeline installation technology
- SY0470-2000: Code for construction and acceptance of crossing structures for oil and gas pipelines
- SY0402-2000: Code for construction and acceptance of process pipeline technology at oil and gas stations
- SY/T0422-97: Code for the construction and acceptance of collection and transportation pipelines in oil fields
- CJJ28-2004: Code for the construction and acceptance of urban district heating networks
- CJJ33-2005: Code for Construction and Acceptance of Municipal Gas Transmission and Distribution Facilities
- CJJ63-2008: Technical Specification for Polyethylene Gas Pipeline Engineering
3. Inspection procedures
Product quality certificate inspection → Factory brand inspection → Appearance inspection → Material specifications and inspection → Material reinspection → Non-destructive inspection and testing → Identification → Storage and preservation
Note: A material review will only be 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 label of the received material or no steel grade is specified on the label;
- ③ The information in the certificate of conformity is incomplete or questionable.
4. Inspection requirements for pipes, fittings and valves upon arrival
4.1 General Provisions
4.1.1 General provisions
- Steel pipes, fittings and valves must be ordered according to the model, specifications and technical parameters specified in the project. If changes are required, technical visas must be obtained from the design unit and visa procedures must be processed promptly with the construction unit or technical person in charge.
- Upon arrival of steel pipes, fittings and valves, they must be inspected and accepted, marked and properly stored in accordance with the supply contract and factory quality certificate.
- Steel pipes, pipe fittings and valves must have a quality certificate from the manufacturer and their quality requirements must not be lower than applicable national standards.
- Steel pipes, fittings and valves must be visually inspected before use. Those that do not meet standards should not be used.
- Design documents require materials to undergo a low-temperature impact test. The supplier must provide a document with the results of the low temperature impact test, the indicators of which cannot be lower than those specified in the design documents.
- Design documents require that stainless steel pipes and fittings be subjected to an intergranular corrosion test. The supplier must provide a document with the results of the intergranular corrosion test, the indicators of which cannot be lower than those specified in the project documents.
4.1.2 Inspection of steel pipes
Steel pipes (including rolled tubular sheets) must have a product quality certificate, which usually indicates: supplier name (or factory logo), buyer name, delivery date, contract number, standard number, steel, furnace number, batch number, delivery status, weight and quantity, grade name, size, level, various test results specified in the standard (including reference indicators) and the seal of the technical supervision department.
Steel pipe markings must meet the following requirements:
- 1) Every steel tube with an external diameter of at least 36 mm must be marked. The marking generally needs to contain the steel number, product specification, product standard and supplier stamp, etc. Alloy steel pipes must also have the furnace number and batch number.
- 2) Each package (or box) of bundled or packaged steel pipes must have a label showing the supplier's trademark (or seal), steel number, furnace number, batch number, contract number, product standard number , weight, number of pieces, the date of manufacture and the seal of the technical supervision department must be indicated.
4.1.3 Testing of piping fittings
The flange sealing surface must be smooth and clean, without radial grooves and without pores, cracks, burrs or other defects that affect the strength and reliability of the connection.
Flanges with Male Female faces or Male Female Rings should fit naturally and the height of the hub should not be less than the depth of the groove.
The load-bearing part of the bolts connected to the flange face must be parallel to the flange connecting surface to ensure uniform force on the face during flange connection.
The threads of screws and nuts must be complete and free from defects such as scratches and burrs. Screws and nuts must fit tightly, without loosening or binding.
Asbestos rubber gaskets must be flexible and must not show aging, wear or stratification. The surface must not have defects such as wrinkles or creases.
The surface of the metal joint must be visually inspected with a flat ruler and must have good contact and be free from defects such as cracks, burrs, rust and rough processing. Its hardness should be less than that of the flange.
Metal-encased and spiral-wound seals must be free from defects such as radial scratches or gaps.
The working surface of the slider must be smooth, flexible and free from snags.
Inspection of the appearance and geometric size of pipeline supports and suspension springs must meet the following requirements
- 1) The surface of the spring should not have defects such as cracks, wrinkles, layering, rust, scratches, etc.
- 2) The spring size deviation must meet the drawing requirements.
- 3) The deviation in the number of spring working turns must not exceed half a turn;
- 4) In the free state, the pitch of each spring coil should be uniform and its deviation should not exceed ± 10% of the average pitch.
- 5) The supporting surfaces at both ends of the spring must be perpendicular to the spring axis, and the deviation Δ must not exceed 2% of the free height (as shown in Fig. 1).
Figure.1 Schematic representation of the deviation between the perpendicularity of the spring face and the axis
The springs of the piping supports and hangers must be certified by the factory. If the support and suspension springs do not have factory certificates, the following tests must be carried out before installation:
- 1) Full compression strain test: Compress until the spring coils come into contact with each other and hold for 5 minutes. After unloading the load, the permanent deformation must not exceed 2% of the original height. If exceeded, a second full compression must be performed. The total permanent deformation after two tests must not exceed 3% of the original height. Those that do not meet the above requirements should not be used;
- 2) Compression test under working load: Under working load, the compression degree of the spring must meet the design requirements. The permitted deviation is listed in Table 1.
Table 1 Allowable spring compression deviation
| Effective spring circle number | The permissible deviation of the degree of compression |
| 2-4 | ±12% |
| 5-10 | ±10% |
| >10 | ±8% |
4.1.4 Checking the valves
- Before installation, valves must be visually inspected and must be free from defects such as cracks or sand holes. The sealing surfaces of the valve stem and flange must be flat and smooth, and the valve stem threads must be free of burrs and scratches. If there is a stuffing box, it should be checked and the tightened stuffing box bolts should have enough clearance for adjustment. Valve testing shall be carried out in accordance with the provisions of “Specification for Testing and Installation of Valves” SY/T 4102. If the working medium is water or steam, use water as the pressure test medium. When the working medium is oil and gas, kerosene should be used as the pressure test medium.
- Valves that pass the test must be immediately cleaned of internal water and dried. Except for valves that require degreasing, the sealing surface must be coated with anti-rust oil, the valve closed, the inlet and outlet sealed, clear markings made, and the “valve test report” completed.
- For valves with a steam jacket, the jacket part must be subjected to an endurance test at 1.5 times the operating pressure or in accordance with the product manual.
- The valve operating mechanism and transmission device must be checked in accordance with the design requirements. This requires flexible action and correct display.
- If there are special requirements for inspection and pressure testing in the design documents or technical conditions of the valve, they must be followed.
4.2 Inspection of piping, connections and valves upon arrival
The pipes used in the crossing project must comply with the provisions of GB/T 8163-99 “Seamless steel pipes for transporting liquids”, GB/T 9711.1/2/3 “Technical delivery conditions for steel pipes for industry of petroleum and natural gas” and SY 5036 “Submerged arc welding with spiral seam of steel pipes for transporting pressurized liquids”.
The steel tubes used in the crossing project must undergo new tests of their mechanical properties and chemical composition. The results must comply with the provisions of article 4.2.1 of these Regulations. The sample quantity should be 20% of the total number of crossed steel tubes, but at least one.
The verification of high-pressure steel pipelines for the production and transportation of natural gas must be carried out in accordance with the following standards:
- All steel pipes must be individually numbered and checked for hardness. Their hardness values must correspond to current national standards.
- From each batch of steel pipe, one steel pipe with highest and lowest hardness should be selected (6 samples should be prepared for each steel pipe, including 2 tensile samples, 2 impact samples and 2 flattened or cold bent samples ) to test mechanical performance. Testing requirements must comply with current national standards.
When retesting high-pressure steel pipes for natural gas extraction and transportation, double tests must be carried out if there are unqualified parts. The new test will only be carried out on parts that have yet to pass the original new test. The retested samples were taken from the previously unqualified steel pipe and another steel pipe with the closest hardness to this steel pipe. If the retest results still contain unqualified parts, the batch of steel pipes should be tested individually and unqualified parts should not be used.
High-pressure steel pipes for the extraction and transportation of natural gas must have an ultrasonic test certificate from the manufacturer. If there is no test certificate from the manufacturer, ultrasonic tests must be carried out individually. Ultrasonic testing shall be carried out in accordance with the current JB1151 “Ultrasonic testing of high-pressure seamless steel pipes”.
If repairable defects are found during inspection of steel pipes, they must be gradually polished until the defects disappear. The actual wall thickness after eliminating defects must be at least 90% of the nominal wall thickness of the steel pipe and at least equal to the calculated wall thickness. Steel pipes with severe corrosion and delamination should not be used.
The deviation between the outer diameter and wall thickness of steel pipes must be in accordance with current national standards.
Pipes and fittings used in natural gas collection and transmission stations must comply with the relevant provisions of SY/T 0599-2006 “Requirements for metallic materials relating to resistance to stress cracking of onshore natural gas installations to sulfide compounds”.
The technical requirements for high-pressure pipe fittings and fasteners used in natural gas collection and transmission stations shall be in accordance with the relevant provisions of JB/T 450-1992 “Technical requirements for high-pressure forged angle valves, pipe fittings and fasteners with pN16.0–32.0 MPa”. Technical requirements for pipe connections and fasteners with a pressure rating of less than 16 MPa must comply with national or industry standards.
Arc quality must meet the following requirements:
- The appearance of the elbow should not show defects such as cracks, layers, wrinkles or excessive burning.
- The reduction in arch wall thickness 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 must 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 arc curvature angle error should not exceed ± 1°.
The bends, cold bends and elastically laid pipe sections of the piping route must comply with the provisions of Table 2.
Table 2 Regulations for bent, cold-bent and elastically laid pipe sections
| Type | Radius of curvature R | Appearance and main dimensions | |
| elbow | ≥5D | No wrinkles, tears, 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 curve | D≤323.9mm | ≥30D | No wrinkles, tears, double skin or mechanical damage; the ovality of the curvature is a maximum of 2.0%. |
| T>323.9mm | ≥40D | ||
| Elastic Tube Section | ≥1000D | No wrinkles, tears, double skin or mechanical damage; The eggs curvature is less than or equal to 2.0%. | |
Note: D – External diameter of the tube
Longitudinal welds of straight steel pipe elbows and hot bend bends shall be located at position 450 of the inner bend of the bend and bend. The strain rate of a portion of the pipe diameter must not exceed 4.9% of the nominal pipe diameter and meet the size requirements for passage through the pig pipe (the sphere). Each elbow and bent end must be marked with parameters such as bend angle, steel pipe outer diameter, wall thickness, bend radius and material model. Other requirements must correspond to those set out in Table 2.
The use of bendable elbows and shrimp tail elbows in natural gas collection and transportation pipelines is strictly prohibited.
The vertical deviation of welded or drawn T-pipes must not exceed 1% of their height and 3 mm. The allowable deviation of the vertical length of each end face shall not exceed 1% of the outer diameter of the steel tube and 3 mm.
The center lines of both ends of the concentric reducer should overlap, and its eccentricity value (a1-a2)/2 should be no more than 1% of the outer diameter of the big end and no more than 5 mm, as shown in Figure 2 :
Figure 2: Concentric reducer
The tube bulge must be elliptical or spherical and its quality must meet the following standards:
The minimum head wall thickness must be at least 90% of the nominal head wall thickness and must not be less than the design wall thickness.
The allowable deviation for the roundness of the inner or outer diameter of the head shall be ±2 mm, the allowable deviation for the height of the curved surface shall be ±4 mm and the allowable deviation for the height of the straight edge shall be +5 /-3mm be; Use a 300mm long sample to check the surface roughness, and the gap should not exceed 2mm.
For pipelines with design pressure less than 10 MPa, flat heads must be used, and their thickness and structure must comply with the “Construction Specifications for Steel Petrochemical Pressure Vessels” of China National Petroleum and Chemical Corporation.
If the wall thickness of elbows, reducers and tees exceeds 3.5 mm, a 300-350 groove should be cut into the end and a blunt edge of 1-2 mm should be left.
Standard flanges must meet current national standards, while non-standard flanges must meet the following regulations:
- The permissible deviation of the diameter of the central circle of the screw hole is ±0.3 mm;
- The allowable deviation of the center distance between screw holes (calculated based on chord length) is ± 0.3 mm for adjacent holes. If the nominal diameter of two holes is less than or equal to 500mm, it is ± 1mm; when the nominal diameter is 600-1200mm, it is ±1.5mm.
Insulated connections or flanges must be subjected to a hydraulic test. The test pressure is 1.5 times the design pressure and the settling time is 5 minutes. It is considered qualified if there is no leak. After the pressure test, the remaining water must be dried for insulation testing. Detection must be measured with a 500V megohmmeter and its insulation resistance must be greater than 2MΩ.
Valves must have a product qualification certificate. High pressure valves, electrical valves, pneumatic valves and gas-liquid connection valves must have product user manuals.
Valves designed to undergo low-temperature leakage testing must have a certificate of compliance from the manufacturer for low-temperature leakage testing.
Valve resistance test with clean water as the medium, with test pressure of 1.5 times the nominal pressure and pressure stabilization of at least 5 minutes. If the housing and gasket are tight, the strength test has passed. If there are austenitic stainless steel components in the valve, the chloride ion content of the clean water used for testing must be less than 25 ppm.
Electric, hydraulic and pneumatic ball valves, orifice valves and parallel double spool valves must undergo the required tests for strength, tightness and operational performance in accordance with the requirements of the manual.
The actuating device of hydraulic ball valves must be checked in accordance with the manufacturer's instructions and all components must be intact. The oil level under pressure must be 2/3 of the oil mark and the drive must be flexible.
When testing electrical valves, the following requirements must be observed:
- The gearbox must be clean, the gears must be free from rust or cracks, the gears must be suitable, the engine must not be affected by moisture, sufficient lubricating oil must be filled, and the mechanical and electrical parts of the gearbox must be flexible and easy to use. friendly.
- Adjust the limit switch according to the manufacturer's specifications and, if necessary, carry out a functional test.
- Oil and gas pipeline shut-off valves must undergo visual inspection, valve start-up test and hydraulic test, and their requirements must meet the provisions of Table 3.
Table 3 Inspection and Test Specifications for Shutoff Valves
| Project | Inspection and testing content | Test Patterns | ||
| Visual inspection | Housing | Trachoma | No sand hole | |
| Crack | No cracks | |||
| Additional equipment | Complete and intact | |||
| Old Anti-corrosion coating for buried valves | Spark leak detection: No leak points | |||
| Opening and closing inspection | Open and closed | Flexible | ||
| Opening and closing indicator | precision | |||
| Hydrostatic Test | Shell strength test | 1.5 times maximum working pressure, stabilized for 5 minutes | No leakage | |
| Valve leak test | 1.1 times maximum working pressure, stabilized for 2 minutes | No leakage | ||
The number of resistance and tightness tests for connections at natural gas collection and transmission stations is generally carried out in the following proportions:
- Valves with a nominal diameter equal to or less than 50 mm and a nominal pressure equal to or less than 1.6 MPa must be sampled at 10% of each batch, with at least 1 valve sampled. If there are unqualified valves, an additional 20% must be sampled. If additional sampling still reveals unqualified valves, each batch of valves must be tested individually.
- All valves with a nominal diameter greater than 50 mm or a nominal pressure greater than 1.6 MPa must be tested.
- Various anti-corrosion materials, including primer, primer, repair and repair materials, should be randomly tested for their coating or coating in accordance with relevant technical standards or design requirements before use. If the test fails, the number of samples must be doubled for random sampling. If it still fails, it should not be commissioned.
4.3 Inspection of industrial piping, fittings and valves upon arrival
When checking the appearance of steel pipes, its quality must meet the following requirements:
The surface must be free from defects such as cracks, wrinkles, folds, delaminations, cracks and scars;
There should be no defects such as rust, corrosion, corrosion and mechanical damage that exceed the negative deviation of the wall thickness.
Steel tubes for Class A or I pipelines must be sampled at 10%, and Class B or II pipelines must be sampled at 5%, with at least one tube used to measure the outside diameter and wall thickness. The allowable size deviation of seamless carbon steel pipes shall be in accordance with the provisions of GB/T 8163-99 “Seamless steel pipes for conveying liquids”. The allowable deviation of the size of seamless stainless steel pipes shall be in accordance with the provisions of GB/T 14976-2002 “Seamless stainless steel pipes for conveying liquids”.
For SHA grade pipelines with design pressure of at least 10 MPa, the outer surface must be subjected to non-destructive testing using the following methods. There should be no linear defects:
- For magnetic steel pipes with an outer diameter greater than 12 mm, magnetic particle testing must be carried out.
- Non-magnetic steel pipes must be tested for penetration.
Surface defects detected by magnetic particle or pipe penetration tests can be grinded, and the actual wall thickness after grinding should not be less than 90% of the nominal pipe wall thickness.
For Class SHA pipelines conveying extremely hazardous media with a design pressure of less than 10 MPa, 5% and not less than one tube from each batch (referring to the same batch number, furnace number, material and specification) shall be used for magnetic particles. or external surface penetration test and there should be no linear defects. If the random check fails, repeat the random check. If there are still unqualified samples, the pipeline batch should not be used.
The quality certificate for pipes transporting highly toxic media must contain the results of ultrasonic tests. Otherwise, further tests must be carried out sequentially in accordance with the current GB/T 5777 “Ultrasonic test methods for seamless steel tubes”.
Alloy steel bolts and nuts used for pipelines with design pressure of at least 10 MPa must be subjected to rapid spectral analysis individually. Two pieces must be removed from each batch for hardness testing. If there are unqualified parts, double sampling must be carried out. If there are still unqualified parts, the nuts and bolts from this batch should not be used.
Alloy steel bolts and nuts for low-temperature pipelines with a design temperature of -29°C or less must be individually inspected by rapid spectral analysis. Two screws must be selected from each batch for low temperature impact testing. In case of deviations, the sample test must be duplicated. If there are still deviations, the batch of nuts and bolts must 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 tested. In case of deviations, the sample test must be duplicated. If discrepancies still exist, the batch of piping components should not be used.
The following pipeline valves must be subjected to a jacket pressure test and a leakage test one after the other. Valves that do not meet standards must not be used.
- Valves for pipelines for transporting highly toxic, poisonous and flammable liquids;
- Valves for transporting non-flammable and non-toxic liquids in pipelines with a design pressure greater than 1 MPa or a design pressure less than or equal to 1 MPa and a design temperature less than -29 °C or greater than 186 °C.
Valves designed to transport non-flammable, non-toxic liquids with a design pressure of 1 MPa or less and a design temperature of -29°C to -186°C must be sampled in 10% of each batch and at least one valve must be tested for pressure and hull sealing. If not qualified, double sampling must be performed. If not yet qualified, the batch of valves should not be used.
The test pressure of the valve shell must be at least 1.5 times the nominal pressure, and the test time must be at least 5 minutes. It is considered qualified if the filling of the casing does not leak. The leak test must be carried out at rated pressure and is considered qualified if the sealing surface of the valve disc does not leak.
Gate valves with a nominal pressure of less than 1 MPa and a nominal diameter of at least 600 mm shall not be subjected to separate shell pressure tests and valve tightness tests. The liner pressure test can be carried out according to the test pressure of the piping system during the system pressure test. The slider leakage test can be checked by methods such as color printing, and the color printing on the connecting surface must be continuous.
If the assembly has contractual requirements or the manufacturer guarantees the quality of the product and provides a guarantee of quality and use of the product, disassembly and leak tests on different types of valves are not permitted. Otherwise, the following valves must be disassembled and checked before installation:
- Used for valves with a design temperature greater than or equal to 450°C;
- safety valves and butterflies;
- Valves that failed the leak test.
Before disassembling the valve, dirt and debris must be removed. Otherwise, opening and closing operations as well as disassembly are not permitted. When disassembling and inspecting valves with special designs, the disassembly sequence specified by the manufacturer must be followed to avoid damage to components or compromising personal safety.
The dismantled valve must be checked as follows:
- The internal parts of alloy steel valves must undergo a follow-up spectral examination (components may not be marked, but the results of the examination must be recorded).
- Whether the connection between the valve seat and the valve body is tight and whether there is any play;
- Check whether the connecting surface between the valve core and the valve seat matches and whether the connecting surface has any defects.
- Whether the connection between the valve stem and the valve insert is flexible and reliable;
- Whether the valve stem is bent or corroded, whether the seal between the valve stem and the stuffing box is sufficient, and whether there are defects such as broken threads on the valve stem;
- Valve cover flange surface connection condition;
- The opening and closing stroke as well as the final position of the butterfly valve must be checked and as many markings made as possible.
After testing and eliminating defects, the valve must 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 shows correctly;
- The specifications and quality of all seals and fillings meet technical requirements;
- The filling arrangement is correct, and the interface should be cut into oblique openings, and the interfaces of each layer should be offset from each other; After the gasket is compressed, it must maintain its seal and not interfere with the opening and closing of the valve stem.
Valves used in the oil system must be cleaned of their flow parts, freed from molding sand and paint, and replaced with oil-resistant gaskets and seals.
When assembling gate valves 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 reassembling the valve, a leak test must be carried out.
Safety valves must be tested in accordance with the opening pressure specified in the design documents. The pressure must be stable during pressure regulation, and the opening and closing tests of each safety valve must be carried out at least three times. After carrying out the test, the “Safety valve initial test report” must be completed.
4.4 Inspection of public pipes, connections and valves upon arrival
Pipeline equipment and components used in gas transmission and distribution project must comply with applicable national product standards and have product qualification documents from the quality inspection department of the production facility.
For materials that are required to undergo a low-temperature impact test in the design documents, the supplier must provide a document containing the results of the low-temperature impact test. Otherwise, the test must be carried out in accordance with the requirements of the current national standard GB/T 229 “Low-temperature impact test method on metals” and its indicators must not be lower than the lower limit of the specified value.
The quality of steel gas pipe elbows, tees and reducers must comply with the current national standard GB 12459 “Fittings for steel welded seamless pipes”.
When testing ductile cast iron pipes and fittings, the following requirements must be met:
- The surface of pipes and connections must not have cracks or irregularities that could affect their use.
- When using rubber O-rings for sealing, their performance must meet the requirements for using gas transmission media. The rubber ring must be smooth and have a clear contour, and there must be no defects that affect the sealing of the interface.
- Dimensional tolerances of pipes and fittings must comply with current national standards GB 13295 Centrifugally Cast Ductile Iron Pipes and GB 13294 Ductile Iron Fittings.
Before connecting polyethylene and polyethylene composite steel frame piping, the specifications and pressure ratings of the pipes and fittings to be connected must be checked. The surface of the pipes should be checked to ensure that there are no protrusions or scratches, and the depth of the scratches should not exceed 10% of the wall thickness of the pipes.
Before installing the valve on the gas heating line, the opening and flexibility of the valve insert must be checked.
When checking the accessories used in the heating pipe network before installation, the following regulations must be respected:
- Valves used in the design of the heating pipeline network must have a product qualification certificate from the manufacturer.
- Valves used in the main piping of the primary piping network and valves directly connected to the main piping of the primary piping network, as well as valves and other important valves that serve closing and protective functions at the main end of the branch piping and the entrance to the heating station, must be inspected by a qualified inspection department and subjected to resistance and leakage tests. They must be inspected and qualified, stored separately, positioned for use, and valve test reports completed.
When testing the compensator, the following points must be checked:
- The compensator used must comply with the relevant provisions of the current national standards GB/T 12777 “General technical conditions for metal bellows compensators”, CJ/T 3016 “Belows compensators for district heating pipes” and CJ/T 3016.2 “Welding compensators socket for district heating compensators”.
- Check the appearance of the compensator.
- Check the model and installation position of each expansion joint based on the design drawings.
- Check the installation length of the product to ensure it meets the duct network design requirements.
- Check the size of the connecting pipe to ensure it meets the design requirements of the piping network.
- Review of the product qualification certificate.
For expansion joints that require pre-deformation, the degree of pre-deformation must meet the design requirements and the degree of pre-deformation of the expansion joint must be recorded.
When accepting pipes and connections in polyethylene gas pipelines, samples must be taken from the same batch and the specifications, dimensions and appearance must be checked in accordance with current national standards “Buried Polyethylene Pipes for Gas” and “Buried Polyethylene Pipes for Gas”. If necessary, comprehensive testing must be carried out.
When cement is used as a sealing filler for the socket joint of ordinary cast iron pipes, ordinary Portland cement or Portland expansion cement with grade 32.5 or higher should be used. When building in the cold season, it is advisable to use cement with an initial strength equal to or greater than 42.5. If the piping interface may be subject to chemical corrosion, grade 42.5 or higher corrosion-resistant cement shall be used in accordance with project requirements. The cement used must meet the requirements of current relevant standards and be within its effective shelf life. Before use, it must 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, the lead content must be above 99.9% and comply with the current national standard GB 469 “Lead Ingots”.
The hemp oil thread used for interface sealing should be made of flax, linear hemp and white hemp, which is free from impurities, has long fibers and good flexibility. It should be dipped in diesel or similar mineral oil and then removed and allowed to air dry.
When sealing gas pipes, rubber sealing rings must be used, the performance of which must meet the requirements for use in gas pipe systems.
5. Identification
To facilitate management and correct transportation, pipes and fittings should be stacked in different categories and marked with tags, labels or writing methods for stack classification. The marking shall separately indicate the name, model, specification, material and inspection and testing status of the material. The colors of labels and material labels are indicated as follows:
- Use white for qualified products;
- The color yellow is used for products to be tested or processed;
- Rejected products are marked in red.
To ensure traceability, once pipes and fittings have passed inspection, materials must be color coded as shown in Tables 4 and 5.
Table 4 Administrative regulations for steel pipe tape marking
| serial number | Name and material | Ribbon Regulations | paint color |
| 1 | 20 | Approx 20mm wide, 1 strip, actual length | Gre |
| two | 20G | Approx 20mm wide, 1 strip, actual length | Yellow |
| 3 | 12CrMov | Approx 20mm wide, 1 strip, actual length | Red |
| 4 | 16 million | Approx 20mm wide, 1 strip, actual length | White |
| 5 | 1Cr5Mo | Approximately 20mm wide, 2 straps, physical length | Red + White |
| 6 | 12CrMo | Approximately 20mm wide, 2 straps, physical length | Red + Green |
| 7 | 15CrMo | Approximately 20mm wide, 2 straps, physical length | Red + Blue |
| 8th | 0Cr19Ni9 | Approximately 20mm wide, 2 straps, physical length | Green + Green |
| 9 | 0Cr18Ni9Ti | Approximately 20mm wide, 2 straps, physical length | Lan+Lan |
| 10 | 1Cr18Ni9Ti | Approximately 20mm wide, 2 straps, physical length | Yellow+yellow |
observation :
① The color code of pipe fittings made of the same material is the same as that of steel pipes;
② Regulations on the marking position of pipe fittings with color bands: T-piece, total length of the main pipe; Big and small heads, from big to small;
Elbow, in the middle; head, along the diameter of the semicircle; Flat head, marked on the edge; Other pipe fittings must be clearly marked in a visible location.
Table 5: Administrative Requirements for Paint Stains on Fasteners
| Surname | material | Color Point Regulations | paint color |
| screw | 25# | head and tail | Brown |
| nut | Periphery | ||
| screw | 35# | head and everything | Red |
| nut | Periphery | ||
| screw | 30CrMoV(A) | head and tail | Yellow |
| nut | Periphery | ||
| screw | 35CrMo(A) | head and tail | Green |
| nut | Periphery | ||
| screw | 25CrMoV(A) | head and tail | ashes |
| nut | Periphery | ||
| screw | 0Cr17Ni12Mo2 | head and tail | White |
| nut | Periphery |
If there is only one type of material for pipes and fittings, color coding can be omitted; If there are multiple types of materials, the material that constitutes the majority of materials and the material that is significantly different from other materials may not be color-coded.
6. Storage and preservation
Storage and storage of pipes and accessories must be in accordance with Q/CNPC-YGS C7.14-2009 “Material Handling and Storage Control Procedures”.
