I. Introduction
In oil and gas, petrochemical, LNG, offshore engineering, and new energy international EPC engineering projects, pipeline fittings serve as pressure-bearing components of pressure piping, and the core task of foreign trade procurement is to accurately identify the full set of technical parameters.Domestic procurement of ordinary materials mostly focuses only on product name, specification, and quantity, whereas the parameter system for international engineering pipeline fitting procurement is more complex, with multiple standard systems running in parallel; the dimensional, pressure, and wall thickness parameter rules of American standard ASME, European standard EN, and national standard GB differ from one another and cannot be arbitrarily treated as equivalent substitutions.The root cause of many foreign trade project disputes is not product manufacturing quality defects, but rather omissions in parameter identification, misunderstandings, and parameter confusion in the early procurement stage.
Foreign trade procurement parameters are sourced from the RFQ inquiry package, pipeline single-line diagrams (ISO drawings), P&ID process flow diagrams, pipeline lists, MTO material take-off lists, and project material specification sheets. Procurement, technical, and quotation personnel need to extract, verify, and cross-validate all parameters item by item from multiple engineering drawings and technical documents; any missing parameter identification will lead to wrong materials, and after the goods arrive at the overseas site, they will be rejected by the owner, resulting in high ocean freight costs, port demurrage charges, rework costs, and project delay compensation.
At present, many domestic pipeline fitting foreign trade practitioners are accustomed to following the domestic procurement approach, simply recording the fitting name and diameter while ignoring key constraint parameters such as pressure rating, wall thickness, complete material grade, governing standard, sealing face, non-destructive testing, heat treatment, and material certificate type.For example, simply equating Class 300 flanges with PN50, confusing NPS nominal pipe size with actual outside diameter, replacing LR long-radius elbows with SR short-radius elbows, and abbreviating material grades by omitting suffixes will all cause the entire batch of products to fail to meet the project technical specifications.
Based on the practical experience of foreign trade procurement of pipeline fittings, this article divides parameter categories, systematically explains the identification key points, reading methods, and common identification pitfalls of each category of parameters, builds a standardized identification process of parameter extraction, cross-checking, and document comparison, clarifies the parameter consistency control requirements among drawings, orders, physical steel stamps, and MTC material certificates, and helps enterprises establish foreign trade procurement parameter identification capabilities and reduce cross-border order fulfillment risks.
II. Overall Classification of Foreign Trade Procurement Parameters for Pipeline Fittings
The procurement parameters of foreign trade pipeline fittings can be divided into six major categories, forming a complete parameter identification system. Each category of parameters is indispensable and must be identified simultaneously and cross-verified.
The first category, product structure and connection parameters: fitting type, connection method, bending radius, and sealing face form, used to determine the structural form of fittings, such as elbows, tees, reducers, flanges, and branch outlets, and to distinguish butt welding, socket welding, and threaded connection.
The second category, dimensional parameters: NPS/DN nominal size, end dimensions, SCH wall thickness schedule, and finished product tolerances, determining the overall dimensions and groove specifications of fittings and ensuring matching welding between fittings and straight pipes.
The third category, pressure and temperature parameters: Class rating, PN nominal pressure, design temperature, and medium working conditions, determining the pressure-bearing capacity of fittings and serving as the core safety parameters of pressure pipelines.
The fourth category, material parameters: ASTM material grades, delivery condition, heat treatment requirements, and special medium requirements (NACE sour service resistance, low-temperature impact), determining the temperature resistance, pressure resistance, and corrosion resistance of materials.
The fifth category, standards and specification parameters: product manufacturing standards, material standards, inspection standards, and certification requirements (PED, DNV), defining manufacturing, inspection, and acceptance rules.
Category six, inspection, documentation and traceability parameters: NDT ratio for non-destructive testing, hydrostatic test, MTC certificate type, heat number traceability, stamp marking, third-party supervision requirements.
A complete and qualified foreign trade procurement description must cover all parameters of the six major categories. Relying solely on simple descriptions such as "carbon steel elbow NPS2" provides severely insufficient parameter information and cannot meet the procurement requirements of international EPC projects.
III. Identification of product structure and connection parameters
Product structure parameters are the first step in parameter identification. First confirm the fitting type and connection form, and identify the fitting type from the MTO list and single-line diagram legend.Elbows are divided into 90° elbows, 45° elbows, and 180° return bends;Distinguish LR long-radius elbows (R=1.5D) from SR short-radius elbows (R=1D). The two are similar in appearance, but their bending radii differ, resulting in differences in pipeline stress calculation results. Unapproved substitution is not allowed in foreign trade projects.Tees are divided into equal tees, reducing tees, and lateral tees;Reducers are divided into concentric reducers and eccentric reducers. Eccentric reducers are mostly used in horizontal pipelines to prevent liquid accumulation. They must be distinguished on drawings; once confused during the procurement identification stage, the on-site pipeline cannot be installed.
Flange parameter identification is a high-frequency key point in foreign trade procurement.Flange structural forms include WN butt weld flanges, SO slip-on flanges with neck, SW socket weld flanges, BL blind flanges, and LJ lap joint flanges.Flange sealing faces are parameters that are extremely prone to identification errors, including RF raised face (general purpose), FF full face, MFM male-and-female face, and RJ ring joint face.The RJ ring joint face is matched with a metal ring gasket and is used for Class600 and above high-temperature and high-pressure oil and gas pipelines. Incorrect identification of the sealing face will directly result in the inability to seal on site and medium leakage.
Connection methods are divided into butt weld BW, socket weld SW, and threaded NPT/BSP.Butt weld pipe fittings have beveled ends, matching the outer diameter of straight pipes for welding;Socket weld pipe fittings have reserved sockets inside and are commonly used for small-diameter high-pressure forgings;Threaded pipe fittings are used for small instrument pipes. Different thread systems, NPT American tapered threads and BSP British threads, cannot be interchanged, and the thread standard must be confirmed during the identification stage.Branch fittings (Olet) include Weldolet, Sockolet, and Threadolet, which are widely used in high-pressure oil and gas projects; when identifying procurement parameters, they cannot be simply equated with tees.
IV. Identification of dimensional series parameters: NPS, DN, SCH wall thickness
Nominal size is a basic dimensional parameter in foreign trade procurement; the American standard system uses NPS, while the European standard and national standard use DN.NPS is the nominal pipe size, not the actual outer diameter of the pipe. For example, NPS2 corresponds to DN50, but the NPS value cannot be directly understood as the inch outer diameter; the actual outer diameter of fittings must be checked in ASME B36.10M.A common misconception among many procurement personnel: equating NPS with outer diameter, causing the fitting end bevel dimensions to fail to match those of the straight pipe.The marking format for NPS reducing fittings is NPS4×2, representing main pipe NPS4 and branch pipe NPS2. When reading the MTO list, the dimensions at both ends must be read completely, and the large-end dimension alone must not be recorded.
SCH wall thickness (Schedule) is the American standard wall thickness series for fittings; the larger the SCH number, the thicker the wall thickness. SCH40 is standard wall thickness, SCH80 is extra strong, and SCH160 and XXS are double extra strong.Stainless steel fittings use the S series wall thicknesses, 10S, 40S, and 80S. The wall thickness values of carbon steel SCH and stainless steel SCH are not the same; when identifying parameters, the wall thickness series corresponding to the material must be distinguished.In foreign trade projects, the SCH wall thickness of pipe fittings must be consistent with the SCH of the matching straight pipe; otherwise, the groove wall thickness will be unequal, greatly increasing the difficulty of welding construction, and may even make welding impossible.When identifying parameters, in addition to the SCH designation, the minimum wall thickness tolerance also needs to be confirmed. ASME standards allow negative wall thickness deviation, and the technical agreement will stipulate the minimum wall thickness lower limit; one cannot look only at the nominal SCH.
The main source for identifying dimensional parameters is the pipeline single-line diagram.The single-line diagram marks the line number, the dimension from the fitting center to the end face, and the groove angle. When procurement personnel read the drawing, they need to read the end groove angle and the groove root thickness. Butt-welded pipe fitting grooves are generally executed in accordance with ASME B16.25.At the same time, identify the tolerance requirements: length, outer diameter, and groove dimension tolerances. Different standards have different tolerance ranges. Lock down the tolerances during the identification stage to avoid out-of-tolerance finished product dimensions.
V. Pressure and temperature parameter identification: Class pound rating and PN nominal pressure
The pressure rating parameter is the core of pressure piping safety, and it is also the section most prone to errors in foreign trade parameter identification.The American standard system uses Class pound ratings: Class 150, 300, 600, 900, 1500, and 2500;The European standard and national standard systems use PN nominal pressure, PN16, PN25, PN40.Many procurement personnel have a major misconception, directly converting Class into a fixed MPa pressure, for example, Class300 is directly equated to 5.0MPa.In fact, the allowable pressure corresponding to the Class pound rating decreases as the medium temperature rises; the higher the temperature, the lower the allowable pressure. The pound rating is a temperature-pressure rating system, not a constant pressure value. Class and PN cannot be unconditionally equivalently interchanged; they can only be used for reference comparison under specific normal temperature conditions, and cannot be directly substituted during project selection.
When identifying parameters, one must not only read the pressure rating, but also simultaneously identify the design temperature, operating temperature, and medium.Under high-temperature working conditions, the allowable pressure of pipe fittings of the same Class rating significantly decreases;For low-temperature working conditions, the minimum design temperature must be identified to determine whether low-temperature impact testing is required.Medium parameter identification is equally critical. For oil and gas projects containing hydrogen sulfide, the NACE MR0175 sour service requirement must be identified, material hardness must be controlled, and sulfide stress cracking must be prevented. Ordinary carbon steel cannot meet sour service conditions. If the NACE requirement is omitted during the parameter identification stage, the procured pipe fittings will pose a major safety hazard in sour service pipelines.
VI. Material grade parameter identification
Material grade parameters directly determine the mechanical properties and corrosion resistance of pipe fittings. Incorrect material identification is the most serious quality defect in foreign trade orders. Once on-site PMI spectral re-inspection finds that the material does not match, the entire batch of goods will be rejected.For foreign trade projects, material grades must be read in full and must not be abbreviated.
American standard forged flanges commonly use A105 (carbon steel forgings) and A182 F304/F316L (stainless steel forgings);butt-welded pipe fittings use A234 WPB (carbon steel butt-welded pipe fittings) and A403 WP304 (stainless steel butt-welded pipe fittings);low-temperature forgings use A350 LF2, used for LNG low-temperature pipelines.A complete material identification needs to include the ASTM standard number + grade, for example ASTM A234 WPB. Writing only carbon steel or 304 leaves the parameter information incomplete and prone to ambiguity.
Material parameter identification also includes the material delivery condition. A105N represents normalized treatment. Low-temperature projects require impact testing, and the Charpy V-notch impact test temperature and impact energy indicators must be identified.For offshore chloride corrosion conditions, identify corrosion-resistant alloys such as duplex stainless steel A815 F51.
The heat number is a core parameter for material traceability.The heat number (Heat No) is the smelting batch of the steel mill. From the raw material forging billet to the finished pipe fitting, the heat number follows throughout the entire process, and the heat number is permanently marked on the body of the pipe fitting by steel stamping.The MTC material certificate, heat treatment report, and non-destructive testing report are all bound to the corresponding heat number.At the parameter identification stage, the project traceability requirements must be clarified, confirming the need for piece-by-piece steel stamping and heat-by-heat document matching, to eliminate the mixing of materials from different heats.
VII. Identification of Executive Standards and Certification Parameters
Standard parameters define the specifications that pipe fitting manufacturing and inspection must follow. During parameter identification, the complete standard number must be locked in, including the version year; it is not acceptable to simply write "American standard".Common standards for American standard pipe fittings: ASME B16.5 flange standard, ASME B16.9 factory-made butt-welded pipe fittings, ASME B16.11 forged socket-welded pipe fittings, ASME B31.3 process piping code.European standard projects implement EN10253 for butt-welded pipe fittings and EN10204 for material certificate specifications. For projects exported to the EU, identify the PED Pressure Equipment Directive CE certification and confirm that the certificate covers the material, pressure rating, and product type; if the certificate does not cover them, the goods cannot clear customs.
Offshore engineering vessel projects identify DNV and ABS classification society certifications;Petroleum projects identify API standards.Parameter identification must distinguish three types of standards: product manufacturing standards, material standards, and inspection standards. ASME specifies the dimensional manufacturing rules for pipe fittings, while ASTM specifies the chemical composition and mechanical properties of materials. The two are used together and must not be confused.
VIII. Identification of Inspection, Testing, and Documentation Parameters
In international EPC foreign trade projects, inspection and testing parameters are procurement parameters that cannot be ignored. Many orders only identify product specifications and omit inspection requirements, resulting in factory documentation that does not meet the owner's requirements.Parameter identification includes non-destructive testing (NDT) requirements: UT ultrasonic testing, MT magnetic particle testing, PT penetrant testing, and RT radiographic testing. Identify the inspection proportion: 100% inspection or sampling inspection, and which processes require Hold Points for work stoppage and witness.Hydrostatic Test: identify the test pressure and pressure holding time;Identify pneumatic testing for special operating conditions.
The MTC material certificate type is a high-frequency parameter in foreign trade; EN10204 is divided into 2.1, 2.2, 3.1, and 3.2 certificates.The 3.1 certificate is issued by the manufacturer's quality inspection department;high-end oil and gas projects mandate the 3.2 certificate, which is issued by a third-party independent witness test.When identifying parameters, the certificate type must be confirmed in the RFQ document; if the certificate type is identified incorrectly, the owner will reject acceptance even if the physical goods are qualified.
At the same time, identify the PWHT post-weld heat treatment requirements; thick-wall carbon steel and low-alloy pipe fittings require stress relief heat treatment after welding, and complete heat treatment curve records are required;identify the PMI on-site re-inspection requirements; overseas project sites generally conduct spectral re-inspection of materials;identify the third-party inspection TPI requirements, i.e., whether on-site witness of key processes is required, and define Hold Points and Witness Points.
IX. Methods for Extracting Procurement Parameters for Pipes and Fittings (Reading Parameters from Drawings and Inquiry Documents)
Foreign trade procurement parameters are mainly extracted from the RFQ inquiry package. The RFQ includes the MTO material list, pipeline single-line diagrams, pipeline schedule, project material specification, and technical requirement attachments.Parameter identification should adopt a multi-file cross-comparison method and must not rely solely on the MTO list.The MTO list provides quantities and brief specifications; the single-line diagrams provide pipeline operating conditions and connection types; the material specification provides general mandatory requirements for materials, inspection, and standards. The parameters from these three sources must remain consistent. If parameter conflicts arise, clarification must be sought from the EPC general contractor and the owner immediately, and a written clarification record must be formed as the technical basis for the order.
Step 1: Read the MTO list, extract fitting type, NPS/DN size, material, and quantity, and initially establish a parameter list.Step 2: Retrieve the corresponding pipeline single-line diagrams, verify fitting connection types, bevels, and bending radii, and read the line number, design temperature and pressure, and medium.Step 3: Consult the project material specification to lock down the applicable standards, NDT inspection ratio, heat treatment, MTC certificate type, and special service condition requirements (NACE, low-temperature impact). Step 4: cross-compare the P&ID diagrams to confirm the pipeline medium and operating conditions, and verify the rationality of the material selection.Step 5: Compile all parameters, list the parameter checklist, mark conflicting and ambiguous items, submit technical clarifications, obtain written responses from the owner, and use the clarification documents as technical attachments to the contract.
Parameter identification must result in a written parameter verification checklist, with each item checked and confirmed; verbal descriptions shall not serve as the basis for parameters.The biggest risk in foreign trade orders is vague parameters and ambiguity; without written clarification, disputes will arise later.
X. Analysis of Common Misconceptions in Parameter Identification
1. Pressure rating misconception: directly treating Class pound ratings and PN as equivalent substitutions
Class is a temperature-pressure rating system, not a constant pressure; as temperature changes, the allowable pressure changes, so one cannot simply equate Class 300 with PN50. Many procurement personnel convert based on experience, resulting in insufficient pressure-bearing capacity under high-temperature conditions and creating safety hazards.
2. Confusion among NPS, DN, and outside diameter
Both NPS and DN are nominal sizes and are not equal to the actual outside diameter; NPS 2 is not equal to a 2-inch outside diameter. The outside diameter table in ASME B36.10M must be consulted.Domestic procurement practice tends to understand size as DN inside diameter, while the American standard system is based on outside diameter; directly mixing the two will cause mismatches in fitting end dimensions.
3. Elbow bending radius parameter ignored
LR long-radius elbows are the default for conventional projects; the absence of a note on the drawing does not mean SR short-radius elbows may be selected at will. The two are not freely interchangeable, and parameter identification must confirm the bending radius.
4. Incomplete material abbreviations
Only 304 or carbon steel is marked, without a complete ASTM grade, and lacking delivery condition and impact test requirements; material properties vary enormously between different delivery conditions.
5. Missing sealing face parameters
Flange procurement only identifies NPS and Class while ignoring the sealing face; gaskets for RF, RJ, and MFM sealing faces are not interchangeable, and selecting the wrong sealing face will prevent the flange from sealing on site.
6. SCH wall thickness confusion between carbon steel and stainless steel series
Stainless steel pipe fittings use the S series wall thickness; the wall thickness values of 40S and carbon steel SCH40 are not the same, and directly applying carbon steel SCH will result in insufficient wall thickness or mismatched bevels.
7. Neglecting inspection and documentation parameters
Focusing only on the physical specifications of pipe fittings, without identifying NDT, MTC certificate types, or supervision requirements; the physical product is qualified, but the documentation does not meet the owner's requirements, resulting in cargo rejection.
8. Missing identification of heat number traceability parameters
Not requiring piece-by-piece steel stamping or one-to-one correspondence of heat numbers; upon PMI re-inspection at the port of arrival, material, heat number, and certificate mismatches are found, resulting in rejection of the entire batch.
XI. Closed-Loop Process for Verification of Foreign Trade Procurement Parameters
Parameter identification is not a one-time read; a full closed-loop verification process of "extraction-comparison-clarification-solidification-production briefing-factory re-check" needs to be established.
1. Parameter extraction stage: extract all six major categories of parameters from the RFQ, single-line diagrams, and material specifications, and create a parameter summary table.
2. Cross-comparison stage: compare parameters across the MTO list, single-line diagrams, and material specifications, and flag contradictory and ambiguous parameter items.
3. Technical clarification stage: For items in question, issue technical clarifications to the general contractor, obtain written replies, and incorporate the clarification documents into the technical agreement.
4. Parameter finalization stage: Write the full set of confirmed parameters into the procurement contract and technical agreement. The technical agreement takes precedence over the general terms and conditions of the contract. Lock all parameters and prohibit oral agreements.
5. Production briefing stage: The technical department briefs the production workshop on the full set of parameters. Steel stamp markings, raw material procurement, processing, and inspection shall be strictly executed according to the confirmed parameters, and the steel stamp content shall remain consistent with the order parameters.
6. Pre-shipment review stage: Before the product leaves the factory, review the physical steel stamps, dimensions, MTC certificates, and flaw detection reports. The certificate parameters, steel stamp parameters, and order parameters must be unified; if inconsistent, shipment shall not be made.
Core objective of the entire process: Ensure that the parameters across the five parties—inquiry, order, drawings, physical product, and documentation—are fully consistent, eliminating parameter deviations.
XII. Performance risks caused by parameter identification deviations
Deviations in parameter identification will trigger multi-level risks.First, manufacturing-stage risks: Incorrect raw material procurement, wrong selection of material grade and wall thickness, scrapping of finished products, increased production costs, and schedule delays.Second, the supervision stage risk: third-party inspection (TPI) finds that parameters do not conform to the ITP inspection plan and issues an NCR (non-conformance report), which must be rectified and closed, extending the production cycle.Third, the ocean shipping delivery risk: when the goods arrive at the destination port, unpacking inspection and PMI spectral re-inspection reveal parameter non-conformities, and the owner directly rejects the goods, incurring high ocean freight, port demurrage charges, and return costs.Fourth, project schedule and commercial claims: delayed delivery of pipe fittings causes the EPC general contractor to bear liquidated damages (LD) to the owner, and the general contractor will claim against the pipe fitting supplier under the procurement contract, causing huge economic losses.Fifth, long-term warranty risk: parameter errors lead to leakage and failure during the pipeline operation stage, bringing safety accidents and long-term warranty liability.
Many companies regard parameter identification as simple clerical work, but in fact parameter identification is the first gate of foreign trade technical risk control, and the losses caused by parameter identification errors are far higher than the value of the pipe fittings themselves.
XIII. Countermeasures for improving the parameter identification capability of pipeline pipe fitting foreign trade
1. Establish a standardized parameter identification checklist template; for each RFQ inquiry, extract parameters item by item according to the checklist to avoid omitting key items.The checklist includes items such as pipe fitting type, NPS/DN, SCH wall thickness, Class/PN, complete material grade, applicable standard, connection form, sealing face, design temperature and medium, NDT requirements, MTC certificate type, heat number traceability, and supervision requirements.
2. Conduct drawing interpretation training so that foreign trade, sales, and quotation personnel master the basic drawing interpretation skills for pipeline single-line diagrams, P&ID, and pipeline schedules, understand legends and pipeline parameters, and distinguish between the two dimensional and pressure systems of American standards and European standards.
3. Establish a parameter cross-review system: after a single person extracts parameters, a technical engineer performs a second review, with two-person verification to reduce individual comprehension deviations.
4. Establish a project technical clarification mechanism: whenever parameters are ambiguous or conflicting, written clarification must be obtained, and subjective speculation based on experience is not allowed; clarification documents shall serve as order attachments.
5. Standardize steel stamping and document management: when order parameters are confirmed, the steel stamp content shall be clarified simultaneously, and the parameters and heat numbers in MTC material certificates and NDT reports shall be consistent with the physical steel stamps.
6. Establish standard databases by category, and compile comparison tables of commonly used ASME and EN pipe fitting parameters, NPS outside diameter tables, Class temperature and pressure tables, and material grade comparison tables for procurement and quotation personnel to consult quickly and reduce conversion errors.
7. Conduct pre-order operating condition assessment, identify the medium, temperature, and corrosive environment, and determine whether additional parameters such as NACE sour service resistance, low-temperature impact, and special surface treatment are required, so as to avoid omitting technical requirements for special operating conditions.
XIV. Conclusion
Parameter identification for foreign trade procurement of pipeline fittings is the foundational work of material control in cross-border EPC projects. Unlike simple specification procurement in the domestic market, foreign trade parameters are a multi-dimensional technical set covering six major modules: structure, dimensions, pressure, material, standards, and inspection traceability.Parameters originate from the RFQ inquiry package, piping single-line diagrams, MTO material lists, and project material specifications. The identification work requires cross-referencing multiple documents, clarifying ambiguous parameters, and consolidating them into the technical agreement.
NPS/DN nominal size, Class rating, SCH wall thickness, material grade, and flange sealing face are high-frequency error-prone parameters. Practitioners must abandon the mindset of domestic procurement experience and must not arbitrarily substitute parameters across standards as equivalents.A complete closed-loop process for parameter identification, including extraction, comparison, clarification, consolidation, technical briefing, and factory re-inspection, ensures consistency of parameters among drawings, orders, physical goods, and documentation.
As domestically produced piping and fittings continue to enter the global supply chains of oil and gas, LNG, offshore engineering, and new energy EPC projects, the parameter complexity of foreign trade orders continues to increase.Domestic fitting enterprises must establish a systematic parameter identification system, strengthen technical personnel's ability to read drawings and verify parameters, and treat parameter identification as the first line of defense for order risk control, thereby reducing the risks of wrong materials, rejection, and claims caused by parameter misreading, and enhancing the contract performance capability and brand competitiveness of domestically produced pressure-bearing fittings in the international engineering market.
References
[1] ASME B16.5, Pipe Flanges and Flanged Fittings [S]. American Society of Mechanical Engineers.
[2] ASME B16.9, Factory-Made Wrought Buttwelding Fittings [S]. American Society of Mechanical Engineers.
[3] ASME B31.3, Process Piping Code [S]. American Society of Mechanical Engineers.
[4] ASME B36.10M, Metric Dimensions of Welded and Seamless Steel Pipe [S]. American Society of Mechanical Engineers.
[5] EN 10204:2004, Types of Inspection Documents for Metallic Products [S]. European Committee for Standardization.
[6] EN10253, Butt-Welding Pipe Fittings [S]. European Committee for Standardization.
[7] PED 2014/68/EU, EU Pressure Equipment Directive [S]. European Commission.
[8] ASTM A234/A234M, Specification for Carbon Steel and Alloy Steel Pipe Fittings for Moderate and High Temperature Service [S]. American Society for Testing and Materials.
[9] NACE MR0175, Material Requirements for Hydrogen Sulfide Service in Oil and Gas [S]. Association for Materials Protection and Performance.
[10] TSG 31-2025, Safety Technical Regulation for Industrial Piping [S]. Special Equipment Bureau of the State Administration for Market Regulation.
[11] GB/T 20801, Pressure piping code—Industrial piping [S]. National Technical Committee for Standardization of Pressure Piping.
[12] Li Xuedao. Practical Handbook on Foreign Trade Procurement and Quality Control of Pressure Piping Components [M]. Beijing: China Machine Press, 2023.
[13] Zhang Lei. Material Procurement Management for International EPC Projects [M]. Beijing: China Architecture & Building Press, 2022.
[14] Wang Jian. Research on Risk Control of Pipeline Material Procurement in International EPC Projects in the Oil and Gas Industry [J]. Petroleum Engineering Construction, 2024.
[15] China International Contractors Association. Report on Compliance Management of Overseas Engineering Supply Chains [R]. 2025.