I. Introduction
In the procurement chain of pressure piping EPC general contracting, technical transformation, and overseas implementation projects, the procurement contract is divided into two components: the commercial contract and the technical agreement.The commercial contract stipulates price, delivery time, payment, and liability for breach of contract;the technical agreement, on the other hand, carries all technical boundaries, quality baselines, and acceptance rules, and is the core technical basis for supplier manufacturing, supervision and inspection, owner acceptance, and verification by special equipment supervision and inspection agencies, and has equal binding force.TSG 31-2025 "Safety Technical Regulation for Industrial Piping" clearly stipulates that the procurement of pressure piping components must specify material, manufacturing, inspection, and traceability requirements, and the relevant technical agreements shall be documented in writing as supporting documentation for the quality certification documents.
Several typical problems commonly exist in procurement practice: first, the technical agreement copies a generic template, merely marking "manufactured according to national standards," and lacks the standard year designation, operating condition boundaries, and additional test requirements;second, standard components and non-standard pipe fittings are stipulated in a mixed manner, and non-standard pipe fittings do not specify strength calculation and review requirements;third, non-destructive testing, heat treatment, and hydrostatic testing only list the items without specifying the applicable standards, qualification grades, and sampling ratios;Fourth, the data delivery clauses are too general, lacking requirements on the number of copies, format, and stamping for MTR material certificates, NDT reports, and inspection certificates;Fifth, the priority of document conflicts is not agreed upon, and there is no basis for judgment when drawings, inquiry documents, technical agreements, and supplier quotations contradict each other.Once there are loopholes in the clauses, it is very easy for suppliers to "supply according to the lowest standard"; after arrival, the material, wall thickness, inspection items, and data may fail to meet the supervision and inspection filing requirements, causing returns, rework, schedule delays, and economic losses.
The technical agreement is not a formal document, but a tool for upfront control of procurement risks.This article breaks down the core clauses of the technical agreement for pipeline fittings procurement item by item, explains the meaning of the clauses, key writing points, and common blind spots, and distinguishes clause differences among different systems such as national standards and American standards, standard parts and non-standard parts, and domestic projects and cross-border foreign trade projects, helping procurement, technical, and supervision personnel unify control standards.
II. Document Priority Clause: The General Outline of the Technical Agreement
Document priority is the first clause at the beginning of the technical agreement. It is used to clarify the order of determination when drawings, technical agreements, inquiry documents, relevant specifications, and supplier documents conflict, and it is also the first basis for resolving later disputes.The conventional priority order is generally: national special equipment regulations, project design drawings, this technical agreement, project specifications, referenced standards and specifications, and supplier technical documents.The clause must specify that, after receiving the documents, if the supplier discovers contradictions or doubts in drawing parameters, standard systems, or technical requirements, it must submit a written clarification sheet to procurement or design for confirmation within the specified time limit, and must not interpret on its own, modify parameters on its own, or select approximate specifications on its own.
High-frequency loopholes in this clause: the standard version year is not marked, and only GB/T12459 or ASME B16.9 is written, while differences exist between old and new versions in dimensions, tolerances, and inspection rules;In foreign-related projects, multiple sets of standards exist at the same time, and the governing execution system is not clearly defined. For example, for transition fittings with an ASME flange at one end and a national standard flange at the other end, there is no agreement on which set of specifications should be used as the basis for strength verification when conflicts arise.Supplementary control points: all referenced standards and specifications must be marked with the complete number and year of publication;For fittings connecting mixed standards, an additional note shall be added to this clause: the overall strength and sealing verification shall be based on the project's main governing specification, and the flange dimensions shall respectively correspond to their own finished product standards.
III. Working Conditions, Standards, and Specification Clauses
Working conditions are the underlying basis of all technical requirements and must be clearly written into the technical agreement; drawings must not be assumed by default to be the sole source of working conditions.The clause content includes pipeline GC classification, design pressure, design temperature, operating condition range, medium composition, corrosion type, corrosion allowance, whether there are severe cyclic loads, low-temperature impact, hydrogen service, hydrogen sulfide stress corrosion, and other special requirements.Once the operating condition boundaries are locked, further specify the fitting type, nominal size DN/NPS, wall thickness SCH, pressure rating Class/PN, fitting structural form (elbow, tee, reducer, branch outlet, flange, etc.), sealing face form, and the requirements for matching gaskets and fasteners.
The clauses of the standard system distinguish between standard fittings and non-standard fittings.For standard fittings, specify the finished fitting standards, such as GB/T12459, ASME B16.9, and EN10253;For non-standard fittings, it must be clearly stated: manufactured according to drawing XX, with strength verification carried out in accordance with GB/T20801, together with the supporting strength calculation report and the opening reinforcement review record.A pitfall that very easily occurs here: writing non-standard fittings into the clauses for finished product standards, which leads the supervision and inspection agency to determine that the documents are contradictory;Or, in the agreement for standard fittings, allowing the supplier to freely select approximate substitute specifications.The agreement should clearly state: without written design approval for material substitution, the supplier must not change the material, wall thickness, pressure rating, or structural form.
IV. Material and material traceability clauses
The material clause is the core of pressure piping safety control, and TSG 31-2025 has mandatory requirements for the traceability of materials used in pressure-bearing components.The clause content includes base metal grade, base metal implementation standard, steel mill scope, smelting method (killed steel, electric furnace steel, etc.), chemical composition, mechanical properties, heat treatment condition, and additional test items: low-temperature Charpy impact, intergranular corrosion, HIC hydrogen-induced cracking resistance, PMI spectral re-inspection, etc.For foreign trade projects, the material certificate level should also be specified, such as EN10204 3.1 and 3.2 certificate requirements.
Traceability requirements must be clearly stated: the content of the steel stamp marking on each pipe fitting, the stamp position (avoiding high-stress areas), and the one-to-one correspondence of heat number, melt number, and serial number;The heat number on the material certificate must fully match the steel stamp on the actual item, with one certificate per batch; merging certificates for multiple heat numbers and disconnection between certificates and actual items are prohibited.Stainless steel pipe fittings require additional clauses for iron ion contamination control, as well as isolation requirements for storage, processing, and packaging.Clause loopholes are mainly reflected as follows: only the material grade is specified, without additional tests;only a material certificate is required, without requiring one-to-one correspondence of heat numbers, making it impossible to complete special equipment traceability verification later.
V. Manufacturing, Forming, and Heat Treatment Process Clauses
This clause governs forming methods, welding, and heat treatment, and applies to various pipe fittings such as elbows, tees, forged flanges, and branch outlets.The forming clause specifies: the permitted scope of seamless pressing, pushing, forging, and welded forming, and restricts the use of cast pipe fittings and fabricated welded pipe fittings;Control indicators for elbow wall thickness reduction rate, control range for reducer cone angle, bevel forms, bevel processing precision, end face flatness, and dimensional tolerance execution standards.
The welding clause stipulates WPS/PQR welding procedure qualification requirements; the supplier must possess valid qualifications covering the material, thickness, and welding form;Welding without qualification is not permitted, and repair welding is likewise subject to qualification control.The heat treatment clause specifies whether normalizing, tempering, solution treatment, or stress relief heat treatment is required, the delivery requirements for heat treatment curve records, and the sampling inspection rules for hardness testing after heat treatment.For stainless steel pipe fittings, sensitization heat treatment is explicitly prohibited to avoid the risk of intergranular corrosion.Many procurement agreements omit heat treatment details, and suppliers simplify heat treatment processes, resulting in material mechanical properties failing to meet standards and early failure under high-temperature and corrosive working conditions.
VI. Inspection, Non-Destructive Testing and Pressure Test Clauses
Inspection clauses are the core of acceptance and also a high-incidence area for disputes; they cannot simply state "qualified upon inspection according to standards."The clauses are divided into four parts: appearance and dimension inspection, non-destructive testing (NDT), physical and chemical testing, and pressure testing.Clearly specify the non-destructive testing execution standard JB/T4730 or the corresponding ASME code, testing methods (RT/UT/MT/PT), testing proportion, acceptance level, and hold points.GC1 high-risk medium pipe fittings are often stipulated to undergo 100% non-destructive testing, while GC3 low-pressure non-toxic pipe fittings are sampled at the standard proportion;Forged flanges and branch outlets shall have additional UT ultrasonic testing requirements.
The hydrostatic/pneumatic tightness test clauses shall specify the test medium, test pressure, pressure holding time, test temperature, and drainage and drying requirements;The pressure test timing is scheduled after the completion of heat treatment and non-destructive testing.At the same time, the disposal rules for nonconforming items shall be agreed upon: the scope of repair, the maximum number of repairs, the re-inspection requirements after repair, and the isolation, re-inspection, and rejection mechanisms for nonconforming batches.Common loopholes: failing to distinguish the inspection ratio between standard parts and non-standard parts, applying sampling inspection for standard parts to non-standard high-risk pipe fittings, thereby lowering the inspection level;failing to agree on the third-party re-inspection authority, the re-inspection agency, and the rules for bearing re-inspection costs.
VII. Special Technical Clauses for Non-standard Pipe Fittings
Special clauses for non-standard pipe fittings should be set up separately in the agreement, and managed separately from standard pipe fittings.The clauses shall specify clearly: non-standard pipe fittings must be provided with design-approved drawings, strength calculation reports, and opening reinforcement verification reports;GC1-grade non-standard parts require third-party technical review or type test certificates;First article confirmation before manufacturing and first article inspection and sample sealing requirements;Non-standard parts cannot apply the inspection ratios and acceptance rules of finished pipe fittings; the inspection plan shall be prepared by the supplier and can only be implemented after confirmation by the purchaser and the supervisor.It is also agreed that any change to the structure, wall thickness, or reinforcement of non-standard drawings must be accompanied by a newly issued calculation report and completed approval, and the change documents shall serve as supplementary attachments to the technical agreement.
VIII. Clauses on Supervision, Marking, Packaging, and Document Delivery
The supervision clause stipulates the scope of supervision, hold points (H points), and witness points (W points); it clarifies that the owner or third-party supervision personnel have the right to enter the production site to verify raw materials, processes, and inspection records; the supplier shall cooperate with supervision and notify witness points in advance; without witness confirmation, the process shall not proceed to the next step.
The marking clause specifies the content of steel stamps and inkjet codes, marking positions, and low-stress stamping requirements; hard stamping that causes surface damage is prohibited for stainless steel;The packaging clause distinguishes the protection of carbon steel, stainless steel, and alloy pipe fittings; stainless steel shall be isolated in packaging, moisture-proof, and protected against impact, and the packing list and batch list shall correspond one-to-one with the actual items.
The document delivery clause is key to ensuring special equipment filing, and lists the delivery documents item by item: product certificate of conformity, MTR material certificates, heat treatment curves, non-destructive testing reports, pressure test records, supervision inspection certificates, non-standard part calculation reports and review records, and drawing versions;Agree on the number of document copies, the format of paper stamped versions plus electronic versions, the language versions (Chinese for domestic, Chinese-English bilingual for foreign trade), and the delivery milestones, and make it clear that delayed documents are deemed equivalent to delayed supply.For a large number of projects, the physical items are qualified but cannot be filed for acceptance; the root cause is the absence of document delivery clauses and the vague agreement on the document list.
IX. Clauses on Acceptance Objections, Quality Assurance, and Change Control
The clause on objections to acceptance upon arrival shall stipulate the arrival inspection period, the method for raising objections, the re-inspection process for objected samples, and the handling methods for nonconforming products (repair, replacement, rejection), and make it clear that if re-inspection fails, the re-inspection costs shall be borne by the supplier.The warranty clause shall specify the warranty period and warranty scope, and distinguish the boundaries between wear under normal operating conditions, medium corrosion, and manufacturing quality defects. If a manufacturing quality problem occurs during the warranty period, the supplier shall replace or repair it free of charge and bear the related downtime losses.
The change control clause shall stipulate the technical change process: any change in specifications, materials, structure, or inspection requirements must be issued as a written technical change order, signed and confirmed by design, procurement, and the owner, and serve as a supplementary document to the technical agreement;Oral changes are invalid; changes shall simultaneously adjust the quotation, delivery date, and inspection plan, so as to prevent the supplier from raising prices or reducing quality after making unauthorized changes.
X. Summary of High-Frequency Misunderstandings in the Preparation and Implementation of Technical Agreements
Misconception 1: The technical agreement directly copies a generic template, leaving working conditions, GC grade, additional tests, and standard versions all blank, so the supplier selects the lowest standard for supply.Prevention and control: Each project technical agreement must be bound to the project working conditions and drawing version, and the matching of medium risk levels with inspection requirements must be checked item by item.
Misconception 2: Standard parts and non-standard pipe fittings are mixed in the same clause, and non-standard parts lack strength calculations and review agreements, resulting in a determination of non-compliance during the supervision and inspection stage.Prevention and control: Within the agreement, separate chapters for standard parts and non-standard custom parts shall be divided, and control rules shall be agreed separately.
Misconception 3: Non-destructive testing only specifies the test items, without specifying the acceptance level, applicable standard, or testing proportion, leading to inconsistent understanding of the acceptance criteria between both parties.Prevention and control: Clearly specify the testing specification, acceptance level, which positions are to be 100% tested, and which are to be sampled at a specified proportion.
Misconception 4: The documentation clause only states “provide certificate of conformity,” without clarifying certificate type, heat number traceability, number of copies, stamping, or bilingual requirements, causing obstacles in foreign trade projects or domestic special equipment filing.Prevention and control: The document list shall be refined down to each type of report, with delivery deadlines clearly specified.
Misconception 5: The absence of a document conflict priority clause leads to mutual buck-passing when drawings, technical agreements, and standards contradict each other.Prevention and control: Establish the priority order at the outset and stipulate the supplier's obligation to clarify in advance.
XI. Conclusion
The technical agreement for pipeline and pipe fitting procurement is essentially the conversion of the pressure-bearing safety requirements of design drawings into implementable, verifiable, and accountable manufacturing and acceptance rules, and is the core vehicle for risk control in pressure piping procurement.Its core clauses comprise nine major modules: document priority, working condition standards and specifications, material traceability, manufacturing and heat treatment, inspection and testing, special control of non-standard items, supervision, marking and packaging, document delivery, and objections, warranty, and changes.Clause drafting should adhere to the principles of prioritizing working conditions, clear standards, clear boundaries, closed-loop documentation, and distinguishing standard parts from non-standard parts, and should eliminate vague and template-based wording.
A rigorous and complete technical agreement can unify the technical understanding of the four parties—the purchaser, the supervisor, the owner, and the manufacturing supplier—thereby avoiding major risks at the source, such as material mismatch, downgraded inspection, missing documents, and non-standard items without verification; reducing delivery disputes, failed pressure tests, rejected supervision inspections, and filing delays; and ensuring the safe and compliant delivery of various pressure piping projects in chemicals, oil and gas, new energy, power stations, and overseas EPC, while balancing procurement quality, safety risks, and project cost control objectives.
References
[1] TSG 31-2025, Safety Technical Regulation for Industrial Piping [S]. State Administration for Market Regulation, 2025.
[2] GB/T 20801-2020, Pressure Piping Code: Industrial Piping [S]. Beijing: Standards Press of China, 2020.
[3] GB/T 12459-2017, Steel Butt-Welding Seamless Pipe Fittings [S]. Beijing: Standards Press of China, 2017.
[4] HG/T 20592-2009, Steel Pipe Flanges, Gaskets and Fasteners [S]. Beijing: Chemical Industry Press, 2009.
[5] ASME B16.9-2021, Factory-Made Wrought Butt-Welding Fittings [S]. New York: ASME Press, 2021.
[6] TSG D7006-2023, Supervision and Inspection Rules for Pressure Piping Components [S]. State Administration for Market Regulation, 2023.
[7] Li Gang. Practical Guide to Design of Pressure Piping Components and Review of Non-Standard Parts [M]. Beijing: Atomic Energy Press, 2021.