I. Introduction
Industrial piping fittings include elbows, tees, reducers, caps, flanges, branch outlets, blind plates, and other pressure-bearing components, and are the core parts of fluid transportation systems for achieving direction changes, flow splitting, diameter reduction, sealing, and connection.Fitting selection cannot simply rely on general standards; the downstream application industry is the primary factor determining material grade, manufacturing process, non-destructive testing, quality assurance documentation, and certification access.For carbon steel elbows of the same specification, those used in long-distance oil and gas pipelines, power plant main steam pipelines, and municipal heating networks correspond to completely different design codes, inspection ratios, qualification requirements, and procurement costs, and cannot be directly interchanged.
From the perspective of the special equipment regulatory system, pressure piping is overall divided into four major categories: long-distance pipelines GA, public utility pipelines GB, industrial pipelines GC, and power pipelines GCD, corresponding to different industry scenarios.However, in engineering procurement, foreign trade business, and EPC project practice, classification is more often based on the end-use application industry.The medium hazard, service conditions, regulatory intensity, and owner technical habits of different industries form their own independent fitting access systems.Petrochemical and long-distance oil and gas transmission belong to high-hazard medium scenarios, where fittings are classified under GC1 high-grade pressure piping, and 100% non-destructive testing and complete heat-number traceability are mandatory requirements;Municipal water supply and drainage and ordinary circulating water pipeline working conditions are mild, inspection requirements are simplified, and more emphasis is placed on cost and delivery cycle;Emerging industries such as nuclear power, LNG, and hydrogen energy have a large number of special working conditions, imposing dedicated indicators on material toughness, cleanliness, and hydrogen embrittlement resistance.
In the foreign trade business of pipes and pipe fittings, industry attributes directly determine the applicable standard system: international EPC petrochemical projects in the Middle East and Southeast Asia generally adopt the ASME B31.3 process piping code;long-distance heat transmission projects in Russia and Central Asia implement the GOST system;power plant projects in Europe and the United States adopt ASME B31.1 power piping;marine engineering projects must meet the certification requirements of classification societies DNV and ABS.The root cause of many cross-border order disputes, on-site acceptance failures, and document rejections is that procurement personnel focus only on the external dimensions of pipe fittings, ignore the mandatory technical requirements of the industry to which they belong, and directly use general-purpose pipe fittings in high-risk and special working conditions.Therefore, systematically completing the division of application industries for industrial pipeline pipe fittings and clarifying the selection logic, inspection rules, and procurement boundaries of each industry is the foundational work of pipeline engineering technical management and foreign trade supply.
This article divides downstream applications into eight major sectors: the petrochemical and long-distance oil and gas pipeline industry, the power industry (thermal power/nuclear power), the municipal public utility industry, the ship and marine engineering industry, the new energy industry, the metallurgical and mining industry, the pharmaceutical and food light industry, and the general industrial supporting industry. It elaborates one by one on the pipeline operating condition characteristics, pipe fitting selection features, applicable standards, procurement control key points, and foreign trade export characteristics of each industry, analyzes the core differences between industries, and summarizes risk prevention and control strategies for cross-industry selection, procurement, and supply.
II. Petrochemical and Long-Distance Oil and Gas Pipeline Industry
The petrochemical industry is the largest demand market for pipeline fittings, covering subdivided scenarios such as refinery units, ethylene cracking, chemical plant process pipelines, oil and gas field gathering and transportation, long-distance oil and gas pipelines, and LNG receiving terminals. The media include crude oil, natural gas, liquefied hydrocarbons, and various highly corrosive chemical raw materials. The media are flammable and explosive, with high toxicity risks. Pipeline classes are mostly GC1 pressure pipelines, making this one of the industries with the strictest pipe fitting quality control.
Petrochemical process pipelines implement the ASME B31.3 Process Piping Code, and domestic projects implement the GB/T 20801 Pressure Piping Code.Pipe fittings are mainly seamless butt-welded elbows, tees, reducers, and butt-welded flanges, with forged socket-welded fittings and branch outlets for small-diameter instrument pipelines.Conventional carbon steel pipe fittings use A234 WPB material;high-temperature cracking pipelines use alloy pipe fittings such as A234 WP11 and WP22;corrosive media use 304/316L stainless steel, and highly corrosive scenarios use duplex stainless steel 2205.Flanges in high-pressure oil and gas projects mostly use RTJ ring joint sealing faces to meet high-pressure and severe temperature cycling conditions.
Long-distance oil and gas pipelines belong to GA-class long-distance pipelines, mainly transporting crude oil and natural gas. Pipe fittings are mainly large-diameter thick-wall butt-welded elbows and tees, implemented to API 5L and GB/T 9711 standards, with emphasis on impact toughness and fracture resistance. Pipe fittings need to be accompanied by drop weight tear tests.LNG receiving terminals operate under low-temperature conditions, using low-temperature carbon steel pipe fittings such as WPL6, with mandatory low-temperature impact tests to control the low-temperature toughness of materials and prevent low-temperature brittle fracture.
Key points for procurement and foreign trade: petrochemical projects generally require EN10204 3.1 or 3.2 material certificates, full-chain traceability of heat numbers, and 100% UT and MT non-destructive testing for pipe fittings used in high-pressure and flammable media;Large international EPC projects will arrange third-party supervision, with on-site witnessing of the entire process of raw material re-inspection, heat treatment, and flaw detection.Foreign trade exports to petrochemical projects in the Middle East and Southeast Asia are mainly ASME-system products, while oil and gas projects in Russia and Central Asia require GOST-standard pipe fittings, and documentation needs to be provided in foreign language versions.This industry prohibits arbitrary material substitution; any change in material or process must be approved in writing by the owner and the design party.The main risks in the industry are concentrated in material downgrading, negative wall thickness deviation, missing heat treatment, and falsified flaw detection reports. Once on-site sampling inspection fails, it will result in rejection of the entire batch and huge claims.
III. Power Industry: Pipe Fittings for Thermal Power and Nuclear Power Pipelines
The power industry is divided into two major sub-sectors: thermal power generation and nuclear power. Power piping is classified as GCD category pressure piping, mainly consisting of high-temperature and high-pressure steam, feedwater, and condensate pipelines, and is a core application market for alloy pipe fittings.
The main steam and reheat steam pipelines of thermal power plant boilers have long been in service under high-temperature and high-pressure conditions, posing a risk of creep failure. Pipe fittings extensively use heat-resistant alloy steel butt-welded elbows and tees made of P91, P92, 12Cr1MoV, etc.After forming, such pipe fittings must strictly undergo post-weld heat treatment to eliminate residual stress. Heat treatment curves and hardness inspection records are mandatory documents for supervisory inspection.The operating conditions of feedwater and circulating water systems are relatively mild, mostly using 20# and A234 WPB carbon steel pipe fittings, while ordinary stainless steel pipe fittings are used in demineralized water systems.Thermal power plant piping follows the ASME B31.1 Power Piping Code, while domestic projects follow the DL/T electric power industry piping code.
Nuclear power pipeline pipe fittings are nuclear-grade pressure-bearing components, classified into nuclear classes 1, 2, and 3, with the highest safety level. Their design, manufacturing, inspection, and quality assurance systems implement nuclear safety regulations, and the requirements for material purity, fatigue performance, non-destructive testing, and cleanliness far exceed those of ordinary industrial piping.Nuclear-grade pipe fittings have numerous raw material re-inspection items, and full-process quality records are permanently archived. Manufacturing enterprises must possess nuclear-grade component manufacturing qualifications, making the entry threshold extremely high and the number of suppliers very small.Pipe fittings for nuclear power projects are not allowed to use rolled and welded structures; all are made of seamless forged forming. The documentation system is extensive, and third-party supervision runs through all production processes.
Key points for procurement and foreign trade: The procurement of alloy pipe fittings for thermal power focuses on controlling heat treatment processes and hardness indicators, and spectral re-inspection of alloy materials cannot be omitted;Supplier admission for nuclear power projects is extremely strict, requiring qualification review, performance evaluation, and quality assurance system audit to be completed in advance.For foreign trade overseas power station projects, American standard power station pipe fittings are based on ASME B31.1, and the pound class and SCH wall thickness systems must match the design documents.The procurement list of pipe fittings for the power industry has high requirements for completeness as a set. Main pipeline pipe fittings, flanges, gaskets, and bolts are supplied as a unified matching set, with consistent materials and pressure ratings, and it is strictly prohibited to mix products of different standards.
IV. Pipeline Pipe Fittings for the Municipal Public Utilities Industry
The municipal public utilities industry includes urban heating thermal pipe networks, urban gas, municipal water supply and drainage, and sewage treatment. It belongs to public pressure pipelines GB1 (gas) and GB2 (heating), and is the civil industrial field with the largest demand for pipe fittings in China. Overseas municipal infrastructure projects under the Belt and Road Initiative are also a main track for pipe fitting foreign trade.
Urban heating thermal pipelines transport high-temperature hot water and saturated steam, and the medium temperature is relatively high. They are mainly 20# carbon steel seamless elbows, tees, and pre-insulated pipe fittings, and some high-temperature primary networks use low-alloy pipe fittings.Pipe fittings for heating networks focus on high-temperature creep performance and weldability, and buried pipeline fittings require accompanying anti-corrosion treatment.Urban gas pipelines belong to GB1 category pipelines, and the medium is flammable and explosive; seamless formed structures are selected for pipe fittings, and rolled fittings may be used for large-diameter low-pressure pipelines, but strict flaw detection is mandatory and defects exceeding standards are not allowed.Municipal water supply and drainage and sewage treatment conditions involve normal temperature and low pressure, the medium is mainly water, and corrosiveness is relatively low; pipe fittings are mainly carbon steel, stainless steel, and ductile iron fittings, large-diameter rolled fittings are widely used, and procurement focuses more on cost, delivery cycle, and anti-corrosion performance.
Procurement and foreign trade key points: pressure ratings for municipal projects are generally lower than those for petrochemical and power plant projects, inspection items are simplified, sampling inspection mode is generally adopted, demand for 3.2 certificates is relatively low, and most only require 3.1 material certificates.Export orders for municipal projects in Southeast Asia, Africa, and Central Asia are large in volume and highly price-sensitive, and customers mainly use general carbon steel pipe fittings conforming to national standards and American standards.The risk points in this industry are concentrated in anti-corrosion failure of buried pipe fittings and excessive negative wall thickness deviation; gas pipelines must not use rolled fittings with defects exceeding standards.Municipal projects have many non-standard large-diameter pipe fittings, and drawing conversion and dimension verification are key tasks in the early stage of procurement.
V. Pipes and Pipe Fittings for the Shipbuilding and Marine Engineering Industry
Marine and offshore engineering pipe fittings are divided into ship engine room process pipelines, seawater cooling pipelines, and offshore platform oil and gas process pipelines. The industry independently adopts classification society rules, such as DNV, ABS, LR, etc., which are different from conventional onshore industrial pipeline standards and constitute a distinctive export track.
Marine pipeline media include seawater, fuel oil, steam, compressed air, and firefighting water.Seawater cooling pipelines are in long-term contact with high-chloride-ion seawater, so copper-nickel alloy and 316L stainless steel pipe fittings are preferred to resist seawater pitting corrosion;Pipe fittings for fuel oil and combustible media pipelines have high pressure-bearing requirements, so carbon steel seamless butt-welded pipe fittings are used;Small-diameter instrument pipelines in the engine room use forged socket-welded pipe fittings.Offshore oil and gas platforms are offshore high-risk operating conditions, simultaneously subjected to media corrosion, marine atmospheric corrosion, and alternating wind and wave loads. Pipe fittings need to balance pressure-bearing, corrosion resistance, and fatigue resistance, and comply with ASME B31.3 plus additional classification society inspection requirements.LNG carrier supporting low-temperature pipe fittings have strict requirements for low-temperature impact toughness.
Procurement and foreign trade key points: marine and offshore engineering pipe fittings must pass the corresponding classification society certification, products must be stamped with the classification society steel stamp, and inspection certificates need classification society approval.Foreign trade orders are the main market for this industry. The documentation system for exported marine pipe fittings is complex; in addition to material certificates, classification society certificates are required.Industry selection taboo: ordinary carbon steel pipe fittings must not be used directly in seawater pipelines;The dimensional tolerances, bevels, and cleanliness requirements for marine pipe fittings are higher than those for onshore pipelines. Transport protection focuses on protecting bevels and sealing surfaces to prevent impact damage and corrosion.Ship project piping spaces are compact, with a large number of non-standard pipe fittings. Single-line drawings are complex, and procurement lists are prone to omissions.
VI. Pipes and Fittings for the New Energy Industry
New energy is a fast-growing emerging track, including hydrogen energy storage and transportation, CCUS carbon dioxide capture and transport, LNG, solar thermal, and energy storage supporting pipelines. The growth rate of the pipe fittings market is significantly higher than that of traditional industries, making it a high-value-added segmented market.
Hydrogen energy pipeline fittings are divided into gaseous high-pressure hydrogen transport and liquid hydrogen cryogenic pipelines.Hydrogen carries the risk of hydrogen embrittlement. Ordinary carbon steel is strictly prohibited for high-pressure hydrogen pipelines; hydrogen-embrittlement-resistant special materials are used, the interior of fittings undergoes degreasing treatment, impurities are controlled, and pipeline cleanliness requirements are high.CCUS carbon dioxide transmission pipelines: the medium is subject to acidic corrosion, so the material of pipe fittings and the welding process need to take stress corrosion into consideration.Concentrated solar power plant molten salt pipelines: for long-term high-temperature service, high-temperature-resistant alloy pipe fittings are selected.LNG low-temperature pipeline fittings: the core indicator is low-temperature impact toughness; WPL6 low-temperature carbon steel and austenitic stainless steel are the mainstream choices, and pipe fittings must be strictly prevented from brittle fracture at low temperatures.
Key points for procurement and foreign trade: new energy projects are mostly newly built demonstration projects, and the project standard system is still in the development stage; many operating conditions lack mature general experience, so the technical agreement needs to clearly specify inspection items one by one.For hydrogen energy and liquid hydrogen pipe fitting procurement, in addition to conventional non-destructive testing, degreasing and cleanliness testing are additionally added.Overseas new energy EPC projects mostly adopt ASME international standards, and certification and carbon compliance requirements are gradually increasing.The supplier threshold in this industry is high, the number of domestic enterprises with a full set of inspection capabilities is limited, the raw material procurement cycle is long, and delivery risk is higher than that of ordinary carbon steel pipe fittings.
VII. Pipeline and Pipe Fittings for the Metallurgical and Mining Industry
The metallurgical and mining industry includes steel smelting, ore beneficiation, slurry transportation, and dust removal pipe networks. The media are characterized by high-temperature flue gas, slurry, particle-containing abrasive media, and acid-base wastewater. Pipe fitting selection focuses on wear resistance, high-temperature resistance, and erosion resistance.
For high-temperature flue gas pipelines of steel blast furnaces and heating furnaces, heat-resistant carbon steel pipe fittings and alloy pipe fittings are used;The medium in slurry transportation pipelines contains solid particles, and elbows and tees suffer severe erosion and wear. Wear-resistant composite pipe fittings with a ceramic wear-resistant lining are widely used to extend service life.For acid-base wastewater pipelines in ore beneficiation, 304 and 316L stainless steel pipe fittings are selected to resist acid-base corrosion.The pressure rating of mine pipelines is generally not high, but the wear problem is prominent, and failure locations are concentrated in the fluid diversion areas of elbows and tees.
Procurement and foreign trade key points: Metallurgical and mining pipe fittings do not necessarily pursue high pressure ratings; wear resistance is the primary indicator. The procurement technical agreement must clearly specify the thickness of the wear-resistant layer and the wear resistance testing method.Overseas mining projects are concentrated in Africa and Southeast Asia. Orders are mainly large-diameter rolled pipe fittings and wear-resistant pipe fittings. Inspection focuses on appearance, wear-resistant layer, and weld seam flaw detection, with less demand for expensive 3.2 certificates.Common industry risk: Ordinary carbon steel pipe fittings are directly used for slurry transportation and are eroded through in a short time, causing pipeline shutdown.
VIII. Piping and fittings for the pharmaceutical, food, and light industries
In the pharmaceutical and food industries, pipelines transport pure water, medicinal liquids, and food fluids. The medium pressure is generally not high, but there are mandatory requirements for cleanliness, surface roughness, no precipitation, and hygiene grade. The industry customarily calls these sanitary-grade fittings, which belong to a special subdivided category.
For food and beverage and biopharmaceutical process piping and fittings, 304 and 316L stainless steel are mostly selected, with internal and external polishing treatment to reduce medium adhesion and microbial growth;The groove and inner surface of fittings need controlled roughness, and welds are required to be smooth inside and outside, with no dead corners, for easy cleaning and disinfection.Oxygen pipeline fittings are special light-industry supporting fittings and must undergo strict degreasing treatment to remove grease and prevent explosion risks.
Procurement and foreign trade key points: fittings in this industry have low pressure-bearing requirements, but surface treatment, cleanliness, and degreasing are core acceptance items.For export of fittings supporting pharmaceutical and food equipment, material certificates and surface inspection reports must be provided; some overseas customers require FDA material certification.Ordinary industrial stainless steel fittings are strictly prohibited from being directly used in food and pharmaceutical pipelines; ordinary fittings have rough inner surfaces and carry hidden risks of residue and contamination.
IX. Pipes and Fittings for the General Industrial Supporting Industry
The general industrial sector includes factory compressed air, circulating cooling water, heating, and ordinary process auxiliary pipelines. The operating conditions are mild, with low pressure and temperature, and the media are room-temperature air and clean water. The fittings are mainly conventional carbon steel and stainless steel standard parts, making this the category with the largest market stock and the fiercest competition.Most of these pipelines belong to GC2 level, with simplified inspection items focusing mainly on appearance, dimensions, and material verification; generally, 100% non-destructive testing is not required.
The project characteristics of this industry are scattered specifications and many small-batch orders, with spot purchasing as the main approach. Customers prioritize price and delivery speed, and have low requirements for high-level certificates and third-party supervision.Foreign trade export orders are mostly supporting overseas small processing plants, spread across Southeast Asia and Africa, mainly standard spot elbows and flanges conforming to GB and American standards.Procurement risks are mainly concentrated in: customers mistakenly substituting general-purpose fittings into high-temperature, flammable, high-risk process pipelines, creating safety hazards.Procurement personnel must properly identify operating conditions, clearly distinguish utility auxiliary pipelines from high-risk process pipelines, and must not select based solely on pipeline appearance.
X. Pipe Fitting Procurement and Foreign Trade Control Strategies for Different Industries
10.1 Industry-tiered access, establishing a differentiated supplier system
According to industry risk levels, downstream industries are divided into high-risk high-regulation industries (petrochemical, oil and gas, nuclear power), medium-high risk industries (thermal power, offshore engineering, LNG, hydrogen energy), conventional industries (municipal, metallurgy), and clean low-pressure industries (food and pharmaceuticals, general factories).Establish a tiered supplier access system: for nuclear power and petrochemical GC1 projects, suppliers must possess special equipment manufacturing qualifications, the ASME stamp, and a complete NDE non-destructive testing team;For municipal and general low-pressure projects, the supplier qualification threshold may be appropriately relaxed, but material and basic inspection compliance must be guaranteed.In foreign trade business, pre-audit the enterprise's international certifications for the target export industry, such as PED, ASME, and classification society certificates, to avoid qualification deficiencies during the project bidding stage.
10.2 Locking down technical agreement clauses with industry specifications
For the same pipe fitting, different application industries have completely different mandatory standards, test items, and warranty documentation.During the inquiry and technical negotiation stages, first confirm the industry to which the project belongs, extract the corresponding industry design specifications, and write them into the technical agreement.Petrochemical projects explicitly specify ASME B31.3;power plant power piping adopts B31.1;marine projects add classification society inspection clauses;food and pharmaceutical projects add internal polishing and clean degreasing clauses.The technical agreement states that arbitrary material substitution across industries is not permitted, and all changes must be approved in writing by the design party and the owner, to avoid quality disputes caused by selection errors.
10.3 Inspection plans are configured differently according to industry risks
High-risk industries such as GC1, nuclear power, and offshore engineering pipe fittings implement 100% non-destructive testing, spectral re-inspection of raw materials, and third-party supervision;municipal and general low-pressure pipelines adopt sampling inspection;For food and pharmaceutical pipe fittings, inspection focuses on surface roughness, cleanliness, and degreasing effectiveness, while non-destructive testing requirements are reduced.For pre-shipment acceptance of foreign trade orders, strictly match the inspection checklist of the target industry, prepare certificate types and document language versions according to the owner's requirements, and ensure a complete closed loop of MTC material certificates, flaw detection reports, and heat treatment records.
10.4 Matching foreign trade market layout with industry demand characteristics
Overseas EPC projects in petrochemicals and large power plants are concentrated in the Middle East and Central Asia, with huge order volumes and high technical thresholds, suitable for enterprises with ASME qualifications and supervision support capabilities;Municipal infrastructure orders are concentrated in Southeast Asia and Africa, with demand mainly for conventional carbon steel standard pipe fittings and intense price competition;Shipbuilding and offshore engineering orders belong to a specialized niche track, where customers value classification society certification;New energy hydrogen and LNG projects belong to emerging tracks with high added value and year-on-year order growth, representing the direction for the transformation and upgrading of pipe fitting foreign trade.Enterprises can select advantageous industry tracks based on their own manufacturing capabilities to avoid homogeneous low-price competition across all industries.
XI. Analysis of Common Selection Misconceptions from the Perspective of Industry Classification
Misconception 1: Only looking at pressure and nominal size, ignoring industry-specific medium characteristics.Many procurement personnel only verify nominal pressure and dimensions, using ordinary carbon steel pipe fittings for hydrogen, seawater, and low-temperature LNG pipelines, ignoring industry-specific failure risks such as hydrogen embrittlement, chloride ion corrosion, and low-temperature brittleness, thereby planting hidden safety hazards.
Misconception 2: Arbitrarily making equivalent substitutions across industry standards.Using municipal pipeline fittings directly for petrochemical GC1 process pipelines, or using onshore industrial fittings directly for marine seawater pipelines—the requirements of different industry design codes for fitting manufacturing processes and inspection ratios cannot be automatically treated as equivalent, and substitution is not permitted without written confirmation from the designer.
Misconception 3: The certification system does not match industry regulatory requirements.Ordinary municipal projects do not require 3.2 certificates, but petrochemical, nuclear power, and offshore engineering projects mandatorily require high-grade material certificates;Food and pharmaceutical projects require cleanliness reports, and ordinary industrial fitting certificates cannot satisfy acceptance requirements.In foreign trade orders, the certificate type often fails to comply with the overseas owner's industry specifications, resulting in the rejection of documentation.
Misconception 4: Ignoring special additional requirements of the industry.For example, degreasing of oxygen pipelines, nuclear power cleanliness, marine classification society steel stamping, and heat treatment of alloy pipe fittings—these are not basic general parameters of pipe fittings, but mandatory additional requirements specific to certain industries; omissions in the technical agreement will lead to on-site acceptance failure.
XII. Conclusion
The downstream application industries of industrial pipeline fittings can be divided into eight major sectors: petrochemicals, oil and gas; power, thermal power, and nuclear power; municipal utilities; shipbuilding and marine engineering; new energy; metallurgy and mining; pharmaceuticals, food, and light industry; and general industry.There are huge differences among industries in terms of medium hazard, temperature and pressure, corrosion and wear, and safety regulatory systems, which directly determine the requirements for fitting material, forming process, non-destructive testing, quality traceability, certification qualifications, and warranty documentation.Petrochemical, nuclear power, and marine engineering are high-risk industries, with the most stringent quality control for pipe fittings;Municipal and general industrial operating conditions are relatively mild, and procurement focuses more on cost and delivery;New energy sectors such as hydrogen energy and LNG, as emerging industries, carry relatively high added value and are new growth points for the pipe fittings industry.
In engineering procurement, EPC projects, and foreign trade export business, the primary task of selection is to identify the industry to which the project belongs and establish pipe fitting technical requirements based on the design codes corresponding to that industry; selection must not rely solely on the appearance or nominal pressure of the pipe fittings.Enterprises should establish a tiered supplier admission, differentiated inspection, and technical agreement control system according to downstream industries, and formulate procurement lists, factory documentation, and packaging and protection plans for different industries.Accurately identifying differences in industry requirements and avoiding cross-industry selection errors will help reduce project quality risks, improve the ability to fulfill overseas project contracts, enable domestic pipe fitting manufacturers to better serve domestic engineering and the global foreign trade market, and achieve high-quality development of the industry.
References
[1] TSG 31-2025, Industrial Piping Safety Technical Regulation [S]. Special Equipment Bureau of the State Administration for Market Regulation, 2025.
[2] GB/T 20801, Pressure Piping Code — Industrial Piping [S]. National Technical Committee for Standardization of Pressure Piping.
[3] GB/T 12459-2017, Steel Butt-Welding Pipe Fittings — Types and Parameters [S]. National Technical Committee for Standardization of Pipe Accessories.
[4] ASME B31.3, Process Piping Code [S]. American Society of Mechanical Engineers.
[5] ASME B31.1, Power Piping Code [S]. American Society of Mechanical Engineers.
[6] ASME B16.9, Factory-Made Wrought Butt-Welding Fittings [S]. American Society of Mechanical Engineers.
[7] GB 50316, Code for Design of Industrial Metallic Piping [S]. China Planning Press.
[8] DNV-OS-F101, Submarine Pipeline Systems Code [S]. Det Norske Veritas.
[9] Li Xuedao. Practical Guide to Foreign Trade Procurement and Quality Control of Pressure Piping Components [M]. Beijing: China Machine Press, 2023.
[10] Lange Steel Research Center. Research Report on Downstream Industry Demand for Steel Pipe Fittings [R]. 2025.
[11] National Energy Administration. Technical Guidelines for Pressure Piping in Thermal Power Plants [S]. China Electric Power Press.
[12] GB 50028, Code for design of city gas engineering [S]. China Architecture & Building Press.