The standard system for pipe fittings is highly complex, with corresponding specifications for different countries, industries, and connection methods. For ease of reference and application, they are generally categorized into two major groups: international common standards (American, European, and Japanese standards) and domestic standards (Chinese national, petrochemical, and chemical industry standards). Below is a summary of the most commonly used pipe fitting standards in current engineering projects:

I. International Common Standards

1. American Standards (ASME / ANSI / ASTM)

The American standard system is the most widely used in petroleum, natural gas, chemical engineering, and international trade.

• ASME B16.9: Factory-made wrought steel butt-welding fittings(The most commonly used standard, covering elbows, tees, reducers, etc., for sizes 4 inches and larger.)
• ASME B16.11: Forged fittings, socket-welding and threaded(Covers small-bore high-pressure fittings such as socket elbows and threaded tees.)
• ASME B16.28: Wrought steel butt-welding short radius elbows(Standard specifically for short-radius elbows.)
• ASME B16.5: Pipe flanges and flanged fittings(Although focused on flanges, it also includes relevant dimensions for flange connections.)
• MSS SP-43: Stainless steel butt-welding fittings.
• MSS SP-79 / 83 / 95 / 97: Standards for socket-welding, threaded, butt-welding and other types of fittings respectively.

2. European Standards (EN / DIN)

The European system differs from the American system in mechanical strength calculation and material classification.

• EN 10253: Steel butt-welding pipe fittings(Divided into several parts; e.g., EN 10253-2 for carbon steel and EN 10253-4 for stainless steel.)
• EN 10241: Threaded and socket-welding pipe fittings.
• DIN 2605 / DIN 2615: German industrial standards, widely used in older versions. Now mostly replaced by EN standards, but still applied in some German-invested enterprises.

3. Japanese Standards (JIS)

• JIS B2311: General steel butt-welding pipe fittings.
• JIS B2312: Steel butt-welding pipe fittings (high pressure).
• JIS B2313: Steel plate butt-welding pipe fittings.
• JIS B2316: Socket-welding and threaded pipe fittings.

II. Chinese National Standards (GB)

Chinese national standards (GB/T) serve as the basic specifications for domestic engineering projects.

• GB/T 12459: Steel butt-welding seamless pipe fittings(The most commonly used Chinese standard for seamless pipe fittings.)
• GB/T 13401: Steel plate butt-welding pipe fittings(Used for large-diameter or non-standard fittings fabricated by rolling and welding steel plates.)
• GB/T 14383: Forged steel socket-welding and threaded pipe fittings(Small-bore high-pressure fittings.)
• GB/T 10752: Butt-welding joints of steel pipes for ships(Specifically for the marine industry.)
• GB/T 8803: Injection-moulded fittings of unplasticized poly(vinyl chloride) (PVC-U), chlorinated poly(vinyl chloride) (PVC-C), acrylonitrile-butadiene-styrene (ABS) and poly(vinylidene fluoride) (PVDF)(Standard for plastic pipe fittings.)

III. Industry-Specific Standards

In China, specific industries have stricter or more detailed implementation standards.

1. Petrochemical Industry (SH)

Developed by Sinopec, these standards are generally more stringent than national standards and apply to oil refining and chemical plants.

• SH/T 3408: Steel butt-welding seamless pipe fittings.
• SH/T 3409: Steel plate butt-welding pipe fittings.
• SH/T 3410: Forged steel socket-welding and threaded pipe fittings.

2. Chemical Industry (HG)

Formulated by the Ministry of Chemical Industry, focusing on corrosion resistance and chemical processes.

• HG/T 20592: Steel pipe flanges, gaskets and fasteners(Although mainly for flanges, it provides dimensional benchmarks for flange connections.)
• HG/T 21635: Steel butt-welding seamless pipe fittings (Series I).
• HG/T 21631: Steel welded butt-welding pipe fittings.

3. Electric Power Industry (DL)

Applicable to piping systems in power plants and substations.

• DL/T 695: Steel butt-welding pipe fittings for power stations.
• DL/T 515: Bends for power stations.

4. Gas Industry (CJ)

Used for urban gas transmission and distribution pipelines.

• CJ/T 152: Aluminum alloy plastic-lined composite pipes and fittings.
• CJ/T 270: Mechanical fittings for polyethylene (PE) piping systems for town gas.

IV. Material Standards (Associated Standards)

The manufacture of pipe fittings relies on material standards, which are usually cited simultaneously during procurement.

• ASTM A234: American standard for carbon and alloy steel butt-welding fitting materials (e.g., WPB, WP11).
• ASTM A403: American standard for stainless steel butt-welding fitting materials (e.g., WP304, WP316L).
• ASTM A182: American standard for forged fitting materials (flanges, socket-welding fittings) (e.g., F304, F316).
• GB/T 1220: Chinese standard for stainless steel bars.
• GB/T 8163: Seamless steel pipes for fluid transport(Commonly used as raw material for pipe fittings).

Summary

In practical engineering, a complete procurement description consists of standard number + model + material.Example: GB/T 12459-2017, DN100 Sch40, 20# 90° Elbow. The three most commonly used core standards are:

• GB/T 12459 (Chinese seamless fittings)
• ASME B16.9 (American butt-welding fittings)
• ASME B16.11 (American socket / threaded fittings)