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Pipe Fitting Standards

Some of the standards that apply to buttwelded fittings are listed below. Many organizations such as ASME, ASTM, ISO, MSS, etc. have very well developed standards and specifications for buttwelded fittings. It is always up to the designer to ensure that they are following the applicable standard and company specification, if available, during the design process.

Types of pipe fitting standards:

Some widely used pipe fitting standards are as follows:

ASME: 
American Society for Mechanical Engineers

This is one of the reputed organizations in the world developing codes and standards.

The schedule number for pipe fitting starts from ASME/ANSI B16. The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows:

• ASME/ANSI B16.1 - 1998 - Cast Iron Pipe Flanges and Flanged Fittings

• ASME/ANSI B16.3 - 1998 - Malleable Iron Threaded Fittings

• ASME/ANSI B16.4 - 1998 - Cast Iron Threaded Fittings

• ASME/ANSI B16.5 - 1996 - Pipe Flanges and Flanged Fittings

• ASME/ANSI B16.11 - 2001 - Forged Steel Fittings, Socket-Welding and Threaded

• ASME/ANSI B16.14 - 1991 - Ferrous Pipe Plugs, Bushings and Locknuts with Pipe Threads

• ASME/ANSI B16.15 - 1985 (R1994) - Cast Bronze Threaded Fittings

• ASME/ANSI B16.25 - 1997 - Buttwelding Ends

• ASME/ANSI B16.36 - 1996 - Orifice Flanges etc.

ASTM International:
American Society for Testing and Materials

This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM).

• ASTM A105 / A105M - Specification for Carbon Steel Forgings for Piping Applications

• ASTM A234 / A234M - Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service

• ASTM A403 / A403M - Specification for Wrought Austenitic Stainless Steel Piping Fittings

• ASTM A420 / A420M - Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service

AWWA
American Water Works Association

AWWA About - Established in 1881, the American Water Works Association is the largest nonprofit, scientific and educational association dedicated to managing and treating water, the world’s most important resource.

• AWWA C110 - Ductile-Iron and Gray-Iron Fittings, 3 Inch Through 48 Inch (75 mm Through 1200 mm), for Water and Other Liquids

• AWWA C208 - Dimensions for Fabricated Steel Water Pipe Fittings

ANSI: 
The American National Standards Institute

The American National Standards Institute
ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns "schedule numbers". These numbers classify wall thicknesses for different pressure uses.

MSS STANDARDS 
Manufacturers Standardization Society

The Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry is a non-profit technical association organized for development and improvement of industry, national and international codes and standards for: Valves, Valve Actuators, Valve Modification, Pipe Fittings, Pipe Hangers, Pipe Supports, Flanges and Associated Seals

• MSS SP-43 - Wrought Stainless Steel Butt-Welding Fittings Including Reference to Other Corrosion Resistant Materials

• MSS SP-75 - Specifications for High Test Wrought Buttwelding Fittings

• MSS SP-73 - Brazing Joints for Copper and Copper Alloy Pressure Fittings

• MSS SP-83 - Class 3000 Steel Pipe Unions, Socket-Welding and Threaded

• MSS SP-97 - Integrally Reinforced Forged Branch Outlet Fittings — Socket Welding, Threaded, and Buttwelding Ends

• MSS SP-106 - Cast Copper Alloy Flanges and Flanged Fittings Class 125,150, and 300

• MSS SP-119 - Factory-Made Wrought Belled End Socket Welding Fittings

Difference between “Standard” and “Codes”:

Piping codes imply the requirements of design, fabrication, use of materials, tests and inspection of various pipe and piping system. It has a limited jurisdiction defined by the code. On the other hand, piping standards imply application design and construction rules and requirements for pipe fittings like adapters, flanges, sleeves, elbows, union, tees, valves etc. Like a code, it also has a limited scope defined by the standard.

Factors affecting standards:

“Standards” on pipe fittings are based on certain factors like as follows:

• Pressure-temperature ratings

• Size

• Design

• Coatings

• Materials

• Marking

• End connections

• Dimensions and tolerances

• Threading

• Pattern taper etc.

BSP: 
British Standard Pipe

BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring.

JIS: 
Japanese Industrial Standards

This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations.

NPT:
National Pipe Thread

National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting.

BOLTS & NUTS

• A193 = This specification covers alloy and stainless steel bolting material for pressure vessels, Valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications.

• A320 = Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for Low-Temperature Service.

• A194 = Standard specification for nuts in many different material types.

AN:
Here, "A" stands for Army and "N" stands for Navy

The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments. For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16" or ¼". It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread.

Dash (-) size

Dash size is the standard used to refer to the inside diameter of a hose. This indicates the size by a two digit number which represents the relative ID in sixteenths of an inch. This is also used interchangeably with AN fittings. For example, a Dash "8" fitting means an AN 8 fitting.

ISO: 
International Organization for Standardization

ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows: