American standards for pipe elbows

American pipe elbow standard:

Elbows are pipe fittings that change the direction of pipes in pipes. They are mainly used for pipe connections or to allow pipes to turn within a certain range. There are many kinds of materials for elbows, including cast iron, stainless steel, carbon steel, and alloy steel, and there are also different production standards. Common production standards are American standards and Chinese standards. Elbows of different standards have different design dimensions and quality requirements.

1. ANSI / ASME Standards

Elbows are a common pipe fitting used to change the flow direction of pipes and connect two pipes at different angles. In the United States, ANSI / ASME B16.9 is one of the main standards for elbows. This standard specifies the design, materials, dimensions, manufacturing, inspection and other requirements of elbows. Among them, elbows are divided into different angles such as 45-degree elbows, 90-degree elbows, and 180-degree elbows. They can be made of carbon steel, stainless steel, alloy steel and other materials, and are suitable for pipeline systems under different pressure levels and temperature conditions.

2. ASTM Standards

ASTM (American Society for Testing and Materials) is an international standards organization whose standards mainly cover materials, products, test methods and other fields. In terms of elbows, ASTM A234 is a commonly used standard that specifies the manufacturing requirements for carbon steel and alloy steel sleeve pipes, elbows, tees and other pipe fittings, but does not give specific size and angle requirements. Therefore, when selecting, it is necessary to combine the specific usage and the standard requirements of the region.

Main differences and application scope:

There are some differences between the ANSI / ASME standard and the ASTM standard in the size requirements and application scope of elbows. Generally speaking, the ANSI / ASME standard is applicable to general industrial piping systems, while the ASTM standard is applicable to special industry fields such as refining, chemical industry, pharmaceutical industry, etc. In addition, the elbows of the ANSI / ASME standard are relatively more standardized and suitable for piping systems under most pressure levels and temperature conditions, while the elbows of the ASTM standard are more flexible and can be manufactured according to specific requirements.

Common American standards for pipe elbows are as follows:

ASME/ANSI B16.9
Applies to factory-made forged steel butt-weld pipe fittings, covering elbows, tees, reducers, etc., and specifies dimensions, tolerances and material requirements.

ASME/ANSI B16.11
Applies to forged steel pipe fittings for socket welding and threaded connections, including elbows, tees, etc., and specifies pressure grades and sizes.

ASME/ANSI B16.28
Applies to forged steel butt-weld short radius elbows and return elbows, and specifies dimensions, tolerances and material requirements.

ASTM A234/A234M
Applies to forged carbon steel and alloy steel butt-weld pipe fittings for medium and high temperatures, including elbows, and specifies chemical composition, mechanical properties, etc.

ASTM A403/A403M
Applies to forged austenitic stainless steel butt-weld pipe fittings, including elbows, and specifies chemical composition, mechanical properties, etc.

MSS SP-43
Applies to forged stainless steel butt-weld pipe fittings, including elbows, suitable for low pressure and corrosive environments.

MSS SP-75
Applies to high-strength butt-weld pipe fittings, including elbows, suitable for high pressure and high temperature environments.

MSS SP-79
Applicable to socket welding reducing inserts, including elbows, for small diameter piping systems.

MSS SP-83
Applicable to 3000 lb. class socket welding and threaded pipe fittings, including elbows, for high pressure systems.

MSS SP-95
Applicable to reducers and round ends, including elbows, for low pressure systems.

Difference between the American standard elbow and the Chinese standard elbow:

1. Size standard
The size standards of the American standard and the Chinese standard elbow are different. The size of the American standard elbow is in inches, and the diameter range is 1/2 inch-72 inches. The size standard of the Chinese national standard elbow is the nominal diameter, and the diameter range is DN15-DN2000. Therefore, when selecting and purchasing elbows, you need to choose the corresponding American standard or Chinese standard according to the actual diameter of the pipe.

2. Material
The material standards of the elbows in the American standard and the Chinese standard are different. The elbow materials in the American standard include carbon steel, stainless steel, alloy steel, cast steel, etc., among which carbon steel is the most commonly used material. The elbow materials in the Chinese standard include Q235A, 20#, 16Mn and 10#, among which Q235A is the most commonly used material. Therefore, when selecting, you need to choose the appropriate material according to the chemical properties and pressure level of the pipeline liquid.

3. Manufacturing standard

The manufacturing standard of the elbow is also an important difference between the American standard and the Chinese standard. The manufacture and installation of American standard elbows must comply with relevant standards, such as ANSI B16.9, MSS SP-43, etc., while the national standard elbow manufacturing standard is GB, and manufacturers need to manufacture in accordance with national standards. Therefore, when choosing an elbow, you need to check the standard and choose a suitable manufacturer.

Size and wall thickness: 

In terms of size, ANSI elbows may have some specific requirements, such as the outer diameter of the pipe and the deviation range of the wall thickness. In terms of the expression of wall thickness, ANSI often uses "SCH" (Schedule) followed by numbers, such as SCH 5, SCH 10, SCH 40, SCH 80 pipe elbows, etc. These numbers represent different wall thickness grades.

Common errors:
In the process of producing or using American standard elbows, common errors include bending radius error and angle error. Bending radius error is usually caused by poor workmanship or material quality problems, which will result in the failure to achieve the ideal effect when connecting pipes. Angle error refers to the difference between the bending angle of the elbow and the required angle, which should usually be controlled within the standard range.

Precautions for the use of pipe elbows:

1. The wall thickness of the elbow should comply with the standard to ensure the safe use of pressure.
2. Sealing gaskets need to be used at the elbow joints during installation to prevent leakage.
3. During transportation, the elbows need to avoid impact and be handled with care to avoid deformation that affects the use effect.
4. The use environment of the elbows needs to be regularly inspected, maintained and maintained to ensure their service life and safety.

In general, the choice of standard elbows needs to be flexibly selected according to the specific situation and application requirements, and at the same time, it needs to ensure compliance with relevant national and regional standards and regulations.

Read more: Types, advantages and disadvantages of elbow fittings