Pipe Specifications, Standards and Grades

Pipe Specifications & Standards

The American Society for Testing and Measurements (ASTM)
Steel pipes are manufactured and tested based on specifications agreed upon by the committees of the ASTM (The American Society for Testing and Measurements). These committees are designed to fairly represent the interests of steel pipe users, steel pipe producers, and relevant interest groups.

Steel pipe specifications are published to ensure all pipe manufacturers follow a balanced level of standards and deliver quality products. They also help pipe buyers develop a better understanding of product requirements. Steel pipe specifications, in addition to regulating manufacturing and testing, dictate the methods used for measuring a pipe’s mechanical and physical properties. Physical properties include the pipe’s outer diameter, weight, and wall thickness. If these properties do not meet the require parameters, they are discarded.

American Petroleum Institute (API)
Line and oil pipe products also follow specified standards; however, their specifications are developed by the committees of the American Petroleum Institute (API). The API issues a license to a pipe manufacturing plant only after it has thoroughly inspected the plant and reviewed the plant’s manufacturing processes and testing procedures. Approved plants are given the right to mark their pipe products with the API monogram.

Five Categories of Pipe

Pipe standards and specifications are typically grouped into five pipe categories. These categories include:

1) Standard Pipe
Standard pipe have general applications. They are used for pipeline transmission systems that convey steam, water, air, and gas. They are also used for structural purposes, as well as plumbing and heating. Standard pipe specifications are published by the ASTM.

2) Line Pipe
Line pipe is used in pipeline transportation systems for the petroleum and natural gas industries. Line pipe specifications are published by the American Petroleum Institute (API)

3) Oil Country Tubular Goods (OCTG)
Oil Country Tubular Goods are pipes and tubing products, which are used for the operation and drilling of gas and oil wells. OCTG pipes and tubing products are manufactured and tested based on the guidelines of the American Petroleum Institute (API).

4) Pressure Tubing
Pressure tubing is a seamless pipe, used for pressure applications such as in boilers and condensers.

5) Mechanical Tubing
Mechanical tubing includes a variety of products used for mechanical and structural purposes, as well as for machining operations.

Pipe Grades A/B/C

Different types of seamless pipes and welded pipes are divided into subsets called grades. Pipe grades A/B/C define the pipe’s mechanical properties, which include its minimum yield strength and tensile strength, or its resistance to deformation and breakage under tension.

Grade A
Grade A steel refers to soft, bendable steel used for such formation operations as coiling and cold bending.

Grade B
Grade B steel is manufactured from higher carbon steel and has a higher tensile strength and yield strength than Grade A steel.

Grade C
The tensile strength and yield strength of Grade C steel is superior to those of Grade A and Grade B steel.

The API designates X-grades to indicate the lowest acceptable yield strengths. Examples of these grades include X-42, X-46, X-52, and X-65.

Pipe specifications are revised often, so it is vital to reference only the most up-to-date specifications. Pipe specifications typically pertain to black steel pipe*, galvanized welded piping, and seamless pipes.

*Black steel pipe got its name from the appearance of its outer surface, which is coated with dark, iron oxide. It is a type of steel pipe that has not been galvanized and is used in applications where galvanizing is unnecessary.

Black steel pipe has very little maintenance and a high level of strength, making it ideal for transporting water and gas in rural and urban areas. Black steel pipe is also suitable for conduits protecting electrical wiring and delivering high-pressure steam and air. Other black steel pipe applications include water wells, gas distribution – inside and outside homes – and sewage systems. Black steel pipes shall never be used for conveying potable water.