Process Piping Materials – Module 2 – M06-036

CHAPTER - 2

MATERIALS – METALLIC PIPING

2. METALLIC PIPES

Metals are favored as process piping material because they offer a combination of mechanical properties that are unique and not found among non-metals.

Metals are generally strong and many can be loaded or stressed to very high levels before breaking.

2.1.Piping Material Specifications – ASME/ASTM

The most widely used standard specification for steel products in the United States is by the American Society for Testing and Materials (ASTM). It defines the specific manufacturing process of the material and defines the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc.

Other standard specifications are as prescribed by the American Petroleum Institute (API). The API operates similarly to the ASTM except that producers, consumers, and associations with primary interests in oil or gas are involved.

2.2.ASTM Material Designation

ASTM’s designation system for metals consists of a collection of documents called material specifications for standardizing materials of large use in the industry.

•Specifications starting with “A” are for steel.

•Specifications starting with “B” are for non-ferrous alloys (bronze, brass, copper nickel alloys, aluminum alloys and so on).

•Specifications starting with “D” are for plastic material, as PVC.

Example

ASTM A105/A105M-02, Standard Specification for Carbon Steel Forgings for Piping Applications, breaks down as follows:

•‘A’ describes a ferrous metal. Prefix B is for nonferrous materials.

•105 is a sequential number without any relationship to the metal’s properties.

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Process Piping Materials – Module 2 – M06-036

•M indicates that the standard A105M is written in rationalized SI units (the M comes from the word Metric), hence together 105/A105M includes both inchpound and SI units.

•02 = 2002, the year of the latest version.

•Official title = Standard Specification for Carbon Steel Forgings for Piping Applications.

Many of the ASTM specifications have been adopted by the American Society of Mechanical Engineers (ASME) with little or no modification. The ASME designation follows a similar scheme but uses the prefix S, for example, ASME-SA213 and ASTM A213 are identical.

2.3.Pipe Grades

Grade refers to divisions of steel (A, B, C….) within different types of pipes. It defines the mechanical properties such as the maximum tensile strengths and the yield strengths.

•Grade A, B and C

−Grade A, being a softer steel, which is easier to bend.

−Grade B has higher tensile and yield strength than Grade A. It has higher stress values and is better suited for machining operations.

−Grade C has higher tensile and yield strength than Grades A and B.

The complete range of ASTM prefixes are A, B, C, D, E, F, G, PS, WK; however, the piping requirements referenced in ASME B31.3 call for only A, B, C, D, and E. Higher alphabet indicates higher tensile or yield strength steels, and if it is not alloyed, it has an increase in carbon content.

Example

•ASTM A 106 Grade A, Grade B, Grade C - Seamless Carbon Steel Pipe. In this case:

−Grade A:0.25%C (max), 0.1% Si, 48 ksi tensile strength (min);

−Grade B: 0.30%C (max), 0.1% Si, 60 ksi tensile strength (min);

−Grade C 0.35%C (max), 0.1% Si, 70 ksi tensile strength (min).

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