Recommended Practices for selection of Pipes

The selection of piping systems is an essential aspect of plant facility layout and design. Generally, the selection of pipe begins when the designer determines the location of the new pipe. It is a challenging task for process engineers as they have to choose the right pipe by considering many factors such as size, class, pipe materials, pressure, temperature, and more. 

Let’s take a look at the approaches to be followed on the selection of pipes.

The material used in pipes is defined by the type of joint, wall thickness, weight, length, and more. The majority of pipes are made up of carbon steel, stainless steel, and chrome-moly pipe. When a designer selects the type of pipe for a particular application and location, it is recommended to determine the pipe service life. Materials such as pipe composition, thickness, and coating of pipes define pipe service life. The soil elements, including soil resistivity, pH, sulfate levels, and more, can adversely affect the pipe service life. 

Below are some typical manufacturing standards and grades for different types of pipes:

1. Carbon Steel: ASTM A105, ASTM A106, ASTM A333, API5L, ASTM A691

2. Stainless Steel: ASTM A312, ASTM A358 

3. Grades: Grade B, X60, TP304, and Gr 11/4 C

The outside diameter of the piping system shall be within tolerances as specified in 

API 5L Specifications.

NPS and DN define the internal diameter of the pipe.

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes, which is used for high or low pressures and temperatures.

Diameter Nominal (DN) indicates standard pipe size when followed by the specific size designation number without a millimeter symbol. The European international designation equivalent to NPS is DN, in which dimensions are measured in millimeters. It is used in the metric unit system.

The standard for wall thickness is expressed as wt, std, xs, and xxs. Weight classes and schedules should be followed as per the American Society for Testing and Materials in ASTM A53. The pipe wall thickness is calculated based on various factors such as maximum and working temperatures, chemical properties of the fluid, fluid velocity, pipe material, and more. 

    1. Seamless Pipes:

Seamless pipes are made from solid round billets, and it doesn’t contain any welding and joints. It can withstand higher operating pressures and temperatures compared to welded pipes. So, it is widely used in high-pressure systems.

    2. Electric Resistance Welded (ERW):

ERW pipes are formed by rolling metal and then welding it longitudinally across its length. It has reduced allowable compared to seamless pipes.

    3. Electric Fusion Welded Pipe (EFW):

EFW pipes contain electron beam welding, which is formed by rolling plate and welding the seam. ASTM A672 is the standard code for EFW pipes. 

    4. Galvanized Pipes: 

Galvanized Pipes are carbon steel pipes coated with a protective layer of zinc to prevent rust and corrosion. The specification of pipes must be as per the ASTM A53 pipe standard.

We hope that this article provided you with adequate information for the selection of pipes. If you’re seeking piping engineering services, consider hiring a company that adheres to international codes and standards.

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