Pipe material selection: What are basis for the pipe material selection?

Pipe material selection

1. Basis for the  pipe material selection is the conditions under which the materials shall operate. The following information is normally required to select the correct material:

• Fluid properties
• Operating temperature and pressure
• Design temperature and pressure
• Upset conditions
• Material properties (corrosion resistance and mechanical properties)
• Material limitations

2. The basis for the material selection shall be developed in close cooperation with process, mechanical, and piping engineering to enable the best possible total design.

3. Materials shall normally be selected to last for the lifetime of the installation.

4. The total cost of the completely installed system shall be used in any cost comparisons, bearing in mind that the cost of the material is only a minor part of the total cost of a system. As a minimum, the following considerations shall be included:

• Maintenance costs may be reduced or eliminated by using corrosion resistant materials.

• Weight savings can be achieved if corrosion resistant materials without corrosion allowance are used.

• Weight savings for high-pressure systems may be possible where higher strength materials are used.

• Materials allowing increased flow velocity may allow for reduced pipe size.

• Use of cost effective fabrication methods may give total cost reduction cold and induction bending or omission of post weld heat treatment.

• More expensive materials may be easier to work with and thereby reduce component fabrication costs that more than offset the increase in unit material cost.

·         Design Life

Design Life (DL)        = 20 years for Equipment
= 10 years for piping, or
= Per Client’s requirements
·         Corrosion Rate (CR) Estimation
CR = mils per year (mpy) or millimeters per year (mm/yr)
·         Corrosion Allowance (CA)
CA = 1/16”, 1/8”, 3/16” or 1/4”
                                = 1.6 mm, 3.2 mm, 4.8 mm or 6.4 mm
Maximum CA = 1/4” or 6.4 mm
(Upgrade material if required CA is > ¼” or 6.4 mm)
CA = CR x DL

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