"Calulating a Corrosion Allowance for ASME B31.3 Piping"

Question:

"Per Code, I have calculated a minimum pressure design thickness of some 6" Sch. 80, ASTM A-335, P-11 Piping. How do you arrive at a figure to allow for corrosion allowance. A corrosion allowance of 0.063" (1/16") is typical, but is there a formula or table to provide this number? Does a mandatory corrosion allowance have to be figured in to satisfy the Code?"

Answer:

As far as I am aware, B31.3 does not stipulate a corrosion allowance (CA). Corrosion allowances are normally established by the end user and are somewhat based on personal preferences and industry tradition. 0.062" for piping is a common CA; however, you are free to set whatever corrosion allowances you wish, unless a state or local agency has adopted and superceded B31.3. To specify the pipe, add the CA to the minimum design thickness and select a pipe schedule that is equal to or greater than the Min. + CA.

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