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How to Calculate Corrosion Allowance For ASME B31.3 Refinery Piping
2

How to Calculate Corrosion Allowance For ASME B31.3 Refinery Piping

How to Calculate Corrosion Allowance For ASME B31.3 Refinery Piping

(OP)
Using the formula and tables in ASME B31.3, I have calulated a minimum pressure design thickness for some ASTM A-335, P-11, 6" Sch 80 Seamless Piping.  (I have calculated a value of 0.376" at 750 p.s.i. at 1000ºF.)  How do you determine a corrosion allowance value to add to this number to get a true minimum thickness that will satisfy the Code?

RE: How to Calculate Corrosion Allowance For ASME B31.3 Refinery Piping

2
GD,
Firstly you should determine if the piping is in a corrosive environment and establish or predict a corrosion rate.

An acceptable industry standard for corrosion rates is in the order of 10 mpy (mils per year). Base your corrosion allowance on design life 10 yrs, 20 yrs, etc.

As you have calculated a minimum thickness of .376", as a minimum specify Sch 80 (.432"). In a non corrosive environment this would allow a corrosion allowance of .056". At 10 mpy, life would be about 5 yrs.

If the corrosivity is unknown or a longer life is desired, use a higher pipe schedule and calculate the CA.
Hope this helps...

RE: How to Calculate Corrosion Allowance For ASME B31.3 Refinery Piping

I have a similar question.  I am designing a distribution piping system for aviation hydraulic fluid MIL-H-83282 between hydraulic power supplies and the test stands they power.  Does using this fluid, fire resistant hydraulic fluid with corrosion inhibitors, require adding the corrosion allowance, c value, to the formulas of ASME B31.3?  Does Stainless Steel pipe require using a c value?  I am considering all welded construction.

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