Alloy A335 P5 corrosion / erosion allowance

[749KDV]

Hello corossion engineers,

This is a three part question.

1) What is a reasonable corrosion/erosion allowance for A335 GR P5 (5CR-1/2MO) alloy pipe for use in determining minimum wall pressure/temperature ratings per ASME B31.1 (Power Piping)?

I was told that for an erosive service an allowance of 0.10" is what should be used. To me it seems high.

2) If 0.10" is what is recomended, why wouldn't I specify P22 rather than P5? Isn't it true that P22 needs little if no corossion/erosion allowance?

3) Do you know of a EPRI document (or another) that specifies an adequate corossion / erosion allowance for these alloy materials?

I appreciate any help you can give.
Thanks,
Joe

 

[PAN]

I think that you can not get conclusion here. I used to see many project specifications with variaty of minimum corrosion allowance.

In my plant, A335-P22 has higher corrosion allowance (compare to A335-P5).