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

[gd]

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?

 

[rustbuster]

GD,<br>Firstly you should determine if the piping is in a corrosive environment and establish or predict a corrosion rate.<br><br>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.<br><br>As you have calculated a minimum thickness of .376&quot;, as a minimum specify Sch 80 (.432&quot. In a non corrosive environment this would allow a corrosion allowance of .056&quot;. At 10 mpy, life would be about 5 yrs.<br><br>If the corrosivity is unknown or a longer life is desired, use a higher pipe schedule and calculate the CA.<br>Hope this helps...

 

[rmwilson]

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.