Proper Interpretation of Shell Design 1

[Andrewdroth]

I have a question regarding the wording of 5.6.1.1 in API 650.

"The required shell thickness shall be greater of the design shell thickness, including any corrosion allowance, or the hydrostatic test shell thickness, but the shell thickness shall not be less than the following:"

Does this mean the indicated minimum thicknesses are prior to adding a corrosion allowance? Or do you add the corrosion allowance to the design thickness, and if the thickness is still less than the indicated minimum, bump it up?

I did a quick search and It doesn't look this has come up before on the forum.

I'm relatively new to the code and any guidance would be greatly appreciated.

 

[xema77]

Corrosion allownace need not be applied to the minimum thicknesses indicated in the table of 5.6.1.1. I believe that the minimum thicknesses provided are for fabrication reasons.
Ensure you still consider all external loads such as wind, seismic and nozzle loads when considering plate thickness.

 

[IFRs]

Calculate the design, add corrosion allowance.
Calculate the hydrotest, no corrosion allowance needed.
Read the minimum.
Take the greater of the three.

 

[Andrewdroth]

Thanks Guys.