Pressure Vessel Corrosion Allowance

[Jharper361]

My employer has thrown me into the world of QA/QC inspection after years of never inspecting their fleet. I am questioning our U1a's. They state a Minimum thickness of .680 on 96'' heads but allowable CA of .0625. Do I subtract .0625 from the minimum thickness or is the minimum thickness when we call it a dead vessel or downgrade MAWP?

 

[LittleInch]

Any other thicknesses it quotes?

Min should be minimum. then you add CA to get to your required as built or more thickness, but depends how they've calculated minimum.

 

[Christine74]

Refer to nonmandatory Appendix W in ASME Section VIII Div. 1 for guidance on the U-1A. Specifically see item (28) in Table W-3.

The thicknesses shown on the U-1 Data Reports have always referred to the Uncorroded condition.


-Christine

 

[Louisiana Inspector]

The minimum thickness of .680 on the U1 is the minimum thickness after forming, not the minimum thickness based on design.

.680-.010-.0625 = Alarm Thickness / tmin

PD/2SE-0.2P = Pressure Design Thickness

ASME Sec. VII Div. 1 UG-32