Minimum test pressure

[PVdesigner]

Hi All
For a clad vessel with low liquid head, MAP & MAWP difference is very small. This vessel is to be hydro tested per UG-99C (horizontal position) and shall meet future hydro test requirement (in vertical position) per UG-99b. Calculated shop test pressure per UG-99C came out to be less than field hydro test pressure. How do we ensure that hydro test to meets the minimum requirement of UG-99(b) when the test pressure basis was set to UG-99 C? Thanks

 

[vesselfab]

your horiztal hydro at map (ug-99c) is the max you can hydro at. future vertical should be 1.3(mawp) with deduction for the additional liquid head.

I am not sure how the field vertical at mawp could be higher than shop horizontal at map could be higher

 

[PVdesigner]

Since the vessel is clad, corrosion allowance has been set to zero & operating liquid head @ bottom shell is 1.19 psi. MAWP (545.26 psi) & MAP (546.45 psi) is limited by bottom shell. So, the field hydrotest (UG-99b) will be 1.3 x MAWP = 708.84 psi whereas shop hydrotest(UG-99c) will be 1.3 X MAP- Test Liquid Static Head = 1.3 X 546.45 -2.403 = 707.98 psi. Am I missing something in my calc. ? This error is flagged my new build (6261) of Compress.

 

[vesselfab]

in your design, do you have the liquid level set for hydro in vertical

Compress does not like a second hydro condition so you have to copy the file and run it with full liquid which should lower mawp signifigantly