ASME VIII-1: Hydrostatic Test UG-99 (c) and definition of "basis for calculated test pressure&q

[FPPE]

Hi,
I would like to clarify what is written in the title by linking to the following thread:

thread292-370284: MAP and UG-99(c)

From ASME VIII-1, UG-99 (c):

"A hydrostatic test based on a calculated pressure may be used by agreement between the user and the Manufacturer. The hydrostatic test pressure at the top of the vessel shall be the minimum of the test pressures calculated by multiplying the basis for calculated test pressure as defined in 3-2 for each pressure element by 1.3 and reducing this value by the hydrostatic head on that element. When this pressure is used, the Inspector shall reserve the right to require the Manufacturer or the designer to furnish the calculations used for determining the hydrostatic test pressure for any part of the vessel."

From ASME VIII-1, Mandatory Appendix 3, Par. 3-2 Definition of terms:

"calculated test pressure: the requirements for determining the test pressure based on calculations are outlined in UG-99(c) for the hydrostatic test and in UG-100(b) for the pneumatic test. The basis for calculated test pressure in either of these paragraphs is the highest permissible internal pressure as determined by the design equations, for each element of the vessel using nominal thicknesses with corrosion allowances included and using the allowable stress values given in Section II, Part D, Subpart 1 for the temperature of the test."

So, I understand that UG-99 (c) says:

Hydrostatic Test Pressure = 1.3 * "basis for calculated test pressure (with nominal thicknesses minus corrosion allowance)" - hydrostatic head on that element

So, taking advantage of what the software calls "MAP", but not in "cold & uncorroded" conditions, as I have read in many threads, but in "cold & CORRODED" conditions, to allow the hydraulic test to be performed in field with the corroded vessel.

Also, by not subtracting the hydrostatic head you are not following UG-99 (c), but you would need to make arrangements with the customer, because you would get a higher pressure.
Obviously, in contrast to UG-99 (b), UG-99 (c) involves calculating the test pressure for each element, and then only the least is considered. UG-99 (b) on the other hand calculates the stress ratio for each element and then only considers the LSR, but the pressure is unique.

This is what I understand, can anyone confirm or correct?
Thank you very much

 

[david339933]

So, I understand that UG-99 (c) says:

Hydrostatic Test Pressure = 1.3 * "basis for calculated test pressure (with nominal thicknesses minus corrosion allowance)" - hydrostatic head on that element

UG-99(c) includes CA...not "minus CA".

If the vessel is corroded, you should refer to NBIC which may have slight tweaks to the hydrotest procedure/pressure.

 

[FPPE]

Thanks David, I had interpreted "included" as "including corrosion in the calculation" then subtracting it from the nominal thickness. I think it was enough to include a formula to make it clearer.

My doubt arose from the fact that several software programs use the term "MAP", which in ASME VIII-1, note 8 of Figure UCS-66.2 is defined as:

“The MAP is defined as the highest permissible pressure as determined by the design equations for a component using the nominal thickness less corrosion allowance”

What do you mean by NBIC?

Thank you

 

[david339933]

Yes that is a little issue using the term MAP as indicated in the thread you posted, but the code doesn't list it as MAP, only calculated test pressure.
NBIC - National Board Inspection Code.

 

[FPPE]

Thank you David, I'll check it.