Question about UG-99 (b) (c) and (g) Hydrotest 2

[billbusy]

1. UG-99 (b) vs UG-99 (c)

I think in both cases we measure hydrotest pressure on top of equipment.In both of case liquid is full.
In case of UG-99 (b) Hydrotest pressure = 1.3 * MAWP * Stress ratio
Does UG-99 (C) Hydortest pressure = 1.3 * MAWP - Hydro static Head?

How should the hydro static head be calculated? As it is supposed to be 0 at the top of the equipment.

2. UG-99 (g)

This tells us the acceptable critia, but there is a sentence like "This inspection shall be made at a pressure not less than the test pressure divde by 1.3"

I am confused if the inspection is made when the test pressure on the vessel or after the test pressure is been released?


Thanks!



3 years industry experience;
Oil & Gas industry in Canada.

 

[Tony1t]

Hi Billbusy,

UG-99(b) says that Hydrotest pressure = 1.3 * MAWP * Stress ratio, MAWP may be assumed to be same as design pressure, likewise which stamp on nameplate.
UG-99(c) says that Hydortest pressure = 1.3 * MAWP - Hydro static Head, MAWP is determined by calculated, general the MAWP > design pressure.

You may be select (b) or (c) to determine test pressure. but general condition, (b) is usual.

UG-99(g), when inspector does inspection,the pressure shall be down to a value which test preesure divid by 1.3.such as test pressure is 1.3Mpa, inspection pressure shall be 1.3/1.3=1Mpa after enough holding time.

 

[LittleEd]

Typically, the vessel is taken to 1.3 x MAWP x Stress Ratio and held for a period (as required per test procedure or the A.I.), after this period, the vessel may be lowered back to the MAWP for the actual close visual inspection by QC and the A.I. This is for the safety of those performing the inspection. Code requires the vessel to be taken to the higher test pressure and held (no specific time required) but then pressure is lowered to perform the actual inspection. Many, many shops and Inspectors still often perform the actual inspection with the full hydro test pressure on the vessel, but this is not required, the pressure can be lowered for safety purposes.