Does anyone know if there is a minimum time duration for a hydrostatic test? It seems that 30 minutes is an acceptable time but is the test time actually stated anywhere within ASME?

There is no specific requirement in Section VIII-1 for the duration of hydrostest.

There is no time indicated in ASME Code . Normally 30 minutes is considered acceptable .

National Board specifies 15 minutes time for Hydrotest .

B31.1 says to hold the test pressure equal to 1.5*MAWP for a minimum 10 min for NBEP and after 10 min, it may be reduced to MAWP for a sufficient time necessary to determine if there is any leakage.

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Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

There is none, but let me give my coin of withsdom: If there are reinforcing plates and you did not witness air test on them, let the hydrostatic pressure for one hour. This will let the water pass through any porosity, fill the gap between shell and RP then come out from the bleed hole. It happened to me once in my life and it was an important 5%Ni column for ethylene plant, built by a big manufacturer. It was 40 years ago, but I can't forget and it may happen again.
Mauro