02:31 Dec-09-2008 Roger D NDT Inspector, API-510, 570, 653 MISTRAS, USA, Joined Jan 2009 148
Re: Hydrotest of Sphere ----------- Start Original Message ----------- : Dear : We just need to know how much time duration required for doing hydotest of Sphere : Dia - 15.4meters : Regards : Ashish ------------ End Original Message ------------ The standard [& traditional] ASME vessel test time is 10 minutes at overload [the full test pressure with any temperature/mat'l stress corrections figured in]. This is just a 'usual & customary' time. If it's going to fail, it'll happen IMMEDIATLY.
Do not allow the pressure gauge(s) to be unattended for even a minute at overload. Spheres vent well, and sunshine on a well vented vessel can cause MAJOR increases in test pressure, just due to the expansion of the water.
Some company spec's call for a 1-hour hold at test pressure, but this is just added danger. Overload it, hold it at overload for a very few minutes, drop the pressure down to Design [or a little above Design] & imspect for leaks and other problems. If you're feeling suicidial, do the visual inspection at full Overload. There's a reason that ASME Sect. VIII now recommends waiting until the pressure has been decreased to do the close-up inspection.