Tuesday, May 8, 2012

Re: [MW:14215] API 650 - Vacuum box test Vs PT/MT(Penetrant Test/MPI)

Vacuum box test is mean to find the air leak where PT/MT mean to find the defects...
Assume minute  a pin hole on the weld thorough the weld thickness,where in vacuum box test it can be traced easily and where PT/MPT,sometimes it may not be able to trace the minute defects.
And in MPT/PT,pin holes, porosity are acceptable up to certain size so when the pin hole is throught the plate thickness,it may cause leak..
As we know the tanks are for storage purpose,even a minute leak causes big problems..
Tats why Vacuum box test is preferred.

On Mon, May 7, 2012 at 4:21 PM, M S <striarc@gmail.com> wrote:

Please provide technical support:-

What is the difference between Vacuum box test(for leak detection) and PT(for surface discontinuity detection)?

PT can detect all the surface discontinuity as well and MT can detect surface and slightly subsurface discontinuity also, but why API 650 prefers Vacuum box test instead of PT for Carbon steel-tank bottom plate welding?

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