Re: [MW:14294] API 650 - Vacuum box test Vs PT/MT(Penetrant Test/MPI)

Dear Sir,
you can find surface discontinuities and Imperfections by PT and you
can find Subsurface imperfections/Discontinuities by MT also. But Code
given some tolerance for the acceptance criteria in these method.
While you do with Vacuum box test you can find Pinholes and small
cracks and code doesn't allow any small defect for bottom plate lap
welding and access to the all corner of the vessel or tank.

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George Xue (Xue Guoliang)
Suzhou CXGL Mechanical Engineering Co., Ltd.
China
Tel: +86-512-68639769 Fax: +86-512-68639492
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2012/5/8 deva m <devmunch@gmail.com>:
> 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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>
>
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.