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Technical Discussions
Dent McIntyre
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
00:47 Mar-29-1999
Penetrant Test of vessel under pressure

A vessel is under Helium pressure at 100 PSI for the purpose of performing a Helium Leak test.
A tiny Inconel weld on the vessel needs to be PT inspected but was not done prior to pressurizing.
What effect will this have on the penetrant test?


 
 Reply 
 
S.V.Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
09:45 Aug-16-2002
Re: Penetrant Test of vessel under pressure
Pressurisation of the vessel will have a tendency to slightly expand the vessel, thus there will be a tensile stress on the outer surface. This will slightly magnify the size of any discontinuity that may be present. So, the best course is to 'retest' the same weld after the pressure test is completed and the internal pressure removed, before attempting to 'size' the discontinuity and apply the specification for acceptance and or repair.

: : A vessel is under Helium pressure at 100 PSI for the purpose of performing a Helium Leak test.
: : A tiny Inconel weld on the vessel needs to be PT inspected but was not done prior to pressurizing.
: : What effect will this have on the penetrant test?
: ..
.



 
 Reply 
 
rodney fordham
rodney fordham
03:55 Aug-16-2002
Re: Penetrant Test of vessel under pressure
:A partial thickness crack on the outside of a pressure vessel wall opens slightly when the internal pressure is applied. The more sensitive interferometric techniques reveal that the vessel bulges a little in the vicinity of the crack. Does anyone know what the relative importance of internal and external partial thickness cracks is? Clearly the external cracks are more weakening than internal?
====================
: Pressurisation of the vessel will have a tendency to slightly expand the vessel, thus there will be a tensile stress on the outer surface. This will slightly magnify the size of any discontinuity that may be present. So, the best course is to 'retest' the same weld after the pressure test is completed and the internal pressure removed, before attempting to 'size' the discontinuity and apply the specification for acceptance and or repair.
.
: : : A vessel is under Helium pressure at 100 PSI for the purpose of performing a Helium Leak test.
: : : A tiny Inconel weld on the vesselneeds to be PT inspected but was not done prior to pressurizing.
: : : What effect will this have on the penetrant test?
: : ..
: .
.



 
 Reply 
 
Dent McIntyre
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
05:36 Aug-19-2002
Re: Penetrant Test of vessel under pressure
Pressure inside a vessel especially (helium)will inhibit the capillary action of the penetrant in entering leaks. The thru wall leak may not be detected with the penetrant test.
Furthermore, penetrant could also plug a tiny leak and make it undetectable with the helium test.

This information comes from a recent experience of a vessel similar to the one described.
For more information e mail me directly.


: :A partial thickness crack on the outside of a pressure vessel wall opens slightly when the internal pressure is applied. The more sensitive interferometric techniques reveal that the vessel bulges a little in the vicinity of the crack. Does anyone know what the relative importance of internal and external partial thickness cracks is? Clearly the external cracks are more weakening than internal?
: ====================
: : Pressurisation of the vessel will have a tendency to slightly expand the vessel, thus there will be a tensile stress on the outer surface. This will slightly magnify the size of any discontinuity that may be present. So, the best course is to 'retest' the same weld after the pressure test is completed and the internal pressure removed, before attempting to 'size' the discontinuity and apply the specification for acceptance and or repair.
: .
: : : : A vessel is under Helium pressure at 100 PSI for the purpose of performing a Helium Leak test.
: : : : A tiny Inconel weld on the vessel needs to be PT inspected but was not done prior to pressurizing.
: : : : What effect will this have on the penetrant test?
: : : ..
: : .
: .
.



 
 Reply 
 

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