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- since 1996 -
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Technical Discussions
S S Ananthan
S S Ananthan
08:53 Dec-06-2002
Accepting cluster pores

Hello,

I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?

Ananthan


 
 Reply 
 
John Woollven
John Woollven
03:30 Dec-06-2002
Re: Accepting cluster pores
: Hello,
.
: I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?
.
: Ananthan
.
You indicate that there "is no construction code for this product" so presumably radiography was carried out as a quality control check. This often leads to problems when defects are disclosed - the fabricator will claim that there were no specifications regarding porosity, so he is in the clear; the customer believes that he has a defective product but cannot cite a code reference and as a result nobody is happy.

There is no easy answer - the decision to accept or reject has to be based on factors such as the type and thickness of material, the operating conditions, and the end usage of the product. Cluster porosity is often just a cosmetic defect but in a pressure retaining component, for example, it may be rejectable.

John


 
 Reply 
 
Nick Welland
Nick Welland
03:36 Dec-06-2002
Re: Accepting cluster pores
: Hello,
.
: I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?
.
: Ananthan
.
Without a code the decision on pass/fail is the responsibility of the cognizant engineer, using information provided by a skilled RT interpreter. It is possible to calculate loss of cross-sectional area by the tedious measuring and counting of pores. Attitudes to cluster porosity vary in codes, depending on whether a "workmanship" philosophy is favoured; this sits well with RT as the flaws most easily detected are those associated with poor technique and/or supervision. Large numbers of pore clusters indicates there is a problem with welder technique which may give rise to questions about the possible presence of flaws that RT is not optimal at finding.
Regards
Nick


 
 Reply 
 
Scott Longstreet
NDT Inspector, Metallographer
Areospace, USA, Joined Apr 2002, 5

Scott Longstreet

NDT Inspector, Metallographer
Areospace,
USA,
Joined Apr 2002
5
03:49 Dec-06-2002
Re: Accepting cluster pores
: : Hello,
: .
: : I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?
: .
: : Ananthan
: .
: When no code or specification is called out, it is our responsibility is to REPORT ALL possible nonconforming issues whitnessed!


 
 Reply 
 
Juan Amado
Engineering, Inspection
Arco Industrial, S.A., Panama, Joined Nov 2001, 44

Juan Amado

Engineering, Inspection
Arco Industrial, S.A.,
Panama,
Joined Nov 2001
44
04:33 Dec-06-2002
Re: Accepting cluster pores
: : : Hello,
: : .
: : : I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?
: : .
: : : Ananthan
: : .
: : When no code or specification is called out, it is our responsibility is to REPORT ALL possible nonconforming issues whitnessed!
.
As an inspector you must be provided with an accept/reject criteria. This can come from a code, or in your case, from the engineer (meaning the person responsible for the construction/fabrication). Design factors such as load and service conditions, as well as safety issues should be taken into account. (A container holding a pressurized lethal substance can't be regarded the same as one holding compressed air).
The inspector should not be put in the position of responsibility regardign the choosing of an accept/reject criteria. As any professional, the inspector may "recommend", based on experience or past similar jobs, but the actual choosing is the responsibility of the engineer in charge.


 
 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
00:10 Dec-09-2002
Re: Accepting cluster pores
Cluster porosity as revealed by RT indicates problem in electrode selection, poor moisture control, poor quality shielding gas, or inadequate shielding or local corrosion of the metal being welded. Acceptance or otherwise of the cluster depends upon the material, stress and other operating conditions. We have some similar experience, whihc we can share with those interested.

Swamy

: : : : Hello,
: : : .
: : : : I am having a component with a lot of cluster pores as seen in RT. There is no construction code for this product. There is no slg / LOP, LOF or any other defects. On what basis do I accept or reject the component ? Is there any way of calculating the acceptabilty ?
: : : .
: : : : Ananthan
: : : .
: : : When no code or specification is called out, it is our responsibility is to REPORT ALL possible nonconforming issues whitnessed!
: .
: As an inspector you must be provided with an accept/reject criteria. This can come from a code, or in your case, from the engineer (meaning the person responsible for the construction/fabrication). Design factors such as load and service conditions, as well as safety issues should be taken into account. (A container holding a pressurized lethal substance can't be regarded the same as one holding compressed air).
: The inspector should not be put in the position of responsibility regardign the choosing of an accept/reject criteria. As any professional, the inspector may "recommend", based on experience or past similar jobs, but the actual choosing is the responsibility of the engineer in charge.
.



 
 Reply 
 

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