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- since 1996 -

Materials Research Institute
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3018 views
Technical Discussions
Sanjoy Das
R & D, NDT Manager
Bhabha Atomic Research Centre, India, Joined Apr 2008, 3

Sanjoy Das

R & D, NDT Manager
Bhabha Atomic Research Centre,
India,
Joined Apr 2008
3
06:29 May-27-2008
Aceptanc code for radiography!

What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.


    
 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 519

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
519
09:38 May-27-2008
Re: Aceptanc code for radiography!
Rejection or repair does mean economic loss, and there are few operators who will have never experienced varying degrees of pressure to sign off on work. I have known people who have lost jobs over it. It is why we all sign up to a code of ethics when we get our certs.

The acceptance criteria in the codes are generally chosen to take account of the operating factors. Defects which are likely to grow, such as surface breaking cracks, are generally treated much more conservatively than porosity or inclusions, which in many circumstances wont. committees spend a lot of time considering these criteria.

If you feel that defects are causing rejection that have no possibility, in the application involved, of growing to a critical size, then it is possible that an inappropriate code is being used - But that is a matter for the customer to decide - All you can do is honestly apply the criteria you are given.


Good luck

Joe

----------- Start Original Message -----------
: What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
------------ End Original Message ------------




    
 
 
collin maloney
NDT Inspector, - Plant Inspector
Applus RTD, Australia, Joined Nov 2000, 147

collin maloney

NDT Inspector, - Plant Inspector
Applus RTD,
Australia,
Joined Nov 2000
147
03:19 Jul-12-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
------------ End Original Message ------------

Sanjoy,
there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments


    
 
 
Nigel
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1094

Nigel

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
01:18 Jul-15-2008
Re: Aceptanc code for radiography!
Sanjoy

Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.

----------- Start Original Message -----------
: : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: Sanjoy,
: there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
------------ End Original Message ------------




    
 
 
tj
tj
02:05 Jul-24-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: Sanjoy
: Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : Sanjoy,
: : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
------------ End Original Message ------------

Nigel,

Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).


    
 
 
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
00:40 Jul-24-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: : Sanjoy
: : Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : : Sanjoy,
: : : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
: Nigel,
: Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).
------------ End Original Message ------------

Dear colleagues:
I think there are two separate ideas at play here, both of which deserve study.
The first is the basis for establishing acceptance criteria within a given code, which clearly should result from a balanced approach between suitability for service on one hand, and the cost to procure a certain quality level on the other. The trick here is that the suitability for service issue must be considered, from the stand point of the code, to hold valid under a vast array of service conditions, which in turn will weight more towards the overly stringent acceptance criteria side for many particular applications.

The other concept at play here is that once a buyer/owner specifies the code, standard or level of quality to be met on his purchase (or by his provider) on a contractual document, then the level of quality becomes a condition to be met regardless of whether or not it exceeds the service requirements for the particular item. In other words, they want it the way they want it because it is so specified and agreed to. It would be like a contractor saying: “I know this car I’m giving you is not a Mercedes Benz like you asked, but it’s still a good car and will take around, to wherever you want to go” and the purchaser will respond, “Yeah, but it’s not a Mercedes!, like we asked for”. Furthermore, when the purchase or contract is the result of a bid process, it is assumed that the other prospective contractors, at least in theory, would have provided the quality level required at bidding and thus acceptance of a lower quality level based on suitability for service would be an unfair practice to them.

Regards,
Juan Amado


    
 
 
tj
tj
01:20 Jul-25-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: : : Sanjoy
: : : Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : : : Sanjoy,
: : : : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
: : Nigel,
: : Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).
: Dear colleagues:
: I think there are two separate ideas at play here, both of which deserve study.
: The first is the basis for establishing acceptance criteria within a given code, which clearly should result from a balanced approach between suitability for service on one hand, and the cost to procure a certain quality level on the other. The trick here is that the suitability for service issue must be considered, from the stand point of the code, to hold valid under a vast array of service conditions, which in turn will weight more towards the overly stringent acceptance criteria side for many particular applications.
: The other concept at play here is that once a buyer/owner specifies the code, standard or level of quality to be met on his purchase (or by his provider) on a contractual document, then the level of quality becomes a condition to be met regardless of whether or not it exceeds the service requirements for the particular item. In other words, they want it the way they want it because it is so specified and agreed to. It would be like a contractor saying: “I know this car I’m giving you is not a Mercedes Benz like you asked, but it’s still a good car and will take around, to wherever you want to go” and the purchaser will respond, “Yeah, but it’s not a Mercedes!, like we asked for”. Furthermore, when the purchase or contract is the result of a bid process, it is assumed that the other prospective contractors, at least in theory, would have provided the quality level required at bidding and thus acceptance of a lower quality level based on suitability for service would be an unfair practice to them.
: Regards,
: Juan Amado
------------ End Original Message ------------

Head on the nail Juan!

Regardless of what anyone believes to be sufficient for the intended service conditions of the part inspected, the design has already been agreed upon and acceptance or rejection criteria set. At this point, speculation of the performance of said part is completely irrelevant.


    
 
 
Nigel
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1094

Nigel

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
08:03 Jul-30-2008
Re: Aceptanc code for radiography!
tj

Which part of my response deserves the unusual description of "excitingly imaginitive" (sic)? I admit that I could have been more concise (unfortunately not one of my saving graces!) by stating, "acceptable risk at commercial cost". However often our words do not necessarily convey quite our desired intention.

Sanjoy asked, "What is the basis of making RT acceptance criteria" and "What is the technical basis for deciding acceptance parameter" with the inference from his next sentence that he is specifically interested in how Code "workmanship criteria" have been derived. Your indication to him for the basis of deriving "fitness-for-purpose" acceptance criteria being "very expensive" is a confirmation rather than a denial of my contention that workmanship criteria is based on acceptable risk at commercial cost.

I answered through my prior reading of some ASME technical papers on this subject which Sanjoy may not have seen. The description of "workmanship criteria" is commonly used for traditional ASME Code acceptance. The rediographic acceptance criteria ARE based on what quality a proficient welder working in the right conditions to a proven weld procedure should be capable of producing on a regular commercial basis. If otherwise then the costs of fabrication would rocket enormously.

I am a little bit confused by your terminology (platform, arch interface) however I have quoted from a reliable material scientist academic with a wealth of practical experinece (Gordon) regarding flaws, SCF's and the probability of propagation and my remarks are not my own but his. I did not say that no pore could propagate nor did I say that all propagating cracks will be arrested by pores. I dont know what "given circumstances" you may have in mind, tj, but they must be highly unusual and therefore deserving of special rather than generic acceptance criteria to cause a spherical embedded flaw in a properly-designed conventional engineering steel boiler or PV weld working within its design operating parameters to propagate.

I have no argument with Juan's contention that once agreed then the acceptance criteria should be upheld. But does this mean arguing over the actual diameter of a pore or insisting on the best possible radiography in order to detect all present flaws, especially in the critical root zone, which would fail the acceptance criteria if detected? How many quick and chapo small-bore contact shots are allowed by NDT supervisors, Level III's and managers due to commercial expediency? How much (or rather how little) focus is placed on best radiographic practice with no concern for quality or safety or detecting existing Code rejectable flaws. Its another acceptable risk (or what we think we can get away with) scenario!

----------- Start Original Message -----------
: : Sanjoy
: : Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : : Sanjoy,
: : : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
: Nigel,
: Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).
------------ End Original Message ------------




    
 
 
tj
tj
03:16 Jul-31-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: tj
: Which part of my response deserves the unusual description of "excitingly imaginitive" (sic)? I admit that I could have been more concise (unfortunately not one of my saving graces!) by stating, "acceptable risk at commercial cost". However often our words do not necessarily convey quite our desired intention.
: Sanjoy asked, "What is the basis of making RT acceptance criteria" and "What is the technical basis for deciding acceptance parameter" with the inference from his next sentence that he is specifically interested in how Code "workmanship criteria" have been derived. Your indication to him for the basis of deriving "fitness-for-purpose" acceptance criteria being "very expensive" is a confirmation rather than a denial of my contention that workmanship criteria is based on acceptable risk at commercial cost.
: I answered through my prior reading of some ASME technical papers on this subject which Sanjoy may not have seen. The description of "workmanship criteria" is commonly used for traditional ASME Code acceptance. The rediographic acceptance criteria ARE based on what quality a proficient welder working in the right conditions to a proven weld procedure should be capable of producing on a regular commercial basis. If otherwise then the costs of fabrication would rocket enormously.
: I am a little bit confused by your terminology (platform, arch interface) however I have quoted from a reliable material scientist academic with a wealth of practical experinece (Gordon) regarding flaws, SCF's and the probability of propagation and my remarks are not my own but his. I did not say that no pore could propagate nor did I say that all propagating cracks will be arrested by pores. I dont know what "given circumstances" you may have in mind, tj, but they must be highly unusual and therefore deserving of special rather than generic acceptance criteria to cause a spherical embedded flaw in a properly-designed conventional engineering steel boiler or PV weld working within its design operating parameters to propagate.
: I have no argument with Juan's contention that once agreed then the acceptance criteria should be upheld. But does this mean arguing over the actual diameter of a pore or insisting on the best possible radiography in order to detect all present flaws, especially in the critical root zone, which would fail the acceptance criteria if detected? How many quick and chapo small-bore contact shots are allowed by NDT supervisors, Level III's and managers due to commercial expediency? How much (or rather how little) focus is placed on best radiographic practice with no concern for quality or safety or detecting existing Code rejectable flaws. Its another acceptable risk (or what we think we can get away with) scenario!
: : : Sanjoy
: : : Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time the Code was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the partwithout taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : : : Sanjoy,
: : : : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
: : Nigel,
: : Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).
------------ End Original Message ------------

Nigel,

I believe, due to the confusing format of these forums, you may have read the "very expensive" post as mine. It was another persons post. However, I have not seen these technical papers from ASME. I do not pretend to be an engineer, but I would like to believe that acceptance criteria is based on service design and not average welder profficiency. I would also like to point out that I was talking about a concentrated cluster of discontinuities as a possible weakening source of material. Yes, the diameter of even a single isolated pore is definitely critical in acceptance of the radiograph. As for quality vs. expediency, I think you know where I stand on that.



    
 
 
raul marcano
raul marcano
05:31 Sep-21-2008
Re: Aceptanc code for radiography!
----------- Start Original Message -----------
: : tj
: : Which part of my response deserves the unusual description of "excitingly imaginitive" (sic)? I admit that I could have been more concise (unfortunately not one of my saving graces!) by stating, "acceptable risk at commercial cost". However often our words do not necessarily convey quite our desired intention.
: : Sanjoy asked, "What is the basis of making RT acceptance criteria" and "What is the technical basis for deciding acceptance parameter" with the inference from his next sentence that he is specifically interested in how Code "workmanship criteria" have been derived. Your indication to him for the basis of deriving "fitness-for-purpose" acceptance criteria being "very expensive" is a confirmation rather than a denial of my contention that workmanship criteria is based on acceptable risk at commercial cost.
: : I answered through my prior reading of some ASME technical papers on this subject which Sanjoy may not have seen. The description of "workmanship criteria" is commonly used for traditional ASME Code acceptance. The rediographic acceptance criteria ARE based on what quality a proficient welder working in the right conditions to a proven weld procedure should be capable of producing on a regular commercial basis. If otherwise then the costs of fabrication would rocket enormously.
: : I am a little bit confused by your terminology (platform, arch interface) however I have quoted from a reliable material scientist academic with a wealth of practical experinece (Gordon) regarding flaws, SCF's and the probability of propagation and my remarks are not my own but his. I did not say that no pore could propagate nor did I say that all propagating cracks will be arrested by pores. I dont know what "given circumstances" you may have in mind, tj, but they must be highly unusual and therefore deserving of special rather than generic acceptance criteria to cause a spherical embedded flaw in a properly-designed conventional engineering steel boiler or PV weld working within its design operating parameters to propagate.
: : I have no argument with Juan's contention that once agreed then the acceptance criteria should be upheld. But does this mean arguing over the actual diameter of a pore or insisting on the best possible radiography in order to detect all present flaws, especially in the critical root zone, which would fail the acceptance criteria if detected? How many quick and chapo small-bore contact shots are allowed by NDT supervisors, Level III's and managers due to commercial expediency? How much (or rather how little) focus is placed on best radiographic practice with no concern for quality or safety or detecting existing Code rejectable flaws. Its another acceptable risk (or what we think we can get away with) scenario!
: : : : Sanjoy
: : : : Generic acceptance criteria from major codes (ASME VIII, B31.3 are sometimes called "workmanship criteria" based on the quality of welders work considered acceptable at the time theCode was evolved. I suppose repairs required by the Code would be a kind of penalty which would raise an economic cost and thus clearly flagging poor welder performance to the fabricator management. Academics with practical experience such as J.E. Gordon inform us that rounded flaws such as spherical porosity have very low stress concentration factors even potentially being crack-arrestors, yet if a pore exceeds 4mm diameter (or 6mm if isolated or 10mm if thickness > than 51mm) it is cause for repair iaw ASME VIII. A way of looking at this again is not that it will necessarily cause weld failure but that it is necessary to highlight the welder's poor technique and workmanship by inserting and not removing such a large readily detectable flaw.
: : : : : : What is the basis of making Radiography acceptance(RT) criteria? All of the codes specify max acceptable flaw sizes. But in service it may not grow and disrupt the perfonance. In this case rejection/repair means considerable economic loss. But code simply rejects the part without taking consideration of it's fracture toughness parameter. Anybody can tell me what is the techincal basis for deciding acceptance parameter.
: : : : : Sanjoy,
: : : : : there are codes such as API 1104 / DNV OS 2000 etc that allow for ECA's and fracture mechanics as an acceptance basis. This is however very expensive, and usually a luxury afforded by oil and gas project developments
: : : Nigel,
: : : Your theory is excitingly imaginitive. However, you have left out a fundamental promise to your formula. You should well know that ANY platform (interface) can result in fracture propagation under given circumstances. Yes, the arch interface of porosity may beat the odds and intercept an incoming crack, however, it is more likely going to be the origin of a problem especially concentrated (which is the overall focus for acceptance of rounded indications per ASME VIII).
: Nigel,
: I believe, due to the confusing format of these forums, you may have read the "very expensive" post as mine. It was another persons post. However, I have not seen these technical papers from ASME. I do not pretend to be an engineer, but I would like to believe that acceptance criteria is based on service design and not average welder profficiency. I would also like to point out that I was talking about a concentrated cluster of discontinuities as a possible weakening source of material. Yes, the diameter of even a single isolated pore is definitely critical in acceptance of the radiograph. As for quality vs. expediency, I think you know where I stand on that.
------------ End Original Message ------------




    
 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1094

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
10:59 Feb-12-2009
Re: Aceptanc code for radiography!
In Reply to Sanjoy Das at 06:29 May-27-2008 (Opening).

In response to Sanjoy's original post, I have now found one of the technical papers which I referred to in an earlier thread post and I hope that others interested in derivation of Acceptance Criteria will be able to seek it out.

"Technical basis for ASME Section V!!! Code Case 2235 on ultrasonic examination of welds in lieu of radiography." - Rana M, Cowfer D, Hedden O and Boyce R.

It is published in PVP-Vol407, Pressure Vessel and Piping Codes and Standards by ASME International

    
 
 

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