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- since 1996 -

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X-ray and CT based NDT systems for a wide range of industrial applications.

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Technical Discussions
Jimbo Q.
Jimbo Q.
00:45 Oct-22-2007
Hypothetical Question

I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.

The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.

What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
Is this rejectable or acceptable?

This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.

Thanks in advance.


    
 
 
Michel
NDT Inspector,
consultant, Canada, Joined Sep 2006, 822

Michel

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
822
04:32 Oct-22-2007
Re: Hypothetical Question
----------- Start Original Message -----------
: I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.
: The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.
: What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
: Is this rejectable or acceptable?
: This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.
: Thanks in advance.
------------ End Original Message ------------


I believe this to be rejectable. You state that both length of concavity and density requirements needs to be met. Well it is. Your concavity is 3/4" and your density at one point is below that of the base metal. You have exceeded both requirements.




    
 
 
chris s
chris s
00:46 Oct-23-2007
Re: Hypothetical Question
----------- Start Original Message -----------
: I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.
: The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.
: What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
: Is this rejectable or acceptable?
: This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.
: Thanks in advance.
------------ End Original Message ------------

if your working with that small of a range of densities,then you might want to factor in the accuracy of the densitometer. it should be calabrated, and have an accuracy of + and - of ????


    
 
 
Michel
NDT Inspector,
consultant, Canada, Joined Sep 2006, 822

Michel

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
822
08:39 Oct-23-2007
Re: Hypothetical Question
----------- Start Original Message -----------
: : I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.
: : The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.
: : What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
: : Is this rejectable or acceptable?
: : This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.
: : Thanks in advance.
: if your working with that small of a range of densities, then you might want to factor in the accuracy of the densitometer. it should be calabrated, and have an accuracy of + and - of ????
------------ End Original Message ------------

Chris,

I understand what you're saying, but all standards have specific value for everything and you have to have a cut off limit somewhere. I believe that whomever wrote those standards have already factored in these factors otherwise, it would become a nightmare to meet the codes. And what would happended if your film is read by someone else? If the accuracy of their densitometer is different than yours, your film maybe rejected!!! Would that be fair and accurate?


    
 
 
David
David
00:17 Oct-24-2007
Re: Hypothetical Question
----------- Start Original Message -----------
: : : I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.
: : : The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.
: : : What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
: : : Is this rejectable or acceptable?
: : : This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.
: : : Thanks in advance.
: : if your working with that small of a range of densities, then you might want to factor in the accuracy of the densitometer. it should be calabrated, and have an accuracy of + and - of ????
: Chris,
: I understand what you're saying, but all standards have specific value for everything and you have to have a cut off limit somewhere. I believe that whomever wrote those standards have already factored in these factors otherwise, it would become a nightmare to meet the codes. And what would happended if your film is read by someone else? If the accuracy of their densitometer is different than yours, your film maybe rejected!!! Would that be fair and accurate?
------------ End Original Message ------------


If you are using the same densitometer at the same time then any errors will be the same, especially if measuring densities so close to each other. So, if the readings for base metal and concavity are compared any difference should be identical regardless of the absolute value. Your 2.54 could be actually 2.49 or 2.59 and the 2.43 either 2.48 or 2.38 so they don't (quite) overlap anyway if your densitomer is correctly calibrated (ASTM E1079) so should not be an issue.
If you are concerned about film rejection in general for density then you shouldn't really be shooting so close to the limit so the small differences between different densitometers shouldn't be a factor.
As for accept reject, I believe the example given above is rejectablel. Look at the burn through criteria referenced in the internal concavity section and it says that that burn through maximum dimension exceeds 1/4" and ANY portion has a density exceeding base material is rejectable, it doesn't say that the high density area has to be above 1/4" long.


    
 
 
stotts
stotts
05:37 Nov-09-2007
Re: Hypothetical Question
----------- Start Original Message -----------
: : : : I have a hypothetical question I'd like to get some opinions on regarding flaw sizing (RT). Let's say you are working to API-1104 and you find some root concavity.
: : : : The accept/reject criterai for concavity is the same as burn through. Must be over 1/4" and the density must be greater than the thinnest base material. It must meet both requirements to be considered rejectable. Not just one.
: : : : What if the concavity was 3/4" long and the density of the concavity was 2.54 and the density of the base material was 2.43. However, only less than 1/4" of the concavity was over the density of the base material. The remaining concavity was less than the density of the base material.
: : : : Is this rejectable or acceptable?
: : : : This question was posed to me and I think it was a legitimate question and I'd like others opinions on it.
: : : : Thanks in advance.
: : : if your working with that small of a range of densities, then you might want to factor in the accuracy of the densitometer. it should be calabrated, and have an accuracy of + and - of ????
: : Chris,
: : I understand what you're saying, but all standards have specific value for everything and you have to have a cut off limit somewhere. I believe that whomever wrote those standards have already factored in these factors otherwise, it would become a nightmare to meet the codes. And what would happended if your film is read by someone else? If the accuracy of their densitometer is different than yours, your film maybe rejected!!! Would that be fair and accurate?
:
: If you are using the same densitometer at the same time then any errors will be the same, especially if measuring densities so close to each other. So, if the readings for base metal and concavity are compared any difference should be identical regardless of the absolute value. Your 2.54 could be actually 2.49 or 2.59 and the 2.43 either 2.48 or 2.38 so they don't (quite) overlap anyway if your densitomer is correctly calibrated (ASTM E1079) so should not be an issue.
: If you are concerned about film rejection in general for density then you shouldn't really be shooting so close to the limit so the small differences between different densitometers shouldn't be a factor.
: As for accept reject, I believe the example given above is rejectablel. Look at the burn through criteria referenced in the internal concavity section and it says that that burn through maximum dimension exceeds 1/4" and ANY portion has a density exceeding base material is rejectable, it doesn't say that the high density area has to be above 1/4" long.
------------ End Original Message ------------

reject,concavity length against density makes for a thin argument



    
 
 
Vishal Gupta
Vishal Gupta
16:21 Sep-08-2013
Re: Hypothetical Question
In Reply to Jimbo Q. at 00:45 Oct-22-2007 (Opening).

I believe the situation posted by you is rejectable because the discontinuity shall meet all the acceptance criteria to be marked as acceptable. The situation doesn't meet both the citeria (length and density) so should be rejected.

    
 
 

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