Inspection Frequency
Inspection Frequency
(OP)
This might be too simple for those gifted in stats. For me, not so simple.
We inspect 5% of our pipe prior to PWHT. We inspect 100% of it after PWHT. The second inspect shows a defect rate of 6%. The first inspection shows a defect rate of 0%.
I am looking for the probability/likelyhood that we'll catch a defect at the first inspection. (ie. we've made 100 - seems like a small enough number that we simply picked 5 good pieces for primary inspection). After how many can I expect to see a failure ont he first inspection?
Note: I am assuming all defects are present at the first inspecion.
We inspect 5% of our pipe prior to PWHT. We inspect 100% of it after PWHT. The second inspect shows a defect rate of 6%. The first inspection shows a defect rate of 0%.
I am looking for the probability/likelyhood that we'll catch a defect at the first inspection. (ie. we've made 100 - seems like a small enough number that we simply picked 5 good pieces for primary inspection). After how many can I expect to see a failure ont he first inspection?
Note: I am assuming all defects are present at the first inspecion.





RE: Inspection Frequency
RE: Inspection Frequency
We are trying to determine if the PWHT:
- causes the cracking
- makes the cracking visible
- has no effect (ie. it was there before)
The 5% inspection rate is theoretically random. All pieces are now being inspected prior to PWHT.
RE: Inspection Frequency
TTFN
RE: Inspection Frequency
corus
RE: Inspection Frequency
I am working in ISO domaine so I can direct you towards the ISO 2859(1989)part 1,2,3 and ISO 3951. There is surely an ASTM issue.An odd reading with terrific effect!
m777182
RE: Inspection Frequency
Cheers
Greg Locock
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