NDT percentage clarrification 1

[NimChimpsky]

Hi guys,

A real quick one...

If the level of NDT of a weld is defined as 20% does this mean that 1 in 5 of welded joints needs to be tested or that 20% of every joint needs to be tested?

For example,

If there are 10 butt welds that require 20% MPI, does this imply that 2 out of 10 of the welds need to be fully tested or that a 1/5th of every joint needs to be tested?


Thanks,

 

[SectionIX]

In the context you have described, it is based upon the complete examination of a weld. If there are 10 butt welds that require 20% MPI, at least two complete welds are examined.

If related to spot radiography as described in ASME VIII, Division I, see UW-52.

 

[weldstan]

Generally, it would be 1 weld in 5 at random; however, the contract wording must be clear to avoid confusion - and your wording is confusing. The NDE level "of a weld" (singular) does not necessarily mean the NDE level of welds in a system.

 

[DekDee]

You don't mention code but B31.3 (as an example) may require 5 x welds out of 5 (100%) if there were 5 x different welders,
Cheers,
DD

 

[RolMec]

Over here it's relative to the weld volume or lentgth (for one weld type / thickness). So of 10 assemblies 2 are fully tested (which is the effective approach). If by malchance / contract a requirement of "20% of every weld" is to applied, the respective cost will show up & this needs to be carefully handled in advance of making the manufacturing contract.
Beware of clauses alike "20% of full length of the weld" in your clients spec., because these could be read as "of every weld", whereas the quote of the manufacturer / lab by default would most probably be based on the effective approach.
Regards

 

[yaschief]

The way I have interpreted this spec is 20% of all welds to receive MPI translates to 1 in 5. But also reference the requirements for failure which may increase the amount of welds to be inspected.

 

[NimChimpsky]

Thank you for the comments. I've got a good idea of what is required now. Many Thanks guys,