Strange !! IMPACT Test question

[Flareman]

This is one of those times when I think I already know the anwer but someone has shaken me up.. so I'll ask anyway.

My client required impact test to -50 degC (ie: -58 degF). My fabricator already has procedures tested to -65 degF (ie:-53.9 degC) which we submitted to the client (WPS and PQR). They were rejected for wrong temperature ????

Is there something I'm missing here or is it just my client being silly?


David

 

[unclesyd]

Technically he is correct.

But I don't think he understands the reasons for and methods of impact testing.

Unless you are designing to a very specific temperature or using a very specific material the FTE to NDT is on an approximate 45° slope. This coupled with a normal scatter pattern of impact testing is usually acceptable by all.
The accepted impact values of all materials are averages.

The only reason I could see requesting same would be that your numbers are vert, very close to minimum accepted values he is looking for.

 

[GRoberts]

I know this is the AWS forum, but the only place I can find at the moment that specifically allows lower temperatures to be used is in ASME VIII UG-84. They probably had to put it in there when some less than knowledgable people were complaining that tests were done at a lower temperature than specified. I have seen it done all the time on weld procedures, and no one has ever complained about it to my knowledge. As far as I know on ferrous materials, there is never any situation where a colder temperature makes the test easier, so your client is picking nits, in my opinion. What kind of material are you fabricating? If it is non-ferrous, I'm not as sure if all the same rules apply.

 

[Flareman]

Thanks for your input chaps.
Yes I think he is nit picking.
We're looking at A 516 Gr60 base (also impact tested) and ENi1K filler; SAW.
Thanks for the ref to UG-84, that's just what I need.


David

 

[sayee1]

David
One other time when there is possibly a reduction in temperatures is when subsize specimens are used because of lower thickness of the PQR. Please check if the specimen on the PQR was still a 10mm x 10mm x 55mm. If not check if the correct correction temperature was applied!!

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
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