We have a vendor that wants to use an existing prequalified WPS to build something for us with charpy requirements. They would like to run a small coupon per their existing prequalified WPS just big enough to run charpy tests, staple the results to the back of their prequalified WPS call it good to go (assuming it passes). In theory I may not have a problem with that but, I may have to convince our customer as well.
The most relevant section of code I found is, "4.35.3 When CVN testing is a requirement and a qualified WPS exists which satisfies all requirements except for CVN testing, it shall be necessary only to prepare an additional test weldment with sufficient material to provide the required CVN test specimens. The test plate shall be welded using the WPS, which conforms to the limits of Tables 4.1, 4.2, and 4.5, plus those supplementary essential variables applicable only to CVN testing (Table 4.6). A new or revised PQR shall be prepared and a new or revised WPS written to accommodate the qualification variables for CVN testing."
I would like them to treat their coupon like a normal weld test, recording all relevant, parameters and then compare their actuals to those on their prequalified WPS in conjuction with Table 4.6, Supplementary Essential Variables for CVN testing, and if they qualified all the ranges allowed on their existing WPS then that may be okay. If not, I'd like a new WPS with tighter allowances based on their psuedo-PQR. Although, this may not comply with the code exactly. Any thoughts?
By Nanjing
Date 03-11-2009 13:57
You are right in my opinion. You need to record all required welding parameters on a PQR and develop a WPS from this. I think you need to do all the other mechanical tests eg tensiles and bends, they cost buttons, I am sure it must be in the spec somewhere, perhaps someone else will tell us where.
Rick,
The difference is in prequalified and qualified. You state that your vendor has "an existing prequalified WPS", while the 4.35.3 provision states "a qualified WPS exists" (I've put in the bold).
If you need impact testing, you need to qualify the WPS, period. You can't start out with a prequalified WPS. That means running all of the necessary test plates, recording all of the parameters, doing all the tests, and if it meets the requirements writing a PQR. You can then use this to write a WPS.
Mankenberg
I like the idea that the use of "qualified" opposed to "prequalified" is significant in 4.35.3. Hmmmm.
By Nanjing
Date 03-12-2009 13:52
Kipman, why did you not just cut and paste my answer?
Nanjing,
Your answer was correct, and essentially I did cut and paste it. I just wanted to add and highlight for the gentleman that 4.35.3 does not apply in his case as he is dealing with a prequalified WPS, and not a previously qualified WPS.
Cheers,
Mankenberg
