By 3.1 Inspector
Date 08-20-2008 14:27
Be carefull with your hair, you might loose it soon enough :)
I will do my best to sort it out for you.
A pWPS (preliminary welding procedure specification) is written by the welding engineer, based on that pWPS you weld a test coupon. You record all relevant data during welding.
Thoose data is then written on the PQR (procedure qualification record) based on the data recorded you can the write a WPS (welding procedure specefication) within the parameters outlined in the code you are testing to.
When all that is in place you will have to certify the welder with a WQT (welding qualification test) the PQR and WQT can be done on the same test coupon.
As far as I remember thickness is not an issue in regards to a WQT, but the deposited weld metal is.
If the welder does his test on a - this is an example - 2 inch thick plate/pipe, he deposit 2 inch weld metal (he deposit the same thickness as the coupon is thick - NOT taking into account depth of penetration or weld reinforcement)
If - still example - the code state that when depositing 2 inch of weld metal, the welder will be qualified x2 (4 inch) which mean that he can ONLY deposit 4 inch of weld metal, but in theory the groove can be 8 inch thick - but he is only allowed to weld up tp 4 inch - and another welder has to take over :)
Note that the above is only an example...
Now that I think about it, I think that if the welder deposit more than 3 layers he is qualified unlimited, I am not sure on this one....I suddenly remember something about 13mm.
It might be if the coupon's thickness is more than 13mm and he deposit a minimum of 3 layers, he is qulified unlimited.
If I left something out, I am sure I will be corrected by other members :)
Not a "dummy" at all. This is a subject that I think many people are confused on.
Here are some background facts. [edit] Based on what I understand the code to say in many cases. I have on more than one occasion come to realize that interpretations from someone on a code committee may very well be different than mine. I strongly suggest looking these ideas I have stated below to assure that what YOU do is correct. The statements below are made in the context of this thread[/edit]
1) The ranges of qualification for performance based on the test below are different for the welder than the procedure.
2) The welder for instance has no limit on the maximum base metal thickness he/she can weld on. The WPS is limited to 2T.
3) The welder can weld ANY thickness but can only deposit up to 2t of the deposited metal used for each process.
4) The procedure can be written for 7018 open root but the welder must use GTAW (I am making an assumption that the test was GTAW/SMAW)
5) The welder can weld on Pnumbers 1thru11 amd Nickel alloys of P4X p numbers. The WPS is limited to P1 to P1
6) The welder can weld on material with ANY amount of Preheat, Interpass, PWHT. The WPS may need to be requalified depending upon the changes and requirements for impact testing.
7) The welder must weld uphill. The WPS could be written for downhill (unless impact testing is an issue )
8) For performance qualification ASME Lists 7 variables for SMAW. For Procedure qualification there are 11 essential, 17 Non-Essential, and 10 Supplementary essential variables.
9) The Welder is qualified down to 1" OD but the WPS may be written to any diameter.
10) If a welder deposits 1/2" of weld metal with a minimum of 3 passes he is qualifiedd for unlimited deposited weld metal, the procedure in the same case would be limitedd to 2 times t hat thickness or less depending on the process.
So as you can see there are some differences. Base metal thickness is NOT listed as a variable for performance qualification. Diamter is.
Hope this helps. If I had more time i'd throw some code paragraphs in there. Its in there .
Gerald