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Preheat an essential variable?

Preheat an essential variable?

Preheat an essential variable?

(OP)
Hello, first time posting here. Please bear with me as I don't understand the terminology probably as well as I should.

I have welders who have been tested on B-U 4a-GF as per the lower diagram on page 94 of the 2006 d1.1 manual. The process was GMAW, the groove angle was 45 deg, thus the root opening was 1/4.

This test was done in the 2G postion.

The material used was 1" thick A36. Per the chart on page 63, this is a group II material. Page 67 indicates that 1" A36 requires a category B preheat, in this case a minimum of 50 deg F. When the tests were performed, the ambient air temp was about 80 deg, and was so noted in the documentation we got from the CWI.

Everybody "passed" this test. We were told we were qualified to unlimited thickness for materials in either Group I or Group II. We have been operating under this assumption.


I now have work which is a little thicker. It's 3" thick, and it is A572 grade 50. Again per page 63, this is in the same group as we tested on originally. On page 67 however, table 3.2 says that we must preheat to a minimum to of 225 degrees F.

My CWI is telling me that this is a change in an essential variable, and that I must re-test using A572 coupons (1" thick), preheated to 225 degrees, as we again were only tested at 80 deg preheat originally.

Is he correct in telling me this or not? My customer wants to see copies of my "d1.1 documentation", is my original test OK or do I in fact need to re-test to what the CWI says?

Thanks in advance for any input!

RE: Preheat an essential variable?

Preheat is dependent on thickness.  Your work piece and your test plate aren't the same thickness so some change in preheat is expected.

Table 4.5 Item 35 calls for requalification if you go down too far in preheat, but not for increased preheat.  Under the "more is better" theory of preheat, you actually ran a more conservative test anyway by using 80 degrees instead of 225.

Hg

Eng-Tips policies:  FAQ731-376: Eng-Tips.com Forum Policies

RE: Preheat an essential variable?

Your CWI is way off base on this one.  Preheat is NOT an essential variable for welder qualifications.  Tell your CWI to read Table 4.12 in AWS D1.1.

RE: Preheat an essential variable?

As previously pointed out, preheat is not an essential variable for operator qualification. Perhaps your CWI is confusing this with the requirements for re qualification of a PQR in impact tested situations.  If CVN's are required, preheat is an essential variable for procedure qualification.

RE: Preheat an essential variable?

I agree that your welders are qualified for a range of thicknesses from 1/8 to unlimited.

The preheat is a variable for the WPS, not the welders. They must work within the parameters of the WPS, which includes preheat that is dependent on the base metal and the thickness.

As long as your WPS and your practices comply with the limits of a prequalified WPS, you are covered. No testing or qualification of the WPS is required as long as you meet the limits of prequalification as listed in the Annex of D1.1.

Best regards - Al

RE: Preheat an essential variable?

Does ASME VIII permit use of the AWS pre-qualified WPSs?

Joe Tank

RE: Preheat an essential variable?

You may use SWPS with several conditions and limitations.  Suggest you carefully review QW 500.

RE: Preheat an essential variable?

Welltek,
Thanks, I will go look it up.  I don't recall anything in ASME VIII that specifically permits them to be used.

SWPSs are not permitted for API tank construction.  API-650 permits SWPS for misc structral items only, but nothing that welds to the shell, bottom or roof.

Joe Tank

RE: Preheat an essential variable?

Joe,
You might want to review Par UW-28(d)in Sec VIII for a little further info.

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