ASME BPVC Section IX QW-452.3, large diameter 2

[HgTX]

As I read QW-452.3, ANY pipe over NPS 2-1/2 qualifies for diameter down to NPS 2-1/2.

Which means, in theory, someone could weld pipe with 6 ft diameter and qualify to weld 3" diameter. They'd be a long time welding, but it looks like it would be legal.

At what point does pipe become plate? Plate tests qualify pipe over 24", but have limited application for pipe under 24". But there appears to be no restriction on how big that qualification pipe can be, and no connection of qualified range back to actual diameter welded as long as it's over NPS 2-1/2. If pipe welding truly takes a different skill from plate welding, shouldn't there be a max diameter based on something other than the practicality of how long they can afford to spend welding the sample?

Am I missing something?

Hg

 

[metengr]

If you review QW-469.1, it is clear the code committee views welding on pipe over 24" diameter as being similar to welding on flat plate for a performance qualification. Below 24" OD, the Code committee views welding on pipe OD as having no significant impact on performance qualification down to 2 - 7/8" OD. I would imagine this requirement was arrived at based on significant input from industry code volunteers. I am not sure this completely answers your question, but given cost and handling of large diameter coupons >24" OD for welder performance qualification, this must have been the compromise.

 

[metengr]

Sorry, this should be QW-461.9, and not 469.1.

 

[HgTX]

There's what's more or less implied by common sense, and there's what the code actually says.

What QW-461.9 says is that if your production piece has diameter over 24", you have the option of treating it as plate with regard to who's qualified to weld it.

But it doesn't go the other way. It doesn't say that if your test piece has diameter over 24", you have to treat it as plate with regard to what that welder is then qualified to weld; QW-452.3 does not give an upper limit on outside diameter of test coupon. Normally you wouldn't want to waste a whole lot of time welding a huge test coupon, but if you had a 6' diameter 5G or 6G pipe to weld for production anyway, in theory you could use that per QW-304.1 to qualify that welder to weld 3" pipe at a later date.

Maybe they meant the large-diameter test coupon range to be from 2-7/8" to 24", but they didn't say it.

Hg

 

[DekDee]

Hg,
Two things come to mind in response to your question.
Firstly,
There is no difference in welding a 2", 6" or 6' diameter test coupon in the 5G position except the transition between the positions.
All three diameters still have F, V & O but the transition between these positions changes more rapidly the smaller the diameter of the test coupon.
That is why the code committee gives a wider range of qualification for coupons less than 2 7/8" OD due to the increased difficulty of the smaller diameter pipes.
As the diameter increases the speed of this transition lessens and the welding "supposedly" becomes easier but you still have to weld in all three positions.
A competent welder should be able to weld a 5G coupon vertical up with SMAW (as an example) without changing the amps from the bottom to the top on any diameter coupon - the only change will be his/her body position and electrode angle.

Secondly,
ASME IX contains minimum requirements and does not excuse the manufacturer from executing "sound engineering judgement".
If you think you can take a welder who has successfully welded a 6' diameter test coupon and have him welding 3" production welds it is your call and you are then responsible as the manufacturer for the quality of his work.
I have spent approx 30 years working with ASME IX on large scale O&G / LNG projects and just about every project I have been on the client will require a 2" carbon steel GTAW test and a 2" stainless steel GTAW test.
Why bother ? A P1 already qualifies you for the P8 so why do an additional test ?
Because the code gives minimum requirements and the client is using "sound engineering judgement" to ensure they are confident the welders are competent on both materials.

Hope that helps,
Cheers,
Dek Dee

 

[HgTX]

Transition rather than diameter is helpful, thanks.

Hg