American Welding Society Forum
By Toey TNDT
Dear All ,
I'm having a confuse for a little bit words
If WPS required Preheat and/or Postweld Heat treatment
Does WQT need to Preheat and/or Postweld Heat treatment , Doesn't WQT ?
Many times when i witness WQT some representative recommended Preheat and/or Postweld Heat treatment accordance with WPS
Kind Regards ,
For WQT, Preheat and Postweld Heat Treatment aren't essential variables, which means you don't have to do it.
The recommendation you're being given could be for the type of materials you're welding, to avoid cracking (which would fail the welder's qualification without him being at fault).
A good example is the P91 Steel which is very prone to cold cracking, even if cooled at calm air. For this one you need to preheat and postweld heat treatment even for welder qualifications
Interesting, lol:. There are many alloy materials that require heat treatment in WPS. There are many welders to be qualified, you need to consider the volume of test coupons that need to be PWHT if you allow this to happen.
What is your take if the contractor decided to perform RT without PWHT and it shows accepted result?
If the contractor opt to qualify their welders based on initial production welding of P91, which will come first PWHT or RT? If the RT result passed before PWHT, is it enough without the PWHT?
What if you proceed with PWHT before RT and the results show unacceptable due to weld slag but no cracks.
Is it unfair to the welder and the contractor boss? have you heard the slag becomes larger in size after PWHT? The contractor boss may say I should not have wasted money doing PWHT on rejected weld
What ASME IX says "when performance qualification is done in accordance with a WPS or SWPS that requires a preheat or postweld heat treatment, these may be omitted"
I'm not suggesting that he should do what he's being recommended. I'm just stating possible causes for the recommendation being made.
ASME IX does say it may be omitted, and you can and should present that information to your client.
I do not know if there are many welders to be qualified, maybe they have a project which has 5 welders welding these coupons. In which case, if the client covers the costs for this additional requirement, it could be acceptable. I've had this specific situation happen to me, but for duplex and super duplex steels, where the Ferrite test was deemed necessary. It's not a cost as high as performing PWHT, but it was a specific request for qualifying welders and the client covered this cost
It will boil down to how much your client insists on this issue, but you will always have to stand your ground, as its not your responsibility to cover these costs in the initial quotation
As the paragraph you quoted states, Preheat or PWHT may be omitted.
Since for performance qualification, plain carbon steel base metals can be used to qualify for many other base metals, this should seldom be an issue.
In the case where an organization has the desire to use crack sensitive materials, then preheat would be an issue and regardless of the allowance, should be applied.
the WQT does NOT require preheat/pwht in accordance with the WPS.
I agree, most times, plain carbon steel test pieces are used for general WQT. The expense and time/cost involved in providing heat treatment and consumable costs would not be feasible WHEN the standard allows an alternative. Of course, in the case of high alloy crack susceptible material tests and more stringent 'after weld' corrosion tests, then the omission of heat treatment can be overridden.
RT is often used as an alternate to guided bend testing when there is a concern the test specimens will not pass the bend test.
One must review the construction code to verify RT can be substituted for guided bend tests. B31.3 High Pressure fluid service comes to mind.
Thank you for recommended , I will a answer as Standard to Clients
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