welding procedure qualification

[sw007]

I am reviewing vendor's welding procedures on a Vessel, which requires impact test.

The welding process is SAW. The vendor provided two PQR(s) to support one WPS. Impact test is required. ASME IX is used for the qualification.

PQR-1:
Test coupon thickness: 8 mm
Maximum Interpass temperature 311F;
Maximum Heat input: 68000 J/in

PQR-2:
Test coupon thickness: 19mm
Maximum Interpass temperature: 383F;
Maximum Heat input: 57000 J/in

WPS:
Qualified thickness range: 8-38mm.

My quesions:
(1) Which one is the qualified Maximum interpass temperature: 411F or 483F ?

(2) Which one is the qualified Maximum Heat imput: 57000 or 68000 J/in ?

Please advise. Thicks.

 

[metengr]

Based on ASME Section IX, the WPS essential and supplementary essential variables would be based on;

1) the highest interpass temperature because one could always decease interpass temperature (see QW-406.3, which would not adversely affect impact requirements. Higher interpass temperature means more heat input and grain growth.


2). Use the maximum heat input value on the WPS because if you increase the heat input, the WPS must be re-qualified (see QW-409) for the same reason as in 1).

 

[sw007]

metengr,
Thanks for you comments.

(1) The Maximum Interpass could be 483F(383F + 100F), using PQR-2
(2) The Maximum Heat input could be 68000J/in, using PQR-1.

Am I right?

My concern:
The qualified thickness is only 8-16mm by PQR-1. If the plate thickness used in the fabrication is 24 mm, which is qualified by PQR-2. The maximum heat input of 68000J/in is qualifed by PQR-1. How can I deal with this case? Do you know what I mean? Thanks.

 

[metengr]

(1) The Maximum Interpass could be 483F(383F + 100F), using PQR-2

Correct, by Section IX guidelines.

(2) The Maximum Heat input could be 68000J/in, using PQR-1.

Correct, by Section IX guidelines.

You need to envelope the interpass and heat input, which you have done by the above. I don't see that this is a problem. You can always run a leaner heat input for the thicker production material. You can have the vendor follow the lower heat input requirement because you are not penalized for decreasing heat input.

 

[sw007]

Thanks again.

 

[weldtek]

My thinking would be that the max allowable interpass temp. would be that recorded on the impact tested PQR. In this case 411 F.

 

[stanweld]

Max heat input and interpass temp is based on the PQR and the thickness range qualified. The qualification range on 8 mm thick material for impact requirements is 8 mm to 16 mm. The qualification on 19 mm material qualifies the procedure from 16 mm to 38 mm. Therefore, the max heat input and interpass temp values recorded during qualificatio of the 8 mm coupon apply to the thickness range from 8 mm to 16 mm and the heat input and interpass temp recorded during qualification of the 19 mm coupon applies to the thickness range from 16 mm to 38 mm.

 

[weldtek]

I would agree if, and only if, both PQR's were impact tested. In this case I assumed the fabricator only impact tested the thinner plate. Maybe that assumption isn't correct but, why would a fabricator perform impacts on both plates when he carried a higher heat input on the thinner plate. 68 KJ on the 8 mm and only 57 KJ on the 19 mm. I'm not saying he couldn't impact test both plates but, it doesn't makwe a lot os sense to do so.

 

[stanweld]

If they need to weld materials from 8 mm to 38 mm that are subject to impact test qualification, at least two PQRs are required; one qualified on 8mm plate and one on 19 mm or thicker plate.

 

[weldtek]

Right, but only the thinner plate requires impacts. The thicker plate can be tested with bends and tensiles only and those two PQR's provide coverage thru the full range of 8 mm to 38 mm, with impacts.

 

[stanweld]

It was stated that the production material is 24 mm thick and it is assumed that the production material required impact testing and was subject to impact test qualification; therefor, the qualification on the 8 mm sample is moot - only the qualification on the 19 mm plate and the attendent essential supplementary essential variables recorded thereon are germane to meeting ASME Code impact requirements for the production work. The statements by metengr apply, except that I believe the max heat input is limited to that in PQR 2 or 57 kJ/in.

 

[weldtek]

Stanweld,

My point is simply this, in the example above, impact tests are NOT required on the thicker test plate. As I stated in my previous post, per ASME Sec IX, an impact tested only, ( ie no bends and tensiles,)weld coupon on 8 mm plate, combined with a weld test plate on 19 mm tested for bends and tensiles only ( ie no impacts), will support a WPS with impacts, 8 mm thru 38 mm. Of course, max heat input recorded for the impact tested plate governs.
Now, if in fact, both the 8 mm plate and the 19 mm plate were impact tested, the SE variables from the 8 mm plate would govern for thicknesses below 19 mm. Above 19 mm either set of SE variables could be used. Evidently the Sec IX Subcommittee recognizes that when using the same heat input and welding within the range of other variables, thicker base metals typically experience less degradation of notch toughness.