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Hi,
In Table 4.11(A) (Essential Variables for welding procedure) (i) states that a change of more than plus or minus 25% in specified number of runs requires re-qualification. Except if the cross sectional area is increased then you can increase the number of runs in proportion to the increased area.
If i qualify welders with a WPS on 10mm plate with 5 runs in 2G does this mean the welders are not qualified to the thickness range on the WPS (.5 to 2) x thickness 5mm plate could not possibly be welded with 4 runs.
Im thinking that ill have to also qualify the welders to a procedure with 6mm plate with 2 runs. Just seems strange that the specified number of runs cant be decreased in proportion to a reduction in cross sectional area.Has anyone else come across this problem is there any other way around this?
Andrew,
Clause 4.11a is for procedure qualifications only.
Clause 4.12 is for qualification of welders, which is positional based only.The thickness limits apply only to procedures, not to the welders.
Is not the WPS developed from the WPQ based on the limits of the essential variables of clause 4.11 in which the welders need to be qualified within that range. So that if the welder qualifying to that Procedure steps outside of any of these variables ie Table 4.11(A) plus or minus 25% specified number of runs has to re-qualify the procedure or stay within the essential variables of the first procedure.
What im trying to say is that if plus or minus 25% runs is an essential variable then the procedure is no good for the thickness limits for but welds .5 to 2 x thickness because the procedure is limited to the number of runs i can use when welding thinner plate.
Andrew
Hi Andrew,
You are correct that the WPS is developed from the PQR, however Table 4.11 is for that only – not welder qualifications.
For welder qualifications, see clause 4.12.2.3. A welder is deemed qualified as long as they are welding to a specified weld procedure, within their positions qualified, and using the process originally qualified.
I don’t agree with the number of runs essential variable, as it is contradictory to the thickness limits qualified.
For example – 8mm plate welded both sides, 2 runs per side. The WPS is qualified for 4mm to 16mm.
25% = 1 run. It would therefore be impossible to weld 16mm plate both sides in 5 passes.The way a lot of contractors around this, is to include a statement in the procedure along the lines of “it is recognised that the number of runs may vary with a change in material thickness”.
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