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In this article we shall discuss the various aspects of a WPS for carrying out weld repair and build up on a component, in accordance with ASME Section IX.
QW 202.3 of Article 2 of Section IX addresses the use of WPSs qualified on groove welds for repairs in welded joints, and for build up on base metals for the purpose of restoration of thickness. It basically says that WPSs qualified on groove welds can be used for weld repairs to groove and fillet welds and for weld build-ups with the following provisions:
- There is no limitation on the thickness of base metal or deposited weld metal for fillet welds.
Now, when a WPS qualified on a groove weld has to be used on fillet welds, it can be used for ALL base metal thicknesses and ALL fillet sizes regardless of this provision in QW 202.3. This has been already permitted in QW 451.4. It is not clear why the authors needed to specify this here.
It would have sufficed if they had merely said: “WPS qualified on groove welds can be also used for repairing fillet welds.”
- For weld repairs and build ups in other than fillet welds, the base metal thickness and weld metal thickness shall be in accordance with QW 451, except there need be no upper limit on maximum qualified thickness of base metal if the qualification was done on a base metal having a thickness of 38 mm or more.
This is pretty self explanatory, and needs no further description. Let us see in what cases the exemption given in ‘b’ might be of use.
Thickness of Procedure Qualification Coupon For Repairs & Buildups
If you have a qualified procedure which was qualified with a 38 mm thick test coupon, it would qualify base metal thicknesses in the range 5 mm to 200 mm. You would not need the exemption granted in QW 202.3 if your production joint thickness fell in this range.
If you have a production joint with T>200 mm that you need to freshly weld (and not just repair), you would be anyway having a procedure qualification that supports this thickness. Repair too to such a joint can be made using the existing WPS. So when would the exemption of QW 202.3 be useful?
Well, i can think of only one circumstance. When you are required to only perform the weld repair work (the original joint was made elsewhere by some other organization) on parts with T>200 mm, then the exemption given in QW 202.3 is decidedly useful. Besides this, it is also useful when you need to do build-ups on parts with T > 200 mm.
Now, let us examine some other aspects of when we use a WPS for making repair welds.
Representation of Weld Repair Groove On WPS
When we use a WPS qualified on groove welds for repair to a groove weld, which was already welded with the same WPS, does the WPS need to be revised to have the figure show the weld repair cavity?
Why should this question arise in the first place? This is because QW 402.1 is a variable as per QW 250, and therefore has to be indicated (correctly) on the WPS. QW 402.1 says that a change in the type of groove (V groove, single bevel etc.) is a non essential variable.
All variables identified in QW 250, whether essential or non-essential, must be addressed on the WPS. Although it is a non-essential variable, the actual groove of the weld which is going to be made with a WPS, has to be correctly represented on the WPS.
The groove design at the time of making the original joint may have been of one type (say V groove). The cavity developed in preparation of groove for repair in the joint might look like a ‘U’ groove. This may prompt the welding engineer to think, is the WPS required to be revised to show the repair cavity thus developed, to serve QW 402.1?
Also, sometimes, overzealous inspectors want everything to be perfect, and would insist on revision of the WPS to indicate the exact image of repair groove.
So, what does Section IX intend regarding this? Does it require revision of the WPS?
This question has been asked to ASME a couple of times, in Interpretations IX-10-15 and IX-79-72. The committee replied in the negative, meaning that revision of the WPS is not required.
The reply further stated that – “The intent of QW 402.1 is to include or reference in the WPS the groove design employed in preparing the base materials for joining into a weldment. Repairs are considered a part of the welding operations.” This settles the matter for good.
Now, this was about when the WPS used for making the repair is the same one used for making the original weld. Can we use a WPS indicating a certain groove design to make repairs in a completed weld that had a different groove design (but the weld is completed now; that is, already welded with another suitable WPS)?
No. I believe that would be a misrepresentation. This kind of a question has not yet been asked in an Interpretation, so there are no references to cite. Although it seems a trivial matter seeing that doing so would not violate any essential variable, in my opinion it would be appropriate to use a WPS showing correct groove shape. QW 402.1 may be a non-essential variable, it does not mean an incorrect representation would do.
Now, similar to this line of thinking – consider this. Can a WPS showing a groove weld be used to weld a fillet joint, without revising the WPS to show fillet in the figure?
Using WPS Showing A Groove For Fillet Welding
A procedure qualified on a groove weld is good enough to weld any fillet size on a base metal of any thickness and diameter as per QW 451.4, so a groove weld WPS is good enough to weld on a fillet weld.
However, can a WPS showing a groove weld be used to weld a fillet joint, without revising the WPS to show fillet in the figure?
The matter of whether the same WPS can be used to weld on a fillet joint is a pertinent one, because, although it does not violate any essential variable, this problem is commonplace, and occurs frequently.
Such a question has been officially asked to ASME as well, who have replied to it through an Interpretation. The Interpretation number is IX-78-10 (qs 2).
The reply said that the WPS showing the sketch of a groove weld need not be revised to show a fillet weld when this WPS is used to make a fillet weld. The wording used stated that “The variable QW 402.1 refers to a change in groove weld joint design and therefore does not apply to fillet welds.”
The reply is undoubtedly true to the wording of QW 402.1. QW 402.1 only talks about groove, not fillet. However, the reply is a bit of disappointment to purists, including this author. Using a WPS showing a groove joint for a fillet joint is clearly a misrepresentation.
This Interpretation was issued in 1978, one hopes that the committee would have revised its understanding of the matter. Perhaps the QW 402.1 should be amended as “A change in the type of groove (Vee-groove, U-groove, single-bevel, double-bevel, etc), or a change from groove to fillet or fillet to groove. Correct joint configuration shall be represented on the production WPS.”
There is another interesting question that comes to mind, regarding the matter of repairs.
Weld Repair With A Different Process
Suppose that a PQR has been qualified using a combination of GTAW (at the root) and SMAW in the test coupon. Using this PQR, a joint has been welded with GTAW (at the root) and SMAW. Is it permissible to carry out repairs in the SMAW welded portion of the joint using GTAW process?
Consider another version of this. There exist two different PQRs, having all essential and non-essential variables as identical to each other, except that one PQR has been welded with GTAW, and another with SMAW. Is it permissible to carry out repairs with GTAW, in a joint welded with SMAW, in the context of these two PQRs? Or, vice-versa?
Let us reword the question one more time. Is it permissible to carry out repair in an already welded joint, with a process different from the original process used for welding the joint? Assume that the chemical composition of the weld deposited by both the processes is same.
This question has not been addressed in Section IX. So, one has to take refuge of the Interpretations database, to understand the Committee’s intent regarding this. A recent Interpretation, IX-17-29, asked such a question, as described above. The question is reproduced below:
“Background: A joint is welded using a WPS qualified with the GTAW (with the addition of filler metal) and SMAW processes.
Question: Is it permissible to use the GTAW process, with the addition of filler metal and not exceeding the maximum qualified deposited thickness, to make repairs to the SMAW deposit?”
The reply given in the Interpretation is a ‘yes’. This establishes that such repairs are allowed.
So this was all about how to reckon a WPS for doing repairs and build ups, in compliance with ASME Section IX. Do leave your thoughts in the comments section below.