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Up Topic Welding Industry / General Welding Discussion / Strictly for conversation.
- - By Lawrence (*****) Date 05-31-2016 16:14
So I saw this picture on the internets.

GTAW with two filler rods on the cap pass.   I've seen this before but was curious if there were actual restrictions to this technique?

I understand that an increase in filler metal diameter may be an essential variable such as in D1.1 Table 4.5, and that the increase in current to accommodate the extra filler might exceed established WPS current values as well.

But could a procedure be qualified in such a way that two filler rods were used for a cap pass?  

I can think of many reasons why this might not be a great idea... But am also just curious about the technique and if there are actual code restrictions to the technique in ASME, API or some other specification.

Thoughts ?
Parent - - By js55 (*****) Date 05-31-2016 16:48
Lawrence,
Other than perhaps a procedural compliance issue there is in essence absolutely nothing wrong with the technique.
Parent - - By js55 (*****) Date 05-31-2016 16:54
And in answer to your question about Code restrictions, no, there are no restrictions.
Parent - - By Lawrence (*****) Date 05-31-2016 17:42
Is it something you have seen commonly in the work you oversee?

Thanks for the reply :)
Parent - By js55 (*****) Date 05-31-2016 18:04
Back when I was welding it was not uncommon. Simply another technique in the quiver for specific situations (like the bent tungsten trick, or feeding rod from the backside of open butt grooves). Now, with much more background in metallurgical and mechanical issues I can see nothing wrong with it.
Parent - - By qcrobert (***) Date 05-31-2016 18:21
Phillips 66 Modernization Project, Borger, TX, in 1979 I busted RT for SI on a 2" heavy wall, carbon steel pipe using this technique.  I began 2-wiring to soon as a quick way to fill pass.

This technique was not allowed by Daniels QA/QC at the time.  Only one out of 63 tubes that were 100% RT that failed.
Robert
Parent - By js55 (*****) Date 05-31-2016 20:13
Robert,
I would venture to comment that the increased speed/productivity from this technique does not come from the additional wire but from not having to stop and reload your hand.
It can also prevent having to roll the wire with the electrode when making wide weaves for caps.
Parent - By Blaster (***) Date 05-31-2016 21:45
I like the technique if the torch will take enough amperage and conditions will allow its successful use. This happened the last time a guy tried it on a test:

Parent - By PlasmaHead2 (***) Date 06-01-2016 05:02 Edited 06-01-2016 05:04
I saw one on the book of faces that was a Massive weave(4x wire dia. with 4 1/8" wires...) on a ~1/4" thick ~4"wide aluminium plate. They cut and etched it showing that it had penetration and no gaping porosity. Kind of a pretty weave pattern too... you could almost see how long the welder sat in one area...
It was all around pretty cool looking, but the claims that it was a strong weld (knowing the little I do about heat input and aluminium thanks to this forum) made me twitch a little...
End of the day, I realized I hang around you guys too much to get along with the "weld porn" crowd... :twisted::lol:
Ill try and find the pics... they seem to be lost to facebook, and I appearently didnt save them...:sad:
-Clif
Parent - By pipewelder_1999 (****) Date 06-01-2016 13:55
As indicated before, there is no code restriction on piping. However the size of filler metal in conjunction with the electrode travel angle can greatly affect penetration/fusion. I recently tested 45 welds on the  2.75 OD x .625" Super coupon. The contractor wanted GTAW all the way out. The fail rate for bends was 22%. All failures were related to non-fusion between layers. The defects were not visible prior to bends and would NOT have been seen by radiography.

In more than a couple of cases the welders were heard to say things such as I shouldn't have doubled the wire, should have used the 1/8" instead of the 5/32" etc...

If you need to double the wire, maybe its time to reach into the toolbox for a tool with a better deposition rate. The pass rate for the SMAW welds on the same type coupons was 100% (Except for those that were looked out).

Gerald
Parent - By 46.00 (****) Date 06-04-2016 20:10
I have seen many photos posted on LinkedIn that show the same. I must admit I have done the same in site situations when needs must.
I would not 'like' to see it done on a job I was looking after now but that would make me a little hypocritical I suppose. As I have never found a clause in any piping spec that prohibited this practise, you could argue it's wrong thru many reasons. I guess I would just have to voice my disapproval.
You can have procedures with more than one filler wire. I remember one years ago that had 24 filler wires on a consumable guide procedure
- By 803056 (*****) Date 06-04-2016 21:51
I take the position you can use it if you can demonstrate it will produce acceptable results, i.e., qualify the WPS. If the WPS is qualified and if it lists dual filler rods, then go for it.

Al
Up Topic Welding Industry / General Welding Discussion / Strictly for conversation.

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