Backing strip

[Slag in Sleeve]

If I weld say a pipe root using 6010P rods and fill & cap using FCAW(N) could the root run be deemed a backing strip? We have some non coded cement pipelines to do and also pile joints to do. I was thinking that I might be able to kill two birds with one stone with doing the cement line 6010 root and if that qualified as a backing strip then it would cover us for the FCAW(N) piling job.

Cheers

[warfab]

Hello Slag in Sleve,

I’m gonna say no on this one because the joint designs for an un-backed joint versus a backed join are much different.
In AS1554.1 the prequalified joint preps in Table E show a much larger root gap for a backed joint (4-6mm) compared to an un-backed joint (1-3mm) which is what you would have, to put in a root run with 6010 electrodes).
One of the essential variables in AS1554 is the omission of backing which would require requal.

I think that ASME IX has an allowance for a root run to be classed as backing.. but dont quote me on that one.

May I ask.. why you are worried about it when you mentioned the welds are not to a standard??

Cheers!!

[Ballbearing]

SIS,
As AS/NZS is very vague on combination of processes (in fact it is very vague on a lot of things) it is basically left to the individual to try and make a decision based on sound engineering judgement.
If we have a SMAW/FCAW open root joint it is obviously not pre-qualified and will require mechanical testing.
If it passes the mechanicals it is ready to go in production.
Now in reality the only thing the 6010 has done is provide backing material for the FCAW.
Table 4.11 (c) lists “The ommision of backing material” as an essential variable – backing material can be weld metal, permanent backing strip or temporary backing strip (ceramic etc).
If you change from 6010 root, in other words remove the SMAW process (backing with weld metal) to just FCAW (backing with backing strip) you have not contravened anything in the code and IMHO you are all good.
But, and it is a big but – this is purely my opinion and opinions are like a….holes, everyone has one. LOL !!!
That is your cue Flash !!!!!

Cheers,
BB

[dieselofdog]

I agree with you BB,

At the end of the day ‘Backing’ is anything that supports the root run.  As long as all the essential variables are maintained, I can not see a problem.

I would like to see in 1554 some guidance around qualifying multi processes in the same joint, thickness ranges of weld metal deposited by each process.  ASME IX is all over this.

I have seen two supporting PQR’s of 2 different processes combined into the one WPS to form a dual process procedure, eg A pipe PQR that was GTAW (full pen no backing) root, fill and cap and pipe PQR FCAW (with backing) fill and cap combined to form a GTAW root FCAW fill and cap WPS. Thus a saving on not having to produce another PQR and further testing.  The material, thickness and pipe OD where the same on both PQR’s.   

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