Stainless Steel Welding FCAW

[TANKO]

Dear all,
i'm writing to have some technical advice about a situation that we have in our site.
We are building some pipelines for liquid gas but we have a problem with some joints infact it's impossible to weld with the purging because we don't have any solutions to pull out the plugs. The alternative would be use a FCAW (flux cored arc welding) but the client does not accept this welding procedure for the slag that can remain inside the pipeline and damage the valves.
If we clean the line with air before pneumatic test, is it possible to remove this slag?does this slag remain attached to the pipe?

We are waiting for your comments above all if someone had this experience.

regards

 

[DekDee]

Tanko,
I have never heard of root runs being put in with FCAW - are you possibly meaning flux cored or flux coated GTAW ?
If so, no - you will not remove with air.
It is very, very hard to remove and that is why the client is not allowing it.

IMHO there is no such thing as "impossible" when discussing purging - just varying degrees of difficulty (and consequently cost).
You say you can't remove plugs - what about soluble dams ?
Regards,
DD

 

[racookpe1978]

What diameter pipe, and what material pipe?

I've used consumable inserts in pipes requiring "backless welds" even for stainless.
Some companies got screwed before with FCAW (wire fed) welders leaving stubs of the wire inside the pipe, but proper welding "start" procedures eliminate that risk. You can also borescope the pipe to check for wires, debris, and slag.

"Slag" per se does not happen with wire-feed welding using the proper purge gas, but the back side of un-purged stainless pipe welds often get a "sugar" or black and oxidized coating that IS rejectable if found.

 

[Duwe6]

Try the flux-coated GTAW 'tig' rods. I recently qualified a WPS using a rod from ESAB; welder hated it; "The puddle runs like MUD!". Tensiles and bends passed just fine.

NOTE: on a PQR coupon with a different root process, the coupon has to be a double-bevel, not a single-bevel. Otherwise, during the specimin prep, most [if not all] of the root's metal will be removed. Invalidates the root portion of the PQR.