GMAW for piping / pressure vessels applications

[Ariuri]

Hi guys, I've been through some welding spec for piping/pressure vessels and was curious about one requirement:
GMAW may be used for fill passes provided the transfer mode is globular or spray arc and the completed thickness is of the weld is no greater than 9.5 mm.

Does anybody know what can be the reason for that? Is it due to reliability (defect rate) of GMAW?

 

[kingnero]

Spray is the preferable transfer mode for GMAW in thicker plates.
This is a reasonable statement from the client.
I'd avoid globular transfer where possible, but it is a suitable option when welding in position.

No idea about the 9.5 mm, the only reasonable explanation I have would be that SAW should be used for thicker plates. But that's just a guess, because lots of 10 mm plates get welded using GMAW. I don't think the client should be dictating how to weld 10 mm plates to the fabricator. Again, just my $0.02.

 

[MJCronin]

Suggest that you post in the "Boiler and Pressure Vessel" forum

MJCronin
Sr. Process Engineer

 

[DVWE]

Is it due to reliability (defect rate) of GMAW?

I am going to say yes to this. More than likely, your client had a bad experience with GMAW. Either that or their specifications have carried this requirement over from years past.

GMAW is not a bad process to use for piping or pressure vessels as long as it is set-up properly, just like any other welding process.

The devil is in the details; she also wears prada.

 

The TS writer probably doesn't want short arc GMAW.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

Years ago this was standard practice, except the root pass restrictionm, for short circuiting transer gmaw.

 

[Ariuri]

Ironic metallurgist, the spec additionally says that short arc GMAW might only be used for root pass.

Weldstan, you are right. The spec is a bit old (prepared in 1995 and revised in 2005).

Thanks everyone for your inputs. Still have no idea why there is 9.5 mm (3/8'') thickness limitation.