[Bencrossland]

Hi I am a fabricator/sheet metal engineer from the UK I have been in this business for five years. I have studied fabrication and welding at college for four years as an apprentice and have good experiance in mig, tig and stick welding and in all that time even when learning to stick weld I have never heard of backing straps until watching the welding tips and tricks videos. I was wondering if any one could explain the purpose of them to me? It is probably something simple and I will feel like an idiot when it is explained to me because I can't get my head around it I thought that penetration was needed on the back side for reinforcement.

[Shield Arc]

Think of backing straps as a crutch. Not everybody can weld open root.

[plain ol Bill]

Backing straps are to insure 100% penetration really.

[gnabgib]

Think of backing straps as a crutch. Not everybody can weld open root.

No problem with penetration to see there!.. And how would you do backing straps on a length of pipework anyway?

[gnabgib]

Backing straps are to insure 100% penetration really.

Whatever happened to thorough testing without aids?


















/

[MinnesotaDave]

Backing straps are to insure 100% penetration really.

And they are fast to weld too - in my opinion.

[MinnesotaDave]

No problem with penetration to see there!.. And how would you do backing straps on a length of pipework anyway?

(snip)

Whatever happened to thorough testing without aids?

Pipe can have backing rings, and when splicing tubes (like on motorcycle frames and small airplanes) it's not uncommon to put a sleeve inside and widen the gap so all three can be welded together.

Backing straps are common in structural work I'm told.

Ceramic backing straps are common in structural work also I'm told - they are pretty interesting.

[gnabgib]

Pipe can have backing rings, and when splicing tubes (like on motorcycle frames and small airplanes) it's not uncommon to put a sleeve inside and widen the gap so all three can be welded together.

Backing straps are common in structural work I'm told.

Ceramic backing straps are common in structural work also I'm told - they are pretty interesting.

[/quote]

Point taken. I do know about "backing rings" in my part of the world, but was thinking too literally when replying about backing 'straps'.

[Otto Nobedder]

One application I was in that used backing straps was the manufacture of new rail cars. These were flat cars, of a new (at the time) design with the highest rated capacity. The central box-beam had to be welded to the "long-neck", which rose/tapered to the bed height to connect the car's couplers. This box structure required flawless roots, as rework was prohibitive in cost, so the top and bottom flanges used permanent backing bars. This allowed very high amperage spray-transfer welds for the root passes, and I don't recall a single root failure for the time I was there. There was also a production speed benefit, as we could use 3/32" flux-core (dual-shield) wire and lay in the root as quickly as any fill or cap pass.

I've also used backing rings in aluminum pipe for ASME welds. These were machine-fitted (the pipe was back-tapered to a matching taper on the backing rings to keep the ID constant) and welded beautifully.

I've more recently used backing straps on high-vacuum repairs where there is no access to the back side, but a huge gap to fill, in the correction of stress-corrosion cracking in stainless steel. I'm able to eliminate sugaring by opening an oblong slot, inserting a narrow backing strip and turning it 90* to close the opening so I can properly back-purge the area (nitrogen. The volumes are too large to use argon economically).

Everything we do as welders has it's place and purpose. The trick is selecting the right procedures for that place and purpose.

Steve S

[Shield Arc]

And how would you do backing straps on a length of pipework anyway?

We always called them chil rings.

[Boomer63]

Thank you Dave J and Steve for two great replies! You beat me to the punch with those comments! I would add that I have run into backers extensively in structural welding; sometimes working with ceramic backers on moment connections, which will then be removed, ground and welded from the other side (just one example, I can offer many more). I think to just dismiss backers as something used by those who can't weld open root is an understanding that a welder of limited skills would have. Fortunately, we have enough cats on this forum with very diverse backgrounds to set that record straight.

Gary S