Bonding Metal Scaffolding to The Work Piece Being Welded

T

TVH

Senior Member
The attached Welding Safety Bulletin from our friends Down-Under highlights a concern that person in construction may not be aware of. During heavy construction projects I have personally been shocked (tingling to jolts) during scaffold inspections where multiple Arc Welding was taking place on the metal scaffold (tube and coupler and framed scaffolds). Other crafts were working on the same scaffolding and have occassionally complainted of nuisance shock events. Investigation into these events revealed poor welding practices by welders which involved improper work piece connections, stray current from adjaced welding, broken electrode holders, worn/damaged cable, accidental stinger contact with metal. Such practices were corrected on the short term but welding protocols are often repeated during the rigors of construction especially on "hard-money" projects.

The bulletin below gives caution on use of a bonding straps where the strap is properly connected to the metal scaffold and to the structure being welded. I have not seen this in practice on the many projects I have been assigned.

I have attempte to address this subject with welding machine manufactures/welding organizations with no or little clarity on validity or specifics.

Question to Electrical Professionals:
Are bonding precautions, detailed in the bulletin, a required safety precaution againt electrical incidents to those working/occupying the scaffold? If so where is the precaution clearly specified in industry standards? I have searched many standards but clear and specific precautions on this subject are not detailed. OSHA has, however, specified bonding straps when welding from wire rope suspened scaffolding along with other precautions to prevent stray current from passing through the wire rope.
Comments from electrical professionas will be appreciated.
 

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The problem I see with this is that the pins and stuff (structural connections) on scaffolding aren't exactly reliable low impedance electrical connections.

It used to be common practice in fabrication shops to connect one output lead of the welder to the building's structural steel and just using a short jumper from the building's steel to the work eliminating a one run of welding cable. But there were instances of high impedance structural connections leading to I2R heating of things like plumbing, or EGCs causing fires, Also there were reports of differences in potential causing shocks.
 
My welding is connected to the building. I have a couple jumpers and benches very carefully crafted to eleminate other pathways for welding current. Its kind of a long story but have worked in welding here this type thing is a concern, big fab shops etc.
But there is ANSI I believe that goes in to more detail about connections between welders and structures, where and when to bond etc. I looked for it again,,, I want to mark it when I find it.
 
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Sberry: Your followup on this subect is very much appreciated.
TVH

Sberry said:
My welding is connected to the building. I have a couple jumpers and benches very carefully crafted to eleminate other pathways for welding current. Its kind of a long story but have worked in welding here this type thing is a concern, big fab shops etc.
But there is ANSI I believe that goes in to more detail about connections between welders and structures, where and when to bond etc. I looked for it again,,, I want to mark it when I find it.
Click to expand...
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Thank you. I dont know much but its something that has been a concern. I have seen a lot of conclusions about some of the connections,,, looking back more than currently can see some of what and why. As a payback to some early forum guys have hooked up and insured hundreds of grounds.
Worked in a couple of shops that we considered this and have seen a couple forum posts and a couple events.
 
They refer to it in the standard,,, somehow I believe it is ansi and maybe OSHA or prolly mining,,, ???? So it refers in those docs to operator awaremess,,, ha but early on had 2 benches connected by a 3 wire circuit and forget to move the work lead. I catch this and bolt a chunk of service wire across it. Even take advantage of it.
 
There was a problem thawing water service on city mains and started some fires.
There are several possible events, some particulars, cant even pretend I know them all or even read them all.
 
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