Ground Ring And Welding What Problems?

[ed downey]

I have a project in New Mexico that we are adding on to an existing building (Steel Structure) that is tied to a ground ring around the perimeter of the existing building. Part of the use of the existing building that is being added on to is for communications, phone switch, and small data center.

My question is this when we start construction there will be a lot of welding and this steel structure is tied to the ground ring. Will we have issues with the communications equipment? If yes, Have you ever worked on a project like this and what is a good procedure for isolating the communications equipment?

Any help with this matter would be greatly appreciated.

Thanks,
Ed

 

[George Stolz]

Re: Ground Ring And Welding What Problems?

I'd say you can disconnect the building steel from the GES for the welding.

See 250.6(B)(1).

I'd consider the current from the welder to be objectionable current, you wouldn't want it travelling in your GES.

I don't really think it would, but I'm no expert.

 

[tkb]

Re: Ground Ring And Welding What Problems?

I'd say you can disconnect the building steel from the GES for the welding.

I think it would be safer with the steel bonded than removing it.

The steel cannot be isolated. It connects to grounds through conduits, plumbing, MC cable (if any).

It could cause more objectionable current all over the building without the building steel ground.

IMHO I would not disconnect it. There should not be any problems with the welding if the steel is grounded. It's done all of the time in construction of additions.

I am not an expert either. I may be wrong, but I have never heard of problems.

 

[charlie]

Re: Ground Ring And Welding What Problems?

If the welder is not grounded to the steel from the secondary side and the circuit consists of the clamp and welding rod, the current will travel from the secondary side of the welder through the welding rod to the steel and back through the other side of the welder. How can the current go elsewhere? In other words, don't lift the grounds.

 

[gpedens]

Re: Ground Ring And Welding What Problems?

Ed, we have had some rather costly problems in this area. Using welders near cables and open cabinets can cause interference and nuisance tripping. Welders can cause pitting in bearings. In critical areas we require both the welding machine ground lead and hot lead be run to spot the welding is performed. As in just inches away. Try to avoid long runs of welding cable that might be parallel to signal cables or connect to PLCs or other computer like equipment. Use care when welding near open cabinets.

 

[dereckbc]

Re: Ground Ring And Welding What Problems?

Well at MCI where I used to work, you would be shot on site with a welder, not to mention held liable for any outages incurred from it's use.

The problem isn't from current flowing on building steel, but EMP and RFI generated from the arc that radiates into the equipment and causes anything from data errors, resets, to equipment failure.

When welding was required, equipment had to be relocated and a magnetic shield installed encircling the work area.

You really need to coordinate with the company wanting the work done, or somebody is not going to have a good year.

 

[gpedens]

Re: Ground Ring And Welding What Problems?

Dereck, is a magnetic shield a metal cage? Sounds like you have experienced some of those million dollar shutdowns too. I think you mean EMI rather than EMP. They both cause the same problems but I usually see EMP associated with atomic or hydrogen bomb blasts.

 

[oceanaradio]

Re: Ground Ring And Welding What Problems?

GPedens is correct, you must ground at the work when welding, and that prevents contamination of the building ground system. It is also not the contractors responsibility to isolate sensitive equipment, it is the owner and owner's engineer.

I used to be an Ironworker, and I never heard of any shielding required for even 600 amp air-arc work in any kind of industrial, defense or commercial project. The only precautions were ground the work (not steel near it) and avoid laying welding leads or power cables over other equipment. Simple.

Isolation trasformers, fiber optics, or a combination of both protect sensitive communications equipment from transients from ground that far outweigh anything a properly (work) grounded welder could ever cause. If that protection isn't there, the equipment isn't sensitive to anything your properly operated welder could do.

Jack
USCG Oceana Radio