Welding on an ESD (conductive) Floor

By Glenn J Date 06-10-2010 19:36

We have purchased a TIG welding lathe w/ wire-feeder, and will be welding a metal piece to the metal portion of an electro-mechanical assembly. The assembly’s electronics are static sensitive, and we are thus planning on installing a conductive epoxy floor in the facility. It is a unique combination. Normally you would not weld in an electronics assembly environment, or vice-versa. My concern is that the conductive floor may pose a safety problem, especially since it will be connected to earth ground. Of course the welding machine’s chassis will be tied to a ground (likely to the service panel, or possible a separate earth ground) though the wall socket, but do you think this poses a safety problem for the operator? The operator will be wearing electrically conductive footwear, effectively grounding him to earth ground all the time. Do you think this poses an increased risk for shocking the operator?

Any advice is appreciated!

Glenn

By Superflux (****)

Date 06-10-2010 21:05

"The operator will be wearing electrically conductive footwear, effectively grounding him to earth ground all the time"

1) Non conductive floor mats for the operator?
2) Composite toed foot wear.
3) Extreme forethought into selctive grounding for all electronic components...ie. independent grounds AT POINT OF SOURCE!

By rlitman (***)

Date 06-11-2010 20:41

ESD ground is NOT a direct connection to ground. It is typically over 100K ohm, and should actually be around 1M ohm for safety sake.
Concrete floors are conductive to some extent on their own right, and the ESD coating doesn't really change that too much. That finish is just applied to have a more consistently conductive surface and to avoid the dust issues of untreated concrete, and a non ESD epoxy coated concrete floor IS non-conductive.

Anyway, the real concern is the welding. If you use HF in your TIG process, that is basically the static jolt from hell. Seriously, forget about HF anywhere NEAR static sensitive equipment. You don't need to see an actual HF spark contact something for it to do damage, and HF actually has the power to jump through your cable's insulation.