metal table assembly line help

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mike1964

Member
Location
Pennsylvania
Please help, i am an electrician for a medium size product manufacturer i am being asked to go to our Puerto Rico facility and investigate a problem. every once in a while (1or2 times a day) one of the workers who are sitting on metal chairs and working on a metal table assembly line with a movable belt that carries product down the line to be worked on in steps gets shocked. From what i understand its a half decent wack. What i plan to do is bond together all the metal parts of the assembly line with 4# wire back to the sub panel, inspect all circuits connected to the assembly line and check that the sub panel that feeds the line is grounded/wired correctly. If you all have any other ideas please share them with me. I leave sunday morning!!!

thanks
mike


p.s i have pictures of the panel that feeds this assembly line, but don't know how to add them to the post. It is a HORRIBLE MESS.
 
roger

roger

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Staff member
Location
Fl
Occupation
Retired Electrician
Re: metal table assembly line help

Mike, E-Mail your pictures to bill@electrical-contractor.net and ask him to post them for you.

It sounds like possible static build ups which may take some inginuity to resolve. (note I said "sounds like" which could be way off)

Roger
 
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bennie

Esteemed Member
Re: metal table assembly line help

Mike: Will you have internet access when you get to the jobsite?
 
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bennie

Esteemed Member
Re: metal table assembly line help

That's good Mike. You have tools that were not available a few years ago.

Make an analysis of the event and write the details. Also get some jumper test cables with alligator clips. Radio Shack has them.

I am with Roger, this sounds like static charge.

Find out what kind of clothes the workers are wearing.

Good luck.

Bennie
 
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bill addiss

Senior Member
Re: metal table assembly line help

Mike, Here's your Pictures:

Panel.jpg


Panel-1.jpg


Panel-2.jpg


Panel-3.jpg
 
roger

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: metal table assembly line help

Bennie, I may be a little warped, but I didn't think Pinto's were ugly. :D

Roger
 
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mike1964

Member
Location
Pennsylvania
Re: metal table assembly line help

bennie,roger, by the way my bosses who know nothing of the nec have instructed me to ground the s*it out of the assey.line. Do you see a problem if i bond all metal parts of the line together and take it back to the main distribution equipment and hook up with the concrete incased grounding electrical that i have heard exists, it would be ran as a single conducter, how about in sch.40
 
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bennie

Esteemed Member
Re: metal table assembly line help

Mike: Find out where the two points of contact are on the machine, and worker, when getting zapped.

You can check for proper equipment ground, probably at the drive motor.

Find out what kind of material is in the conveyor belt.
 
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mike1964

Member
Location
Pennsylvania
Re: metal table assembly line help

Bennie

I have been assured by the engineers that it is not a static problem, we have been making our assembly lines "static safe" for years so i would like to believe we do it correctly, although i have never been involved in that process and really don't know how its done...Any thoughts?

thanks
mike
 
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bennie

Esteemed Member
Re: metal table assembly line help

Mike: If this event is a repetitious zap, it is static. If it shocks all time, it is a operating voltage fault. That is all I can come up with.

Others may have a solution.
 
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bennie

Esteemed Member
Re: metal table assembly line help

Mike: If those panels are an example of engineering credibility, you have a static problem.
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Re: metal table assembly line help

Mike1964
From the photo's I think I see that the neutral connection has been hot?
If the sub-panel has been bonded to the neutral and the conduit connection is lost and the neutral is lost there will be an unbalanced voltage on everything that is bonded to the grounding and to earth or in this case the floors. It looks like there is no bonding bushing installed on the feeders REMC to prevent the loss of connection to the panel case.

the first thing I would do is to see if the neutral bars are in fact bonded to the panel case.
Investagate the neutral connection to the neutral buss to make sure that it is intact and has a good connection.
Make sure that the neutral and grounding is kept seperate from the grounding after the service disconect this means that there should be a sepreate path for the ground fault and neutral current back to the main disconect. this will pervent a neutral loss from showing up as voltage on the EGC's
Also there is a large green ground wire on the neutral buss on the left. that shouldn't be there.

[ July 19, 2003, 05:28 PM: Message edited by: hurk27 ]
 
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mike1964

Member
Location
Pennsylvania
Re: metal table assembly line help

bennie

i hear what your saying, i want to make sure that everybody understands that i had nothing to do with the panel wiring. This panel is 1600 miles away from were i work. :)
 
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mike1964

Member
Location
Pennsylvania
Re: metal table assembly line help

hurk27

Good eye, i all ready tried to tell them to perform the tasks you speak of over the phone...it didn't work. as a matter of fact the "electricians" they called in drove a ground rod and connected it to the neutral!!! When i explained to the engineer that what he did a 1st year votec.student wouldn't even think of doing he got spooked and bought me plane tickets.

thanks
mike
 
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bennie

Esteemed Member
Re: metal table assembly line help

Mike: The static charge can be in the workers body, and discharging when touching a grounded object.

I had the same complaint as you, one time years ago. The assembly line was a venetian blind manufacturer.

The problem was, the ladies on the line who wore nylon underclothes got zapped often, the ladies with cotton, or no pants, were spared.

The metal chair is the clue.

[ July 19, 2003, 06:22 PM: Message edited by: bennie ]
 
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