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JOB 02-25-2013 08:42:05 50.124.208.41 Report to Moderator	Grounding question for an electrician. Below is posted a couple of welding incidents, situations or maybe mild accidents. I read an article in the newspaper maybe 30 years ago of a farmer and son working on a manure spreader. Son was welding and father working. I have assumed the welder was an AC buzz box because that was what most farmers had back then. The news paper article did not say what the welder was. There are a lot of electrically smart people on here so I will tell what I read to the best of my memory. The welder was grounded to the rusty tongue of the manure spreader The son was welding somewhere on the spreader. Don't know if he was standing on the ground (dirt) or on the spreader itself. The father was laying on the ground working on the bottom of the spreader. This was a really hot and humid day like when you can't even walk outside without sweating. While the son was welding the father was electrocuted. The newspaper article said the father made a better ground than the grounding clamp. Any electricians want to comment on this? This is just what I read in the newspaper second hand to the best of my memory. [Reply]   [No Email]
John T 02-25-2013 13:55:04 71.52.99.130 Report to Moderator	Re: Ground for a welder in reply to JOB, 02-25-2013 08:42:05   Good post, I will try to explain it for you in simple terms so as to NOT loose you, here goes. If its an AC Buzz Box Welder its an isolation transformer and if theres no leaks or shorts the ONLY voltage difference is between the leads, stinger and the groung clamp, none with respect to mother earth or the concrete floor or structural building steel from either lead. Thats notwithstanding inductive and capacitance which can create some other potentials but those are low energy. Soooooooooo if one part of a farmers body is in contact with say the stinger or metal its in contact with and another part of the body is in contact with the ground clamp or metal or water or earth etc its in contact with THAT VOLTAGE CAN CAUSE A CURRENT FLOW and it only takes maybe 30 TO 50 milliamps across the ticker to cause it to de fibrillate and YOU DIE. If you put one hand on the stinger and another on the ground clamp theres a voltage difference and current can flow.......Same if youre lying on the wet ground or up againstg a metal farm implement etc that either the stinger or ground are contacting you can get shocked Got it??????? John T [Reply]  [No Email]
JOB 02-25-2013 16:27:38 74.36.134.85 Report to Moderator	Re: Ground for a welder in reply to John T, 02-25-2013 13:55:04   Not entirely, I do not understand the weird things electricity can do. I had heard that it only takes a couple of milliamps across the ticker to put you into that eternal sleep. The post above this one from David G, his dog put his wet nose to a trailer that was being welded on, and it sounds like he got bit by something. Aboard ship when in an engine room and welding I would get a tingle when putting an electrode in the stinger if I was not wearing a dry glove and standing on a wet deck. [Reply]  [No Email]
John T 02-25-2013 17:38:31 71.52.99.130 Report to Moderator	Re: Ground for a welder in reply to JOB, 02-25-2013 16:27:38   A GFCI is designed to trip around 5 milliamps and this is for an approximate safety factor of ten times. Typical figures Ive seen for defibrilation are 30 to 50 milliamps. Again the voltage output of a buzz box AC transformer welder is between/across its leads (stinger and ground NOT either lead to other AC wiring) but one or both of those leads are against metal or on concrete or wet mother earth and if your body gets between one or the other (or water or metal etc) you get shocked.. Electricity doesnt necessarily do weird things (from an engineers perspective), current simply tries to flow anytime theres a voltage difference and ohms law defines how much in whatever paths are available subject to the paths resistance. Hang in there, youre comin around John T [Reply]  [No Email]
smallercrawler 02-25-2013 11:38:39 166.82.254.181 Report to Moderator	Re: Ground for a welder in reply to JOB, 02-25-2013 08:42:05   Early 70's, company decided to eliminate 4 overhead bridge crane operator jobs on a 2 bay/2 cranes per 600' bay installation. Bought a then "state of the art" AB digital processor/control system for ~$400k (analgous to elevator call/que scheme). Vendor took 3 months to install/debug system. Worked great until shutdown when another vendor was employed to do some mods. on the crane rails/supports. Poor welder grounding apparently fried the system; the electronics vendor was not responsible, welders went out of business. Company had to eat it. Just an example of what improper grounding can do. [Reply]  [No Email]
JOB 02-25-2013 13:39:43 74.36.130.21 Report to Moderator	Re: Ground for a welder in reply to smallercrawler, 02-25-2013 11:38:39   That weldor could have done something similar to what I described down below on a reply to puddles. You need to ground and ground good as close to where you are welding as possible. There are some exceptions to grounding close. [Reply]  [No Email]