Morning All , Thank god its Friday !! I have a question that has been bothering me ever since it was raised yesterday for myself. It was reported to me that unsafe welding practices were being performed in our yard . A welding activity using electric arc welding equipment with a 440 volt cable in outside conditions. this does not sit right with me but i have no concrete evidence to say other wise , can any of you guys help me out with this ? Be great to get some feed back

This is not an unusual situation but as JB has already noted its horses for courses

Evening Mike, Our site is ship build & repair. Welding is our business. Best practice; cable hangers above head height or dog guards if they have to lie on the ground. RCD at the supply, armoured flex, which also improves longevity of equipment. Weld sets more often than not have an integral fan cooling unit therefore the IP rating is quite low. I would recommend (if your site allows and if you perform this task frequently) a make shift shelter that can keep the operative dry (they are at risk of electrocution if they are in standing water, wet gauntlets, overalls or closer to the job than the feed return). A designated shelter also allows you to segregate adjacent hazardous activities / painting / flammable substances, maintain product quality and even incorporate an LEV etc. If open flame (oxy/acet/prop) burning is also taking place being aware that the dross / spatter can spall concrete with a severe and almost explosive force. And for Jane, I agree a regime of test and inspect to ensure equipment is serviceable and fit for form & function additionally a nice to know; underwater welding is one of the only workplace tasks that require dental check ups by way of health surveillance as the eclectic current has the ability to destroy amalgam. Hope this is of help. Regards Alex

The use of steel-wire-armoured 3-phase cable for extending the mains power across workshops, or outside, is common. I´ve seen two or more of these used to extend power many metres across building sites and works yards. Their use within workshops is also common (unfixed and mobile). I can personally attest to the kick you get from a welding set in the wet, even an 80 OCV set. Painful. even from the workpiece to ground is tingle-inducing if the work grounding lead is not earthed.

Can I reiterate that the welding set should have a letter S on the rating plate. This tells you that it is suitable for a conductive environment. (You also need to check the IP rating) You can be killed by the OCV of a welding set, if the accident reports are to be believed. In the US they recommend not more than 38V rms AC, or 50V DC.

John, Yes it also happened to me years ago, however, if you look at the links, and the current standards, and "accepted" practice, etc. it is no longer acceptable for this to be possible. The primary and secondary circuits now require total electrical separation. This means I could clamp an electrode holder onto my tongue and stick a wet finger on a true earth and get no shock. (I was going to say another wet part of the male anatomy, but thought better of it, in jest obviously) ;)

I agree with your comment that primary and secondary circuits in a welding set require total electrical separation. This has been the case for a very long time. However, I don't follow your second argument. If there is 80V OCV (open circuit voltage) or thereabouts between the electrode and earth, I think you will get a shock when you touch the earth with your finger. There exists a potential difference, even if the primary and secondary are electrically isolated. Likely to be fatal if you put it on your tongue, as well.

Well said young Paul. On the money as usual mate. As I recall the wielding secondary circuit has nothing to do with 'earth' it is a return path to the secondary winding and as such cannot give an electric shock between the secondary and earth. However... I would not want to connect myself across the secondary winding + / - and 50v or more, but more than happy to plant one 'leg in the ground and hang on to the feed end as in ( #11 :-)

I´m holding the electrode holder, changing the welding consumable. The OCV of the welder secondary is either 50V or 80V, with a current available a maximum 400A (usually around 120A). My workpiece is attached to the other side of the secondary, and rests on the ground (the messy stuff that normal people call ¨ground¨). Now, since I´ve been doing this a while, I know that I need to keep away from the work while changing the welding rod...unfortunately being wet has strange effects.... 80V AC through a 300-ohm body resistance leaves me on the wrong side of a few hundred milliamperes....sometimes I can even get shocked because another welder is working further down the work.... If I had ever got on the wrong side of mains current then we would not be having this discussion. I do like it when people tell me what should be done...because an awful LOT of work places DON´T do health and safety the way theory says they should (and loads don´t do it any way) (hence the mention of extension leads, a LOT of the previous are being used right now....and BS(whatever) doesn´t come into it. Welcome to my world. Where am I working tomorrow?

John Murray has it in a nutshell. Regardless of the electrical separation between primary and secondary, welding is frequently done in environs where there is a connection to earth, whether you want it or not. The original poster described a workplace where this is very likely the case.

This is getting silly now. Taking a modern welding set which complies with the relevant modern standards, say just a couple of years old, which is what I am getting at. The older sets often have a welding return that is connected to the supply earthing system, i.e. the primary side, there by offering a significant potential for electric shock. So forget them for a moment.. First we need to consider the welding set in isolation. There can be no current flow from secondary welding circuit to primary protective circuit, i.e. true earth. The maximum leakage current allowable is 10mA, by design, by product testing and by periodic checks to confirm the safety of the welding set. However, if the insulation resistance also complies with the requirements of the standard, then the maximum leakage will be well below this. The primary circuit is connected to the means of earthing of the electrical supply. The secondary circuit is totally isolated from the primary side. You cannot get an electric shock between the secondary side and true earth, unless you deliberately reference the secondary welding return to true earth. This cannot happen inside the welding set itself. What you are all considering are situations that are extraneous to the welding circuit, you are not considering the welding circuit itself. It is impossible to get an electric shock to true earth from the electrode holder side of the secondary, in a modern welding set where the primary and secondary sides are electrically isolated unless the secondary welding return lead is connected to an object that is at or near true earth potential, or otherwise deliberately connected to something that is at or near true earth potential, or, offers a suitably low impedance path to true earth. That scenario is external to the welding set. I will say again there is no chance of me getting a shock between the electrode holder of a welding set which has correct electrical separation and true earth, unless the welding return lead has been connected to something that is at or near the potential of true earth, or otherwise offers a path to true earth. There is simply no current path within the welding circuit for that to happen. Now if the set has an internal fault, or is faulty by design, or is of an older design, where by the secondary welding return is connected internally to the primary protective circuit, then a shock is possible regardless of the connection of the welding return lead. You are all looking at extraneous issues, not at the welding circuit itself. It seems that is being missed here?

No Jane, I'm not missing it, I work in it and on welding equipment enough. Down to internal levels. It seems from where I am that no one is grasping electrical separation? If the concept of electrical separation is understood, then that's fine. However, this seems not to be the case.

Of course you are right. The secondary is isolated from both primary and earth. Unless the welding return is connected to an item that is, itself, earthed. The electrical earth is connected to earth, literally. So a welded item that is also earthed forms part of the ¨circuit¨. In any case, the potential between electrode holder and the return is either 50 or 80 volts AC, when no arc is struck.

OK, Now if everyone agrees with me on the electrical separation bit, then we can move forward. I fully get the earthed metallic structure being worked on bit. Something we need to consider, is whether in a typical workplace scenario it is better that the secondary is electrically separate from the primary or no? Now due to the proliferation of the most unreliable electrical safety device known to man kind, everyone thinks that electrics can be made safe. In fact they have been mentioned on this thread. They are not the be all and end all of electrical safety, they are commonly known as RCD's and, they are very unreliable. Now, IF the primary and secondary were not electrically separate, a leakage to true earth on the secondary would be detected, now, that could be down to an electric shock, or down to a workpiece offering a low impedance path to true earth. So, if the set has an electrically separated secondary, then your RCD is only protecting the primary. I would suggest that this is poor design, IF it is the only means of protection against indirect contact, and is not allowed under BS7671, however, that stops at the socket, which could be 50m away perhaps. This is something that cannot be taken for granted and should not be ignored, it needs to be properly understood. Another thing that has been said is that the supply cable to the welding set has been replaced and resulted in it becoming unsafe or more dangerous. Why? Why are such uncontrolled and incompetent modifications being undertaken? If you are going to extend the supply cable on a welding set, or use an extension lead, then the impact of this on the protection of the supply circuit and the danger that this can pose must be considered, surely this would come under PUWER, EAWR & MHSWR?...

Dear mods Please delete my posts above as I have no wish to contribute further. Notice to quit IOSH will be in the post. Kind regards Rob

Thanks John and Paul :-) No offence intended to you Jane, a wise head.