When working with electrical equipment I have read that you should keep one hand in your pocket or behind your back. I just want to make sure that my understanding of why you do this is correct.
I reason that this is sound advice so that your free hand doesn’t come into contact with a live wire.
Another reason that comes to mind is that rubber soled shoes are an insulator so if you are working on some electrical equipment it may be possible that you won’t receive a shock unless your free hand comes into contact with some object that is grounded thereby completing the circuit and resulting in a nasty shock? I realize that the rubber soled shoes would not be an insulator for higher voltages.
If you touch high voltage, but don’t touch anything at other voltages, it won’t hurt you. You can grab 220 volts with one hand, and as long as you don’t touch anthing else and your shoes are insulated, it won’t hurt you.
However, if that free hand is touching anything that’s grounded (or at a different voltage/phase), you will complete a circuit and current will flow through you. As an added bonus, as the current goes from one hand to the other, it will pass right through your heart, the most dangerous place for it to be.
In my early days as an electrician, I was always told to either use rubber and/or leather gloves, or put one hand in my pocket when working on live equipment, since current can only pass through your body if you complete a circuit with it. It’s difficult to do any meaningful work on a system with only one hand, however, so I either opt for the gloves or pay very close attention to my surroundings.
Besides, as a practical matter the “one hand” technique is pretty dangerous. If you have a chip of metal embedded in one or both shoes (very common in my shop), or if the soles are worn enough, you could complete the path. If part of your hand is on an insulator that is coated with metallic dust or other conductive gunk, or is deteriorated, then again, the current could go through your hand and give you a nasty shock. I’ve been bit a couple of times by touching a live wire with my fingers and touching a wirenut with a pinhole in it with the back of my hand or my arm. So yeah, in an ideal situation you can grab a live, low-voltage wire and live to tell about it, but in the field it’s not the smartest thing to do. And of course, at higher voltages (thousands of volts) you don’t even need to touch the wire to get severely shocked or killed.
I’ve never met an electrician, or even a home hobbyist who would do anything with one hand.
It seems absurd.
If the power isn’t off, there is almost guaranteed to be an accident waiting for any part of your body, knees, cheeks, or elbows.
The first question I must ask someone who believes in this rule is, “What in the hell are your hand doing in there in the first place?”
Now I’ve certainly heard of this “rule,” and I agree with the other posters that it’s patently absurd. Why? Because if you’re worried that “you may touch a live wire and get electrocuted,” then you’re obviously doing something wrong in the first place, and/or you are not adhering to proper safety rules. Performing electrical work should not be “amateur hour,” but should only be done by those who completely understand the safety rules. (Besides, when performing electrical work, you should use two hands.)
Now having said that, there are (albeit rare) times when it has been a necessity for me to work on “live” 120 VAC equipment. (Troubleshooting comes to mind.) So I follow a few practical rules:
Wear rubber-soled shoes.
Keep your body parts away from earth ground (which could be just about anything).
If possible, power the equipment through a 1:1 isolation transformer. While an isolation transformer won’t do squat if you happen to come in contact with hot and neutral (i.e. both of the transformer’s secondary windings), it will protect you from getting zapped between hot and earth ground (which constitutes 99% of all jolts). If you don’t have an isolation transformer, the next best thing is a GFI.
Some people suggest to also wear rubber gloves. While I don’t think rubber gloves could hurt, I really don’t think they’re necessary if the above rules are followed. Besides, rubber gloves are a pain to work in.
If you’re doing electrical work around the house, then the only concern is getting zapped between 120 VAC and earth ground. (It is very rare for a homeowner to get a true 240 VAC shock, since you never have 240 VAC between hot and earth ground.) But if you’re working with a common mode voltage of 240 AC or higher, then all I’ve got to say is that you better know what the hell you’re doing, else we’ll be reading about you in the paper.
Its not really necessary to put one hand in your pocket, or behind your back. Unless you are a qualified electrician, and you can demonstrate that you would be creating a greater hazard by locking out the circuit, you must have the circuit turned off and locked out before you start to work on it. At least that is what the rules are in the US. Is it true that people don’t always do this, yes. Is it true that people die from this all the time, yes. Darwinism at work.
The old tube type tvs were a joy to work on.
Many many a time I only used one hand.
Many many a time I was seen nursing a sore elbow which hit the wall after jerking my hand out of a tv after getting bit.
Summertime was worst, sweaty hands and arms.Lots of scrapes from jerking away after getting bit.
I agree with you for the most part, hardhead365, but there are times when the only practical option is to work on “live” equipment. For example: troubleshooting a piece of equipment. While it is theoretically possible to troubleshoot a “dead” circuit, the faulty component is usually isolated much, much quicker when you take voltage, current, and/or frequency measurements when the unit is powered.
If you would like to know what the actual rules are (in the U.S.) you can find them at www.osha-slc.gov/OshStd_toc/OSHA_Std_toc_1910_SUBPART_S.html. They are about halfway down the page. You are right Crafter_man infeasability is the other reason for a **qualified ** electrician not to lockout.
If you’re working in conditions where the possibility that your free arm might come in contact with a live wire, you’ve got bigger problems to worry about besides whether your hand should be in your pocket.
Anyway, I’ve watched plenty of licensed electricians working, and you need both hand to do your job. Putting one in your pocket or behind your back would make the job more risky, not less. As noted above, rubber soled shoes, insulated gloves, and insulated tools are a much better idea.
I was watching some story on TV, where these people were workng on high volatage power lines where there was no easy access, except by air. They’d fly there in a helicopter, and the guy who was going to do the work had an electric cable, like for jumping cars, and also a wire with a metal stick on one end, which was attached to the cable.
They’d approach from the air, and he’d hold out the stick, and sparks would go between it and the power line (which was at 10’s of thousands of volts). When he was close enough, he’d touch the stick to the power line, so the whole helicopter was at the same AC potential as the line, then clamp the cable to the line.
Then he would move onto the power line, and holdng the stick on the helicopter, release the cable from the helicopter, which could now fly away, leaving the worker to do his work on the power line while it was live.
I’m not sure what work he he was actually doing on the power line.
In certain rare cases, it is perfectly acceptable for a highly trained/qualified electrician or engineer to work on bare conductors at high voltages (even tens of thousands of volts) with their bare hands. However, there are extremely strict rules which must follow in order to do so, and special (and approved) isolation equipment must be used. In a nut shell, the electrician is very, very, very well insulated, and the risk of electrocution is virtually zero if the special training, approved equipment, and procedures are properly utilized.
On the subject of infeasibility, according to regulation 1910.333you can work on energized circuits if deenergizing them is “infeasible due to equipment design or operational limitations.” And “operational limitations” are defined to include (also in 1910.333):
I do a lot of troubleshooting on machine tools and process-control equipment that cannot be shut down without either disrupting plant operations or requiring the operator to reload a bunch of tool offsets, part programs, and machine parameters, a pretty lengthy process on some of the ancient machinery we have in my shop. We do wear PPE to make it as safe as possible, needless to say.
And on the subject of rubber gloves, I find them a total pain in the ass to use, but my company recently adopted regulations (stricter than OSHA’s, I believe) that require that we use them and stand on a rubber mat when working on live circuits of 120VAC or 50VDC or greater (I don’t always use the gloves, I must admit). Between the gloves, mat, glasses, boots, hat, and insulated tools I could probably get hit by lightning and keep on working. It’s better than being dead, though.
While I think it’s important to use proper safety equipment, nothing is more important than using your head. An intelligent, well-trained, and attentive person with a minimal amount of safety equipment is usually in a much safer situation than an amateur with an abundance of safety equipment.
Definitely. When I first started as an apprentice electrician about five years ago, I met a man (one of our shop production planners) that had lost his left arm, a couple of fingers on his right hand, and been severely scarred on the back of his head after getting hit by 10,000 Volts. About ten years earlier, he had been an apprentice, and had walked into a 10kV station that had previously been deenergized (and the high-voltage breaker disconnected), in order to check the dimensions of some of the bus bars for the construction of a piece of phenolic board that was to be placed between them.
What he didn’t know was that the station feeder had been energized a little earlier and no one had told him, so the incoming line to the station was hot. He didn’t hear the telltale hum of the transformers because the breaker was open, walked into the station, and got too close to the incoming line with a metal-tipped ruler. Because he was leaning against the metal cage that enclosed the station, the arc went down his arm and out through his shoulder, but it still did plenty of damage to some other parts of his body. I’m still amazed that he survived.
Sorry about the hijack, but seeing that man and hearing his story really impressed the importance of attentiveness, common sense, and the capricious nature of electricity on me. His supervisor was punished for what happened, but by then it was too late. He lost an arm and spent years in and out of hospitals because of a moment of carelessness. Ultimately, an electrician can’t trust anyone but themselves for their own safety.
Your friend may have lost a limb but he was lucky to survive at all.
The damage to various nerves can mean a lifetimes treatment in potassium supplements and thyroxin.
Unfortunately our mains frequency in the UK is about the ideal for stopping the human heart - 60hz.
It isn’t realistic to work on machine plant when it is completely isolated and single handed operations are just unfeasable.
My next door neighbour has an interesting job, he is the one who goes out on the cage carried by helicopter to maintain the 275kV and upwards overhead lines - live.
He has to wear what can only be described as a chainmail suit when doing this.
The big plus is that to do his work it generally takes all week to get everything in position and then its usually a fifteen minute job checking that bolts are torqued up correctly.Easy life or what.
One of the problems I have found when working on 11kV gear is that the tools have be made of relatively soft materials which can be a total ball ache when they have not been maintained correctly.The last thing you want in such situations is that the jaws of spanners slip or screwies to be rounded off.
As far as isolation is concerned, any electrician knows that no circuit is off until they themselves have pulled the fuses and discharged the conductors - stuff the senior engineer and his permit to work system.