Our Health & Safety department has gone on an electrical kick for the first time since I've been working here. This could be good as I might finally get the equipment I want. It could be bad in that everybody may be disallowed from using meters to check voltages.
What is the take from OSHA and NFPA 70E for "working" on live electrical from 120 VAC up to 480 VAC? When I say "working", I mean simply opening up a power or control panel and either testing the voltage with a meter or clipping on the analyzer probes. Our Health & Saftey guys just sent over some photographs of some guy wearing gloves and protectors while checking the voltage on what appeared to be a 480 VAC panel. Is this really required when the probes themselves are already 1000 V insulated?
I am trying to round up a copy of NFPA 70E so I can discuss such things with those guys. Any head start you might give me would be appreciated, though.
I believe you can get by with just the insulated tool (probe in this case) up to 120/240V. For 277/480V you need insulated gloves. My recommendation is to use insulated gloves anyway. Also, no manmade fibers (cotton, etc, only). Some 480V will require Nomex I believe. Again, better to overdo it on the safety equipment than to be injured. I would also recommend a face shield for 480V.
Where I work the safety goes something like this. Up to 480 V safety glasses, and gloves rated at 5kv over 480 to 1000 V Nomex coveralls, face shield, and gloves rated at 5kv over 1000 V Blast suit, face shield, gloves and hot sticks, insulated mats and blankets
I was party to a recall with Klein insulated tools. Never trust your life to an insulated tool. They are all right to have and to add to the safety but not by themselves. We test our equipment every 6 months. I have only gotten back one glove from testing that was ok, usually I get a new pair. Heat is hell on them, or at least that is what we all believe.
I don't think that NFPA 70, (National Electrical Code or NEC). is going to help as far as "personnel protective equipment" goes, this is more of an OSHA issue, besides I think that I paid about $60 for my personnel copy of the NEC. I have heard from sales reps and others that a two or three years ago that OSHA came up with new guidelines in PPE for energized electrical work over 50 volts to ground, if you can navigate the
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web site and figure this one out, I'd have to say your darn good. I was unable to find a "exact" answer. What I have heard is that working within three feet of anything energized 50 volts or over requires gloves, helmet, boots, faceshield, etc, etc, etc rated at 1000 volts and tested. My personnel feelings are this, if you don't know what 480 volts at 2000 amps can do to you if you touch it, then stay the f_ck out! Leave it to the maintenance guy that does know! Safety safety safety, a part of safety is that you understand all the systems involved with a piece of equipment, if you don't know "STAY THE F_CK OUT"!!! and I'll fix it rather then undoing your b.s. and doing it right. Sorry, I just had to put my little maintenance quote in here for all the idiots I work with.
I'd say what you are encountering is becoming more common. As far as it being necessary, well .... I see a lot of otherwise smart electricians working in MCCs wearing watches, rings, or other jewelry items. I think thats a dumb idea as its just something else that can catch on a live part. My guess is someone managed to kill hisself doing something stupid, and now everyone wnats to prevent it on their watch.
I think you can safely make a distinction sometimes between stuff that is more dangerous to work on, at whatever voltages. A lot of plants now expect fingersafe terminals or plexiglass shields on anything that is over 24V. usually they have access holes to allow you to put your meter leads in and check a fuse or something. These are much safer to work on as there are no exposed live parts you might fall into, or inadvertantly touch.
OTOH - sometimes its just a good idea to do things the same way all the time in a known safe way, and you never know just what you might run up against. maybe the last guy that changed a fuse didn't bother to secure the plastic covers and when you fall against them, you might get that little tingle, and do the dance.
The advice above might seem excessive, but all one has to do is see the results of a good flash arc burn to appreciate safety equipment.
I recently evaluated an accident scene where there were severe injuries involved.
Two electricians were working in the back of a 480v 4000a distribution switchgear center. They locked out one section of a 2000a motor control center feeder, and proceeded to change the output phase orientation. They didn't shutdown the entire distribution center as the buses in the section they were working in were guarded. One of the phase conductors slipped out of the person's hands doing the actual work, and managed to slide through a small opening in the guard hitting one of the live phase buses. On the motor control center end the conductors for the phase in question were common. On the distribution end the other phase conductors had been removed, and some were resting against the metal enclosure.
The resulting arc flash ionized the air with all phases going common with each other, and ground. The fellow doing the work was wearing a flash hood with face shield, Nomex jacket, and appropriate gloves. He received no burn injuries to his skin, his Carharts were partially burned from the waist down, and he was flash blinded for about tem minutes.
His safety? observer wasn't wearing any protective gear because he wasn't doing any work, it was hot - he didn't want to get "all sweaty", and the circuit involved was dead. Even though he was standing about two feet back, and to the side of the person doing the work, he received severe 2nd and third degree burns after his shirt - upper pants were burned off, and had his face and arms peppered with molten pieces of copper. The distribution center took about four days to repair.
I guess feeling you are safe isn't as good as wearing the equipment, and being safe.
It would have been interesting to have the ball of fire that came out of the distribution center on video.
The photos are accurate. I personally wear gloves and a flash shield when probing in a live cabinet. As a consultant who investigates electrical accidents, I have seen the results of both electrocution and arc flash accidents.
The latest OSHA and NFPA70 regulations address arc flash hazard as well as electric shock. There is a lot to digest. There are various clearance distances depending on the voltage levels involved, what personal protective equipment you are wearing, and your level of "qualification". I recommend that the organization go through OSHA training to become familiar with the requirements.
NFPA 70E 2000 states in Section 2-1.3.3.2 that if arc flash calculations have not been performed the Flash Protection Boundary for systems operating under 600 volts is 4 feet.
.The NESC and OSHA require an approach distance of 12 inches for live 480 volt equipment.
.Appropriate protective gloves, face shield, and clothing should be worn when working within the Flash Protection Boundary or within the approach distance.
.The preferred method for working on electrical equipment is to turn off the equipment and lock it out or insulate the exposed parts using blankets, barriers, etc. - but if this cannot be done proper Personal Protective Equipment is required.
.Unfortunately, the NEC does not contain work rules like the NESC. While a great deal of NEC training is performed and is mandatory, learning safe work rules is not mandatory by most jurisdictions that enforce licensing and the NEC.
In most cases I would say that assuming that the circuit is hot will not pose any threat. However, assuming your coworker shut off the power can and will be deadly.
Right. Not quibleing about testing the circuits. Just don't trust 'insulated test probes' when dealing with anything over 120/240. Personally, I wear gloves when testing higher voltages. Once I know they're dead, then the grounding hooks go on. *THEN* and only *THEN* do the gloves, faceshield & other ppe come off!!!
in article 5iXqb.38386$ snipped-for-privacy@twister.nyroc.rr.com, daestrom at daestrom@NO_SPAM_HEREtwcny.rr.com wrote on 11/7/03 5:04 PM:
Remember, if you are working with capacitors or rotating machinery, you need to bleed the source to make sure that capacitors are dischagred or machines stationary before the solid ground connection is made. Othewise, there may be considerable excitement.
Especially with high voltage capacitors, such as those in CRT displays, which seem to undergo some form of plastic deformation in the dielectric. You discharge them first with a bleed and then with with a short circuit, disconnect it,come back a few minutes later and get a belt off them.
Not just discharge, *leave* the grounding on. Just grounding for a few seconds is not enough. Many folks understand the capacitor problem, not many bring up the rotating machinery. I agree though. Showed one of my crew this one time. We had just grounded everything, and before starting work, I had him disconnect the grounds and hook up a voltmeter between winding and ground. We sat there for five minutes watching the voltage climb back up from
When I was a zoomy, i.e. USAF enlisted, low these many years ago, one of our installation crew asked the sergeant why he couldn't lift the large capacitors by the terminals when the manufacturer had provided a bar across the two terminals that made such a convenient handle. The sergeant explained that the bar was there to short the capacitor to keep it from developing a dangerous charge during shipping and storage. The questioner was unconvinced and thought the sergeant was just being anal. Twenty minutes later when he was moving the "bad" capacitors that we had replaced he grabbed one by both unshunted terminals. Bad move.
in article Tzdrb.17335$ snipped-for-privacy@newsread1.news.atl.earthlink.net, Tom Horne at snipped-for-privacy@mindspring.com wrote on 11/8/03 1:51 PM:
What really frosted me at one time was that someone was in a hurry to measure the capacitance of a number of capacitors. He clipped the shorting wire so that he could connect the bridge easily. The short was never reconnected.
There are people out there who give not consideration to their fellow man. They are go-getters who do not want to waste there time to maintain safety. That is someone elses problem. They are not willing to go out of their way at all if it hinders their promotion.
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