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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Stephen Swaffer on December 23, 2013, 04:55:07 PM
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Mike, I agree with you about arc flash safety-I hope you can get techs to understand the importance of taking precautions. Around here, it seems like even electricians aren't concerned about arc flash. Having worked in a facility that had the arc flash studies done and used the gear, I would think a long sleeve cotton shirt, leather gloves, safety glasses and hearing protection would serve most techs well. Those are inexpensive safety precautions to implement. Of course, if you are working on a 480 V panel or greater than 200 Amp you definitely need to find out what is appropriate or find someone who does know.
I know electricians are "expensive" and I like to do things myself, too, but often much of the cost difference between me doing a project and a "do-it-your-selfer" is the cost of the materials I use to do it right vs taking a short cut. I would guess that most electricians hourly rate is comparable to what sound/lighting techs charge-and in any event is certainly less than ER doctors and burn units charge. I have made major equipment decisions based on the thought that while another route may be cheaper in the short run, one trip to the ER or a few weeks of missed work might be far costlier! It might be wise to get to know an electrician you use for larger projects (or for tie-ins so that you have someone that the legal people would view as qualified) that would be happy to give advice on smaller projects-in order to keep his customer healthy.
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Having worked in a facility that had the arc flash studies done and used the gear, I would think a long sleeve cotton shirt, leather gloves, safety glasses and hearing protection would serve most techs well. Those are inexpensive safety precautions to implement.
Yes, I would agree that your list could be workable. Cotton shirts are way better than polyester which melts into your skin from an arc flash (no kidding). Safety glasses are always an excellent idea, but most companies won't rate glasses for arc flash, insisting on face shields instead. And lightweight gloves would work since power under 600 volts is considered "low-voltage". I also have 3M sending me a pair of their ARC Plug earplugs which allows for normal conversation, but shuts out impulse noises and explosion decibels. See http://tinyurl.com/lvj2v57
But we'll have to convince OSHA that these simple precautions are sufficient. As I'm sure you all have done (as have I) we often tie in camlocks with no more protection than a layer of sweat and a t-shirt. As you know from your own arc flash training, the type of PPE (Personal Protective Equipment) is dependent on energy levels. So the total fault currents available on various sound and lighting distros would need to be reviewed. However, I personally feel that anything would be an improvement over the lack of any protection at all.
And in the interest of complete disclosure, I lived through an arc flash less than 2 ft from my face in 1970 when I was about 15 years old and helping a master electrician tie in some new circuit breakers in my parents' house. He was an electrical instructor at a tech school and I was doing an electrician apprentice program. He insisted I have on my safety glasses and long-sleeved cotton shirt, so he was ahead of his time, I think. While horsing a ground wire around the side of the panel using a pair of insulated electrician's pliers, I nicked the insulation on the 100-amp service ahead of the main fuses. What happened next can only be described as a bomb going off in my hands. It vaporized about 3 ft of 14 gauge wire in a ball of light that sounded like a shotgun blast. I was standing on a wooden chair with my one hand still in the box, and my teacher was telling me to stand very still.
I saw a much bigger one later involving a 600-amp/480-volt feeder, but lucky for me I was about 100 yards away from it. More on that arc flash later.
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I saw the feeder for about 5000 houses shorted out one night. I was about 100m away. It lasted about a second and a half and seemed brighter than the sun.
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I have no arc flash training, but I am aware of it.
One of the industrial facilities where I provide network support has a bank of large enclosed switches (the kind with a swinging door and a lever on the side).
Next to this bank is a sign reminding operators to do the following (in addition to wearing PPE) when actuating a switch:
- Turn your face away from the panel
- Stand to the side opposite the hinge
The reason for the first is obvious. The reason for the second -- I assume -- is to protect the operator from the door being violently flung open from an arc flash explosion. It would also protect the operator from some of the arc flash.
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I saw the feeder for about 5000 houses shorted out one night. I was about 100m away. It lasted about a second and a half and seemed brighter than the sun.
I love this one. Not technically an "arc flash" but certainly a really big arc...
http://www.youtube.com/watch?v=NQQMK1Rvq0A
Just added a compilation video including the one above. My favorite quote is "If it blows up, get ready to hit the ground".
http://www.youtube.com/watch?v=_2LpCdhuOyQ
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As far as arc flash safety and the entertainment industry is concerned, it might make more sense to address mitigation of the hazard versus using the proper PPE?
The arc flash safety emphasis has been industry. Most industrial facilities have a large number of panels that are relatively infrequently accessed so taking PPE with you makes economic sense. I would surmise that most entertainment venues would have a handful of panels allocated to tie-ins from touring lighting and audio contractors-and those would be accessed frequently so perhaps mitigating the hazard would make more sense.
I saw a video by Cooper Bussman a few years ago-and they have white papers on the subject (no doubt driven by the desire to sell fuses!) regarding the advantages of their Low Peak fuse designs in controlling arc flash.
Fuses have been given a bad rap by the Edison fuse-which being available in sizes to 30 A in the same form factohas resulted in a very high percentage of systems using it being overfused. But the fact is, they are more reliable and can react quicker protecting both personnel and equipment.
Obviously, losing a fuse during a performance is more of a problem than tripping a breaker, but if carefully thought out and designed, fuses could be used to provide safety with a smaller breaker providing overload protection-much like what is down with motors and overloads.
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As far as arc flash safety and the entertainment industry is concerned, it might make more sense to address mitigation of the hazard versus using the proper PPE?
The arc flash safety emphasis has been industry. Most industrial facilities have a large number of panels that are relatively infrequently accessed so taking PPE with you makes economic sense. I would surmise that most entertainment venues would have a handful of panels allocated to tie-ins from touring lighting and audio contractors-and those would be accessed frequently so perhaps mitigating the hazard would make more sense.
I saw a video by Cooper Bussman a few years ago-and they have white papers on the subject (no doubt driven by the desire to sell fuses!) regarding the advantages of their Low Peak fuse designs in controlling arc flash.
Fuses have been given a bad rap by the Edison fuse-which being available in sizes to 30 A in the same form factohas resulted in a very high percentage of systems using it being overfused. But the fact is, they are more reliable and can react quicker protecting both personnel and equipment.
Obviously, losing a fuse during a performance is more of a problem than tripping a breaker, but if carefully thought out and designed, fuses could be used to provide safety with a smaller breaker providing overload protection-much like what is down with motors and overloads.
I'm an arena sparky. I'm one of the folks that does your road show power when it comes to our PAC, arena(s) or couple other places.
None of the major venues have "live" boxes; i.e. the disconnect switch is tagged/locked out at its master breaker or the physical design has shunt-trip and connector chamber switches that de-energize the entire panel when opened. Almost all of the newer venues have CamLock and/or Posi-Lock connections with additional wire tails capability. Most of the tie-ins (not direct Cam connections) I do these days are with generators or in a couple of older theaters.
I don't work in live panels. Ever. That shit kills people and burns down buildings. One of the things that defines "qualified" is knowing when one is NOT...
Don't take the above as an attempt to minimize PPE, it's not... After working in production for nearly 30 years and as a show electrician for 14 years, I've seen all kinds of dodgy stuff. What I've observed, though, is that if I need the level of PPE to deal with a potential arc flash the situation is above my pay grade. Mitigation of hazard, beginning at the design stage, is the best practice IMHO.
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I am not a sparky, but my day-job system uses a lot of electricity. Around a hundred gigawatt hours per annum. Downtime costs serious money. Really serious money.
How much live power work do we have done? Zero. Zilch. Live power work is for cowboys.
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Not to be argumentative, but, Lyle, would you have every electrician that does any wiring upgrades to a home call the utility and cut the power to the home at the transformer? That is the only way to get a de-energized system in a home-or really in any occupancy ultimately you can't keep de-energizing upstream. (Even shutting off the main leaves energized conductors in the panel.) And troubleshooting can be very challenging when all power is disconnected.
Part of LOTO is verification-which unless indicators have been designed into a system requires use of PPE appropriate for a live situation until verification is complete. Please don't tell me I am the only one that has ever shut off the wrong breaker knowing I had the right one?
A typical home arc welder runs at 30-40 volts and 60-100 amps-plenty of arc for a burn, and indeed 70E calls for "PPE" for anything above 50 volts or so. I doubt you would consider that above your pay grade? PPE doesn't have to mean a spacesuit-it might be that the items I mentioned in the OP are enough-they are inexpensive and simple IF we think about them.
I am not arguing for making life difficult-we all tend to get comfortable with things and that is when people get hurt.
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Residential power down here has a unscrewable (with an insulated pole) fuses on the ceramic insulators where the cable enters the house, breakers in the outside meter panel, and individual circuit breakers for each circuit on an inside panel. If something needs to be rewired, turn it off, lock it out, short it out, ...
Obviously problems need to be recreated to find the fault. I'm not suggesting that nobody ever measures live power.
In an industrial setting, the need to work on live and loaded circuits is something that comes from poor planning. If the site isn't built to be concurrently maintainable then that is a design/management problem. We don't ask our sparkys to put their lives on the line because someone made a cheap design choice five years earlier. If a whole site needs to be shut down for electrical works then we make sure we make use of the outage to install enough additional panels/breakers/switching/etc that next time less needs to go offline.
I was not suggesting people don't use PPE. Far from it, I was suggesting people work out how to reduce risks even further.
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Here's some pictures of an arc flash that killed two wannabe copper thieves. Even though the police story stated they were "electrocuted" when cutting through a high-voltage wire, I'm pretty sure there was an arc flash that produced the severe burns shown in the pictures. Note what appears to be fiberglass handled bolt cutters they used for cutting the live wire. So I'm proposing that as the wire carrying hundreds of amps and thousands of volts was cut, there was an arc flash at the point of separation which rapidly grew into a full arc. So not really an electrocution, but an arc flash blast from the high voltage and current. But dead is dead...
Don't open this link if you have a squeamish stomach or don't want to see dead bodies. You have been warned:
http://www.thepadrino.com/2012/02/copper-thieves-electrocuted-trying-to.html (http://www.thepadrino.com/2012/02/copper-thieves-electrocuted-trying-to.html)
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That seems a minor distinction. I recall seeing a safety film presented by the local power utility with lots of gory photo's including people who lived but were maimed by serious high voltage hits through a limb for example. Kind of like those cheap hot dog cookers that run electricity through the dog...
Probably worth being exposed to (the film not the shock).
JR
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I recall seeing a safety film presented by the local power utility with lots of gory photo's including people who lived but were maimed by serious high voltage hits through a limb for example. Kind of like those cheap hot dog cookers that run electricity through the dog...
When I worked doing industrial power in the 70's, OSHA was just getting started and they did a few presentations with photos of arc flash and high-voltage shock injuries. It was pretty gruesome stuff. While the dead bodies were bad enough, the pics that really bothered me were the ones who lived through it. Hot dog cookers only begin to describe what these injuries looked like.
The key to understanding arc flash is that it doesn't take a lot of voltage to make one, and even 120-volts with a sufficiently large circuit breaker behind it can make quite a fireball. Of course, add high voltage to high amperage and you get a very serious bomb. Let's be careful out there...
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This is the first time I've seen an Arc-Flash warning on a 3-phase service panel at a church. Nothing special for AVL, just a rack with four QSC amps and some processing, plus a basic dimmer rack in the next wiring closet. No cam-locks or anything special. This was in western Florida, so I don't know if local code or an inspector required it to be labeled as such.
BTW: I just received a pair of EAR ARC blast earplugs for evaluation. This will be part of my study and article on arc flash protection for sound technicians.
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This is the first time I've seen an Arc-Flash warning on a 3-phase service panel at a church. Nothing special for AVL, just a rack with four QSC amps and some processing, plus a basic dimmer rack in the next wiring closet. No cam-locks or anything special. This was in western Florida, so I don't know if local code or an inspector required it to be labeled as such.
BTW: I just received a pair of EAR ARC blast earplugs for evaluation. This will be part of my study and article on arc flash protection for sound technicians.
Mike, I suspect that the sticker might be supplied by the enclosure supplier. At the probable cost of ten cents or less per unit, the device maker could include it in the box with instructions that the installer place it on the door. Such a strategy would (might) help avoid product liability damages if/when an arc-flash occurs and somebody is injured or killed. Mark C.
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Mike, I suspect that the sticker might be supplied by the enclosure supplier. At the probable cost of ten cents or less per unit, the device maker could include it in the box with instructions that the installer place it on the door. Such a strategy would (might) help avoid product liability damages if/when an arc-flash occurs and somebody is injured or killed. Mark C.
You could be right. I always forget about the lawyers... ::)
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You could be right. I always forget about the lawyers... ::)
Arguably, lawyers are the ultimate safety plan enforcers. They get folks to pay attention when folks won't do the right things on their own.... Mark C.
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Warning labels are now required by code (NEC 2011 110.16) in non residential applications-I think the 2014 adds the requirement to residential. Enforcement hasn't been real strict in my experience-yet!
Steve
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from NEC 2014
110.16 Arc-Flash Hazard Warning. Electrical equipment,
such as switchboards, switchgear, panelboards, industrial
control panels, meter socket enclosures, and motor control
centers, that are in other than dwelling units, and are likely
to require examination, adjustment, servicing, or maintenance
while energized shall be field or factory marked to
warn qualified persons of potential electric arc flash hazards.
The marking shall meet the requirements in 110.21(B)
and shall be located so as to be clearly visible to qualified
persons before examination, adjustment, servicing, or
maintenance of the equipment.
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from NEC 2014
110.16 Arc-Flash Hazard Warning. Electrical equipment,
such as switchboards, switchgear, panelboards, industrial
control panels, meter socket enclosures, and motor control
centers, that are in other than dwelling units, and are likely
to require examination, adjustment, servicing, or maintenance
while energized shall be field or factory marked to
warn qualified persons of potential electric arc flash hazards.
The marking shall meet the requirements in 110.21(B)
and shall be located so as to be clearly visible to qualified
persons before examination, adjustment, servicing, or
maintenance of the equipment.
There you go.... that 'splains it.
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from NEC 2014
....marked to
warn qualified persons of potential electric arc flash hazards...shall be located so as to be clearly visible to qualified
persons before....
Why do "qualified" people need to be warned that an arc flash hazard exists inside an electrical panel? Shouldn't that be a crucial part of their "qualification"?
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Why do "qualified" people need to be warned that an arc flash hazard exists inside an electrical panel? Shouldn't that be a crucial part of their "qualification"?
Well, yeah.... And these were big 3-phase panels that DIY guys have NO BUSINESS being inside of. But the NFPA has got to start somewhere, I suppose. I've met a lot of "old" electricians who don't know or follow code anyway, so perhaps a warning label on the box will make them think/ask about Arc-Flash before they dive into one.
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OSHA is proposing a fine of $119,000 to Pure Power Technologies for failure to supply proper Arc Flash protective gear. See the story at http://ecmweb.com/news/osha-cites-pure-power-technologies-after-worker-burned-electrical-arc-flash-waukesha-foundry?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+ECMMostRecent+%28Electrical+Construction+%26+Maintenance%29&Issue=ECM-04_20140127_ECM-04_378&NL=ECM-04&cl=article_12_b&sfvc4enews=42&YM_RID=mike%40noshockzone.org&YM_MID=1445461 (http://ecmweb.com/news/osha-cites-pure-power-technologies-after-worker-burned-electrical-arc-flash-waukesha-foundry?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+ECMMostRecent+%28Electrical+Construction+%26+Maintenance%29&Issue=ECM-04_20140127_ECM-04_378&NL=ECM-04&cl=article_12_b&sfvc4enews=42&YM_RID=mike%40noshockzone.org&YM_MID=1445461)
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FYI: The January issue of EC&M has a very good article about Arc Flash Calculations vs. Tables. Read it at http://ecmweb.com/january-2014#46 (http://ecmweb.com/january-2014#46)
I've not had time to read the entire article yet, but I'll absorb it over the next few days.
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Just in Rochester NY this morning... A very bad Arc-Flash burn to a subcontractor. Here's a link to the newspaper story.
http://www.democratandchronicle.com/story/news/2014/02/20/hurt-rochester-explosion/5640609/ (http://www.democratandchronicle.com/story/news/2014/02/20/hurt-rochester-explosion/5640609/)
Text of the article is pasted below.
A man was injured from an electrical explosion at Advanced Glass Industries Inc. on Emerson Street just before 11:30 a.m. Thursday.
Rural Metro Ambulance Services reported that the man, 57, was taken with flash burn to Strong Memorial Hospital after the explosion, which occurred at 1335 Emerson St. He received burns to 25 percent of his body, mainly to his face, hands and arms, according to Capt. Joseph Luna of the Rochester Fire Department.
The man was a subcontractor who had been hired by the business to do electrical maintenance work, said Rochester Fire Department Battalion Chief Dan Mancuso. He said an electrical arc, or an exposed current between two conductors, caused the injury.
Advanced Glass Industries is one of the world's largest suppliers of precision machined optical glass blanks, molded optical glass blanks and slumped optical glass blanks, according to the company's web site. The company was founded just after World War II as Fischer Optical, according to the website.
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Iowa OSHA Issues Citations for Arc Explosion
Workers connecting an energized 800-amp panelboard without proper safety training or PPE creates some very dangerous arc-flash injuries. See link and article text below.
http://tinyurl.com/kssnpww (http://tinyurl.com/kssnpww)
The Iowa Division of Labor Services Occupational Safety and Health Bureau has cited three entities in an arc flash explosion last July in Sibley, Iowa. I-OSHA says the accident happened when workers were switching over electric lines at Timewell Drainage. After its investigation, I-OSHA cited City of Sibley Electric Department, Timewell, and Current Electric of Sibley.
KIWA Radio reported that the issue occurred when workers were installing new electrical wiring to an 800A interior panelboard. I-OSHA said work was being performed while the wiring was energized, and people were allowed in the immediate area without personal protective equipment (PPE). After installation of wiring to the panelboard, the employer was confirming that proper function of the equipment had been achieved. Lock and tagout was not applied, ensuring that the equipment was not energized prior to installation of the panel cover. The reportt stated that people were in the immediate area and were exposed to an arc flash and/or arc blast, and life-threatening injuries were sustained.
Five people were sent to the hospital.
According to I-OSHA and the radio report, Current Electric should have conducted frequent and regular inspections of job sites, materials, and equipment. Current Electric supposedly did not instruct each employee in the recognition and avoidance of unsafe conditions and the applicable regulations.
Last fall, Timewell Drainage was cited for not instructing their employees in the recognition and avoidance of unsafe conditions, and for employees not wearing PPE. The City of Sibley Electric Department was cited because controls deactivated during the course of work on energized or de-energized equipment or circuits were not tagged on the worksite involving the energizing and deenergizing of a transformer with an incoming line voltage of thousands of volts.
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This article mentions another issue with arc flash and that is safety area/barrier. The standard specifies a distance for wearing PPE, another that "qualified" personnel are allowed to approach and a greater distance for non-qualified people. Bottom line=expose as few people as necessary to the arc flash hazard. I usually ty to form some sort of barricade-doesn't take much -to keep people back. One, to keep them from a hazad, two, the last thing I want if I am n an energized panel is a non electrician trying to look over my shoulder-especially if I need to get away!
Interestingly, I was redoing a similar service a year ago and redoing underground service conductors to a transformer. The POCO employees asked me if the I wanted primaries (less than 3 feet from where I was digging) de-energized. Really? You have to ask?
w
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This article mentions another issue with arc flash and that is safety area/barrier.
Also, failure to use Lock and Tag-Outs is a VERY dangerous thing. That's the first thing I learned to do back in the 70's when I was working on industrial power.
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This article mentions another issue with arc flash and that is safety area/barrier. The standard specifies a distance for wearing PPE, another that "qualified" personnel are allowed to approach and a greater distance for non-qualified people. Bottom line=expose as few people as necessary to the arc flash hazard. I usually ty to form some sort of barricade-doesn't take much -to keep people back. One, to keep them from a hazad, two, the last thing I want if I am n an energized panel is a non electrician trying to look over my shoulder-especially if I need to get away!
Interestingly, I was redoing a similar service a year ago and redoing underground service conductors to a transformer. The POCO employees asked me if the I wanted primaries (less than 3 feet from where I was digging) de-energized. Really? You have to ask?
w
Of course underground infrastructure is always exactly where the city records say it is.... :-)
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Also, failure to use Lock and Tag-Outs is a VERY dangerous thing. That's the first thing I learned to do back in the 70's when I was working on industrial power.
At my industrial manufacturing day job there's one more item added to that list: Lock Out, Tag Out, Try Out. Verification is also important.
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There is one thing more dangerous than not doing LOTO-and try out. That is messing with MY lock out tag and lock!! :) Corey is right though-I have come across more than one disconnect that had parts missing (removed?) so that nothing actually disconnected when the handle was thrown.