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Lockout-Tagout

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Re: Lockout-Tagout

#101

Post by alsysadmin »

I've spent many career years in sysadmin / process automation for manufacturing companies, and LOTO is one of many pieces of proper procedure and process that really impresses me about that industry. I worked at a big steel recycling plant, and the zero tolerance effort put toward safety and generally ensuring that this type of stuff was upheld was impressive. Not locking out a machine, or forgetting your lock on a machine was a fireable offense with like, one warning I think. You certainly didn't want to be the guy who was working on a machine that morning, and left your lock on it when you went home while someone else was working on it. They'd call you and get you out of bed real quick if it meant the machine couldn't start up because your lock is on there and you weren't accounted for.

SRE's and operations people can pick up good habits from manufacturing gigs. A lot of the same concepts like uptime, good documentation, procedure, discipline are really important to the business at all levels. When lives are at risk good companies put a large sum of time and money in making sure everyone is on the same page.

Re: Lockout-Tagout

#102

Post by jjeaff »

michaelt wrote: post #54
jjeaff wrote: post #50

Earlier quoted context omitted.

110v or 240v will kill you dead where you stand. But it's not really about the voltage. The higher the voltage, the easier it is for the electricity to ground out through you. But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps. Luckily, human skin is not highly conductive and neither are rubber soled shoes. So if you are taking proper precautions and not kneeling…

> 110v or 240v will kill you dead where you stand. In my experience, when encouraging people to follow safety rules you get better results with true examples that justify the rules than with exaggeration like this. If you tell a person one thing they know isn't true, they're liable to start thinking the other things you tell them aren't true. 240v might kill you if you're up a ladder, elderly, have an undiagnosed hea…

>guaranteed instant death that, say a 25kV shock is

Also not true.

You can safely hold a metal rod into the air as a 20,000 volt tesla coil fires lightening bolts through the air and into your body then to the ground, because the coil is built in such a way to induce very little amperage across your body.

My point being, it's not just the voltage.

I was just imprecise with my language. What I should have said is "110v or 240v could kill you dead". And that is why the following sentences qualify what I was saying.

Household voltage is plenty to kill you, assuming the factors are aligned.

I have been shocked multiple times with household 110v and it was not pleasant at times and others it was barely a twinge. It all depends on how well you are grounded.

I had a very unpleasant shock once from a 12v car battery because I was sitting on the ground in shorts and fiddling with it somehow.

Re: Lockout-Tagout

#103

Post by jjeaff »

ttsda wrote: post #71
jjeaff wrote: post #50

Earlier quoted context omitted.

110v or 240v will kill you dead where you stand. But it's not really about the voltage. The higher the voltage, the easier it is for the electricity to ground out through you. But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps. Luckily, human skin is not highly conductive and neither are rubber soled shoes. So if you are taking proper precautions and not kneeling…

It's impossible for a 240V outlet to deliver 10A through your body. Unless you're made of metal or something.

But you don't need 10Amps to kill you. Just a few hundred milli-amps is enough to kill a human.

Re: Lockout-Tagout

#104

Post by jjeaff »

LeifCarrotson wrote: post #59
jjeaff wrote: post #50

Earlier quoted context omitted.

110v or 240v will kill you dead where you stand. But it's not really about the voltage. The higher the voltage, the easier it is for the electricity to ground out through you. But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps. Luckily, human skin is not highly conductive and neither are rubber soled shoes. So if you are taking proper precautions and not kneeling…

I was working with a circular saw and extension cord on a ladder in light rain Monday night (gotta get that roof up before snow settles in!) and got a moderately bad hit of 110. I didn't drop dead where I stood nor was I thrown off the ladder. Don't exaggerate. I did retire the extension cord, though.

You misunderstand my comment. And you misunderstand how electricity works. Had you been well grounded, you could have easily died. It only takes about 200 milliamps to kill a human.

110v/10amps is plenty to kill you. It's not the voltage that kills you, it's the amps. That is why you can touch a 20,000 volt tesla coil and barely feel a tingle.

Re: Lockout-Tagout

#105

Post by jjeaff »

6nf wrote: post #53
jjeaff wrote: post #50

Earlier quoted context omitted.

110v or 240v will kill you dead where you stand. But it's not really about the voltage. The higher the voltage, the easier it is for the electricity to ground out through you. But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps. Luckily, human skin is not highly conductive and neither are rubber soled shoes. So if you are taking proper precautions and not kneeling…

> But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps. 10-20 amps? Not across your skin! Usually a 220V zap at home won't cause instant death.

You should read the whole comment before contradicting someone. It really wasn't that long of a post.

Re: Lockout-Tagout

#106

Post by tomatotomato37 »

grawprog wrote: post #98
taneq wrote: post #28

Earlier quoted context omitted.

Honestly if our mains was 110V rather than "240V" (read 250-260V thanks to all of the rooftop solar in our area) I'd probably be a bit more casual about it. I've been nipped by ~100V from poor earthing and it's not that bad. 240V hurts.

I dunno, I got electrocuted repeatedly a few weeks ago, not sure the voltage, I was using a wet saw and didn't realize the rubber had worn out on my boots and the steel plate in the soles was touching the floor. Every time I turned the saw on or touched it when it was running I got electrocuted. It was kind of funny, nobody could figure out why i was the only one being electrocuted. All my coworkers came and touched…

I find it interesting how you describe a job with a functional safety culture from the perspective of regulators, with lockouts and random inspections, that yet solves the issue of a power tool shocking workers at mains voltage by just tossing down a rubber mat and continuing to work with said malfunctioning tool.

Re: Lockout-Tagout

#107

Post by mcguire »

taneq wrote: post #9

After working in mining for a long while, where this kind of isolation procedure is standard and is taken very seriously (pretty much any breach of procedure is an instantly firable offense) it's terrifying coming back home and seeing people working on house wiring etc. with nothing more than a turned-off circuit breaker protecting them from electrocution or other injury. I've seen some trades start to pick up isolat…

I worked on Redstone Arsenal, and although the most danger I was in was having an emacs fall on me, the monthly safety bulletins were usually about proper tagout/lockout procedure. Particularly with equipment that people have to crawl into for maintenance.

Re: Lockout-Tagout

#108

Post by mcguire »

RandomBacon wrote: post #12

Always verify the equipment you are working on is still physically LO-TO. I heard a story about one person who LO-TO a breaker on Friday, and Monday it had power when he went to work on it. The guy went to check the breaker, and the breaker was sitting on the ground with the lock still attached, and a new breaker in its place.

That was the subject of a monthly bulletin once. Reading between the lines, somebody didn't have a job the next day.

Re: Lockout-Tagout

#109

Post by taneq »

duckymcduckface wrote: post #97
ttsda wrote: post #71

Earlier quoted context omitted.

It's impossible for a 240V outlet to deliver 10A through your body. Unless you're made of metal or something.

Think the point is that the voltage won't collapse under the load.

Exactly, you can get zapped by tens of thousands of volts from a van de Graf generator and be fine, and you can die from 110V mains. The difference is the importance of the supply.

Re: Lockout-Tagout

#110

Post by MertsA »

amluto wrote: post #60
zaarn wrote: post #36

Earlier quoted context omitted.

What I learned when doing electrical work in germany, the procedure for safe electrical working is as follows: - Switch off (at circuit breaker) - Prevent switching on (lock the breaker) - Check voltage free (multimeter cleared for 230V/120V operation with long, isolated test leads) - Ground and short (put a plug into the socket connecting earth, live and neutral, you can DIY that at home safely by cutting open an un…

> Ground and short (put a plug into the socket connecting earth, live and neutral Hmm. Given that breakers in the US don’t disconnect the neutral, grounding the neutral can introduce potentially unpleasant stray currents. On the flip side, as far as I can tell, it’s entirely possible for a code-compliant installation to give you a moderate zap if you touch the neutral with the breaker off: if you have a long feeder t…

No it can't. Neutral is tied to ground at the breaker panel. So long as that breaker is turned off, and the neutral isn't accidentally being used as the neutral for another circuit, then there's zero current across the neutral wire back to the breaker panel. The only difference between neutral and ground on that circuit at that point is the color, check the resistance between neutral and ground and you'll find that they're basically a dead short.

Shorting the neutral to ground as well as hot has the benefit that under fault conditions the neutral wire can become electrically hot and if there's a miswired circuit that has current passing through it shorting it to ground would prevent a shock hazard from forming when you disconnect the neutral wire.

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