Safety reminder

matthewsx

matthewsx

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At work lately I’ve been doing a bunch of moves on machines that run on 480 3 phase. We’re consolidating facilities and as maintenance and facilities manager it’s my role to get things like these discharge machines wired up.

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My rules is I only work on wiring after the safety disconnect so I can do proper LOTO. Mostly I can do this but occasionally I run into machines that are wired directly to the breaker and have to be extra careful.

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I’ve explained to my guys what the big 2x4 is for if something goes wrong but mostly I’m confident in my abilities to do this work safely.

Well, day before yesterday we were wrapping up a meeting and the lights started flickering and some outlets went dead. It didn’t take me long to figure out we’d lost one leg of the incoming 3 phase.

I don’t have a picture of it on the pole but this is what happened.

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This crow managed to fry itself between conductors.

Be safe out there, high voltage can kill instantly.

John
 
matthewsx said:
My rules is I only work on wiring after the safety disconnect so I can do proper LOTO. Mostly I can do this but occasionally I run into machines that are wired directly to the breaker and have to be extra careful.


John
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Agree 1000% about LOTO for all hazardous systems; don’t industrial breakers have capability of being locked open?
 
ChazzC said:
Agree 1000% about LOTO for all hazardous systems; don’t industrial breakers have capability of being locked open?
Click to expand...
Not the ones this equipment is wired to. If I had the key to the panel cabinet I could lock it but the building is probably 40 years old, I’ll need to order some additional. LOTO
 
matthewsx said:
Not the ones this equipment is wired to. If I had the key to the panel cabinet I could lock it but the building is probably 40 years old, I’ll need to order some additional. LOTO
Click to expand...
Maybe have someone man the breaker panel to prevent someone from turning the breaker back on while the work is being performed if there is no way to lock out the breaker.

480vac is nothing to be cavalier about. Lock Out Tag Out is a must.

I've seen and heard (loud like a shot gun, complete with ringing ears afterward) first hand what 480 vac can do.
Small VFD's seem to be more explosive than larger 40hp units are in catastrophic failure mode.
Many years ago, I had a main disconnect blow up. An electrician left a skinned piece of #14 wire laying across the L1 and L2 lugs. Of course I had the floor cabinet doors all closed and latched when energizing the machine for the first time.

I've seen a lot of people just pull the interlock lever down and push the disconnect lever up without having the door closed. Because, it is so hard the close an latch the door an then use a screw driver to unlatch the door after energizing the machine... laziness can get you killed. I wish videos of arc-flash accidents were available back then.

Here are some I just found that, I think if were viewed, no one would energize a machine with the door open. This was one of my pet peeves back in the day. Luckily, no one I worked with ever had a bad accident.





One of my favorite videos. Not arc flash. Just high voltage.

 
Fortunately there’s nobody else that would likely be flipping breakers in our facility. Nevertheless I did keep a close eye on the door to the electrical room when I had to disconnect the machine with no safety disconnect.

I’ll be removing some unused wiring on the line we’re moving tomorrow. I’ve enlisted assistance from the licensed electrician we have on staff (not his actual job) to help with that one since it’ll involve work past the disconnects.

John
 
20 plus years in the mobile equipment drilling industry and I’ve seen several small and large shorts. I’m still here safe and sound. Take the right steps and you can minimize events. That’s how we used to operate now. We do everything we can to make sure people don’t get hurt. Doing qa qc I once had a 225kva transformer fail next to me. Scared the **** out of me, but I was not hurt. I was out of the way, covers were on and I was wearing ppe including full fr. Now we have cal suits. We are learning. Half of all my first year apprentices have taken a good poke, so we are not there yet but we are moving forward.

When I mention we, I mean the electrical industry. I no longer work in the field after 30 years I took a job as an instructor. Only regret is that I didn’t do it sooner.

Be safe, take the time that’s needed to do the job right. A lot of deaths come down to either time or money, or both.
 
I have worked with power systems from, 5 VDC to 34,000 VAC, for years and have a lot of respect for what can happen. The worst I can remember was a new installation of an 800 HP 7200 VACcompressor that had shorted winding. When we bumped the starter to check the rotation fire erupted from the pecker head and I was standing just below. It singed hy hard hat. The fun times were at McGraw Power Systems R & D we had a lab that could create lightning. We often caught a rat, suspended it by its tail 2 or 3 feet from the ground plate, and hit it with a lightning bolt. only found a few hairs once the smoke cleared. FUN times, Back in the days.
 
Not only will high voltage kill you very quickly, but it will hurt you all the time it is killing you. Probably like getting eaten by a lion.
 
I guess I don't fully understand what causes arc flash. Does this happen when there is a physical short between two conductors (or one and ground?). What usually causes this in practice? Is this a risk on standard 240 VAC panels?

Edit:
This video answers a lot:
 
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