Off topic but bad idea

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tomoldcars

Active member
Joined
Nov 7, 2010
Messages
36
Location
Montclair, Ca 91763 USA
Disclaimer;
This post is neither appliance nor homemaking related, but service people will understand. I found these forums while tracking down an obscure Westinghouse service tool that one of you now own. I’ve been hooked ever since. Our common trait is that we are all eclectic collectors with the desire to fix the things we collect. Many of you grew up in the service industry. I’ve enjoyed reading of the pitfalls you’ve related. I have 35 years in aerospace and industrial engineering, but this is a first. I humbly propose a toast to the insanity of the customer.

On Monday, one of my co-workers, Brian, went to a large manufacturer of plastics for the medical industry. He was to install a new Allen Bradley 300hp inverter for an extruder. It was completed Wednesday with start up yesterday. Power comes from a 480V, 3 phase, 600A disconnect breaker. It has been off and locked out for several years. The new $30K drive was initiated and power restored for the first time since the line was deactivated. The following is a third hand narrative related by the Chief Engineer / Owner of our company and corroborated by the drive I unloaded and the box of shrapnel Brian brought in. During the course of commissioning, power can be cycled several times. Each time power is shut off we physically check with a meter to confirm all is dead. Brian physically checked and two legs weren’t. He reported this to the facilities engineer and was told it was impossible, the breaker was off. Brian then put his meter across the two legs which read 470VAC. The customer dismissed it as “incidental floating voltage” and couldn’t hurt anyone. When Brian insisted that there was a real problem, the customer “proved it wasn’t” by grabbing a screwdriver and jamming it across the offending terminals. Next down the line was the 1800A sub panel feed that worked. The culmination of this early 4th is; One badly burned and, I suspect, unemployed maintenance engineer, One badly shaken but undamaged co-worker, One coffee can sized hole in a 12 gage cabinet and one $30K box of scrap. I won’t even speculate on the behavior of someone who should know better.
Tom
 
After reading this story all I can say is shocking,______ just shocking!
smiley-surprised.gif
 
BELEIVE WHAT YOUR METER TELLS you in this case-if the meter showed voltage-for you sake and anyone else working with you-beleive it-Breakers CAN AND DO fail-often closed position as you found.When working with high voltage high power equipment as you are doing a safer thing to do is interrrupt the power again from a breaker upstream of the one you are working from-then LOCK&TAG both of them OFF!!!!!We do that at the transmitter site-one transmitter is locked off now--both 4160 V breakerrs feeding it locked off-pending a replacement or rebuilt rectifier transformer for its HV supply.That maintenance man is AN IDIOT and should no longer be allowed around High current power systems!!!It is a wonder you guys weren't KILLED from his IDIOTIC actions!!!!In factI would have taken him outside and worked him over again!!!!And on our 4160V breaker at the transmitter--it is grounded-our breakers have a grounding system that can only be used when the breaker is off,and locked off.The lockout-taggout system saves lives-that is another thing that should have been used at that worksite-it is now an OSHA requirement.All persons working on the system have a key for their lock.All locks have to be unlocked and removed before the system can be activated again.Our building engineer here is doing some wiring work and the breakers to the circuits he is working on are locked out--208V three phase.
 
Well it WAS fireworks day. But geezus! How old was this guy and how did he get that old with practices like that?

I have a 'floating/phantom' policy. It's 47VAC. I don't shove a screwdriver in it, I shove a finger while meter still connected. If it really IS phantom, it drops to tenths. If it's NOT phantom, I get a harmless tingle and go looking where it's coming from.

If it's OVER 47VAC I go looking why. I've only wired 240V twice, at breaker boxes, with UTMOST caution. Anything over that, fuggit, call a union man. If HE turns out to be an idiot, at least insurance still covers the result.

I wouldn't stay in the same room with someone shorting 470V 'on speculation' that it's not really there. Those little bouncing/glowing balls of metal are somewhere around 2000F. Then there's retina damage. And I REALLY don't need PTSD from watching a human explode.
 
I WON'T touch ANY wiring until it is safe and----GROUNDED!!!!Esp at where I work.Fingers and other body parts should NEVER contact conductors until they have been proven safe to touch.Remember the old radiomans saying---"Better a dead circuit than a dead operator!"
In some cases while or tripping-closing breakers-you will need to wear a flash suit-this protects your skin and eyes from the heat,and powerful UV radiation that results from arc flashes.Arc flashes can be explosive as Frigiluxes video link shows.When the new Powell Electric switchgear was installed at our plant-they showed that video and another one involving a strip of 12Ga copper wire 6 in long shorting the 240V terminals of a 50Kva "pole" transformer.The wire was placed in a junk car and the transformer primary pulsed with its rated 13Kv primary voltage-that car was DESTROYED from the blast of that little peice of wire.Other videos they showed were the testing of their breaker enclosures-in some of the extreme testing-the enclosure panels actually buckled under the extreme currents.So they go to heavier guage metal.And the 4160V(5Kv rating)switchgear cabinets here the doors are like bank vaults-they are strong enough to withstand rupture forces if a breakers fails.I still stand to the side while tripping the breaker open or closed.Remote trips breakers are best-that way you are totally isolated.On YouTube there is a video of a worker tripping a 4160V breaker and it failed-the blast blew him out of camera sight!Don't know if he survived.Its really rare when a stored energy breaker fails--but when it does-the results are REALLY bad!!
 
Yes,know about the explosive fuses-they use the explosive to destroy the fuse element to prevent arcing over the fuse.They are used in circcuits 33Kv and over mostly.Lower voltage fuses have elements that burn completly when blown-have some here-in the 4160V fuses in the transmitters.These can be rebuilt-have replacement elements here.Have rebuilt a couple.You have to pull against a very strong spring when installing the elements.The spring then pulls the fuse wire away when blown.Haven't blown one of these in a while-they are for 400A.One blew years ago from a shorted transformer in one of Continental transmitters.
 

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