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 Post subject: PPE For greater than HRC 4
PostPosted: Wed Aug 19, 2009 8:52 pm 
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Joined: Wed Oct 29, 2008 6:05 am
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Some of our equipment requires PPE greater than HRC 4. We will not work on any of this equipment live but we will need to verify zero voltage on this equipment. What PPE is required when verifing zero voltage on systems where the HRC is greater than 4?? This is at various voltage levels 460V, 5KV, and 13KV.

Thanks In advance.


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PostPosted: Wed Aug 19, 2009 10:25 pm 
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Joined: Sun Aug 16, 2009 8:42 am
Posts: 184
Location: Lawrenceburg KY
Great question. I seen one thread were you may use a voltage detector on a hot stick to increase the distance. This seems possible but maybe not feasable. I would look at installing some type of voltage meter tapped off with a small fuse for protection. But if you equipment runs 24/7 that also may not be feasable. Look at this article. I have some warning lamps like this in equipment. Not sure about the higher voltage. Maybe these people at graceport could tell you.
http://ehstoday.com/safety/electrical/ehs_imp_36894/
http://www.graceport.com/


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PostPosted: Thu Aug 20, 2009 4:51 am 
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Location: North Florida
One option is to move upstream of the equipment to a point of lower IE and clear it there. Then you have eliminated the risk of operating the equipment with such a high rating. Since the sources of energy have been removed, verified and locked out upstream you can open and verify the equipment to be worked on safely. This is what we do for some equipment that has a long clearing time due to transformer impedence and cable lengths with very high incident energy. Just don't fool with it is the safe way to go. Operations hates it but we don't give them a choice.

TxEngr


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PostPosted: Thu Aug 20, 2009 6:25 am 
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Permanently mounted meters/indicators cannot work with the test the circuit, verify the tester, test the circuit rule.

PPE above HRC4 is available. The common argument against is that it offers insufficient protection from the blast. If your high IE is due to long clearing times, you do not have the blast hazzard.


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PostPosted: Tue Aug 25, 2009 1:17 pm 
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Location: Louisville, KY
Hrc 4

Really HRC 4 is >40 cal. It doesn't have a top.

However if you have > HRC 4 you have done calculations so the HRC's no longer apply. You can use them for reference but you have to match the hazard to the protection. I agree with Steve that you may NOT have a blast issue but this isn't definitive at any specific level. The studies on blast tell us one thing. It is worse as the clearing time goes up but the size of the "box" also affects this. No easy answer. I have found in testing. 10kA isn't too horrible. 20kA can throw a meter about 31 feet AFTER hitting the worker/mannequin.

You have to do voltage testing and often grounding no matter what but the risk when you are truly following an "electrical safe work condition" policy is reduced. Get the PPE as close as you can.

Hugh


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