This article was posted 04/29/2011 and is most likely outdated.

Burn up the Myth: Hinged Door Protection
 

 

Topic - Safety
Subject - Burn up the Myth: Hinged Door Protection

April 29, 2011
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Burn Up the Myth: Hinged Door Protection

Submitted by: Hugh Hoagland

e-Hazard One Hand Arc Flash RuleQuestion: A trainer told us that we should always stand on the hinged side of the door when operating equipment even if it means reaching across the equipment.  Is this the best practice?

Answer: Probably not.  Our training has included, since the beginning, a slide we have called the "One-Hand Rule".  It is an adaptation of the "Left Hand Rule" that has been taught for years.  Here is the slide we use.

I have been confronted that this is wrong by many trainers and consultants, so we decided to test the theory at Kinectrics lab last month during the IEEE-ESW Tour.  We placed a 100 Amp disconnect on the vault wall and produced a 10kA and a 20kA phase-to-phase fault inside them.  I purchased eight since I was confident they would fail.  The disconnects were rated for 10-200kA depending on fuse type but most folks don't know this is for "bolted fault" not arc fault. 

The arcing faults will almost always blow off the door especially if they go phase-to phase. Standing to the side is the most important thing. When the mannequin was standing in the position illustrated above, no t-shirts ignited and they would have been relatively unharmed in NFPA 70E compliant HRC 2 gear.  When the mannequin stood in front it was disastrous see our NFPA 70E arc flash training video. When the mannequin stands to the hinged side with the arm across the door, the arm broke off and hit the concrete wall 6 feet away and bounced back several feet away.  The biceps of the fiberglass arm can be seen at the mannequin's feet.
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Note: I'm sure in some lower level arc flashes doors have protected folks (we often see this in switchgear) but when the door fails it is your worst enemy.  Stand to the side and allow the door to protect the area. In our collective experience, doors do great UNLESS they come off.  When they come off, it is almost always straight out just like the video test. 
This testing was done by causing a phase-to-phase fault with a wire (difficult in real life but they do happen) and with >480V to help arc sustain.  <480V arcs are difficult to sustain in real life BUT they will sustain when they go three phase, so to eliminate chance in the testing we used overvoltage of about 1000V to assure the arc would last for the whole test.

Hugh Hoagland
http://www.e-hazard.com/

 

 

 

 

 

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Comments
  • I know this is a simulation but before I turn breakers on I use my meter to eliminate the odds of the occurance. Get in the habbit, learn what to look for. When entergizing panel boards, turn them all off and turn them on one at a time after you reentergized it. I was a little confused about the left hand rule, I though it was so you didn't blow your good arm off!

    perry vogler  May 1 2011, 8:07 am EDT
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  • P.S. Wear your FR and other PPE!!!

    Bill Clapp  April 30 2011, 6:36 pm EDT
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  • I tend to agree in most situations but there will be exceptions to the basic rule you have given. On large switch gear, standing to the side may put you in line with the escaping energy. I know of a couple of arc incidents with medium voltage breakers where the individual racking the breaker was directly in front when the breaker blew up and the blast went out each side and out the top and the body of the breaker protected the individual walked away with no marks on them. Of course this was with the door open because the gear was older and could not be close to rack. I always encourage the people I train to 1. Know where the point of egress is 2. Ensure that the path of egress is clear. 3. Make sure someone is aware of what you are doing and where you are. 4 Ensure an arc/flash boundary and/or a shock boundary has been established and is clear of personnel 5. Inspect the hinges and latches and secure if necessary. 6 If possible use a tool to switch. 7.Take a deep breath and hold 8. Switch and step toward the exit..As a foot note if a person is wearing the flipdown arc face shield you may not want to turn your head away which is difficult to do after years of doing is by habit but the face shield offers a lot of protection when facing but not much if turned away. In my opinion getting to the exit without crossing in front of the exploding gear is probably my first priority and saving my arm may be second but each situation may be slightly different. Using your rules as basic and modifying them to fit the situation and gear may be a good way to get to a retirement age. Thanks for an awesome demo.

    Bill Clapp  April 30 2011, 6:33 pm EDT
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  • As an electrically Qualified person, you must make the decision as to where to stand. Think about egress, where you feel you will be most protected in an equipment failure.

    Rick Simpson  April 30 2011, 9:30 am EDT
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