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 Post subject: Fuse installation and removing
PostPosted: Mon May 16, 2011 9:25 am 
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Another question that came up by my electricans was: Are we allowed to use fuse handling equipment to install and remove fuses when live? I believe they must de-energize unless greater hazard, infeasible, or less than 50 volts. Am I correct?

I noticed OSHA says the following:

1910.33(a)(1)
"Deenergized parts." Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Live parts that operate at less than 50 volts to ground need not be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.

1910.335(a)(2)(i)(A)

Fuse handling equipment, insulated for the circuit voltage, shall be used to remove or install fuses when the fuse terminals are energized.


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PostPosted: Tue Jun 07, 2011 7:41 pm 
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unfortunately

I have to agree with you. This is an area where I do believe things may have gone a little to far. Convincing the powers that be of that is the problem. Good luck.


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PostPosted: Wed Jun 08, 2011 7:12 am 
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Don't fully understand the question.

Are you asking about replacing fuses, out and into fuse clips that are energized?
Or, are you asking about a fused disconnect switch, where you open the upstream switch so the fuse clips are de-energized, but the line side of the switch is exposed and energized.


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PostPosted: Wed Jun 08, 2011 8:46 am 
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Good question, and one that will be debated I am sure. I think using insulated fuse pullers rated for the voltages present is allowable if wearing the prper PPE per the label or tables.

THe debatable part I think is if an EEWP is required or not, if it were me, I would have a standing EEWP for this task.

Let the games begin :)


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PostPosted: Wed Jun 08, 2011 9:25 am 
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Zog wrote:
Good question, and one that will be debated I am sure. I think using insulated fuse pullers rated for the voltages present is allowable if wearing the prper PPE per the label or tables.

THe debatable part I think is if an EEWP is required or not, if it were me, I would have a standing EEWP for this task.

Let the games begin :)


Hmm.. Next week's "Question of the Week?"

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PostPosted: Wed Jun 08, 2011 10:44 am 
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It's a great question. I've been asked this in the context of replacing Class "L" fuses in a bolted pressure switch. The switch would be open, so the fuse terminals would be deenergized.

These fuses bolt on, so there is a little more work required than just sliding the fuses in and out of clips. They are accessed through a door. Although the fuse compartment isn't "hermetically sealed", I think someone would have to try pretty hard to access the line side of the switch.

Is this considered interaction with equipment?

On occasion, I come across inverted switches where switch line side is on the bottom and something dropped into the switch would be a problem.


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PostPosted: Wed Jun 08, 2011 11:57 am 
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Fuse Pullers

I believe you are correct; they must de-energize unless justified (greater hazard, infeasibility or less than 50V) and even though the live work is justified, an Energized Electrical Work Permit should be required - NFPA-70E 130.1(B). If this is frequent task, I think a standing permit would suffice.


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PostPosted: Wed Jun 08, 2011 9:04 pm 
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Personally I would have it de-energized then replace the fuse AFTER I found out why it failed.. Not troubleshooting and blindly replacing it could lead to another one failing in my fuse pullers...
Plus with the fuse blown, whatever the equipment is won't running anyway, so shutting it down shouldn't be an issue.


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PostPosted: Thu Jun 09, 2011 6:37 am 
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glen1971 wrote:
Personally I would have it de-energized then replace the fuse AFTER I found out why it failed.. Not troubleshooting and blindly replacing it could lead to another one failing in my fuse pullers...
Plus with the fuse blown, whatever the equipment is won't running anyway, so shutting it down shouldn't be an issue.


Excellent point Glen, I was thinking of removing and replacing fuses as maybe part of a LOTO process, but when you are replacing a blown fuse without knowing what caused the fuse to blow that changes things (No idea why I was thinking the way I was).

OSHA 1910.334(b)(2)"Reclosing circuits after protective device operation." After a circuit is deenergized by a circuit protective device, the circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized. The repetitive manual reclosing of circuit breakers or reenergizing circuits through replaced fuses is prohibited.

Note: When it can be determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, no examination of the circuit or connected equipment is needed before the circuit is reenergized.


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PostPosted: Thu Jun 09, 2011 8:28 am 
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How much danger

exists in changing these fuses?


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PostPosted: Thu Jun 09, 2011 8:53 am 
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100questions wrote:
exists in changing these fuses?


With the switch off? Not much, but technically you are still working inside the AFB and need PPE. The real danger exists in closing that switch after the fuse replacement if the reason the fuses blew is not known or has been fixed.


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