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Have you seen equipment where there is evidence of impending failure?
Yes 83%  83%  [ 43 ]
No 17%  17%  [ 9 ]
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Total votes : 52
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ekstra   ara
 Post subject: Evidence of Impending Failure
PostPosted: Sun Oct 08, 2017 12:45 pm 
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Location: Scottsdale, Arizona
NFPA 70E permits “normal operation” of electric equipment if specific conditions are satisfied such as the equipment is properly installed, properly maintained etc. One of these conditions is “There is no evidence of impending failure”

Although this could be quite subjective, have you seen equipment where there is evidence of impending failure? What was the evidence?

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 Post subject: Re: Evidence of Impending Failure
PostPosted: Mon Oct 09, 2017 2:43 am 
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Location: Rutland, VT
When we do data collection, we offer an infrared option since we have the equipment covers off, that is an opportune time to scan connections. For many companies this is the first IR scan ever done and we have found overheated connections.

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Barry Donovan, P.E.
www.workplacesafetysolutions.com


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 Post subject: Re: Evidence of Impending Failure
PostPosted: Mon Oct 09, 2017 7:39 pm 
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Determining if the condition of a device is evidence of impending failure is pretty subjective. First, if you've been around a while, you likely know that certain manufacturers have produced equipment that, given enough time, will fail. Where as, under identical conditions, other brands will operate for years without any issues. Much like when consumer reports does research on how well certain cars do over time. You'll often see the same issues with a particular brand and model. Same thing applies here.

We see issues with line side contacts heating. Heating so much that the fuse eventually melts and trips. This mainly is with disconnects installed in distribution sections. Here's where shutting off the gear to remove the defective switch becomes critical. One manufacturer has disconnects that stab onto bus. So it's pretty easy to just jerk the disconnect out and install a replacement. However, if the switch has been very hot, the insulators that support the bus connections may be damaged. Removing a disconnect with damaged insulators (with the power left on) is inviting an arc flash and shock accident. Years ago, we'd do this without shutting off power, that's no longer acceptable or allowed.

With the advent of the new fuses and reduction in physical size, some manufacturers have reduced the physical size of their disconnect switches. With that change we've seen an increase in fuses melting and tripping due to heat. Here's an example, a 400 amp disconnect might carry up to 250 amps without much if any off time to cool. The smaller disconnects ability to reject heat has been compromised by the reduction in surface area and mass. Eventually, so much heat builds up that a fuse trips. Even though the disconnect is not overloaded, it still trips a fuse. In an effort to address this, one manufacturer puts heat sinks on the line side of each fuse. This same manufacture added vents to the door. That helped, but in areas where the weather is hot, like in the southwest, we still see fuses trip because the disconnect cannot reject heat fast enough.

We see cases where maintenance is either minimal or worse, non existent. Opening gear that's not been shut down and cleaned in 20 years or more can be dicey at best. Is that evidence of impeding failure? Probably not, but it sure increases the odds of failure. We've had cases where bolt lock switches would not open. So, the failure only happened when the switch was called on to open during a ground fault and failed to operate. Yet pointing out the warning label on any bolt lock switch about the necessary maintenance seems a waste of breath We've done that again and again, but convincing owners to do regular PM doesn't work unless theire's been a failure.


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 Post subject: Re: Evidence of Impending Failure
PostPosted: Tue Oct 10, 2017 5:18 am 
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I guess those only doing new construction inspections might never see "evidence of impending failure"...that or if you are blind. I get called on troubleshooting all the time and let me just say that it almost gets routine to automatically give every piece of equipment the "evil eye" looking for trouble. I'm always on the lookout for wires that were never trimmed to size and hanging out and getting pinched in doors, signs of liquid stains, linkages that aren't correct anymore, black/brown/discolored spots of any kind, wiring that is corroded and about to pull loose, broken handles where its been forced so many times that it's been twisted, etc. Missing guards, disabled interlocks, all kinds of bypasses. The signs are all there. The really shocking part is that 70E contains such trivial language "signs of impending failure". It's pretty simple to do. It can be a simple list of examples similar to how NEC describes where arc flash stickers should be. Start with "a tripped fuse or breaker"...

The "fun" ones are when I come up on site and take one look at the situation and immediately go back to the truck to "gear up" and take every single step very carefully with flashlight and meters in hand to attempt to discern just what is going on, step by painstaking step, securing everything against just about anything that can happen. It's the time when I "pucker up" and treat everything as suspect. Anyone who has been there and knows that knot in your stomach feeling that says that this could be a very, very bad day knows exactly what I'm talking about.

So I'm kind of surprised at the "no" answers on the survey. Most be office workers.


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