# Metallic Debris Getting into Electrical Disconnect Box.



## Wirenuting (Sep 12, 2010)

If a box has open knock-outs it’s an OSHA hit when something happens. 
It sounds like your company doesn’t employ liability lawyers.


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## Signal1 (Feb 10, 2016)

I would say your best bet is hire an electrician.

You could probably clean things up safely if you did proper shut-downs, however, an experienced electrician with all of the test equipment and safety gear would be much safer for you and your company, and also would be more likely to identify safety hazards that you may miss.

I would advise you to come up with an annual inspection program as well.


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## canbug (Dec 31, 2015)

It's not just the accumulation in the bottom of the boxes, metal dust on knife blades, fuses, anything in that disconnect can cause an arc flash, to clean these properly will require a shut down. I don't think I would even want to open a box or switch knowing the condition of the gear.
It's time to bring in someone knowledgeable, electrically, and get your worksite safe again.

Tim.


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## hotrod1442 (28 d ago)

Wirenuting said:


> If a box has open knock-outs it’s an OSHA hit when something happens.
> It sounds like your company doesn’t employ liability lawyers.


No the "knock outs" are intact/in place, just the fact that even though they haven't been removed, I believe that they are likely allowing the metallic dust thru the cracks.


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## CMP (Oct 30, 2019)

hotrod1442 said:


> I'm the Plant Maintenance Foreman (certified Millwright/General Machinist,.....but NOT an Electrician) at a large machine/millwrighting/fab shop, and have a concern related to debris that is finding its way into the interior of electrical disconnect boxes throughout the facility.
> 
> The disconnects in the machine shop/millwright shop are accumulating metal shavings & dust, and the fab shop boxes are accumulating metallic grinding dust. I would describe myself as just having enough electrical knowledge to perform basic troubleshooting around the facility to keep equipment in service. (changing out blown fuses, resetting electrical overloads, simple rewires of single, and 3 phase equipment, etc.)
> 
> ...


If you need some ammunition to use for the boss, to get the point across, have a look here.









Sparks and Arcs also (aftermath of burn to member)


Some real spark video's may make some on here work safer. If you have some post it. Cowboy Cowboy, I didn't make a video, because I was in the middle of a meltdown similar to that, but likely worse. If you want to get guys to really come to terms with the risks, seeing some after effects still...




www.electriciantalk.com





Grinding dust in a 480V disconnect at the service.


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## SWDweller (Dec 9, 2020)

Do you wear a mask at this place of employment? If metal shaving are getting inside the electrical boxes then the atmosphere has to be contaminated. 
I suggest a full face mask to protect your eyes.


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## gpop (May 14, 2018)

hotrod1442 said:


> No the "knock outs" are intact/in place, just the fact that even though they haven't been removed, I believe that they are likely allowing the metallic dust thru the cracks.



There are different grades of disconnects/boxes base on a Nema number system. Yours should have been Nema 4X but there probably Nema 1 which means they have no door seals and knockouts on top. 

Nothing much you can do other than explain the problem and hope they are willing to invest money before some one gets hurt. No one likes a safety problem being put into writing as it may come back to bite them in the arse later. So you could try a polite e-mail pointing out the problems you are seeing.


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## wcord (Jan 23, 2011)

I'm probably going to get trolled, but here goes.
Any holes/cracks (KOs or open mounting holes) could be sealed with metal duct tape, or a bead of caulking.
And then run a 1/2 wide, thin rubber or foam gasket material on the inside of the disconnect cover, to seal the door to the edge of the enclosure.
Of course, the best solution is nema 4. Even nema 3 will let in dust


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## Awg-Dawg (Jan 23, 2007)

You could always stick a couple magnets in them, it will help with metal dust. Planning a Saturday once in a while to vacuum them out doesn’t sound like a bad idea.


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## paulengr (Oct 8, 2017)

We routinely do cleaning jobs for some companies which accumulate coal, wood, or metal dusts. The first two can cause corrosion but more importantly create a dust explosion even from normal operation. Even dust/oil tight (NEMA 12) equipment is NOT impenetrable. You have to clean it, period. How often depends on the equipment and the plant. Some are worse than others. Some are annual.

Arc flash happens when the conditions are right: above about 200-300 V, especially with 3 phase or when an arc is “contained”, if the available current is high enough Current flow is normally interrupted 120 times per second (100 in 50 Hz countries) so the arc is extinguished. However if the air around the arc gets hit enough it changes to a conductor and that’s when the arc becomes self-sustaining. At that point usually the only thing stopping it is an upstream breaker or fuse, NOT the one in the disconnect. That means it is usually much bigger. Don’t think the doors will stop it either. Most electrical panels rupture at 1-2 PSI. If you have say a 20” wide and tall door that’s 400-800 pounds of pressure on the door pins which aren’t very large. The pressure buildup usually happens in about 0.01 to 0.03 seconds before the cabinet ruptures. And you may not want to stand in front of the door.

The whole key here is that unless your equipment is engineered to minimize the damage (and even then you don’t need the down time), the most effective thing you can do is minimize the risk. That means don’t just use knockout hole plugs. Use the Hoffman NEMA 4 sealed plugs. Use NEMA 12 panels, buttons, etc. Use conduit or better yet MC or TC/ER cable in tray where it can be cleaned, even washed down Panels should be vacuumed and wiped down. How often depends on your site.

I will say this too. Disconnects under ordinary maintenance will outlast just about all other equipment, even breakers. They do wear out and need replacement just like everything else.


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## splatz (May 23, 2015)

wcord said:


> I'm probably going to get trolled, but here goes.
> Any holes/cracks (KOs or open mounting holes) could be sealed with metal duct tape, or a bead of caulking.
> And then run a 1/2 wide, thin rubber or foam gasket material on the inside of the disconnect cover, to seal the door to the edge of the enclosure.
> Of course, the best solution is nema 4. Even nema 3 will let in dust


I heard it from a guy that knows a guy that if you roll a ball of duct seal into a rope like play dough, and press that into the seams and around the door, it's hack but it works pretty well. The 3M mastic tape or pads work extremely well to cover up big holes.


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