# The blow myth



## Flyingsod (Jul 11, 2013)

My boss wanted me to blow out an MCC. I asked when it could be shut down and was told no, do it hot. It’s in a saw mill and the dust in there is very fine. Def could be explosive dust if stirred up just right. It’s prolly really dry dust so may not be conductive. I will not take the chance. He said it was a myth that blowing dust into electrical apparatus could be dangerous. 

It’s all good, he’s not a jerk and said he will blow it out himself. So my question to yawl is this: have you ever actually witnessed an occurrence or the aftermath of an occurrence for yourself. Hearing about one doesn’t count unless you are somehow very close to the source. Thanks

Also I’d be happy to hear others thoughts on the matter either pro or con. 

Thanks for your time. 


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## CoolWill (Jan 5, 2019)

I 100% know that dust is explosive, having been in a dust explosion myself. However, that incident had an ignition source. I don't think you would have a problem, but it's good to be on the safe side.


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## Bird dog (Oct 27, 2015)

A hazardous location?...

Class II *locations* are those in which combustible dust may be found. Class III *locations* are those which are *hazardous* because of the presence of easily ignitable fibers or flyings.
https://literature.rockwellautomation.com/idc/groups/literature/documents/wp/800-wp003_-en-p.pdf


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## just the cowboy (Sep 4, 2013)

Dust +air+ ignition source = flash.
Dust is dry as per you.
Air is supplied by blowing out panel
Ignition source is the question? A MCC in a sawmill probably has large contacts for motors that can arc when stopping or starting that would be my maybe it could happen.

Take a handful of baking flour and throw it into a campfires flame hard so it spreads out and watch the flash. 

Good job being safe, to bad the boss won't listen

Cowboy


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## Kevin (Feb 14, 2017)

Can't static electricity build up from compressed air moving over a surface?

I would use my right to refuse unsafe work there in a heart beat... the MCC should be shut down to work in it regardless of the dust... but that's just me...

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## canbug (Dec 31, 2015)

Hate to say it because I've used compressed air before on smaller pieces of equipment but a vacuum is the way to go. Use it to get all you can and then blow out the tight areas and suck that up too.


Tim.


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## splatz (May 23, 2015)

Some get confused because, why doesn't road dust explode? It's not combustible material like flour or wood dust. 

Training video (animated, no actual footage) 






Lab Demo: 






Fairly convincing: 

https://www.youtube.com/watch?time_continue=44&v=4hS6IGO2tdA


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## 460 Delta (May 9, 2018)

I’m with cowboy, open up the contacts on the motor that runs the headsaw when they hang it in a log, and you have ignition Houston.


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## Going_Commando (Oct 1, 2011)

It's scary how much Nema 1 gear is in sawmills.


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## flyboy (Jun 13, 2011)

I thought this was going to be a thread about cocaine.


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## TheLivingBubba (Jul 23, 2015)

flyboy said:


> I thought this was going to be a thread about cocaine.



Same here! Was told a story about a guy in the 80's who in his front shirt pocket use to keep a piece of copper tubing, the kind used to connect fridge ice makers full of cocaine and he'd take sniffs throughout the day.


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## emtnut (Mar 1, 2015)

flyboy said:


> I thought this was going to be a thread about cocaine.


Me too. Disappointed in this thread , and the strippers thread too :vs_mad:


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## flyboy (Jun 13, 2011)

emtnut said:


> Me too. Disappointed in this thread , and the strippers thread too :vs_mad:


Especially the strippers thread. :devil3:


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## emtnut (Mar 1, 2015)

flyboy said:


> Especially the strippers thread. :devil3:


I really expected more from Sabrina lain:


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## Flyingsod (Jul 11, 2013)

Thanks for your thoughts on the subject. 


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## Flyingsod (Jul 11, 2013)

splatz said:


> Some get confused because, why doesn't road dust explode? It's not combustible material like flour or wood dust.
> 
> Training video (animated, no actual footage)
> 
> ]


 Thanks for taking the time to find those. I never even considered looking for. Vids




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## Flyingsod (Jul 11, 2013)

just a cowboy said:


> Dust +air+ ignition source = flash.
> Dust is dry as per you.
> Air is supplied by blowing out panel
> Ignition source is the question? A MCC in a sawmill probably has large contacts for motors that can arc when stopping or starting that would be my maybe it could happen.
> ...


Thanks for mentioning that. I was more concerned with possible shorting of the bus’s bars through dust piling up on them. I hadn’t considered the much more likely contacts as source of ignition. 




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## emtnut (Mar 1, 2015)

Flyingsod said:


> Thanks for your thoughts on the subject.
> 
> 
> Sent from my iPhone using Tapatalk


fwiw, I wouldn't do it live. Most MCCs are 600V here, assuming yours is 480.

If you have the door open live, you'd have to have arc flash data and appropriate PPE.

Edit: The PPE limits the injury to second degree burns !


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## Bird dog (Oct 27, 2015)

emtnut said:


> fwiw, I wouldn't do it live. Most MCCs are 600V here, assuming yours is 480.
> 
> If you have the door open live, you'd have to have arc flash data and appropriate PPE.
> 
> Edit: The PPE limits the injury to second degree burns !


Second degree burns are blisters. Imagine someone having sunburn so bad they got blisters from it.


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## Bird dog (Oct 27, 2015)

*Inferno: Dust Explosion at Imperial Sugar*


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## circuitman1 (Mar 14, 2013)

if this doesn't wake someone up nothing will.a friend works at a feed mill.luckily he wasn't there that day because he was sick,there was an explosion right where he would have been possibly killing him.his boss was near by when it happened and was severley burned but was ok after several weeks. i would give my boss my tools if he told me to do it, my life is more important. :vs_mad::vs_mad::vs_mad:


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## emtnut (Mar 1, 2015)

Bird dog said:


> Second degree burns are blisters. Imagine someone having sunburn so bad they got blisters from it.


Yep ! Scary huh !

De-energize and have PPE is the way to go home at night, without the free suntan :biggrin:


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## nrp3 (Jan 24, 2009)

Is a few hours of after hours overtime that costly?


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## TGGT (Oct 28, 2012)

nrp3 said:


> Is a few hours of after hours overtime that costly?


Should be costly for the customer and $$$ for the owner.

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## nrp3 (Jan 24, 2009)

TGGT said:


> Should be costly for the customer and $$$ for the owner.
> 
> Sent from my SM-G930T using Tapatalk



A lot less costly than a blow up and resulting injuries. Never having done this, how long does it take?


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## Flyingsod (Jul 11, 2013)

nrp3 said:


> A lot less costly than a blow up and resulting injuries. Never having done this, how long does it take?




It’s very dependent on circumstances. In THIS case it’s a smallish mcc with only loose dust in it. To blow it out would take 20 mins tops including getting the covers off. I’ve cleaned some in the past that took a crew of four all weekend. That was a plant that vulcanized rubber though and the carbon in the gear was thick and sticky. 


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## Flyingsod (Jul 11, 2013)

I’m very pleased that no one has said they would go ahead and do it. I’m glad you are all working safely. 


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## LARMGUY (Aug 22, 2010)

Ainnofrikkinway. Shut it down. Don your PPE. Work safe.

*PERIOD!*


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## splatz (May 23, 2015)

canbug said:


> Hate to say it because I've used compressed air before on smaller pieces of equipment but *a vacuum is the way to go*. Use it to get all you can and then blow out the tight areas and suck that up too.
> 
> 
> Tim.


I get in arguments about this all the time. It's much more fun blowing things out with compressed air but you have little control where the dust goes. The compressed air generates a lot of force and I am sure it blows dust in areas that it wouldn't normally get.


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## gpop (May 14, 2018)

Ive been in a dust fire at ground zero and it wasn't that bad. The difference between that event and one in a mcc is compression. 

In a skirted building (roof and small side walls that do not go to the floor) the flash off rapidly moves away from ground zero and vents rather dramatically outside as it has gained fuel on the way. The most memorable part was how the building went from dusty to clear as a bell in a instant. 

Now if you work in feed-mills you will have seen blow out panels because a uncompressed dust ignition is a rapidly moving fire verses a compressed event which is a massive explosion. 

In a enclosed mcc i wouldn't take the risk as compressed air may contain water vapor, you also may have drill shavings that are about to be blown around in places that could cause expensive problems and finally the room would cause compression as the door is not large enough to vent that much energy.


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## Cow (Jan 16, 2008)

We've blown out mcc's before, but always de-energized.

How are you supposed to get the metal air nozzle back in there to blow out around and behind the components and whatnot with all the live terminals?

If someone is just figuring on opening the mcc bucket door and pointing the nozzle straight in from outside the mcc enclosure, that sounds like a fairly half ass way to blow mcc buckets out. 

Different strokes, I suppose...


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## manchestersparky (Mar 25, 2007)

Google Domino Sugar explosion in Baltimore. That was a dust explosion and it damaged multiple floors of the building. Don't let someone tell you its only dust !


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