# Ground the duct work ?



## Jim West Pa (Jul 27, 2010)

I ran 4" PVC under my shop floor for dust collection from my table saw and jointer. someone said to ground this PVC.
Should I do this ? 
If so, why?
And how ?


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## woodnthings (Jan 24, 2009)

*not necessary.*

I would explain how but that would be unnecessary also..... :yes:

No need to explain how not to do something. JMO.

But if you want to know why not, there's not enough volume of dust or an ignition source. Yes, a static spark may occur but even those won't cause an explosion. There would be a whole forum devoted to dust explosions in PVC pipe if it were a real concern. Never heard of one yet in a home shop, only industrial settings with HUGE volumes of dust.


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## cabinetman (Jul 5, 2007)

Here's a good write up on static electricity.


















.


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## Jim West Pa (Jul 27, 2010)

woodnthings said:


> I would explain how but that would be unnecessary also..... :yes:
> 
> No need to explain how not to do something. JMO.
> 
> But if you want to know why not, there's not enough volume of dust or an ignition source. Yes, a static spark may occur but even those won't cause an explosion. There would be a whole forum devoted to dust explosions in PVC pipe if it were a real concern. Never heard of one yet in a home shop, only industrial settings with HUGE volumes of dust.


 Thanks dubya n T.
I do believe that I get your drift and understand what yer sayin.


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## Jim West Pa (Jul 27, 2010)

cabinetman said:


> Here's a good write up on static electricity.
> 
> 
> 
> ...


 Thanks cabnitman.


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## Brian T. (Dec 19, 2012)

Here's a good write-up, in fact two of them. Read the Prince George Citizen newspapers. No more theoretical conjecture needed.

Explain that to the families of the dead and injured at Babine Forest Products.
Explain that to the families of the dead and injured ar Lakeland Mills (about a month later.)

Friends of mine died in there.

Both mills totally exploded. The issue is what's enough and what's too little.
I refuse to believe that any dust is not enough to be concerned about. Cavalier thinking, I say.

Being a little fastidious is better than watching the roof loft off your shop house with you in the middle, yes?


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## woodnthings (Jan 24, 2009)

*home shops or industrial sites?*

I'm guessing those you mentioned were industrial sites where HUGE quantities of dust were ignited ... :blink:

Like I said, if this was an issue in home shops there would be hundreds, maybe thousands of reports of explosions in forums like this.... assuming there were survivors. I haven't seen any, but that doesn't mean there wasn't ....one?

I grounded my dust deflector/separator in the dust collector to the motor housing and mobile base since the 6" flex hose between them is not an "electrical connection" because the flex hose has a non-conductive plastic coating. The static shock I received before doing this were painful and annoying and survivable, but never an explosion hazard...JMO.


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## epicfail48 (Mar 27, 2014)

woodnthings said:


> I'm guessing those you mentioned were industrial sites where HUGE quantities of dust were ignited ... :blink:
> 
> Like I said, if this was an issue in home shops there would be hundreds, maybe thousands of reports of explosions in forums like this.... assuming there were survivors. I haven't seen any, but that doesn't mean there wasn't ....one?
> 
> I grounded my dust deflector/separator in the dust collector to the motor housing and mobile base since the 6" flex hose between them is not an "electrical connection" because the flex hose has a non-conductive plastic coating. The static shock I received before doing this were painful and annoying and survivable, but never an explosion hazard...JMO.


Industrial setting or not, recommending against a safety measure is pretty foolhardy. That's like saying "most saw accidents occur in factories so you don't need blade guards on yours". Its a pretty poor recommendation to make about any safety precaution


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## cabinetman (Jul 5, 2007)

epicfail48 said:


> Industrial setting or not, recommending against a safety measure is pretty foolhardy. That's like saying "most saw accidents occur in factories so you don't need blade guards on yours". Its a pretty poor recommendation to make about any safety precaution


+1. :yes: It is foolhearty to assume that because some events of explosion or fire due to dust haven't been made public, or may have been in local situations not widely publicized. What may be critical is that a hobbyist works in a much smaller space, and it's likely that the concentration of dust (parts per) could be greater than in an industrial setting.

As for an ignition source, whether a static charge could qualify or not, there are plenty other sources of sparking happening in the machinery in the shop. Safety can't be overlooked no matter how far fetched the conditions seem. 


















.


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## woodnthings (Jan 24, 2009)

*for the doubters and skeptics, ground away*

Quoting from the Rick Christopherson Article:

*Some Reality Checks
**Q:* Why doesn't my shop vac explode?
*A*: Because the air velocity in a shop vac is high, the static build up is also very high, and sparks happen frequently inside the hose. However, the same high velocity of the air also reduces the chance for an LEL concentration to develop within the hose. In this case, you have the ignition source, but don't have the explosive concentration.
*Q*: Why are there so few occurrences of explosions in home shops?
*A*: Home shop explosions are not impossible, but they are rare. This is because you need both an LEL concentration and an ignition source at the same time and same place. The odds are low, but not zero.




AND:
The spark that travels can either be between the negatively charged PVC and the positively charged air, or it can be from surface to surface on the PVC. Since the PVC does not conduct, it will not equalize the charge throughout the length or even diameter of the pipe. As a result, there is the potential for the spark to jump from one section of the PVC to another. *Even an internal ground wire will not prevent this, as the wire only covers a small portion of the surface.*
Read the entire article to get the whole picture: 

http://www.waterfront-woods.com/Articles/Electricity/static.htm


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## Fred Hargis (Apr 28, 2012)

Without (I hope) stepping into the debate, Woodnthings has it, grounding a home shop system is about as useless as anything you can do. It's also a PITA. It's sometimes done for personal comfort, but if your duct is underground that doesn't seem to be much of a concern. My first system was completely grounded, that quickly went by the wayside as the system evolved.


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## Miller Woodworks (Dec 11, 2013)

While I normally love things done for safety, I don't think grounding a home dust collection system is actually done to make anything safer. Safety is one of those things you can never actually achieve. There's always a way to get hurt. If having a stud in your walls every 16" makes the wall safe, wouldn't one every 8" make it twice as safe? 8" wouldn't mess up the spacing so you'd still be able to hang sheetrock and have the edges fall correctly. That would make it safer, but nobody does that. Why? Because it doesn't actually make anything safer in the real world. 

The same thing applies to home shop dust collection. Yes, grounding the PVC makes it "safer" but not in the real world. It would be cheaper to run metal ducts than to completely ground a PVC system. There's simply no real world benefit to it. If you choose to, great. Let us know how you did it, or post a build thread where we can kinda watch you do it. It'd be cool to see even though I don't think it's necessary.


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## epicfail48 (Mar 27, 2014)

Miller Woodworks said:


> While I normally love things done for safety, I don't think grounding a home dust collection system is actually done to make anything safer. Safety is one of those things you can never actually achieve. There's always a way to get hurt. If having a stud in your walls every 16" makes the wall safe, wouldn't one every 8" make it twice as safe? 8" wouldn't mess up the spacing so you'd still be able to hang sheetrock and have the edges fall correctly. That would make it safer, but nobody does that. Why? Because it doesn't actually make anything safer in the real world.
> 
> The same thing applies to home shop dust collection. Yes, grounding the PVC makes it "safer" but not in the real world. It would be cheaper to run metal ducts than to completely ground a PVC system. There's simply no real world benefit to it. If you choose to, great. Let us know how you did it, or post a build thread where we can kinda watch you do it. It'd be cool to see even though I don't think it's necessary.


Having studs at 8" would make the walls stronger due to having more potentially load bearing beams in the wall. The reason its not done that way is cost, given that spacing joists at half the distance would need twice as many. Now, if grounding the PVC makes things safer in the slightest, it is still safer. Even if there's no "real world benifit" immediately visible, you can be dang sure there is one when something doesn't blowup. Claiming"I had mine grounded and it never blew up, therefore its useless" is, in a word, stupid. 

As far as perfect safety being unachievable, its only unachievable so long as there's that one person claiming safety measures are useless. Just because nothing is 100% safe doesn't mean we should give up on safety measures


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## Fred Hargis (Apr 28, 2012)

But the truth is it takes a very high concentration of dust and other just right conditions to pose an explosion hazard.....conditions that are so unlikely in a home shop setting it borders on the odds of being hit by a meteor. Taking safe measures against something that has only infinitesimal odds of happening is as silly as not guarding against those things that are more commonplace.


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## woodnthings (Jan 24, 2009)

*do a search, you will find*

I searched "Home shop dusty explosions" and found what I had suspected or already knew from previous research and posts here on the subject:
http://www.thewoodnerd.com/articles/dustExplosion.html

Quoting from the article above:
Before getting into the details, let me set your mind at ease. There is absolutely no reasonable risk of this happening. There's not even a remote risk. It's so close to impossible that you're much better off building a large metal shield over your shop, because it's much more likely to get hit by a meteor than have a PVC-induced dust explosion. *There has never, ever been a verified PVC static-caused dust explosion in a home wood shop.* Not even one. Of course, you can't really prove anything by a lack of evidence, but the fact that we have no record of it _ever_ happening tends to back up the science of why it's not a realistic risk. So just stop worrying about it.

Quoting your post..... claiming "I had mine grounded and it never blew up, therefore its useless" is, in a word, *stupid. *Implying that anyone is stupid is not gonna impress anyone here, or prove your point, or make you any new friends and it's just not necessary or in good taste. A few of us have been around for a long time, have researched the issue and have come to our own conclusions based on the research. You have a right to your own "opinion" but you need not flame the issue. The author of the "Static" article, Rick Christopherson, is a well respected author, electronics/electrical expert and woodworker:
http://www.waterfront-woods.com/Arti...ity/static.htm


By the way, I hope for sake of consistency that your own system is properly grounded. And that you always wear safety glasses and hearing protection and a dust mask and that you always have all the proper safety equipment mounted on your power tools. Anything less would be.... well, startling!
..


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## Brian T. (Dec 19, 2012)

I think that the difference in the mills was that some dust escaped the DC system and built up, here and there. Combined with inefficient maintainence,
one bang shook the rest of it loose and kablooie.
The government safety agency upscrewed their investigation so badly that there seems no hope of any charges or court cases.

I've got all sorts of storage shelves all around in my workshop. There's a fine layer of very fine dust on everything. Possibly, I should do one wall per year.


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## Trav (May 30, 2011)

My response to this question is if you are worried about grounding a PVC pipe dust collection system then you should not use PVC but metal duct instead. 

I don't understand how running a wire down a length of PVC pipe will do anything to ground any section of the pipe that is not touching the pipe.


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## Miller Woodworks (Dec 11, 2013)

epicfail48 said:


> Having studs at 8" would make the walls stronger due to having more potentially load bearing beams in the wall. The reason its not done that way is cost, given that spacing joists at half the distance would need twice as many. Now, if grounding the PVC makes things safer in the slightest, it is still safer. Even if there's no "real world benifit" immediately visible, you can be dang sure there is one when something doesn't blowup. Claiming"I had mine grounded and it never blew up, therefore its useless" is, in a word, stupid.
> 
> As far as perfect safety being unachievable, its only unachievable so long as there's that one person claiming safety measures are useless. Just because nothing is 100% safe doesn't mean we should give up on safety measures


I'm sorry, but using cost as an excuse to not include a safety feature in your home (where you and your loved ones eat, sleep, and do pretty much everything else) is just you giving up on one safety measure while complaining that others give up on another one.

I'm not trying to get people to not use some safety feature. I'm pointing out that grounding a home PVC dust collection system isn't a safety feature. Yes, many people say it is, but those people don't have any evidence to show that it actually makes anything safer. Do you have any evidence to show that grounding a PVC system is actually safer than not doing so? Do you have a verifiable account of a home PVC dust collection system exploding?


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## walnutavenue (Nov 9, 2011)

I initially grounded only the gates on my system to avoid getting shocked each time I touch them. Then, on one very dry afternoon when I was cutting some dados the static in the pipe built up enough that it found the closest thing to ground to. What it found was my stereo.

Now all the pipe is grounded, not for my safety... but for the safety of the new stereo. All it takes is a piece of wire, some screws, and a few minutes. In the time that it takes to read just one "grounding a dust collection system" debate, you can have yours done and never look back.


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## frankp (Oct 29, 2007)

The only reason I would ever bother with it, personally, is because the occasional shocks you MIGHT get would be annoying. From a safety perspective, there is no indication I've ever found that it would be necessary.


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