Dust Collectors...

[Astriapo]

I bought a dust collector tonight. What is the idea behind grounding the hose? I assume to reduce friction. So do I connect it to a pipe and hook it to the tool itself or what?

Thanks...

[Vic Baron]

Gee - I'm really sorry you asked that question. Prepare for a lot of pro's and cons. For in depth information, search for info. Otherwise, *some* people content that static electricity could generate a spark which will ignite the dust in the hoses and start a fire in your workshop. Others quickly point out that there is NOT ONE documented case of this happening in a home workshop. Dust explosions in a commercial environment are another matter but still not relative to the dust collector and static electricity.

If you want to do it, run a copper wire through the hoses and ground them. I did it that way and it was a real PITA. When I moved and redid the system, I did not ground the hoses/pipes.

IMHO, ignore the grounding - it really falls under the urban legend heading.

Vic

[marks542004]

If you are using plastic pipes the idea is to eliminate static buildup caused by the material in the pipe rubbing on the walls.

It should be sufficient to ground the hose clamp at the dust collecor end. If the hose attachment is metal and in contact with the blower motor housing it is likely to be grounded already.

A simple check is to run the system and suck up a bunch of dust, then touch the hoses while in your stocking feet. If you don't get a jolt you can probably leave it alone.

[Buster]

You'd be surprised how much static is built up on the system. If you're moving it around the shop at all you'll want to ground it so you don't get shocked every time you touch it... and continuously while your touching it.

As the other reply points out people worry about dust explosions and such, I agree with him I don't think it's a real danger.

[bridger]

please be careful to properly ground the system. instructions are at:

[Lobby Dosser]

I want to see the Video of freehand panel routing on a table mounted router.

[Tom Woodman]

If you don't think you have a static problem in your workshop... what do you think is holding all that dust on the walls? HOWEVER... having said that, getting a dust cloud to explode in a home workshop environment is next to impossible. I agree with Vic. I went to all the bother of running a ground wire through an extensive duct system. I dont think I would do it a second time. Tom

[Astriapo]

I could probably do that... Isn't the wheel on top of the bit there so your wood can use it at a guide. Plunge in and push forward...

[George]

Of course, grounding non-conducting material is a bit iffy. If don't want to get shocked, you should be "grounding" the outside.

Now metal ducts and the odd woodscrew represent a real sparking danger.

[Jim Weisgram]

[...snip...]

[...snip...]

FWIW, I do recall seeing a mention of this in Sandor N.'s book on dust collection a few years back. He stated in that edition that insurance companies said they have documented evidence this does happen. Whether you believe that or not, it might be wise to be sure you don't do something the insurance companies can use to avoid paying out on a claim.

There's a new edition of that book out, I guess. I wonder what he says now?

Anyway, on Bill Pentz web site on dust collection

I believe he says something about using metallic tape for grounding as being easier than wire.

[Wes Stewart]

The incorrect idea is that by "grounding" the plastic piping, static charge can be eliminated.

When two things in contact with each other are separated, electrons can be stripped from one of them and deposited on the other. In this case, the objects are 1) the piping and 2) air/dust. If either or both of the objects are insulators then the resulting electrical charges have no place to go and thus remain in place, i.e. they are "static."

If the process is continous, as it is when air/dust is flowing through the piping, the charges continue to build. They cannot build without limit however because there is no perfect insulator so when the potential difference (voltage) becomes high enough the insulative properties will be overcome and the charge will discharge. This can happen rapidly, via a spark (think lightning) or more likely, by gradual discharge.

The myth in woodworking is that "ungrounded" piping will generate static charge buildup sufficient to create a spark inside the piping that will ignite the combustible dust. There is no documented evidence of this ever happening.

Furthermore, even if there was, there is no way to "ground" an insulator. It's an "insulator", by definition a poor conductor of electricity, and attaching a wire to it, or running a wire through it cannot prevent the buildup of charge in areas not directly in contact with the wire. The best this wire can do is to insure that the equipment at each end is at the same potential, something that should already be the case due to the equipment-grounding conductor in the power wiring.

Can you be shocked by static charge buildup in your shop? Sure. I'm in AZ where the RH can be under 10% and dry air is a better insulator than damp air. If I'm wearing rubber soled shoes and vacuum up a large volume of dust, using my all-plastic (double insulated) vac, the vacuum and I get charged up. If I then touch the metal frame of a piece of grounded equipment I will get a shock. There might even be a tiny spark. Does anyone think that this spark will ignite the dust in the air and burn down my garage?

If I turn off the vacuum and wait just a few seconds, I can touch the grounded equipment and not be shocked. This shows that the insulators are not perfect and that the charge is slowly dissipated. Note that this is a continuous process, which is why you don't get shocked every time you run a vacuum; if the charge buildup is small, for example when you're not sucking up sawdust, but just air, the charge is dissipating as fast as it is generated.

Tip: If possible (and I remember to do it) I just keep one hand on a piece of grounded equipment when I suck up a pile of stuff. Absent that, I bend over and touch the concrete floor with a bare hand before touching anything else. This dissipates the charge slowly and painlessly.

[Mike Berger]

[joe2]

Spider webs. :)

[Joseph Connors]

In order for an explosion from a static electric discharge to ignite sawdust in the air, the concentration in the air would need to be on the order of not being able to see your hand in front of your face! It is not possible to have that concentration of sawdust in the air and still be breathing.

I have no personal experience, this is according to everything I've ever read on the subject. Grain explosions occur in very confined areas in silos with very high concentrations of dust, to a degree simply not possible in a shop (commercial or hobby).

Mike Berger wrote:

[bridger]

if you have evidence of a static electricity induced explosion in a home shop dust collection system, post it here. you'll make history- it will be the first and only time such evidence has come to light.

wanna be famous? go for it....

[Vic Baron]

Static charge and sawdust fires from hot metal are two different animals. Grain and dust explosions in commercial environment are not the same thing. I repeat - sawdust explosions from static charge in a home workshop are the stuff of urban legend.

Vic

[Astriapo]

I was just wondering where the myth began then? Sounds like a job for Myth Busters...

[Astriapo]

And someone has already posted that on their website, so I can't ask again. Sniff.

[Walt Conner]

"It gets very dry here in the midwest during the winter. This is NOT urban legend"

Here we go again. I too, live in the mid-west and have had an ungrounded plastic piped system about 20 years, no sign of static problem. We are talking home shop here, not commercial shop. A post a couple of year ago, using Gov. figures, estimated that you would have to reduce a 6" pc of Oak

4x4 to dust in about one minute to get a great enough concentration to cause an explosion.

Walt Conner

[Ba r r y]

Has anyone ever suggested "woodshop PVC pipe dust collector explosion" to Adam & Jamie?