Hey Gang,
My name is Mike I'm new here, could someone tell if you have to run braided wire through pvc pipe that is hooked up to a dust collector so that static elec. don't cause a explosion or fire, some guy at Home Depot said I had to do that, is this true?
Thanks for any help!
Mike
On Wed 01 Feb 2006 01:10:08a, snipped-for-privacy@webtv.net (Soo-Line-Mike) wrote in news: snipped-for-privacy@storefull-3272.bay.webtv.net:
Yep. If you don't do it, your shop will explode and take the whole neighborhood with it, ten seconds after you turn it on. Happens a couple times a day.
Not common. But do keep in mind... Fuel(wood dust) + Oxygen(air) + Heat (spark) = fire
I was getting static shocks on my tablesaw until I grounded my DC pipe to it. A small wire will work, it doesn't have to be braided. I think using metal tape is even better--fewer places to catch chips.
Well, anyone who knows about the defunct Soo Line (CN now), deserves a straight answer.
Grounding an insulator isn't possible. In order for a ground to work, there must be some conductivity to get those electrons to the wire.
Then there's a really narrow set of physical circumstances required for a dust "explosion," which include extremely small particle size, extremely dense distribution, and an instantaneous ignition source.
Tempest in a teapot.
I can not find the link, but one of the wood working magazines on the web did a researched artical on this. They concluded that the ground was not needed and if not done properly, the ground could increase the chance of a spark. They also stated that the risk of fire is much more real than the chance of an explosion. I do not run any ground in my unit and I feel comfortable with that after reading the available data I found on the subject. Brad Harding
No.
This doesn't make sense. Are you saying that by touching your table saw you were getting shocked?
There is an article about this on Bill Pentz website.
Of course it is - and it's regularly done for dust collectors. You can either apply a conductive surface coating or you can make the insulator conductive (usually by mixing carbon black in with the plastic used for moulding it). The monitor you're reading this on right now is very probably insulating plastic with a conductive coating sprayed on the inside surface.
Insulators are also conductive - if we're talking about real-world materials in real-world environments and static discharges. A "brush" discharge (the sort you notice) is formed when an "insulator" has a surface coating of moisture, dust or similr on it that's insulated enough to allow a charge to build up, but potentially conductive if it can be induced to break down when a discharge starts. Purely insulating surfaces don't store enough charge to provide a noticeable discharge, it's these surfaces on the boundary that make the big discharges you can really feel.
In woodworking workshops though, static discharge is just a nuisance problem, not _ANY_ explosion hazard. It will be worst on metal pipe sections separated by insulators, so if you have any of these (Y-joints maybe) then it can be worth earthing them. You only need an external wire, not an internal one - although some people advise these "to earth the flowing dust" (ridiculous), wood dust is also abrasive enough that you'll wear through the wire before long.
Twaddle! If you make it conductive, it's no longer an insulator. That should be obvious even to the quarrelsome.
I don't worry about an explosion, but I have been zapped multiple times while vacuuming the shop floor on a cold day until I grounded the hose.
Of course it is (although you may have only affected the surface, not the volume) - but your original statement "Grounding an insulator isn't possible." is far too simplistic. There _are_ things you can do to reduce charge build up on insulators. The issue under discussion is that it's not worth doing this, not that it's impossible to.
Let us know when your conductive anti-static coatings are able to tolerate the abrasive effects of shop crap running through them, won't you?
Until then, there is a reason why they call it "static" electricity....
On 2/2/2006 1:53 AM Max Mahanke mumbled something about the following:
Mythbusters did a thing trying to get a large enough static spark to create an explosion on a PVC pipe. Couldn't do it with sandblasting the hell outta the pipe. Minor zaps from touching it was all that was possible.
There can be a very large static buildup on the PVC pipe, insulator or not. And the static can cause sparks and therefore set off a fire.
A wire run along the length of the pvc pipe and grounded will help. A screen or shield around it would be even better.
There are plenty of small particles in a typical woodshop, and most of us have drawn a spark from a static charge. A spark along a long pvc pipe could do a lot worse.
Now, a cheap low power dust collector might not draw enough air to do damage. But my ancient Silver King shop vac does. It can light up a neon lamp next to the plastic intake nozzle.
George wrote:
Insulator vs. Conductor is a scale of resistance. In the case of a "conductive coating", all that is done is making a slightly less resistive coat that can conduct static electricity along it's surface to keep a static buildup in one place from happening. There isn't enough of a conductor to run a current through, just spread the charge out.
This same principle is used quite often in many ordinary things: Fabric softener / clothing static guard The pink/silver plastic bags that electronics come in ESD static mats electronic technicians work on the plastic pads roller chairs roll on in the office coatings on monitor screens
Take the static guard for instance. It obviously isn't enough to make your shirt into a "conductor", but it does allow static to dissapate along the surface of your shirt so you don't shock yourself everytime you touch a doorknob in the winter.
My dust collector's impeller housing has a bulk resistivity that's similar to that of anti-static plastics in the electronics industry. Looking at the colour it's chock-full of carbon black. Obviously you can't retrofit this, but it's an easy thing for the maker to specify - quite possibly it's just in there as a cheap filler anyway.
Incidentally there are copper/nickel multi-layer platings that can be applied to plastic and are tough enough to resist abrasive particles going over them. I've no hands-on experience with these for wood, but they're tougher than the simple sprayed paints.
No, it can't (search the archives). There's a limit on the discharge energy you can produce from this setup and it's demonstrably not enough to start a dust explosion in wood dust.
Mix solvent vapour in - different situation.
Suck up a spark or smouldering ember - different situation.
Strictly speaking this isn't even a "spark" (as these things are categorised by electrostatic engineers).
Reinventing the capacitor, are we?
It's called static because it doesn't flow.
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