Dust collection safety


Airick55

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if you doing small lengths its usualy not a problem over long length then it can develope into a issue. but all you need to do is ground the coper wire pull it through the hose and attached it to the ground thats basicly all you need to do. coper is a great conductor of electicity much more then plastic or any other material your dust collector hose is going to be made of.

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I didn't read Russ' article, but since the word "myth" appeared in the title, I'll assume that it states the whole PVC/static/shop explosion thing has been pretty much debunked. You might get zapped, but your shop isn't gonna blow up unless you have a gas leak somewhere, in which case you'll probably blow up regardless. :) Happy thoughts.

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I have metal pipe, and the tools and cyclone are grounded. I still get zapped at very low RH times of the year! Why? Electricity flows both ways. :lol:

Discharges happen because two surfaces are are at different potentials. My system may be grounded, but I'm not. In some cases, the static charge is actually on me, not the pipe. Anytime you aren't at the same charge as the thing you touch, current flows, even if too small to feel. So, if we're different enough, I feel it. Regardless of what side is "more grounded".

This is why electronics shops who work on grounded bench mats have some sort of way for the human to lose the charge before touching the grounded circuit pack. Electronics can be damaged by discharges too low for a human to feel. This can be a heel strap that drags on a conductive floor, a wrist strap that is connected before touching the equipment, etc... These devices include a resistor to prevent large current flows that could injure the human. Humidity control helps a great deal, too.

In the airplane world, we use a bonding strap that gets connected before we bring a fuel nozzle to the airframe. All we're doing is putting the aircraft at the same potential as the nozzle, preventing a spark in the fume rich fuel filler neck. We're not actually grounding the airplane, only equalizing the electrical potential, just like the strap on the electronic tech's body. Sometimes, the bond strap goes to a rubber tired fuel truck, with no ground connection. Other times, to a ground based pump that is absolutely grounded. We just need to be the same.

In past setups, I've had DC setups PVC with and without grounds, metal specifically grounded, and metal casually grounded via the collector and tool connections. The only difference I ever noticed was that all the cockamaimy internal wires or through studs in PVC simply collected debris and caused clogs.

Dust collectors can most definitely burn, sometimes hours later, because people suck lit cigarette butts into them, they sharpen tools on sanders that draw burning metal shards into the pipes, they cut metal with bandsaws that are caked with sawdust, or they hit steel with carbide cutters... In other words, they throw burning embers into a pile of sawdust, that smolders until it either goes out or grows.

Blowing one up is actually very difficult, even when trying, as detailed in Russ' link. AFAIK, there has never been a documented case of a small wood shop dust collector exploding due to static. I would imagine if it happened, news would spread through the woodworking world faster than it blew up.

If shock prevention is the goal, adding a bit of humidity will often cure the problem completely. If that's not an option, different shoe sole materials can be tried.

For some real mind bending, read up on the "skin effect"...

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There's a couple of books available at Woodcraft I read through (one of which I purchased there) about setting up DC systems. One of the things I got out of it was how to wire the pipes for grounding. (Both PVC and metal.) Bare copper wire is not hard to come by, but, as CPB mentioned, clogs come. Bill's site recommends grounding (from what I remember, it's been a while) inside the pipe. On a short, small shop, I'd say that's not always needed.

The majority of DC work is going to be trial and error. Of course, since you're here, you can use our error to ease your trial.

Currently (no pun intended), my DC setup is a dust pan and broom. Fine for the large shavings and chunks, not so good on dust. Then again, I don't really have any space for anything larger than a bagless house vacuum converted into a dust collector. Although, I'd give Marc's video on the cyclone shootout a couple of views, before tackling the Dust Collection Question.

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