Vacuum Pipe Grounding?
I am about to build a floor sweep. Simple box with a 4" flange on the back. I plan to put the intake under the bench that a wood lathe is on.
Question: Using plastic pipe or hose, a normal vacuum pipe grounding wire goes from machine, along/around pipe, to dust collector. If the floor sweep is wood (or plastic) and not bolted to a grounded floor, where should the ground wire start?
02-26-2012 02:06 PM
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I am a firm believer that you cannot ground an insulator like plastic pipe or a wood box like your speaking of. I have a large amount of S&D ASTM 2729 thinwall S&D PVC pipe in my basement for my cyclone DC system, and not one single ground wire. Pictures here: https://picasaweb.google.com/113966569709555812037/DC
There are HEATED debates all over the internet about this very subject, but the possibility of an explosion in the home is just not there. Now, if you are just trying to bleed off some static electricity that may build up on the surface there are mixed results with that also.
What is you goal?
What DC do you have?
What kind of pipe do you have?
I'll go ahead and throw my 2cents in here as well. I have a very large dust collection system in my shop, all plastic pipe, NO GROUNDING. I've done lots of research on this topic and the reality is pretty clear to me now. There are ZERO documented reports of a single explosion due to static charges on plastic pipe for any size wood shop that a hobbyist would have. In fact, it's not clear that there is a single event documented even for commercial wood shops.
Can you get a shock? I suppose it's possible, I've yet to get one from my system and I haven't met a person yet that has told me of a shock.
Could not resist comment on this one, LOL
Vacuum Pipe Grounding? Even & I mean Even if there was a spark what will explode? The pipe can not conduct electricity so the spark could not even reach the dust extraction collector. This one made me laugh, that's why I had to comment.
When I bought a Grizzly 2 HP DC, it had a braided copper static line attached to it. When I'm running a 16" planer, I wrap the 4" flex tube with the static line & connect it to the planer & the DC. Without it connected, I can feel a very definite static field around the flex tube (when the DC and planer are running).
It's only 3-4 feet from the planer to the DC. It will be 20 feet from the DC to the floor sweep. Probably using PVC, my thought was to wrap the PVC with a braided line to absorb the static. Connecting one end to the DC is fine, but there is no machine on the other end.
Will an "unterminated" wire collect the static created by the dust going thru the pipe?
OK, so static control is your goal-this can be a problem in very dry areas. You can certainly continue the braided wire around the pipe towards you new floor sweep. You can pick up a ground anywhere in the shop, it does not have to be to one from the DC, you can find the main utility ground, a cold water pipe (if you have a copper system), a metal EL box mounted on a wall...
As I understand it, any ground wire on plastic pipe has to be on the inside where the static is generated by the rushing air flow. Grounding the outside doesn't work since the plastic acts as an insulator. Just my 2-cents based on what I've read on the subject.
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.
What's the real danger?
There are three realistic dangers in home dust collection, none of which has anything to do with PVC.
1.The most remote danger comes not from the duct, but the dust inside the filter. Not literally the filter, but the airspace inside. Here you have a much larger dust cloud that can stay around after the blower has stopped. The odds of having an explosion here are greatly higher than in the PVC ducts, but still extremely unlikely.
2.A much more likely danger (and something has has actually been documented) is ignition in the collection bin. Sucking up something metallic which then strikes the blower impeller (fan) can create a spark that goes into the pile of sawdust. This type of ember can smolder for hours before flaring up, taking your shop with it. The simple answer? Install a standard fire sprinkler above the collector.
3.The greatest danger from a home shop dust collector is poor filtration. Most (probably all) inexpensive dust collectors using filter bags still allow a tremendous amount of extremely fine dust to blow right through the filters and back into your lungs. What you really have is a large vacuum, not a dust collector.
Easy Killer We are all learning here and each of us have our own comfort zone.
Originally Posted by Dewaltcarp
This is good information. Information that helps people to stop worrying about things rather than being told not to. Thank you.
Originally Posted by Dewaltcarp