Static shock hazzard or not?

Tom Baugues

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I added a dust collector to my shop this summer. I used PVC pipe for my runs. One of them runs down a wall that I had insulation between the studs. I removed the insulation at the time to get it all fitted but now I wonder if I will have any stactic issues by adding the insulation back. There are also electric wires going through this section.
Note: this is on the outside wall of my shop. My dust collector is in the other half of my building and I ran PVC through the walls.
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Well, to start the debate. Yes you will have static, but shouldn't hurt the insulation. Your static comes from movement of the dust through the pipes mostly. Some folks take the bare copper wire and either wrap the pipe or run the wire in and out of it to help discharge static. If you run the wire, ground one end to your collector or a near by outlet.
 
Let's start with the ground wire, lightning rods on the roof, a grounding chain hanging down from your belt, don't wear silk garments.......especially underwear:eek:, rubber soled shoes............yep.........that should cover it. Maybe a hat made from aluminum foil.............ya jus' never know. :huh: :rolleyes:

Plan on an annoying shock when you least expect it but don't worry about being blown up because there is sawdust in the air. Like Darren said, ground the system.
 
Let's start with the ground wire, lightning rods on the roof, a grounding chain hanging down from your belt, don't wear silk garments.......especially underwear:eek:, rubber soled shoes............yep.........that should cover it. Maybe a hat made from aluminum foil.............ya jus' never know. :huh: :rolleyes:

Plan on an annoying shock when you least expect it but don't worry about being blown up because there is sawdust in the air. Like Darren said, ground the system.
 
So I should have a bare wire runing through my pipes then exit the pipe somewhere at the dust collector and attach it to the metal frame of the dust collector. Do I have that correct?
 
Oh look, a hornet's nest! Lemme poke at that a bit... :D

Honestly, I wouldn't worry at ALL about it.

Leave it for a bit - see if you get any nuisance shocks that you can't stand to tolerate. I've seen reports that after awhile the static buildup reduces significantly as a fine film of dust settles on the inside walls of the PVC. Static buildup is caused by dissimilar materials passing past each other - i.e. dust + pvc. When there's a fine film of dust on the surface of the PVC, it's then dust + dust and very little buildup happens, eliminating many users' static issues.

It's impossible to ground an insulator, since insulators don't conduct electricity and PVC is an insulator. Secondly, STATIC electricity is named such because it doesn't flow (because it can't, it's built up on an insulator!). A wire may discharge some of it, but only a very little in the immediate vicinity of the wire itself. It may be enough that you notice - it may not. It's a little bit of work and I would suggest holding off until you know you have a problem first. :)
 
Not sure if any of this applies to the question, but I'll throw it out for consideration. I have a Delta 50-850 with clear flex. Lots of static, but didn't worry about it--uncomfortable at times but not a big deal. I added a galvanized trash can with a LV lid. The can is on the concrete floor. With the can in the picture the static issue has totally disappeared.
 
So I should have a bare wire runing through my pipes then exit the pipe somewhere at the dust collector and attach it to the metal frame of the dust collector. Do I have that correct?

NO!!!! I ran a DC system for the 14 years with PVC & no ground wire it will nip you a bit for a while & after a while when it gets good & dirty it won't. Ground wire on the inside of the pipe is just asking for a plugged duct.
 
I think there are arguments both directions.

There are those that have run for years without issues and I've heard of people having fires. I wonder if some of those had a similar problem as Bryan Cowing did a few weeks back with a dull bit causing a spark and that getting sucked into the collector. Growing up we used to take a bucket of dad's sawdust out to the burn barrel and take handfuls and toss them in the hot fire. It was like the magicians with their puff of smoke or like watching a cup of gas thrown on a fire...poof.

I'm probably going to ground my pipes, but will probably spiral it around outside the length of the pipes. Mostly to ground any build-up, but I look at it as cheap insurance.
 
Absolutely for sure it's your shop, do what makes you feel better.

I just want to point out that it's a myth that a home shop DC could have a fire due to static build up on PVC ducting. There isn't enough energy in the arcs to ignite the dust, thankfully. Yeah, we've all heard about flour silos blowing up - totally different scale, here - vastly larger charges and particle concentrations. Apples to oranges for sure. It's more likely that an ember or hot steel spark will ignite the dust in the bag of your DC before any cloud of dust we could produce would be.

I won't keep poking the hornets nest - if anyone's curious, this is one good source that explains it in pretty plain english: http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html

There are lots of them but that's probably my favorite source for compiling it all in one area and making it easy for me to understand.

FOR SURE - do what makes you feel safe. In the spirit of information, my reason for bringing it up is to present what I have learned from. Your shop, your rules. :)
 
Don't rely on a dust film inside of your PVC ducting. I have been using PVC ducting for 5 or 6 years. The inside of the pipe is cleaner now than it was when it was installed. The dust going through at 130 (or whatever) miles per hour has polished the insides beautifully. If you have good air flow, there won't be any dust in your system---well, yes there will be, but it is in the "bag" at the end of the run. I was assuming smooth, solid, PVC. Flex ducting has such crazy air currents in it that dust is probably going to collect---at least a thin film collects in my "Flex" drops.

Enjoy,

JimB
 
Okay - here is some good old physics for those who might care. Consider the DC pipe made of PVC. Cross section is a circle. As static charge builds, the number of electrons will increase in the PVC from the flow of dust/wood chips. As the number of electrons increases the pipe gains a negative charge. These electrons, having the same negative charge will do their best to get away from each other (like charges repel) and will eventually migrate (be forced actually) to the OUTER surface of the pipe (this is why when YOU complete the circuit between the pipe and the ground by touching the pipe- the excess electrons will move from the pipe through you and you get zapped) SO - putting a wire INSIDE the pipe would be less effective than wrapping the wire around the OUTSIDE where the electrons are being forced to accumulate, connecting this to a grounding source should provide a constant discharge of electrons as they build. Obviously using metal DC pipe provides an easier way to ground this static charge. Now an earlier post states that over time a wood dust film will likely coat the inside of the pipe and this SHOULD decrease or eliminate the need for a separate ground wire wrap. Hope this helps - BILL
 
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