Grounding Dust Collector???

[rbertalotto]

I've watched dozens of videos on the subject.....Lots of folks drive short screws into the PVC pipe with 1/16" exposed to the inside of the pipe. Then they wrap bare copper wire around the pipe and terminate it at the vacuum chassis.



A few questions,



If I run screws into the PVC pipe and run bare copper wire from screw to screw, why do folks wrap the wire around the pipe? Why not just run it along the side? Static should be dissipated through the screws with nothing left for skin effect?



Can I simply ground it to the same ground in the electrical receptacle box that the vacuum plugs into? (My vacuum is in another, adjacent building for noise abatement and running the ground wire over to it would be difficult.



Thanks!

[John Hasler]

Run the wire along the side and ground it to any grounded box (or anything that is connected to a box). The wrapping does nothing and any box provides an earth ground.

[rbertalotto]

Thanks John, that is exactly what I thought. Wrapping the pipe just wastes good copper wire! Merry Christmas!

[rbertalotto]

Here is an intertesting video on the subject

https://www.youtube.com/watch?v=WJ8NMYlhaLQ

[Lew Hartswick]

A single "wrap" between the screw is to keep it from being snagged and pulled off. A "mechanical" phenomena not electrical.
...lew...

[John Hasler]

Putting the wire inside would do a better job of protecting it. If you feel that you need sharp points twist the wire and snip off the loop at the same interval as you would have put in screws.

[Inspector]

Here is some more reading on the subject. https://www.woodcentral.com/articles/sh ... _221.shtml

PVC is an insulator so screws at intervals will only discharge static buildup in a small area around the screw. What is reputed to work better than a wire inside, doesn't snag chips, is metal foil tape down the inside of the pipe and similar inside the fittings. The two reasons for trying to ground the ducts are because the shock can hurt a little, not a good thing when near spinning cutters, or to prevent stray discharges in computer controlled machines that can fry some of the electronics. If you really are worried about the static you should be using metal ductwork and have the peace of mind.

Pete

[Rich_Carlstedt]

It's an interesting subject to talk about. I have never worried about it because I have a metal shop.
I think that the danger is the volume of dust at one time and the total surface area of those particles exposed to oxygen .
Anyway, years ago I ran a operation that required mixing Natural Gas and air to the proper combustion ratio and then pumping it through
2 and 3 inch steel pipes to burners . Now to shutoff a burner, you wanted the valve close to the burner, and if the pump ( blower) shutoffs accidentally with the valve open,you get a mini explosion within the pipe and if it reaches the blower, someone will get hurt !
The same occurs if the valve does not close completely and the pump stops. So how do you prevent explosions ?
Thats the reason for my post
Simple solution is to install Metal Screens in the pipes. When the flame front (explosion) hits the screen , the metal screen absorbs the heat and the flame stops ... If the source of fuel ( air/gas in this case) continues and allows the screen to heat up, then the flame can continue. In our case we had multiple screens and a thermo sensor at the pump...
Anyone actually know of a home PVC pipe explosion ? ( not heresay)
I ask because i don't think wooden chips present a problems , but continuous heavy wood dust from a large power sander is another factor IMHO
Rich

[Russ Hanscom]

Flame arrestors in piping is common in certain industries, but not any screen will work. There are specific design requirements for flame arrestors, not a do it yourself device. Commercial flame arrestors are NFPA or UL listed.

[liveaboard]

I was told that the risk was explosion, run a grounded uninsulated wire lengthwise inside PVC pipe; but like said above, better to get metal, ie galvanized air ducting or stove pipe.
It's cheap, and you seal the seams with duct tape, using it as intended for the first time.

That flame arrestor idea might have trouble in a dust + chip duct, it will likely get clogged.

[10KPete]

Yes, a screen in a dust/chip duct would be problematic at best!

Rich was speaking of vapor pipes/tubes/etc and those flame arrestors do work well and usually no special metalurgy is required. A series of metal screens in a duct stops the hot screen re-ignition propagation.

Part of the arresting mechanism is cooling, but the major part is the large velocity increase seen at each hole in the arrestor. Rarely is the vapor moving thru the duct at high velocity but the advancing flame actually sucks the vapor through the holes thus causing the velocity increase. Then it can get complicated but the disruption of the advancing flame front is usually enough to slow/stop it. Most flame arrestors in things like safety fuel cans are multi-layered spaced just a bit apart so any flame front is quickly quenched. And quietly. I'm quitting.

Yeah, used to play with that stuff way back when. Fun stuff!

Pete

[Rich_Carlstedt]

Thank You Pete,,..Yes, I was not advocating using a screen in a wood chip evacuation system.
I was trying to point out that metal chip / grit systems do not seem to have the fire hazard you may find in PVC pipe systems

I have to believe that someone can figure out a simple solution as I am reminded of my friends Potato Canon which he shot at night
When he ignited the gas /air mixture, the PVC pipe lite up briefly, but did not break as it launched the Potato, so I would think that the real danger
is not the pipe, but the blower and collector as fire hazards ?
Thats why I asked if anyone had known of one occurring

Rich