grounding pvc pipe for dust collector

[zoltan]

Hi,

Could someone help me and explain how to ground the PVC pipes for a dust collector? I understood that you must run a wire outside & inside of the PVC pipe. Please, more details.

Thank you.

Zoltan

[Geetar-ist]

ive only installed industrial dust collectors where the ducting is all metal - therefore grounded. are you creating very fine dust?
dust explosions as far as i know are created by very fine dust particleswhich become statically charged and once there are enough - kaboom.

I would imagine that if your hopper is grounded then there should not be a problem but im sure that someone here will correct me..

[2muchstuff]

I have seen it grounded both on the inside and the outside of the pipe. To ground on the inside of the pipe, a bare copper wire is run down the inside length of the pipe. It eventually exits and gets connected to a ground.

I'm no expert but if I remember correctly from high school physics, I thought that static electricity only collects on the outside of a round surface.

[d.dixson]

I'd recommend reading Dust Collection Basics (from Woodstock Intl.). They are pretty clear about running bare wire all the way through a pvc system and making sure its grounded at both ends. They mention wrapping the pipe in bare wire as well, as a secondary measure. The book also says that wire reinforced plastic pipe has no grounding effect at all because its insulated by the pipe itself.

Anyway, if your'e planning to machine any plastics, I'd urge you to ground your pipe properly! A long time ago I worked in a place that had a vacuum take-up for polypropylene filiment coming out of an extruder. When there was no humidity in the air, I'd see first hand what happens to an ungrounded pipe. The build up discharged inside the pipe and sounded like a shotgun going off. I could see the arc through the wall of the pipe. The pipe was grounded at each end, but nothing going through it. I'm sure it would have made a difference.

I have also read in at least one woodworking magazine (publication's name escapes me just now) that most wood dust is immune to static build up because of the moisture content. Sounded like a lot of hogwash to me.

Be safe, hth

Doug

[bml6116]

Sounds like you are NOT operating a commercial/industrial system judging from the use of PVC pipes. Unless you are operating with very fine dust particles at high velocities and high mass flow, I wouldn't worry about grounding. In other words, if your dust collector is less than 7.5hp (and probably much higher) , there is just not enough energy to cause any problems.
Most likely, some people will disagree, but if you do the calculations it will prove that point. BTW there was an article in one of the trade magazine a while back that did not find any hazard existed by NOT grounding small scale dust collection pipe systems.
PS My dust collection in my home shop is 6" SD platic pipe running on 7.5 hp and it is not grounded.

Cheers,
Bernhard

[zoltan]

Thank you all of you for help and advices.

Zoltan

[ckelloug]

2muchstuff,

You're almost right but you forgot an important point. The charge is only on the outside of a conductive surface. PVC is not conductive so your statement doesn't hold. The derivation comes from a special case of Maxwell's equations known as Gauss's law which states that the surface integral of an electrical field is equal to the charge enclosed divided by epsilon_0, the permissivity of vacuum.

I don't know squat about dust collection however I'd assume that some sort of heavily carbon filled plastic pipe would be ideal for the application.

--Cameron

[pbonser]

Dunno if this is a bit late for your needs, but here's a lot of excellent information on dust collection at www.billpentz.com.
It's a very extensive site, but well worth the time spent exploring.
I'm planning on using pvc ducting, & won 't bother grounding it. For a home workshop system, it seems there's nowhere near enough energy in the pipe to cause a spark.

[budP]

HI:
Well I use vacuum to get corn into my house through plastic pipe and in a 10 foot run it will generate enough static to jump 4 to 6 inches, what I do is put some self tapping screws about 8 inches apart and run the ground wire on the outside connecting the screws. Works great.

Bud