DC ducts - 4" or 6"

[Greg G.]

OK - My last words on the subject. Form your own conclusions. (Rhetorical statement for some...) Results of a 10 minute search. And not from some self-appointed expert with a misquoted web site. In this world, most anything is possible-only a fool claims otherwise.

GA Tech studied the factors behind explosions in dust collection facilities in 2002, and determined that 3 of 175 were caused by static discharge - more than defective motors and electrical panels.

Wood shop DC explosion and fire at school

DC Ducts in Woodshop See Post by David Snow in DC in MFG Info on dust/ignition of Dust Collectors and ducts/plastic/static producing parts See Section 5.12.1.4 far as I'm concerned, $3 is cheap insurance against these sorts of things - in addition to the reduction in unpleasant static discharge to your person.

Ciao,

Greg G.

[Unisaw A100]

You mean, you didn't write what you wrote a couple/few messages up? Bring Sybil back to the keyboard, I want to ask her something.

Facts? Please include foot notes.

So again, why do you feel there is a need for a grounding wire? Grain storage in my hobby shop dust collector?

And again, why do I need the metal ducting you recommended?

There you go. A true statement of a true fact and from everything factual that has been gathered on the subject the only real reason to choose metal over plastic. OK, to be fair there are other reasons. :-)

A'yup, and you and urine also.

UA100, who is real sorry for you that you felt you needed to state what you stated and you can't remeber what you said but what the hell, it's been real fun and the sport is priceless...

[Unisaw A100]

Maybe you can deflate your blow-up doll and send it to me.

Be sure to send along the grounding wire.

UA100

[Unisaw A100]

[Norman D. Crow]

IIRC from my days with NCR, that large resistor was to protect you from the rare possibility you *might* get hold of some 120VAC. Theoretically you could grab a live lead with the other hand and not even feel it with the large resistor in the static ground lead.(I got tired of the dam wrist strap and soldered the snap to my watch band)

Nahmie

[Larry Bud]

I have the Jet 1100, but not the cartridge unit. I ran cheapo snap lock pipe from HD, 6", as the two main lines coming off of it. Then I fabricated my own 6x6x4" wyes and put 4" aluminum blast gates on each machine. Then used some black flexible hose from the blast gate to the machine. The hose I used was the 40' length on Amazon.com, I think it's a Penn Industries hose. It's something like 40' for $40. Great value.

[Unisaw A100]

Wait! Is it? Call me a skeptic but it seems I read this somewhere else.

in which of these was PVC cited as the culprit?

Agreed when you cite static discharge.

Probably not given your track record to date.

UA100

[Rick Chamberlain]

So Greg, just how often do you hug your PVC pipe?

[Unisaw A100]

Makes me wonder what he's like when he sees a frozen pipe.

UA100

[George]

People spend hundreds for electrostatic filters in the shop. You get yours free with the PVC.

1) Don't urinate on electric fences when barefoot. 2) Don't lick the pump handle at 20 below. 3) Don't touch your PVC (or your spouse after sliding down the couch to her).

Results are, in all cases, predictable.

[Swingman]

You've handled yourself well on this subject, Greg ... showed common sense, class, and a good deal more charity and than most.

[Mark & Juanita]

A) Nobody is disputing the fact that dust can explode; there is both empirical and anecdotal evidence to demonstrate this. However, for dust to explode, it must be in sufficient concentration and a proper ignition source must exist to transfer energy into the dust cloud to start combustion. In the example you cite, the ignition source was a sustained fire, the dust concentration was caused by a large quantity of existing fine dust in a silo that was storing said material.

What is in dispute is

1) Whether it is even remotely possible to entrain sufficient dust in a home workshop dust collection system for sufficient time, in sufficient concentration to be an explosion hazard and 2) Whether a static discharge in a plastic duct will occur across that concentration of dust, and whether there is sufficient energy in that spark to start combustion. IIRC, someone posted a number several years ago when this subject came up regarding the combustion temperature required to ignite saw dust; the number was significantly higher than what one could obtain from a simple static spark -- you are much more vulnerable to glowing pieces of metal that could enter the DC system from sources such as accidentally grinding metal on one of your tools.

[Jim Wilson]

Two more points to consider. First, at least in this forum, emotion usually enjoys equal prominence on both sides of the debate. OTOH, the research and analysis conducted by some who discourage PVC "grounding" is objectively superior to that done by any who condone it.

And second, the negative consequences may not be insignificant, owing to the sizes of the probabilities involved. The probability of a dust explosion ignited by static discharge from PVC piping is vanishingly small. However, that tiny probability is increased by adding a grounded conductor on the outside of the pipe. Installing an internal conductor or screws through the piping have relatively substantial negative consequences as well. So, the likelihood of some type of undesirable incident is probably greater -- by a statistically significant margin -- when any of these things are installed.

You haven't followed any of the political discussions around here, have you? (G)

Cheers!

Jim

[Jim Wilson]

"Working with a 1100 cfm vac 3 hp running a planer walked by touched pvc pipe duct with grounding wire inside etc. woke up about two min. later aprox. five feet away leaning against the wall that stoped my forward movement!! oh yea had to replace the fire extingusher after I put the fire out. I then did the research on what osha requires for factory setups. nuff said Dave"

This is interesting! More details and a better understanding of the incident would be useful. However, note that because Dave had a wire installed inside the pipe, it is a rather poor argument in favor "grounding" PVC ducting.

Jim

[jev]

The most complete treatise on this subject I have seen is located at

article was summarized in an issue of FWW but what is located here is much more complete. Read it and then decide for yourself whether to use PVC and whether grounding is worhtwhile.

[Jim Wilson]

In response to my statement that...

I have never seen anything comparable from any proponent of PVC DC "grounding."

Jim

[Dave Hufnagle]

Somewhere I remember there was a question about the size of ducts. I too just bought a DC (Delta 1.5hp) and am trying how to layout my ducts.

Dust explosions and health hazards from dust are a concern, but I'm more interested in getting the chips from my RAS, planer and BS. I'd like to hear more about elbows, flex tube, separators, blast gates and all the rest of the stuff that makes up a good system.

Thanks in advance for input along these lines.

Dave in Dayton

[Greg G.]

Hmmm... Missed the mention of the wire in my quick scan. However, he DOES mention the importance of actually grounding it in the sentence above. Perhaps he hadn't actually *grounded* the wire he ran in the pipe - this would lead to quite a charge buildup. Who knows.

Greg G.

[Greg G.]

Thanks, but not a subject I *really* wanted to get involved it, nor a fervent believer in. As I mentioned, just playing devil's advocate for another side for the coin - one in which there in no *real* undisputable scientific evidence to support either side. Life is chaotic - I believe anything can happen, if circumstances permit.

Many of the discussions here devolve into bouts of name calling and personal attacks - often fairly quickly. IMHO, not a good way to present either side of a debate.

Now don't get me started on left tilt vs. right tilt.

Greg G.

[Greg G.]

SWMBO resents that...

I'll make sure to do that very thing - wouldn't want static discharge to zap wee willy.

Greg G.