I have used a single 50 flex 4" diameter flex dust collection tubing (with an internal steel grounded wire) for all my machines for the past 15 years but now it is wearing out with many small holes. I have a 1.5 HP DC with a trash can cyclone. Are there any recommendations for replacement? I was looking at T-7 Santoprene tubing which is supposed to be good at abrasion and contains a steel wire which I can ground. It is about $4.50 a foot. Is this a good choice/value?
Because people will lead you to believe that if you use non-grounded plastic there will be an explosion bigger than the H-bomb.
Where I work, we move 20,000 pounds of material a day through 4" pvc. Probably half of our industry does. I use pvc in my shop with good results. Just emptied the DC last night, in fact. Ed snipped-for-privacy@snet.net
Remember that guy who strapped a JATO to his Chevy Impala out in AZ? He was a woodworker too, had ungrounded PVC dust collection in shop. It blew up one day.
Folks, PVC is an insulator. You CAN NOT GROUND an insulator. If you could, you would not be reading this message because none of our computers (or anything else electronic) would be working.
Repeat after me:
"I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" "I cannot ground PVC" .....
Well, some believe that the PVC can accumulate static electricity, then discharge (by means of a little electrical arc) and ignite the dust, thereby causing your own rendition of a grain silo explosion.
These are probably the same people who turn off their cell phones when the fill up their cars with gas to prevent the deaded "cell-phone gas station explosion"; because... well... gosh... even though we've never tracked down a documented/verified case of it happening, it *must* happen a lot because everyone talks about it, right?
Ugh. That's it! I'm submitting this one to MythBusters
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answer your question, the May 2003 issue of American Woodworker (page 54) has a section on setting up DC in your shop. The guy suggests using steel instead of PVC for a variety of reasons. *One* of the reasons is static buildup... but even then, the guy doesn't say that there will be an explosion. He merely talks about the zap you can get *yourself*. The other reasons are that steel comes in larger diameters than the 4" where PVC generally stops at.
Strangely, he didn't mention how great steel looks when you accidentally bump a tool into and dent it... or how yummy it feels when you slice your hand on the sharp steel ends... or how the sheetmetal screws protruding into the tube help the airflow!
He does point out though that, at large diameters, the price difference between PVC and steel starts to become a non-factor in the decision process.
Issue 13 of ShopNotes has an article about building your own cyclone and collector. The seem to use all steel.
I recall reading some article about a week ago where the author went into 4 more-likely fire hazards in your DC system than static electricity. One of them was hitting a nail (or other metal) which can cause red-hot sparks to go wafting through your DC system to the collection bag. There were a couple of others. If I track down that article, I'll come back and post it here.
Actually, it just occured to me that you *can* purchase electrically-conductive paint... probably in a spray, too. So you could make your PVC system grounded without needing wires in it.
... for those so concerned about grounding, that is.
snip post about how pvc isn't a static explosion hazard, but metal duct is better anyway.
wouldn't metal duct (or more likely the sheet metal screws) present a lot more opportunities for bits of hard stuff like chips of metal or pebbles from the shop floor to strike sparks? of course the big one is still gonna be the impeller blades themselves....
FWIW, I highly recommend metal tape versus duct tape - at least from the standpoints of being a much better seal and the tape not delaminating from the adhesive layer after some time. The metal tape is more expensive. But a regular HVAC duct with metal tape at the seams and the joints, if you want, is darn "airtight" in this context, IMO. The metal tape won't handle bumps and such as well, so in some places you could use duct tape over the metal tape. -- Igor
Yes, PVC is more a dielectric. That said, one puts wire through the ducts so that it "collects" the charge that is generated by the movement of the air/wood through the duct. You ground the wire to dissipate the "static charge".
So while PVC doesn't "conduct", it can generate "Static electricity" under the right circumstances. That is what you're collecting and grounding.
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