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PVC for handing sawdust/chips?

Started by AdirondackMill, January 11, 2019, 11:11:28 AM

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AdirondackMill

We have a fines blower on our chipper and we were looking to use PVC instead of steel blower pipe. Anybody have any experience with doing this?
thanks
3rd Generation Sawmill in the foothills of the Adirondacks. Making big timber is what I love.

Southside

Any curves will wear out faster and you need to ground the pipe or you will have static problems. 
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

SawyerTed

+1 on grounding the pipe.  Static will cause clogs and with give a painful shock.  Sparking may also be an issue with ungrounded PVC.  I worked in a urethane foam plant that used PVC for some floor sweep tubes.  There was a copper ground wire attached every 3 or 4 feet and attached to a ground rod.
Woodmizer LT50, WM BMS 250, WM BMT 250, Kubota MX5100, IH McCormick Farmall 140, Husqvarna 372XP, Husqvarna 455 Rancher

YellowHammer

I used ungrounded pvc for a couple years for our dust collection system until I noticed some 3/4" sparks popping from the pvc to the frame of our metal building. 

All the PVC came out the next week. 
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

moodnacreek


Den-Den

I use PVC in my home shop dust collection system BUT it is not possible to really ground PVC.  It is a very good insulator so even if you painted the outside with conductive paint and ran a ground wire the full length; the inside would still accumulate static charges.  The point the ground is attached is grounded, every other point (more than 1/4") away is NOT grounded).
You may think that you can or may think you can't; either way, you are right.

alan gage

I don't know if it really works or not but the advice I've heard for the best way to ground PVC pipe is to run the ground wire internally through the pipe from one end to the other. That allows (or supposedly allows) the static buildup to discharge to ground at any point along the way.

I used metal for my shop dust collector so can't comment on how it actually works.

Alan
Timberking B-16, a few chainsaws from small to large, and a Bobcat 873 Skidloader.

doc henderson

I have not done it, but if it is present already, I think you could attach a ground on the outside,  Might put a screw on the wire to the inside every so often.  Just like arcing to the metal building, the wire will be the path of least resistance for the static charge.  Do not use pvc for positive air pressure.  It will work for a while, but will degrade over time and when you least expect it, shards of plastic all over.  I have used pex for air, as it does not break into shard and will develop a bulge then a leak.  My shop air is all in iron pipe.  forms a circle Along the walls of my shop.  also added 11 gallons of air storage.  as is often sited on this site, do not ask me how I know.  If I make it to the coleman concert or the next pig roast, might share the story.  I do have short sections of the flexible  corrugated  4 inch pipe to adapt from the machine to collection.  The static can dissipate onto the metal parts.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

Alan I have heard that to and it makes sense.  You could google it as well.  I researched this years ago and the concern was it might cause clogging.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

DMcCoy

I'm not entirely sure about grounding being effective.  You can have both positive and negative static charges close to each other and they don't cancel the other one out unless you have a film of moisture to carry them.  Static shocks for me tend to occur during winter, inside, where the wood heat keeps the humidity low.  Our wood cabinets shrink and swell with the seasons too.   Humidity is a big factor.

Static electricity what it is how to control remove eliminate static shock

Even with static buildup it doesn't seem to be a safety hazard.  

Why dust explosions in a home woodshop are just a myth

It is annoying, getting zapped. :(



Escavader

  I use30 feet or more  flex pvc hose on my woodmizer mp 100 ,way up 12 feet to my blower and then outside with 40 feet of 6 inch plastic culvert.green beams and never an issue .use it to suck sawdust up from lt15 sawmill too
Alan Bickford
Hammond lumber company/Yates American A20 planer with dbl profilers Newman feed table multiple saw trimmer destacker automatic stacking machine Baker resaw MS log corner machine  4 large capacity Nyles dehumidification kilns JCB 8000 lb forklifts woodmizer lt 15 and mp100 and blower

doc henderson

I think the wet wood is less inclined to cause the static and less likely to explode.  I have never seen a wood dust explosion, but we have grain elevator dust explosions in Ks.  Think of rubbing a balloon on you hair, or the kid in the bouncy house who's hair is standing out from their head.  I "wood" say if you are going to use long runs of plastic, I would attempt to ground.  If you think it is a bad idea, then do not use it.  


smiley_blue_bounce
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

kelLOGg

Quote from: alan gage on January 11, 2019, 02:42:05 PM
I don't know if it really works or not but the advice I've heard for the best way to ground PVC pipe is to run the ground wire internally through the pipe from one end to the other. That allows (or supposedly allows) the static buildup to discharge to ground at any point along the way.

Alan
That's what I do on my planer dust collector. 
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Kindlinmaker

We may be drifting away from the original question, which I believe was a chipper chute question, but I'll share what I learned about PVC after a fair amount of research on PVC usage for shop dust collection systems when I did my woodshop. As I dug deeper into it, I learned that there is virtually no way to ground PVC. I am no physicist nor electrical engineer but I will share my takeaways as I understood them. As it is an insulator, a static charge will build up wherever friction causes it in PVC. It will not readily move thru the wall of the pipe to the outside nor laterally thru the pipe on the inside.  A grounded wire running inside the pipe may act as a discharge conduit because it is the path of least resistance but the charge is going to jump (arc) from the point of build-up to the wire which is a potential ignition source. Every system designer and installation expert I found said always use metal ducting. One even told me to use metal as we were standing beneath his personal PVC system; it is the standard safe answer.  I finally found articles that confirm the scientific facts but acknowledge that nobody can recall a fire starting from static in a personal shop PVC system; the limited static build-up and lack of dust saturation don't seem to support it. My shop now has a PVC system and I am more concerned about the potential  fumes from the system burning in a general shop fire than I am about a fire within the system. I'm not sure I would consider it in a high volume or commercial application. I have not been shocked by my system but I have talked with folks who have been "bitten". I think humidity plays a big part in this.  No recommendation either way; just reporting what I learned after a fair amount of research.
If you think the boards are twisted, wait until you meet the sawyer!

YellowHammer

Without doubt, from my personal experience, ungrounded PVC will generate enough static electricity to cause a repeated, significant spark.  However, whether it has enough energy and the right combustible material to ignite a fire, I don't know, and thankfully it didn't happen to me.  The sparks I saw on my PVC dust collection pipe were about 3/4 inch or so long, cracking and arcing to the metal of the buillding, and looked and sounded a lot like what would come from an electric cattle fence charger.  I truly regret not taking video off the phenomenon, but at the time, photography wasn't foremost in my mind.  

The fix was relatively inexpensive, I used snap seam sheet metal ducting from the box stores.  It's strong enough not to collapse with my 5 hp blower and much less expensive than true dust collector metal pipe.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

Southside

I have never seen a dust explosion, but I have seen the results of two of them.  Both at pellet plants, in one case a brick wall was destroyed, and I mean completely destroyed, along with the equipment that was involved.  It is definitely not something I am willing to risk.   
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

YellowHammer

Incidentally, when I installed the $1,000 laser on my straight line rip saw, the dealer warned me that static electricity could damage my laser, and they said use metal or conductive (carbon loaded) plastic dust collector pipe in its vicinity because the dust extraction chute runs only a few inches from the laser.  


YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

AdirondackMill

We ended up rolling with steel. 
Thanks all!
3rd Generation Sawmill in the foothills of the Adirondacks. Making big timber is what I love.

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