Anybody buy from Leichtung Workshops?

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wrote:

We know. <G> How would grounding change this?    

A plastic insulation factory. Where is the wood shop explosion?

The sawdust was already on fire from another source. How would grounding change this?

Where is the wood shop explosion?
We would like to see an actual WOOD DUST, not insulation, grain dust, or plastic explosion caused by STATIC ELECTRICITY, not glowing sharpening embers, cigarettes, torches, etc... that would have been prevented with an internal ground wire.
Barry
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What makes you say that? It refers to a rash of explosions and fires caused by various spark sources throughout Canada and it does name static discharge as a source of ignition. If your concern is that sparking usually occurs to ground, grounding multiple points on a non-conductive (i.e., charge-holding) material would minimize its ability to hold a charge at all.
<<<SNIP>>>

is named that one might as well "run with scissors" (I've never seen a documented case of THAT either...my assumption is that most of the Darwin Awards for that were already handed out about two generations ago)??? If you've ever seen a dust explosion of any sort, it results in a fireball and if caused by static discharge there would be no ignition source to be found (unlike embers, torches, cigarettes, etc)...as long as you don't live near me or my relatives or friends, do as you wish with the information and I truly DO wish you the best of luck.
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wrote:

the point is that despite lots of chicken little running around, there are no documented cases of home shop dust collection systems exploding from static electricity generated by plastic pipes. none. zip. zilch.
plenty of industrial woodshop and flour mill and so on dust collection explosions... mostly caused by things other than static from plastic pipes. IIRC, plastic pipes aren't allowed in industry for that very reason. they actually move enough dust with enough air for hot static discharge to be possible. they also have 24" pipe and 40 HP blowers sucking sawdust from dozens to hundreds of machines simultaneously.
my measly 2HP dust collector and 40 feet of 4" plastic pipe isn't gonna blow. nope.     Bridger
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wrote:

"Recently, firefighters were trying to remove smouldering sawdust from the hopper of a dust collector when an explosion blew burning materials out of the equipment. Six firefighters and eight workers suffered serious burns and cuts. The explosion happened 36 minutes after the fire apparatus arrived."
Read the first sentence.
Barry
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Unfortunately, the link at the end of the following citation no longer works, but it did when I excerpted the article a couple of years ago.
A research scientist at MIT has looked into this matter very carefully, both anecdotally and empirically. In the summary of his quite long report, he says:
"...I have read more than a dozen research papers on this topic recently. The thing I am most struck by is how hard these guys have to work to get dust explosions in the lab. It is not hard to get ignition if one makes a very carefully controlled, nonmoving cloud with just the right dust mix, and introduces a spark from a very carefully designed sparking mechanism. But no one seems to be able in lab sized experiments to get electrostatic discharge ignition of even very highly combustible dusts in remotely realistic situations, and they do try. Is is possible? I presume so, but it is extremely difficult."
"...there has never, to my knowledge, been a documented case of an explosion problem with PVC in the home shop or a case of an explosion in a filter bag in a home shop. A friend of mine who is a professional cabinet maker asked his fire inspector what he thought about the hazard of PVC ducts, and the fire inspector said he was far more concerned about people keeping lighter fluid under the kitchen sink. The fire inspector was intrigued and checked whatever registry of fire information he had available and came back and said he could not find one reference to a problem in a small shop with PVC ducts."
"In all the years that this has been debated on the Web, not one verifiable report has surfaced of an exploding home shop dust collector. I know full well that anecdotal evidence does not make good science, and just because I don't know of a problem caused by an electrical discharge in a home shop DC does not make it impossible. But, such evidence is certainly food for thought, and at least shows that such events, if they exist at all, are very rare."
Near the end of the report, there is an explanation of several common MYTHS (untrue, unfounded beliefs) about home workshop dust collection. That list (without the accompanying explanations) is as follows:
Myths--the following assertions are NOT true
1. PVC ducts are dangerous. FALSE
2. You can ground PVC. FALSE
3. The only thing of concern in a dust collector are the ducts. FALSE
4. The external ground wire works by reducing the static on the outside of the PVC. FALSE
5. The external wire must be bare. FALSE
6. Grounded screws can not help as they are too far apart. FALSE
7. Grounding works by removing charge from the dust. FALSE
8. Metal ducts keep the dust from charging. FALSE
9. Any spark will ignite the right dust mixture. FALSE
10. Grounding PVC works by removing charge at a point, and since charge must be uniformly distributed, it therefore removes charge everywhere. FALSE
11. Getting a discharge outside the ducts, say to your finger, means you also have discharges inside the ducts. FALSE The full report can be found at:
<http://www.gis.net/~dheaton/woodworking/articles/DC_myths.shtml
--
Regards,

Benoit Evans
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Do you know who did the study and when??? You say it was published a "couple of year ago"...any idea of when the study occurred?

board material. Not too many raw materials are dangerous. THAT usually depends on one's design.

static charge does not flow (definition of static), the distance from ground potential is what is important...I'd bond a wire to the PVC in multiple locations to ground to hold the static charge to a very low voltage. It is true that you would not eliminate static charge altogether by doing something like this.

manufacturers have already taken due care to make certain that the collector itself cannot become a source of ignition.

the dust can even hold a charge (I tend to doubt it, however).

PVC. But, also, if the dust can charge, no individual particle could hold a charge sufficient to ignite the sawdust.

mixtures.
able to conduct through the thickness of the duct meaning that what is inside could experience sparking as well.

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wrote:

here's the updated link.
http://mywebpages.comcast.net/rodec/woodworking/articles/DC_myths.html
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We'll see if the 5-6 links I posted in response actually do post...but another thought came to mind. Since any dust collection system will cost at least $200, why are you kicking and screaming over $5-10 worth of wire to make it safer? Just curious...
Like I said in my previous post, an ESD-caused sawdust fire or explosion would be most likely with a high concentration of FINE (very fine) sawdust, like from sanding, rather than what your table saw or planer generates.
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says...

Not the $5 to $10 but the 30 to 40 hours of time it's going to take to wrap, interconnect across gaps, and seal any holes if you run the grounding inside the pipe, all for a very dubious benefit. The other problem is the fact that if you run the wire around the outside of the pipe, the only thing you will do is protect yourself from uncomfortable discharges when coming in contact with the pipe -- as you alluded to in your original post, the plastic pipe is non-conductive, therefore the charge is distributed across the entire pipe and thus will not fully discharge, particularly if the static is being generated from the friction of the sawdust on the inside of the pipe. Grounding the inside of the pipe leads to other theoretical problems: a) you cannot wrap a conductor around the inside of the pipe, thus one must lay the conductor inside the pipe. b) The problem here is since one is laying a conductor along a non-conductive surface that is becoming electrically charged, one could postulate that you are actually creating an environment in which you have actually increased the potential for explosion by providing a discharge path for a spark that could occur from the potential generated across the diameter of the pipe, discharged to the grounded wire inside the pipe. This could be further excacerbated in a case in which the wire could become airborne due to the airflow in the pipe, thus isolating the wire from the pipe until enough potential is achieved to generate a spark from the pipe to the airborne wire.

Given your first link, how much sanding dust would be required to be generated to achieve sufficient concentration for an explosion? I cannot picture any workshop equipment capable of generating sufficient volume and concentration of sawdust to ignite. Further, that experiment requires a candle to ignite, this is not equivalent to the low amount of energy imparted by a static discharge -- the duration of discharge is too short to sustain combustion. i.e., what you have posted does not constitute proof of your assertion.

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On Tue, 09 Dec 2003 03:41:15 GMT, Mark & Juanita

And if that actually _worked_, you'd think by now somebody would have posted a pic of their NEW! IMPROVED! system--
--pvc pipes totally encased in aluminum foil. :)
"I'm grounded NOW, baby!!!"
M--
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wrote:

In my case it had nothing to do with cost. I GROUNDED my system. I pulled the wires out after getting tired of semi-weekly clogs caused by jointer and planer chips and offcuts getting stuck in the wires. I haven't had a clog since I pulled the wires out.
I can also see no noticeable difference in static electricity buildup or the other performance aspects of the system. My ground wires were grounded at copper cold water pipes which are in turn grounded to the same 8' ground rod my radios are. The connections were soldered to the pipes.
If you want to ground yours, feel free. Until someone comes up with documented evidence, or for that matter, documented conjecture on the part of a fire inspector that grounding would have prevented a WOOD SHOP (NOT plastic, grain dust, etc...) explosion, I'll continue to question "safer". I'd even go with "better safe than sorry" thinking, if the wires didn't cause so many clogs.
Barry
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So, your system uses PVC ducts and you ran internal ground wires (which you have since removed)? I could see where that would cause you some grief. In the manufacture of electronic products, ESD protection is provided with much higher resistances. Many of the 3M products to reduce damage due to static use about 1,000,000 ohms to ground (or even 10,000,000 ohms). I've never put an ohmmeter to a piece of PVC (plus I'm sure it would vary by manufacturer as any impurities would change the resistance) but I'd investigate putting the ground wire on the outside...worst case you could even use small self-tapping screws to bring a ground from the outside to the inside and I wouldn't think that would cause the dust collection system to clog.
In spite of how the tone of our exchange may have sounded to you, I fall in the "better safe than sorry" camp...if you re-read my original posting on this, I merely stated that it was possible based on several factors. I don't think that it is highly likely for very many home woodworkers because most won't generate the concentration of dust nor the fineness.
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wrote:

I work in the electronics biz (telco), and we do all kinds of things to contain ESD. For an entirely different reason. <G> Reasons for that resistance include SLOWLY discharging the static electricity.

So do I, which is why I originally installed ground wires. When I replumbed after a shop rearrange, I removed the existing internal wires, and thought about driving screws in from the outside. After using it ungrounded for a while, I saw no reason to bother to ground it.
Barry
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Not to mention worker safety (in case of other fault conditions), otherwise the assembly labor would likely be barefoot on copper ground plates to save $3 ICs... For production, one of the nicer solutions is ionizers.
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: Like I said in my previous post, an ESD-caused sawdust fire or explosion : would be most likely with a high concentration of FINE (very fine) sawdust, : like from sanding, rather than what your table saw or planer generates.
Edited from a 1977 posting to rec.ww. I fear that I no longer have details of the actual source.
'.........................................................an OSHA required data sheet..... lists the safety requirements of hazardous material. It states therein that the Least Explosion Level (LEL) for wood dust is 40 grams per cubic meter of air.
If there are 453.5 grams in a pound and 35.31 cubic feet in a cubic meter then this calculates out to 0.0025 pounds per cubuc foot of air.
If you have a typical 1-1/2 horsepower dust collection unit and nothing else connected to it you can probably draw 1100 cfm according to the manufacturers rating. So, at 0.0025 pounds per cubic foot of air, you are going to need to sand off 2.75 pounds of wood per minute to reach the minimum dust explosion level in your ductwork.
How does that relate to in the real world? The book says red oak has a density of 43 to 63 pounds per cubic foot. If we use 53 pounds as the average and divide 2.75 pounds by 53 pounds per cubic foot we get 0.052 cubic feet of oak to reach LEL in our ductwork. If we were sanding a red oak 4" x 4" on the sander, we would have to sand away .468 feet of 4x4 per minute or a little over 5-1/2 inches if 4x4 oak per minute to reach LEL. Unless you have the Tim Allen memorial sander in your shop, I don't think that a home size workshop can produce enough dust to get to the minimum explosive level.
Now, When you start moving thousands of pounds per minute of wood dust through a dust collection system, you can relate it to a grain elevator.'
Jeff G
-- Jeff Gorman, West Yorkshire, UK Email address is username@ISP username is amgron ISP is clara.co.uk Website www.amgron.clara.net
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Finally, quantitative proof! (Good analysis) :-) Thanx Renata
wrote:

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Please do your homework and read the archived posts on this subject. The possibilty of a wood dust explosion in a home workshop are practically less than nil (perhaps even lower!)
As for your large static charges on plastic, any high school physics teacher could tell you the same thing about his classroom Van de Graff generator and all it could do was make his hair stand on end. No explosions and no student deaths by electrocution.
And the hugh charge built up on my body when I shuffle across the room in winter doen't set the house on fire when i discharge it to the door knob. (It does make me jump though--and that's all the charge on ductwork in the shop will do too.)
Of course you are right that such charges could fire a microprocessor chip--that's why they're often sold with a wrist strap grounding cable so the person installing them want accidentally ruin them.
Dust collection in a shop only needs grounding if static discharges from ductwork to the human operator are undesired. There is NO danger of a "grain elevator" type explosion--unless your shop is extremely large and full of tons of dust with hugh volumes of airborne particles.
--
Regards,

Benoit Evans
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wrote:

school, I did connect a Van de Graff generator to a doorknob (teenage pranks) and after seeing that I could zap an unsuspecting victim with about a 7" "lightning bolt" (ESD) decided to add licopodium powder to the prank. It IS impressive and it DOES ignite and is reminiscent of flash powder of years gone by. For those unfamiliar with licopodium powder, it is about the same fineness as flour and would represent a fine dust explosion or ignition.
As for permanent harm, a Van de Graff generator doesn't generate sufficient static charge for that, though lightning does.
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On Friday, December 5, 2003 at 4:28:31 PM UTC-5, Ian Dodd wrote:

I have ordered tools from for my husband and he was happy with them.
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On Thu, 17 Dec 2015 09:52:55 -0800, mscottgruber wrote:

I did - a long time ago. The company has been sold to Woodworkers Supply in Casper. I've also ordered from them, but again, it was a long time ago. Used to stop and browse their store any time we drove through Casper.
So any old reviews you see about Leichtung no longer apply. But I never had any problems with Woodworkers Supply. But it may have changed hands as well - I don't know.
--
Nobody expects the Spanish Inquisition!

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