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explosive situation?
My hi-tech DC system for my TS consists of a shop-vac connected to a 30
gallon plastic dust bin. The dust bin is then connected to the bottom of my contractor saw with a flexible aluminum 4" dryer vent. I normally have the back of the saw closed off with 1/4" plywood and this system works fairly well. Yesterday I needed to clean out the inside of the saw, so I unplugged the saw and turned on the shop vac. I then bent over and pushed the sawdust into the chute on the bottom of the saw. While I was doing this everytime my hand partially blocked the hole leading to the dryer vent it would compress slighty and touch the frame of the saw. That is where I saw the spark. A tiny spark between the leg of the saw and the aluminum vent connected between the plastic dust bin and the plastice adapter on the saw. In theory, static can ignite fuel vapors or gases, but wood dust? Both the shop-vac and TS are plugged into properly wired 3-prong outlets but this is only really grounding them in case of a motor failure. Should I somehow ground this DC system or just ignore the static? |
explosive situation?
"RayV" wrote in message
theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. |
explosive situation?
Upscale wrote:
"RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. -- Thank you, "Then said I, Wisdom [is] better than strength: nevertheless the poor man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16 |
explosive situation?
"Dhakala" wrote in message
oups.com... dnoyeB wrote: Upscale wrote: "RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. http://www.ydr.com/newsfull/ci_3604224 No one says it can't happen in an industrial situation. To my knowledge, no one has ever documented a case of a dust explosion in a home workshop. If there is such documentation, I'm open to seeing it, but AFAIK, it has never been produced here when this topic has surfaced. todd |
explosive situation?
I should have so much dust and that big of a collector!!
"Dhakala" wrote in message oups.com... dnoyeB wrote: Upscale wrote: "RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. http://www.ydr.com/newsfull/ci_3604224 |
explosive situation?
"RayV" wrote in message oups.com... A tiny spark between the leg of the saw and the aluminum vent connected between the plastic dust bin and the plastice adapter on the saw. In theory, static can ignite fuel vapors or gases, but wood dust? Both the shop-vac and TS are plugged into properly wired 3-prong outlets but this is only really grounding them in case of a motor failure. Should I somehow ground this DC system or just ignore the static? A while back an engineer, MIT I think, wrote an article on the subject for one of the ww mags (sorry, don't remember which one). He essensially concluded (supported by formulas & math) that you can't move enough air thru a 4" pipe with a dust collector (let alone a shopvac) to generate enough static charge to sustain a spark of sufficient duration to ignite wood dust. But urban legends die hard. Anyway, the spark you saw is the same as the one you see when you slide out of your car and touch the key to the door. And if you touch the door with your finger instead of the key you'll feel it. If you find that discharge thru your finger annoying, that's about the only reason to ground non-metalic dust collection pipe. You can ground the metal dryer pipe if it makes you feel better but you will still be building static charge in the non-metalic shop vac hose. And I'll bet you never worried about that when you were using the shopvac for other things. |
explosive situation?
Ray,
You might want to run a wire between the aluminum flex hose and the metal leg of your table saw. - MB |
explosive situation?
There is a possibility that one of the two machines has a faulty ground
connection and you are seeing the connection of an ungrounded machine to a grounded one. Check to ensure there is zero-5 ohms resistance between the saw chassis and the shop-vac motor frame when they are plugged in...... or....There are kits available to ground plastic 4" hose to discharge static. Guess it could happen in aluminum pipe too. Wrap a copper ground wire around the pipe and screw the ends of the wire to the saw and DC frame. Jim "RayV" wrote in message oups.com... My hi-tech DC system for my TS consists of a shop-vac connected to a 30 gallon plastic dust bin. The dust bin is then connected to the bottom of my contractor saw with a flexible aluminum 4" dryer vent. I normally have the back of the saw closed off with 1/4" plywood and this system works fairly well. Yesterday I needed to clean out the inside of the saw, so I unplugged the saw and turned on the shop vac. I then bent over and pushed the sawdust into the chute on the bottom of the saw. While I was doing this everytime my hand partially blocked the hole leading to the dryer vent it would compress slighty and touch the frame of the saw. That is where I saw the spark. A tiny spark between the leg of the saw and the aluminum vent connected between the plastic dust bin and the plastice adapter on the saw. In theory, static can ignite fuel vapors or gases, but wood dust? Both the shop-vac and TS are plugged into properly wired 3-prong outlets but this is only really grounding them in case of a motor failure. Should I somehow ground this DC system or just ignore the static? |
explosive situation?
On 27 Mar 2006 09:15:12 -0800, "Dhakala"
wrote: dnoyeB wrote: Upscale wrote: "RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. http://www.ydr.com/newsfull/ci_3604224 At the time the article was written, static electricity as a cause was purely speculation. They also indicated a hot ember could have started the fire. Mythbusters would be a good venue for testing this theory. I seriously doubt that static electricity has enough energy to ignite a dust explosion. An electric arc or hot piece of metal contains significantly more energy to start the required reaction. +--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+ |
explosive situation?
On 27-Mar-2006, Mark & Juanita wrote: I seriously doubt that static electricity has enough energy to ignite a dust explosion. That depends on how much static and how fine the dust. While I doubt that walking across a carpet and then touching a dust collector would do it, the kind of dusts that can be found in silos of anything (and bulk carriers being loaded etc) in conjuction with a significant static source could do it. Continuously running equipment can continuously generate static. Mike |
explosive situation?
"Woodhead" wrote in message ... There is a possibility that one of the two machines has a faulty ground connection and you are seeing the connection of an ungrounded machine to a grounded one. Check to ensure there is zero-5 ohms resistance between the saw chassis and the shop-vac motor frame when they are plugged in...... or....There are kits available to ground plastic 4" hose to discharge static. Guess it could happen in aluminum pipe too. Wrap a copper ground wire around the pipe and screw the ends of the wire to the saw and DC frame. I'd have a whole lot more confidence in your method if they didn't put (insu/iso)lation on conductors to keep them from grounding. Testing for stray voltage or bad ground is a good idea in the conducting saw. |
explosive situation?
dnoyeB wrote: I'd like to see that one on myth busters. Myth Busters is pseudo-science at BEST. They raise more questions than they answer. |
explosive situation?
"Gus" wrote Myth Busters is pseudo-science at BEST. They raise more questions than they answer. But this group is solidly science-based, aren't we? After all, we've a wealth of experience ... umm make that a large vocal group that believes they have solid factual data, with a minority that provides verifiable data, sound data analysis and (usually) a well written presentation of that analysis. Read the FAQ. The MYTH of static-induced home dust collection system explosions is well documented. Get to know Google ... in fact, make Google your friend. The MYTH of static-induced home dust collection system explosions is well documented. Especially important is to read the rec.woodworking archives, searching for dust + explosion. Rick |
explosive situation?
Woodhead wrote: ....There are kits available to ground plastic 4" hose to discharge static. you cannot ground plastic pipe. plastic is an insulator. the kits are strictly for suckers. |
explosive situation?
Rick M wrote: "Gus" wrote Myth Busters is pseudo-science at BEST. They raise more questions than they answer. But this group is solidly science-based, aren't we? After all, we've a wealth of experience ... umm make that a large vocal group that believes they have solid factual data, with a minority that provides verifiable data, sound data analysis and (usually) a well written presentation of that analysis. Read the FAQ. The MYTH of static-induced home dust collection system explosions is well documented. So, by your logic, if it's in the FAQ, it MUST be true. Remind me to contact you next time I have swamp land for sale. |
explosive situation?
"Gus" wrote So, by your logic, if it's in the FAQ, it MUST be true. Factual evidence supports the FAQ entry in question. The absence of any contrary data presented as a counterpoint by you simply illustrates your emotional denial, rather than supporting your opinion. If you have factual evidence, kindly present it. If not, feel free to believe what you will, but don't take offense if I don't share your beliefs. Rick |
explosive situation?
I've searched the wreck archives, osha site, googled the web... all I
can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." "PVC cannot be effectively grounded..." What I can't find are any specs or hard facts. If I rub my feet on the carpet and touch a doorknob with a handful of sawdust will my hand explode? Without any facts I'm extremely unlikely to believe that a home shop DC system can explode. Didn't one of Adolf's boys say, "if you repeat it often enough it will become true"? Case in point: Just about every driver's manual I have read (ok, two) states that for a car with a manual transmission...you should put the car in reverse when parked facing downhill and in first when parked facing uphill. This is totally idiotic! That advice is based on the false assumption that the engine can only rotate in one direction. But still it is part of driver's ed training. Doesn't anyone beLIEve in facts anymore? How much dust in what concentration is required for an explosion? How much of a static charge would be required to ignite that dust? I only found one link that supposedly had data available but the link is now dead. |
explosive situation?
On 28/03/2006 3:56 PM, RayV wrote:
I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." When I was younger, I worked a couple of summers on Great Lakes boats carrying wheat. That dust can definitely explode: http://www.fireworld.com/magazine/grainperil.html http://osuextra.okstate.edu/pdfs/CR-1737web.pdf Under the right conditions and in the right amounts, sawdust is no different: http://www.cep.ca/health_safety/files/wooddust_e.html http://www.hse.gov.uk/pubns/wis1.pdf http://www.healthandsafety.co.uk/hswd.html http://www.dol.state.nc.us/osha/etta...s/CombDust.pdf And on and on... |
explosive situation?
Best person to ask is your local fire department. They might have
some good stories to tell. Fuel + Oxygen + Heat (spark) = Fire I think a DC can catch fire, although I'm not sure how likely it is to happen. On 28 Mar 2006 12:56:03 -0800, "RayV" wrote: I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." "PVC cannot be effectively grounded..." What I can't find are any specs or hard facts. If I rub my feet on the carpet and touch a doorknob with a handful of sawdust will my hand explode? Without any facts I'm extremely unlikely to believe that a home shop DC system can explode. Didn't one of Adolf's boys say, "if you repeat it often enough it will become true"? Case in point: Just about every driver's manual I have read (ok, two) states that for a car with a manual transmission...you should put the car in reverse when parked facing downhill and in first when parked facing uphill. This is totally idiotic! That advice is based on the false assumption that the engine can only rotate in one direction. But still it is part of driver's ed training. Doesn't anyone beLIEve in facts anymore? How much dust in what concentration is required for an explosion? How much of a static charge would be required to ignite that dust? I only found one link that supposedly had data available but the link is now dead. |
explosive situation?
Doug Payne wrote: On 28/03/2006 3:56 PM, RayV wrote: I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." When I was younger, I worked a couple of summers on Great Lakes boats carrying wheat. That dust can definitely explode: http://www.fireworld.com/magazine/grainperil.html http://osuextra.okstate.edu/pdfs/CR-1737web.pdf Under the right conditions and in the right amounts, sawdust is no different: http://www.cep.ca/health_safety/files/wooddust_e.html http://www.hse.gov.uk/pubns/wis1.pdf http://www.healthandsafety.co.uk/hswd.html http://www.dol.state.nc.us/osha/etta...s/CombDust.pdf And on and on... sure, in big industrial facilities with dust systems moving tons of material per hour the risk is real, and the measures taken to control static discharge are vital. in the home shop with probably a maximum 5hp collector sucking dust from at most a few machines at once through probably 6" maximum pipe you aren't going to make a big enough static spark to get ignition. if you can present evidence to the contrary I'll nominate you king of the wreck. |
explosive situation?
"Doug Payne" wrote in message
... On 28/03/2006 3:56 PM, RayV wrote: I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." When I was younger, I worked a couple of summers on Great Lakes boats carrying wheat. That dust can definitely explode: http://www.fireworld.com/magazine/grainperil.html http://osuextra.okstate.edu/pdfs/CR-1737web.pdf Under the right conditions and in the right amounts, sawdust is no different: http://www.cep.ca/health_safety/files/wooddust_e.html http://www.hse.gov.uk/pubns/wis1.pdf http://www.healthandsafety.co.uk/hswd.html http://www.dol.state.nc.us/osha/etta...s/CombDust.pdf And on and on... Flour would be another prime example. I'm sure we're all familiar with the many reports of kitchen dust explosions when flour particles became airborne and explosively ignited from a lit burner on the stove. todd |
explosive situation?
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explosive situation?
Subject
What everybody is dancing around is "LEL" or "Lower Explosive Limit". It is that point where the dust volume in the air WILL explode. An entire industry exists to provide instrumentation to measure "LEL" for various products. There are published tables of LEL values and are usually available from the instrumentation manufacturer. Been there, done that, but that was a while ago. Lew |
explosive situation?
On Wed, 29 Mar 2006 00:20:55 GMT, Lew Hodgett
wrote: What everybody is dancing around is "LEL" No, not at all. Fill a reasonable router extractor hose with typical levels of fine larch dust, initiate it pyrotechnically and I have no doubt at all that you can have your very own wood dust explosion. You'll not do it from static though. That's the demonstrable case where you can't initiate it. or "Lower Explosive Limit". It is that point where the dust volume in the air WILL explode. No, far from it. It's the lower limit for where the mixture _can_ explode. Below this it's impossible to explode, at this limit it's barely possible. It isn't especially likely (depending on other conditions regarding ignition sources) and it certainly isn't any sort of spontaneous ignition as suggested by your emphatic "WILL explode" comment. |
explosive situation?
I previously wrote:
It is that point where the dust volume in the air WILL explode. As written, not true. It should have read: It is that point where the dust volume in the air WILL explode IF an ignition source is provided. Blame it on a lazy typist, ME. Lew |
explosive situation?
The RayV entity posted thusly:
I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." "PVC cannot be effectively grounded..." snippage Doesn't anyone beLIEve in facts anymore? How much dust in what concentration is required for an explosion? How much of a static charge would be required to ignite that dust? Yes, I do believe in facts. No idea of the concentrations or how hot a spark it would take to set it off. I was, however, rudely awakened one Sunday morning in North Vancouver when a grain elevator about 5 miles from me was subject to a grain dust explosion. That was in the mid-70s or so, if you feel like looking it up. I also participated in several experiments in which we ignited clouds of flour, cornstarch, and sawdust. No real explosion, because it was a small and unconfined cloud, but it was, nonetheless, spectacular. |
explosive situation?
Oleg Lego wrote:
The RayV entity posted thusly: I've searched the wreck archives, osha site, googled the web... all I can find are anecdotal statements. "sawdust can explode..." "any combustible material in dust form is explosive..." "PVC cannot be effectively grounded..." snippage Doesn't anyone beLIEve in facts anymore? How much dust in what concentration is required for an explosion? How much of a static charge would be required to ignite that dust? Yes, I do believe in facts. No idea of the concentrations or how hot a spark it would take to set it off. I was, however, rudely awakened one Sunday morning in North Vancouver when a grain elevator about 5 miles from me was subject to a grain dust explosion. That was in the mid-70s or so, if you feel like looking it up. I also participated in several experiments in which we ignited clouds of flour, cornstarch, and sawdust. No real explosion, because it was a small and unconfined cloud, but it was, nonetheless, spectacular. My mother couldn't explain the seemingly rapid disappearance of her cache of corn starch when I, unbeknownst to her, would sneak baggies of it down to the creek bed to huff it out my mouth at a candle held before my face--much to my inner pyromaniac's delight. er -- email not valid |
explosive situation?
In article . net,
Lew Hodgett wrote: Subject What everybody is dancing around is "LEL" or "Lower Explosive Limit". It is that point where the dust volume in the air WILL explode. An entire industry exists to provide instrumentation to measure "LEL" for various products. There are published tables of LEL values and are usually available from the instrumentation manufacturer. Been there, done that, but that was a while ago. Lew No disrepect intended, but I've read dozens if not hundreds of MSDS and had some training as well, and I have never seen a reference to LEL/UEL that was not for gas or vapor concentration in air. In fact, for dust any LEL would vary with the particle size. -- Larry Wasserman Baltimore, Maryland |
explosive situation?
In article ,
Enoch Root wrote: ...snipped... My mother couldn't explain the seemingly rapid disappearance of her cache of corn starch when I, unbeknownst to her, would sneak baggies of it down to the creek bed to huff it out my mouth at a candle held before my face--much to my inner pyromaniac's delight. er -- email not valid That must have been fun, but how many times were you successful igniting it with a static discharge? -- Larry Wasserman Baltimore, Maryland |
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explosive situation?
wrote in message ... In article , Andy Dingley wrote: ...snipped... No, the situation is exactly the same. It's a question of max possible discharge energy vs. minimum energy needed to initiate a dust explosion. These don't change for industrial scale wood dust collectors - the volumes get bigger, the densities don't. Can you support that statement? At any rate, in an industrial setting the greater volume of air and dust being moved would have the potential to create a more powerful static discharge. And all the comparison to grain silos; The dust that creates the danger of an explosion in them is MUCH finer than the sawdust created in the typical wood shop operation, except perhaps for sanding dust. -- Larry Wasserman Baltimore, Maryland Agreed, but ... still don't throw a box of sanding dust into the wood stove if there's still a small fire in there. Took a LONG time to grow back eyebrows! Woof! Pop |
explosive situation?
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explosive situation?
OK, dust can explode! But I'm not putting a candle in my DC anytime
soon. http://jchemed.chem.wisc.edu/JCEsoft...cca7dust1.html |
explosive situation?
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explosive situation?
On 29-Mar-2006, Mark & Juanita wrote: If your dust collector can generate a static spark with equivalent energy to a lightning bolt, some wimpy little wire wrapped around the pipe isn't going to help you anyway. But that wimpy little wire will bleed off the charge before it can get as big as a lightning discharge. While I doubt that an explosion in a home DC will occur - how about a fire? The only difference between a fire and an explosion is the rate of combustion. Mike |
explosive situation?
In article , Michael Daly
wrote: While I doubt that an explosion in a home DC will occur - how about a fire? From static electricity? Bwahahahahahaha! |
explosive situation?
In article ,
Mark & Juanita wrote: On 27 Mar 2006 09:15:12 -0800, "Dhakala" wrote: dnoyeB wrote: Upscale wrote: "RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. http://www.ydr.com/newsfull/ci_3604224 At the time the article was written, static electricity as a cause was purely speculation. They also indicated a hot ember could have started the fire. Mythbusters would be a good venue for testing this theory. I seriously doubt that static electricity has enough energy to ignite a dust explosion. I guarantee you that static electricity _does_ have enough energy. Under the _right_ circumstances. Now, as for sawdust, in a home/hobby shop setting, it is *EXTREMELY*UNLIKELY* that the 'right circumstances' will occur. |
explosive situation?
On Sat, 01 Apr 2006 14:16:34 -0000, (Robert
Bonomi) wrote: In article , Mark & Juanita wrote: On 27 Mar 2006 09:15:12 -0800, "Dhakala" wrote: dnoyeB wrote: Upscale wrote: "RayV" wrote in message theory, static can ignite fuel vapors or gases, but wood dust? Wood dust in the right proportions can be explosive. You can probably find more information on it in the rec archives, but I'm sure quite a few people will respond with additional information. I'd like to see that one on myth busters. http://www.ydr.com/newsfull/ci_3604224 At the time the article was written, static electricity as a cause was purely speculation. They also indicated a hot ember could have started the fire. Mythbusters would be a good venue for testing this theory. I seriously doubt that static electricity has enough energy to ignite a dust explosion. I guarantee you that static electricity _does_ have enough energy. Under the _right_ circumstances. I should have been more specific. My sentence above should have read, "I seriously doubt that static electricity has enough energy to ignite a wood dust explosion from the dust that would be generated in a typical home woodshop." Now, as for sawdust, in a home/hobby shop setting, it is *EXTREMELY*UNLIKELY* that the 'right circumstances' will occur. +--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+ |
explosive situation?
On Sat, 01 Apr 2006 09:47:58 -0700, Mark & Juanita
wrote: This might help: http://www.chemeng.ed.ac.uk/~emju49/.../deh/deh4.html I guarantee you that static electricity _does_ have enough energy. Under the _right_ circumstances. I should have been more specific. My sentence above should have read, "I seriously doubt that static electricity has enough energy to ignite a wood dust explosion from the dust that would be generated in a typical home woodshop." Now, as for sawdust, in a home/hobby shop setting, it is *EXTREMELY*UNLIKELY* that the 'right circumstances' will occur. |
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