PVC pipe for dust collection?

[scsmith42]

In researching pro's and cons for using PVC pipe for dust collection, I ran across this essay. Very fascinating reading, from someone that is well versed with the physics behind it.

http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html

Thought that I'd share it for others to learn from.

Scott

 

[nelsone]

Looks like an interesting read. Don't have time right now. Thanks for the link!

 

[McRabbet]

This link has been in our Link Library for some time. It is a good article, Scott -- thanks for bringing it up.

 

[merrill77]

I ran across that as well - a few years back when I was seriously researching DC systems. As an electrical engineer, I was able to follow most of the discussion.

One thing struck me about the discussion. If anyone here is enough of a gearhead to have done any serious research on how carburetors work, it is actually pretty hard to get gasoline to explode (despite what is shown on TV). The mix created by the carb has to have just the right air-to-fuel ratio in order to explode. If you've ever rebuilt or tuned a carburetor, then you know how easy it is to get a carb far enough out of adjustment that the engine won't start. And the ignition system is designed to deliver exactly the right spark. Given all that - think how much harder it must be to get sawdust to explode...without a carefully engineered ignition source!

Given the stark contrast with the odds of injury on other power tools (esp the table saw), any effort spent preventing an explosion in a home-shop DC duct is pretty much wasted, IMHO.

just my 2c
Chris

 

[MrAudio815]

Thanks for pointing it out.

I guess I need to look into that library of ours.

 

[scsmith42]

This link has been in our Link Library for some time. It is a good article, Scott -- thanks for bringing it up.

Rob, thanks for letting us know. There seems to be a problem with the library though, when I click on "link library" in your post I get a blank page.

 

[McRabbet]

Rob, thanks for letting us know. There seems to be a problem with the library though, when I click on "link library" in your post I get a blank page.

Must be at your end -- I clicked on the quoted link in your post and opened it in a new tab just fine. I'm using IE7.

 

[cpowell]

Thanks for an interesting read on a sleet/snow/yucky weather day! :icon_thum

Despite what is written and read I'm afraid the myths will persist. But I'll run pvc one day when I get tired of flex hose and do something about it.


Chuck

 

[Travis Porter]

I get the same thing as Scott, a blank page, and I am running IE 8.

 

[RandyJ]

The link works for me in Firefox 3.6. Didn't try IE. Did I say how much I hate IE????:tongue2::kamahlitu:realmad:

 

[McRabbet]

I get the same thing as Scott, a blank page, and I am running IE 8.

Try this link and scroll down to the Title starting "Dr. Rod Cole..."

 

[Alan in Little Washington]

I ran across that as well - a few years back when I was seriously researching DC systems. As an electrical engineer, I was able to follow most of the discussion.

One thing struck me about the discussion. If anyone here is enough of a gearhead to have done any serious research on how carburetors work, it is actually pretty hard to get gasoline to explode (despite what is shown on TV). The mix created by the carb has to have just the right air-to-fuel ratio in order to explode. If you've ever rebuilt or tuned a carburetor, then you know how easy it is to get a carb far enough out of adjustment that the engine won't start. And the ignition system is designed to deliver exactly the right spark. Given all that - think how much harder it must be to get sawdust to explode...without a carefully engineered ignition source!

Given the stark contrast with the odds of injury on other power tools (esp the table saw), any effort spent preventing an explosion in a home-shop DC duct is pretty much wasted, IMHO.

just my 2c
Chris

Yup and gasoline is a hydrocarbon with a high vapor pressure- means burns easily, it vaporizes easily, and the vapor is more explosive that the liquid. As Rod Cole pointed out the dust particles must be just the right size, in a relatively static cloud (not moving at 4000 fpm), and at a concentration much higher than possible with the air velocities in a typical DC, for a fire to propagate even if static could ignite it.

I have been trying to kill that urban legend for years, but it keeps coming up time after time in many forums, and of course suppliers are more than happy to keep the legend alive and sell you their grounding kits.

If you want to do a neat demonstration though, put a length of hose on the small end of a funnel so you can blow through it. Put a few tablespoons of corn starch in the funnel. Hold a lighted match over the wide mouth of the funnel, while you blow through the hose. As you blow the dust is ignited by the match and the air causes it to become a large fireball so don't aim the funnel at anybody or anything flammable.

:kamahlitu

 

[MrAudio815]

Corn Starch is Flammable?

Awesome~! Ha ha ha.

Aqua Net Hair spray is very flammable, it works well with a Potato and a PVC Cannon with flint striker.

 

[Gotcha6]

The facts about upper and lower explosive limits as they are called would dispel the myth here. The problem is that once the spark finds that magic window of opportunity it will perpetuate itself. However, I've always felt that the static grounding issue was more for the comfort of not getting shocked every time I touch it. BTW, my DC is piped in PVC, is not bonded & I don't have a problem with static - yet.

 

[Travis Porter]

Try this link and scroll down to the Title starting "Dr. Rod Cole..."

Travis Porter, you do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

 

[Mike Wilkins]

Not sure what the link go to, but Fine Woodworking magazine had an article in one of the annual Tools and Shops issues that discussed the pros and cons of PVC for dust collection. Basically the article states that since PVC is a non-conductive material, like an electrical insulator. Sounds like a neat experiment for the Mythbusters guys to try. I have been using PVC in my shop for 5-6 years without a hitch. I have less than 30 feet of total run, with blast gates at the pick-up points and it has worked well. The jointer/planer machine is closest to the collector since it generates the most dust/chips; the router table is furthest away. Just remember to close any gates that are not in use.
I did not permanently attach the pipes/joints just in case I need to make some changes. Just used Silicone sealant and 3/8" sheet metal screws to attach wyes and blast gates.
Hope this helps.

 

[Alan in Little Washington]

Not sure what the link go to, but Fine Woodworking magazine had an article in one of the annual Tools and Shops issues that discussed the pros and cons of PVC for dust collection. Basically the article states that since PVC is a non-conductive material, like an electrical insulator. Sounds like a neat experiment for the Mythbusters guys to try. I have been using PVC in my shop for 5-6 years without a hitch. I have less than 30 feet of total run, with blast gates at the pick-up points and it has worked well. The jointer/planer machine is closest to the collector since it generates the most dust/chips; the router table is furthest away. Just remember to close any gates that are not in use.
I did not permanently attach the pipes/joints just in case I need to make some changes. Just used Silicone sealant and 3/8" sheet metal screws to attach wyes and blast gates.
Hope this helps.

I believe they already did something similar- they tried to make a PVC static canon. They couldn't get a spark sufficient to ignite anything.

ditto on the silicone. If you have some leaks (you can usually hear them) or just want to make sure, just put a tiny bead of silicone (not latex) on the outside (not inside) at each fitting. Between suction pressure and mild adhesion the silicone stays in place, but you can easily rub cured silicone off with your fingers when you want to reconfigure your ducting.

Oh, and by the way, that FWW article was so full of crap. So many errors, errors of omission, and downright bad advise and pics of a terrible installation.