Another Ponder comes in

I've been a long time lurker and sometimes poster on the Pond. I thought that I would register and make at least enough posts to get to be a "regular member".

As some Ponders may remember, I am a professional dust control engineer. Since finding the pond, I have done considerable reseach on the subject of home shop dust collection and the "dangers" of wood dust. In the future, I will start posting some DC information you may find interesting. I don't want to step on the toes of a certain individual who has done considerable work to provide information on woodshop dust collection, but I would like to clarify some misconceptions that have been widely distributed.

I hope this site becomes as active, interesting and most of all, as civil as BP has been these past years. There are quite a few wood forums out here, but BP has always had a warm friendly atmosphere with no insults to man nor tools. I hope this site will as well.
:)

Doug

Hi Doug,
Welcome to the Creek. Like yourself, I lurked at the pond for a long time, but seldom posted. I think you'll like it here.

Lets go ahead and get something started about dust collectors.
In a one man shop where you have a 1.5 HP dust collector with 4" and 2" PVC lines going to a 4" PVC main header, is it necessary to ground the PVC lines?

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Originally posted by Doug Edwards
. . . I am a professional dust control engineer. Since finding the pond, I have done considerable reseach on the subject of home shop dust collection and the "dangers" of wood dust. In the future, I will start posting some DC information you may find interesting. I .... would like to clarify some misconceptions that have been widely distributed.

Doug

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Welcome, Doug.

Some of the opinions expressed have been rather overbearing and as a EE, I did find fault with some of the reasoning about static build-up.

That said, I have a question about lift. I want to install a dust cyclone collector mounted near the ceiling (due to space limitations). My ceiling is 10' high. I want to run the main trunk down the center of the room with drops (2 or 3) from it. How well can I expect it to work with that kind of lift involved?

Thanks.

Ted

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Originally posted by Von
Hi Doug,
Welcome to the Creek. Like yourself, I lurked at the pond for a long time, but seldom posted. I think you'll like it here.

Lets go ahead and get something started about dust collectors.
In a one man shop where you have a 1.5 HP dust collector with 4" and 2" PVC lines going to a 4" PVC main header, is it necessary to ground the PVC lines?

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Jeez, the first question you ask has to be one of the most controversial. Any particulate flowing through a non-conductive duct will create a static charge. This charge may become strong enough to cause a discharge. The discharge can give you a nasty shock. This may be a good enough reason to ground the ductwork. The best method I've seen is to drive conductive screws into the duct from the outside about every 6" - 8" and connect to a grounded copper wire (14 ga or heavier). The screws do not have to penetrate into the interior of the duct, but should pass completely through the PVC.

The controversial part is will the spark cause a dust fire/ explosion. The best answer I have found is that it is HIGHLY unlikely. To create an explosion you need a high enough dust concentration (and small enough particulate) to create an explosible atmosphere and an energy source strong enough to ignite the dust/air mixture. In general, there is normally not enough dust in the ductwork to create an explosable atmosphere. Several sources have stated that the spark produced from PVC is not strong enough to ignite wood dust. But, if the dust is fine enough, concentrated enough and the spark stong enough and the planets are all aligned in a certain way and you are very unlucky, it might ignite. Probably not.

The most likely point in the system for an explosion to occur is inside the dust collector. But I haven't heard any chatter about using conductive filters explosion vents, or any of the other anti-static measures used on commercial dust collectors. It (the most likely unlikely ignition site) has been a non-issue on the web.
In short, the chance of an exposion in a home dust collection system is about the same as a metor strike on your jointer.

However, my PVC system is grounded. This is because I can't stand those static shocks that PVC can give you. I don't worry about a fire, explosion, or meteors.

Glad to have you here. I'll be nice and not ask any DC questions, at least for a day or two. ;)


Bob

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Originally posted by Ted Shrader

I have a question about lift. I want to install a dust cyclone collector mounted near the ceiling (due to space limitations). My ceiling is 10' high. I want to run the main trunk down the center of the room with drops (2 or 3) from it. How well can I expect it to work with that kind of lift involved?

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Ted,

In general, lift is discounted in the design of dust collection systems. Since the weight of material is usually much less than the weight of the air moved, the calculations for determining system losses and power requirements do not include the weight of the dust. More important is the velocity of the air in the duct. This is critical in the success of the system. The generally accepted conveying velocity for wood is 3500fpm. This applies horizontally or vertically. So if you are running at least 685 cfm in a 6" duct or 305 cfm in a 4" duct you are OK. BTW assume your dust collector moves about 50% or less from the rated volume.

Just in case, it's not a bad idea to put a clean out acces at the bottom of a vertical run. This could be as simple as a way to easily remove the bottom elbow or as complicated as an access door to reach inside the duct.

BTW This is what an exploding dust collector looks like.

You just got my attention Doug,

Jerry

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Welcome and dive right in - the water is fine
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Doug, We will look forward to using your expertise. Thanks for joining us.

I've been lurking around the Pond and a few other sites trying to get some general knowledge from the folks who really know their stuff. Glad to see you here.

Glad to have one more here.

Lee

Happy to see you in the Creek and will look forward to your input.

Welcome, Doug. Someone with your expertise is sorely needed. I'm sure that you will be innudated with questions. :)