I have done quite a bit of research on the subject of dust collection mainly because I am not nearly satisfied with mine. It all gets pretty complicated quite fast but there are a couple of big principles which effect efficiency and effectiveness.
The main thing is the volume of air moved. More is better. Now the amount of air moved through a duct depends on the cross sectional area of the pipe and the resistance to the flow of the air. There are other variables of course but these are the big ones. Cross sectional area is the area of the cross section of the duct. This is pretty obvious in a square duct. A square duct 4 inches by 4 inches has a cross sectional area of 4 X 4 inches or 16 square inches. A square duct 3 X 3 inches has an area of 9 square inches almost half the cross sectional area. Round is a little different calculation but it is essentially the inverse square law. The point is that the most air you can draw through the system will be determined by the narrowest lumen. Where you increase the dimension down stream you reduce the air speed because you are drawing the same volume of air which started in the smaller duct through a larger duct effectively slowing the air flow in the duct with the larger area. This can and will cause at least some of the particles to rain out of suspension and can contribute to filling the pipe. Where you are running more than one outlet then the terminal outlets can be smaller than the collecting duck with less loss because the larger trunk is collecting from the two smaller ones, your calculations then should take into account the usual number of peripheral tubes so that the trunk is roughly equivalent to the sum of the usual open peripheral pipes. The next consideration is the resistance of the ducts. Mostly this is a function of the material they are made of and anything that contributes to turbulence. Flexible ribbed hose offers in the range of four times the resistance per running foot of a smooth walled vessel. 4 feet of flex hose offers as much resistance as 16 feet of smooth walled duct. You want to keep your flexible runs as short as possible and preferably at the distal end of the duct. Joints and unions and 'Ts' and elbows all contribute to increased turbulence in the air stream. You want to make elbows as wide sweeping as you can and you want to minimize interior roughness at joints, screws which penetrate the duct and all that for optimal efficiency. Now if I had my druthers it would be an Ecogate controller with power blast gates and Nordfab Quickfit ducting with the neoprene pipe clamps. The ends of the pipes are rolled back so there isn't anything to catch the air flow. It is expensive like crazy though. The ecogate controller senses when and what machine you turn on and opens that blast gate and turns on the dust collector. It senses when you turn off the last machine and runs the system long enough to clear the debris from the ductwork before shutting down and closing that blast gate. So, run as large of duct as your blower will accept and if you must reduce do so as close to the terminus as you practically can with as little flexible hose as you can reasonably get away with. There is a little debate about the requirement for grounding against static electricity. Not much debate but some. Mine isn't presently well grounded, it does produce static, sometimes quite a bit. I believe it is prudent to ground the ducting. Hope this helps. Dale Leavens, Cochrane Ontario Canada [EMAIL PROTECTED] Skype DaleLeavens Come and meet Aurora, Nakita and Nanook at our polar bear habitat. ----- Original Message ----- From: Matt To: [email protected] Sent: Friday, December 07, 2007 1:25 PM Subject: [BlindHandyMan] running pipe for dust collection Hello, I am moving up to bigger pipe with my dust sucker. I would like to open up your minds on ideas having to do with the idea of dust collection. Have you a system set up for this? What did you do? What did you redesign, why and all that? I have already listened to many people debate the idea of theoretical dust explosions from static and such, So if you wish, we can skip that. I ran copper wire after listening to all that and still don't know if it was for good, bad or indifference. It is done. I had run 3 inch pipe to my sucker back when I got here, because my original pipes were lost in the move, and I didn't know what to start with. I have since decided that this was too small, so i bought 4 inch. The four inch matches the gutter flexi pipe I have coming off the machine. It matches exactly, so the new 4 inch won't fit inside the guttering. I may match it up and duct until I can get a matching rubber reducer or whatever. Do you think I should come off my 4 inch with the 3 inch I already have, or should I just 4 inch it all the way? I thought about going to each machine with gate valves, but really, I am just one person, who uses one tool at a time. That's a bit of over kill. Anyway, I will look forward to the discussion. My dust sucker is a machine I bought second hand at a resale place. Has cloth bags on top and bottom of a metal frame and it really moves some air! It is 220. I forget the horse power. Matt [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
