<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Cyclone Dust Collection</title></head><body> <div>Hi Terry,</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1">I recently purchased a 5 hp cyclone dust collector/separator for my woodworking shop. It has yet to be delivered. I would like to solicit input from any of you folks that have used/installed one of these units - or maybe even someone who has just put some thought into it.</font></blockquote> <div><br></div> <div>Haven't installed one yet, but have done some research on the subject.  We're making plans to install a complete workshop system after I return from Rochester, cashed up after receiving the final payment for piano no. 6.</div> <div><br></div> <blockquote type="cite" cite> <font face="Arial" size="-1">My air-conditioned concrete-block shop is attached to the rear of my concrete-block 2-car garage. I have been thinking of installing the cyclone in the garage, piping through the shop and exhausting outside the rear of the shop with no filters. This has the advantage of keeping a lot of the noise out of my shop and no hassles with filters. The downside of such an installation is that the garage is very close to my neighbor's nice back porch with pool (the noise might be a problem) and all the air that is exhausted outside the shop has to be made up with outside air coming back into the shop (half the year, humid and hot) - if this thing actually moves anything close to 1,500 CFM, it will replace all the air in my shop every six minutes or so.</font></blockquote> <div><br></div> <div>Yes, this approach will avoid the use of filters, but you'll be losing the workshop air that you've either heated or cooled, depending on the season. A 5 hp unit with appropriately sized ducting should pull around 2300 CFM. The manufacturer should be able to supply you with a flow chart for the unit, which plots CFM flow against restriction of the ducting in inches water gauge. When you design the system, don't forget to include the restriction of the flexible hose which connects the fixed duct to your machine. The flexible ducts are very lossy (these also vary considerably between makes - try to source one with a smooth inner bore).</div> <div><br></div> <div>I've uploaded the performance chart of a 5 hp unit that we're considering, to my personal webspace at;</div> <div><br></div> <div>http://members.optusnet.com.au/ronovers/25SDC.jpg</div> <div><br></div> <div>You can see on the chart the flow of this unit, with no restriction, is its fully rated 3200 CFM. At 10 inches water gauge the flow is cut to 2000 CFM and at 16 inches WG the flow falls to zero. The chart performance for each pump will depend on the design of the housing and in particular the impeller design. A straight bladed impeller will give you a higher unrestricted flow but will fall dramatically when subject to restriction. A backward curved impeller will give you less CFM at no restriction, but will deliver more CFM at a high restriction (which is the way it will operate most of the time). The best units use impellers with backward curved blades. Backward curved impellers also deliver a higher efficiency so they tend not to heat the air so much as it passes through the cyclone and back into the workspace.</div> <div><br></div> <div>You should be able to design your system so that the restriction of the system is low enough to enable the unit to  pull the required number of CFM to keep the system clear and the workplace clean.</div> <div><br></div> <div>The general rule of thumb is that you size the runners to your machines so that the air velocity is around 4000 ft/min, with the horizontal main duct sized so that the air velocity is around 3500 ft/min. In your case the calculations will be simple since you'll have only one machine operating at any time. The vertical runners, which usually run up from the machine to the main runner, require are higher velocity to lift the chips to the main runner, but once they arrive at the main runner 3500 ft/min is adequate to keep the duct clean. The use of a smaller main duct will cause unnecessary restriction which will lower the overall performance of the system. If the restriction is too severe it may restrict the air velocity to such a degree that wood chips become permanently lodged in the ductwork. If you get a copy of<i> Woodshop Dust Control</i>, this writer will take you through the entire process of designing a system which works. He also publishes the water gauge losses of pipe section sizes at the air velocities of 3500 and 4000 ft/min. You can calculate the losses at different velocities from the table yourself, since air restriction goes up according to the square of the increase in air velocity. In other words, if you increase the air velocity by a factor of 2, the restriction in the system will be four times greater. The design of a system is quite straightforward with the help of a good publication such as the one previously mentioned.</div> <div><br></div> <div>I've just about decided that I will make the ductwork from polyethylene (PE) pipe, since it is available in a great range of diameters. It is very important, when designing a system, that the runner diameters are appropriately sized. Runners which are too large will have insufficient air velocity to keep the wood chips in the air flow, while runners  which are too small will cause too much restriction for the cyclone to pull the required CFMs and keep the machines  clean. We'll be installing spiral earth wires around the runners to prevent static build up and the risk of an explosion. Another advantage of PE pipe is that large radius sweep bends are available, which will allow for the construction of relatively low-loss branch junctions.</div> <div><br></div> <blockquote type="cite" cite> <font face="Arial" size="-1">The alternatives are to install it inside the shop and exhaust through filters inside the shop (noisy, filter expense and hassle).</font></blockquote> <div><br></div> <div>The idea of mounting the unit in your garage is a good one, since it will keep the noise of the unit away from your work space. It will also keep the noise contained in your garage which will please your neighbours (unless there are no doors on the garage). If your garage has no doors you may eventually need to enclose the unit to keep noise down.</div> <div><br></div> <div>If you are running the outlet back through your shop then exhausting it outside, why don't you consider setting up some column style filters along one of your workshop inside walls? These filter types require a distribution plenum at the top (preferably just underneath ceiling level), to which is attached a number of tubes of filter material. The filter tube lengths are set so that they just reach low enough to be connected to collection buckets on the workshop floor. The filters are attached to the collection buckets with large hose clamps. The cyclone will remove most of the dust down to around 5 micron (1/5 th of one thou). The filter media will take care of the particles down to 1 micron. The advantage of this system is that you get to keep the air in the shop at a suitable temperature. There will be some heating which comes from the inefficiency of the impeller, which will have a slight workshop-warming effect in the winter and place a little more load on your air conditioner during the summer. But overall, the air con' will cope a lot easier than it would if you simply plumb the exhausted air from the cyclone out to the atmosphere. Your neighbour's pool will probably stay a bit cleaner as well.</div> <div><br></div> <div>Looking forward to meeting some of you listers at Rochester.</div> <div><br></div> <div>Isn't living fun some of the time.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>