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| Range hood blowers and dust collection http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=44394 |
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| Author: | Dave Baley [ Wed Oct 22, 2014 7:36 pm ] |
| Post subject: | Range hood blowers and dust collection |
I have the chance to pick up a high volume range hood blower. It is a Viking double squirrel cage blower at 1200 CFM. Anyone have experience or opinions on using such a blower as the basis of a dust collection system? |
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| Author: | Chris Ide [ Wed Oct 22, 2014 7:57 pm ] |
| Post subject: | Re: Range hood blowers and dust collection |
I made a box air filter using a squirrel cage blower salvaged from a furnace that I am happy with. I'm not sure that this type of fan would hold up to the constant barrage of particles in a dust collection system, maybe as a pull through with a cyclone before it that would separate out the large stuff. |
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| Author: | Bri [ Wed Oct 22, 2014 8:08 pm ] |
| Post subject: | Re: Range hood blowers and dust collection |
If it is anything like the sub zero blower I was installing today, I would say no. The squirrel cage fins are just light stamped metal and the box would be very dificult to seal. The blower impeller on both my dust collectors are big heavy blades, with a lot of area between the blades for debris to flow through. The kitchen units were never intended to push any thing but air or smoke. But... Possibly a blower for small a spray booth if you could work out the filters. |
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| Author: | Haans [ Thu Oct 23, 2014 6:44 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
We have one for our Viking stove. Not enough power for dust collection. My Oneida also has a huge impeller that spins at a very high speed. Dust and chips are stopped before they hit the impeller by a large filter. Very fine dust collects on the filter and the rest falls into the barrel... |
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| Author: | Clay S. [ Thu Oct 23, 2014 7:11 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
It might work O.K. for a dust particle collector to filter the shop air or as part of a down draft unit for catching sanding dust. "Dust collectors" are more chip and shavings collectors, and sometimes don't do that good a job of collecting airborne dust. |
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| Author: | SteveSmith [ Thu Oct 23, 2014 8:16 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
Clay S. wrote: It might work O.K. for a dust particle collector to filter the shop air or as part of a down draft unit for catching sanding dust. "Dust collectors" are more chip and shavings collectors, and sometimes don't do that good a job of collecting airborne dust. Cyclone type dust collectors with filters on the output are quite good at collecting the dust. I often leave mine running with through the downdraft table for exactly that reason. |
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| Author: | RusRob [ Thu Oct 23, 2014 11:26 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
I would tend to agree with the other comments. I don't think it will have enough CFM for collecting much dust as an air filter let alone enough for a dust collector. Two different items BTW... Dust COLLECTOR is for hooking up to a machine to pull the sawdust and debris away and a Dust FILTER is for the fine dust in the air. I just recently had to replace my furnace and before they hauled the old one out I had them remove the blower so I can make a dust filter. A furnace blower usually has at least 3 speeds and has a high CFM so it will exchange the air in my 600 sq foot shop quite easily. I have not built it yet but it should be pretty straight forward by just building a plywood box with a 2 stage filter before the air goes through the blower. I plan on using a standard furnace filter for the first stage and a standard 1 micron filter for the second stage. I will put a wire mesh over the opening where the air comes out to keep fingers and other small things from reaching the impellers. The fan you are have might be good for a small sanding table though... Do NOT use it as a spray booth fan because it probably has the motor in the air flow which could cause sparks and start a fire. Also the impellers in a squirrel cage fan will get clogged up with paint dust pretty quickly. If you want to make an dust filter I would go to a Heating and Cooling place and ask them if you can get the fan out of an old unit they removed. They will probably be happy to give it to you but make sure you get the electronics to hook it up and control the speeds. If you are looking for a dust collector you may be better off just buying one because you need a high CFM and a completely different kind of impeller along with a separator which is usually like a big funnel to separate the big stuff out before it gets to the fan. Just my 2c... Bob |
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| Author: | Pmaj7 [ Thu Oct 23, 2014 11:55 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
Dave Baley wrote: It is a Viking double squirrel cage blower at 1200 CFM I don't know why everyone is saying there is not enough CFM. 1200 is great! Although, I think a furnace type blower is going to create more pressure which i think is what you need for serious filtering. But, I hope someone with more experienc could weigh in on that. I have often wondered about that. Is there some spec like "water lift" for that? Also, I agree that the Impeller might be fragile. |
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| Author: | Clay S. [ Thu Oct 23, 2014 12:56 pm ] |
| Post subject: | Re: Range hood blowers and dust collection |
If you look at the specs for commercial dust filters/collectors they range from 600 cfm to 1700 cfm. I think 1200 cfm would make a workable unit for air filtration. Adding filters would probably reduce it some, but still seems like a worthwhile project. "Cyclone type dust collectors with filters on the output are quite good at collecting the dust. I often leave mine running with through the downdraft table for exactly that reason." Two stage cyclone collectors do a better job than the typical bag type dust collector. Once the filter bags become caked with dust they do a decent job of filtering small particles. When you empty the bags and beat the dust out of them they lose the ability to capture fine dust until a cake builds up on them again. |
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| Author: | Barry Daniels [ Thu Oct 23, 2014 3:58 pm ] |
| Post subject: | Re: Range hood blowers and dust collection |
Blowers are specified on both volume (cfm) and pressure (inches of water or whatever). Squirrel cage blowers are normally in the lower pressure range than impeller type blowers. Wrong tool for the job. |
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| Author: | Clay S. [ Fri Oct 24, 2014 5:36 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
As long as you are moving an adequate volume of air wouldn't a lower intake pressure be desirable? It would seem to me that it would be less likely to pull the dust through the filter. Isn't the idea of building a filter wall in front of an impeller type exhaust fan to essentially lower the pressure per square foot? Squirrel cage blowers tend to run quieter but not be as cheap as blade type fans. Cheap usually wins. |
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| Author: | Haans [ Fri Oct 24, 2014 6:51 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
The unit might work for a downdraft sanding table, I used to have a homemade one with a furnace squirrel cage and my Griz downdraft table has a squirrel cage. Dust collectors are a whole different game. You need lots of power to draw machine dust 15-20 ft. |
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| Author: | Dave Baley [ Fri Oct 24, 2014 9:38 am ] |
| Post subject: | Re: Range hood blowers and dust collection |
Haans wrote: The unit might work for a downdraft sanding table, I used to have a homemade one with a furnace squirrel cage and my Griz downdraft table has a squirrel cage. Dust collectors are a whole different game. You need lots of power to draw machine dust 15-20 ft. What type of filter does your downdraft table use? It seems like that would need to de at least as good a filter as a dust collection system. |
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| Author: | David Malicky [ Fri Oct 24, 2014 2:35 pm ] |
| Post subject: | Re: Range hood blowers and dust collection |
As mentioned, squirrel cage blowers are not for dust collection -- they just can't push (or pull) much pressure. Pressure is needed to overcome the resistance of the long ducts and especially the filters. And if they see 'dirty' air, wood chunks would damage the blades. In general the max pressure of these blowers is in the ballpark of "1 inch of water column" (iwc), whereas a dust collector blower can deliver up to ~15 iwc. Conditioned (dirty) filters have a ballpark resistance of about 5 iwc at reasonable flow rates; the ducts are somewhat less restrictive. A blower's cfm rating is generally given at zero pressure resistance (open inlet and outlet, no filters, nothing to impede flow). So two "1200 cfm" blowers can be vastly different in performance. Hypothetically, in the pic below: - The dark blue line is a dust collector blower: 1200 cfm into free air (0 iwc), and 15 iwc when plugged. - The light blue line is a squirrel cage: also 1200 cfm into free air, but only 1.5 iwc when plugged. - The red line is the "system curve": it accounts for the resistance of the ducts and filters, and tells us how much pressure we need to achieve a given flow. - The green dots are the "operating points" for that system and each blower. The DC blower in this system will actually flow about 900 cfm. The SC blower will only flow about 350 cfm. - To flow more than 900 cfm, we either need a different system curve (more filter area, bigger diameter ducts, long radius elbows...) or a bigger and/or higher RPM and HP blower. Attachment: ScreenShot082.jpg If picking up a blower second-hand (and you can't get any data on it), you can get a rough idea of its pressure capability by the radial length of the blades and the HP of its motor. Short blades (squirrel cage) and/or a 1/2 HP motor can't push much pressure. These were designed for systems with big ducts and unrestrictive filters. |
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