Confused by DC

[Mark Blatter]

I was finally able to fire up my DC from Clear Vue yesterday. It has taken forever, but once I did, I found something that I did not expect. I have the cyclone dumping into a Brute plastic receptacle. My anticipation was that it would end up somewhat pressurized but instead after running for about 45 minutes, the sides were some what caved in, meaning that the can had a suction applied. Is that normal or did I mess up the install some how?

I was running a wide belt sander so everything I collected was saw dust, no shavings from a planer or jointer. I was also a little surprised by how much dust there was in the bottom of the filter case.

[Chris Parks]

There should be no excess pressure or suction in the drum, it relies on this condition to work. There is a leak somewhere at the bottom of the cone or in the drum, it should be absolutely air tight in this area. The way it works is the air/debris enter the cyclone and the circular action separates the two and the air then exits the impeller housing. The dust you see is the caused by the cyclone being able to suck air from the drum thus holding a small amount of debris in the air stream.

[Doug Garson]

Considering the cyclone is on the suction side of the dust collector fan, how can the bin not be under negative pressure?

[Jim Andrew]

My drum is under pressure. If I forget to put the clamps on the lid to the barrel, the lid will lift off the barrel and all the dust gets sprayed around.

[Chris Parks]

My drum is under pressure. If I forget to put the clamps on the lid to the barrel, the lid will lift off the barrel and all the dust gets sprayed around.

In theory the exhaust should be big enough to cause no restriction so as not to pressurise the bin. The air should enter the cyclone, separation occurs above the bin and the clean air leaves all within the cyclone and not the bin. TTTT I have never questioned this and never attempted to measure the pressure in the bin, anyone know more?

[Chris Parks]

Considering the cyclone is on the suction side of the dust collector fan, how can the bin not be under negative pressure?

Ideally if the ducting presents no restriction it won't be as there is no need to try and draw air from the bin. The fan will draw air from the easiest source and if there is a leak in the bin it will draw from there instead of the ducting which in itself is restricting the air flow and the cyclone which is also very restrictive because the air has to change direction inside it. Bill Pentz gives all the losses in ducting and the cyclone on his web site. Again, in theory you can't draw air form a closed container. I am sure others can explain all this stuff better than me, I just know what works.

[Peter Christensen]

Any possiblity the flexing of the plastic trash can is breaking the lid seal allowing air to enter and carry the dust to the filters?

[Tony Latham]

Same issue here:



I always assumed that the entire system would have a low pressure.

T

[sean meltvedt]

Mark, the collection bin is on the suction side of the impeller, and will see the maximum vacuum the system can create. On my clearvue, I used a plastic drum that has a much thicker wall than my garbage cans. Also, in my experience-sanding dust will slowly accumulate in the filters. I clean them when it reaches 3.5 to 4” water column differential across the filters. When I do clean them, I get several quarts worth of fine dust - so fine it flows like water. Cleaning intervals is directly related to how much the double drum sander is utilized. To minimize any carryovers of dust, be sure your collection bin and connections are airtight.
Cheers
Sean

[Mike Kreinhop]

My 35-gallon plastic drum also tends to collapse from the suction of the DC fan and break the seal at the top. When this happens, my filters fill with dust. I suspect the reason is as Chris explains and my duct work is too restrictive.

To minimize the problem, I added some internal braces to the drum so it keeps its shape. This works well, but I plan on replacing my 120mm ducting with 150mm ducting.

[Rod Sheridan]

The suction on the dust outlet side of cyclone is why my Dust Deputy cyclone kit has 2 plastic pails, one nesting inside the other. The extra wall helps withstand the outside air pressure...........Rod.

[Roy Petersen]

In theory the exhaust should be big enough to cause no restriction so as not to pressurise the bin.

That doesn't sound right, Chris. If the bin were not under pressure, leaks would not be an issue that would cause dust escaping the bin.

As I understand it, the entire system upstream of the impeller is under (negative) pressure, so that dust is pulled towards the separator from the machine being serviced. The cyclone and bin are more or less equalized to each other, when sealed correctly, which allows dust to settle rather than swirl up and out. The difference is that there is no stream of air (hopefully) from inside the bin to loft the dust into the airstream occurring above near the top of the separator.

[Doug Garson]

That doesn't sound right, Chris. If the bin were not under pressure, leaks would not be an issue that would cause dust escaping the bin.

As I understand it, the entire system upstream of the impeller is under negative pressure, so that dust is pulled towards the separator from the machine being serviced. The cyclone and bin are more or less equalized to each other, when sealed correctly, which allows dust to settle rather than swirl up and out. The difference is that there is no stream of air (hopefully) from inside the bin to loft the dust into the airstream occurring above near the top of the separator.

Agree with your post with the addition of one word negative.

[Mark Blatter]

I know I don't have any obstructions in my pipes, plus since right now only the wide belt is hooked up, I have gates on the openings where the other pipes will go eventually. I had both of the gates partially open to minimize the pressure on the system.

It is highly likely that the seal on the collection bin (plastic can) is not solid as it starts to collapse. That explains the dust in the filters. Knowing that there is a significant suction on the can, I am thinking I will get a metal can so that isn't a problem in the future.

[Roy Petersen]

Agree with your post with the addition of one word negative.

That was the intent, yes. Didn't meant it to say it was outward pressure.