Installing Dust Bags in a Cyclone

It's more complicated than you would think to get a liner bag working properly inside a dust-collection cyclone. June 15, 2014

Question (WOODWEB Member) :
I have an older 2 HP Cyclone that has a 30 gallon fiber drum that fills very quickly. I added a 55 gallon drum and put a plastic liner/bag in it with the hope that I could tie it off and pull the bag out, only to find out that it was sucked into the Cyclone. Has anyone figured out how to keep the bag in place? I've seen that "Oneida" has a clip system to hold the bag in place. Does it work or what set-up do you use?

Forum Responses
(Dust Collection and Safety Equipment Forum)
From contributor J:
Does the lid seal tightly over bag, which I'm assuming hangs over the lip of the drum? Are there any holes in the drum?

From contributor O:
If the liner is pushed down in the barrel when you install the bag then it can't suck that bag up if the barrel is sealed air tight. Air has to be getting to the outside of the plastic bag and then the bottom of the cyclone. Being under a negative pressure will suck the bag up. Find out how the air is getting in. I would make the same change if I had the height. I have one of the Onedia's with the small barrel also and as soon as the thing fills up, which happens fast, the internal filter plugs and the cyclone packs solid and sometimes backs up in the duct - a major pain. What they really need for that system is a low cost rotary valve.

From contributor J:
"What they really need for that system is a low cost rotary valve." Or a level sensor connected to a light or buzzer in the shop.

From the original questioner:
You both may be on to something. Earlier I had used a translucent 55 gallon plastic drum with drum liners and I put 1" holes in the drum to help removing the bag and break the suction. I will try a new drum with no holes. On the fiber drum I cut a 18"x18" square hole in the side and used a piece of Plexiglas sealed to the fiber drum. It works well in letting you see the contents, but is way too small when surfacing a stack of lumber.

From contributor L:
Take the plastic or fiber drum and cut the bottom out, leave the ring intact and slip the bag over the outside of the drum. When the bag is full pull the drum out of the bag. I have been doing this for years and it works well.

From contributor O:
I really missed the other important step (you still need an air tight can.) I have been using bag liners for so long as an easy way to carry the dust out - that one step slipped my mind. Put the bag in with as little of the bag up under the rim seal and outside the can as possible.(Use a big enough bag so that you have some left over inside the can). The last thing I do is stick my finger through the bag to make a hole just below the rim (inside). That allows the air between the bag and the can to escape. The suction then cannot act on the bag because the pressure is now equal between the inside and the outside. I have been doing the bag changes so long that I forgot that that step was needed. When the bag is full you tug on the liner and the hole (about the size of your thumb) ends up in the part above the twist tie so the bag does not leak.

I was not getting bags sucked up, but I was getting incomplete bag filling because of the trapped air bubble inside the can and outside the bag. You also need to open the bag up (a quick tug on the two sides of the top and fanning it through the air to open the bag up.)

If there was a low cost rotary valve I could just stick a light weight garden leaf cart (or whatever they are called, not a contractors wheel barrel but one of those low slung two wheel carriers for the lawn and garden) in place of the barrel and could wheel it out and dump it easily as well as being able to see the level. If it overfilled it would not plug up the whole works.

From contributor W:
The best way to handle this is to install a small hose from the housing of the unit to the side (bottom) of the drum. This equalizes the pressure when running, preventing the bag from getting sucked up, and also allows for easier bag removal when the unit is turned off leaving a path for air to enter below the bag.