I’ve got a single-bag Delta dust collector, and it sucks up sawdust from my TS, router table and jointer like a champ. But when I turn it off, the bag collapses. This creates backpressure along the line, and if there’s very fine dust still suspended inside the DC, it comes floats in the air stream and right into the machine I’m using.
I’ve come up with a few strategies, but I’m hoping someone has a better idea than these:
1) Spend a lot of $$ and put auto-blast gates on each of the machines. Thus when I power the tool off, the automatic blast gate will prevent the blowback when I (later) shut off the DC.
2) Spend less $$ and put an auto-blast gate on the DC itself, on the main hose that goes into it. Theory is, when the DC’s on, the blast gate will open; when it’s off, the gate will auto-close before much air gets forced back.
3) Spend even less $$ and make or buy some sort of one-way valve, and install it permanently in the 6″ hose that leads into the DC. This might be something like a “flapper” valve you see for furnace vents, etc.
4) Spend nothing, just close the blast gates manually before shutting off the DC. This is the least favored solution.
Any suggestions would be greatly appreciated!
Replies
Is there a way to hold the bag up so that it doesn't collapse? Strings/cord or bungee to the ceiling maybe.
Well, the DC has a hook that holds it up, so it's not falling to the floor of the DC, it's just losing its volume as the blower shuts off. I suppose yet another possibility is putting "hoops" inside the bag to keep the thing expanded much like it is while in use.
I have upgraded my 4 bag (2 up and 2 down) to 1 micron bags and they are stiff enough to stay "inflated" after the collector is off. Your hoop idea is a good one and worth a shot. Some of the super magnets that everyone sells would hold a coat hanger wire or strip of sheet metal in place without putting any holes though the bags.
FatherJohn,
I have the Delta AP400 single bag system (w/ a collection bag on the bottom to hold dust/chips/ect). My top bag has a steel bar that holds the bag up when not in use. I have run into the same problem when I store my machine (removing the arm and letting the bag sink into the machine, dust is pushed out). Does your single bag system have a bar to hold it up? If not, I would rig something up so the bag would not "deflate" and create back pressure, thereby, pushing the fine dust out.
I hope this helps with your problem.
Joe
Is it really saw dust or wood dust?
I think I would check the impeller to see if something has wrapped around the shaft. My bags stay inflated long after the switch is off. The impeller coasting to a stop keeps them up and lets them down very gently. I have my upper bags tied to the ceiling, not because of blow back on deflation, but because the force of the air on start up would blow them off the top. Talk about a mess!
Beat it to fit / Paint it to match
Hmm, still thinking it over. Right now I guess I'm leaning toward the automatic blast gate on the DC infeed. Then when the bag collapses the air will have to go out through the DC's top bag.
I'm not that concerned about the dust released into the air, which the air cleaner should take care of pretty quickly.
I know this sounds like a pretty trivial thing, this dust. But when I'm working with the TS, it creates little bits of wispy dust underneath and around the TS cabinet (the Unisaw is not what you'd call 'hermetically sealed') in pretty short order. It's enough to make the floor pretty slippery, so it's a minor safety issue.
Edited 11/28/2005 5:13 pm ET by FatherJohn
Depending on what you read about breathing fine dust, your bag collector could be a major safety issue. You can kill two birds with one stone by buying a filter cartridge to replace the bag filter. The cartridge will do a far better job of getting fine dust out of the air then your bag and won't blow back when you depower. Andy
Hey John,Dust collection is NOT trivial. The most dangerous stuff is the dust that you can't even see.I agree that, if you can, you should upgrade your system to a cartridge filter (Grizzley sells upgrade kits), or at least to a high efficiency mylar filter bag.Lung, and other respiritory problems are not the only hazard associated with wood dust, there are also wood allergies to consider. They can stop you in a heartbeat, litterally, and they usually develop with discouraging speed. Your best defense, is dust collection.Do yourself a favor and ask someone who cares about you, to get you an upgrade kit for Christmas.Tom
Maybe I'll look into a cartridge, thanks. I just installed an air cleaner last night, the three-speed Delta. If I do much more of this, my safety gear will out-bulk my working gear. :)
I have a cyclone separator between my machines and my single bag collector. This seems to trap an "blow back" Not sure why, I am assuming gravity. the other thing is I have an air cleaner that blows the clean air toward me. Lastly there is a fan that blows at the back of my head (when at the table saw/router table) and gives the dust a chance to settle or get trapped by the air cleaner.
Lastly I wear a dust mask. Admittedly not all the time, I find them uncomfortable, but especially when using the table saw. I keep telling myself that coughing is more uncomfortable than the mask. I even made a sign that faces me that says just that.
Muleboy.
I'll wear a mask when machining exotics or MDF, but other than that, not so much. It's interesting that the technology that lets us burn through wood so quickly requires so much care to keep us safe!
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