Half full of Half Empty?

[Dale Thompson]

No! This is NOT a test for Laguna Mark. :) I've got a simple Penn State DC which, incidentally, I like very much. My question is: The bottom bag has a "window" which is about half way up the bag. It seems as though whenever the dust level reaches about half way up that window, the collector seems to lose a bit of suction. Is this the level at which I should empty the bag? It kind of makes sense because, due to the input/output design, the energy of the collector is starting to get depleted because it has to "stir" up everything underneath any new incoming material. :confused:

Dale T.

[Kelly C. Hanna]

I have noticed the same thing on my little Grizzly DC...I would say yes, since I did this last time and it seemed the suction was greatly increased afterwards.

[Chris Padilla]

Half full or half empty? I say, "It's twice as big as it needs to be...." ;)

[Robert Ducharme]

I read someplace that the lower bag should basically be kept empty for those type of DC to work most efficiently.

[Dan Mages]

It is neither half empy or half full. It was a failure by marketing to determine the correct size required for their customers. It needs to be sent back to R&D to be reengineered.

Dan

[Tom Hintz]

Dale T,
I have been told by more than one manufacturer that the bottom bag is as essential as the top in passing air out of the DC to maintain it's performance. As the bottom bag fills, less air is exhuasted from the DC, which reduces how much it can inhale. Since DC's work more on volume of air rather than velocity, like a shop vac, this becomes a more important factor.

On another note, though I now live in Concord, NC, I am originally from the South (Sout') side of Milwaukee and used to spend summers in Marrinette on my great aunt's (Schrank) farm.

[Steven Wilson]

The bottom bag has a "window" which is about half way up the bag. It seems as though whenever the dust level reaches about half way up that window, the collector seems to lose a bit of suction. Is this the level at which I should empty the bag?

In short, yes. The CFM of the single stage, double bag collectors goes down as the bag fills up. You can improve things by getting a very large, felt, upper filter bag.

[Mark Singer]

As we have found , after years of careful study ,many DC's suck....which is a good thing....if they didn't they would be TC's (trash cans) If its half full or its most likely half empty or maybe your half full of...
Dale just kidding! (laguna Mark!)

[Tim Sproul]

get a cannister top.....doesn't matter so much how full the bottom bag is.

Regardless, I'd highly recommend emptying the bag at 1/2 full.....at least at 3/4 full....do NOT wait 'til it is completely full damhikt

[Arvin Brown]

This is an easy one - the amount of air that goes into the system has to equal the amount going out of the system - basic law of engineering. Therefore, as the dust bag gets fuller and fuller, the air velocity escaping has to increase - but for this to happen the pressure has to increase. Well at some point the back pressure of the dirty bag is going to equal the pressure that the system can make and wala - system stops working. The best performance of a DC is the second that it is clean - it begins to become less and less efficient the longer you let it run without cleaning.

[Arvin Brown]

Forgot to add - that is why in my business - paper (which is quite dusty) our dust collection systems (usually around 100-200 hp each) have automatic shake down every so often with a screw conveyor at the bottom to take the dust away. Therefore, always keeping the bags clean and keeping a high performing system.

[Dale Thompson]

Thanks Guys,
I think that I will stick with the "half-full" level for emptying the bag. Life is always a compromise as several of you stated in terms of keeping the bottom bag as empty as possible.

Arvin, back when I used to fake my credentials as "a injunear", I installed quite a few bag collectors. Ours were always cleaned by high velocity air shots. The waste was then dropped into the exiting Star valve. I would think that mechanical "shakers" would require more maintenance in a dusty environment. DUH - but what do I know?? :confused:

Tom, you obviously know where Peshtigo is. Therefore, I will be sure to be nice to you. :) I'll bet that we got more snow than you did this year! Great for snowmobiling - finally!! Do you recall exactly where your Great Aunt's farm was?

Steve, I'm maxed out on height in my shop. I'd like to increase the ceiling height but that would mean taking out our kitchen. :eek:

Laguna, I'm not saying anything to make you angry. I'm afraid that you will send your Gulfstream airforce out here and bomb my humble abode with water balloons. Water has a nasty tendency to deleteriously impact the strength of cardboard. :(

By the way, all you rich guys out there with your fancy "cyclones" should realize that you have nothing more than a sophisticated "bag collector". A true "cyclone" collector is nothing more than a centrifugal (or is it centripetal) separator. The "cyclone" action throws the larger particles to the outside of the container where they caught and discarded. Unfortunately, the "fine" stuff escapes entrapment and is exhausted into the environment. Your fancy "cyclones" have a filter (i.e like a bag) which collects these "fines" and allows them to be caught. :D :eek: DUH - what do I know? ;)

Dale T.