How much do "leaks" affect efficiency of a dust collection system

[Ken Vick]

Some people seal all their pipe joinery and are careful to eliminate all small leaks from their system. Others, myself included, don't take any special pains, just make good snug connections but no duct tape sealing, etc. Does anyone have any data suggesting that sealing all the joints significantly improves their system?

I wonder if people aren't confusing the requirements of a dust collection system with a vacuum system in which you are attempting to pull all the air out of an enclosed system. Clearly with the vacuum example, even tiny leak will be significant.

With a dust collection system you are pulling air through an open pipe, in my case 6" machine to cyclone. The amount of air that is moved is related to the cross sectional area of the pipe. If the system has a "y" and both pipes are open the amount of air pulled from each of the 2 open pipes is proportional to their cross sectional areas. If one of these is a 4" pipe and the other is a 6" pipe, the 6" pipe will pull something over twice as much air as the 4" pipe. Now consider a leak in the system. The leak is equivalent to another "y" with an open pipe end. But just in the case of the 4" and 6" pipe above, the amount of air drawn from the leak is proportional to its cross sectional area of the pipes in the system. Unless the leak was huge, like when I inadvertently leave several of my blast gates open, I don't think that leaks have any measurable impact on the efficiency of the system and that taking great pains to seal everything is not worth the effort. Yes, No?

[EricU]

my guess is that a little bit of leakage doesn't hurt anything. Really hard to tell without testing though. Life is too short

[David G]

I agree. The impact of leaks is roughly proportional to the open area of the leaks compared to the open area of the ductwork. I would seal up the joints at or near the dust collector, especially any loose metal cyclone to PVC pipe joints. And with a 1-1.5 Hp DC, every little bit helps.

[Alan S]

In the ducting, I suspect you're right. But in the DC itself with a pull-through cyclone, a leak can destroy your separation.

[Ken Vick]

Alan S said:

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In the ducting, I suspect you're right. But in the DC itself with a pull-through cyclone, a leak can destroy your separation.

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On the inlet side for sure. Any sizable leak between the cyclone and the dust container can pull all the collected dust across into your filters just like overfilling the container, BTDT. On the outlet side a sizeable leak there might improve your air flow depending on how stopped up your filters are but you are going to be breathing a lot of dust--had that happen too. Ken

[MichaelMouse]

Light a cigar, walk the line. Where smoke's pulled in, tape up.

[Ken Vick]

MichaelMouse said:

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Light a cigar, walk the line. Where smoke's pulled in, tape up.

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I guess the implication of your comment is that leaks you can find with smoke are significant enough to worry with. It is possible to find small leaks but my suspicion is that the volume of air entering the system from these small leaks is so small, compared to the amount entering the system at the open end of the pipe as to be inconsequential. I would be interesting to see data. Years back I used metal foil duct tape to seal every joint but for the last several years I have just stuck the fittings together, using a couple sheet metal screws when necessary to keep the joint together. I have not noticed any difference in the efficiency of my system. I would be interested hearing from people who had the same or different results.

[fall]

One factor would be the size of your system if it is large and you have a lot of runs the more leaks would have to cause a lack of efficacy. In a smaller system it may not make that much difference as you are closer to the collector.

[Pink Floyd]

Ken Vick said:

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I don't think that leaks have any measurable impact on the efficiency of the system and that taking great pains to seal everything is not worth the effort. Yes, No?

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Small leaks do affect the efficiency. Enough to worry about, probably not if the system is a good one.

I have a 3 hp cyclone and 6" PVC ducting. I didn't glue or seal the duct connections but I did put a 3/8" long screw into each connection to hold them together. It's been in place several years and there is dust around every one of those screws which tells me some air is being pulled in around them. I just note it as interesting and don't try to do anything about it since it's a tiny amount of the 1500 cfm the collector pulls.

I even took the gate out of the connection to the TS so that it stays open all the time. The other machine gates get opened and closed selectively.

[DFJarvie]

Unless you have a lot of little leaks along the line it won't make much of a difference. Making sure there are no leaks in the DC is more important.