# Clogs in the DC hose



## gfadvm (Jan 13, 2011)

I have just started getting clogs in my 4" hose just before it enters the dust collectorGrizzly cannister filter type.Problem only occurs when planing cedar or pine[large fluffy shavings],no problems with oak,walnut,osage orange,etc.I have 10 feet of 4" hose,then 7 feet of 21/2" to the planer. No clogs in the 2 1/2 which I dont understand.Any suggestions would be appreciated.


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## cabmaker (Sep 16, 2010)

If youll remove the y from the impeller unit you will see a protective grid made of plastic. Large fluffy chips will build quickly there. I use to use these type collectors and they all did that . I eventually removed the grid and eliminated the problem. Some will advise that the grid is there to protect the impeller from large chunks and that is correct, but I never experianced a problem by doing so. And I have ran many types of material and many hundreds if not thousends of bd. ft. doing this.


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## NBeener (Sep 16, 2009)

If it were me, I would add a chip separator or Thien baffle.


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## Gregn (Mar 26, 2010)

I have to second Neil's suggestion. By removing the grid you could end up with a bigger clog.


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## 8iowa (Feb 7, 2008)

The fact that you don't have any clogs in the 2 1/2" hoses is an important clue. You likely have a velocity problem in the 4" hoses. Air velocity in the hoses needs to be at least 3500 fpm in order to suspend the dust & chips in the turbulent airstream. When the chips enter the 4" hoses the velocity falls by a factor of 2.57, inversly proportional to the difference in the cross sectional area of the hoses. Whenever dust and chips accumulate in the hoses, low velocity is usually the problem. If you run 2 1/2" hoses all the way to the dust collector the problem will likely be solved.

I know that this is a difficult concept to grasp as the common belief is that "the bigger the pipe the better the flow". However, the velocity must be kept at or above 3500 fpm for successful dust collection.


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## TheWoodsman (Jun 21, 2010)

8iowa is on it. 3500 to 4500 feet per minute is the typical air-speed range that DC design follows for woodworking. I would make sure the filters are clean before resizing pipes/hoses. Keep in mind that sanding dust packs filters pretty quickly and they need to be beat or shaken regularly.


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## brtech (May 26, 2010)

While I suspect you are right that the problem is the step down to 2 1/2, a better solution would be 4" all the way, rather than 2 1/2" all the way. He has the Griz with the canister, which has enough oomph for the 4".

Of course. 17' of flex is pretty bad.

Consider replumbing with 4" PVC, or PVC to within a couple of feet and then 4" flex to the planer.
If you do that: no 90s, only 45s and a short section of straight duct.

And the Thein separator is a really good idea.


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## verdesardog (Apr 2, 2011)

I have a 30 gallon oil drum I use as a seperator before my DC, I have put two 4" elbows in the lid to make a semi cyclone in the can and an 8" square dischagre to 4" flex hose It keeps all the big chuncks out of the impeller, it even does a decent job of collecting dust!


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## gfadvm (Jan 13, 2011)

I replaced the first 10 feet of 4" flex with 4" pvc and this appears to have solved the problem.Thanks for the suggestions.


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## bubinga (Feb 5, 2011)

I don't why you would not, have 4" all the way to planer


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## alkillian (Mar 19, 2011)

cut the cross grid out and you wont have any problems. We have a 2 hp grzzly and we had to cut the grid out to keep it from plugging.


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