Dust Collector Issue

[kelLOGg]

I have a 60s version 5 HP Powermatic planer to which I added a 1.5 HP dust collector on top of two 55 gal drums tack welded end-to-end to make a tall chip storage unit. As long as the storage unit is not full the dust collector really sucks the chips which collect in the drums with the fine particles exiting with the exhaust. (I'm far away from my neighbors so inhaling fine particulate is not a problem.) When the drums are full I would expect ALL of the chips to start exiting with the exhaust because there is no room for them to settle and the turbulent flow would carry them out in the exhaust. But this is not what happens - they exit the infeed side of the planer even though the dust collector is still sucking air as strong as ever. When I empty the chips via a cleanout door normal operation is restored. This has been going on for about 10 years. What gives? See pics.
Bob

 

[gmakra]

The phenom is call fan stall. When the exit is blocked the fan still runs but blows out the exhaust.
You know what to do just keep your drums from getting to full, plus your back should agree with me.

 

[kelLOGg]

The exit is not blocked. Air comes out of the exit full force but chips don't. That's the conundrum.

 

[ehpoole]

Most likely explanation is that the volume of airflow has dropped off significantly from when things are working nominally and the bins are not full, such that there is no longer sufficient velocity on the suction side to capture the chips being thrown off by the knives. As a result, the inertia of the waste chips allows them to escape the intake airflow and make it through to the planer’s infeed side.

 

[kelLOGg]

That is certainly logical reasoning which could be confirmed by air velocity measurement which I cannot do. The exit air stream surely feels very strong. I raised the blower off of the drums and took a pic of the chips - it shows the effect of a turbulent air flow pattern which could affect the air velocity giving credence to your explanation. If I didn't have enough to do I could rig up a vane to respond to the force of air with and without full bins but I think I will just empty the bins and get on with wood work. Thanks for the response.
Bob

 

[JimD]

You can get approximate airflow pretty cheaply and easily with a wind speed meter. I think I paid less than $20 for mine from Amazon. It is approximate because you will raise the speed of the airflow by putting the meter in it (it blocks area). But it would be a good way to understand the change (since the measurement could be done both ways with the blocking having the same effect).

 

[kelLOGg]

I emptied the chip collection barrels, ran the planer and chips still poured out of the infeed. This sucks, I said. I removed the shroud from the planer and saw chips really packed in it and in the flexible tube to the collection barrels. I removed the other end of the tube from the dust collector and saw the problem. Years ago I ran a grounded bare copper wire internally in the tube to prevent possible static discharge from the flowing dust/chips. Chips had slowly accumulated between the wire and the tube wall starting a blockage that very slowly increased moving its way down to the planer and reducing the flow rate so slowly that I didn't notice it. I removed the wire. Planer really sucks now! in a good way.

 

[Dreuxgrad]

Watch your cholesterol!