Filter dust without losing heat?

[Don P]

If you were to put a sealed plywood box on skids under the cyclone and run a flexible boot from the cyclone to the sealed box, do you need an airlock?

[scsmith42]

Brad, when I built my shop ten years ago I was unaware of the rotary air locks.  Hands down, if I ever have to rebuild my system I'll use one.

What I did was include a room specifically for dust collection.  It has a tandem axle dump truck parked inside with a 10' tall sleeve of filter cloth that attaches to the top of the dump truck bed.  The top end of the filter cloth terminates into a solid ceiling with penetrations for the dust collectors shavings and dust to enter.

In-between the dust collection room and the main shop is a wall that is covered with additional filter cloth.  What my system does is allow me to keep all conditioned air inside the shop, but capture all of the shavings and dust in the attached room with two levels of filtration in place.

It works as designed, but a rotary air lock would be superior.  If I had it to do over again, I would allocated the floor space in the dust collection room as additional shop space, duct my dust collection outside under a shed overhang using a cyclone with an air lock at the bottom (suspended above a dump truck bed), and then vent the discharge from the cyclone back into my shop via a couple of HEPA filters.

This design would allow for my conditioned air to be returned to the shop, yet the bulk of the dust and fines to be managed outside.

I can understand a benefit of controlling the acceptance particles using an airlock below the cyclone separator (inside) the building.   I would appreciate if you could explain how the added cost of an airlock would be worthwhile or necessary when discharging the cyclone dust into the truck outside.

Because without the airlock you lose your conditioned air.
I'm pretty fanatical about keeping my kiln dried wood in a humidity controlled enviroment.  I view it as a competitive differientator (our lumber is 6% - 8% compared with our competitors 10%+).

Plus, it's nice to work in a climate controlled shop.

Based upon the volume of shavings that we produce, a standard cyclone with bags or barrell's is not practical. There are days that we have filled a tandem axle dump truck in a single day.  That's a lot of lost time to empty bags....

No matter how good your system is, you will still get a bit of a mess around the dust collector.  Putting it outside takes the mess outside. 

But using a rotary air lock allows you to dump into an open dump truck outside (high capacity) yet vent your exhaust back inside - thus keeping your climate controlled air inside.

I have two dust collectors that both dump into the dump truck.  A 3 hp single phase system that collects from all of the smaller equipment, and a 5' diameter blower attached to a 15hp 3 phase motor that evacuates all of the major production equipment.  The 15hp system is gated to allow it to evacuate the smaller system as well.

The 5' blower will evacuate all of the air in the shop within a few minutes.  So if I direct vent outside during the summer time, I'm sucking a lot of 90% RH air into the shop.  That also means that I have to work the HVAC 2X to 3x harder to catch up.

Not something that I want to do.  I recognize that this is not the best approach for everybody, but it works for me.

[Brad_bb]

FYI here is the system that Satamax suggested.  Note that it is a 3phase blower.  I don't have 3 phase, so I'll have to figure this one out.  I need to understand if there is an advantage to using a 3phase rotary converter and using 3 phase equipment like this.  Sure it drops the current draw in the machine, but does it reduce spikes when it's turned on and off or any other advantage to going 3phase?



 

[Brad_bb]

SCSmith42,
Yes, I could blow outside into a bin during summer.  Considering that.  I just want to be covered during winter.  The mill shop is not Air Conditioned during the summer, but is so well insulated that it maintains the existing temp almost all day.  It's only when you get into the really hot humid dog days that it's no longer as comfortable in there.  Opening and closing the 20ft overhead door to bring logs in and out will negate that though the 2 days of the week I mill and you'll end up as warm as outside.  Who knows, I may add A/C in that room later if I think I need it.  The rest of the building is Air Conditioned, like the woodworking room next to the mill room.

You brought up another issue, sizing of dust collection versus what is will collect dust from.  Surely my regular shop tools like table saw, band saw, jointer, smaller planer, mitre saw, won't require nearly as large of a blower as the sawmill, sawmill beamplaner, and commercial grade board planer.  So the next question will be should I have one blower to do everything, or a larger and a smaller one?

I currently have a 1.5 HP Jet blower pulling beam planer chips about (20 feet of 4" hose), and blowing them in an open bin the the adjacent room (polebarn that has two halves, one side is concrete insulated and heated, the other is gravel unheated).  This is the current shop, not the new shop.  In the new shop my pipe run will probably be 55 ft plus 20 feet of hose.  I need the hose because it needs to move with the beam planer- it runs down the sawmill track. So maybe stepping up to 3hp or 5hp might do it?  I'll have to consult someone like Oneida to help me with that sizing.  If I end up with the 5hp unit, will the speed of that motor be controlled for tools requiring less suction.    the runs for some of those tools will probably be 35ft plus a short length of hose to connect or a rigid connection.

[Andries]

If you were to put a sealed plywood box on skids under the cyclone and run a flexible boot from the cyclone to the sealed box, do you need an airlock?

Don: No, you wouldn't need an airlock.
Brad: Look at the image below - no airlock, no 3 phase power. Substitute a sealed plywood box in place of that dinky little 55 gal drum, as Don P suggests. If you have a huge amount of dust and chips - make it a BIG box. 
A small system for the small equipment, (maybe your existing ?) and a big (5 hp.) for the big producers, like planer, jointer and sawmill. 

[ScottCC]

What I meant by using make-up air was if I can push outside air at close to same rate as the vacuum is sucking at the point of suction then for a low cost I could greatly reduce my heat loss.  I think the reality is if I could afford a really nice three phase system I would not be trying to get around the issue.  Doing more with less is my approach, my mom bought me my first hammer so I blame her.  In-floor radiant heat also reduces the need to concern yourself with air changeover.

[YellowHammer]

I run a 5 hp single phase with a 3hp booster for the edger.  Three phase motors are cheaper for the same hp but since I have limited three phase using converters I don't want any more on them than neccssary.  Single phase is fine but top out at about 7.5 hp, 220V. Anything over that will need three phase.  

The main thing about a good dust collector system is that it should be hands off, zero effort and just runs in the background.  Ours usually runs the entire work day, and more than once we've closed up and walked away only to hear the blower still running.  Oops.  

Some tools really benefit from high airflow extraction.  My planer kept eating belts, little pieces of chips would get between the power belts and pulleys and eventually rip them up.  When I upgraded our system, we've not torn up a belt since.  

[Brad_bb]

Yep, I'm betting you can do the 5hp in single phase, though I only see 3ph advertised on their site.  By Booster you mean you're running two blowers at once?  Does the edger need that much airflow, or is the run longer to the edger and thus need help?

[Satamax]

Brad, changing a motor shouldn't b. e that complicated. And i'm prety sure they can do it for you. 

For the guys advocating venting outside etc. Careful guys. In Europe we see the start of restrictions in dust levels that we're allowed to release in the air. It might come soon where you are. 

[YellowHammer]

Our edger is a long way away, the booster is hooked directly to the edger, and gets everything going down the pipe, when the other one blower takes over.

Boosters are a good use for spare dust collectors, we only use the motor and blower which generally are pretty compact.  I take all the other stuff off, just hook to the machine with a short flex pipe, suck it in, shoot it out down the main pipe.

[Don_Papenburg]

With the grain bins you should be able to get 3ph  .  That is if the line goes past you . I know they grumbled about me getting it , I told them that had planned on putting up a couple of bins .  I never got to that but use a lot of smaller equipment on 3ph .  my largest will be a 210 cfm compressor soon.