External venting

I have been reading the Bill Pentz site and am considering building a cyclone unit.

I currently have a 3 phase 3 hp twin bag system sitting against the back wall of the shed. It is ducted to most machines and works reasonably well. Of course the shed has a nice fine mist of saw dust in the air that I assume escapes through the bag filter. This is not to mention the constant mess around the base with the plastic bags I try to use.

Unfortunately, I do not have a suitable location outside to have the unit, and it takes up a large amount of space in the shed.

My question is regarding the external venting versus pleated filters on a cyclone unit. It makes sense to me to vent the unit outside. My concern is the amount of dust that would escape through the vent. We live in a reasonably built up area in Wantirna and the vent location would be some 3m approx from 2 boundary fences.

Would I expect most of the dust to be caught in the bin with only very fine, mainly invisible dust escaping outside, or will I come out to the neighbours back yard a brown color, the shade depending on the color of the wood I'm working at the time?

Thanks,
Andrew

Andrew,
there are other better experts than me but from what I know.....
if you have a well designed cyclone there will be very little dust after this.
cheers
Mick

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Originally Posted by ab1

I have been reading the Bill Pentz site and am considering building a cyclone unit.
I currently have a 3 phase 3 hp twin bag system sitting against the back wall of the shed. It is ducted to most machines and works reasonably well. Of course the shed has a nice fine mist of saw dust in the air that I assume escapes through the bag filter. This is not to mention the constant mess around the base with the plastic bags I try to use.

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Unless it has been physically damaged, once the filters have been conditioned, very little escapes from the filtering medium and what escapes is so fine it cannot usually be used. What you are looking at is dust that has filed to be captured at source. I'll bet your machines are throttled and/or you are using ducting that is too small. The next most common source of the problem is leaks, plastic bags rucked around the bag housing and small holes in the filters and bags, and then comes the dust left over after emptying the bags. All this is why it is best to vent externally.

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Unfortunately, I do not have a suitable location outside to have the unit, and it takes up a large amount of space in the shed.

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A good reason indeed for a cyclone.

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My question is regarding the external venting versus pleated filters on a cyclone unit. It makes sense to me to vent the unit outside. My concern is the amount of dust that would escape through the vent. We live in a reasonably built up area in Wantirna and the vent location would be some 3m approx from 2 boundary fences.

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. . . . . mainly invisible dust escaping outside, or will I come out to the neighbours back yard a brown color, the shade depending on the color of the wood I'm working at the time?

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Unless you fail to empty the bin it will all be invisible particles.

If you decide to go for a cyclone you will be going backwards unless it is a BP type or style. Older designs impose a significant back pressure on a system and will not have anywhere near the flow of a modern design.

I think the bp design looks good. He seems to have spent many hours in testing. I have an 8" duct approx 12m long in the shed with most machines having a 6" duct to them with a couple with 4".
I'm thinking about purchasing a 3phase 10hp 2880rpm motor as I have little power restraints in the shed.
I have downloaded the bp spreadsheet and am currently trying to understand it.
What is the optimin sire blower for this size motor?

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Originally Posted by ab1

I think the bp design looks good. He seems to have spent many hours in testing. I have an 8" duct approx 12m long in the shed with most machines having a 6" duct to them with a couple with 4".
I'm thinking about purchasing a 3phase 10hp 2880rpm motor as I have little power restraints in the shed.
I have downloaded the bp spreadsheet and am currently trying to understand it.
What is the optimin sire blower for this size motor?

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The flow determining component in your proposed setup is the 8" ducting - think of it as the speed limit to the entire system.
Provided the motor can physically turn the impeller and move the air flow governed by the 8" duct, what drives air through ducting is impeller pressure.
Impeller pressure is determined by design and RPM - .
Thus, 10HP is overkill for 8" ducting and while 10HP will drive a bigger impeller than a 5HP motor, the impeller pressure using a larger impeller won't increase significantly so it won't move any more air through 8" ducting than a 5HP motor.
Using a VFD to increase the motor speed on a 5HP motor will increase the pressure by 20% so is worth doing.
A 16" impeller will match with 8" ducting. If you go to 17" you should use 10" ducting.
A 10HP motor can drive a 20" impeller but it won't move any more air through 8"ducting than a 5HP motor and 16" impeller.
If you want to move the volume of air that a 10HP motor / 20" impeller are capable of moving you will need 12" ducting.

To really utilise the sorts of air flows that a 5HP/16" impeller can generate be prepared to get you angle grinder out and cut holes in machinery cabinets as these are the real governors on most systems.

Thanks Bob, your advice is very helpful.
I am reasonably happy with the suction of my current system. My main reasons for wanting to change is the external venting of very fine dust and the mess of emptying the bags. I use plastic bags with my system and steel clamps which drive me crazy. I was aiming to make a large, sealed, plywood bin on wheels I can easily disconnect and move to empty.
I will make a system with a 16" impeller. I have found a 10hp flange mount motor on Ebay for $200. This seems like a very good deal. I will look for a 5hp, but the running costs are not overly high, so I may end up with the larger. Overkill I know but flange mount motors are not as common as foot mounted.
I am considering making the impeller myself. I have a lathe and reasonable welding skills. I understand the main challenges are keeping the plate from buckling under heat and balancing. Would 2mm mild steel suit or should I consider heavier?
Another question I have is relating to the duct entering the cyclone. I currently have a duct entering from the left and the right of the unit. They both go into a Y piece and into the unit. Can I have 2 entries into the cyclone, or will this cause 1 of the entries to create friction due to the swirl of the air entering differently to the direction the impeller is spinning?
Thanks, Andrew.

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Originally Posted by ab1

Thanks Bob, your advice is very helpful.
I am reasonably happy with the suction of my current system. My main reasons for wanting to change is the external venting of very fine dust and the mess of emptying the bags. I use plastic bags with my system and steel clamps which drive me crazy. I was aiming to make a large, sealed, plywood bin on wheels I can easily disconnect and move to empty.

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I understand the mess but if it's outside it'd less important than inside the shed.

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I will make a system with a 16" impeller. I have found a 10hp flange mount motor on Ebay for $200. This seems like a very good deal. I will look for a 5hp, but the running costs are not overly high,

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It will be interesting to spin it up to 60Hz under load and see what power it needs to do that. I think a 20% increase in speed requires a 40% increase in power.

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so I may end up with the larger. Overkill I know but flange mount motors are not as common as foot mounted.

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It's quite easy to turn a foot mount motor into a flange mount using a large piece of angle iron and cutting a hole in the middle of one side for the shaft to pass through and for the the impeller to bolt onto while the other side mounts to the motor feet.
You could also turn a hole in a 8mm thick rectangular plate and then weld it at right angles to a foot mount plate with extra gussets for strength.

I have a 4HP motor that is foot mounted that I was going to use until I found a 4HP flange mount for $30 - Its an absolute beauty and spins up to 70Hz with very little vibe. I converted it to ∆ and it runs on a 240V VFD :)

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I am considering making the impeller myself. I have a lathe and reasonable welding skills. I understand the main challenges are keeping the plate from buckling under heat and balancing. Would 2mm mild steel suit or should I consider heavier?

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The Clearvue Impeller uses 11 and 14 gauge for the impeller disc and vanes. Building the impeller is no big deal if your lathe can turn and true a BIG disc. The big deal is getting it balanced and ideally this really needs to be done professionally especially if you want to be able to spin it to 60Hz. When I build mine I'll be going for something like 8 and 14 gauge because the disc can be trued fairly well on a big lathe and if it represents the majority of the weight more imbalance caused by the much lighter vanes can be tolerated. I was thinking of making up a jig that would temporarlly mate the impeller to the hub of a car wheel and taking it to a car tyre place and seeing if they can balance it.

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Another question I have is relating to the duct entering the cyclone. I currently have a duct entering from the left and the right of the unit. They both go into a Y piece and into the unit. Can I have 2 entries into the cyclone, or will this cause 1 of the entries to create friction due to the swirl of the air entering differently to the direction the impeller is spinning?

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Ideally the last junction or join to ducting should be at least 5 ducting diameters from the cyclone but if you can't manage it then it's not that critical on such a large system

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Originally Posted by BobL

The flow determining component in your proposed setup is the 8" ducting - think of it as the speed limit to the entire system.
Provided the motor can physically turn the impeller and move the air flow governed by the 8" duct, what drives air through ducting is impeller pressure.
Impeller pressure is determined by design and RPM - .
Thus, 10HP is overkill for 8" ducting and while 10HP will drive a bigger impeller than a 5HP motor, the impeller pressure using a larger impeller won't increase significantly so it won't move any more air through 8" ducting than a 5HP motor.
Using a VFD to increase the motor speed on a 5HP motor will increase the pressure by 20% so is worth doing.
A 16" impeller will match with 8" ducting. If you go to 17" you should use 10" ducting.
A 10HP motor can drive a 20" impeller but it won't move any more air through 8"ducting than a 5HP motor and 16" impeller.
If you want to move the volume of air that a 10HP motor / 20" impeller are capable of moving you will need 12" ducting.

To really utilise the sorts of air flows that a 5HP/16" impeller can generate be prepared to get you angle grinder out and cut holes in machinery cabinets as these are the real governors on most systems.

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All great advice.

The importance of ensuring your machine ports/hoods are in good order cannot be overstated. Airflow tests of my system (3.3 kW CV 1800 with a VFD (running at 60 Hz) and 6" ducts) clearly demonstrate that the ports/hoods are the limiting factor. I know BobL said that, but I fear many get focussed on motors, impellers and ductwork and do not grasp the importance of this factor. I could put on a bigger motor and impeller, and it would make little to no difference.

Have fun!

John

Hi Andrew,
Here's a couple of pics that might be useful
Attachment 309095Attachment 309094Attachment 309096Attachment 309097Attachment 309098

1st one is the chip collection box, I have since lined this with 3mm ply which makes it easier to empty, one day I will make a box that goes inside this one so I can just remove the box with dust in and cart the whole lot away with having to shovel it out, one day!

2nd is the 3kw (4hp) motor and flange mount (the blue section) these are generally available from any motor supplier/rewind place, they will want to know the brand and frame size, from memory 3kw is a 100L, if in doubt take the whole thing in if you go that way. All you need to do is remove the drive end housing on a foot mount and replace with flange mount and your good to go. I really think that 10hp is way more than you need, not too mention the weight of getting it into position, 5 hp would be a large size for a one person single machine at a time operation, I have no real issues with 8" duct a 12" fan wheel and the 3kw motor.

3rd, 4th and 5th are views looking up into the fan from the outlet of the cone, I made this fan, I used 6mm plate for the backing disc machined flat on both sides, I wouldn't go any thinner than this by the time it is machined, ended up about 4 to 5mm thick, also machined was the flange mounting hole and 6-8mm cap screws to suit the mounting flange, the flange was welded to a "weld on hub" (available from any mechanical drives supplier) with a taper lock to fix it to the motor shaft, the blades I machined from about 5" pipe to be about 2mm thick which were then welded onto the backing disc and then the shroud onto the blades, if I were to make another one I would make it 14" diameter and a few other mods to improve flow.

A few pics of a smaller fan wheel
Attachment 309099Attachment 309100Attachment 309101Attachment 309102

This is the first one I made, I then made a second using the larger blade on the right which is the one in use atm. I statically balanced the second one by adding weight to the backing disc, been in use a number of yrs now but it would be better option to have it dynamically balanced tho.

Hope this helps.



Pete

Pete, It looks like your WEG motor
https://www.woodworkforums.com/attach...4&d=1339077290
Is similar to mine - Its also a WEG 4HP
https://www.woodworkforums.com/attach...d=307894&stc=1

Cheers
Bob