Thread: round DC help

Originally Posted by hughie

Some time back there was a thread about dust collection with a new production. A round dust scrubber that is suspended in the worksop to remove the unseen small particles.

But darned if I can remember any details I wonder if anybody out there can remember

Not sure of the thread, but I believe you are thinking of Microclene which filter down to about a micron, left ruuning a couple of hours after your finish your woodwork
Willy

MC1210 also has a smaller cousin MC420

Another option - I've been using a Sunbeam air cleaner (with HEPA filter) for years, it's a cheaper option, but can't comment on the volume/min of air scrubbed compared to the above models. Here are some similar options to my Sunbeam on eBay.

Hughie,

I think Microclene is the answer you are looking for BUT after reading the reply by Neil S I'm liking his idea a lot!

Add Neil's idea to your ingenuity and I foresee a Hughie style DC in no time.

Cheers mate

By the way, the lathe has done its first bit of work. It took a while to get going though - all the typical questions like what *********** have I done etc. Then remembered you mentioned the microswitches. It worked a lot better with the doors closed

I had a look at the microclene air flow specs specs and based on what other manufacturers do with regards measuring air flow rates the quoted flow rates need to be divided by 2 when the filter is clean, and then don't forget it goes down from there as the filters block up.

Then the claim that it performs "X complete changes of air p/h to a Y cubic metre work space" can be misleading.
At best these things filter half the room air in the time it takes to pass all the room air through the filter. The reason for this is some of the clean air is refiltered over and over again. In addition the filtering process warms the air so the clean warm air returns preferentially back to the ceiling and the cooler dusty air stays in the bottom half of the room.
This means at best in the first pass it only cleans 50% of the air, in the next pass it cleans 50% of the remainder, and in the next pass 50% of the remainder.
This assumes a room that is totally clear of obstructions etc so a more realistic series is one where only ~1/3 of the room air is put through the filter at the equaivalent of every room change.
Next they only capture 65% of the very fine particles so they take even more passes to clean the air.

I'm not saying they don't work (I have one - not a microclene) but they take much longer to remove the most health significant dust than they quote. I would at minimum divide any quoted air filter room turn over spec by 4.

For woodworking activities, especially turning, which is BTW one of the worst dust making activity for most woodworkers, room filters simply cannot cope with the volume of dust produced while the activity is taking place. The best way to keep your shed clean is to grab the dust at the source of production using a large air flow (1000 cfm). The air flow has to be as close as possible to the dust source and not in your shed ceiling. The DC should then be left running for some time after the last dust making activity as this will clear a shed much faster than a room air fliter. Ideally your dust collector is not in the shed as all these things (including room air flitters) (eventually) leak so they are not as clean as we'd like them to be.

Room air filters are very useful to leave running after turning off a DC as they use less power and are mucg quieter than DCs. They are especially useful to clear a shed when you are not there, and for preping an area prior to applying finishes as they not only remove wood dust but other dusts from the air..

If you decide to get one I would go for the biggest one you can afford, certainly for woodworking I would not start at anything smaller than the MC1201.

Thanks guys, OK, BobL my little shed is 54.6 cum and I have divided it in half for the turning section so its now 27.3 cum. So by your reckoning I should OK as the smallest one MC420 is supposed to move 420cum per hour. I fully intend to rig up a ducted system and I have a 1hp blower 240v and a 3 phase .5hp. Either one should do, as I will have at worst 4 outlets all with gates. The Sunbeam sounds interesting will look into it further along with the rest of the info.

Originally Posted by hughie

Thanks guys, OK, BobL my little shed is 54.6 cum and I have divided it in half for the turning section so its now 27.3 cum. So by your reckoning I should OK as the smallest one MC420 is supposed to move 420cum per hour. I fully intend to rig up a ducted system and I have a 1hp blower 240v and a 3 phase .5hp. Either one should do, as I will have at worst 4 outlets all with gates. The Sunbeam sounds interesting will look into it further along with the rest of the info.

If you are turning and you do not want to turn in a bath of fine dust then a room filter is not the way to do it. It takes less than 2 minutes of conventional turning to contaminate a 6 x 4 m shed beyond the OHS dust limit and no commercially available room air filter will keep up with the rate of dust generation.

The way to prevent a bath of fine dust building up in the first place, especially a small work area, is to use something that will generate 1000 cfm minimum at the dust site.

A 1HP DC can at most pull 350 cfm so it will also not keep up.

A stock 2HP DC pulls about 600 cfm so it will also not keep up. There are ways of modifying a 2HP DC to get more than this but significant radical surgery is needed to convert the DC to an all 6" system - look here for what I am doing about this. I have my doubts this will ever manage to achieve 1000 cfm in a real situation where anything more than a few metres of ducting are being used so this means the DC cannot be placed outside a shed.

A 3HP DC will generate about 1250 cfm and is the minimum stock DC that will sufficient cfm over a reasonable distance of ducting and be able place the DC outside your work area.
BUT
You must use 6" ducting all the way from the worksite to the DC. Most DCs only have 4" inlets but they have to be removed and replaced with a 6" inlet.

A 4HP DC will generate about 1650 cfm and would be needed in a large shed with long ducting runs.

At the lathe end of things you need can maximise the flow by using a bell mouth hood like this.

The flow into these hoods is such that much higher air speeds are achieved further out from the front of the mouth than any other hood.
This means the air speed rips the fine dust away from the site where the dust is generated better than any other hood.

This hood is discussed in this thread - https://www.woodworkforums.com/f200/a...26/index6.html
Unfortunately you will have to wade through a pile of irrelevant posts but you can still see the development and measurements of how we (it was a group effort) developed this hood.

When I turn I still have a lot of sawdust on my bench and on the floor but they are all large chips and my particle detector picks up very little fine dust above the natural background in my shed.

Now once you have this setup, depending on what you are turning you may still have some fine dust escape in your shed so when you finish turning you should keep the DC running for 20-30 minutes (time depends on volume of turning space) to make sure you clean up the air in the shed.

Now if are like me you hate the sound of the DC running so I turn off the DC about 5 minutes after I finish and then fire up the room air filter as it is quieter and uses less power. The room air cleaner is not needed if you are happy enough to run the DC itself. The room air filter will eventually clean a shed to better than external background so if you are fussy about dust free finishing they are excellent at doing this.

Clear as mud?

Some people like to wear masks as well or instead of going to this trouble, but masks alone have a lot of issues I won't go into here.
Masks as a form of extra protection are fine

I could go into much grimier detail if you need to.
Cheers
Bob

Phew! Bob thats a fair bit of info. I should have mentioned that I am also fitting a a large exhaust fan in the wall its a slow revving reasonably high volume fan off a split AC unit.
The main reason for a room fliter aka scrubber is for finishing in a reasonably clean room. I would probably switch it on after turning etc prior to getting into finishing side of things.

Originally Posted by hughie

Phew! Bob thats a fair bit of info.

Sorry but that is the very short condensed version.
For the long version try Bill Pentz website.

I should have mentioned that I am also fitting a a large exhaust fan in the wall its a slow revving reasonably high volume fan off a split AC unit.

The axial type fans used in exhaust fans are not very efficient and although it won't work anywhere near as well as extraction at source, any ventilation that pulls air from outside the shed into the shed is better than none.
Here are some ways of making this work better for you.
-place vents that let air into the room in as straight a line as possible between the exhaust fan and the dust source. This will set up a preferential flow line that will reduce the amount of fine dust that gets into the room.
- close any openings (doors or windows) or vents that are on the same wall as the exhaust fan, otherwise the exhausted air and dust will go straight back inside the shed.
- locate the exhaust fan as high on the wall as possible, and the intake vents below half height to help clear the room faster than otherwise. I would avoid placing the intakes at ground level otherwise it may drive dust from the ground into your shed.
- Most people make the intake vents too small. The total area of the intakes should be about twice the area of the exhaust fan.

The main reason for a room fliter aka scrubber is for finishing in a reasonably clean room. I would probably switch it on after turning etc prior to getting into finishing side of things.

Just be aware that if you don't extract at source there will be far more dust in the room and it will take longer to clean it up.

The fan will be at one of the shed and the door will be open at the other, its actual dia is better than 600mm. I had intending to build and fit to each lathe a ducted system with gates to localize the extraction. The runs will be short, at worst perhaps 3-4m from lathe to DC. The DC will have a cyclone set up and at this stage 1hp set up outside under an awning with a silencer fitted. I will be using Bill Pentz design for the cyclone and silencer.

Currently the plan is to have both lathes and the bdansw connected to the system and the wall fan will run at the same time as general evacuation fan it should be capable of causing a constant air movement from the door to the outside. I am not looking for a gale, but rather enough movement to pull the near invisible dust and expel it. It will run whether lathe is going or not, be a bit chilly come winter tho'.

Originally Posted by hughie

The fan will be at one of the shed and the door will be open at the other, its actual dia is better than 600mm.

That sounds very good.

I had intending to build and fit to each lathe a ducted system with gates to localize the extraction. The runs will be short, at worst perhaps 3-4m from lathe to DC. The DC will have a cyclone set up and at this stage 1hp set up outside under an awning with a silencer fitted. I will be using Bill Pentz design for the cyclone and silencer.

A Bill Pentz style cyclone is designed for a 4HP motor and a 14" impeller. If you fit one to a 1 HP system it won't work and it will let a lot of dust through. If you downsize the BP cyclone to a 1HP it develops a significant back pressure that it will throttle the system and produced a reduced flow. If you want the maximum flow from any small DC then it is much better that you do not use a cyclone or chip collector (CorCC) with it. Yes you will have to empty and clean the bags more often but if you use a CorCC on a small DC you should still clean the filters/bags every time you empty the chip bin. Most people who have a CorCC on a small DC do not do this and the air flows I have measured on these systems clearly demonstrate that they compromise their flow by using these devices. A BP cyclone fitted to an appropriate size motor and and impeller is so good at filtering out fine dust that it does not need an end filter.

Currently the plan is to have both lathes and the bdansw connected to the system and the wall fan will run at the same time as general evacuation fan it should be capable of causing a constant air movement from the door to the outside. I am not looking for a gale, but rather enough movement to pull the near invisible dust and expel it. It will run whether lathe is going or not, be a bit chilly come winter tho'.

Yep - that's the penalty for any system that vents outside. In my case it vents my air-conditioned air in summer but it is the only way of insuring against dust leaks which I have found to be the "elephant in the dust corner"

Originally Posted by BobL

A Bill Pentz style cyclone is designed for a 4HP motor and a 14" impeller.

I have been running a Pentz cyclone on a 3HP/3Ph motor with a 12" impeller for a few years now and in that time I would only have had a cup full fine dust get through to the filter (probably because I let the cyclone drop box overfill), but I am running the Pentz long cone specification which has the optimum efficiency.

I haven't tested the airflow at the inlet, but I have had a tight leather glove sucked right off my hand...

Originally Posted by NeilS

I have been running a Pentz cyclone on a 3HP/3Ph motor with a 12" impeller for a few years now and in that time I would only have had a cup full fine dust get through to the filter (probably because I let the cyclone drop box overfill), but I am running the Pentz long cone specification which has the optimum efficiency.

I haven't tested the airflow at the inlet, but I have had a tight leather glove sucked right off my hand...

Before I comment on this I would need to know what sort of final filters and what size ducting you have?

Originally Posted by BobL

Before I comment on this I would need to know what sort of final filters and what size ducting you have?

Minimum duct size is 6" diameter with a pleated cartridge filter (I think it's about 1200mm high and 600mm diameter).

I do place the intake right next to the dust source, which in my case is primarily sanding dust off the lathe. The distance between the intake and point of dust generation is usually just mm. I constantly readjust the position of the intake to optimise for dust pick up.

My best measure of escaped fine dust is how much collects on the HEPA filter in my air cleaner. I'm surprised how relatively clean it is after hundreds of hours of run time.

However, I defer to Bill Pentz on all matters relating to dust collection. Do as he says and ignore anything that I have said that doesn't comply with his advice.

Originally Posted by NeilS

Minimum duct size is 6" diameter with a pleated cartridge filter (I think it's about 1200mm high and 600mm diameter).

I do place the intake right next to the dust source, which in my case is primarily sanding dust off the lathe. The distance between the intake and point of dust generation is usually just mm. I constantly readjust the position of the intake to optimise for dust pick up.

My best measure of escaped fine dust is how much collects on the HEPA filter in my air cleaner. I'm surprised how relatively clean it is after hundreds of hours of run time.

However, I defer to Bill Pentz on all matters relating to dust collection. Do as he says and ignore anything that I have said that doesn't comply with his advice.

Sounds very good . I am surprised you get sufficient flow to catch all the fine dust with a 12" impeller but if the intake is constantly adjusted to be mm from the dust making point this will easily explain what is going on. How long is the duct from the lathe to the cyclone?

As for the efficient cyclone operation I am only echoing what Bill Pentz says about impellers and cyclones.

Do you vent inside the shed because if ". . . for a few years now and in that time I would only have had a cup full fine dust get through to the filter" then you could vent outside and remove the filters completely and improve your flow.

Although it sounds like you don't need it, given your motor is 3 phase you could also fit a VSD and speed up the RPM to 60 Hz for a 20% improvement in flow.