Thread: Dust Extraction / Control used by woodturners

Valuable contribution to the topic there, Bob, particularly your observations on leaks.

I have suspected that leaks could be the weak point in my DC system. However, without the benefit of dust measuring equipment I have no way of getting a reading on that.

Bob, have you written elsewhere on the measuring equipment that you are using?

Originally Posted by NeilS

Valuable contribution to the topic there, Bob, particularly your observations on leaks.

I have suspected that leaks could be the weak point in my DC system. However, without the benefit of dust measuring equipment I have no way of getting a reading on that.

Cyclones have a clear advantage as far as leaks go because the collection bag/chamber is under negative pressure. Only the dusting on the down flow side of the impeller is pressurised which can be reliably sealed and have it stay sealed. Most leaks on DCs occur around or in the collection bag which being positively pressured causes problems

Bob, have you written elsewhere on the measuring equipment that you are using?

I'm using an ARTI 6 channel particle counter with micron particle size ranges of <0.3. 0.3 - 0.5, 0.5 - 0.7, 0.7 - 1.0, 1.0 - 2.0, 2.0 - 5.0 , >5.0.
FOr air flow I'm using a TSI digital and Kurz Analog hotwire anemometers.
The TSI has a max range of 20m/s and the Kurz is 30 m/s so I use test pipes with larger diameters to measure higher air speeds.

Bob,
Interesting points. Leaks are a huge problem and probably account for more flow loss than the corrugated type tubing/pipes. When I set up my centralized system, they recommended taping all seams as they supplied snap lock type sections of metal pipe. They also said to tape and/or silicone caulk all joints. For their hook ups at the machine, all had neoprene type gaskets at all junctions, so they should have been pretty clean.

I am not sure about how accurate the micron rating is on the various filters. The old cloth bags were 5 micron at best (mine was about 20 years ago). Every time I started it up, there would be a dust plume from the bag. I do think that the ratings are better on the newer machines. I guess it comes down to design and 'respectability' of the manufacturer. Like Mark Twain said, "There are 3 kinds of lies in this world, lies, damned lies, and statistics". One turner here, I think but, am not sure, he was the guy who started Clear View cyclones tested a bunch of different dust collectors. Almost none of them matched the manufacturer's specs, and some didn't even come close. One manufacturer even threatened him with a law suit if he didn't retract his statements.

I don't know if you did a comparison chart, but I would be interested in seeing it.

robo hippy

Originally Posted by BobL

I'm using an ARTI 6 channel particle counter with micron particle size ranges of <0.3. 0.3 - 0.5, 0.5 - 0.7, 0.7 - 1.0, 1.0 - 2.0, 2.0 - 5.0 , >5.0.
For air flow I'm using a TSI digital and Kurz Analog hotwire anemometers.

Thanks, Bob.

Originally Posted by robo hippy

Bob,
Interesting points. Leaks are a huge problem and probably account for more flow loss than the corrugated type tubing/pipes.

In terms of loss of flow rate, lt depends where the leaks are. The leaks I was referring to are on the positive pressure side of the system ie after the impeller, and these will actually assist flow at the input side of the system.

When I set up my centralized system, they recommended taping all seams as they supplied snap lock type sections of metal pipe. They also said to tape and/or silicone caulk all joints. For their hook ups at the machine, all had neoprene type gaskets at all junctions, so they should have been pretty clean.

I probably should be more rigorous about this but I don't worry too much about leaks on the input side as they under negative pressure still collect dust from the shed. About half my junctions are taped and these tend to be those that are likely to be more permanent. If there is a chance I will be modifying junctions I usually leave them untaped.

I am not sure about how accurate the micron rating is on the various filters. The old cloth bags were 5 micron at best (mine was about 20 years ago). Every time I started it up, there would be a dust plume from the bag. I do think that the ratings are better on the newer machines.

It took me a while to work this out but the classic "dust plume from the bag on startup" is in many cases mostly not from the bag. That is the dust that has settled out around the DC either from leaks, or the failure of the DC to capture fine dust at source (most likely), or from something else like using a vacuum cleaner. After some use, most vacuum cleaners (even really expensive ones) output more fine dust than they collect. They do this because the motor cooling look minces larger dust particles into finer ones. This plume of dust from a filter/bag is a good measure of what is not being collected at source and a sure sign that a DC is not up to spec. Sometimes this is due to the small ports being used on machines being too constrictive to air flow. A good test of any DC system is to lay out a large clean (ie just washed) cloth after doing a days worth of woodwork and leave it for a few days. Then carefully collect it up and take it outside in full view of early morning or late evening light and shake it and see how much dust comes of. Bear in mind you might only be seeing a few percent of the actual dust as most of it will be invisible.

The single number micron ratings of bags/filters (ie 5 microns) is effecfively useless without the efficiency at that micron rating, and whether those ratings are for a new or conditioned bag. The filter/bag conditioning process is so variable (wood type, WW activity, humidity ext) that it would be impractical for manufacturers to provide any sort of accuracy for a conditioned bag. A new bag rating may also not be indicative of it conditioned performance which might still be OK even though it is relatively porous when new. But as I said before all this seems secondary to stuff like leaks and poor collection at source.

Perhaps more significant than micron ratings are manufacturers claims on DC Air flow. I have communicated with many wood workers who ask me what I think about (generic) 2HP DCs. Most of them have skim read Bill Pentz website and picked up on the 1000 cfm requirement for fine dust control and then read on retail websites that their 2HP has a flow rate of 1200 CFM but his is complete bollocks on a variety of fronts. The most I have measure on 3 of these as supplied by the retailer is 600 cfm. I have seen the measurement protocols for a manufacturer of these generic DCs and the test is not for the DC it is for the impeller alone, ie no adapters to 100 mm hose on the input side, no filters or bag housing, no flexy connection to the bag housing AND they perform a single point measurement in the middle of the exit so there is no allowance for wall friction which can be of the order of a 25% reduction to real flow. The real flow of those 2HP DCs as supplied by the retailer using one of the 2, 100 diameter input ports is ~400 cfm. Using both of the 100 mm diameter inputs the flow is <600 cfm - the only wood working machine this is probably adequate for is a drill press .

. . . . . Almost none of them matched the manufacturer's specs, and some didn't even come close. One manufacturer even threatened him with a law suit if he didn't retract his statements.
I don't know if you did a comparison chart, but I would be interested in seeing it.

If you read my threads in the DUST forum you can see that I report on a number of DCs and VCs but I do not mention any brand names because of what BP experienced. What I do feel safe about saying is none of the DCs I have measured for flow rates measure up to the manufacturers claims.

come on you fellow wood turners,

this is not an inquisition. I (and I expect many others) would like to know what others are actually doing in regards to dust extraction to get a more balanced feeling for 'what is normal'. I would also like to know what others think about what they are doing. I know the path I am currently thinking of but want to get a broader view. I'd hate to think I went down a religious path (no offence intended) but I expect most people will get my drift.

thanks

Mick

Mick, I would expect after BobL's informed posts many of us are thinking something like '#####, my kit is not up to speed and/or I've overlooked something' and so will be reluctant to admit to our failures.

For your own setup, there's all the info you need here and elsewhere on the web.

Set it up and let us know what you opted for and why.

How about, unless invited, I agree to butt out of any criticism or comments on members setups?

Originally Posted by BobL

How about, unless invited, I agree to butt out of any criticism or comments on members setups?

Bob - I hope you do not as there is no doubt that you are making an extremely valuable contribution and I for one am extremely grateful (even if sometimes it may not seem that way ).

I also suspected what Ern is saying ie: many feel what they have done is 'not really good enough' so are reluctant to comment. From that view, it makes me feel more confident that I am going down the right path of trying to achieve the magic numbers to get fine dust extraction at the source.


cheers


Mick

Yeah, I'm with Mick. Friendly and informed comment is invaluable, and I've learned a lot from Bob's posts.

Eg. while I knew that some folk have contracted an asbestos-related disease via the clothes of a worker exposed to the stuff I never made the connection with wood dust

Just to add regarding my complete setup: after a number of years I was seeing dust settle both in the workshop and in the workshop annexe which houses the dusty. Following a query about the life of pleated paper cartridges, Bob suggested I check for leaks. Bingo, the rubber sealing ring at its bottom was leaking.

And I replaced the prefilter on the box scrubber. The original type was no longer available. The replacement is not working as well and again that looks to be due to a poor seal.

Originally Posted by rsser

Yeah, I'm with Mick. Friendly and informed comment is invaluable, and I've learned a lot from Bob's posts. Eg. while I knew that some folk have contracted an asbestos-related disease via the clothes of a worker exposed to the stuff I never made the connection with wood dust

The risk is nowhere near as high for second/third party exposures with wood dust as it is for asbestos otherwise we'd be seeing clear problems with turners families. My concern is more with the turners than only wear masks as a form of dust control and end up with many grams of fine dust on and in their clothing and continue to wear the clothing for hours after turning.

Here is another sobering piece of information showing relative exposure by different woodworking occupations.
I have posted this before but I cannot find it so I will post it again here.
The Australian Standard for wood exposure is 1 mg/m for hardwood and 5 mg/m³ for softwoods but these are considered too high in terms of world's best practice.
This chart also does not take into account "particle sizes" since fewer fine particles will have lower mg/m3 but in turn are likely to cause more health problems than larger particles.
For example the European Medical Standard for wood dust exposure is 0.1 mg/m³ for particles 10 microns or smaller and turning typically produces a lot of very fine dust
The average exposure for turners well above the recommended OHS levels.
Maximum levels are the highest of all specific wood machinery type operators and even the minimum exposure is above the recommended hardwood level.

I have been turning for 15 years and luckily in my first year of turning I met a retired production turner who warned me about dust and scared me into taking it seriously

I use three ways to help control dust:
1. I wear a trend respirator helmet all day long
2.I have a microclean air scrubber running all day and an hour after i finish working.
3.I have a 2hp cyclone extractor which sits just outside of my workspace and is ducted in with 2.5m of 8" duct

I use the extractor when i'm sanding and if i'm turning something very dusty

I would value any advice on one thing and that is that at the end of the 8" duct I put a Y piece on with two 4" ports, I tend to cap one port and use a metre of 4" bendy hose from one of those ports to the closet point that the dust is leaving the workpiece.
would i be better trying to find a larger diameter bendy hose and doing away with the y piece? or using two bendy 4" hose's and not capping one port off?

here's a pic of me at the lathe that shows the end of the duct and the y piece, the bendy hose is on the shelf at the back.

Originally Posted by cornucopia

I use three ways to help control dust:
1. I wear a trend respirator helmet all day long
2.I have a microclean air scrubber running all day and an hour after i finish working.
3.I have a 2hp cyclone extractor which sits just outside of my workspace and is ducted in with 2.5m of 8" duct

Firstly good on you for taking dust seriously.

If a cyclone was setup and working right you would not need either respirator or an air scrubber.
I can expand on this if you would like more details.

Any DC/cyclone sitting just outside a workspace doesn't help dust problems much as the DC/cyclone creates a negative pressure inside a workspace which draws any fine dust that exits the DC/cyclone back into the shed. A DC/cyclone should be where possible located outside on the wall opposite the major opening to the shed. This increased the possibility of fine dust being dispersed and carried away before it can get back into the shed. If this is not possible in your case then I can understand why you need to wear a respirator.

In terms of ducting and connectors the best way to increase flow (thus capturing more dust at source) is to remove all 4" ducting and ports as that just reduces flow. The most a 4" dust/port can transmit under the pressures generated by any conventional impeller used in DCs or cyclones is 400 CFM.

At 8"m the theoretical flow rate is ~1800 cfm but a 2HP with what looks like a 12" impeller will top out well before that, probably around 1350 CFM without any resistance. The Axminster cyclone design is quite an old one so I would expect it to significantly resist the flow so it will be less than this, but using 6" or more ducting should still generate a better flow than 2 x 4" individual ducts so you are better off using either 6" or 8" ducting. I seriously doubt whether you would get much more flow using 6" versus 8" ducting on that cyclone.

Using bigger ducting reduces air speed and increases flow which means more fine dust is collected but few chips may be collected. Some turners don't like this but remember that the big chips represent less risk than the fine dust in terms of respiratory problems.

thank you for your reply

the impeller in this machine is just shy of 17" wide by 5" deep, i know this because after a few months of owning it it kept popping capacitors and i checked that the impeller could spin freely and the motor had no bearing issues. I also had to have a dedicated 16 amp supply fitted to it as when it starts up it needs the juice to get the impeller turning!!

I think i understand what you mean- so if i keep the 8" from the machine into my workshop but remove the 8" to 4" Y and try to find an 8" to 6" reducer and a 6" bendy hose i can improve the performance- is that right?