Thread: Beginning my dust extraction journey and looking for help

Originally Posted by BobL

I assume your enclosure is inside the shed? If so the plasterboard acoustic batt combo will be fine. Door needs to have a really good all round seal. Preferably set into a frame like a room door but don't forget to include a frame/seal at the bottom. Sliding doors or spurs flay against and opening are harder to seal. If you are enclosing outside seal does not need to be as tight.

Yes (unless I decide this is all too much trouble). I can't see a way to make outside viable. Had a bit of an attack when I went down to scout out a 1.5mx1.2 area, plus space for a baffle box and exhaust vent. Am now faced with the decision of starting small - 2 or 3HP, see what works and moving up or just jumping in at the big end (ie CV/PFlux). I figure I should size the enclosure for future expansion so need to research those now - turns out the footprint of a 3HP motor with double bags is larger than that for a PFlux. Am disappointed there seems to be a dearth of incremental value in the space between $600 and $3400.

I feel like I should avoid the extractors with impellers at the bottom if I'm ducting via the ceiling. Is an extra 2-3m (to come down to the impeller then up to the dust collection bag) something that should affect my decision making?

Spyro's particle counter can be bought in ebay for under $60.
I bought one of these about 30 months ago and have done tests against other particle detectors.
See review at Developments in Dust Sensor tech
That detector uses a Plantower 5300 particle detector which is not the most recent Plantower detector but it still provides reasonable (and useful) results.
My testing shows it underestimates particle counts between 20 and 50% depending on where in the scale dust is being measured
The Dylos was found to produce similar results and even though it records data I don't think it's worth the price given data storage PM2.5 detectors can be bought for about $150.

While this sounds terrible it is not the main source of inaccuracy. The greatest source of inaccuracy being that the detector has very little chance of more closely measuring what dust levels operator is being exposed to unless the detector is close to the operators mouth. This is the main reason I developed a logging wearable dust detector. the difference between the results from a wearable versus a detector place a couple fo meters away can be as much as 100x. The downside of moving the detector closer to the dust source is you may more easily damage a wearable .
Wearable.jpg

Despite this these cheap PM2.5 detectors are still useful and I do recommend getting one if you are interested in pursuing general dust monitoring. Lets face it, most (specially DIY) operators do not spend that much time making dust - they spend most of their time working in a dusty environment so this is where their greatest overall exposure will be.

Every now and they I get a surprise. I loaned one of my standard dust detectors to a mate who has a single operator commercial (5+m high, 140m^2 ) woodwork shop with very large (half wall) roller doors at each end of the workshop. His production (dust making) activities are relatively light - closer to that of a DIY than a commercial workshop. The main reason for this is he buys stock that is close to required dimensions so there is very little resawing (14" euro slider) or thicknessing (12" Hammer) etc. His DC is a large double bag Felder , located inside the is workshop but next to one of the big sliding doors The ducting is mostly 6" but there is also some 4". There is a fair bit of dust settled over everything BUT his PM2.5 dust levels rarely go above 50µg/m^3. Seems to break every rule in the dust control book but what I think it shows is the power of ventilation.

At some point I stapled some velcro on an old top and I was wearing it on my shoulder

I think ventilation is a life saver. I know a couple of old cabinetmakers who started in terrible conditions overseas (Greece) and continued in terrible conditions for decades, basement shops, no DC etc. They're still ok somehow (smokers too LOL), but they both told me they always had open doors and fans and moving them around to create a draft through the shop, whatever they were doing. Must have helped them a little bit.
But even today, a couple of times I've had the chance to go into commercial woodshops, their DC can only be described as crap. You can see the obvious mistakes everywhere, DC machines indoors, big ducts but with small openings on the machinery, unnecessarily long lengths of hose or duct, 90 degree bends etc. Most of all you can actually see the fine dust settled everywhere. I think the safety inspection (if there is one) is just ticking boxes but not actually measuring the result.

Originally Posted by Stopblock

I feel like I should avoid the extractors with impellers at the bottom if I'm ducting via the ceiling. Is an extra 2-3m (to come down to the impeller then up to the dust collection bag) something that should affect my decision making?

There is a simple way to loose those two 90º elbows and 2-3m of duct. Unbolt the bag housing rings from the ends of the "Y"bendy duct bit after the impeller and flip the base up so it can be bolted to the ceiling or put it on a stand. Then bring the bag housing rings back to the "Y"bendy duct bit and bolt them back on in the same orientation as they were. The filters are still up and the bags down but the impeller is at the ceiling where your ducts are. You might have to put a box on the ground so the lower bags can sit on something. Still best to have it enclosed outside or closeted inside and vented out. You're lucky to have a favourable climate for that kind of installation.

Pete

Originally Posted by QC Inspector

There is a simple way to loose those two 90º elbows and 2-3m of duct. Unbolt the bag housing rings from the ends of the "Y"bendy duct bit after the impeller and flip the base up so it can be bolted to the ceiling or put it on a stand. Then bring the bag housing rings back to the "Y"bendy duct bit and bolt them back on in the same orientation as they were. The filters are still up and the bags down but the impeller is at the ceiling where your ducts are. You might have to put a box on the ground so the lower bags can sit on something. Still best to have it enclosed outside or closeted inside and vented out. You're lucky to have a favourable climate for that kind of installation.

Pete

That’s what I did. My main duct goes up from my lathe, has a 90° at the top and goes straight through the wall into the impeller.

Summary in the hopes of getting my thoughts straight and to record thinking. Criticism welcome.

***** Issues
2 Issues:
- air exchange (replace air in the workshop 20 times per hour)
- dust extraction (collect dust at source)

Secondary issue: ducting
Dust extraction and ducting thoughts to follow.


*** Units
1 m ~= 3.281 ft
1 m3 ~= 35.32 ft3
1 CMH ~= 0.59 CFM

***** Blower Capacity for Air Exchange:
Shed size: about 55m3 ~ 1942ft3.
Therefore, for 20 changes of air per hour
in CMH = 1100 CMH (seems to be the units used for cage fans)
in CFM = 38840 ft3 per hour or 647CFM (units used for dust extractors)

At 647 CFM I will need roughly 6" ducting for the exhaust.

First thing should therefore be to acquire a fan with this capacity.

***** Air Exchange Options

Recommended fans are "squirrel cage fans" and "hydroponic fans"
"Squirrel cage" fans don't seem to have much of a retail following in Australian searches at least not with this capacity, much more prevalent are "inline duct fans". Many candidates do not list any metrics either for noise or how much air they shift or both. Price seems largely unrelated to CFM.


This guy
Dynabreeze 200mm Yellow Extraction Fan | Bunnings Warehouse
purports to give 25m3 per minute (1500CMH, 882CFM)

Hydroponic inline fans seem to be substantially more expensive for the same CFM. Seem easier to duct though and quieter? What's the point of a hydroponic fan?


***** Air exchange issues
Noise
Ducting to window.
At 20 exchanges per hour workshop will be the same temperature as outside air.

20 exchanges per hour is cautious. Measurement may show lesser exchange is sufficient in practice.

Originally Posted by BobL

What have you got that powers the workshop?

20A circuit breaker with a C curve, shared with the laundry. Everyone went out! Baffled as to where the other 20A circuit goes...

Originally Posted by Stopblock

20A circuit breaker with a C curve, shared with the laundry. Everyone went out! Baffled as to where the other 20A circuit goes...

That will be enough for one 2HP or less machine but you will need at least another circuit, preferably one that will take a 15A GPO

Originally Posted by Stopblock

This guy Dynabreeze 200mm Yellow Extraction Fan | Bunnings Warehouse
purports to give 25m3 per minute (1500CMH, 882CFM)
Hydroponic inline fans seem to be substantially more expensive for the same CFM. Seem easier to duct though and quieter? What's the point of a hydroponic fan?

The hydroponic ones are quieter and more efficient than Axial fans.
Please ear in mind there are Axial and Centrifugal Hydroponic fans - make sure try looking at the latter.
The Hydro centrifugal fan ratings will be closer to actuality than the axial type.

That yellow fan will be quite noisy.
In practice it won't be moving 882 CFM, probably closer to 440 CFM

(20 exchanges per hour is cautious. Measurement may show lesser exchange is sufficient in practice.

Yes but given manufacturers fan ratings are nearly all over estimates shooting for the 20 Room Air Changes per hour (RACH) should get you 10 RACH

Don't forget if your DC is venting outside the shed you can also use your DC to assist with venting, but given DCs consume lots of power I would tend to use a DC just for say 10-15 minutes after finishing dust making. This should give you the full/real 20 RACH and help get rid of the bulk of the remaining fine dust, but after that running a real 10 RACH should take care of teh remainder.

FWIW I have 3 ways of venting
Squirrel cage fan 1, 1200 CFM, 20 RACH
Squirrel cage fan 2, 1600 CFM, 27 RACH - this is at the MW end of the shed.
DC , all gates Open , 1200 CFM, another 20 RACH

Originally Posted by BobL

That will be enough for one 2HP or less machine but you will need at least another circuit, preferably one that will take a 15A GPO

I assumed it would cope with one machine and a 3hp DE? A C curve should cope with a 60A transient.

Originally Posted by BobL

Please ear in mind there are Axial and Centrifugal Hydroponic fans - make sure try looking at the latter.
The Hydro centrifugal fan ratings will be closer to actuality than the axial type.

So, it looks like that's going to be $400 ish.
Fan Centrifugal Can Fan RS 315mm - Gold Coast Hydroponics
CAN FAN 250mm RK250 Centrifical inline fan low noise 225lps

My means of exiting the workshop are limited. Is a 6" duct large enough for fans of this kind?

Originally Posted by Stopblock

I assumed it would cope with one machine and a 3hp DE? A C curve should cope with a 60A transient.

3HP DCs usually run from 15A GPOs which are usually on their own circuit and breaker
The other machine lathe etc can run on the existing 20A circuit.

Usually set up is
- one 10A circuit for lighting,
- one 10A circuit (10A outlets on a standard 16 or 20A RCD Breaker),
- 15A circuits are (15A outlets on 20 or 25A Breaker) specific to each machine
OR
Use standard breakers PLUS running power outlets via a 32A RCD breaker.

So, it looks like that's going to be $400 ish.
Fan Centrifugal Can Fan RS 315mm - Gold Coast Hydroponics
CAN FAN 250mm RK250 Centrifical inline fan low noise 225lps

If you plan on getting a 3HP DC, for a single car garage you probably will not need an exhaust fan.
Instead I'd put the fan money towards the DC and 6" ducting - then add an additional exhaust fan if required.
If its a 2HP then I would recommend a fan.

My means of exiting the workshop are limited. Is a 6" duct large enough for fans of this kind?

Not really, they don't like much "back pressure" but together with a 3HP DC, a 6" fan may be enough?

Correction for part 1 - centrifugal fans

Part 2: Dust Extractors

The three key figures for dust extractors are (per Bill Pentz):
* 1000 CFM - the miniumum volume of air to be moved (in cubic feet per minute) in order to catch dust when it is created and before spreading to the room
* 6" - the minimum size of ducting to have any chance of meeting the 1000CFM requirement
* 4000 FPS - the minimum speed at which the dust needs to be moved to prevent it precipitating out and clogging the ducts. For 6" ducts, 4000 FPS translates to roughly 800 CFM.

If the CFM of the DE is sufficiently high (ie about 650CFM for 55m3 room) (and is exhausted outside) then it will perform sufficient air exchanges to evacuate any dust missed as a result of the less-than-idea CFM. However, there is limited scope to compromise on volume of air moved because I pretty much need 800CFM in order to avoid clogging anyway.

Not sure whether a DE will overheat if run to act as an air exchanger.


Needle v Pleated Filter:
Pleated filter because it gives better airflow (about 10%).
Also smaller, but more expensive (~$230 DC 3, $460 for DC7).

Cyclone v No Cyclone:
Cyclones cause an effective drop of CFM
Cyclones typically only separate out chips.
Not much point in inserting a cyclone inline unless it separates out dust (CV and, apparently, Laguna CFlux/PFlux).

Table of Models
DC3/DC7 as representative of variety of 2 and 3hp models out there.

Model	Enclosure Volume (m^3)	CFM effective	Noise	Price	1 micron filtration
Hafco DC3	3.31	600	??? 90db??	$418+$230 for 1xpleated filter	None
Hafco DC7	4.73	1150	??? 90db??	$594 (+$460 w 2xpleated filters)	None
"Modified DC3"	3.31	900?	???? 90db??	$418+$230 for 1x pleated filter + elbow grease	None
Laguna Pflux series 3	3.80	1300	76 dB(A) @ 3m	$3,899	100 (HEPA filter)?
Laguna Pflux series 1	3.09	720	70 dB(A) @ 3m	$3,199.00	100 (HEPA Filter)?
Laguna Cflux	3.76	1299	88 dB(A) @ 3m	$2,949.00	99.7?
Clearvue 1800	3.53	1442	78 dB(A) @ 3m	$3,366.00 (+$1500 for 2x pleated filters +$500 for VFD)	Technically, not stated without filters but 99.999? with filters

Most sensible option seems modified DC3, although don't know how noisy it will be.

Originally Posted by Stopblock

The three key figures for dust extractors are (per Bill Pentz):
* 1000 CFM - the miniumum volume of air to be moved (in cubic feet per minute) in order to catch dust when it is created and before spreading to the room

1000 CFM is BP's general recommendation but what is required in practice depends on each machine.
This is also from BPs website
Machinerydustflowrequirements.jpg

* 6" - the minimum size of ducting to have any chance of meeting the 1000CFM requirement

More importantly its' the minimum size ducting for anything over about 450 CFM.

* 4000 FPS - the minimum speed at which the dust needs to be moved to prevent it precipitating out and clogging the ducts. For 6" ducts, 4000 FPS translates to roughly 800 CFM.

This applies more to industrial dust extraction systems where many cubes of sawdust per hour are produced, often from multiple machines at the same time . In DIY situations, rather than; "preventing dust from precipitating", the 4000 FPM applies to the case where a the air flow through a duct fulled loaded with sawdust suddenly stops and then the sawdust drops out. When the flow restarts, 4000 FPM will be needed to restart the saw dust flow and pick up the precipitated sawdust.
In practice I've not found this to be a major issue. Even as low as 2000 FPM will keep (especially fine) sawdust moving through ducting. In DIY situation, if air flow stalls the duct will rarely be full of sawdust so 2000 FPM should also be enough to pick up what has dropped out of the flow. Problem ia more significant if the sawdust is from green wood (ie stickier) making it harder to pick up again.

Not sure whether a DE will overheat if run to act as an air exchanger.

Should not be a problem

Cyclone v No Cyclone:
Cyclones cause an effective drop of CFM
Cyclones typically only separate out chips.
Not much point in inserting a cyclone inline unless it separates out dust (CV and, apparently, Laguna CFlux/PFlux).

Depends on cyclone efficiency - cyclones like the Clearvue will separate most of the fine dust. No filters are required when externally vented.
For small DCs the problem with cyclones is less about separating fine dust and more with choking the air flow so it fails to pick up enough air/fine dust in the first place.

Originally Posted by Spyro

Instead of Dylos I went the cheap chinese route, I think it was under a hundred bucks

........

Obviously if you need a Dylos then you need a Dylos...

Actually, you can get Dylos equivalent readings from that device. There's an alternate display mode that shows the raw particle counts. The Dylos shows the number of particles greater than 0.5 and 2.5 per .01 cubic foot. The 0.5 and 2.5 particles per deciliter shown on the low cost device can be converted to the Dylos units by simply multiplying by 2.8.

Is there anywhere that shows the spectra of noise from dust extractors?
What frequencies are the main culprits?