More on dust extraction

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Pat.Hawkins
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More on dust extraction

Post by Pat.Hawkins » Fri Aug 31, 2018 10:44 am

Hi Folks,
I see Joseph's drum sander post was morphing into a dust control topic. It raised a few questions with me as I'll be setting up a new shop soon and the extractor is my first consideration. I guess I'll have a single duct with multiple shut-offs using one machine at a time.

The Carbatec and Jet 2HP are both speced similarly - is it just the build quality that causes the price difference?
Are pleated filters made for these models?
Can you maintain a pleated filter's life indefinitely?
Cheers

Cal
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Re: More on dust extraction

Post by Cal » Fri Aug 31, 2018 3:16 pm

Hi Pat,
Probably the first thing to consider in installing a dust extractor is where it will be located, inside a shed is not an ideal location as you will be breathing in all the dust that the extractor is unable to contain. I have mine located outside the shed in its own shed and the duct runs through the wall into the shed and to the various machines. We need to start with the actual ability of the extractor to remove the fine dust at the source, to do this we need to look at the real statistics of the dust extractor not what the manufacturers put in their specs or what the salesperson says because they are both wrong (through real world testing). The minimum cfm (cubic feet per minute) draw that is required to keep us safe and healthy is 1200cfm, most manufacturers claim that a 2hp dusty draws this and it is based on the speed of the impeller with nothing attached to the extractor before or after the impeller. This means no machine hooked up to it and no ducting either, nor are there dust bags or filters. A 2hp dust extractor can only draw a max of 900cfm once everything is hooked up, it is not enough. 3hp single phase with two bags and filters is the minimum that will draw 1200cfm, this also depends on the size of ducting you intend to run. 1200cfm can only be achieved with 150mm ducting, 100mm ducting will only draw 400cfm. Machine ports are a standard 100mm which also need to be addressed as they too will only allow a total of 400cfm to be drawn even if you directly attach a 150mm duct to the 100mm port. As for filters, weather they are pleated cartridge or needle felt filters, they both only allow sub 3 micron dust particles to escape, but these particles will still do damage to your lungs, that is why the dust extractor needs to be either in its own shed or fully enclosed in the shed and vented to the outside away from doors and windows in the shed. Pleated filters take longer to clog up than needle felt filters as they have more surface area, so the time between cleans is longer but they still need to be cleaned to maintain the maximum cfm of the extractor. I have needle felt filters and my extractor is in its own shed. The length of ducting needs to be kept as short as possible and the type of ducting is also important, flexible ducting should be kept as short as possible. Use long sweeping pvc bends to keep flow high and bell mouth hoods on the machines for smooth flow into the ducting. Blast gates should also have a smooth surface transitions inside them and not reduce smaller than the internal diameter of the ducting being used. This information is not just a combination of assumptions on my part, this is from others on the woodwork forum who have used partial counters and other electronic devices to test what really works and what fails. In Australia, authorities have designated all timber as being carcinogenic.
I will post some pics of my shed so you can see how it works. Or here is a link to what I have done http://www.woodworkforums.com/f200/lets ... -do-214143

Cal
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Re: More on dust extraction

Post by Cal » Fri Aug 31, 2018 5:36 pm

ok, here are some images of my setup, in no particular order. the only machine I don't have with 150mm ducting is the bandsaw, its not exactly mine so I am not going to cut it open to the 150mm duct size. since I took these pictures I have added a large bell mouth hood the the belt sander.
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shed 2.jpg
shed 1.jpg
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kiwigeo
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Re: More on dust extraction

Post by kiwigeo » Fri Aug 31, 2018 6:13 pm

So THAT'S why the air is always fresher in Strahalbyn? :mrgreen:
Martin

Cal
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Re: More on dust extraction

Post by Cal » Fri Aug 31, 2018 7:59 pm

kiwigeo wrote:
Fri Aug 31, 2018 6:13 pm
So THAT'S why the air is always fresher in Strahalbyn? :mrgreen:
Yep there is that and I am doing my part to keep the town in a constant vacuum, just the way the old towns folk like it :lol:

Pat.Hawkins
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Re: More on dust extraction

Post by Pat.Hawkins » Sun Sep 02, 2018 9:59 am

Wow - That's a reply!

Guess I've got some more homework to do like considering dropping a non-essential or two (like the bobbin sander) and get the extraction right.

Thanks.

Cal
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Re: More on dust extraction

Post by Cal » Sun Sep 02, 2018 11:30 am

Sorry if it’s too much information, I’m not sure as to what you’re plans are or the amount of information you have on the subject. What I have written only touches the surface of a safe environment and dust, I really started to take notice after I turned and finished a bowl from redgum. I had a headache for days afterwards, and was really effected by the sanding dust. That is where my journey started, it is very easy to become sensitised by any timber or finish you work with. I would really encourage you or anyone to have a good read of the information provided on dust extraction in the woodworkforum.com, it is invaluable. It has probably set me back around $2000 to set mine up, a lot of the expense is in the PVC ducts and bends, I could have bought a good tablesaw for that.
Cheers Cal

Gazm
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Re: More on dust extraction

Post by Gazm » Sun Sep 02, 2018 11:56 am

Food for thought Pat...Bill Pentz.com , some say fanatical but, how much is your life worth??
I'm setting up my extraction system with a 4hp motor & 150mm spiral metal ducting with fittings.
Bill site is a lot too wade thru, but a great guide line.

I applaud your Extraction ideals Cal, great job!!! :cl :cl :cl :cl

Gaz

Joseph Jones
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Re: More on dust extraction

Post by Joseph Jones » Sun Sep 02, 2018 3:52 pm

Like the blast gates.

Joseph.

Cal
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Re: More on dust extraction

Post by Cal » Sun Sep 02, 2018 5:58 pm

Gazm wrote:
Sun Sep 02, 2018 11:56 am
Food for thought Pat...Bill Pentz.com , some say fanatical but, how much is your life worth??
I'm setting up my extraction system with a 4hp motor & 150mm spiral metal ducting with fittings.
Bill site is a lot too wade thru, but a great guide line.

I applaud your Extraction ideals Cal, great job!!! :cl :cl :cl :cl

Gaz
The only thing with spiral metal ducting is that it is not smooth internally like PVC, it will create turbulence especially around the bends and reduce the efficiency even with a 4hp extractor. I think the radius on the bends are tighter as well which reduces flow. It will be more expensive than PVC also. Bill Pentz is an amazing man, his clear view cyclone is the best on the market. Be aware that Bill is using larger ducting ( I think it’s 7”) than we have here in Aus and his extractor is set up accordingly.

Thanks Joseph, the straight ones are an adaptation of others I have seen and the rocker style was designed by BobL from the other forum, he has a template in one of the threads. As were the bell mouth hoods, I made a wooden former on the lathe and sat the PVC on it then used a heat gun and a blow heater to soften the PVC enough to create the shape while tightening the tailstock on the lathe.
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Joseph Jones
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Re: More on dust extraction

Post by Joseph Jones » Wed Nov 14, 2018 9:24 pm

What about copper wires earthing the pipes to stop static electricity and sparking, are they still necessary this day and age?

Joseph

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kiwigeo
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Re: More on dust extraction

Post by kiwigeo » Wed Nov 14, 2018 9:39 pm

There seem to be widely varying opinions and advice on this one. Discussed at length here: http://lumberjocks.com/topics/14140
Joseph Jones wrote:
Wed Nov 14, 2018 9:24 pm
What about copper wires earthing the pipes to stop static electricity and sparking, are they still necessary this day and age?

Joseph
Martin

Cal
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Re: More on dust extraction

Post by Cal » Thu Nov 15, 2018 6:36 pm

The static electricity issue causing sparks and subsequent fires has been debunked many times, static charge can be felt on the outside of the ducting sometimes, I have a bit of copper wire around one length of flex duct that is grounded to the shed that I brush up against regularly, only because the static charge makes it’s way over my whole body including my eye glasses and I end up with bits of dust clinging to the glasses. The static charge does not travel internally through the duct, not only that but the dust particles don’t touch the sides of the duct all the way through to the extractor either. Just don’t send metal sparks through to the extractor!

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kiwigeo
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Re: More on dust extraction

Post by kiwigeo » Thu Nov 15, 2018 6:43 pm

Cal wrote:
Thu Nov 15, 2018 6:36 pm
The static electricity issue causing sparks and subsequent fires has been debunked many times, static charge can be felt on the outside of the ducting sometimes, I have a bit of copper wire around one length of flex duct that is grounded to the shed that I brush up against regularly, only because the static charge makes it’s way over my whole body including my eye glasses and I end up with bits of dust clinging to the glasses. The static charge does not travel internally through the duct, not only that but the dust particles don’t touch the sides of the duct all the way through to the extractor either. Just don’t send metal sparks through to the extractor!
That's pretty much my understanding after trawling through screeds of discussions on the subject. You might get a zap off your PVC ducting but cases of PVC ducting on small scale extraction systems setting fire to workshops just don't seem to exist.
Martin

Cal
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Re: More on dust extraction

Post by Cal » Thu Nov 15, 2018 6:54 pm

Yep, the bit of flex I have it attached to only gets static charge if I have it hooked up to my makeshift drum sanding attachment that is on my big belt sander, when I use that same bit of flex on my tablesaw or router table I don’t get any charge off it. I think it has to do with the speed of rotation of the sander more than anything and the fact that the belt is brushing against the backing plate as it whizzes around. Strange though that I don’t get any charge from the bell mouth hood or duct that I use with the sander normally, the hood is aluminium and it sits on the motor housing of the sander, maybe it’s that grounding it? Who knows.

blackalex1952
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Re: More on dust extraction

Post by blackalex1952 » Fri Nov 16, 2018 11:41 am

I don't worry about the static myself, I might be a reasonable musician....but I'm a poor conductor!-Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

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lamanoditrento
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Re: More on dust extraction

Post by lamanoditrento » Tue Nov 20, 2018 9:37 am

blackalex1952 wrote:
Fri Nov 16, 2018 11:41 am
I don't worry about the static myself, I might be a reasonable musician....but I'm a poor conductor!-Ross
Ross for the win :lol: :lol: :lol:
Trent

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