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Author Topic: Dust collection  (Read 1182 times)

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Offline dean herring

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Dust collection
« on: October 02, 2017, 09:02:44 am »
My next purchase is probably gonna be a dust collector and am leaning toward a cyclone type.
Eventually I will have a 20" or a 24" planer, jointer , table saw and lathe. Welcome any advice or experience on best to get . Thanks
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Offline Savannahdan

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Re: Dust collection
« Reply #1 on: October 02, 2017, 01:11:49 pm »
I have a regular dust collector for the shop but it's not located for best use so I use a shop vac with a Deputy Dust Genie attached to it.  I'm impressed at how much it collects and I don't waste money on dust collection bags (costly) and don't have to clean the shop vacs filter as often.  I'm eyeballing adding a cyclone to the larger system.  Oneida puts out some nice equipment, you can also get them from Grizzly, Woodcraft, Penn State Industries and a few others.  When I made my choice of collection systems many years ago the cyclone systems available wouldn't fit into the lower ceiling of my shop. Other than discharging sawdust to the outside of your shop I think a cyclone system would serve you well.
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Offline dean herring

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Re: Dust collection
« Reply #2 on: October 02, 2017, 07:32:19 pm »
Discharging sawdust outside is easily doable. Is there a system specifically for discharging outside?
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Offline woodworker9

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Re: Dust collection
« Reply #3 on: October 03, 2017, 09:46:42 am »
You can contact Oneida directly.  Their customer services is very good, and they will help you size and design a system that is right for the machines you plan on utilizing, as well as plan for future expansion, if you are so inclined.

There is tons of information regarding the short comings of some of the systems you mentioned, and I can only urge you to search the internet for this information before purchasing.  This is truly a case where trying to save money on import clones can leave you with a less than functional system that clogs a lot.

Discharging sawdust outside your shop is easily done, but you also have to account for replacement of the air you are removing.  High CFM systems need to allow for fresh air intake so you don't create a vacuum situation which pulls air out of the shop without replacing it, thus causing your blower/cyclone to work harder than it should.
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Re: Dust collection
« Reply #4 on: October 03, 2017, 09:58:24 am »
If you are just dumping it outside be careful. Sawdust can bery very dangerous. Wet sawdust can heat up enough to cause a fire. Fine sawdust floating in the air will explode with the proper ignition source.

I have been to many fires at crosman air guns. They have an outdoor hopper they dump the sawdust into using a large dust collector like you are talking about. Whenever they have a fire its an all day ordeal and usually ends up us disassembling the hopper to put the fire out. Good news is we are a volunteer department so we don't charge for it.
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Offline dean herring

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Re: Dust collection
« Reply #5 on: October 03, 2017, 08:31:08 pm »
Thanks, I think I stick with a cyclone
Don't need a fire
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Offline YellowHammer

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Re: Dust collection
« Reply #6 on: October 04, 2017, 10:00:41 am »
We have an open air system, after a few configuration changes, and now dump all our sawdust outside, decent amounts, I suppose, into a dump truck.  We fill it up every week, sometimes two, sometime sooner, and I use it in my farm, or sell it.  It's a combination of green sawmill green dust and kiln dried planer and tooling chips.  Everything that generates dust goes through the system, outside to the the dump truck.

I talked to Oneida engineers at length about some of my options and relative cost, (I ended up buying a Timberking) and they, as well as others, can be set up outside, and in many instances, from a commercial configuration, are indeed routinely set up outside, if nothing more than to reduce the inherent risk of inhalation health issues and fire of sawdust in confined spaces.  There is a risk of fire anywhere a sawdust collector is set up, and if it is used to pull from the mill, the sawdust will be damp, so having it outside or inside won't matter.  Green sawdust can heat up, dry sawdust can be very flammable if sparked, and an equally important concern is personnel exposure during container or hopper empty and cleanup, getting it into your eyes, ears and respiratory tract.  I've seen instances where a hardwood manfacturer dumps from a hopper into awaiting 18 wheelers, and it is an incredible mess.   

The blower I bought is a through flow chip blower, which can digest relatively large chunks of debris without damage, and doesn't need a sealed vacuum system.  It does not have the air flow or suction efficiency of a similar sized cyclone system.  Most cyclone blowers, on the other hand, have more efficient impellers but do not like debris going through them.  So they are semi vacuum systems where the shavings are deposited in the containers on the suction side so that relatively clean air only gets to the impeller.  The downside is that the chip and duct containers must be somwhat sealed. 

In an outside environment where the cyclone debris is dumped into an open air hopper, a special device called an airlock is installed, which is like a rotating door, which seals and dumps as it rotates.  Pretty expensive. 

The amount of chips produced is important, I used to fill bags and drums, and spent too much time emptying them.  So that is a disadvantage if a bag system if it is not big enough for your personal production of chips and dust.

Also, ductwork and electrical installation are important considerations.  I originally installed my system with plastic PVC and one winter I kept hearing a sharp popping cracking noise, like an electric fence charger arcing.  After some hurried investigation, I noticed that I was getting a substantial arc from the surface the dust collector pipe to a nearby metal building brace, the arc maybe a half an inch long :o every few minutes.  So after I ran to shut the machines down, out come the plastic ductwork, in goes the metal ductwork, in a major hurry.

We get inspected by the Fire Marshall as well as our insuranse company, on a regular basis, and they were quite eye useful and opening.  The Fire Marshall learned I used shop air and leaf blowers to clean up, and had me remove some of the outlet covers furthest downstream in the building.  They outlet boxes were packed with sawdust. :o :o

Then he looked at my flourescent tube light fixtures and had me put plastic tube protectors over every one.  Sure enough, upon installation, one of the bulbs showed signs of arcing around the bulb pins where extremely fine sawdust had bridged and the high voltage ballast had sparked and charred a path through the dust on top of the light bulb.  Yet one more !!! :o :o

So I am a true believer in fire safety and sawdust.  Here's what I finally settled on:  sawdust collected outside, a relatively safe distance from anything I care about burning down. Sawdust blown into a truck so I don't have to get exposed during cleanup because no bags or bins to empty.  A lower efficicency trash blower instead of a higher efficiency and higher cost commercial cyclone.  Metal piping.  Dust sleeves for my light bulbs.  Vacum my outlets every year.  Clean up and remove debris routinely.

A long post, maybe something useful for your consideration. 
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Offline Crusarius

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Re: Dust collection
« Reply #7 on: October 04, 2017, 10:46:39 am »
Yellowhammer does you metal piping have its own ground?

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Offline Kbeitz

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Re: Dust collection
« Reply #8 on: October 04, 2017, 01:41:55 pm »
This dust collector grounding kit is made for plastic piping...
It runs inside the pipe.

 

 
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Offline YellowHammer

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Re: Dust collection
« Reply #9 on: October 04, 2017, 02:56:39 pm »
Yellowhammer does you metal piping have its own ground?
Yes, that's a good point, and I'm a quick learner, usually.  Any system that has the potential to build up voltage in our shop now has a dedicated ground, in the form of a local 8 foot ground rod and adequate copper wire.  Our laser which is pretty expensive even has an installation requirement that any dust collector pipe run nearby must have a dedicated ground to protect it.  The metal pipe naturally grounds to the machines, metal to metal contact through the dust collector ports which is potentiall harmful to their electronics, and the dust collector motor/blower isn't totally independently grounded either, as it's also grounded to the electrical panel, but it's important to have a low resistance, local ground to bleed off the potential voltage.  We also attach a ground rod to the dust collector piping system.   

So we now have a dedicated local ground for all our electrical panels (code requirement), a dedicated ground for our dust collection system, and also an independent and dedicated ground for our lightning rods for our Lighnting Protection System (LPS).

This dust collector grounding kit is made for plastic piping...
It runs inside the pipe.

 

 (Image hidden from quote, click to view.)
Kbeitz, I've seen some of those systems, but I don't know how well they work.  After my little "lightning in the building" incident, I just decided to go with metal.

I really wish I had taken a video of the sparking and arcing for proof and posterity, but it was several years ago, and at the time, the last thing on my mind was photography.  It may be interesting to note that it was when my planer was running hard throwing lots of chips, on a cool dry day in winter time.
 
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Offline Crusarius

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Re: Dust collection
« Reply #10 on: October 04, 2017, 03:05:52 pm »
KB I have always seen that wire just run around the pipe and grounded externally.
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Offline Kbeitz

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Re: Dust collection
« Reply #11 on: October 04, 2017, 11:01:50 pm »
KB I have always seen that wire just run around the pipe and grounded externally.

It's best to run it inside to bleed off any static build up.
I don't think it would do much good outside.
It's made for inside. It's a braided copper wire.
I worked a lot with static build up in the textile industry.
I think we would have lost all of our workers if I did not
do something about all the static problems we had working
with elastic and lycra products. That static snap hurts.
Really hurts.
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Offline 21incher

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Re: Dust collection
« Reply #12 on: October 05, 2017, 07:57:16 pm »
I have the copper wire inside all my pvc pipe and hoses grounded back to the collector. Before I put it in you could get a good shock touching my aluminum router table top from the static during the winter months. I understand pvc generates so much static that the pipes can explode if the fine dust ignites. Better to be safe than sorry.  :)
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Offline dean herring

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Re: Dust collection
« Reply #13 on: October 05, 2017, 08:32:43 pm »
Thanks Yellowhammer, which one did you get from timberking?
It would match my sawmill.
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Offline low_48

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Re: Dust collection
« Reply #14 on: October 05, 2017, 10:20:43 pm »
Mythbusters spent a great amount of time trying to get a spark from dust moving through a plastic pipe. They never did. You are much more likely to get a spark from a machine than a static spark. Also, I can't imagine the ignition source you would need to light off dust blowing at the flow rate coming from a blower. It takes such a precision mixture of suspended fine dust, oxygen, and spark. It would take great effort to achieve that combination when the dust is moving at 20mph (just a guess at the speed). I woodwork all year long. No way do I want to pull heated or air conditioned air and blow it outside. Stick with the cyclone, but don't be bashful about using PVC. Pay attention to duct size, and use a 6" trunk line with that size of planer.

Offline YellowHammer

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Re: Dust collection
« Reply #15 on: October 06, 2017, 01:04:06 am »
I bought the five horsepower Timberking blower only, I didn't get the bags and piping.  I run it from 2 to 8 or more hours a day, pretty much 6 days a week.  I mounted it outside under an awning to keep the noise down.  I use it for my mill as well as all my shop equipment, using aluminum blast gates to shut off airflow to tools I'm not using.  It has no problem filling up my dump truck.

Mythbuster missed the effect I experienced if they were trying to spark inside the pipe with moving fuel/air. I didn't see the show, but that was not what happened in my situation. I had an external spark from the PVC to metal covered in flammable sawdust.  Mine is much more predictable, explainable and repeatable.
 
Triboelecric effect is caused by high speed particles moving against an insulating surface, in my case a non carbon loaded PVC pipe.  Also, as I mentioned, the low winter air temperature and low humidity are conducive for the buildup of static electricity.  As the friction occurs due to dust particles traveling down the pipe, a static charge is built up in the insulator.  If enough static charge is built up and if a nearby ground is present it may eventually build up enough energy to cause a dielectric breakdown and arc through the air.  Typically, the longer the arc, the hotter it will be.  So my spark did not occur inside the pipe, as apparently Mythbusters tried, it arced externally between the PVC and a metal building rafter about a half an inch away.  On top of the rafter was years of fine, dry sawdust particles that could have easily caught fire and propagated to the wooden roof.  All it takes is a spark.  Thankfully it did not, and I got lucky.  I heard the spark repeatedly, over the course of a short period of time, and isolated it by actually hearing and watching it snap an arc through the air over the background noise of the planer.  It sounded and looked like any standard cattle rated electric fence charger arc. Once I figured out what was happening, I shut things down. 

This is a different scenario than having a dielectric breakdown to dust particles flowing inside the pipe.  Unless the fuel and air ratio was greater than the Lower Explosive Limit nothing would happen.  A spark might occur but it would not propagate.  Of course if the air and fuel mixture was correct, and the dust particles were of proper size, the smaller the better, as the surface area ratio goes up, then certainly combustion could occur. I have no personal experience with that particular phenomenon with sawdust, but I do have first hand, no doubt experience of an electric arc repatedly jumping in air to my dust covered metal building from my PVC dust collector pipe.  Did it cause a fire? Nope.  Could it? Yes.  It wouldn't have exploded, it, would have just caught fire.....   

This most likely would not have occurred in the high humidity of the summer time.  Also, my planer was working hard and we were generating a lot of chips.  I did not see the arcing when I was using other tools in the shop which weren't generating as much. 

As I said, I wished I had video of the situation, but I do not, however, the physics behind the triboelecteic buildup of a static charge in an insulator, the possibility of an external spark, and potential ignition of a suitable fuel source is readily explainable.


I'm not saying don't use PVC, or change out what you have if you don't want to.  All I'm saying is be aware.





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Re: Dust collection
« Reply #16 on: October 06, 2017, 01:29:46 am »
General consensus seems to be that the static discharge from a small scale (home workshop) size dust collector can't generate enough charge to ignite dust. Enough to give you a fright and a visible discharge? Yes it certainly can, especially in a dry enough climate.

But I imagine that as things get scaled up, the potential would increase as the "storage" potential of the pipe system would increase. The spark would release more energy, and eventually get to the point where it could ignite something.

Hence when you get up to things the size of aircraft, which also tend to pick up a static charge, and then sit on nice insulating rubber wheels, it becomes an actual safety hazard. Lightning is also basically the same phenomena, where you have millions of ice crystals moving, and a whole cloud to build up the charge in. BIG Volts, and Amps involved there.
 
Out of interest, to arc across a 1/2" gap would need about 36,000 volts, but the current would be relatively small unless it was a huge system.

What an earth cable running on or around the duct does is reduce that gap to practically nothing, allowing the static charge to drain away to ground before it gets to levels where you notice.
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Offline dean herring

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Re: Dust collection
« Reply #17 on: October 06, 2017, 06:44:09 am »
Yellowhammer so you can buy just the blower?
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Offline Crusarius

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Re: Dust collection
« Reply #18 on: October 06, 2017, 07:51:32 am »
I would be more concerned about wet sawdust building up heat and causing a fire that way. Especially if you fill the bags and leave them sit for a while.
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Re: Dust collection
« Reply #19 on: October 06, 2017, 12:13:24 pm »
Yes, you can just buy the blower from them.  They offer a 5hp and a 3 hp unit.  YH has the 5 and I have the 3.  I am in the process of building a cyclone for my woodshop using the Timerking/Woodmaster blower with the Oneida Super Dust Deputy Cyclone Separator.  I have bought all the parts needs, now I need to buy the time needed to put it all together.  These blowers are HEAVY DUTY.  If I could just blow outside I would, but my shop location doesn't permit that.