Grounding my Dust Collection System

[Bru]

I am running a HF 2hp dust collector, from my table saw, using 3 inch ABS black plastic pipe. The motor on the DC is grounded ( 3 prong plug). Do I need to ground the pipe or anything else? Hope this isn't to dumb of question...I've read enough to know that...I really don't know or understand the grounding concept. The motor, blower and dust bag sit on a metal platform on rubber wheels. I'm worried I don't want to blow up my Festool tools.
My second question; on my CT22 I am running a 5 gallon bucket cyclone system, do I need to do anything to ground that system? (see pic) Is there anything to worry about the way I have both set up?
Thanks for all your help! Bru

 

[Scott W.]

Bru
While this subject always seems to "spark" a debate, I will give you my opinion based on my shop.

I have a 7.5hp dust collector with a bag house type filter system. while the main ducting is all metal, I did use plastic pipe for some of the branches and plastic flex for some of the machine hook Up..

When I first installed it I did not add any grounding to the plastic (or from the machine past the plastic back to the metal duct).

After a while I noticed that fine dust was sticking to the plastic which made me a little nervous. I added some copper wire between the machine along the plastic and attached it to the metal duct.

No more dust - no more static.

On the other hand I know several folks who just use plastic, no grounding what so ever.

I think that the chances of a dust explosion from static in a small system like yours is very unlikely. However, I don't know what your environment is like, what kind of dust you are producing or your tolerance for risk.

If it were me, I would run a ground from the metal of the saw along the plastic and to the metal of the collector.

It's cheap and easy to do.

Just one opinion 

Scott

 

[Bru]

Thanks Scott, should I rap a bare copper wire from my TS around the pipe, maybe ground to my metal building? Thanks again for the reply.

 

[Scott W.]

Thanks Scott, should I rap a bare copper wire from my TS around the pipe, maybe ground to my metal building? Thanks again for the reply.

I doubt that grounding to the building will make any difference. If your DC has a grounded plug then that should "complete" the ground.

If you have an ohm meter check to see if the ground of the plug has continuity to the metal of the DC, I'll bet it does.

I used bare "woven" copper wire, I don't recall where I got it but this is a kit from Grizzly that should work just the same:http://www.grizzly.com/products/G4679

Scott

Scott

 

[Bru]

Thanks again Scott, I will do that.

 

[Greg_R]

There has never been a documented case of a wood dust explosion (fire yes, explosion no).  Even in large plants, OSHA classifies wood dust as a fire hazard (vs an explosion hazard).  Flour dust (which is very fine and very dense) is very prone to explosion and that's where a lot of the wood dust explosion worries come from.  The ABS pipe _will_ build up some charge and zap you.  If this is an issue, ground the pipe.  An easy way to do this is to use the metallic HVAC tape and run a strip down each pipe and ground the strips every so often.

 

[bruegf]

I've been kicking around the idea of using a ground path created from a fairly narrow copper foil tape applied to the plastic tubing as a way to create an inexpensive boom arm.

Fred
http://cgi.ebay.com/6mm-Multi-Purpo...goryZ131QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[Bru]

Thanks Greg, just got in from the shop of course playing with the DC system. Thanks for the info...Bru

 

[Dave Ronyak]

Fine Woodworking Magazine did a feature article about dust collection systems in the past year or two.  They also debunked the rumors about danger of a wood dust explosion in typical 1 - 3 Hp DC systems. 

Running a grounding wire or tape or strip all the way from the saw to the vacuum or to true ground will certainly dissipate the static that might otherwise buildup in the plastic components that are not electrically conductive.  But I would first try simply bridging the the plastic components with the wire or conductive tape.  The amount of electricity to be handled is not like that required to run any of your machines.  You can try grounding to the wire in the clear hose and jumpering across the plastic lid to the Festool AS hose.  Commercial static dissipating systems and packaging use materials of controlled electrical conductivity - just enough to dissipate any electrical charge that would otherwise buildup.  I am using a Oneida Dust Deputy (made of ?powder coated? steel with a flexible adapter fitting on its inlet connected to a Festool AS hose, and a common rubber plumbing adapter on the inlet fitted to another Festool AS hose and have not experienced any noticeable buildup on those components.  I have noticed "dust flocking" on other parts of my CT 22 when I run it for a considerable period of time, though, especially on the fittings that secure the Boom Arm and Handle and the Wheels of the vacuum machine.  Even so, I have not felt any static discharge when I walk over and turn the vacumm machine to "manual on" to sweep up the dust that was not directly captured.  (I made a lot of uncaptured dust the other evening while routing rabbets on the perimeter of a large door panel and its frame.)

You might also try jumpering the plastic components by using common hose clamps  on the hose end that grip either your wire.  I think braided grounding wire might be more user friendly and help avoid injury from sharp ends of a solid single conductor wire.

Dave R. 

 

[Bru]

Thanks Dave I just added the braided ground wire to my List. Should pick it up tonight and install it tomarrow. Have to get some more ABS to complete the other side of my shop. Thanks again for all the help. Bru

 

[jonny round boy]

There has never been a documented case of a wood dust explosion (fire yes, explosion no).

Also, that depends on your definition of 'explosion' - wood (and flour) dust is a low explosive, as opposed to a high explosive. It can and does explode, but not in an 'action movie' kind of way.

A high explosion is where the flame path accelerates faster than the speed of sound, creating a sound pressure wave (the bang).

A low explosion is where the flame path accelerates slower than the speed of sound (but can still be very fast), resulting in more of a 'wooshing' sound rather than a bang (or, as my Physics teacher used to say "it's the difference between a woof and a bang").

Even a low explosion can be very dangerous, and though it is rare, it is possible. One of the largest dangers is that airbourne dust could combust, resulting in a low explosion which dislodges a larger quantity of settled dust within the workshop & makes it airbourne, creating a secondary explosion.

The HSE (Health & Safety Executive) in the UK also states that some wood dusts can spontaneously combust when they come into contact with certain oils and chemicals.

The chances are it's HIGHLY UNLIKELY to happen, but it can and sometimes does. Unlikely does not equal impossible.

 

[Tinker]

I lived for six years on a farm in southern Berkshires.  i have been involved in various forms of agriculture,along with construction, ever since.  During my years as a pre and early teenager(that's when i lived on a farm). and later working on farms thru my HS and on into college years, i was witness to many barns burning to the ground. I was a voluteer fireman for 27 years. In later years, even up til present time, i have been winess to, first, second or third hand, of structures burning, sometimes total losses.

In the cases of the earlier barn burnings, there were 3 main causes that could almost always be attributed to their distruction by fire.  The most common that those outside of the farming community most often attribute has been lightening.  those within the farming community most often think right away of spontaneous combustion from wet hay.  The third, altho just as dangerous, if not as often stated as a cause has been oily rags.

Since working around construction, some of the other causes i have come across as everyday hazzards have been oily rags piled in corners or buckets.  sawdust from floor sanding before the finishing material has completely dried.  The finish material mixes with the encapsulled sawdust (sanding dust) and eventually heats up to flash point when it explodes.  Wet sawdust from saw and planing stations if alowed to become wet and left in a pile can heat up to explode in spontanious combustion.  A spark in an enclosed dusty room can cause the dust to explode. (JRB has explained the various levels of explosion). 

These are some of the causes not included in the above conversations that are just a dangerous.  Anybody who works around farms, construction, storage facilities, workshops of almost any kind of situation where there is dust, oil and/or machinery is always exposed to the potentials of spontaneous combustion from various causes and should be constantly on the lookout for the potential dangers.  Even with constant vigilance, there is ALWAYS the potential for the tiniest accident from lack of 100% attention to cause the 100% loss of property, and sometimes even lives.

I, as Chris alluded, cringed when a respondent stated that explosions from static and wood dust never occurs.  Been there, seen that.  doesn't matter where high noon or midnite, conditions come together in just the wrong way and there will be excitement, i assure you.
Tinker

 

[Fred West]

Thank you to Rick, JRB and Tinker. Like Greg and Dave I too somewhat dismissed the idea of a wood dust particulate explosion in my shop mostly based upon the FWW article and others. I have been extremely diligent about oily rags but now will at least pay more attention to the dust situation. Would not want to "tinker" with the wrong thing. ;D : Fred

 

[Tinker]

Thank you to Rick, JRB and Tinker. Like Greg and Dave I too somewhat dismissed the idea of a wood dust particulate explosion in my shop mostly based upon the FWW article and others. I have been extremely diligent about oily rags but now will at least pay more attention to the dust situation. Would not want to "tinker" with the wrong thing. ;D : Fred

This is getting me off topic (one more time)
In another discussion, i noted that the Irish do not particularly care for Tinkers whether tinkering or not. 

Are you old enough to remember the famous Chicago Cubs combo.  if you played on the oter team, and hit a ball down the middle to Tinker, you did not ever believe he would not get the ball to Evers in time that he would not only get the guy sliding into second, but the hitter would also be retired as Chance would collect Evers throw in time for the hitter to lose his only chance.  (How terrible can i get here.) The famous call was Tinker to Evers to Chance as another double play got the Cubs out of another jamb.

I'll quit for now. 

Tinker

 

[Fred West]

Tinker, I am going to be 52 in six days but unless I was double that I would not have experienced it.  ;D Now, as to remembering it, absolutely. : My Dad. who is probably closer to your age at 80 ;D quoted that all of the time. Fred

 

[Forrest Anderson]

UK Government Health and Safety Executive has published an information sheet athttp://www.hse.gov.uk/pubns/wis32.pdf entitled "Safe collection of woodwaste: Prevention of fire and explosion".

One paragraph of this document reads as follows:

-----------
The explosibility of woodwaste

Assume that all woodwaste is potentially explosive,
unless a dust explosion test demonstrates it is not.
Woodwaste usually has a dust explosion risk where the
mean particle size is less than 200 microns and where
as little as 10% of the mixture contains dust less than 80
microns in size. Only weak explosions are likely where
the mean particle size exceeds 200 microns.
Woodwaste is commonly produced by:

- fine cutting (eg sanding) which produces a dust of
very fine particle size. This is usually assumed to
be explosible;

- machining and sawing softwoods which produces
chips, shavings and coarse dust with only a small
amount of fine dust. This does not normally create
an explosion risk, so long as the fine dust is not
allowed to separate and accumulate within
confined spaces;

- sawing and machining hardwoods which often
produces woodwaste containing considerably more
dust than that from softwood. Assume this is
explosible ;

- the processing of MDF, chipboard and similar
boards by machining and sawing. This can be
expected to produce waste containing much fine
dust. Assume this is explosible.

When mixed processing of a variety of woods and boards
occurs, assume that the waste produced is explosible.
----------------

A second leaflet, titled "Wood dust: hazards and precautions HSE information" is athttp://www.hse.gov.uk/pubns/wis1.pdf and one paragraph reads:

--------------
Each year premises and plant are severely damaged or
destroyed by wood dust fires and explosions.

Concentrations of small dust particles in the air can form
a mixture that will explode if ignited. Such concentrations
usually occur in dust extraction equipment which can be
destroyed unless special precautions are taken. Such an
explosion can also dislodge dust deposits that may have
accumulated on walls, floors and ledges which in turn
can ignite causing a secondary explosion.
--------------

Although aimed at industrial premises, it may be interesting to some FOG members. More leaflets relevant to woodworking are available athttp://www.hse.gov.uk/pubns/woodindx.htm

Forrest

 

[Steveo48]

I'm in trouble now!  I'll occasionally have an onery student clean behind the lathes with a large, portable dust collector. :

SHOCKING! 

 

[Greg_R]

and there are many cases of explosions in industrial situations.

Please show me 1 documented case of wood dust exploding from a _static_ spark in a dust collection system.  I'm not trying to be argumentative... it's just that every dust explosion that I've read about has been attributed to faulty wiring or some other form of open flame / heat source (crumpled oily rags, burning wood particulate, etc.).  Weyerhaeuser's Material safety data sheet lists static discharge as a non-issue.

 

[Bru]

Greg I've always been known for being first. So the $20, and the extra 15 minutes to install the wire really don't bother me. I don't stick my fingers by a moving blade, $20 seems like really cheap insurance to me. Just my version of shop safety, sorry I started an argument. Bru

 

[Tinker]

I stated above how some different types of materials can become explosive thru the process of spontaneous combustion.  during my later years in the construction (Mason contractor) biz, my son was becoming more and more interrested in what i was doing.  He went to work with me every chance he got.  for some kids, grounding from social events was a great deterrent against misbehavior.  for my son, to be kept home from work, and especially to be kept away from equipment, primarilly the backhoes, was the greatest deterrent immaginable.

he never grumbled or complained any time i gave him a more difficult task.  He did not complain whenever i tore appart his work and made him do it over until it was right.  What he did present mild discomfort over were my constant harangues about certain fire hazzards.  i did not allow oily rags to be tossed into piles, either alone or in same pile as other rags.  He would not verbally complain other than muttering under his breath.  Sawdust was not to be left in a pile or a container it there was a chance for it to become wet. (Most chainsaw dust it already wet).  Hay bales, if wet, were never to be taken into the shed.  So on and so on and...  He always left the impression that he thought i was crazy or somewhat unreasonable.  he never said it, but you know how a teenager can get his point across without words.

Fast forward:  we are now into landscaping.  i had retired from masonry and gone into landscaping for mostly two reasons. 

#1: My back was finally giving out and i had to lighten my load.
#2: My son had a whole bunch of buddies who wanted jobs.  there was no way i could chance putting them 30 feet in the air on scaffolds.  there was no way i could get away (or cared to risk) with having those kids rassling 85 pound cement blocks or even heavier stones.  And so on with the list. 

i knew which kids were potentials for learning and hard work long before they even thought of work.  I ultimately jumped on all of them, no exceptions, about the same fire hazzrds as I had yelled at my son for since he was old enough to walk (well, almost that long.  His version would be more like "forever")  The results were about the same as with my son.  They all thought (without saying directly to me) that I was not only a Scrooge, but i was more than crazy.

We were doing a job along a road where a new house was being built.  For most of the summer, we went past the house nearly every week, sometimes more often.  All of the kids knew the owners, who were doing much of the work themselves, and so took more than a passing interrest in the progress.  The house, by the end of the summer was completed outside, and, from my own experience, was probably nearly complete inside.  At this point, my son and his best buddy (also part of my crew) reported the owners would be moving in to the house within the next week.  that was on a Friday.

Saturday morning, the house was gone.

My son (he was now in his own house) and his buddy made a special trip to see me on saturday morning with the news paper fire report.  they wanted to be the first to show me.

It seems the owners had been putting the final finish on their floors.  They were hoping to start moving furnture into the house by Sunday.  They had applied the second coat of finish the afternoon before and had sanded, in prep for final finish coat, the following day.  The sanding dust had been dumped into several 5 gal buckets and left on the front porch.  the owners went home with plans to return next day for final buffing.  By 11 pm, they were called to witness the final colapse of their yearlong project as it burned to the ground. 

The cause:  My son and his pal were not happy to know of their friends loss, but they were finally much relieved to have finally discovered that I had not been totally off my rocker for all of those years.  They were "happy" to inform me that the sanding dust from the probably not completely cured floors had heated up in the pails and had exploded with spontaneous combustion.  I told them to not be so happy to know I was not crazy, as i probably was, am and always would be, but to remember what had happened. That was important.
Tinker