DC ducts - 4" or 6"

Greg G. wrote:

> But no matter how bad 1/2 (sometimes 3/4) of a two car garage seems,
> I could be in Silvan's shoes. That gets me all excited again.

Have you seen this shop? <g>
http://plamann.com/sys-tmpl/scrapbook/

-- Mark

Mark Jerde said:

>Greg G. wrote:
>
>> Now don't get me started on left tilt vs. right tilt. <g>
>
>Both! One of each! Two of each! <g> Three saws that tilt both ways! <g>

If I only had the room! I'm still trying to figure out where to put
this new 14" bandsaw, and the DIY router table that will replace the
plate I'm pulling out of the table saw extension.

But no matter how bad 1/2 (sometimes 3/4) of a two car garage seems,
I could be in Silvan's shoes. That gets me all excited again.


Greg G.

"George E. Cawthon" <[email protected]> wrote in message .
> Been reading this newsgroup for a long time, but
> selectively. Don't remember Grandma's face. Cheers.


Well, a long, long time ago, back when Israel owned the Sinai Peninsula and
Egypt wanted it back, an old granny was flying peace keeping missions in A4s
along the Delta line when she switched to pure oxygen. Nowadays, aging
pilots just don't wear makeup, hairspray or greasy lipstick when using pure
oxygen, face-fires ain't a pretty sight.

5" would be a real pain..

would have to find pipe.. no s&d.. prolly some metal somewhere

then i either have to make all new ports.. or do 5" to 4"
conversions..

5" really does not seem practical.

if 6" is going to be a velocity issue.. then i will go w/ 4"

the ts, jointer, planer, and bs are all w/i 12' of the DC to the
north-east

the scms is about 12' also.. but due north

the dp is about 20' due north

it's looking like i have collection needs in the lower left and upper
left quadrants of the shop.. and no needs in either right quadrant

the DC sits in the lower left of the 18w x 23h shop

how come none of the trade mags talk about 6" ducting?

Greg G. wrote:
>Probably didn't get any this weekend... <g>

Maybe you can deflate your blow-up doll and send it to me.

Be sure to send along the grounding wire.

UA100

I know we asked the question at the end of last year "does anyone have
first hand experience with a wood dust explosion" and the answer was "NO".
So maybe it's that time of year to ask it again. Cheers, JG

"Mortimer Schnerd, RN" wrote:

> Unisaw A100 wrote:
> > Greg G. wrote:
> >> Metal ducting is probably more widely available at 5" and requires no
> >> grounding wires.
> >
> > Why would you need to ground the pipe?
>
> Dust can be explosive.
>
> --
> Mortimer Schnerd, RN
>
> [email protected]
> http://www.mortimerschnerd.com

Good grief! Almost any fine organic (and some metal) powder
can be explosive (or maybe just burn fast, depending on your
definition of explosion). No one needs to prove it, it's
been demonstrated time after time in class rooms, at safety
shows, on television, etc.

However, the stuff that ends up in my nose when sawing wood,
is, I think, way to coarse to explode. It has to so fine
that it almost will not settle but just stays in the air. I
can't imagine anyone working in such conditions. And he/she
would need to worry much more about their lungs and eyes.

I have no idea if wood dust has ever caused an explosion in
a wood shop, but fine dust can be explosive.

Unisaw A100 wrote:
>
> Mortimer Schnerd, RN wrote:
> >Dust can be explosive.
>
> Prove it.
>
> UA100

Been reading this newsgroup for a long time, but
selectively. Don't remember Grandma's face. Cheers.



Unisaw A100 wrote:
>
> George E. Cawthon wrote:
> >I have no idea if wood dust has ever caused an explosion in
> >a wood shop, but fine dust can be explosive.
>
> A'yup. And my Grandma's face burst into flames when she was
> flying jets over the Sinai.
>
> Sorry, you'da had to been here for more than the last week
> to be getting that one George.
>
> UA100

Somewhere I remember there was a question about the size of ducts. I
too just bought a DC (Delta 1.5hp) and am trying how to layout my
ducts.

Dust explosions and health hazards from dust are a concern, but I'm more
interested in getting the chips from my RAS, planer and BS. I'd like to
hear more about elbows, flex tube, separators, blast gates and all the
rest of the stuff that makes up a good system.

Thanks in advance for input along these lines.

Dave in Dayton

Greg G. wrote:
>OK - My last words on the subject.

Wait! Is it? Call me a skeptic but it seems I read this
somewhere else.

http://www.pburgea.org/_Articles/01-02/A06/PHS%20Wood%20Shop%20Fire.htm
http://www.talkshopbot.com/messages/26/801.html
http://www.sharon-herald.com/localnews/recentnews/0010/ln102000c.html
http://www.warren-group.com/articles/grainpartI.html
http://www.ccbfc.org/ccbfc/committees/former_SC/hazardous/minutes/minutes_9402_E.shtml

And in which of these was PVC cited as the culprit?

>As far as I'm concerned, $3 is cheap insurance against these sorts of
>things - in addition to the reduction in unpleasant static discharge
>to your person.

Agreed when you cite static discharge.

>Ciao,

Probably not given your track record to date.

UA100

In article <[email protected]>, dcopeland2
@woh.rr.com says...
> For all you disbelievers that dust cant explode I've had the unfotunate

A) Nobody is disputing the fact that dust can explode; there is both
empirical and anecdotal evidence to demonstrate this. However, for dust
to explode, it must be in sufficient concentration and a proper ignition
source must exist to transfer energy into the dust cloud to start
combustion. In the example you cite, the ignition source was a
sustained fire, the dust concentration was caused by a large quantity of
existing fine dust in a silo that was storing said material.

What is in dispute is
1) Whether it is even remotely possible to entrain sufficient dust in a
home workshop dust collection system for sufficient time, in sufficient
concentration to be an explosion hazard and
2) Whether a static discharge in a plastic duct will occur across that
concentration of dust, and whether there is sufficient energy in that
spark to start combustion. IIRC, someone posted a number several years
ago when this subject came up regarding the combustion temperature
required to ignite saw dust; the number was significantly higher than
what one could obtain from a simple static spark -- you are much more
vulnerable to glowing pieces of metal that could enter the DC system
from sources such as accidentally grinding metal on one of your tools.

Greg G. wrote:
>Hmmm... folks are getting mighty testy over this one...

Testy over an urban myth? Me? I only like busting the
balls of the myth tellers.

UA100

[email protected] wrote in message news:<[email protected]>...
> referencing..
> http://cnets.net/~eclectic/woodworking/cyclone/Ducting.cfm#Ducting%20Introduction
>
> I have the Jet cartridge 1.5hp unit; rated 1100cfm
>
> Based on the URL, I plan to use sewer & drain pipe. I will use wye's
> and short (1-2') flex hose.
>
> Should I try 6" duct? If I read this correctly, he is saying that no
> reduction should be done.. so I really have to convert all dust ports
> to 6". That's possible for my TS, SCMS, and jointer, but not very
> practical for my planer, BS, and DP.

I have the Jet 1100, but not the cartridge unit. I ran cheapo snap
lock pipe from HD, 6", as the two main lines coming off of it. Then I
fabricated my own 6x6x4" wyes and put 4" aluminum blast gates on each
machine. Then used some black flexible hose from the blast gate to
the machine. The hose I used was the 40' length on Amazon.com, I
think it's a Penn Industries hose. It's something like 40' for $40.
Great value.

Mark & Juanita thus spake:

> Yep, here we go again. A) Silo explosions are not caused by static,
>but usually by an electrical spark on faulty equipment. The energy in a
>spark is far greater than energy produced by a static discharge; it also
>is of longer duration B) the material that causes silo explosion is not
>far courser material, it is actually very fine, very concentrated dust
>produced as a result of moving very many TONS of material in a short
>period of time.
>
> The archives should provide sufficient information to rehash this for
>the curious.

Probably picking nits here...
Although I understand how you came to these conclusions, for the
record, I never directly stated that static caused silo explosions. I
used that as a rational for why dust collectors are often grounded -
in a different paragraph. But by the same token, it could happen. A
spark is a spark. Lightning, electrical equipment, sparking contacts
in switches just thrown are all potential sources of ignition. This
is why they have specialized equipment that is sealed to prevent this
from happening. A Kettering ignition system has a fairly short spark
duration - but it ignites a highly pressurized cylinder full of
atomized fuel - every time. (Hopefully...)

I also never said course material was the fuel for the explosion. Of
course it is finely atomized dust particles. But the average
bystander sees corn, or wheat - larger material than sawdust - which,
incidentally, contains many fine dust-like particles itself. As
anyone who has ever used a dust collector can attest, the friction of
sawdust moving through a plastic pipe generates static.

With this said, a friend has a picture frame shop. When he installed
his dust evacuation system, the inspectors required it to be grounded.
Why? I don't know. Probably the same reason they don't allow PVC air
lines. The chances are 1 in 10,000, but there apparently IS a chance
of something untoward happening. Have I ever seen it or heard a
substantiated case of it happening? No!

I would say, that for myself, a couple of dollars worth of wire is
cheap insurance, and of benefit if only to eliminate that annoying
static shock from touching an ungrounded, static charged thingamabob
in the DC's path.

Just for the record. ;-)


Greg G.

Bay Area Dave said:

>even metal will burn if atomized sufficiently.

Yep, and those magnesium plane parts, hmm...

Personally, I like to throw various metal powders into the fireplace
to see the pretty colors... <g> SWMBO likes it too.


Greg G.

"Bay Area Dave" <[email protected]> wrote in message
news:[email protected]...
> just for the record; we aren't all as skeptical is Unisaw100... I'm with
> you, D&C.
>
> dave

Well, there goes any credibility D&C had....

Dan-o thus spake:

>I just set up a 1.5 HP Penn DC in my 20'x20' shop using 6" sewer & drain
>pipe for the main lines and 4" sewer and drain for branch lines to each
>machine. It will suck the chrome off a trailer hitch! I did not ground
>anything and plan to notify the Wreck immediately if and when there is an
>explosion.

Please include pictures... <g>

Vacuum is nice, but does it maintain enough internal velocity to keep
planer/jointer bits in suspension with 6"? Just curious...


Greg G.

Unisaw A100 said:

>Uh, huh. As I thought.

Hmmm... folks are getting mighty testy over this one...

I could care less if you ground your DC or not, I'm not twisting any
arms - just playing devil's advocate. So don't take it personally.

But, as stated in a previous post:

... a friend has a picture frame shop. When he installed his dust
evacuation system, the inspectors required it to be grounded.

Why? I don't know. Probably the same reason they don't allow PVC air
lines. The chances are 1 in 10,000, but there apparently IS a chance
of something untoward happening. Have I ever seen it or heard a
substantiated case of it happening? No!

I would say, that for myself, a couple of dollars worth of wire is
cheap insurance, and of benefit if only to eliminate that annoying
static shock from touching an ungrounded, static charged thingamabob
in the DC's path.

Just for the record. ;-)


Greg G.

In article <QSOFb.787180$6C4.746315@pd7tw1no>, [email protected] says...
> Hi all,
>
>
>
... snip
> more energy than a static electricity spark,
heckuvalot more. i.e. it was already an open flame with sustained
duration
> but the resulting 40 foot fire
> ball was enough to instill in me a healthy respect for the explosive quality
> of dust. I will for forever remember the wall of heat that over took me
> while I was admiring the way the dust had billowed up in the rising gasses
> of the burning barrel. It was over in milliseconds, left no permanent scars,
> but has left me with the attitude that I will not take any chances with dust
> explosions.
>
> Just for fun I Googled dust explosions, perused the results to see if my
> mileage was not too different to others ( didn't want my first post to be
> attributed to a raving loony) and I happened upon an image that is a dead
> ringer for what is seared into my brain. (pun intended)
> http://www.chemeng.ed.ac.uk/~emju49/SP2001/webpage/boom.jpg
>
> I don't know how much of this is relevant to dust collectors, don't really
> care, but for my money if there is a chance of setting of something like the
> explosion I witnessed and it only takes a couple of dollars and a couple of
> hours then I'm in.
>

I want someone to tell me how they think that wrapping copper wire
around the *outside* of an insulator is going to prevent sparks from
occuring *inside* said insulated space. Since static charge builds up
as a surface charge, I also want to be shown how having a discharge path
on the inside of the collector will actually make the system safer
regarding static discharge from the surface charge. One could postulate
that having the wire on the inside is actually worse, because a
potential from one side of the plastic surface can build up such that a
discharge to the wire residing at some distance from the surface
results. This can become even more of an issue if the wire becomes
airborn, creating a gap for the discharge to take place.


>
>
> Howard H.
>
>
>
>
>
>
> "Unisaw A100" <[email protected]> wrote in message
> news:[email protected]...
> > Mortimer Schnerd, RN wrote:
> > >Dust can be explosive.
> >
> >
> > Prove it.
> >
> > UA100
> "Unisaw A100" <[email protected]> wrote in message
> news:[email protected]...
> > Greg G. wrote:
> > >Hmmm... folks are getting mighty testy over this one...
> >
> > Testy over an urban myth? Me? I only like busting the
> > balls of the myth tellers.
> >
> > UA100
>
>
>

Keeter, you forgot to tell me you are from MO.

Only believe what you see with your own eyes? Never learned anything by
reading or listening to others? A fair amount of skepticism is fine, but
you pretty much are calling folks liars when you refer to someone as a
"myth teller".

Now I've given you reason to get back to busting my chops... :)

dave

Unisaw A100 wrote:

> Greg G. wrote:
>
>>Hmmm... folks are getting mighty testy over this one...
>
>
> Testy over an urban myth? Me? I only like busting the
> balls of the myth tellers.
>
> UA100

even metal will burn if atomized sufficiently.

dave

Greg wrote:

> A rational voice rang out from the void, and 6tester said:
>
>
>>I'm new to the group and don't want to get roasted here, but I have a tale
>>to relate...
>
> <snip>
>
>>more energy than a static electricity spark, but the resulting 40 foot fire
>>ball was enough to instill in me a healthy respect for the explosive quality
>>of dust. I will for forever remember the wall of heat that over took me
>>while I was admiring the way the dust had billowed up in the rising gasses
>>of the burning barrel. It was over in milliseconds, left no permanent scars,
>>but has left me with the attitude that I will not take any chances with dust
>>explosions.
>
>
> Sort of my point. Any remotely combustible product finely atomized
> within an oxygen environment will burn at an accelerated rate - and
> when constrained by the walls of a DC system, *could* result in an
> explosion. Whether big or small doesn't matter - fire is fire.
> Apollo Astronauts aren't *supposed* to be char-broiled in their
> capsule on the launch pad, but it happened.
>
>
>>Just for fun I Googled dust explosions, perused the results to see if my
>
>
> Nice fireball! Reminds me of my youth & home-made rocket experiments.
>
>
>>I don't know how much of this is relevant to dust collectors, don't really
>>care, but for my money if there is a chance of setting of something like the
>>explosion I witnessed and it only takes a couple of dollars and a couple of
>>hours then I'm in.
>
>
> Potential for nice fireballs in your house, no less. I, too, tend to
> err on the side of caution. $3 and 20 minutes? Count me in as well.
>
> Opinions are like as%holes - we've all got one.
> Oh well, made for a mildly entertaining hour, anyway. <g>
>
>
> Greg G.

Greg G wrote...
> I am only reporting facts.

I believe that is what you think you are doing. But, for example,
statements like:

> This stupid thread started (again) over one mention of metal pipe
> replacing grounding the wire that some install on their PVC systems.
> Several companies sell DC ground kits to (IYO) misguided individuals.
> Fire codes in some localities require it in commercial installs.

can lead to confusion. It sounds like you are saying that some fire codes
require commercial installations of PVC ductwork to be grounded.

AFAIK, fire codes that require grounded ductwork in commercial
installations also require the ductwork itself to be metal (or at the
very least, conductive). I have never heard of, and seriously doubt the
existence of any code that requires non-conductive ductwork to be
grounded. It just doesn't make any sense because it is impossible to
"ground" an insulator.

Jim

Greg G wrote...
> WAY too much grief
> over installing $3 worth of wire. Especially considering that the
> negative consequences of doing so are nil.

Two more points to consider. First, at least in this forum, emotion
usually enjoys equal prominence on both sides of the debate. OTOH, the
research and analysis conducted by some who discourage PVC "grounding" is
objectively superior to that done by any who condone it.

And second, the negative consequences may not be insignificant, owing to
the sizes of the probabilities involved. The probability of a dust
explosion ignited by static discharge from PVC piping is vanishingly
small. However, that tiny probability is increased by adding a grounded
conductor on the outside of the pipe. Installing an internal conductor or
screws through the piping have relatively substantial negative
consequences as well. So, the likelihood of some type of undesirable
incident is probably greater -- by a statistically significant margin --
when any of these things are installed.

> Too bad people aren't more interested in the direction our
> economy or world politics is headed.

You haven't followed any of the political discussions around here, have
you? (G)

Cheers!

Jim

Greg G wrote...
> Exploding DC Ducts in Woodshop
> See Post by David Snow
> http://www.talkshopbot.com/messages/26/801.html

Here's a quote of the pertinent part.

"Working with a 1100 cfm vac 3 hp running a planer walked by touched pvc
pipe duct with grounding wire inside etc. woke up about two min. later
aprox. five feet away leaning against the wall that stoped my forward
movement!! oh yea had to replace the fire extingusher after I put the
fire out. I then did the research on what osha requires for factory
setups. nuff said Dave"

This is interesting! More details and a better understanding of the
incident would be useful. However, note that because Dave had a wire
installed inside the pipe, it is a rather poor argument in favor
"grounding" PVC ducting.

Jim

Hi all,



I'm new to the group and don't want to get roasted here, but I have a tale
to relate. Many moons ago I was cleaning out my shop after a long winter of
woodworking projects, I use my compressor to blow the dust that had
accumulated in the shop into the air then vacuumed up the dust that settled
on the floor. I repeated this a few times until my shop was as dust free as
the day I built it. It was not until later in the day that I learned the
power of dust explosions. I had taken all the shop scraps and what not out
to the burning barrel on the back of the property and was finishing up with
yard waste when I remembered that the Shopvac needed to be emptied and the
burning barrel seemed like a good repository for the contents. Now I will
give you that a 45 gallon drum filled about 3/4 full of embers has slightly
more energy than a static electricity spark, but the resulting 40 foot fire
ball was enough to instill in me a healthy respect for the explosive quality
of dust. I will for forever remember the wall of heat that over took me
while I was admiring the way the dust had billowed up in the rising gasses
of the burning barrel. It was over in milliseconds, left no permanent scars,
but has left me with the attitude that I will not take any chances with dust
explosions.

Just for fun I Googled dust explosions, perused the results to see if my
mileage was not too different to others ( didn't want my first post to be
attributed to a raving loony) and I happened upon an image that is a dead
ringer for what is seared into my brain. (pun intended)
http://www.chemeng.ed.ac.uk/~emju49/SP2001/webpage/boom.jpg

I don't know how much of this is relevant to dust collectors, don't really
care, but for my money if there is a chance of setting of something like the
explosion I witnessed and it only takes a couple of dollars and a couple of
hours then I'm in.



Howard H.






"Unisaw A100" <[email protected]> wrote in message
news:[email protected]...
> Mortimer Schnerd, RN wrote:
> >Dust can be explosive.
>
>
> Prove it.
>
> UA100
"Unisaw A100" <[email protected]> wrote in message
news:[email protected]...
> Greg G. wrote:
> >Hmmm... folks are getting mighty testy over this one...
>
> Testy over an urban myth? Me? I only like busting the
> balls of the myth tellers.
>
> UA100

Greg G. wrote:

> Again, I didn't design it, recommend it, or sell it. I am only
> reporting what is required by our commercial fire code.

Should the ground go though a resistor to limit current?

-- Mark

just for the record; we aren't all as skeptical is Unisaw100... I'm with
you, D&C.

dave

DAN & CINDY wrote:

> For all you disbelievers that dust cant explode I've had the unfotunate
> experience of seeing 2 of our local firemen killed in an explosion at our
> local lumber yard. Sure the fire started in silo but the silo contained
> nothing more than sawdust , A short in the dust collecter motor sent a spark
> through the duct system that started what seemed to be a harmless fire, when
> the firefighters arrived they went about putting out the fire as a routine
> call, moments later the silo exploded and sent pieces of the silo over a
> mile away.The 2 firemen killed were spraying water down the top of the silo,
> the explosion was caused by a void ( air pocket) in the material in the
> silo, when it was saturated with water it became heavy and fell to the
> bottom, the dust cloud that was created when the material hit the bottom had
> enough power that when it exploded it sent pieces of the silo over a mile
> away. needless to say what happened to the 2 men that were looking down the
> throat of the silo.
> "Mark & Juanita" <[email protected]> wrote in message
> news:[email protected]...
>
>>In article <[email protected]>, Greg G. says...
>>
>>>Unisaw A100 thus spake:
>>>
>>>
>>>>Greg G. wrote:
>>>>
>>>>>Metal ducting is probably more widely available at 5" and requires no
>>>>>grounding wires.
>>>>
>>>>Why would you need to ground the pipe?
>>>
>>>Oh, God - here we go again...
>>>Convention? Elimination of static buildup?
>>>
>>>Just ask a midwesterner about silo explosions.
>>>Far courser material, yet it CAN explode.
>>>Have I ever seen it? No - maybe 'cause they are grounded by
>>>convention... <g>
>>>
>> Yep, here we go again. A) Silo explosions are not caused by static,
>>but usually by an electrical spark on faulty equipment. The energy in a
>>spark is far greater than energy produced by a static discharge; it also
>>is of longer duration B) the material that causes silo explosion is not
>>far courser material, it is actually very fine, very concentrated dust
>>produced as a result of moving very many TONS of material in a short
>>period of time.
>>
>> The archives should provide sufficient information to rehash this for
>>the curious.
>
>
>

My insurance seem to think that it is - as do the authorities in Europe
after a number of injuries in recent years in factories. The scenario seems
to run something like this - spark generated in the ductwork (e.g. from a
sander, grit from timber, lost carbide tooth, etc.), spark arrives in
collector and smoulders in waste, someone knocks out the dust sack (creating
a stochiastically viable mixture of air and fine wood dust), air/dust
mixture ignites and causes a small explosion which blows the bag off the
extractor, the force of this explosion is not enough to harm anyone but
dislodges all the dust trapped on beams, tops of machines, etc for many
years past, this is turn generates a much larger volume of air/dust which in
turn is ignited by the initial explosion..... This can happen in small
shops, too, but is probably much more of a problem in commercial
environments.

Personally, I'm not so sure any more about the static sparking theory (and
if you follow one of the links of Bill Pentz's site you'll find a properly
researched paper on the subject by an academic which says just that), but
I've heard enough foreign objects striking the ductwork to believe that a
fire or explosion in a collector is possible. Never had one myself, but last
year we did have a dust sack which had been removed at the end of the
working day catch fire.... (luckily outside of the shop)

I'd still tend to earth galv. steel trunking in the same way as I earth
strapped our steel roof trusses, gives lightening or shorts and easier
journey to earth.

Scrit

"Unisaw A100" <[email protected]> wrote in message
news:[email protected]...
> Mortimer Schnerd, RN wrote:
> >Dust can be explosive.
>
>
> Prove it.
>
> UA100

Unisaw A100 thus spake:

>Greg G. wrote:
>>Metal ducting is probably more widely available at 5" and requires no
>>grounding wires.
>
>Why would you need to ground the pipe?

Oh, God - here we go again...
Convention? Elimination of static buildup?

Just ask a midwesterner about silo explosions.
Far courser material, yet it CAN explode.
Have I ever seen it? No - maybe 'cause they are grounded by
convention... <g>


Greg G.

In article <[email protected]>, Greg G. says...
> Unisaw A100 thus spake:
>
> >Greg G. wrote:
> >>Metal ducting is probably more widely available at 5" and requires no
> >>grounding wires.
> >
> >Why would you need to ground the pipe?
>
> Oh, God - here we go again...
> Convention? Elimination of static buildup?
>
> Just ask a midwesterner about silo explosions.
> Far courser material, yet it CAN explode.
> Have I ever seen it? No - maybe 'cause they are grounded by
> convention... <g>
>

Yep, here we go again. A) Silo explosions are not caused by static,
but usually by an electrical spark on faulty equipment. The energy in a
spark is far greater than energy produced by a static discharge; it also
is of longer duration B) the material that causes silo explosion is not
far courser material, it is actually very fine, very concentrated dust
produced as a result of moving very many TONS of material in a short
period of time.

The archives should provide sufficient information to rehash this for
the curious.

Roy Smith wrote:
> In article <[email protected]>,
> "Mark Jerde" <[email protected]> wrote:
>
>> Greg G. wrote:
>>
>>> Now don't get me started on left tilt vs. right tilt. <g>
>>
>> Both! One of each! Two of each! <g> Three saws that tilt both
>> ways! <g>
>>
>> -- Mark
>>
>>
>
> I don't get it. I can understand wanting a left and a right, and it
> certainly makes sense to have two of each (set up for rip and
> crosscut),
> but I don't see what you're going to do with the third of each. Do
> you really cut that many dados?

<vbg> It takes a lot longer to change blades than to cut a piece of wood.
If I had the space (I don't) and the money (I don't -- yet) why not leave a
TS set up to cut double-sided melamine? <g>

BTW, the scar on my left hand from a kickback accident about 6 months ago is
still visible. It wasn't really an "accident" -- I should have taken the
time to put on the guard and splitter. But mounting the spiltter & guard on
my Grizzly contractor table saw, and aligning them, is somewhat of a PITA.
In my "dream shop" I'd have made that cut on the TS with the guard &
splitter permanently installed & the accident would never have happened.

-- Mark

A rational voice rang out from the void, and 6tester said:

>I'm new to the group and don't want to get roasted here, but I have a tale
>to relate...
<snip>
>more energy than a static electricity spark, but the resulting 40 foot fire
>ball was enough to instill in me a healthy respect for the explosive quality
>of dust. I will for forever remember the wall of heat that over took me
>while I was admiring the way the dust had billowed up in the rising gasses
>of the burning barrel. It was over in milliseconds, left no permanent scars,
>but has left me with the attitude that I will not take any chances with dust
>explosions.

Sort of my point. Any remotely combustible product finely atomized
within an oxygen environment will burn at an accelerated rate - and
when constrained by the walls of a DC system, *could* result in an
explosion. Whether big or small doesn't matter - fire is fire.
Apollo Astronauts aren't *supposed* to be char-broiled in their
capsule on the launch pad, but it happened.

>Just for fun I Googled dust explosions, perused the results to see if my

Nice fireball! Reminds me of my youth & home-made rocket experiments.

>I don't know how much of this is relevant to dust collectors, don't really
>care, but for my money if there is a chance of setting of something like the
>explosion I witnessed and it only takes a couple of dollars and a couple of
>hours then I'm in.

Potential for nice fireballs in your house, no less. I, too, tend to
err on the side of caution. $3 and 20 minutes? Count me in as well.

Opinions are like as%holes - we've all got one.
Oh well, made for a mildly entertaining hour, anyway. <g>


Greg G.

Swingman said:

>You've handled yourself well on this subject, Greg ... showed common sense,
>class, and a good deal more charity and than most.

Thanks, but not a subject I *really* wanted to get involved it, nor a
fervent believer in. As I mentioned, just playing devil's advocate
for another side for the coin - one in which there in no *real*
undisputable scientific evidence to support either side. Life is
chaotic - I believe anything can happen, if circumstances permit.

Many of the discussions here devolve into bouts of name calling and
personal attacks - often fairly quickly. IMHO, not a good way to
present either side of a debate.

Now don't get me started on left tilt vs. right tilt. <g>


Greg G.

Jim Wilson said:

>AFAIK, fire codes that require grounded ductwork in commercial
>installations also require the ductwork itself to be metal (or at the
>very least, conductive). I have never heard of, and seriously doubt the
>existence of any code that requires non-conductive ductwork to be
>grounded. It just doesn't make any sense because it is impossible to
>"ground" an insulator.

Yes, metal is *supposed* to be used in commercial installs.

But it IS possible to reduce and dissipate accumulated charges in PCV
through surface leakage so that large discharges to metal objects is
all but eliminated. Of course you can't "ground" PVC in the classic
sense, it is an insulator. But in reality, all materials conduct
electricity to some extent, especially in high humidity conditions,
their resistance is just *extremely* high.

Well anyway, this thread is getting quite tedious. WAY too much grief
over installing $3 worth of wire. Especially considering that the
negative consequences of doing so are nil. Too bad people aren't more
interested in the direction our economy or world politics is headed.

Folks, do what you want, believe what you want.

I'll stick to my conductive, impregnated plastic pipe and enjoy the
peace of mind of knowing that when I brush against a pipe, I'm not
going to get zapped by static discharge - which is my primary concern.

And maybe, somewhere deep down inside, I may even get some comfort in
knowing that I may also avoid that 1 in 1,000,000 chance that my DC is
going to catch fire. The universe is a cruel and chaotic place. <g>

Happy Holidays!


Greg G.

Bay Area Dave said:

>Keeter, you forgot to tell me you are from MO.
>
>Only believe what you see with your own eyes? Never learned anything by
>reading or listening to others? A fair amount of skepticism is fine, but
>you pretty much are calling folks liars when you refer to someone as a
>"myth teller".
>
>Now I've given you reason to get back to busting my chops... :)

Aw, don't mind him. He's just a crusty old fart sparrin' for a fight.
Probably didn't get any this weekend... <g>


Greg G.

Mark & Juanita said:

> I want someone to tell me how they think that wrapping copper wire
>around the *outside* of an insulator is going to prevent sparks from
>occuring *inside* said insulated space. Since static charge builds up
>as a surface charge, I also want to be shown how having a discharge path
>on the inside of the collector will actually make the system safer
>regarding static discharge from the surface charge. One could postulate
>that having the wire on the inside is actually worse, because a
>potential from one side of the plastic surface can build up such that a
>discharge to the wire residing at some distance from the surface
>results. This can become even more of an issue if the wire becomes
>airborn, creating a gap for the discharge to take place.

To begin with, the wire goes on the inside, and is connected to all
equipment and earth ground. And I believe the intention is to reduce
potentials across varying sections of pipe and the metal equipment.
As anyone familiar with science fair projects can attest, easily
generated static charges can be on the order of 20,000 - 80,000 volts.

Again, I didn't design it, recommend it, or sell it. I am only
reporting what is required by our commercial fire code.


Greg G.

Greg G. wrote:

> Now don't get me started on left tilt vs. right tilt. <g>

Both! One of each! Two of each! <g> Three saws that tilt both ways! <g>

-- Mark

On Mon, 22 Dec 2003 23:40:41 -0500, Greg G. wrote:

>Mark & Juanita said:
>
>> I want someone to tell me how they think that wrapping copper wire
>>around the *outside* of an insulator is going to prevent sparks from
>>occuring *inside* said insulated space. Since static charge builds up
>>as a surface charge, I also want to be shown how having a discharge path
>>on the inside of the collector will actually make the system safer
>>regarding static discharge from the surface charge. One could postulate
>>that having the wire on the inside is actually worse, because a
>>potential from one side of the plastic surface can build up such that a
>>discharge to the wire residing at some distance from the surface
>>results. This can become even more of an issue if the wire becomes
>>airborn, creating a gap for the discharge to take place.
>
>To begin with, the wire goes on the inside, and is connected to all
>equipment and earth ground. And I believe the intention is to reduce
>potentials across varying sections of pipe and the metal equipment.
>As anyone familiar with science fair projects can attest, easily
>generated static charges can be on the order of 20,000 - 80,000 volts.
>
>Again, I didn't design it, recommend it, or sell it. I am only
>reporting what is required by our commercial fire code.
>
>
>Greg G.


from
http://mywebpages.comcast.net/rodec/woodworking/articles/DC_myths.html#inside




The inside wire or grounded screws: Many people use a bare grounded
wire inside the ducts. This may provide some amount of leakage
current, but the primary effect is to provide a shorter hop to ground
than if no wire is added. Since the wire has a very small radius, the
field due the charge drawn into it by the static charge is large,
making discharge occur at smaller charge densities than if the wire
was not there. The discharge will be a brush type discharge which will
not ignite the dust. This limits the amount of charge that can build
up, which in turn limits the strength of the field outside the pipe
where your unsuspecting finger is. Basically, this reduces the chance
that your finger will become the shortest path to ground! By limiting
the charge build up, this also reduces the chance of a propagating
brush discharge. Grounded screws poking through the duct wall provide
much the same protection. For a single wire in a 4 inch duct, the
maximum discharge distance is 4 inches. The maximum discharge distance
for screws placed 4 inches apart along the pipe is 4 inches across the
pipe and 2 inches sideways, for a total distance of just under 4.5
inches, so the protection is about the same, and may even be better as
screws have sharp points that increase the strength of the electric
field leading to discharges at smaller charge densities. Because this
type of grounding does not have the potential to cause a propagating
brush discharge, I think this is safer than the external ground wire.
Using very short screws will not cause the jamming up of shavings that
often occurs with the internal ground wire.

Greg G. wrote:
>Just ask a midwesterner about silo explosions.

I'm a midwesterner. Trouble is I don't use my shop for a
silo.

>Far courser material, yet it CAN explode.

It can? Have you proof? Can you refer me to someone whose
shop has *blowed up* onna 'count of PVC pipe and their dust
collector? Can you refer me to a fire department,,, OK, I
think you know I know you can't.

>Have I ever seen it? No - maybe 'cause they are grounded by
>convention... <g>

Uh, huh. As I thought.

UA100

Unisaw A100 said:

>Maybe you can deflate your blow-up doll and send it to me.

SWMBO resents that...

>Be sure to send along the grounding wire.

I'll make sure to do that very thing - wouldn't want static discharge
to zap wee willy. <g>


Greg G.

<Greg G.> wrote in message

> OK - My last words on the subject. Form your own conclusions.

You've handled yourself well on this subject, Greg ... showed common sense,
class, and a good deal more charity and than most.

--
www.e-woodshop.net
Last update: 12/21/03

I have to needle him once in a while, Greg, to see if he'll post either
a series of blank replies for a couple of days, or his infamous two word
reply to me, "Bad Monkey", dazzling us all with his originality. A
couple of times I mimicked his style and he came up with the well worn
phrase of our youth: "monkey see, monkey do". That's why I've suggested
to him time and time again to hire some new writers. :)

Greg wrote:

> Bay Area Dave said:
>
>
>>Keeter, you forgot to tell me you are from MO.
>>
>>Only believe what you see with your own eyes? Never learned anything by
>>reading or listening to others? A fair amount of skepticism is fine, but
>>you pretty much are calling folks liars when you refer to someone as a
>>"myth teller".
>>
>>Now I've given you reason to get back to busting my chops... :)
>
>
> Aw, don't mind him. He's just a crusty old fart sparrin' for a fight.
> Probably didn't get any this weekend... <g>
>
>
> Greg G.

Howard-

before you go any further, read this:
http://mywebpages.comcast.net/rodec/woodworking/articles/DC_myths.html

Bridger

[email protected] thus spake:

>I have the Jet cartridge 1.5hp unit; rated 1100cfm
>
>Based on the URL, I plan to use sewer & drain pipe. I will use wye's
>and short (1-2') flex hose.
>
>Should I try 6" duct? If I read this correctly, he is saying that no
>reduction should be done.. so I really have to convert all dust ports
>to 6". That's possible for my TS, SCMS, and jointer, but not very

IMHO, 6" is probably a big for a 1.5HP unit - real world CFM is
probably lower than advertised - 5" would be a better match. Velocity
needs to kept up, or the material falls out of suspension. Metal
ducting is probably more widely available at 5" and requires no
grounding wires. I believe the no reduction rule applies to runs, not
connection branches - but make up air has to come from somewhere to
keep the velocity up. In consideration of the economics of it all, I
believe short 4" runs to equipment would be fine. Various leakages
would make up some of the difference - or an inlet relief flap at the
end of the run.

JMHO however,

Greg G.

Unisaw A100 said:

>Greg G. wrote:
>>Hmmm... folks are getting mighty testy over this one...
>
>Testy over an urban myth? Me? I only like busting the
>balls of the myth tellers.

My balls are fine, thank you. <g> I perpetuate no myths.
Good Grief, shoot the messenger. I am only reporting facts.

You will notice that I never told anyone to ground their DC system.
This stupid thread started (again) over one mention of metal pipe
replacing grounding the wire that some install on their PVC systems.
Several companies sell DC ground kits to (IYO) misguided individuals.
Fire codes in some localities require it in commercial installs.
Nothing here should be construed as MY recommending anything.

As for me, I use conductive tubing, because I hate the static
attraction that generic plastics generate.

Have a Happy Holiday and Peaceful New Year, Dude.

Greg G.

For all you disbelievers that dust cant explode I've had the unfotunate
experience of seeing 2 of our local firemen killed in an explosion at our
local lumber yard. Sure the fire started in silo but the silo contained
nothing more than sawdust , A short in the dust collecter motor sent a spark
through the duct system that started what seemed to be a harmless fire, when
the firefighters arrived they went about putting out the fire as a routine
call, moments later the silo exploded and sent pieces of the silo over a
mile away.The 2 firemen killed were spraying water down the top of the silo,
the explosion was caused by a void ( air pocket) in the material in the
silo, when it was saturated with water it became heavy and fell to the
bottom, the dust cloud that was created when the material hit the bottom had
enough power that when it exploded it sent pieces of the silo over a mile
away. needless to say what happened to the 2 men that were looking down the
throat of the silo.
"Mark & Juanita" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, Greg G. says...
> > Unisaw A100 thus spake:
> >
> > >Greg G. wrote:
> > >>Metal ducting is probably more widely available at 5" and requires no
> > >>grounding wires.
> > >
> > >Why would you need to ground the pipe?
> >
> > Oh, God - here we go again...
> > Convention? Elimination of static buildup?
> >
> > Just ask a midwesterner about silo explosions.
> > Far courser material, yet it CAN explode.
> > Have I ever seen it? No - maybe 'cause they are grounded by
> > convention... <g>
> >
>
> Yep, here we go again. A) Silo explosions are not caused by static,
> but usually by an electrical spark on faulty equipment. The energy in a
> spark is far greater than energy produced by a static discharge; it also
> is of longer duration B) the material that causes silo explosion is not
> far courser material, it is actually very fine, very concentrated dust
> produced as a result of moving very many TONS of material in a short
> period of time.
>
> The archives should provide sufficient information to rehash this for
> the curious.

Jim Wilson said:

>This is interesting! More details and a better understanding of the
>incident would be useful. However, note that because Dave had a wire
>installed inside the pipe, it is a rather poor argument in favor
>"grounding" PVC ducting.

Hmmm... Missed the mention of the wire in my quick scan. However, he
DOES mention the importance of actually grounding it in the sentence
above. Perhaps he hadn't actually *grounded* the wire he ran in the
pipe - this would lead to quite a charge buildup. Who knows.


Greg G.

Unisaw A100 said:

>It can? Have you proof? Can you refer me to someone whose
>shop has *blowed up* onna 'count of PVC pipe and their dust
>collector? Can you refer me to a fire department,,, OK, I
>think you know I know you can't.

OK - My last words on the subject. Form your own conclusions.
(Rhetorical statement for some...) Results of a 10 minute search.
And not from some self-appointed expert with a misquoted web site.
In this world, most anything is possible-only a fool claims otherwise.

GA Tech studied the factors behind explosions in dust collection
facilities in 2002, and determined that 3 of 175 were caused by static
discharge - more than defective motors and electrical panels.

Wood shop DC explosion and fire at school
http://www.pburgea.org/_Articles/01-02/A06/PHS%20Wood%20Shop%20Fire.htm

Exploding DC Ducts in Woodshop
See Post by David Snow
http://www.talkshopbot.com/messages/26/801.html

Explosion in DC in MFG
http://www.sharon-herald.com/localnews/recentnews/0010/ln102000c.html

General Info on dust/ignition
http://www.warren-group.com/articles/grainpartI.html

Grounding of Dust Collectors and ducts/plastic/static producing parts
See Section 5.12.1.4
http://www.ccbfc.org/ccbfc/committees/former_SC/hazardous/minutes/minutes_9402_E.shtml

As far as I'm concerned, $3 is cheap insurance against these sorts of
things - in addition to the reduction in unpleasant static discharge
to your person.

Ciao,

Greg G.

George E. Cawthon wrote:
>I have no idea if wood dust has ever caused an explosion in
>a wood shop, but fine dust can be explosive.

A'yup. And my Grandma's face burst into flames when she was
flying jets over the Sinai.

Sorry, you'da had to been here for more than the last week
to be getting that one George.

UA100

Mortimer Schnerd, RN wrote:
>Dust can be explosive.


Prove it.

UA100

In article <[email protected]>,
"Mark Jerde" <[email protected]> wrote:

> Greg G. wrote:
>
> > Now don't get me started on left tilt vs. right tilt. <g>
>
> Both! One of each! Two of each! <g> Three saws that tilt both ways! <g>
>
> -- Mark
>
>

I don't get it. I can understand wanting a left and a right, and it
certainly makes sense to have two of each (set up for rip and crosscut),
but I don't see what you're going to do with the third of each. Do you
really cut that many dados?

I just set up a 1.5 HP Penn DC in my 20'x20' shop using 6" sewer & drain
pipe for the main lines and 4" sewer and drain for branch lines to each
machine. It will suck the chrome off a trailer hitch! I did not ground
anything and plan to notify the Wreck immediately if and when there is an
explosion.


<[email protected]> wrote in message
news:[email protected]...
> referencing..
>
http://cnets.net/~eclectic/woodworking/cyclone/Ducting.cfm#Ducting%20Introduction
>
> I have the Jet cartridge 1.5hp unit; rated 1100cfm
>
> Based on the URL, I plan to use sewer & drain pipe. I will use wye's
> and short (1-2') flex hose.
>
> Should I try 6" duct? If I read this correctly, he is saying that no
> reduction should be done.. so I really have to convert all dust ports
> to 6". That's possible for my TS, SCMS, and jointer, but not very
> practical for my planer, BS, and DP.
>
> I have a 23x18 shop. Planning to place DC in corner.. and duct along
> the 23' wall, with wye's off to a TS/Jointer/Planer/BS area.. (closest
> to DC), SCMS area, and DP area
>
> DC
> |
> BS \ |
> \ |
> J/TS__ /
> P |
> |
> |
> SCMS_/
> |
> |
> |
> |
> DP_ /
>
>
>

Greg G. wrote:
>My balls are fine, thank you. <g> I perpetuate no myths.

You mean, you didn't write what you wrote a couple/few
messages up? Bring Sybil back to the keyboard, I want to
ask her something.

>Good Grief, shoot the messenger. I am only reporting facts.

Facts? Please include foot notes.

>You will notice that I never told anyone to ground their DC system.
>This stupid thread started (again) over one mention of metal pipe
>replacing grounding the wire that some install on their PVC systems.

So again, why do you feel there is a need for a grounding
wire? Grain storage in my hobby shop dust collector?

>Several companies sell DC ground kits to (IYO) misguided individuals.
>Fire codes in some localities require it in commercial installs.
>Nothing here should be construed as MY recommending anything.

And again, why do I need the metal ducting you recommended?

>As for me, I use conductive tubing, because I hate the static
>attraction that generic plastics generate.

There you go. A true statement of a true fact and from
everything factual that has been gathered on the subject the
only real reason to choose metal over plastic. OK, to be
fair there are other reasons. :-)

>Have a Happy Holiday and Peaceful New Year, Dude.

A'yup, and you and urine also.

UA100, who is real sorry for you that you felt you needed to
state what you stated and you can't remeber what you said
but what the hell, it's been real fun and the sport is
priceless...

Greg G. wrote:
>Metal ducting is probably more widely available at 5" and requires no
>grounding wires.




Why would you need to ground the pipe?

UA100

Unisaw A100 wrote:
> Greg G. wrote:
>> Metal ducting is probably more widely available at 5" and requires no
>> grounding wires.
>
> Why would you need to ground the pipe?


Dust can be explosive.



--
Mortimer Schnerd, RN

[email protected]
http://www.mortimerschnerd.com