I recently replumbed my PVC DC pipes in my one-man shop. The internal
ground wires were causing blockages, so I took them out. My system is
U-shaped, with a trash can cyclone in the middle, right next to the DC
itself. The longest path is about 12 feet. I left short, grounded
spikes going through the pipe walls in place of the internal ground
wires. The trash can is metal and grounded. All of the tools are
I do not have _any_ signs of static electricity, dust dosen't stick to
the inside or outside of the tubes.
I am tired of local salesman repeating "friend of a friend" stories
about DC explosions.
Can anyone point me to a FACTUAL account online? I cannot find one
Ask the salesman to provide documented evidence of PVC in a home shop
causing an explosion because of static. It has to be a home shop.
He/She won't and can't provide one, because it doesn't exist.
And I went through the same exhaustive search you did before I installed
I've been in the plastics industry for 33 years We move material through
PVC pipes. Ours is not a large plant, but we move 20,000 pounds a day,
others do much more. Static is a problem and must be dealt with, but there
has never been a documented explosion. I did see a guy get taken down from
a static shock though when a ground became faulty. This was at a much
higher potential that a wood shop would have.
Somewhat related, but not about explosions.
Where did you get the PVC you used? I haven't been too happy with the stuff
at the Borg - very limited selection of fittings and diameters. Is there a
good online mail-order place to get PVC for dust collection purposes? I see
that Penn STate has some "economy" metal fittings and duct in their newest
catalog, maybe that's worth looking at.
There are no stupid questions.
There are a LOT of inquisitive idiots.
On Wed, 27 Aug 2003 15:12:16 GMT, "Mike in Mystic"
All I needed for the original and the re-plumb were "T", "Y", 45 & 22
1/2 degree turns, cleanouts, and straight pipes. I use mostly "Y"
fittings at junctions. I added one section of aluminum dryer pipe for
the drill press. This stuff can be bent into place and it stays where
you put it. There isn't enough suction to collapse it, as the gate is
at the DC end of the dryer hose, not the DP end.
I found a clear plastic cement, in caulk type tubes, at a local
hardware store. My blast gates fit inside a normal 4" pipe. This
clear cement is great for gluing the blast gates into the PVC pipe.
If there is a fitting where a blast gate needs to go, I put a short
piece of straight pipe between the gate and the fitting.
Only one I know of happened to me. Dust collection system was a broom and a
metal trash can that I had filled with a mixture of sawdust (fine) and
shavings. Took it out to the burn barrel which had fire in it and dumped
it. It went Ka-Boom. Not an enclosed system and not real smart of me, but
the only one I have ever really known of. Scared me and a passing motorist
out of a weeks growth.
Just about any very fine dust will explode when mixed with a lot of
air. Sawdust is pretty bad that way, grain dust is much worse. I've
had pretty good fireballs at times just tossing a dustpan full of
sawdust into the shop stove.
WRT DC systems, I suspect that only a wide belt sander would generate
enough fine dust to even begin to pose an explosion threat in a normal
On Wed, 27 Aug 2003 16:16:29 GMT, Jim Mc Namara wrote:
It's like how you have to mix gasoline with just the right mixture of air
in your car's engine for the explosion to happen. If the dust particles
are fine enough, and they are mixed well with the air, it can be very
Same thing happens with flour -- if you throw a handful of flour over a lit
stove burner, it can explode.
I'm sure a chemist or physicist can describe exactly what's going on, but
I'm neither and I just know what the cause and effect is...
It is of interest to note that while some dolphins are reported to have
learned English -- up to 50 words used in correct context -- no human being
I'm neither, but studied a bit about explosives many, many years ago (a fun,
but noisy chemistry course - amazing how many things can be turned into
The only difference between a fire and an explosion is the rate of combustion.
With fine dusts, there's lots of surface area in contact with oxygen. Add a
heat and once combustion starts, it proceeds at a rapid rate - boom instead
of whoosh. Take a block of wood (before turning it into dust) and only its
outer surface is exposed to significant oxygen. Light it and the surface burns
more slowly - no explosion.
Fire = fuel + oxygen (air) + heat (spark)
The fire or explosion becomes more intense when the first two
ingredients are fine particles. It makes sense to be concerned about
DC explosions, yet very few people here have first-hand experience
with explosions. I recommend metal tubing for DC ductwork for two
reasons: static charges are minimized, metal is non-combustionable
and the smooth interior reduces turbulence.
On Wed, 27 Aug 2003 10:52:49 -0500, "Sweet Sawdust"
Comming from an electricians point of view in commerical applications
electrical inspectors take grounding of dust collection systems VERY
seriously. Ofcourse nobody in their homeshop is moving as much dust as a
large industrial shop. But it's all proportial
As someone else posted, static electricity can be just as lethal as
generated current from a power source
Think about it this way: what does it cost to add maybe 100' of #14 wire?
maybe $25 prolly closer to $10, and it sure beats sitting in a hospital
giving blood and having MIR's done on'ce you been shock to make sure your
still not burning on the inside. It's not that big of a deal. Is it worth
it? I think so
Who knows, you might be the first documented case!
It's not the cost...it's the effectiveness -- running the wire
through the pipe has negligable effect.
Why? I'm no expert, but it's pretty simple. The concern is static
electricty. Note the STATIC part. It is called static because it is
a stationary charge within a non-conducting material. In this case,
air. The only part of the air that will be grounded is the air
immediately surrounding the wire. The farther it is from the wire,
the more static charge it can build before the charge can move to
the grounded wire. The air on the _other_ side of the pipe sees
negligable effect from the presence of the wire.
Ever play with one of the static-charge generators in high-school
physics class? Even with a LARGE static potential (many kvolts),
you have to get a ground pretty close to get it to jump.
Just a few things to think about...ground away if it makes you
I _had_ a ground wire, just as you describe. I can see no benefit of
it, and no difference in static electricity with or without it.
However, with the ground wire, I had frequent clogs, without it, none.
B a r r y :
Fine Woodworking ran an article debunking
the PVC dangers for dust collection. The author's name is
Rod Cole, the issue is #153 = Winter 2001/2002, page 48.
Might have additional information to make you feel
comfortable. I thought, given the amount of wood dust
I would generate, the biggest danger would be a hot
ember from a tooth flying off a saw and being sucked up
into a bag. I do know that happened to someone I know. He
had metal pipe.
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