Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?

"nigel" wrote in message
ups.com...
Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?


I can only imagine the static build up that will happen. I am in the middle
of putting up my collector system and the amount of plastic (ABS) shavings
that stick to the cut pipes is amazing. The stuff is everywhere. Stuck to
the saw, the walls, the piping, me; I mean everywhere. I will definitely
have to try to ground this somehow. I was thinking of grounding to nearby
110V outlet cover plate screws. Is this a viable way to go?

Paul

On Sat, 13 Nov 2004 21:01:39 GMT, "Paul in MN"
wrote:


"nigel" wrote in message
oups.com...
Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?


I can only imagine the static build up that will happen. I am in the middle
of putting up my collector system and the amount of plastic (ABS) shavings
that stick to the cut pipes is amazing. The stuff is everywhere. Stuck to
the saw, the walls, the piping, me; I mean everywhere. I will definitely
have to try to ground this somehow. I was thinking of grounding to nearby
110V outlet cover plate screws. Is this a viable way to go?

Paul


That will work if the screw is indeed grounded, but it is better to
use a pipe you know is buried into the ground.

Phisherman wrote:
On Sat, 13 Nov 2004 21:01:39 GMT, "Paul in MN"
wrote:


"nigel" wrote in message
ups.com...
Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect
it to DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ...
metal would seem to be proof against the whole thing.
What do the experts have to say on this?


I can only imagine the static build up that will happen. I am in
the middle of putting up my collector system and the amount of
plastic (ABS) shavings that stick to the cut pipes is amazing. The
stuff is everywhere. Stuck to the saw, the walls, the piping, me; I
mean everywhere. I will definitely have to try to ground this
somehow. I was thinking of grounding to nearby 110V outlet cover
plate screws. Is this a viable way to go?

Paul


That will work if the screw is indeed grounded, but it is better to
use a pipe you know is buried into the ground.

I had a lot of electrical "book learnin'" in kollege but my practical
knowledge is very low. In this situation, grounding a DC to a good earth
ground, should there be a current-limiting resistor somewhere between the
water pipe and wire going through the DC system? If so, what size?

Thanks.

-- Mark

"Mark Jerde" wrote in message
newstvld.1341$GV5.185@trnddc04...

I had a lot of electrical "book learnin'" in kollege but my practical
knowledge is very low. In this situation, grounding a DC to a good earth
ground, should there be a current-limiting resistor somewhere between the
water pipe and wire going through the DC system? If so, what size?


It's not necessary since the connection keeps the wire at the same potential
(or very close to) ground. There is a very small current flowing through
the wire. To install a resistor would guarantee that the wire has a small
potential on it.

Frank Ketchum wrote:
"Mark Jerde" wrote in message
newstvld.1341$GV5.185@trnddc04...

I had a lot of electrical "book learnin'" in kollege but my practical
knowledge is very low. In this situation, grounding a DC to a good
earth ground, should there be a current-limiting resistor somewhere
between the water pipe and wire going through the DC system? If so,
what size?


It's not necessary since the connection keeps the wire at the same
potential (or very close to) ground. There is a very small current
flowing through the wire. To install a resistor would guarantee that
the wire has a small potential on it.

I got the idea from (IIRC) the "grounding straps" sometimes used when
repairing computers. It's my understanding these all have a resistor in
them to limit the current flowing through the repair-person in the event of
current-to-ground.

As a kid I was badly shocked by 1960's era tools (*) and I admit I may be
overly concerned about a direct circuit to ground (especially since the
ground wire of a standard 3-prong outlet does the same thing if I understand
home wiring correctly). But suppose I'm concerned about doing something
really stupid like grabbing the DC grounding wire in a sweaty hand, then
biting through the cord of my Skilsaw. Would a properly-sized resistor
between the DC grounding wire and ground help in this situation?

-- Mark

(*) Most memorable: I turned on a sheep shearing machine, got a whale of a
shock, couldn't turn it off and had a hard time letting go. :-(
Fortunately the floor of the sheepshed was fairly dry and I was finally able
to drop the d*mn thing. If the manure had been fresh it may have killed me.

On Sat, 13 Nov 2004 21:59:49 GMT, "Mark Jerde"
wrote:

In this situation, grounding a DC to a good earth
ground, should there be a current-limiting resistor somewhere between the
water pipe and wire going through the DC system?

No.

Resistors in grounding systems are only there when grounding
personnel. It's not needed for static, but it can save lives. An
accidental mains-voltage electric shock can be painful in a typical
situation, but fatal if you have an arm grounded with a low-impedance
path to ground. A mere few megohms makes no difference to grounding
effectiveness, but it's a significant barrier to mains voltages.

--
Smert' spamionam

Andy Dingley wrote:
On Sat, 13 Nov 2004 21:59:49 GMT, "Mark Jerde"
wrote:

In this situation, grounding a DC to a good earth
ground, should there be a current-limiting resistor somewhere
between the water pipe and wire going through the DC system?

No.

Resistors in grounding systems are only there when grounding
personnel. It's not needed for static, but it can save lives. An
accidental mains-voltage electric shock can be painful in a typical
situation, but fatal if you have an arm grounded with a low-impedance
path to ground. A mere few megohms makes no difference to grounding
effectiveness, but it's a significant barrier to mains voltages.

Suppose I'm (irrationally) afraid of doing something stupid, like wrapping
the DC ground wire 12 times around my arm, then shooting a 16d nail through
my thumb into the live hot wire on my Skilsaw. What are the specs for a
resistor to put between the DC grounding system and the water pipe to limit
the current flow yet allow for DC static discharge?

Or can someone talk me out of a fear of an open megaamp path-to-ground
throughout my shop?

Thanks.

-- Mark

On 13 Nov 2004 12:57:13 -0800, "nigel" wrote:

Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?

If your tubing is metal, that will dissipate the static charges. I
have plastic tubing with a spiral wire embedded. I used to get static
shocks before I grounded the wire.

On 13 Nov 2004 12:57:13 -0800, "nigel" wrote:

Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

This is really stupid when you think about the fact that you're
wrapping wire around an insulating material. G

Slide a wire tap along the coil, and tune radio stations!

Barry

Not so sure it's stupid - this is static charge we're talking here, not
anything with a significant current.

"nigel" wrote in message
ups.com...
Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.


Only make the connection at one point. The most logical point would be to
ground the wire at the DC end. Run wires out all the way to the ends where
your machines hook up to it but don't connect it at that point. Ground
should only connected at one point.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?

The pipe itself is the conductor in metal systems and should still be
grounded at one point.

"nigel" wrote in message
ups.com...

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?

You can ground the system if you have problem with getting shocks from it.
Its not necessary, from a safety point of view. I liive in Houston where
the humidity is relatively high and I have no problems at all running
ungrounded.

Bob

On 13 Nov 2004 12:57:13 -0800, "nigel" wrote:

Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around.

It builds up. If this is a nuisance to you, then ground it.

There's no safety hazard to static discharge (in a woodworking DC).
The two real safety risks are static discharge mixed with flammable
solvent vapour, or sucking up a hot ember into the dust stream.

Grounding is hard to do reliably. An internal wire will suffer dust
erosion. The worst case for static buildup is a metal flange in the
plumbing that's insulated by plastic pipe (it creates a capacitor), so
make sure that such things are earthed by external bonding wires.
--
Smert' spamionam

What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

Well, what I heard is that Saddam's entire WMD program is based on
this theory and that's why we be having such a hard time finding them
WMD's, 'cause we just walk right on by all a these PVC pipes laying
around all over the place, not realizing that they only need to be
hooked up to a dust collectorto be turned into explosive deevices,
which is debilishly clebber when ya thinks about it.




On Sat, 13 Nov 2004 20:26:54 -0600, Unisaw A100
wrote:

What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

"Unisaw A100" wrote in message
...
What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

Interesting. So.....

In the book Woodshop Dust Control, Sandor
Nagisygnskfiwef(something-or-other) recommends that the reader NOT use
plastic pipe for the DC system, and shows a lot of detail on grounding
plastic pipe to prevent an explosion. He seems to consider it a real risk.

Yet the concensus here is that it's not a risk in a small-shop environment.
(also other threads have pointed to some good sources of info on why an
explosion is unlikely).

In that book, he also recommends that a DC not be located near a furnace or
water heater - appliances with a pilot light. Is he being overly cautious
in this warning, too? As long as the DC has decent bags so it's not blowing
dust right through, how likely is it that there would be a high enough
concentration of dust to be ignited from a pilot light?

"Keith Carlson" wrote in message
news:6m2md.408724$D%.261058@attbi_s51...
"Unisaw A100" wrote in message
...
What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

Interesting. So.....

In the book Woodshop Dust Control, Sandor
Nagisygnskfiwef(something-or-other) recommends that the reader NOT use
plastic pipe for the DC system, and shows a lot of detail on grounding
plastic pipe to prevent an explosion. He seems to consider it a real risk.

Yet the concensus here is that it's not a risk in a small-shop
environment.
(also other threads have pointed to some good sources of info on why an
explosion is unlikely).

In that book, he also recommends that a DC not be located near a furnace
or
water heater - appliances with a pilot light. Is he being overly cautious
in this warning, too? As long as the DC has decent bags so it's not
blowing
dust right through, how likely is it that there would be a high enough
concentration of dust to be ignited from a pilot light?



Well - even though I'm not answering your questions, let me throw another
twist into the game. Explosive environments, and by that I mean truly
explosive environments, require electrical switches that are rated for that
environment, so that the spark that typically occurs when you throw your
basic household light switch, does not cause an explosion. So - when was
the last time you heard of a dust explosion in a woodworking shop from a
light switch being thrown? I realize you could make an argument that an
open flame is a higher concentration of heat than a spark, if the threat of
explosion was truly as great as is claimed by some, wouldn't you think there
would be at least a mention of explosive environment light switches?
--

-Mike-

On Mon, 15 Nov 2004 13:41:22 GMT, "Keith Carlson"
wrote:

"Unisaw A100" wrote in message
.. .
What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

Interesting. So.....

In the book Woodshop Dust Control, Sandor
Nagisygnskfiwef(something-or-other) recommends that the reader NOT use
plastic pipe for the DC system, and shows a lot of detail on grounding
plastic pipe to prevent an explosion. He seems to consider it a real risk.

yup. he bought the whole load of BS too. it's a shame, 'cause he's a
pretty good teacher.





Yet the concensus here is that it's not a risk in a small-shop environment.
(also other threads have pointed to some good sources of info on why an
explosion is unlikely).

In that book, he also recommends that a DC not be located near a furnace or
water heater - appliances with a pilot light. Is he being overly cautious
in this warning, too? As long as the DC has decent bags so it's not blowing
dust right through, how likely is it that there would be a high enough
concentration of dust to be ignited from a pilot light?


let's make a clear distinction between production shops and home shops
here.

in production shops there are large machines, multiples of them,
running continuously, each making lots of dust. this is an environment
where plastic piping is a hazard and AFAIK illegal.

in home shops this is not the case.

there are plenty of non-static discharge hazards associated with dust
collectors in home shops. big bags of sawdust are a ready source of
fuel just waiting for a source of ignition. vacuum up a cigarette butt
or a nail that sparks off of some metal part inside the DC and you
could have a smouldering fire inside the DC that erupts into full
ignition hours after you've shut off the lights and gone to bed.

I fail to see how a pilot light could do this short of sucking big
piles of dust through the piloted device, but someone somewhere might
be able to pull it off ; ^ ) more likely is that the DC would blow
out the pilot...

On Mon, 15 Nov 2004 12:57:49 -0700, wrote:

let's make a clear distinction between production shops and home shops
here.

Why ? The physics is the same.

If plastic piping is a no-no for commercial workshops in your
jurisdiction, then that's to reduce the _consequences_ of a fire (and
they do happen, for many reasons). Plastic piping, and unearthed too,
is in regular use for the flexible sections of DC hookups.

If I had a roof mounted central DC system, I'd want steel pipe too.
--
Smert' spamionam

On Tue, 16 Nov 2004 03:42:35 +0000, Andy Dingley
wrote:

On Mon, 15 Nov 2004 12:57:49 -0700, wrote:

let's make a clear distinction between production shops and home shops
here.

Why ? The physics is the same.

home shops never involve anywhere near the volume of dust needed to
generate a hot static discharge into a dust cloud dense enough to
sustain it. that takes a dust collector in the 40 HP range pulling
from multiple high volume dust producing machines at once. while in
theory a home shop could create the right conditions, in practice it's
never happened and never will.




If plastic piping is a no-no for commercial workshops in your
jurisdiction, then that's to reduce the _consequences_ of a fire (and
they do happen, for many reasons).

not just to reduce the conscequences- also to reduce the sources.



Plastic piping, and unearthed too,
is in regular use for the flexible sections of DC hookups.

that's ABS flex, not long straight sections of PVC



If I had a roof mounted central DC system, I'd want steel pipe too.

steel pipe is the preferred installation. for home shops, PVC is very
convenient.

Andy Dingley wrote:

On Mon, 15 Nov 2004 12:57:49 -0700, wrote:

let's make a clear distinction between production shops and home shops
here.

Why ? The physics is the same.

But the volume of dust handled by the collector may be different. CWG has a
planer that is bigger than my truck. Somehow I think that when it's
turning a piece of 8/4 lapacho into 5/4 it produces a little more in the
way of shavings and dust and whatnot than my 13" Delta.

Whether the volume is high enough to constitute an explosion hazard in the
event of a static discharge in the system, I have no idea.

If plastic piping is a no-no for commercial workshops in your
jurisdiction, then that's to reduce the _consequences_ of a fire (and
they do happen, for many reasons). Plastic piping, and unearthed too,
is in regular use for the flexible sections of DC hookups.

If I had a roof mounted central DC system, I'd want steel pipe too.

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

Keith Carlson wrote:

"Unisaw A100" wrote in message
...
What do the experts have to say on this?


To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

That's the facts, the whole facts and nothing but the facts.

UA100, stopping at the Lancome' counter after suiting up to
go fly with Grandma, over the Sinai of course...

Interesting. So.....

In the book Woodshop Dust Control, Sandor
Nagisygnskfiwef(something-or-other) recommends that the reader NOT use
plastic pipe for the DC system, and shows a lot of detail on grounding
plastic pipe to prevent an explosion. He seems to consider it a real risk.

Yet the concensus here is that it's not a risk in a small-shop environment.
(also other threads have pointed to some good sources of info on why an
explosion is unlikely).

In that book, he also recommends that a DC not be located near a furnace or
water heater - appliances with a pilot light. Is he being overly cautious
in this warning, too? As long as the DC has decent bags so it's not blowing
dust right through, how likely is it that there would be a high enough
concentration of dust to be ignited from a pilot light?

I could be that Sandor Nagyszalanczy is referring to a commercial wood shop and
avoiding a law suit.. The book is not just written for the hobbyist.

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

Keith Carlson wrote:
In the book Woodshop Dust Control, Sandor
Nagisygnskfiwef(something-or-other) recommends that the reader NOT use
plastic pipe for the DC system, and shows a lot of detail on grounding
plastic pipe to prevent an explosion. He seems to consider it a real risk.



As I said,

To date none of the experts have come up with a single
itty-bitty bit of evidence that PVC piping will lead to a
dust collector explosion.

And this includes Sandor.

UA100, who is mentioned by name on the acknowledgements page
of Sandor's book Power Tools...

On Mon, 15 Nov 2004 13:41:22 GMT, "Keith Carlson"
wrote:

As long as the DC has decent bags so it's not blowing
dust right through, how likely is it that there would be a high enough
concentration of dust to be ignited from a pilot light?

Very unlikely. The research I've seen (Sorry, I don't have a cite immediately
available) indicates that in order for a dust cloud to support a flame front,
the visibility in the cloud would be on the order of a meter. That's a pretty
thick dust cloud. Based on that, the rule of thumb I use is - If I can still see
the far wall of the shop through the dust, an explosion is the least of my
worries.


Tom Veatch
Wichita, KS USA

On Sat 13 Nov 2004 02:57:13p, "nigel" wrote in
ups.com:
I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?

Did anybody catch that Mythbusters show where they tried to make the
Static Canon?

The myth is that a construction worker finds a really nice piece of large
diameter, about 8-10 inch, plastic pipe and wants to use it but it's all
dirty so he sandblasts it at the site and builds up such a huge static
charge on it that when he walks around its end, it shoots a lightning
bolt out of it and blows him across the compound.

They tried everything. Couldn't even make the thing spark. They had a
voltmeter on it, and it kept building up a little charge and then
dissipating.

As someone else has said, the stuff is an insulator. Grounding the
outside grounds only the outside. Don't need a resistor, you're only
sending a few volts to the ground. But any charge inside the pipe is
still there.

I've also seen articles on attempts to duplicate a shop explosion. They
found that the dust particles have to be a certain size, and be dispersed
in the air in such a way that each ignited particle ignites the particle
next to it, and in such a manner that it creates an explosion-like
combustion. They found that when they finally got the conditions correct
for a dust explosion, the air was so full of fine-particle dust they
could barely see. And any air currents in the area screwed it up. The
dust particles weren't close enough together. Their conclusion was, if
you have the correct conditions to create a dust explosion, you should be
more worried about breathing than an explosion.

Want me to hunt around for the article? I think it might have been posted
to this very newsgroup.

Dan

So the general word is that there's no safety hazard involved - saw
dust is obviously different to flour, for example.

That's what I was looking to be sure about! My new shop will be in a
building that doesn't belong to me and as the lawyers here in europe
are starting to get almost as trigger happy as in the USA I wanted to
be sure I wasn't not making myself negligent through ignorance.
Thanks people ....

In article .com,
nigel wrote:

So the general word is that there's no safety hazard involved - saw
dust is obviously different to flour, for example.

True, but MDF dust is not much different than flour.

Lou

nigel did say:

as the lawyers here in europe
are starting to get almost as trigger happy as in the USA

Sorry to hear that.

--
New project = new tool. Hard and fast rule.

On Sat, 13 Nov 2004 13:57:13 -0700, nigel wrote
(in article . com):

Following on from the recent DC discussion ... what is the deal with
static charge buildup with all this dust flying around. I've heard
recommendations to add wire spirals around the tubing and connect it to
DC and machine grounds at each end.

I imagine this is only a problem with plastic tubes/conduits ... metal
would seem to be proof against the whole thing.
What do the experts have to say on this?


I read somewhere on-line (the dust collection info site?) about a factory
using PVC and how everyone would get nasty static shocks from it. They tried
the usual tricks of wire, etc but none really worked. What finally did work
was a strip of the metal (aluminum ?) duct tape in a strip along the inside
of the PVC and another strip along the outside. The two strips were then
connected together with several holes drilled through the pipe wall and
fastened with a bolt and washers. This was then earth grounded. Something
about the greater surface area of the conductor in the pipe doing a better
job of collecting those pesky extra electrons....
-Bruce

On Sun, 14 Nov 2004 11:22:12 -0700, Bruce wrote:

I read somewhere on-line (the dust collection info site?) about a factory
using PVC and how everyone would get nasty static shocks from it. They
tried the usual tricks of wire, etc but none really worked. What finally
did work was a strip of the metal (aluminum ?) duct tape in a strip along
the inside of the PVC and another strip along the outside. The two strips
were then connected together with several holes drilled through the pipe
wall and fastened with a bolt and washers. This was then earth grounded.
Something about the greater surface area of the conductor in the pipe
doing a better job of collecting those pesky extra electrons.... -Bruce

Musta been fun getting that tape on the inside of the pipe...

-Doug