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Re: [Electronics_101] Re: Flash Fires In PVC Pipes

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  • Stefan Trethan
    ... I d be reasonable if that s what you are asking. I thought the one implies the other, especially now. But you know politics is not allowed here. ST
    Message 1 of 18 , Dec 2 12:39 AM
      On Sat, 02 Dec 2006 08:09:26 +0100, <JanRwl@...> wrote:

      > In a message dated 12/1/2006 8:35:24 P.M. Central Standard Time,
      > stefan_trethan@... writes:
      >> I do apologize if you had a kindney stone, but saying something doesn't
      >> happen just because it didn't happen to you is just stupid.
      >> Even if you never had an accident before, does it make it reasonable to
      >> drive without a seatbelt or drunken?

      > ST, if you were American, I bet you'd be a Democrat!


      I'd be reasonable if that's what you are asking. I thought the one implies
      the other, especially now.

      But you know politics is not allowed here.

      ST
    • Joseph Plowick Jr.
      What makes you think he s not American...He very hard headed & argumentative. But PLEASE don t start him on politics. ROFL JanRwl@AOL.COM wrote: In a message
      Message 2 of 18 , Dec 2 5:24 AM
        What makes you think he's not American...He very hard headed & argumentative. But PLEASE don't start him on politics. ROFL

        JanRwl@... wrote:
        In a message dated 12/1/2006 8:35:24 P.M. Central Standard Time,
        stefan_trethan@... writes:

        I do apologize if you had a kindney stone, but saying something doesn't
        happen just because it didn't happen to you is just stupid.
        Even if you never had an accident before, does it make it reasonable to
        drive without a seatbelt or drunken?

        ST, if you were American, I bet you'd be a Democrat!

        [Non-text portions of this message have been removed]






        ---------------------------------
        Everyone is raving about the all-new Yahoo! Mail beta.

        [Non-text portions of this message have been removed]
      • Dave Mucha
        ... Chris, et-al, This discussion has little thought behind it. Sorry guys. but if you run anything past anything else, there is a possibility of static
        Message 3 of 18 , Dec 2 5:39 AM
          --- In Electronics_101@yahoogroups.com, "lcdpublishing"
          <lcdpublishing@...> wrote:
          >
          > The discussion isn't about whether or not dust explosions can
          > happen - that is well know. The discussion is if it can happen in a
          > dust collection system used in a home woodworking shop.
          >

          Chris, et-al,

          This discussion has little thought behind it. Sorry guys.

          but if you run anything past anything else, there is a possibility of
          static electricity conformiting. Just a simple fact.

          Drop water past a ring and a tiny charge will occur. place that ring
          under running water and you get more charge. There is a guy who shows
          how to make a tiny generator by using this property on a waterfall.

          As for the exhaust system.

          wood dust (particulate) does have a LEL or Lower Explosive Level.
          with the proper atmosphere and a source of combustion, fuel and
          oxygen, you can get an explosion. below the LEL, there is little
          risk. above it, there is a HUGE risk.


          From the MSDS of wood: (yes, wood has an MSDS)

          UNUSUAL FIRE AND EXPLOSION HAZARDS:
          Depending on moisture content and
          more importantly, particle diameter,
          wood dust may explode in the
          presence of an ignition source.
          An airborne concentration of
          40 grams (40,000 mg) of dust per
          cubic meter of air is often used as
          the LEL for wood dust.

          1 m^3 = about 35 cu feet.
          4" pipe x 900 CFM = 23m^3 per min
          or about 2 pounds per minute of dust.

          PVC pipe is a great storage medium for those little charges.
          Lots of wood dust can create lots of tiny charges
          pvc is a poor conductor so it does need a drain wire.

          Like plane crashes, or death by bee stings, they are extremely
          infrequent. (please no political comments, you can pick any analogy,
          these were not chosen for any particular reason)

          There is a level of complacency we all achieve.
          when was the last time you backed up your hard drive ?
          when was the last time you handled an IC without a static strap on
          your wrist ?

          An exhaust duct explosion in a home shop is rare for a few reasons.
          #1) a continuous stream of wood is not present
          #2) the pipe does not hold the charge well
          #3) there are few opportunities for a spark

          A wire on the outside of the pipe is of little use. Using metal for
          the pipe is the obvious solution, but not as slick as plastic.
          Drilling and tapping a hole, then screwing in a metal screw would
          allow the charge to drain to an external wire.

          Another example; Car tires have become more wear resistant and there
          was a time before they started adding some sort of conductive material
          into the tires when the car would build up a charge and when you
          exited the car, you would get a shock. There have been many fires
          from filling a car when that charge encountered the filling hose.

          To beat my own horn, I met with some chemists at Hercules in their
          corp hq and when I brought this to their attention, they both had that
          look of putting it together. They made the additives to make tires
          last longer, and within a year were adding other stuffs to reduce the
          potential that would otherwise build up.

          I think if we talk about the engineering, the discussion will be
          easier for everyone.

          Dave
        • Stefan Trethan
          On Sat, 02 Dec 2006 14:39:03 +0100, Dave Mucha ... Some wood dusts are also carcinogenic. Take that you bio people ;-) ST
          Message 4 of 18 , Dec 2 6:05 AM
            On Sat, 02 Dec 2006 14:39:03 +0100, Dave Mucha <dave_mucha@...>
            wrote:

            >
            > From the MSDS of wood: (yes, wood has an MSDS)


            Some wood dusts are also carcinogenic.
            Take that you "bio" people ;-)

            ST
          • lcdpublishing
            Okay, so now we are getting more exact facts to work with... ... If I understand this correctly, in order for an explosion to happen you would need 2 pounds of
            Message 5 of 18 , Dec 2 6:09 AM
              Okay, so now we are getting more exact facts to work with...

              > 1 m^3 = about 35 cu feet.
              > 4" pipe x 900 CFM = 23m^3 per min
              > or about 2 pounds per minute of dust.

              If I understand this correctly, in order for an explosion to happen
              you would need 2 pounds of dust (DUST- not chips) passing through
              the duct work and then an ignition source. There is no machine in a
              home woodworking shop that can generate 2 pounds of dust in one
              minute. I have a 16" wide drum sander that is about as big of a
              sander as you can get (for home use) and it simply cannot generate
              that amount of dust. I would estimate you would have a tough time
              getting that much dust in 15 minutes. I don't even think my planer
              can produce 2 pounds of chips in one minute and those are big
              shavings.

              While it is possible for anything to happen at some point in time, I
              am still not convinced that there would be a dust explosion in any
              duct work used in this manor. I guess it boils down to the old
              saying "I will believe it when I see it".

              Chris





              --- In Electronics_101@yahoogroups.com, "Dave Mucha"
              <dave_mucha@...> wrote:
              >
              > --- In Electronics_101@yahoogroups.com, "lcdpublishing"
              > <lcdpublishing@> wrote:
              > >
              > > The discussion isn't about whether or not dust explosions can
              > > happen - that is well know. The discussion is if it can happen
              in a
              > > dust collection system used in a home woodworking shop.
              > >
              >
              > Chris, et-al,
              >
              > This discussion has little thought behind it. Sorry guys.
              >
              > but if you run anything past anything else, there is a possibility
              of
              > static electricity conformiting. Just a simple fact.
              >
              > Drop water past a ring and a tiny charge will occur. place that
              ring
              > under running water and you get more charge. There is a guy who
              shows
              > how to make a tiny generator by using this property on a waterfall.
              >
              > As for the exhaust system.
              >
              > wood dust (particulate) does have a LEL or Lower Explosive Level.
              > with the proper atmosphere and a source of combustion, fuel and
              > oxygen, you can get an explosion. below the LEL, there is little
              > risk. above it, there is a HUGE risk.
              >
              >
              > From the MSDS of wood: (yes, wood has an MSDS)
              >
              > UNUSUAL FIRE AND EXPLOSION HAZARDS:
              > Depending on moisture content and
              > more importantly, particle diameter,
              > wood dust may explode in the
              > presence of an ignition source.
              > An airborne concentration of
              > 40 grams (40,000 mg) of dust per
              > cubic meter of air is often used as
              > the LEL for wood dust.
              >
              > 1 m^3 = about 35 cu feet.
              > 4" pipe x 900 CFM = 23m^3 per min
              > or about 2 pounds per minute of dust.
              >
              > PVC pipe is a great storage medium for those little charges.
              > Lots of wood dust can create lots of tiny charges
              > pvc is a poor conductor so it does need a drain wire.
              >
              > Like plane crashes, or death by bee stings, they are extremely
              > infrequent. (please no political comments, you can pick any
              analogy,
              > these were not chosen for any particular reason)
              >
              > There is a level of complacency we all achieve.
              > when was the last time you backed up your hard drive ?
              > when was the last time you handled an IC without a static strap on
              > your wrist ?
              >
              > An exhaust duct explosion in a home shop is rare for a few
              reasons.
              > #1) a continuous stream of wood is not present
              > #2) the pipe does not hold the charge well
              > #3) there are few opportunities for a spark
              >
              > A wire on the outside of the pipe is of little use. Using metal for
              > the pipe is the obvious solution, but not as slick as plastic.
              > Drilling and tapping a hole, then screwing in a metal screw would
              > allow the charge to drain to an external wire.
              >
              > Another example; Car tires have become more wear resistant and
              there
              > was a time before they started adding some sort of conductive
              material
              > into the tires when the car would build up a charge and when you
              > exited the car, you would get a shock. There have been many fires
              > from filling a car when that charge encountered the filling hose.
              >
              > To beat my own horn, I met with some chemists at Hercules in their
              > corp hq and when I brought this to their attention, they both had
              that
              > look of putting it together. They made the additives to make tires
              > last longer, and within a year were adding other stuffs to reduce
              the
              > potential that would otherwise build up.
              >
              > I think if we talk about the engineering, the discussion will be
              > easier for everyone.
              >
              > Dave
              >
            • Leon Heller
              ... From: Stefan Trethan To: Sent: Saturday, December 02, 2006 2:05 PM Subject: Re:
              Message 6 of 18 , Dec 2 6:22 AM
                ----- Original Message -----
                From: "Stefan Trethan" <stefan_trethan@...>
                To: <Electronics_101@yahoogroups.com>
                Sent: Saturday, December 02, 2006 2:05 PM
                Subject: Re: [Electronics_101] Re: Flash Fires In PVC Pipes


                > On Sat, 02 Dec 2006 14:39:03 +0100, Dave Mucha <dave_mucha@...>
                > wrote:
                >
                >>
                >> From the MSDS of wood: (yes, wood has an MSDS)
                >
                >
                > Some wood dusts are also carcinogenic.
                > Take that you "bio" people ;-)

                There used to be lots of furniture manufacturers in High Wycombe; there was
                a very high incidence of nasal cancer amongst the workers caused by wood
                dust.

                Leon
              • Stefan Trethan
                On Sat, 02 Dec 2006 15:09:20 +0100, lcdpublishing ... Ok, but there might easily be situations when the dust collects somewhere and then suddenly dislodges. We
                Message 7 of 18 , Dec 2 6:30 AM
                  On Sat, 02 Dec 2006 15:09:20 +0100, lcdpublishing
                  <lcdpublishing@...> wrote:

                  >
                  > If I understand this correctly, in order for an explosion to happen
                  > you would need 2 pounds of dust (DUST- not chips) passing through
                  > the duct work and then an ignition source. There is no machine in a
                  > home woodworking shop that can generate 2 pounds of dust in one
                  > minute.

                  Ok, but there might easily be situations when the dust collects somewhere
                  and then suddenly dislodges.
                  We know it happens only rarely.


                  > I guess it boils down to the old
                  > saying "I will believe it when I see it".

                  If you see it, best don't look too closely ;-)

                  ST
                • lcdpublishing
                  Nah, won t happen here, I have metal ducting. I still have to get to the mythbusters website and ask them to do it. Then I can look VERY CLOSE and still be a
                  Message 8 of 18 , Dec 2 6:58 AM
                    Nah, won't happen here, I have metal ducting. I still have to get
                    to the mythbusters website and ask them to do it. Then I can look
                    VERY CLOSE and still be a safe distance away when I am proven wrong;-
                    )

                    Chris


                    --- In Electronics_101@yahoogroups.com, "Stefan Trethan"
                    <stefan_trethan@...> wrote:
                    >
                    > On Sat, 02 Dec 2006 15:09:20 +0100, lcdpublishing
                    > <lcdpublishing@...> wrote:
                    >
                    > >
                    > > If I understand this correctly, in order for an explosion to
                    happen
                    > > you would need 2 pounds of dust (DUST- not chips) passing through
                    > > the duct work and then an ignition source. There is no machine
                    in a
                    > > home woodworking shop that can generate 2 pounds of dust in one
                    > > minute.
                    >
                    > Ok, but there might easily be situations when the dust collects
                    somewhere
                    > and then suddenly dislodges.
                    > We know it happens only rarely.
                    >
                    >
                    > > I guess it boils down to the old
                    > > saying "I will believe it when I see it".
                    >
                    > If you see it, best don't look too closely ;-)
                    >
                    > ST
                    >
                  • Stefan Trethan
                    On Sat, 02 Dec 2006 15:58:32 +0100, lcdpublishing ... do that! ST
                    Message 9 of 18 , Dec 2 7:14 AM
                      On Sat, 02 Dec 2006 15:58:32 +0100, lcdpublishing
                      <lcdpublishing@...> wrote:

                      > Nah, won't happen here, I have metal ducting. I still have to get
                      > to the mythbusters website and ask them to do it. Then I can look
                      > VERY CLOSE and still be a safe distance away when I am proven wrong;-
                      > )
                      > Chris


                      do that!

                      ST
                    • lcdpublishing
                      Posted the suggestion on their website this morning. It appears as though there are some people without lives that hangout on their forums. We shall see if it
                      Message 10 of 18 , Dec 2 12:49 PM
                        Posted the suggestion on their website this morning. It appears as
                        though there are some people without lives that hangout on their
                        forums. We shall see if it comes up in a future show. I would think
                        so, after all, those guys like blowing stuff up and it makes for
                        good TV so I would think they would jump at the chance. I just hope
                        that Adam doesn't stick the impeller of the dust collector up
                        against his face like he did with the vacuum motors :-)



                        --- In Electronics_101@yahoogroups.com, "Stefan Trethan"
                        <stefan_trethan@...> wrote:
                        >
                        > On Sat, 02 Dec 2006 15:58:32 +0100, lcdpublishing
                        > <lcdpublishing@...> wrote:
                        >
                        > > Nah, won't happen here, I have metal ducting. I still have to
                        get
                        > > to the mythbusters website and ask them to do it. Then I can
                        look
                        > > VERY CLOSE and still be a safe distance away when I am proven
                        wrong;-
                        > > )
                        > > Chris
                        >
                        >
                        > do that!
                        >
                        > ST
                        >
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