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Thread: Shocking! (DC)

  1. #1
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    Shocking! (DC)

    My dust collector is giving me some pretty big static shocks. It is installed in another room and is piped in with 3" PVC to a flex hose that I connect to each machine as needed. The 2 1/2" hose is plastic with no wire in it. No problem if connected to a machine or when used for light cleanup, I think because it drains off pretty quickly. But if I pull any amount of sawdust from a machine I get some cracking shocks. Much worse in the dry winter air. Any suggestions to reduce this would be appreciated. Here's a sideways picture of the hose. DC Hose.jpg

  2. #2
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    Hi Tom, I had the same issue with a piece of 4" plastic hose.

    That's the issue with non conductive hose and pipe.

    Perhaps you could try a piece of flex with wire and ground the wire?

    If not buy a length of conductive hose, and ground the hose............Rod.

  3. #3
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    It's amazing the kind of shock you can get from plastic and rubber. I was working on a high rise on the top floor when an iron worker comes up to me to tell me the temporary fall protection cabling around the rooftop was live. To get to it I had to walk over rubber roof membrane. There was steel angle iron acting as posts and they were welded to building steel. No way the steel cable attached to the angle iron could be hot but the iron worker swore to it. They he touched the cable and I heard a loud crack. He looked at me and said, "See! I told you it was hot." Of course, it was just static electricity, but it hurt.

    Tom, you need to drain off the static. Try attaching grounded bare copper wire the hose and experiment which place works best to drain off the static.
    Last edited by Julie Moriarty; 01-02-2019 at 5:35 PM.
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  4. #4
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    I have the same problem with mine and if I am sanding. It's a major problem for me as the static shock could potentially damage my cochlear implant. Thus I wear a ESDC grounding strap on a wrist band and the grounding strap is attached to the metal pipe for my DC.

    It's not a problem with it attached to my TS, BS or any other big tools that are grounded.
    Ken

  5. #5
    I used to have the same problem when my 4" pvc was new. After a short time of use, the static problem went away. Now the plastic won't even raise the hair on your arm.
    Lee Schierer
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  6. #6
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    Spiral wrap the hose with the smallest wire you can find and ground it at one end. The wire does not have to be inside the air stream. Old speaker wire, lamp cord, old ,ear buds. Should not matter if it is insulated or not?
    Bill D

  7. #7
    I find most companies that sell DC flex have the plastic support cord and you can buy it by the foot. Leavalley sells A more flexible hose with a wire in it. The hose is only 10 feet long. All my duct work is metalSo I just leave a little bit of exposed wire in the flex to get my grounding. It looks like you’re using ABS/PVC. Usually if you just run a little wire and attach it to copper plumbing you will greatly reduce the static. To reduce the static in the ABS/PVC, just run a strip of aluminum duct tape the length of the pipe. Around each end just do one wrap and it doesn’t need to look pretty, but needs to be grounded too.
    Last edited by Matt Mattingley; 01-02-2019 at 11:55 PM.

  8. #8
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    So the electrons are picked up (or shed) by the sawdust as it moves thru the hose and pipe. The end of the hose I'm holding is transferring them to me and I'm storing them up and zapping them to the machines when I touch them. If I ground myself by holding onto the machine the static charge is still zapping me from the hose where it builds up. Not sure why it doesn't bleed off thru me continuously instead of building and zapping, but that's what's happening. I wrapped a grounded wire around the hose at the connection to the pipe but that didn't make any noticeable difference. I'm trying to not have to replace the hose.

    If I ground the last few feet of my 25 foot hose it should protect me?

    Not quite sure how to do that. The hose gets dragged around the shop so adding a wire on the outside would be difficult. Wire on the inside would get in trouble with the sawdust.

    Would a capacitor on the end of the hose hold the charge? It could be connected to a wire wrapped back along the hose for a couple of feet.

  9. #9
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    Quote Originally Posted by Tom Bender View Post
    If I ground the last few feet of my 25 foot hose it should protect me?
    Probably but not necessarily completely. Plastic hose is not a good conductor. Electricity follows the path of least resistance. It's impossible to say for sure what path the static is taking. If it's really bad, there are grounding wrist bands worn by those who work on circuit boards and such. Using one would require you to attach the ground wire to whatever you're touching to give you a shock. Not really a practical solution.

    You could tape a bare copper wire along the length of the hose and see how that works. You could replace the hose with anti-static dust collection hose and ground one end. Your picture shows the flex hose is connected to PCV pipe. There's probably static charge building up in that pipe, too. The more places you install charge dissipating conductors, the less charge should be transferred to you. Experiment!
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  10. #10
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    Thanks Julie, I will.

  11. #11
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    Pretty sure I have some sort of super-conductor in my DNA, any static within a mile and I'll get shocked. I use anti-static hoses, have everything thoroughly grounded and still get shocked in the winter time when the air is super dry. I fashioned a "stirrup" out of aluminum foil. Wraps under my shoe, tucks in along the sides, held in place by my foot. I have noticed some of my footwear facilitates greater shocks, more insulated from the ground I suppose.

  12. #12
    Quote Originally Posted by Tom Bender View Post
    Not sure why it doesn't bleed off thru me continuously instead of building and zapping, but that's what's happening.
    The hose is plastic (an insulator), surrounded by air (an insulator), but as soon as a sufficiently large static charge builds up, the electric field is strong enough to break down the air's insulating ability, forming an arc which allows the stored charge to flow from some region on the hose to ground.

    Don't think of the hose as a single insulator. It's a bunch of little charge-building regions separated by insulators which connect together at various times depending on how strong the stored charge is.

    Adding a grounded wire doesn't "ground" the hose, but instead of allowing a giant charge to build up, it provides a shorter path that will be taken once a smaller charge builds up. Also, that path isn't through you

    Basically, reducing static zaps is just a process of minimizing how much distance there is between any bit of plastic and a ground wire/connection. A hose with a built-in wire has, maybe, 0.5" max distance between any plastic surface and the metal wire. Running a bare wire around the length of a full-plastic probably gives you a max distance of ~4".

  13. #13
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    Not sure it is useful in DC, but static charge tends to like pointed conductors. Lightening rods are pointy on top. Static brushes in printers are a large number of pointed conductors (conductive fibers).

    If you can find a static brush from an old printer or something it might be interesting to play with.

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