patrick_g
Elite Member
Isn't it great when you learn something even when you aren't trying!
I once built a dust collector for my wood shop. It used a plastic garbage can for a reciever and I built a cyclonic seperator mostly out of wood. I piped it with plastic pipe and powered it with a large shop vac moter and filter. I was very proud of the results, it extended my run times between shop vac filter changing about 10 times.
When it was running if you put your hand on the plastic tube it would make your hair stand on end. If you touched the cast iron top of the table saw at the same time it would make your eyes roll back in your head.
It was a dust explosion looking for a place to happen. I installed copper ground wires and bonded everything together anf the problem went away.
It gave me a great appreciation of what static electricity can do and where it comes from.
In my profession as a mechanical designer in chemical and nuclear power plants I always insured that everything was bonded and grounded but I actually didn't appreciate why until my dust collector project. If a little fractional horsepower motor in a shop vac can move enough material to build up a charge like that can you imagine what a 100 hp motor with miles of pipe or ductwork could do? Without bonds and grounds stuff would be blowing up every day!!!
Steve, I have the Oneida Dust Gorilla with a 3 HP motor. All the fixed ductwork is steel. I use flex tubes from the blast gates at the drops to the machines. NO electrostatic accumulation or explosion hazard in this part.
When I stand close to my thickness planer's output flex hose it makes hair stand on end, on your arm if that is close to it or on your head if that gets close even when the relative humidity is pretty high. It generates quite a lot of static electricity but as the plastic flex ducts all feed grounded metal ducts the charge easily bleeds off to ground. The machines themselves are grounded so no nasty surprises when touching one.
There is a spiral of wire embedded in the flex duct and it is grounded to the planer but the wire is not directly exposed to the flow of debris. Before experiencing this setup in action I would have bet that the grounded wire in the flex duct would have prevented any major static production BUT I WOULD HAVE LOST THE BET!
When I was much younger I used to build static generators such as the Van de Graff electrostatic generator but never got as much output as a branch of my dust collection system sucking up chips and dust.
Done with humor or otherwise, scoffing at the inherent danger of fueling operations (whistling in the dark ) serves no beneficial purpose. I have been handling gasoline for over 50 years and never had a problem but that doesn't mean their is no danger. When I was in high school some boys were "liberating" what we called "drip gas" from some oil field plumbing and all were burned. Static electricity was the likely culprit as they were not smokers.
Pat
