Originally Posted by
Jim Dwight
I don't have any experience with DCs of this size but I will comment on metal versus PVC piping. There are myths going around that you have to ground DC piping to prevent an explosion. That is, as I said, a myth. But you cannot get the right dust concentration in a DC and it's piping. So which piping to use is just a cost/convenience thing. PVC is easier to work with and may or may not cost less in 6 inch. But it may be a special order item with 6 inch metal pipe locally available. Personally, I will probably always use PVC. The concern about PVC might or might not affect your decision but I think it should not.
It is true that static electricity relative to PVC duct work will not likely result in an explosion in a home-shop situation. (It's not permitted in commercial shops, however) That said, with more and more electronics moving into shops these days with the popularity of CNC machines and VFD-equipped variable speed gear, one really does have to be concerned with static electricity affecting the machines. My duct work is metal, but I have one foot and a half long piece of PVC to the dust hood of my CNC machine...and it absolutely had to be grounded and grounded really well to avoid it affecting the accuracy of the machine.
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