static electricity

[jtb]

Not sure if this belongs here, but I have a customer who installed a length of PVC pipe in a dust collector return. Majority of system originally installed with metallic duct, they just extended it, and want to keep the non-metallic for flexibilty. I haven't seen it, it may even be that flex hose. Now static builds up on the pipe and shocks the operators (no more sleeping on the job!). I am looking for a quick and dirty solution, like foil tape or something. Any suggestions? Thanx

 

[mikeackley]

Re: static electricity

The way I've seen this static problem addressed before is to fish a bare copper wire inside the full length of the plastic pipe, connecting it (the copper wire) securely to the metal duct. Assuming the metal ducting is grounded, this should bleed off any static electricity. Grounding kit accessories are quite often available from the manufacturer/distributor of the primary dust collection system.

I'm not aware of any NEC issues here; however the dust particles inside the ducting could create a highly inflammable environment so depending upon the building class, environment, use and so on, local building, mechanical, and/or fire codes may be involved.

[ March 06, 2003, 04:37 PM: Message edited by: mikeackley ]

 

[nosparks]

Re: static electricity


Just to reiterate with Mike. I agree that the copper bonding jumper is the way to go. I am taking a facilities managment course and this is an issue that the instructor emphasized. Keeping objects at the same potential is the key. Another approach either separatly or to augment the bonding jumper would be to lay down anti static mats in the work area, (and or) look into bonding bracelets for the personnel. Please let me know your results, as I have not had the opportunity to test these methods. Good luck

 

[Len_B]

Re: static electricity

There is a possible problem with dust and/or foreign objects catching or building up on an internally routed bonding wire. This depends greatly upon the material being conveyed, particle size, moisture content, possibility of foreign objects like rags, etc. If the plastic section is easily cleanable or able to be disassembled easily this method may be okay, provided the materials being conveyed are not classified as hazardous. If this is a Class 2 area, or the materials are hazardous, I would look for a flex duct rated for static dissipation and run an external bonding wire.

Links to some suppliers of flex duct:
www.pneumaticconveyors.net
www.texveyor.com
www.hapman.com
www.semcotbs.com
www.conveyor-center.com
www.centralstateshose.com

PS --- make sure collection drum, dumpster or other final collection container is also bonded to this ductwork, and that any operator or access platforms are bonded to this same system.

Len