static charge

It's not possible to eliminate them completely, however, slowing down the rate of arrival of the powder into the bag can help reduce the chances of it being there and its intensity. The rule-of-thumb for non-conducting liquids is to keep the pipe velocity below 1m/s.

Many believe that static can be eliminated by introducing an earthed metal rod into the medium, and wonder why they get fires and explosions. Isn't that how a lightning conductor works?

Static charges can be a very serious problem. Generally a static charge is no greater than 0.1mA. If it's allowed to accumulate, it can reach a very high potential of 30kV. Proper grounding and bonding is imperative in having a safe process where this danger exists.

The Newson-Gale co. is a good source of info on static dissipative equipment. Also, if you have access to it, see the NFPA 77 "Recommended Practic of Static Electricity"

Hope this is of some assistance.

http://www.newson-gale.com/