Static Shock From Burr King Model 760by James Krier
Low Humidity Levels Direct Cause
Low humidity levels especially during the winter months lead owners of Burr King grinders to search out ways to reduce the static shock that may build up while running the equipment. This is not just isolated to Burr King equipment. We have several first hand experiences with belt sanders and other rotating equipment that will produce a healthy static shock. A static shock could range anywhere from 1,000 volts to 500,000 volts but only 5 milli amps or 5/1000 of one amp. It takes 20,000 volts to jump 1/4 of an inch during ideal condtions. First we must understand why the shock is occurring to better reduce the likelihood of being shocked.
The abrasive belt being used
is made of a non-conductive material. The wheels are made with a urethane
material on the outer edge of the aluminum that also may act as an insulator.
Then we move on to the bearing that are filled with oil and grease. Add to this that the operator may be grinding
aluminum with leather gloves on and wearing shoes that have non-conductive
rubber soles. These factors make it
tough for the static charge to dissipate to the natural ground of the machine
and the added resistance will allow the charge to build higher until the path
of least resistance is found.
We have performed many different tests to find ways of discharging the static charge. Currently all idler wheels that are used in the production of the 760 are covered with urethane that has a special electrostatic discharge material incorporated in the urethane. This solves many of the customers problems with static. However, if needed, a non-urethane covered idler wheel maybe installed on the 760. The 707 all aluminum idler wheel is available as a replacement part. The wheel will not have the same life span as an urethane covered 707EX. The life of the wheel maybe shortened 30% or more.
A ground strap maybe the quickest and easiest option for most customers. The copper strap should run near the backside of the abrasive belt without touching it directly. This will allow the static charge that is being isolated in the abrasive belt to be discharged. When installing the copper strap, it is best to run a copper wire from the ground strap to the ground of the machine.
Many Burr King customers have also found grounding devices that are worn around the ankle or wrist and connected to a good ground also produce very favorable results. The conclusion for any of the above methods is to incorporate a path for the static charge to flow throw that has very little resistance.
If you need more assistance or have any questions please contact Burr King Customer Service at 800-621-2748. We will be more then happy to assist you.