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Question I have a customer with a severe static problem. They have polyesterfibre being blown into furniture cushions. The fibre comes out of a three inch tube into a cloth cushion, as the operator holds the cushion over the opening the material entering the bag is creating a shock to the operator. They have tried numerous things to eliminate this problem, including wrist straps, earth ground rods that are attached to the equipment, and many other things. I am looking for your recommendation as to the best way to attack this problem. I have a list of the things that they have tried in the past, and they are sending me some digital pictures of the area that I can send to you. They have ESD mats that were purchased in the past, that were grounded. But they never had the operators wearing heel straps, so that didn't work. If you could call me on my cell phone I can give you more info. 216-276-2880. They are also looking for a way of measuring the static in the air.
Answer This is an industrial ESD control problem. What is happening is very similar to how a Van de Graaff generator works: An electrostatic generator in which an electric charge is either removed from or transferred to a large hollow spherical electrode by a rapidly moving belt, accelerating particles to energies of about ten million electron volts. [After Robert Jemison Van de Graaff (1901-1967), American physicist.] There are two ways to reduce the probability of the operator getting an electric shock: (Q1) control all charging operations (Q2) remove all conductors and float the system
(A1) to control the charging operations, you'll need to ground all conductors (tube, operators, work area, etc.) and properly ionize all insulators (polyester fiber and furniture cushions). Depending on the material flow rate, ionization may not work optimally, even when enhanced with humidification. Another thought might be to pre-treat the fiber and cushions with our Reztore™ topical antistatic solution which will provide charging relief during this operation.
(A2) The other solution would be to float the entire operation knowing that charging will occur. By floating everything, there will never be a big enough potential difference to cause a discharge. You'll have to replace all metal parts with high dissipative or insulative parts, not employ grounding, possibly put down an insulative floor pad. You are essential creating a high voltage working area, like that used for working on high voltage equipment (TV's, Monitors, Implanters, research, etc.). The risky part is once the bag is filled and the operator leaves this isolation area, he/she runs the risk of either touching a metal surface and creating an ESD event or coming into contact with a conductor at a different potential and generating an ESD event (electrostatic shock).
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