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Controlled grounding for maximum safety when handling fire and explosive materials.
Ground monitoring systems make sure that existing ground contactors (e. g. ground clamps) are actually used when filling or discharging potentially explosive materials from tanker wagons and silos. Since filling or discharging can only be started after the proper ground link has been identified, this system provides the ultimate degree of safety.
Electrostatic charges when handling liquids, granulates and powders
Filling and emptying tanks with liquids, granulates and powders and pumping, stirring, mixing or spraying liquids as well as measuring and taking samples or cleaning tasks: All of these processes can cause a dangerous build-up of charge in liquids, granulates and powders or the insides of containers.
The resulting amount and size of the charge depend on several factors. These include the properties of the media and their flow rate, the respective operating method as well as the size, geometry and material composition of the container.
When handling highly inflammable materials, uncontrolled static discharges are a hazard which must not be underestimated. It can cause explosions, fires and secondary accidents due to the effects of static shock. Controlled grounding is a safe and easy measure for rotecting people, production facilities and transport machines. Grounding with static monitoring systems is particularly helpful in the following applications:
A static high voltage is essentially “trapped” on an insulator (such as plastic film), because there is no electrically conductive path to relieve it. Discharging the wrong way means that something “physical” spontaneously becomes that conductive path – and current flows through it to neutralize the charge. A worker accidentally becomes the discharge path for static on a plastic film web and “gets zapped.” Or, the film discharges against a part of the machinery.
Discharging the right way eliminates charges immediately after they develop. The charged material is exposed to antistatic bars that fill the air with ions carrying positive or negative charges. These ions safely neutralize the static charge on the material, preventing hazardous spontaneous discharges.
The most frequent form of undesirable charging is contact charging. It mainly involves two material bodies whose boundary layers are in contact with each other – in our example, the surfaces of a film web. High-speed unwinding causes the film surfaces to separate at very high speed, with the process described on the previous page setting in. The result: the plastic film charges up.
The currents developed during this process may be almost negligible, but the voltages may be several million high. Even if there is only a split-second between contact and separation, relaxation (i.e. charge decay) may take days. One thing is certain, however: discharging is necessary.