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Electrical safety barrier, Measuring device, Voltage rectifier, Enclosure, Human machine interface
Text version of the page
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| An example: Moulded materials in the pipes of pneumatic conveyor systems initially receives a strong electrostatic charge from friction on the inside. This charge produces an influence-charge on the external surface, which is coated with plastic material and covered dust. This double layer of charge may contain large amounts of energy. If one short-circuits both sides of the doubly charged layer, all the stored energy is violently discharged. This causes brightly lit discharge channels to form on the surface of the plastic material. This discharge may contain several joules of energy, so that nearly all gases and vapours and the majority of dusts will be ignited. However, propagating brush discharges are relatively rare in practice. The following measures can prevent this type of discharge process such as these: > Adjusting the surface resistance to 109 Q and grounding the plastic material. > Limiting the breakdown voltage of the non-conductive material to 4kV. > Avoiding thicknesses < 8mm for the non-conductive material. > Limiting isolated capacities to < 10pF. > Increasing humidity to >65% in order to reduce the insulation resistance of non-conductive materials. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Table 11: Summary of the Requirements for Rotating Electrical Machines, Type of Protection "tD" | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| R.STAHL Explosion protection | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||