Abstract
The following three experiments were carried out to determine the safety limit for negatively charged polyester working wear. (1) Through the estimation of muximum (absolute value) voltage causing no discharge by a single contact with a grounded needle electrode, the limiting charged voltage of -3.5kV was obtained as a mean value. The safety limit calculated by adding the doubled standard devition to the mean value was -2.0kV. (2) By measuring the residual voltage on charged fabric after the multiple contacts (scanning) with a grounded sharp electrode, the safety limit causing no discharge was determined to be -2.0kV. (3) From the relation between discharge-initiating voltage of a metallic plate facing a grounded sharp electrode and the distance between these two electrodes, the discharge-initiating voltage at zero-distance was estimated to be -2.0kV in negative static field and 1.4kV in positive field. Considering the above mentioned results, the authors conclude that the salty limit for negatively charged working wear is -2.0kV. This safety limit is effective to avoid static hazards caused by discharges between fabrics and a sharp tip of metallic materials.
