Considerations regarding the main factors influencing the occurrence of pressure pilings in electric motors for use with flameproof enclosure in potentially explosive atmospheres of gases and vapors

The purpose of the paper is to perform a critical analysis of the main factors which lead to pressure pilling in the case of flameproof electrical motors designed to be used in potentially explosive atmospheres of group II of gases and vapors and which should be considered in the design stage of flameproof enclosures of electric motors in order to pass the non transmission of an internal explosion test, successfully. The researches conducted in the specialized Laboratory of INSEMEX Petrosani, on a very large number of flameproof motor samples have led to the conclusion that the pressure pilling phenomenon is the main reason for the transmission of an internal explosion in the case of self ventilated electrical motors. The term pressure pilling, as used in this report, refers to the increase in pressure in a compartmented enclosure, above the pressures that would occur in the same compartment without compartmentation. This pressure increase is a relative measure and may be considered abnormal compared to the pressure obtained in a constant volume combustion process with a precombustion gas pressure at or very near standard atmospheric pressure.