Underground » Detection and Prevention of Fires and Explosions
The aim of this project was twofold. Firstly the aging effect of electronic components used in active power supplies installed in underground coal mines was investigated. This is of concern as the aging characteristics of components could have an influence on the certification of the active power supplies. Secondly the repeatability of testing on different Spark Test Apparatuses was investigated.
The aging effect of components was evaluated through Intrinsic Safety testing of power supplies. Active power supplies, used on equipment underground were supplied by some mines for testing. Power supplies, of the same type and specification were purchased from the manufacturers. The "new" power supplies were tested and then supplied to the mines for fitting to the equipment, if need be. The "old" power supplies were then tested to the same process as was applied to the "new" power supplies. A suite of load circuits was developed to connect to the power supplies during testing.
Repeatability of Spark Test Apparatus testing was evaluated using three different Spark Test Apparatuses. The Spark Test Apparatuses were from three suppliers. All three were setup to the electrical and mechanical parameters as specified in the standard, "IEC 60070-11 Explosive atmospheres - Equipment protection by intrinsic safety "I"" Annex B.
Results for testing of "new" and "old" power supplies were the same. Therefore, the power supply testing did not identify any aging effect of components. In the majority of the testing the three Spark Test Apparatuses returned the same outcome. However, the results differed for the Spark Test Apparatuses for some of the load circuits. Repeated testing of these circuits would alternate the testing between pass and fail, which confirms the statistical nature associated with the Spark Test Apparatus and lead to ongoing work to develop a reliable and repeatable spark testing device.