Explosive atmosphere ignition source identification during mining plant suspended monorail braking unit operation

摘要

Coal dust and methane explosions are some of the most common causes of mining disasters in hard coal mines all over the world, and research continues to be conducted with the purpose of understanding the mechanisms of an explosion, explosion prevention and risk reduction. This article presents the test methodology as well as virtual and bench test results for a braking unit, which constitutes one of the main components of a suspended monorail transport system. The design work and virtual and bench testing were performed as part of a European research programme. The tests were conducted in a dedicated specialist test facility. The tests were based on Polish standard PN-G-46860:2011, concerning braking trolleys employed in mining plant suspended railway systems. The tests also factored in the requirements for non-electrical devices intended for use in explosive atmospheres, including braking systems, as defined in standard PN-EN ISO 80079-36:2016, harmonised with the ATEX directive. The test scope encompassed braking unit operational component temperature measurements using thermal imaging and the contact method, as well as braking distance measurements. Further tests involved virtual simulations of brake pad heating. The tests employed the finite element method (time-varying calculations). Results obtained over the course of numerical calculations indicate that brief brake pad friction face heating, even up to a temperature exceeding 200?C, does not result in inward heat propagation towards the brake pad material. This is also confirmed by the measurement results. However, under real conditions, the braking unit would be engaged only during an emergency situation, which would not lead to exceeding the permissible brake shoe material temperature values.