EXPLOSION TESTING OF RELIEF VALVES FOR UNDERGROUND REFUGE ALTERNATIVES

Federal regulations require refuge alternatives (RAs) to be installed in underground coal mines. RAs provide miners safe shelter from life-threatening environments during a mine emergency when escape is not possible. Built-in-place (BIP) RAs require ventilation systems that supply breathable air to occupants. Relief valves provide critical functions to the ventilation system by limiting pressure within the RA, allowing ventilation air to exit while preventing contamination ingress, and protecting occupants from external pressure due to mine explosions. As such, relief valves for BIP RAs must be developed and tested to ensure pressure relief, adequate airflow, and the ability to withstand a 103-kPa (15-psi) blast overpressure with a duration of 0.2 seconds. The National Institute for Occupational Safety and Health (NIOSH) has published research on relief valve opening pressures and airflow rates. However, the ability of RA relief valves to withstand a survivable mine explosion must be demonstrated. As such, NIOSH researchers tested the ability of RA relief valves to withstand overpressure representative of a survivable mine explosion. For this, seven relief valves were subjected to 103-kPa (15-psi) target overpressure waveforms, produced using methane-air explosions within a fixed-volume enclosure. All seven relief valves survived the overpressure testing, maintained normal performance, and did not incur any critical component deformation. One instance of valve leakage was observed during the tests. This paper presents the methodology and results of testing the ability of RA relief valves to withstand a survivable mine explosion. Information in this publication can be used for evaluating relief valve design and determining parameters critical to their ability to reliably withstand a survivable mine explosion and protect RA occupants. Research presented in this paper is applicable to testing and improving RA designs for underground coal mines, and could also be extended to similar applications and industries involving explosion testing.