Methane gas detectors accuracy and response times under varying gas flow and sensor occlusion conditions

Accurate and timely detection of methane gas levels in underground coal mines is crucial in the prevention of gas explosions. Yet, the nature of the mine environment with its high humidity and dust can cause the gas detectors to become occluded with a buildup of dust over time. These occlusions have the potential to compromise the accuracy and/or response time of gas readings in real time.

The accuracy and response times of fixed gas detectors are validated in typical mining operations with known gas mixtures and gas flow rates during commissioning, and at regular maintenance intervals. Original Equipment Manufacturer (OEM) calibration cups are used to allow the calibration gas to flow into the detector while minimising environmental disturbances.

Simtars has undertaken a comprehensive series of tests to evaluate the effects of occlusion on the accuracy and response times of real time methane detectors. Tests were conducted using both OEM calibration cups and purpose-built Simtars test calibration cups. The influence of various levels of occlusion on the gas detector accuracy and response time was assessed.

This paper presents the outcomes of this study, comparing the accuracy and response times of seven methane gas detectors currently in use in Australian mines. Simulated occlusions were carried out with occlusion percentages of 65 %, 80 %, 90 % and 95 % using three methane concentrations of 0.5 %, 1.5 % and 2.5 % for each occlusion percentage.

The results demonstrated significant variability under varying test conditions. Recommendations to improve gas detector validation, calibration, and performance assessment based on the test outcomes are presented.