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SAFETY
Other suppliers that offer mine refuge systems include Rana Mine Refuge Systems in Canada, and U.S.-based Strata Safety Products and Mining Health and Safety Solutions. Rana's Tommyknocker is a portable, completely self-sustaining refuge chamber that maintains a controlled positive pressure level inside to keep dangerous gases from entering. Available in various sizes to take up to 20 people, its features include a double door airlock entry system, emer- gency battery back-up power, seating and bench storage space, and a self-con- tained toilet system, together with options such as air-conditioning, a gas monitor, a carbon monoxide scrubber and other custom add-ons. The Tommyknocker uses Rana's Re- fuge One Breathable Air Center to main- tain safe breathable air levels for emer- gency durations of up to 96 hours. These centers remove carbon dioxide from the sealed chamber air and replenish oxygen to maintain safe breathable air levels. They run independently on mine electrical power, and have an emergency battery back-up. The number of centers required and the quantities of batteries, chemical
and oxygen depend on the size of the refuge station, the number of people it is designed to accommodate, and the time- span for which protection is designed. Designed for handling with a regular industrial forklift, the standard Tommy- knocker measures 4.3 m (14 ft.) by 2.2 m (88 in.) and weighs nearly 2 mt. The personnel compartment measures 3 m (10 ft.) long, with the double-door air- lock taking up the remaining length. This size will accommodate ten people, Rana says, with greater capacity being gained by adding 610-mm (2-ft) sec- tions to the length.
Keeping Watch on the Air Providing refuges for use in emergencies is just one aspect of evolving safety practice. There is also an increasing reliance on indi- viduals being able to monitor the air around them, using small belt- or harness- worn detectors that can give an immediate warning should toxic gases appear. As the German gas-detection equip- ment manufacturer, Dräger, points out, gases that occur naturally or are generat- ed during mining remain a major hazard and continue to place miners at risk of
poisoning through toxic gas exposure, or suffocation because of oxygen deficiency. Since toxic or combustible gases can be colorless and odorless, and reduced oxygen levels are invisible, measurement and environmental control are needed to make sure that these potential dangers are recognized in time. Dräger's product range includes a comprehensive line of gas-detection pro- ducts for personal air monitoring and workplace exposure monitoring, both in day-to-day mining operations and during mine rescues. Fitted with the new CatEx 125 PR sensor, which is three-to-five
times more resistant to silicone and H2S poisoning than other portable gas detec- tors, its X-am 5000 is perfectly suited for mining applications, the company says. The unit's different sensors can be cus- tomized, allowing this one-to-five-gas detector to measure combustible gases and vapors as well as oxygen and harmful
concentrations of CO, H2S, CO2, HCN, NH3, NO2 and SO2 that are common to hard-rock mining.
Dräger says it recently developed a
new nitrogen dioxide (NO2) sensor to improve the ambient air monitoring of
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FEBRUARY 2012 • E&MJ; 45
