Evaluating the Performance of Fire-Resistant Hydraulic Fluids in Underground Potash Mines

Conventional underground potash mines use boring machines to extract potash 1 km below the surface. The boring machines are largely powered by hydraulics using mineral fluid. Although this fluid works well it is flammable and can catch on fire if it sprays from a failed hose onto the hot equipment. A fire in an underground potash mine is a major safety concern due to the fire not only destroying equipment, but also the smoke limiting fresh air supply for all workers underground. Switching to a fire-resistant hydraulic fluid (FRHF), in place of the flammable mineral fluid, could prevent fires in potash mines. The concern with switching to an FRHF was the ability of the fluid to be reliable with the ever-present potash contamination in the system, due to the confined environment. In previous research, potash contamination caused excessive wear in hydraulic pumps using water-based FRHFs so proper testing was needed to test new synthetic FRHFs that are on the market today. The testing used a large test bench with four identical hydraulic circuits for the currently used mineral fluid to be compared side-by-side to three synthetic FRHFs. Tests with no potash contamination, ideal potash contamination and maximum potash contamination seen currently in the mines were complete. Each test was run for 200 hours. Throughout testing fluid samples and pump performance tests were complete. Post testing wear loss, filter analysis, volumetric efficiency, mechanical power and fluid power calculations were complete. The majority of the tests and analysis ranked a fire-resistant hydraulic fluid higher than the currently used mineral fluid. This type of outcome was not possible when fire-resistant hydraulic fluid was tested previously with potash contamination. Two of the fire-resistant hydraulic fluids showed less wear to the pump and other hydraulic components and gave competitive performance and efficiency values. The fluid samples and filter analysis also showed a replication of the conditions of the underground potash mine in the test bench. These results were the objective for this research and show promise in making the underground potash mines safer by switching to a fire-resistant hydraulic fluid possible