A mine safety system developed and manufactured in South Africa is reported to be at the center of mining attention worldwide as the first installation undergoes commissioning at a large copper mine in Mongolia.
The system is Horne’s emergency fall arresting system (EFAS), a dual purpose product that delivers a safe stop to a mine cage in free fall, while additionally delivering the standard chairing function needed at mineshaft stations.
EFAS is a radical departure from ‘safety dogs’ and other devices traditionally used to arrest mine cages under emergency conditions. It represents a world first that offers mines the advantage of controlled cage deceleration, and works equally well on both wooden and steed shaft guides.
Safety dogs do not offer controlled deceleration and can only be installed in mines with wooden guides.
At the Mongolian copper mine, Horne engineers have been on site at Number One shaft since early January, testing and calibrating EFAS to ensure that commissioning – which should be complete by the time this issue is in prince – proceeds on schedule.
Guduza System Technologies is also on site at the mine, working alongside Horne as the South African company responsible for EFAS communications with the winder room. This communications line must effectively circumvent the accidental earthing to which a mining installation is prone because of damp. Other cage safety systems have a reputation for accidental earthing and the transmissions of false signals that trip the system. Safety dog communication systems in particular have caused transient signals and tripping on so many occasions that many mines have disabled them, electing to use manual communications instead.
To prevent transients in Mongolia, where ambient temperatures can drop to minus 30 deg C, EFAS has been fitted with special PC boards, and special oils have been used in the system power pack and on all lubrication points.
Concurrent with the commissioning in Mongolia, Horne is proceeding with manufacture of its second EFAS system, ordered by FLSmidth Peru on behalf of mining group Minera Aurifera Retamas SA (MARSA) for the San Andres gold mine.
The MARSA EFAS has been modified to reduce the weight of the externally fitted power pack and align it with the smaller size of the shaft cage. Commissioning is scheduled for May.
“We expect orders for EFAS to accelerate rapidly after both these installations are commissioned,” SAID Horne GM Robb Allman. “Mines work on faith and trust where critical safety systems are concerned, and this is why their management teams are watching the Mongolian and Peruvian installations so closely.”
Horne’s dual function EFAS system utilizes a hydraulic accumulator that operates in combination with Levelok guide clamps (another Horne product) running along the shaft guides.
Under failed rope conditions, a valve on the EFAS hydraulic accumulator automatically opens to force hydraulic fluid under regulated pressure to system clamps, activating them and bringing the cage to a safe halt. The accumulator re-charges to full pressure each time the cage is stopped at a shaft station.