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Equipment Maintenance - Mining

Sandy Dunn

November 26,2001

Best Practice Maintenance Strategies for Mobile Equipment


A Conference Paper presented to the Maintenance in Mining Conference - Bali, Indonesia

By Sandy Dunn

March 1997

Obtaining Step Change in Equipment Performance Levels
To date, RCM2 has been successfully applied to large mobile plant in at least four large Australian minesites in the Iron Ore and Coal industries. The items of plant covered includes Production Drills, Haul Trucks and large Electric Shovels.
Example 1 - Haul Truck
In one case study at a large coal mine, RCM2 was applied to a large haul truck from one of the major manufacturers. At the time that the study was undertaken, the engine in the truck was subject to a routine major overhaul every 12,000 operating hours.
Detailed RCM analysis, which included consideration of almost 500 failure modes for the engine, found that there was no failure mode for which the most appropriate preventive task was a routine overhaul, at 12,000 hours or at any other frequency. Condition Monitoring, including oil analysis and visual inspections and adjustments, was to be used instead to predict when the engine required major overhaul.

Incidentally, a similar move to Condition-Based Maintenance by the Barrick Goldstrike Mine in Nevada extended the average time between major overhauls for Caterpillar 16G Grader Engines from the "required" 12,000 hours to almost 18,000 operating hours.

Example 2 - Production Drill
RCM2 was applied to a production drill at a large Iron Ore mine. At the second team meeting, the team determined that the main air compressor on the drill had three levels of protection built in - an exhaust air over-temperature trip, a high cooling water temperature trip, and a low cooling water level trip. The mine was based in North Western Australia, where ambient air temperatures were generally very high. According to the team members, the exhaust air temperature was almost always within 2 or 3 degrees of its trip point. However, the cooling water temperature was always well below its trip point. The group determined that the normal sequence for an over-temperature trip was that the compressor would always trip on the high exhaust temperature trip. Only if this trip was not working, would the compressor trip on high cooling water temperature. Only if both of these trips were not working, would the compressor trip on low cooling water level, however this was seen to be a very unlikely event.
While performing this investigation, the compressor tripped on the low cooling water level trip. Visual inspection showed the cooling water system to be full of coolant - the trip had been a spurious one. An inspection of the log books showed that this spurious trip was a frequent cause of machine unreliability. The group came to the conclusion that the low cooling water level trip was unnecessary, and should be removed, but before doing so, checked with the equipment manufacturer to make sure they had not missed some vital fact. The manufacturer informed them that the low cooling water level trip had originally been installed for their machines that operated in sub-zero temperature conditions, where the coolant could, potentially, freeze, causing the radiators and hoses to burst. Under these conditions, the low cooling water level trip would be the first to activate. But the manufacturer’s view was that this trip was totally redundant and unnecessary for equipment operating at high ambient temperatures.

The low cooling water level trips were removed from the production drills, and significant improvements in equipment reliability were obtained, together with some reduction in maintenance costs.