Benchmarks #5

Maintenance Ratio

Maintenance Ratio (MR) is another benchmark that many mining operations are beginning to use.

Maintenance ratio is used both as an indicator and as a planning tool. MR is calculated by the following method:

MR (hours) = Maintenance Man-hours / Machine Operating Hours

MR can be tracked over time to provide a workshop and manpower efficiency indicator. It can also be used by the Maintenance Department to plan manpower and budgets. When Production makes its upcoming operational plans known to Maintenance, Maintenance can determine the manpower resources it must have to care for the equipment during that period.

To be useful as a budgeting figure MR needs to be measured for each family of machines, (i.e. trucks, bulldozers, motor graders, etc.) as each has different maintenance requirements. In addition, MR changes with time, just as the repair and maintenance requirements for equipment change with time. This means that MR data must be analyzed relative to the equipment life cycle. Mines that are tracking MR report that for trucks and wheel-loaders (in loader / truck applications) the MR can be as low as 0.25 to 0.30 maintenance man-hours per operating hour. This figure applies to fleets that are old enough to have begun the component replacement or reconditioning cycle. This number represents only on-site maintenance and repair activity. Component repair or reconditioning, typically done off-site, is not included.

On relatively new machines (those that have not yet reached the age when components are being reconditioned) the MR number is lower. However, once components are being replaced, the MR number will increase and then remain essentially constant.

... to be continued.