Benchmarks #1

Many mines try to determine maintenance management system effectiveness by utilizing “benchmarks”. Benchmarks are essentially targets or objectives but the current trend is to use numerical benchmarks that are actual measurements or calculations based upon collected data. Benchmarks are frequently used to evaluate performance trends internally but they are also used to make comparisons with other mines. The number of benchmarks in general use has been growing dramatically in the past several years and many mines are using the same or very similar benchmarks. It is logical to use industry benchmarks rather than opinion or other subjective devices when evaluating performance or when comparing one mine with another. Each mine may be unique (in many respects) but most are involved in the same tasks and are looking for results measured in a consistent manner. Performance relative to various benchmarks will be different (depending upon circumstances) but the benchmarks themselves should be uniform.

Mechanical Availability

Mechanical availability (MA) has been a benchmark in the mining industry for a long time. Notwithstanding, there are some drawbacks to mechanical availability which limit how useful or informative it can be. These limitations make MA into more of an “indicator” rather than a true “measure” (or benchmark). The first limitation arises because several different methods and formulas for calculating MA have been developed. As a result MA works better as an internal benchmark (where the calculation method will be known and consistent) than as a comparison between mines (where the formulas may differ). The second, and more important limitation, is that MA is not very informative by itself. It tells us the relationship between two factors, but that is not very useful without having some additional detailed information about those two factors.

Both the Production Department and the Maintenance Department use mechanical availability but it means different things to each. How Production uses MA follows immediately. How Maintenance uses MA follows the sections on MTBS and MTTR.

Mechanical Availability and Production -- Mechanical availability is used by Production to establish the ratio between two factors; operational hours (hours of actual machine usage), and downtime hours (when the machine cannot be used for “mechanical” reasons). Production has routines in place to collect the required data for measuring these two factors.

Mechanical availability is often calculated by the following method:

MA% = [Operated Hours / Operated Hours + Downtime Hours] X 100

An operation develops production estimates based upon some expectation of MA so they use this calculation to see if the expected availability is being achieved. If it is not, production will fall below estimates. As pointed out above, MA is just an indicator of a problem. To know what action is required in response to a change in availability, we would have to analyze the data on operated hours and downtime hours.

Two more recently adopted benchmarks that are proving to be valuable indicators of performance are “Mean Time Between Stoppages” and “Mean Time To Repair”.

... to be continued.