Who at your operation has the final word when it comes to idling a piece of equipment for maintenance, the maintenance manager or the operations manager? Typically, how their performance is evaluated places them in competition with one another. Measuring a maintenance department's performance using only equipment availability could lead to an inaccurate evaluation. A Maintenance Efficiency Factor (see Rock Products, January 2002, page 11) may provide a more accurate evaluation.

The same can be said for measuring the performance of the various operating groups. An Operating Efficiency Factor may be a more accurate method of evaluating the operating groups and an Overall Efficiency Factor a method of evaluating the ability of the maintenance and operating groups to work together.

Efficiency factors that measure the performance of operating and maintenance groups, using similar information collected from daily shift reports, can help managers determine equipment maintenance and operating priorities. In addition, using efficiency factors to set priorities for equipment maintenance scheduling could reduce or eliminate the daily conflicts that arise between the maintenance and operations managers.

Most operations keep track of the scheduled maintenance hours and the breakdown hours — hour meters can assist in measuring the operating hours. However, most operations only track major operating delays, like power outages or inclement weather. Although normally not recorded, minor operating delays lasting less than 15 minutes add up, reducing operating hours. Examples of minor operating delays are delays occurring at shift changes, a loader waiting on a truck and a crusher running out of material due to truck congestion at the dump. Trucks operating at slower than normal speeds due to poor haul road maintenance also are not typically recorded. This last example could also increase truck downtime and scheduled maintenance.

An Operating Efficiency Factor measures the efficiency of the various operating groups and is calculated as follows:

Efficiency Factor = Operating Hours + Downtime Hours Operating + Scheduled Maintenance Hours/Scheduled Hours

The Operating Efficiency Factor measures the hours the facility or equipment could operate compared with the hours it is scheduled to operate, and is influenced by the operating delays. Because most minor operating delays are not recorded, Operating Delay Hours can be determined by subtracting the Operating Hours, Scheduled Maintenance Hours and Downtime Hours from the Scheduled Hours.

Just as the efficiency of equipment in a series can be determined by multiplying the efficiency of each piece of equipment, an Overall Efficiency Factor can be determined by multiplying the Maintenance Efficiency Factor by the Operating Efficiency Factor. The Overall Efficiency Factor measures the entire operation's performance and indicates how well the maintenance and operating groups coordinate and prioritize their daily activities.

If the operating group increases its Operating Efficiency Factor at the expense of reducing scheduled maintenance hours and breakdowns increase, the Maintenance Efficiency Factor will decrease and the Overall Efficiency Factor may remain the same or decrease. Increasing the Maintenance and Operating Efficiency Factors by increasing the Operating Hours should be the goal.

Bill Huber, vice president with Weir International Mining Consultants, has more than 30 years' experience in mining operations and engineering.