Mining Equipment Reliability

Introduction

Each year, a vast sum of money is spent to produce various types of equipment for use by the mining industry around the globe, and this expenditure is increasing quite rapidly. For example, in 2004, the United States mining equipment manufacturers shipped approximately $ 1.4 billion worth of goods, and a year later that figure jumped to around $2 billion [1]. Nowadays, the world economy is forcing mining companies to modernize their operations through increased automation and mechanization.

Thus, as equipment used in mines is becoming more complex and sophisticated, its cost is increasing rapidly. This in turn makes it quite cost-ineffective for having standby units. To meet production targets, mining companies around the globe are increasingly demanding better equipment reliability. Reliability is a very good indicator of overall equipment condition and is expressed as the probability that a piece of equipment will perform its function satisfactorily for the desired period of time when used as per stated conditions. However, it is to be noted that in the industrial sector reliability is often expressed in terms of mean time between failures.

This chapter presents various important aspects of mining equipment reliability.

Reasons for Improving Mining Equipment Reliability and Factors Impacting Mining System Reliability

There are many reasons to improve reliability of mining equipment and some of these are as follows [2,3]: [1]

  • • To overcome challenges imposed by global competition.
  • • To provide more accurate short-term forecasts for operating hours of equipment.

There are many factors that, directly or indirectly, impact mining equipment/system

reliability. Thirteen of these factors are as follows [2,3]:

  • Factor 1: Equipment failure. It is basically a maintenance issue and it causes an interruption in the production process.
  • Factor 2: Refueling and lubrication. In this case, stoppage of equipment for refueling and lubrication results in the interruption of the production process.
  • Factor 3: Minor production stoppages. In this case, “comfort stops”, such as minor adjustments, can interrupt the production process.
  • Factor 4: Routine maintenance. In this case, routine servicing, overhauls, component replacements lead to interruptions in production while the equipment is taken out of service.
  • Factor 5: Accident damage. In this case, it causes an interruption to the ongoing production process if the equipment has to be taken out of service for inspection or repair.
  • Factor 6: Spillage and housekeeping. In this case, the need to stop and clean up spillage around the shovel or the dump area causes an interruption in the production process as well.
  • Factor 7: Shift changes and crib breaks. In this case, every shift change and crib break usually leads to an interruption to the steady-state nature of the production operation.
  • Factor 8: The blast. In this case, there is frequently a need to stop the equipment operation.
  • Factor 9: Ineffective blasting. In this case, it can lead to problems, such as poor digging ability, in certain areas and unreliable equipment operation.
  • Factor 10: The mine plan. In this case, it normally calls for equipment to be shifted on a periodic basis as different areas are to be mined.
  • Factor 11: Weather. In this case, fog or rain can interrupt production.
  • Factor 12: Downstream process. In this case, if a dow nstream process stops in a direct tipping situation, it can lead to an interruption in the mining operation.
  • Factor 13: Geology. In this case, variability in digging conditions can result in the need for trucks or shovels to stop.

Useful Reliability-Related Measures for Mining Equipment

There are many mining equipment, directly or indirectly, reliability-related measures.

Five of these measures considered quite useful are presented below [2,3].

Measure I: Mean Time Between Failures

This is defined by

where

MTBF is the mean time between failures.

F is the number of failures.

H, is the total hours.

Hd is the downtime expressed in hours.

Hs is the standby hours.

Measure II: Production Efficiency

This measure may simply be described as the ratio of actual output from a piece of equipment/machine (which satisfies the required quality standards) to its rated output during the period it is operational. Nonetheless, production efficiency is defined by

where

Ep is the production efficiency.

Pa is the actual production.

Cr is the rated capacity expressed in units per hour.

Measure III: Utilization

This is expressed by

where

UT is the utilization.

Measure IV: Overall Equipment Effectiveness

This is defined by

where

Eoe is the overall equipment effectiveness.

A Vme is the mining equipment/system availability.

Measure V: Availability

This is simply the proportion of time the equipment/system is able to be used for its intended purpose and is defined by

  • [1] To lower the cost of poor reliability (the true poor reliability cost in mostmining operations, when estimated effectively, is quite significant). • To take advantage of lessons learned from other industrial sectors such asnuclear power generation, defense, and aerospace. • To lower the performance of mining equipment-related services in an unplannedmanner because of short notice. • To maximize profit.
 
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