Followup of production equipment availability and its contributing factors in selected Canadian underground mines



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Profitability of operations depends on, among other factors, the capacity of the production equipment employed to perform revenue-generating jobs for as much time as possible. In this context, achieving higher equipment availability is crucial.
Quantification of the factors influencing equipment availability and a thorough analysis of adequate performance measures allow identifying competitive opportunities, prioritizing resources and assessing the progress of improvement initiatives. Even though mining has lagged behind other industries such as manufacturing in this respect, the growing use of computerized maintenance management systems  and condition-based monitoring gives mine operators new opportunities to quantify more precisely different aspects of equipment availability.
Because little information on how Canadian underground mines assess their equipment performance can be found in the technical literature, it was decided to examine and analyze the means and measures used by mines to assess availability and its contributing factors. The questionnaires developed specially for this purpose were sent to over 20 Canadian underground mines whose production is based on a wide-spread use of mobile trackless drilling, loading and haulage equipment. Information deemed adequate with regard to the objectives was received from 12 mines. This sample includes mostly base and precious metals mines situated in eastern Canada. Their daily production is between 2,700 and 10,000 metric tonnes, and the predominant mining method is long-hole stoping (10 mines).
The 12 mines considered in the study operate mobile production equipment fleets numbering from 16 to 64 units (drill jumbos, drill rigs, LHD, trucks and mechanized bolters). Based on the information received, the paper reviews and analyzes the sources, quality and quantity of data and information collected, and the methods and procedures in use. It examines performance measures and related definitions that are used by the mines under study. Survey results are presented according to determination of downtime and its components, calculation of availability, measurement of reliability and assessment of maintainability. The survey proves that almost all the mechanized mines have already recognized the crucial role of equipment availability in the quest to reduce production costs. They collect and process substantial quantities of pertinent data in order to calculate different performance measures.
The study has also revealed some deficiencies, inconsistencies and/or problems adversly affecting the relevance of data and of some performance measures. They include the use of site-specific definitions and interpretations of even the most basic notions and measures that sometimes do not conform to widely recognized standards. It has also been discovered that the mines use, on average, only five measures of availability, maintainability and reliability. The most commonly used are the following: availability (mostly operational), ratio between planned/scheduled and total maintenance man-labour, maintenance ratio (maintenance person-hours to operating hours), mean time to repair (in terms of man-labour hours and hours elapsed on the clock), and mean time between failures.
This paper gives some suggestions and recommendations aimed to improve the quality and quantity of relevant data and information, as well as data analysis. Among the key recommendations is the unification of terminology and definitions through adoption and use of standards such as CAN/CSA Q631-97 (1997). Also, more performance measures should be employed. For example, given the distinct difference between time to restore/repair and downtime, it is suggested to implement two separate measures: mean repair time that may be expressed in maintenance person-hours and mean downtime in clock hours. It is also recommended to focus more on identification of downtime components. Classification and followup of delays will help identify the true nature of problems. It is believed that the suggestions and recommendations given in this paper will assist mine operators to ameliorate assessment of their equipment availability, reliability and maintainability, to become a more useful tool to improve equipment performance and, consequently, to reduce costs.
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