C. Drebenstedt and R. Singhal (eds.), Mine Planning and Equipment Selection, 1195 DOI: 10.1007/978-3-319-02678-7_115, © Springer International Publishing Switzerland 2014 Determination of Optimal Time Intervals for the Dragline Maintenance Using Probabilistic Approaches Onur Gölbaşi and Nuray Demirel Mining Engineering Department, Middle East Technical University, 06800, Ankara, Turkey Abstract. Identifying and quantifying the components failures and their occurrence frequencies in the system offer a statistically notable data for the assessment of machine behavior as a whole. Increase in the complexity of system boosts the severity of the time-dependent availability since many components may lead to breakdown of the system in short to long term. Draglines are massive and complex systems which embody different combinations of motor and generators, structural elements and numerous components enabling to perform the earthmoving operation. In this sense, evaluating the time-varying functional importance and priority of the working parts, optimal strategies and time periods may be generated for the machine maintainability. This paper presents statistical evaluations to acquire optimal maintenance intervals for two draglines operated in Tunçbilek mine site owned by Turkish Coal Enterprise, associated with the reliability and availability issues. Keywords: Dragline, maintenance, reliability, availability. 1 Introduction The term “maintenance” can be identified as whole activities required to hold a system and its subsystems in operation and to sustain the effectuality of production while keeping down the cost [1]. The cost of maintenance can be estimated as the summation of the costs for maintenance staff and spare parts and the circuitous costs for the devolutions in the production due to insufficient and ineffective maintenance policy. Amount of the cost can reach to preposterous levels if the downtime management of the system fails and if the unplanned breakdowns induce successive negative effects on the functionality of the system. Besides, industrial demand in recent decades raised the capacity of production in all industries and forced the business areas to more reliable maintenance policies. These conditions caused so high jumps in the level of maintenance that the maintenance cost of plants only in U.S folded in two in between 1980 and 2000; and the cost reached to $ 1200 billion [2]. Investigations showed that 30 % of the