Bijan Sarkar received B.E., M.E. and Ph.D. degrees from Jadavpur University, India. After a short period in industry he returned to Jadavpur University, where he is now a reader in production engineering.

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The reliability of a hydraulic shovel system has been assessed through the application of fault-tree methodology. Fault-tree analysis assists in the evaluation of the reliability of a system or alternative designs and identifies critical components for system success and potential causes of system failure. It uses deductive reasoning to identify system failure. A reliability block diagram and fault tree of the shovel system were developed. An algorithm for obtaining the minimum cut set as well as the minimum path set from the fault tree is presented and the reliability of the machine and its sub-systems with time is evaluated. The analysis indicates room for improvement in different aspects of the machine.The shovel-truck combination is prevalent as a mining system in India's opencast mines. The shovel is used to remove overburden and to continuously dig, haul and load the mineral on to the trucks. For mine production targets to be achieved it is essential that the shovel be reliable and available for production.The reliability of a piece of equipment or component is the probability that it will perform a required function satisfactorily under the stated operational and environmental conditions for a specified period of time; reliability is considered to be a major barometer for the overall condition of a machine. The availability of a system is defined as the probability that an item is operating or operable satisfactorily when used under stated conditions, or as the fraction of total time that an item is available for use. It is often expressed as (Total operating time)/(Total operating time + Total downtime), with many variants.Reliability assessments of mining machines have been explored in previous publications. [1][2][3][4][5] Kumar and Mishra 1 followed a basic approach derived from system reliability theory to evaluate the reliability of a hydraulic shovel given the equipment failure data. Kumar and co-workers 2 and Paraszczak and Perreault 3 carried out a reliability-based investigation of diesel-operated load-haul-dump machines in an underground mine. In these studies general analytical techniques were used to fit a probability distribution that would characterize the failure data for the machine sub-systems and to identify the sub-systems critical for further improvement. The present authors 4,5 employed graphical and analytical techniques to study the reliability and operational behaviour of shovels and their sub-systems in an opencast coal mine with the goal of continuous improvement to the machines. The development of an adequate model and assessment of reliability by fault-tree analysis appear, however, to have been overlooked and an attempt is made here to evaluate the reliability of a hydraulic shovel system by this method.

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