OPTIMAL-CONTROL LIMIT FOR DEGRADATION PROCESS OF A UNIT MODELED AS A MARKOV-CHAIN

An optimal maintenance problem of a plain bearing is discussed where the bearing is a critical unit of a piece of metallurgical equipment. The bearing shell wear process is investigated as a degradation one; maximum bearing degradation results in the whole unit and system in general break-down. The restoration cost of the failed system is definitely higher than the inspection and preventive replacement cost. To describe the degradation process a Markov chain model is used on the basis of statistical inference methods. To estimate the system operation cost a mathematical expectation of losses per unit time in a steady-state regime is evaluated. Linear algebraic equations are developed to assess the losses depending on a control limit value for the degradation process; for the given operation condition the optimal limit of degradation has been found.