RELIABILITY ANALYSIS OF TWO DISSIMILAR PARALLEL UNIT OIL DELIVERING SYSTEM WITH PREVENTIVE MAINTENANCE AND CORRELATED LIFE TIME

In this paper we study a two dissimilar parallel unit oil delivering system with preventive maintenance of both units with one repairman under the assumption that each unit is as good as new after the preventive maintenance and repair. System will fail when both the units fails totally. Failure and Repair times of each unit are assumed to be correlated. Using regenerative point technique various reliability characteristics are obtained which are useful to system designers and industrial managers. MTSF and the profit functions are studied graphically he reliability analysis of a variety of system models with identical/non-identical units and different repair and failure policies exist in the literature on reliability theory. A two dissimilar parallel unit systems have widely studied in literature of reliability theory and repair maintenance is one of the most important measures for increasing the reliability of the system. Many authors have studied various system models under different repair policies (3-4) they have assumed that the failure and repair times are uncorrelated random variable. During our visit in an oil refinery we have seen that in an oil delivering system after repair, a unit recovers its function perfectly. An operative unit (A or B) goes to a specified time t and it is free from failure in that interval, the unit undergoes inspection as the PM. We also assume that the switching over times from the repair to the PM and from the PM to the operative state are assumed to be instantaneous. Taking this fact into consideration in this paper we investigate a two dissimilar parallel unit oil delivering system model in an oil refinery with failure and repair of unit as correlated random variables having their joint distribution as bivariate exponential .