Reliability and Cost-Benet Analysis of a System Comprising One Big Unit and Two Small Identical Units with Priority for Operation/Repair to Big Unit

A three-unit system working in a sugar mill with one big unit and two small identical units is examined in the present paper. Upon failure of the big unit, both the small units are made operative and the failed unit is undertaken for repair immediately. Priority for operation as well as repair is given to the big unit. System is able to work with full capacity only if either the big unit or both the small units are in good condition. If only one small unit is operable, the system works at reduced capacity. The system under consideration goes to rest during the non-seasonal period. The information obtained from the mill revealed that the system is brought to work at reduced capacity when the system is about to go to the rest period due to shortage of sugarcane near the end of season, irrespective of the number of operable units. This fact has also been considered while developing the model. The expressions for the MTSF; availability; expected busy period for the repairman during both the periods, that is, working as well as rest period; PM/CM and the reliability have been obtained using semi-Markov processes and regenerative point technique.