Probabilistic analysis of a 3-unit induced draft fan system with one warm standby with priority to repair of the unit in working state

This paper deals with the probabilistic analysis of a three unit induced draft fan system fitted in boilers used in thermal power plants. For this analysis, a transition diagram for the system is developed and cost-benefit analysis is carried out using semi-Markov and regenerative processes. Boiler under consideration is fitted with three ID fans: Two operative and one as a warm standby to provide redundancy. If an ID fan fails, then the one acting as a warm standby starts working instantaneously. The unit can also work at reduced capacity with one ID fan when parameters are controlled but this leads to low power production. If parameters cannot be controlled in a stipulated time period then the system goes into down state. Failed state is considered only if all the ID fans fail. Priority is given to repair of the unit over controlling the parameters when in working state. The expression for various measure of system effectiveness such as mean time to system failure, availability analysis and busy period analysis of repairman are estimated numerically. Numerical results and some graphs to a particular case are also included.