• RELIABILITY MODELLING OF A 3-UNIT (INDUCED DRAFT FAN) COLD STANDBY SYSTEM WORKING AT FULL/REDUCED CAPACITY

The paper presents reliability and economic analysis of a system comprising induced draft (ID) fans fitted in boilers used in thermal power plants. The function of induced draft fans is to move the flue gases out of the furnace and push them into flue gas stack. Boiler under consideration is provided with three identical ID fans: Two operative and one as a cold standby to provide redundancy. If an ID fan fails, then the one acting as a cold standby is used for which some time period is required for activation. 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. Various measures of system effectiveness such as mean time to system failure, availability analysis and busy period analysis of repairman are estimated numerically using semi-Markov processes and regenerative point technique. Some real data from the industry is used for this study. Numerical results and some graphs for the particular case are also included.