Main fuel trip( MFT) in thermal power plants is a safety instrumented system which can achieve tripping protection for boilers. In order to ensure normal operation of the safety function

preventive maintenance strategy research was carried out. On the basis of the actual operation

the Markov model for furnace pressure protection function of the MFT was established. The reliability and security theory were applied to perform multi-objective optimization strategy

by taking the highest availability and reliability

and lowest maintenance cost as the goals. Moreover

the preventive maintenance intervals were optimized within the time range the regulations ruled.