The paper evaluates the availability simulation model (Av.) for the performance analysis of coal supply system in a coal-fired power plant using Markov approach. Coal supply system ensures proper supply of coal for sound functioning of thermal power plant. This system consists of four subsystems, i.e., Wagon tippler, Crusher, Conveyor belt and Coal mills. For the analysis, an availability simulation model (Av.) is developed with the help of mathematical formulation based on Markov Birth-Death process using probabilistic approach. For this purpose, first order differential equations are developed based on the transition diagram developed for the system. Then these equations are further solved by using normalizing conditions so as to determine the availability simulation model (Av.), i.e., measure of performance of the coal supply system. This performance evaluating model deals with the quantitative analysis of all factors (courses of actions and states of nature), which influence all maintenance decisions associated with this system. The results show that coal mill subsystem is the most sensitive and demands more improvement in maintainability as compared to other subsystems.

There is a growing interest in the availability analysis of process plants. The process plants are large and complex engineering systems. In this type of industry, which is capital-intensive, production is generally carried out on a continuous basis. Therefore, production unit availability (which is a function of both reliability and maintenance) is very important and critical for the smooth functioning of the plants. The thermal industry is becoming quite complex with huge capital investment being incurred on process automation to enhance the availability of system. Availability is a function of both reliability and maintainability. More simply, it is the fraction of total mission time that the system is in operation. The concept of availability is of value for reliability and maintainability tradeoffs. An availability assessment provides a measure of total equipment performance. The main function of coal supply system of the plant is to supply the quanta of processed coal to bunkers of coal mills for boiler operation and to stack the coal to coal yard. The wagons received from collieries are placed one-by-one on the cradle of the wagon tippler in the central position. The cradle with the wagon gradually starts inclining towards the hopper and the wagon comes in contact with the side bolster cushion. The hoisting being continued, the wagon cradle, arms and side supporting girder form one unit and revolve about the turn-on until the top of the wagon meets the top bolster pads and further together with the top sustaining structure, revolves until the material is fully discharged. The tippler is brought back to its original position by reversing the hoisting gear. The operation can be done on auto or manual as the situation warrants. Through the conveyor belts the coal is transferred to crusher. A conveyor belt basically consists of an endless moving belt carrying idlers and individual rollers with antifriction bearings and conveys from one transfer point to another. Crusher is installed for crushing the coal to proper size. The crusher must handle sticky coal without clogging up and must be of suitable type to take all the incoming coal from the conveyors. After that, coal is transferred to coal mill to convert it into powder form which is fed to the furnace of boiler. So, for the smooth functioning of boiler, coal supply should be there in a continuous manner.

Mechanical Engineering Journal, Availability simulation model (Av.), Transition diagram, Probabilistic approach, Markov approach, Stochastic analysis.