Optimal Preventive Maintenance Model for Steam Turbines: A Case Study of Egbin Thermal Station, Lagos, Nigeria

In this work, optimal preventive maintenance models have been developed using Weibull Distribution to predict maintenance models for Egbin steam turbines. The results obtained were practically correct in that there is an inverse relationship between the input and the output when the graphs of the models were plotted using MATLAB. It was clearly shown that the total cost of replacement was decreasing as the cycle length was increasing. For a cycle of 50,000 ≤ ≤ 500,000, the optimal total cost of replacement is approximately 800.54 USD (N124,884.24) with current exchange rate of $1= N156. At the beginning of the cycle, 50,000 cycles, the total cost per unit turbine required to perform a preventive maintenance was 800.63 USD which was quite high. It implies that it is more expensive to perform a preventive maintenance at the
inception of a preventive maintenance cycle. The cost decreases as the cycle increases. It is worthy of note that there exist an inverse relationship between the total cost of replacement and the cycle length. It reveals that for an increasing cycle length above 500,000 cycles, the total cost of replacement per unit turbine becomes constant; the optimal total cost per unit turbine of performing preventive maintenance. Also, the downtime continues to decrease until it gets to a very minimal level before it becomes steady. There also exist an inverse relationship between the total downtime (seconds) and the cycle length, and the expected cost of performing group maintenance and the number of days in a year. Hence, it requires a high cost at the beginning of the year
to perform group maintenance than towards the end of the year. The expected cost of performing group maintenance continues to decrease through the year until the expected cost gets to about 1 USD at the 366th day.