**ABSTRACT**

This study investigated the availability of centrifugal pumps in Afam VI Gas Plant, using lognormal distribution. The lognormal distribution as a more effective and tested means of determining the appropriate time for maintenance or parts replacement was used in this study to establish a maintenance technique that will minimize system downtime, forecast maintenance requirements and reduce maintenance cost and time. The lognormal distribution parameters were obtained from the probability plot in Minitab software. The value for scale parameter obtained as 7.618 gives an idea of the scale on the horizontal axis; the shape parameter was 0.4324, and the total number of technical systems was 20. The Weibull shape parameter was 2.802 which imply that failure rate is increasing with time. The scale parameter was 2485 which gives the idea of the scale on the horizontal axis. The probability value (p-value) of the distributions are greater than 0.05, this concludes that the data followed both lognormal and Weibull distributions. The study proved that lognormal distribution is more reliable than the Weibull distribution between 200 hours and 2600 hours. The decrease in reliability with increase in time could be as a result of friction and wear of the engineering members of the pump, which was not appropriate by the operating environment. The availability of the technical system at 2600 hours with lognormal distribution was observed to be 0.7, while that of Weibull was 0.6. It was observed that the availability of the system with both lognormal and Weibull distributions decreased with increase in time. Hence, lognormal distribution can be used to estimate the availability of the centrifugal pump and other engineering systems with parts or components that fail primarily due to stress, corrosion or fatigue.

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