Abstract
This paper describes a simulation modeling technique for assessing the availability of an ammonia plant. Field data on failure and down times have been collected and analyzed by fitting Weibull distributions. Plant availability has been estimated using the existing plant configuration and actual failure and repair time distributions. Analytical models based on the exponential and Weibull distributions have also been discussed. Availabilities obtained from different models have been compared and found to vary slightly. The possibility of improving plant performance by modification of plant configuration and change of overhaul strategy has also been studied.