Analysis of Maintenance Man Loading Via Simulation

This paper provides the results of a computer simulation performed to test compliance with a system maintenance requirement. Special attention is given to the selection of the simulation run time (sample size) and fitting a curve to the output data. The actual simulation program was written in the RCA Flow Simulation language which is similar to the IBM GPSS (General-Purpose Simualtion System) language. More specifically, the system requirement was as follows. The probability that the system maintenance-man loading exceeds 4-h repair time in a day (24 h) shall be less than 0.0025. Equipment failures and repairs were simulated via a computer. Equipment failure and repair probability distributions were used as input data. A year´s operation was simulated in less than 2-min computer time. A simulation sample size of 360 days was selected on the basis of a statistical analysis using a nonparametric 0.60 confidence level. The results showed a maximum repair time in a day of 130 min, which indicates the system repair time distribution is considerably better than required. The output data were analyzed and the observed repair times were fit with an empirical distribution function.