Availability and Inspection Interval of Protective Devices

Protective devices are designed to protect people, the environment and material assets under emergency situations. If protective devices do not work well, serious consequences may be resulted. It is critical to pay special attention to their maintenance. For this reason, many availability models have been developed to obtain an optimal inspection interval and to maximize their availability. However, few attention have been paid to the relationship between the statistical distributions used to describe the lifetime of protective devices and their optimal inspection interval and maximum availability. Furthermore, the problem that might occur when the normal distribution takes negative values has not been considered yet in protective device maintenance. This thesis aims to calculate the optimal inspection interval and maximum availability for the Weibull, normal, truncated normal and exponential distributions. Also, the relationship between these statistical distributions, and the availability and the inspection interval is studied. Finally, this thesis intends to study the problem that arises when the normal distribution might take negative values.