Mean Time Before Unscheduled Removal

Mean time before unscheduled removal [MTBUR] refers to the premature failure of a part or system that causes the part or system to be removed and replaced prior to its anticipated life expectancy. For example, supposing a supermarket anticipates that the fluorescent tubes in a store have a design life of 5000 hours, and that they will all be replaced at that time. However, some of the tubes fail prematurely, requiring individual replacement. The average time before the parts failed across all of the failed tubes would be the mean time before unscheduled removal. This calculation would aid reliability planning and judgement about the total cost and the life of the tubes. See also Mean Time Before Failure.