TABLE OF CONTENTS This chapter outlines the activities and techniques, in design and operation, which can be used to optimize reliability.
The main objective of a reliability and maintainability programme is to assure adequate performance consistent with minimal maintenance costs. This can be achieved only if, in the first place, objectives are set and then described by suitable parameters. The intended use and environment of a system must be accurately stated in order to set realistic objectives and, in the case of contract design, the customer requirements must be clearly stated. It may well be that the customer has not considered these points and guidance may be necessary in persuading him or her to set reasonable targets with regard to the technology, environment and overall cost envisaged. Appropriate parameters have then to be chosen.
System reliability and maintainability will be specified, perhaps in terms of MTBF and MTTR, and values have then to be assigned to each separate unit. Thought must be given to the allocation of these values throughout the system such that the overall objective is achieved without over-specifying the requirement for one unit while under-specifying for another. Figure 11.1 shows a simple system comprising two units connected...
