Symptom reliability and hazard for systems condition monitoring

Quite recently the authors of this paper defined the concept of symptom reliability for systems in use or in operation, which means that the reliability is based on symptoms of the systems under consideration. This symptom-dependent reliability is quite different from the commonly known lifetime-based reliability. But despite the lack of definition it is a quantity already used in the practice of machine condition monitoring [1]. Following this concept, the symptom-dependent hazard functions are introduced, and proposals are made for their use. This provides the opportunity to link the symptom reliability with other covariates associated with the systems usuage, such as load and maintenance quality, which are not contained explicitly within the symptom values or lifetimes. This will allow condition determination and prediction to be made more reliably and accurately, and it will make systems usage more economical than before. (C) 2000 Academic Press.