Abstract: The expression of the complex equipment failure rate under the normal operating conditions were researched based on the renewal theory. The results show that the limit of the complex equipment failure rate λ(t) is a integral expression under the arbitrary failure distribution, only when the failure obeys the exponential distribution, as a special example, the limit is a constant. The theoretical research results have been strongly supported by the actual operating failure rate λ(t) of complex equipment. This research has important theoretical value and practical meaning for guiding the operation, detecting test and diagnosis, maintenance and repair of the complex equipments.

Key words: mechanical engineering, complex equipment, renewal theory, failure rate expression