Direct unavailability calculations of highly reliable systems

The paper presents a new analytical algorithm which is able to carry out direct and exact reliability quantification of highly reliable systems with maintenance (both preventive and corrective). A directed acyclic graph is used as a system representation. The algorithm allows take into account highly reliable and maintained input components. All considered models are implemented into the new algorithm. The algorithm is based on a special new procedure which permits only summarization between two or more non-negative numbers that can be very different. If the summarization of very small positive numbers transformed into the machine code is performed effectively no error is committed at the operation. Reliability quantification is demonstrated on a real system from practice and on its highly reliable modifications. The selected system is frequently used system - high pressure injection system occurring in many late references.