Submarine pipeline automatic-repair system-an approach to the mission-availability assessment

The authors present the methodology followed to evaluate the mission availability of a remotely controlled submarine system designed to repair damaged pipelines in deep waters. The goal of the analysis has been to identify the technical and operational solutions with respect mainly to the logistic support system design, to guarantee operational availability and thereby minimize delays. To this purpose, the FMEA and the fault tree analysis technique for reliability assessment of each subsystem have been supplemented by an event tree analysis performed through a computer software package (ADMIRA). All sequences of failure and/or success for the whole system have been analyzed during all the operation steps. This analysis has allowed an estimate of the delay for each possible system state. The analysis has shown that the event tree approach is an adequate tool to handle situations where failure occurrences and dependencies among different events have to be taken into account. The analysis has led to improved design, operator skills, and training as well as support system definition