Jun 30, 2015: Richard Heijbloem: Spare Parts in Fault Trees

June 30, 2015Spare Parts in Fault Trees
Room: HB2ARichard Heijbloem

By keeping spare parts one can enhance the dependability of a system. Without spare parts, one has to order new parts when components fail. During the supplytime of the spare parts, the failed components cannot perform its functionality, which generally results in a less reliable system. If spare parts are kept, this situation is tackled. When components in the system fail, the components can be replaced immediately by spare components. The system recovers earlier from component failures, which results in a more dependable system.

Considering spare parts, one can raise two questions about spare parts: what is the influence on the dependability of keeping spare parts, and what is the optimal set of spare parts for a given system? Unfortunately, is was not possible to model spare parts and repairable components in fault trees (FTs). Hence it was not possible to answers the questions about spare parts. A new extension, an extended dynamic fault tree (EDFT), was constructed to deal with FTs with spare parts and repairable components. An EDFT is solved by translating it to a set of timed automata (TAs). These TAs are solved by UPPAAL to obtain information such as unavailability of the EDFT. A prototype was created to analyze static fault trees (SFTs) with spare parts and repairable components.

This new model is not limited to SFTs, nor to the extension of spare parts. TAs offer a very flexible and adaptable intermediate model. Other extensions, such as limited repair teams or dependent events can be added later on