Masasumi Kokawa

Brief paper: Fault location using digraph and inverse direction search with application

A fault location method for large-scale plants is described. Fault location is executed using the following procedure: first, a digraph which indicates the failure propagation network of a plant is drawn using nodes corresponding to the devices of the plant or failure modes of the devices. Arrows which correspond to the direction of failure propagation between adjacent nodes are drawn in. Second, some nodes are chosen as candidates of the failure origin by back-tracing, using the arrows, starting from the nodes which indicate abnormal states such as rapidly rising pressure. Third, the candidates are screened by using failure propagation probabilities between adjacent nodes, failure propagation time between adjacent nodes, and back-tracing, starting from the nodes which indicate normal states. Finally, the failure propagation probabilities and the failure rates of the devices are used to evaluate the priority ranking among the screened candidates. This method is applied to pump and evaporation plants.

Brief paper: Failure propagating simulation and nonfailure paths search in network systems

This paper describes a method for identifying failure propagation paths in networks. It also assesses the risks associated with failure propagation and identifies the nonfailure paths remaining in the network after failure propagation has occurred. The method employs the following procedure: (1) selection of elements with likelihood of failure; (2) determination of failure source; (3) drawing of failure propagating network; (4) simulation of failure propagation; (5) risk assesment; and (6) search for nonfailure paths.