Knowledge representation for integrated plant operation and maintenance

Integrated operation and maintenance of process plants has many advantages. One advantage is the improved economy obtained by reducing the number of plant shutdowns. Another is to increase reliability of operation by monitoring of risk levels during on-line maintenance. Integrated plant operation and maintenance require knowledge bases which can capture the interactions between the two plant activities. As an example, taking out a component or a subsystem for maintenance during operation will require a knowledge base representing the interactions between plant structure, functions, operating states and goals and incorporate knowledge about redundancy and reliability data. Multilevel Flow Modeling can be used build knowledge bases representing plant goals and functions and has been applied for fault diagnosis and supervisory control but currently it does not take into account structural information. The paper will extend Multilevel Flow Modeling with foundational concepts to represent relations between plant structure and functions. The paper will present results from MFM studies of heat transfer and chemical engineering systems showing that structural information can be included in MFM models by a few extensions of the modeling language. Extending MFM with information of plant structure will make it possible to reason about consequences of component outages and their consequences for plant operation. The extensions provide also a significant general expansion of the expressivity of MFM.