Functional Modeling for Process Safety

Process safety is of considerable concern for society, in order to reduce the risk for major accidents with severe consequences for human lives and economy. The accidents also indicated process complexity as a major challenge for process safety. Presently process safety is evaluated using qualitative methods which rely upon careful bookkeeping for reevaluation when process modifications and improvements are considered. Consequently it is desirable to develop a more systematic modeling methodology which may be applied for safety assessment and which conveniently may be reused when necessary. An established qualitative modeling framework is Multilevel Flow Modeling (MFM) which is based on functional modeling. It has been suggested that MFM can deal with the complexity of design and operation of process engineering systems with a promising application future. Qualitative
modeling and reasoning as implemented with MFM can with advantage be combined with quantitative methods in order to automate analysis and evaluation of safety in industrial processes, especially in oil and gas industry with increased coverage of the analysis or for validation purpose. The paper will point out the difference and connections between the qualitative modeling (e.g.
functional modeling) and quantitative modeling (e.g. differential and algebraic equations, DAEs) in the process safety context. Then the MFM method will be introduced. A recent HAZOP study of an oil and gas separation plant is summarized. It is shown that validation is a key issue here. It has been investigated how the reasoning results from an MFM model could be validated by comparing it with simulation using a quantitative model. However, due to the complexity of advanced industrial process system, MFM still faces many challenges in industrial process safety application. Finally, the suggested future work within the aspects of supporting for MFM modeling construction, reasoning, validation and counteraction planning are discussed.