Criticality analysis of process systems

This paper presents a systematic methodology for formal criticality analysis of process systems, which properly accounts for process interactions, equipment failure, stochastic process variations and events related to process safety. Important extensions are also presented for the use of such criticality analysis tools for safety and maintenance considerations. In the first part a quantitative measure for estimating the expected level for critical operations of process systems is introduced. Next a systematic algorithm of rating the equipment or events according to an associated criticality index is presented, coupled with a methodology for condition based maintenance for enhancing overall system efficiency and safety. The developed tools and the algorithms are demonstrated via a realistic case study of a compressor system, where (FOR) and (COR) are properly identified for the operable states. The proposed methodology is applied in order to rank the critical parts of the equipment or events, and then to result in the maintenance policy which fulfill certain efficiency and safety targets. While the criticality analysis methodology developed in this work predicts variable information regarding the overall system expected critical operations, the relative importance of the equipment to the process and identification of process and/or reliability bottlenecks, its link to the design optimization algorithm has not been formally established. However, as it is shown via the case study, the proposed methodology could be an efficient tool for the proper balance of preventive and condition based maintenance activities and the prediction of their impact to process operational decisions.