Functional security verification method for safety instrument based on Markov process

Abstract

The invention discloses a functional security verification method for a safety instrument based on Markov process. The functional security verification method for the safety instrument based on the Markov process includes: using a Markov model to calculate failure rate on demand of a single device in a one-to-one structure, calculating probability of co-failure of multiple devices based on the failure rate on demand of the single device in the one-to-one structure, and calculating failure rate on demand of a redundant structure according to the probability of co-failure of the multiple devices; and verifying functional safety integrality level of the safety instrument according to the average failure rate on demand of the redundant structure based on the requirements in IEC61508. The functional security verification method for the safety instrument based on the Markov process has the advantages that the Markov model covers various statuses of the system to reflect dynamic behaviors of the system, and accordingly precision in calculating the failure rate is improved; the failure rate on demand of the redundant structure is calculated indirectly according to results of calculation on the failure rate on demand of the one-to-one structure, and accordingly the difficulty in direct Markov modeling and model calculation for the redundant structure is avoided; and a beta factor model and a binomial failure rate model are used to consider common cause failures, and the precision in calculating common cause failure rate is improved.

Description

field of invention [0001] The invention relates to a Markov process-based method for functional safety verification of safety instrument functions, which is mainly used in the field of functional safety verification of process industries such as chemical process, oil refining process, and biopharmaceutical process. Background technique [0002] Safety is crucial to economic, environmental and personal safety, so Safety Related System (Safety Related System, SRS) is widely used in the production process. Safety Instrumented System (SIS) is a category of safety-related systems. According to the definition of IEC61511, a safety instrumented system refers to an instrumented system that is composed of sensors, logic controllers and actuators and can perform one or more safety instrumented functions (Safety Instrumented Function, SIF). In a certain period of time and under certain conditions, the possibility that a safety instrumented system can successfully perform its safety fu...

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Problems solved by technology

[0008] An object of the present invention is to use the Markov model to cover multiple states of the system, to reflect the characteristics of the system dynamic behavior, and to overcome the shortcomings of the difficulty in modeling redundant structures, and not to perform direct Markov modelling on N-selected-M redundant structures. The Kov model is established, but the failure rate of the N-selected-M redundant structure is indirectly deduced from the calculation results of the 1-selected-1 structure, thereby avoiding the difficulty of establishing a Markov model for complex redundant systems

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