Reliability assessment method for safety instrument system based on Markov model and D-S evidence theory

Abstract

The invention discloses a reliability assessment method for a safety instrument system based on a Markov model and a D-S evidence theory. The reliability assessment method comprises the following steps: (1) confirming a state space according to a redundant structure of the safety instrument system and forming a discernment frame theta with states; (2) establishing a basic probability assignment function on a discernment frame power set according to various characteristics of the states and further obtaining basic probability assignment; (3) calculating a reliability function and a likelihood function according to the basic probability assignment; (4) calculating a state-transition matrix in the Markov model based on the reliability function and the likelihood function; and (5) calculating average time of failure on demand, applying the D-S evidence theory to the Markov model, calculating upper and lower limits of each state through a reliability function and a likelihood function of the D-S evidence theory, and obtaining the average probability of failure on demand of the safety instrument system. Compared with the former assessment models, the assessment model is more accurate.

Description

technical field [0001] The invention belongs to the field of reliability evaluation of industrial safety instrument systems, and relates to a reliability evaluation method of safety instrument systems based on Markov model and D-S evidence theory. Background technique [0002] Industrial safety instrument system (Safety Instrument System, SIS), also known as safety interlocking system (Safety interlocking System), is mainly the alarm and interlocking part of the factory control system, which implements alarm actions or adjustments or adjustments to the detection results in the control system. Shutdown control is an important part of the automatic control of factories and enterprises. [0003] SIS executes its safety function on time and correctly before dangerous events occur, thereby avoiding or reducing the occurrence of accidents. But the function failure of SIS will lead to its safety function can not be realized. IEC 61508 "Functional Safety of Electrical / Electronic / P...

AI Technical Summary

Problems solved by technology

These methods calculate the safety reliability from different levels, but they all assume each state of the safety instrumented system as a constant, but in actual applications, the state of each equipment and system will change from "most "best" state to "second best" state, although these states are still in a specific state, but their reliability has undergone slight changes, the previous technology did not consider this issue

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