Reliability And Safety Assessment For The Multi-interface Gateway

Along with the increasing growth of process scale in the thermal power plant, any small mistake in the stage of design, implementation and operation for control system, is likely to pose a threat to persons, equipments and the environment, can also make economic losses. Therefore the reliability and safety assessment for control system has drawn more and more attention. Functional safety assessment is becoming a rapidly growing technology hotspot in the fields of automation and safety control, as an important part of reliability and safety assessment. Safety integrity level (SIL) proposed by functional safety standards has also became an international uniform indicator to measure the safety performance of safety control systems and equipments. While in China, the functional safety has just started, and there has not complete system and professional assess institutions for functional safety assessment at present.In this thesis, the reliability and safety of the multi-interface gateway in LN2000 have been assessed quantitatively in the framework of the IEC 61508 standard and reliability engineering theory, based on studying the functional safety standard IEC 61508 in depth, combined with distributed control system LN2000. The accurate failure data of the gateway was obtained with the method of FMED A (failure modes, effects and diagnostic analysis). Considering two important influencing factors comprehensively which are the common cause failure and diagnosis, the models of reliability block diagram, fault tree and Markov for the dangerous failure both in control function and management function of the gateway have been derived respectively. Using three methods of reliability block diagram, fault tree and Markov, failure probability on demand of the gateway was calculated, and its safety integrity level was determined finally. In addition, the indicators that the gateway was running normally were also calculated by using the Markov model. Finally, the feasible measures and recommendations was proposed, and the indicators of reliability and safety for the improved gateway was verified as well.In this thesis, the important basis was provided for the optimization of LN2000 DCS. The results and the methods of the reliability and safety assessment which were used in this thesis provide an important reference value to the safety assessment for the whole control system.