Design and Maintenance of Two Distinct Types of Safety Interlocks in Continuous Processes

  • 石 祳祥

Student thesis: Master's Thesis


An interlock is a feature that makes the states of two mechanisms or functions mutually dependent and the safety interlocks are needed in almost every continuous chemical plant for mitigating the detrimental effects of hazardous incidents On the various processing units in a plant the interlocking systems may be installed to achieve two completely opposite goals i e emergency shutdown (type I) and operation sustaining (type II) Thus the corresponding configurational features and maintenance policies are determined in this study with two separate optimization codes to minimize the expected total life-cycle expenditures for their respective operational objectives Specifically the well-established genetic algorithm (GA) has been adopted to produce two distinct MATLAB codes Non-uniform inspection intervals are adopted for maintenance of the actuators and warm standbys while the ages of these components are assumed to follow Weibull distributions For the single-layer type-I interlocks that are used for emergency shutdown the encoded data in each binary string should be: (1) the number of measurement channels and the corresponding alarm logic (2) the numbers of online and spare sensors in each channel and the corresponding voting gate (3) the number of shutdown channels and the corresponding tripping configuration (4) the numbers of online and standby actuators in each channel and the corresponding activation mechanism and (5) the inspection schedule of each shutdown channel In order to sustain continuous operation of the critical processes each type-II interlock is equipped with an online unit a switch and one or more warm standby unit The online unit is usually monitored with a set of known sensors (measurement channels) From the optimum solution one can obtain the following specifications: (1) the numbers of online and spare sensors in each measurement channel (2) the inspection schedule of the switch and the number of spares (3) the inspection schedule of warm standby and the number of its cold standbys Finally two examples one for each type are provided in this thesis to demonstrate the feasibility of the proposed approach
Date of Award2017 Aug 10
Original languageEnglish
SupervisorChuei-Tin Chang (Supervisor)

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