| In this paper, a thorough analysis is made on the problems existing in a cryogenic equipment emergency interlocking shutdown system in Daqing Oilfield Natural Gas Company. The existing emergency shutdown system uses interlock conditions of ME control system to shut down. Because of the incomplete judgment of the shutdown condition, when an accident or a subjective command forms a shutdown incident, the whole equipment in the plant cannot, according to different conditions, come to shutdown more systematically, faster and more accurately. Therefore, a separate ESD system of good safety and stability needs developing urgently to ensure smooth production.Based on the research of engineering design of the ESD system, the design principles, design methods, design process, operation, maintenance, management and other aspects are proposed for the ESD system. According to preliminary research results and the interlocking requirements between process units and equipment, a practical feasible transformation program is provided. The system uses dual redundant eDPU and the digital I/O signals for shutdown protection are put into3LPC card, respectively, and then two I/O signals are picked out of the three LPC cards. Different shutdown programs are used for different signals. Due to this design, the probability of mistaken shutdown and that of refusal to shutdown, caused by the communication problems, are decreased, so that the system’s security and stability is greatly improved.According to the causal logic diagram, the interlocking logic function of the system is sorted out. The configuration in the design scheme is based on to further determine the distribution of CPU modules and I/O modules, the allocation of I/O addresses, and the definition of variables. Based on configuration software, the interlocking protection function is implemented for the raw gas compressor, light hydrocarbon efflux pump, the light hydrocarbon tanks and other key devices. The communication between the ESD system and ME control system is researched, and so is the logic control strategy of the ESD system and the SOE configuration mode. Hardware configuration, software programming, HMI configuration and final debugging of the whole system and other aspects are considered when the improvement scheme is carried out for the ESD system. The modular design concept is adopted in the system configuration programming for rapid development and application, one result of which is a great improvement of the program’s speed and the other result is good reference provided for development of the ESD system of other similar equipment.Practical application shows that the ESD system designed here based on XDPS-400e completely solves all the disadvantages in the old system. The unified plan based on the new ESD system can ensure safe operation of the cryogenic plant. This system has been put into operation and achieved good results, which shows it meets the design requirements. |
