Study On ESD To Hydrotreating Unit Equipment Based On PLC

Emergency Shutdown System (ESD) is a kind of Safety Instrumented System (SIS).In the equipments of Petrochemical Corporation, they are filled with poisonous, inflammable and explosive dangerous materials. It's prone to go dangerous, so it is very urgent to design an Emergency Shutdown System to protect equipments and workers.In this paper, an Emergency Shutdown System was researched and designed aim at diesel oil with hydrogen equipment such as fresh hydrogen compressor, recycle hydrogen compressor, feed stock pump and heating furnace, after realizing its processes and characteristics of equipments. And the choice of hardware and configuration, network configuration, the realization of redundancy control and communication between host computer and PLC; establishment of the Access database and design of HMI were introduced in detail.The main work includes:(1)After analyzing the interlock relationship among the equipments among diesel oil with hydrogen equipment, emergency shutdown interlock logic were designed in this paper, to protect fresh hydrogen compressor, recycle hydrogen compressor, feed stock pump and heating furnace.(2) Compared with the different structures of ESD in this paper, two modules of SIEMENS'CPU315-2DP were chosen as the key controller of the system, and constituted a redundancy ESD system, its CPU, ET200M remote I/O station and PROFIBUS network were redundancy structure, promoted reliability of the system.(3)The design of hardware in this paper includes:calculated I/O according to the equipments and the demand of emergency shutdown interlock logic and calculated memory according to the experience formula; selected SIEMENS' S7-300 module PLC to build model of system (hardware configuration) and the Ethernet connection between two PLC based on ISO-ON-TCP protocol and the Ethernet connection between PLC and PC based on TCP protocol.(4) Using STEP 7 software, redundancy control between PLC was realized. Ethernet communication between host computer and PLC through WinSock port was realized by common network card. (5) Using Visual Basic 6.0 software, Access database was developed. PLC's collection data was stored and these data through ADO was called on. Man-machine interface of monitoring was designed by Delphi 7 software, and Access database was visited by ADO of Delphi 7, on-line monitoring run parameters and tendency, historical data query and alarmed record query were realized.