Design And Application Of Evaporator Automatic Control System Based On PLC

Taking an evaporator of food processing plant as the object of study, the paper designs anevaporator automatic control system, which is based on IPC+PLC and combines thetechnological process of evaporator and production control requirements.The hypogenous-machine of the designed system utilizes SIEMENS S7-300series PLC.Besides, some modules are configured for the system, such as5A power module,314C-2DPCPU module, AI/AO module of SM331/SM332series and DI/DO module of SM321/SM322series. The ladder program of the automatic control system is completed by using the STEP7V5.4software. In order to maintain the set point of the evaporator temperature and level, thecascade control is employed in the control scheme. The concentration is estimated by softmeasurement method. In order to maintain the set point of the concentration, the proportionalof concentrated flow-secondary steam flow is employed in the control scheme.The upper computer of the system utilizes ADVANTECH industrial PC and choseWINCC as the exploration platform. The paper has designed four humane-computerinterfaces, such as the interface of the process, the interface of parameter setting, the interfaceof trend and curve, and the interface of historical data. These interfaces realize such functions asthe display of the system interface, real-time monitoring, parameter setting and datamanagement.The paper has configured the communication network of the system by using STEP7software, and realized the communication between PLC and IPC by using CP5611. Thedesign, installation and adjusting of the system have completed and preferably achieve theexpected requirements.