Temperature monitoring system based on DCS
Abstract: This paper briefly introduces the composition and function of water treatment DCS system, discusses the principle and software design of temperature monitoring of circulating water on the basis of DCS, the system has a good operation effect and significant energy saving effect.
Key words: DCS; Frequency converter; Master/auxiliary control
1. Overview
Industrial circulating water steel rolling industry occupies a very important position, and its water temperature directly affects the safety and service life of heating furnace and rolling mill equipment. In order to monitor the circulating water timely and accurately, the water treatment of small and medium-sized workshop of Laisteel Rolling mill adopts SUPCON JX-300X DCS control system of Zhejiang University. DCS control system integrates computer, instrument and electronic control technology to realize automatic data acquisition, processing, process screen display, parameter overlimit alarm, equipment fault alarm and report printing functions. On this basis, the closed-loop control of circulating water temperature and temperature is developed.
2. System introduction
5A26458G05 SUPCON JX-300XDCS uses high-speed industrial Ethernet Scnet as its process control network, the system is composed of engineer station, operation station, control station, process control unit, etc., the configuration is flexible. Water treatment system scale, water treatment SUPCON DCS system design 1 control station, 1 operation station set safety level can also be an engineer station), constitute a two-level structure. The control station is field-level and directly exchanges data with the field equipment to complete the real-time monitoring function of the entire industrial process. The operation station (and engineer station) is a supervisory control level, which can complete the system configuration and realize the on-site detection, control and protection function management. SCKey configuration software of SUPCON JX-300X DCS system is a software platform that supports all kinds of control schemes of the system. SCKey configuration software can complete the entire system control station configuration (system I/O configuration, control scheme configuration, etc.), operation station configuration (screen setting, system flow chart configuration, system report configuration, etc.). The system structure is shown in Figure 1.
Figure 1 System structure diagram
3. Temperature monitoring scheme
3.1 Scheme Design
5A26458G05 The industrial water circulates back from the production hot line into the 1# and 2# suction Wells for heat dissipation, and the 1# and 2# fans at the top of the suction well tower for cooling, and then the bottom of the 1# and 2# suction Wells share an outlet pipe for water supply for the next process, and the water temperature is required to be controlled below 30ºC. In this system, Cu50 thermal resistance is installed at the outlet pipe of the suction well to detect the water temperature, the temperature signal T1 is sent to the DCS processor, and the control signal is given after the control law is calculated. The inverter is controlled to change the input voltage frequency of the motor, change the motor speed, and drive the fan to cool down, forming a closed-loop temperature control system. Two Japanese SANKEN (300KW) general-purpose frequency converters are selected for frequency converters, and the control principle is shown in Figure 2.
FIG. 2 Schematic diagram of system control
5A26458G05 The characteristics of heat exchange at the bottom of the circulating water suction well, the main/auxiliary control of the two fan motors in the 1# and 2# suction Wells, and the different speed curves of the main/auxiliary motors drive the fan. 1#, 2# motor can be selected as the main/secondary motor, which greatly facilitates the operation of the operator.