Treatment in net ring PLC automatic control system research and application
Treatment in net ring PLC automatic control system research and application
This article describes the SIMATIC S7-300PLC in the net loop water treatment system. Detailed description of the control system hardware configuration, software design and its function to meet production needs. Practice has proved that the system design is reasonable, stable and reliable.
1 Introduction Net Central Cleaning Automation Control System and the color coating is continuous hot-dip galvanizing project water supply system. Water treatment monitoring and to automate real-time control is to improve water efficiency, reduce energy consumption in the key. Used to PLC Process as the core of the automatic monitoring system for all Pump , Automatic control valve, on the aeration equipment, drainage equipment, programming control of the operation. According to process real-time control tower fans, pumps, electric valves and other equipment. The flow of water, industrial water temperature to meet the requirements to achieve the purpose of automatic water treatment process.
2 System Description The system has four controller: Net Central station, galvanized stove cool return water pump station, color plate cooling Backwater pump station and stormwater sewage pumping station. Net ring which is 2 # pump stations, pump stations galvanized stove cool return water is 3 # stops, color plate cooling backwater pump stations is 4 # station, rain sewage pumping station is 5 # Station. The system flow chart shown in Figure 1.
3 control system hardware Systems architecture shown in Figure 2, the main part of its functions are as follows.
Figure 2 System Architecture (1) PLC Control system Based device requires, use the higher cost Siemens S7-300 series programmable controllers to build a control system. Net ring pump station and stormwater sewage pump station PLC CPU used in the PLC CPU315-2DP, and net ring pump station with two expansion rack PLC, color plate cooling Backwater pump station PLC and PLC stove cool return water pump station the CPU using CPU313C-2DP. The four means of communication between systems using Profibus-DP network connection. PLC hardware configuration diagram shown in Figure 3.
AC 220V Power supply Power supply, the main module has 16-point digital input, for detecting control commands and switches state; 16 points digital output, for the operation of the control switch and indicator, the status display; analog input, analog measurement signal change The corresponding figures for the amount has been received by the computer. Net ring pump with 14 signal processing module (7 DI, 4 DO, 3 AI), expansion module selection IM360 and IM361, color plate cooling Backwater pump station has four signal processing module (3 DI , 1 DO), furnace cooled return water pump station has four signal processing module (3 DI, 1 DO), rain sewage pumping station has seven signal processing module (3 DI, 2 DO, 2 AI).
(2) Monitoring Station Monitoring station selected Siemens Industrial control computer and high-performance industrial control software WinCC (Windows Control Center), the completion of the entire system of processes, equipment operation status display and monitoring, and curve display, historical data preservation, rights management operation check, alarm, printing. One of the host computer to monitor the net water pump station, galvanized stove cooling pump stations and the color plates backwater backwater cooling pump stations of the production process, and the other to monitor the production of rain sewage pumping station, while two PC backup each other to improve system reliability.
(3) Instrument System Instrument system consists of transmitter, With electrical , Isolators, regulators and actuators, etc., was completed for flow and pressure signals in the implementation of access and control valves, regulators, as an alternate means of control computer system, when the computer fails, you can become a manually controlled.
4 Automation Software Design Net ring water automatic control system software including PC, slave in two parts.
4.1 PC software design Order to ensure the stability of the industrial field, the PC using Windows2000 operating system, programming platform WinCC5.1. PC to achieve the following functions: digital display of flow, pressure, temperature, liquid level, showing the device to start, stop, run, fault and other state; startup, device button is green, normal red color screen flashing fault the same time, with text displayed fault type, to facilitate fault exclusion; to record 250 fault conditions (fault time, fault type, etc.) easily accident analysis, through the statements of the editor, to achieve a regular or random information printout. HMI control screen shown in Figure 4.
Figure 3 PLC system hardware configuration diagram
Figure 4 HMI control screen 4.2 lower computer software design
Lower machine developed by SIEMENS STEP 75.2 software for PLC programming and configuration of the PLC equipment maintenance. The software includes the preparation of signal acquisition and processing, signal control, fault module design, and PC communication DB block design.
STEP standard provides a generation library or FC derived function block programming capability library functions can be called within the application again and again, in this system, due to detection of many points, this function has been widely used. FC function block the use of saving a lot of process time, space and fault diagnosis. Reduces the programming complexity, make the program structure more clarity. Proved, FC function block used to improve the program run faster and more convenient for software portability and scalability.
5 system to achieve functional 4 pumping stations were used on-site, centralized operation mode. In the centralized operations, is divided into two kinds of manual and automatic mode of operation.
Galvanized stove cooling pump stations and the color plates backwater Backwater pump station net cooling loop pump 3 pumps and 2 sets of cooling towers. 3 sets of them prepared with 1 pump 2, when the system needs less water, opening a filling station pump to the pipeline pressure, water is heavy, open two pumps simultaneously to the pipeline filling pressure.
Color plates enhance the cooling backwater backwater pumping stations and galvanizing furnace cooling pump stations own two pumps. The two pumping stations use the same control method. Which 1 # 2 # pump pump and mutual backup. Working pump and automatic backup pump. Set color board cooling pond and pool set within the stove cooling with liquid level monitoring devices were used to monitor the pool level of the water absorption. 1 # and 2 # pump control mode: When the water level h> 2.20m when Motor Started, the water suck out; when the water level h