In this paper, Wei Ye Zhanhua boiler feed water treatment plant control system, for example, discusses OMRONPLC in water treatment fields. The system s hardware, software structure and working principle are described, and focuses on OMRONPLC subroutine call structure and analog signal processing, software programming and communicating with the man-machine interface, the programming notes. Application shows that the system can meet the automatic control of power plant boiler feed water treatment requirements, and advanced, reliable, and good control performance.
Master control unit is used C200HEPLC OMRON PLC products for small and medium companies to facilitate the realization of extension of good manufacturing site; can further enhance the PC s basic functions, reliable and convenient data processing to improve the efficiency of the production site; CX-Programmer is the development OMRON used in C200HPLC programming software, running on Windows2000 operating system, in all aspects of automation engineering with user-friendly features. It is committed to enrich the production field of information technology to adapt to Windows software; its full range of units, on a wide range of machinery and equipment for optimal control.
1 Introduction Process
In this case according to the raw water quality conditions, the boiler water system requirements on the quality of water supply, boiler feed water treatment system process: the original raw water tank ???? ???? ???? original pump heat exchanger ???? ???? Multi Media Filters Activated Carbon Pre-filter ???? reverse osmosis desalination intermediate water tank ???? System ????Intermediate pump mixed ion exchange bed ???? ???? ???? demineralized water tank ???? desalination pump main plant. Another anti-laundering system, including filters, mixed bed ion exchange regeneration system, chemical dosing systems.
The original water tank for storage of raw water entering the system, its purpose is to regulate water flow changes, fluctuations in the system to prevent water running into the water to ensure the system stability and water quality.
The original water pump system for pretreatment of raw water to provide adequate flow and pressure.
The role is to water heat exchanger to maintain a certain temperature range, in order to facilitate efforts to ensure the stability of reverse osmosis systems.
The role of multi-media filter is to filter the raw water caused by small particles, suspended solids, colloids, organic matter and other impurities, and by dosing after the formation of alum, to ensure its water SDI (pollution index) ????è 4.
The role of activated carbon filter to remove low molecular weight organic matter in water, free chlorine, but also less water, odor, color and odor.
Reverse osmosis desalination system using reverse osmosis membrane pre-feature to remove the most soluble salt in water, colloids, organic matter and microorganisms.
Intermediate tank to withstand reverse osmosis water production side of the lower pressure, to avoid back-pressure reverse osmosis membrane Shoudao which cause unrecoverable damage, while the buffer stage ion exchange system as the valve after switching the pressure fluctuations, and through the middle of the water tank Kai Level Control reverse osmosis, stop running.
The role of intermediate pump up water for the OfficeManagement systems provide stable pressure and water.
The role of mixed bed ion exchange reverse osmosis water is retained for further removal of the ion.
Demineralized water tank for water storage capacity of the system, its purpose is to ensure the stability of the boiler water supply.
The role of desalination water pump to provide stability for the boiler system pressure and water.
Figure 1, boiler feed water treatment process
2 control system configuration and description
2.1 Overall control requirements and functional
Boiler water treatment requirements of automatic control system is the water treatment process control and automatic adjustment to make the treated water quality objectives to achieve the required range. Water control room PC in the company issued a directive, it will run during the current time the main working parameters (water quality parameters, flow, level, etc.), operating status and a certain period of time the main process and other information from the field on the curve Water reached the control room PC.
Functions as follows:
Control operation: In the water control room equipment can be charged with online real-time control.
Display Function: Graphics showing the scene in real time charged with the operation of equipmentCondition, and the state of the scene parameters.
Data management: changes according to different operating parameters and the importance of speed, the establishment of production history database, storing the raw data produced for the use of statistical analysis. Real-time database and historical data in the database for comparison and analysis, draw some useful empirical parameters, help to optimize control, and some of the parameters and results necessary to show to the real-time images and reports in to.
Alarm: When an analog (such as flow, conductivity, water level, etc.) measurements over a given area or volume of a switch (such as motor start and stop, the valve switch) occurs when the deflection can be different depending on the need to issue level of alarm. Another alarm can be diagnosed on the PLC.
Print function: can realize a variety of reports and trends in printing and print real-time events and alarms.
Figure 2 Boiler Feed Water Treatment Control System Configuration
2.2PLC program structure and implementation
2.2.1 The process works according to the characteristics of PLC programming in the form of the use of subroutine calls, not only program readable, and shorten the PLC scan cycle. With reverse osmosis desalination system control program, for example, reverse osmosis desalination system according to process requirements controlManufacturing process including reverse osmosis device Soft hand valve PC operating control (ROSoftoperation), reverse osmosis desalination system standby control (ROStandby), reverse osmosis desalination system operation control (RORunning) and reverse osmosis desalination system, irrigation control (RORinse) . The four working condition at the same time is unique, we can be made routine way, process is reverse osmosis (RO) call. Reverse osmosis process (RO) has and alarm procedures (Alarm), the pump control program (PumpControl), analog processing (AD003Setting), address translation process (IOConvert), level interlock program (LevelInterlock) such as a subroutine to be controlled main program (MainProgram) call, this greatly reduces PLC scan time, and control of clear thinking, the program readable. Only in PC operators on the issue simple commands like, soft hand exercise request, the request to run, rinse the request, and control procedures can be requested in accordance with the steps of the process control field devices.
Figure 3 control system part of the human-machine interface
<PALIGN = CENTER>
Figure 4PLC program structure diagram
For OMRONPLCC200HE Controller CX-Programmer programming software for simple instructions can be achieved only subroutine calls. For example:
Control of the main program in order to write the following, used to call "0" routine:
In the "0" in the first end subroutine writes the following directives:
In the "0" in the end of the subroutine to write the following instructions: For OMRONC200HEPLC the analog input module AD003, when from the instrument s 4 ~ 20mA signal is not within 4 ~ 20mA (below zero or exceed the range) when, AD003-site simulation module will convert into big money in 1000 ( 16-bit binary number) values, the corresponding host computer will be displayed in the analog full-scale value. Caused the error, caused by operator errorSolution. To avoid this phenomenon, we need to remove the program out of range (less than 0000 (4mA) and greater than 1000 (20mA)) interference signal. Specific instructions are as follows: For OMRONPLC exchange with the host computer s address, suggested that it be placed in control of the main program, the transfer of data into the HR area to keep the format.
The project uses the analog input module is OMRON s AD003, the actual use of the module channel number and types of analog signals can be flexibly configured PLC instructions. In this case each analog input module contains eight channels are configured to use state of the type configured as analog signal 4 ~ 20mA. In the analog processing (AD003Setting) in the written instructions are as follows:
3 Conclusion
The control system runs the system stable and reliable. Greatly improved labor productivity, the system effectively solve many problems in production, such as reducing the sudden failure of the production process and shorten production preparation time and repair time, reduced labor intensity, the power plant boiler water treatment has made a considerable economic and social benefits to achieve the energy conservation, energy purposes.