The main equipment of the air compressor station is a high-pressure air compressor. The traditional air compressor control is to operate the control panel by hand. It not only has poor safety and low work efficiency, but also cannot make real-time historical data enter the enterprise information management system. Therefore, in order to ensure safe and efficient operation of the air compressor, we have developed an air compressor station monitoring system with operational control and alarm protection.
1 compressed air production process, the natural free air is sucked into the air compressor cylinder through the air intake filter (some with the muffler function) under atmospheric pressure; the reciprocating piston acts to make the inhaled air volume The cylinder is shrunk from low pressure to high pressure, and then discharged through the exhaust valve and the pipe to obtain compressed air with a certain volume and pressure. Because the air passes through its volume from large to small, and its pressure changes from low to high, a certain amount of heat is generated. In order to improve the efficiency of the machine and reduce the energy consumption, the compressed air needs to be cooled, separated from the oil and solid impurities in the production process, and then sent to the gas cylinder for use. In some cases, there is a higher requirement for the quality of the compressed air, which requires post-treatment of the compressed air. Use dryers and filters to obtain high quality compressed air. The basic production process of compressed air is as shown.
2 Air compressor station monitoring system hardware design scheme An air compressor station has 8 high-pressure air compressors and 1 set of common drying and filtering equipment. The air compressor is a 4-stage high-pressure air compressor with many monitoring parameters and high requirements. In order to simplify the system structure, improve reliability and maintainability, we adopt a hierarchical monitoring system structure, each air compressor constitutes an independent LonWorks monitoring network, using embedded intelligent area controller as its monitoring host, 8 air compression The monitoring host of the machine is connected to the air compressor station monitoring host through Ethernet, and the public part device is directly connected to the air compressor station monitoring host. The hardware structure of the monitoring system is as shown.
In the system, the monitoring unit selects the 893-LM series intelligent controller based on LonW orks technology, which has complete hardware resources, including various digital modules, analog modules, DDC controllers, protocol conversion modules, network adapters, and regions. Controllers, etc., can meet the requirements of various application fields, and have been specially designed for waterproof, moisture-proof, anti-electromagnetic pulse interference, etc., and have passed the test certification of the national authoritative testing institutions, especially suitable for harsh environments.
This monitoring system selects 4 types of hardware products; a) LM 1102: 8 general-purpose analog input modules, mainly used for the collection of analog input signals such as temperature and pressure.
b) LM 1203: 8-channel digital input + 8-channel digital output module, mainly used for monitoring and controlling switching signals such as valve switches.
c) LM - 1201: 8-way switch signal input module, mainly used for monitoring the working status of public parts such as dryers.
d) LM - 1502: Embedded area controller, as the monitoring host of each air compressor, mainly collects real-time data and status of each module, and completes alarm processing, equipment control logic and protection functions, such as delay switch valve, etc. .
3 air compressor station monitoring system software design 3. 1 iFix software introduction IPC software is developed using iF ix 3. 5. iFix is ​​a fully integrated industrial automation real-time monitoring software development platform that has been a leader in industrial automation software. It contains a number of powerful graphical tools that allow users to quickly and intuitively build process-oriented real-time windows. As a powerful industrial automation control configuration software, its basic functions are data acquisition and data management. Data collection refers to the ability to obtain data from the field and interact with field devices through I/O device drivers; data management refers to iFix's ability to process and manipulate data, including process monitoring (graphic display), supervisory control, alarms, reports , data archiving, control, etc. At the same time, iFix has a complete security system, including user-based security system and system security application. User-based security system can protect iFix files, important programs, operation display screens and recipes, database modules.
System security applications include both security configuration and login. When a user logs in, he or she needs to enter a name and password. After the identity is confirmed, the operation within the permission range can be performed.
3. 2 main functions of software design and implementation The software design of the monitoring system has powerful monitoring, control and management functions, which can not only display various data of the field monitoring equipment in real time, but also visually represent the changes of the data in an animated manner. Come out and complete the alarm, trend curve, group display, history, report printing and other functions. Through this monitoring system, users can timely master the operation of equipment in the air compressor station and improve the management level of the system.
3. 2. 1 Data Acquisition In order to ensure the safe and effective operation of the air compressor station, the system collects the following parameters in real time: a) air compressor parameters: level 1 exhaust pressure; level 2 exhaust pressure; Level 3 exhaust pressure, temperature; Stage 4 exhaust pressure, temperature; cooling water pressure, outlet temperature; lubricant pressure, temperature; aftercooler exhaust temperature.
b) Common parameters: 1 high pressure dryer pressure, temperature; 2 high pressure dryer pressure, temperature; 1 high pressure gas cylinder pressure; 2 high pressure gas cylinder pressure; compressed air dew point; cooling water network pressure, temperature.
The staff also needs to monitor the operation of the air compressor station equipment and control the operation of the equipment, such as the working status of the unit, the sewage valve, the dryer, whether the air compressor is in manual or remote control.
3. 2. 2 The alarm system sets the lower limit and upper limit alarm values ​​for the lube pressure and cooling water pressure data blocks, and sets the upper limit alarm value for each block of cylinder exhaust pressure and temperature. When the data collected by the system exceeds the set limit, the program will activate the alarm function to prompt the user until it is confirmed. At the same time, alarm information such as alarm time, alarm name, and alarm cause can be recorded in the alarm history database for later reference by the user.
The system also indicates the quality of the data by changing the foreground attribute of the data connection object. For example, in normal operation, the analog quantity data is displayed in green, the upper limit of the parameter is displayed in red and light red, and the lower limit is yellow and light yellow. Flashing display. In addition, after the alarm is triggered, the preset operation command can be started to realize the monitoring of the site. For example, when the fourth stage exhaust pressure occurs, the shutdown protection is immediately performed, and the specific fault location is diagnosed by the monitoring host. Its solution.
3. 2. 3 screen display In order to visually, vividly and comprehensively monitor the control process of the equipment in the whole air compression press station, we designed the total system diagram, gas flow chart, sewage flow chart, network structure diagram and so on. Each screen can be easily switched to each other with a mouse or keyboard. In the picture, we set the dynamic attribute of the running indicator indicating the working status of the device, so that the user can understand the running status of the field device by observing the change of the running indicator color; define the dynamic data link in the static picture, and the running data constantly It is refreshed and displays real-time data, which is convenient for users to observe and analyze in real time. It uses the icon set provided by iFix itself to complete the drawing of the gas path and sewage flow chart of a single unit; using the position and visual experts to indicate the direction of the gas path The arrow is set to achieve the dynamic effect of the pneumatic process; dynamic properties are set for all controlled objects, such as changes in the state of the valve switch will cause its color change. In addition, a control button for switching the monitoring screen and artificially controlling the running state of the hardware device is also set in the screen, and the user can write a script in the event of the button to realize the switching of the screen and the change of the device state. The air compressor air circuit flow is as shown.
3. 2. 4 control function 1) Single-unit variable frequency start-up control The single air compressor in the air compressor station adopts the frequency conversion start mode. Two inverters are arranged on site, one for each device, one for each standby, and the air compressor is controlled to start in turn. When one starts, the other air compressors cannot be started, and after a certain period of time (60 s), other air compressors can be started. The single-machine variable frequency start control program is as shown.
2) Stand-alone fault shutdown protection Single-machine faults can be classified into one type of fault and the second type of fault according to severity. When a fault occurs in the unit, the unit needs to be stopped immediately (emergency stop), and when the second type of fault occurs, the normal stop can play the role of protecting the unit.
One type of fault includes: low oil pressure, low cooling water pressure, high stage 4 exhaust pressure, and motor overload. The second type of fault includes: high oil pressure, high oil temperature, high cooling water pressure, high exhaust gas temperature of the third stage, high exhaust gas temperature of the fourth stage, high exhaust pressure of the first stage, high exhaust pressure of the second stage, The third stage has high exhaust pressure, dryer failure, and dew point meter failure. Stand-alone shutdown and protection control procedures are shown.
The system can remotely or manually control each controlled device in the air compressor station. The user only needs to click the mouse on the monitoring screen to complete the start, stop, emergency stop and reset control of the on-site air compressor.
When the air compressor is shut down due to a fault, the reset switch must be pressed before the unit can be started. During the unit control process, each unit has the functions of interlocking start-up loop interlock, emergency fault stop and interlocking of single-machine variable frequency start loop and power frequency operation loop to ensure the safe operation of the equipment.
4 Conclusion Because the system uses the 893 LM series intelligent controller with good stability and high reliability, the upper computer software adopts the powerful and user-friendly iFIX configuration software, and flexibly uses various kinds in the implementation process. Skills, so achieved good results in the run. It not only monitors the production process of air compressors and key indicators such as pressure and temperature in real time, but also provides shutdown protection for faults to ensure safe operation of equipment. In the future, further software development for fault diagnosis technology, such as when a fault occurs, can be diagnosed by the host to diagnose the cause and solution of the specific fault, which will be a promising development direction.
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