Design of Automatic Control System of Air Compressor Based on PLC
Design of automatic control system of air compressor based on PLC Li Guodong Liaocheng Technician College, Shandong Liaocheng 252000PC machine will transmit the system operation parameters set to PLC, PLC compares the collected wind package pressure with the set value, after intelligent control operation The control signal is sent to the inverter to control the start, run and stop of the inverter.
The 4L-20/8 piston air compressor is a device that uses an electric motor to compress a gas in a compression chamber and to have a certain pressure on the compressed gas. Due to the structural principle, the air compressor itself has obvious technical weaknesses. To this end, this paper introduces PLC and inverter to improve the technology and improve system performance.
The programmable controller used in this system adopts FX2N NON5 produced by Mitsubishi Corporation of Japan as FX2N-8AD type analog input module, each module has 8 analog input channels, numbered CH1CH8. Total 6x8 two 48 channels, For 47 analog signal inputs. The buffer register number is 0BFM31BFM, and the buffer register corresponding to each channel is 5BFM12BFM in order to store the sampling data, the buffer register is read by the FROM instruction of the PLC, and the read data is written into the data storage unit of the PLC. At this point, the A/D conversion is completed. Among them, each special function module occupies 8 I/O points, occupying 6x 8 2 48 X input points.
N6 is an FX2N-8DA analog output module with 8 analog output channels, numbered CH1CH8. Total lx8=8 channels for 6 analog signal output. The buffer register corresponding to each channel is 5BFM12BFM in order to store the output signal of the write buffer register through the TO instruction of the PLC, and thus the D/A conversion of the signal is completed. Among them, each special function module occupies 8 I/O points, occupying 1x 8 2 8 Y output points.
N7 is the PID process control module of PLC. Each module can control multiple closed loops. There are 6 PID control objects in this system. Therefore, this module only needs to implement control through 6 PID commands in the PLC program. They are: 4V20mA output control between 4-5 ends of VVVF inverter, 5 electric control valves for controlling the inlet circuit of the main engine.
The inverter used in this system adopts FR-F740-S450K-CHT, 450kW, 3 Mitsubishi inverter produced by Mitsubishi Corporation of Japan; a total of 11 kinds of signals are collected in the operation of this system, and 5 air compressors plus 1 wind package total 47 analog inputs. The pressure sensor is selected for easy installation and accuracy. The temperature signal range of the system with excellent performance is 0°160°, so the temperature sensor adopts the original PT100 standard resistance temperature sensor. The PT100 is a platinum resistance temperature sensor that is suitable for measuring temperatures between 60 ° C and +400 ° C.
In order to effectively control the water pressure of the air compressor main engine, the system controller adopts PID control. The selected electric valve of the equipment adopts Danfoss design electric control valve produced by Beijing Weijiangyuan Technology Development Co., Ltd.
There are five air compressors of the same type in the system. The pressure and temperature signals of the air compressor are transmitted to the analog input module of the PLC through the standard 4mA20mA signal and resistance signal through the standard pressure sensor and the thermal resistance to realize the analog signal acquisition. The on-site switching signal is transmitted directly to the digital input module of the PLC via the cable.
After the PLC collects, transforms and stores the signal, it communicates with the host computer through the SC-09 programming cable, and sends the converted signal to the PC for real-time display. At the same time, the PC transmits the set system operation parameters to the PLC. PLC compares the collected wind package pressure with the set value, and sends the control signal to the inverter through the intelligent control operation to control the start, run and stop of the inverter. .
The system has a total of 12 switch inputs, 42 switch outputs, 47 analog inputs, and 6 analog outputs. ) Control of the air compressor) First read the wind pack pressure signal and compare it with the set value to determine which range it is. If the wind pressure is in the normal range, the first power frequency, the second frequency conversion; if it is lower than the normal range, the first, the second power frequency, and the third frequency conversion.
If it is higher than the normal range, only the first frequency conversion is started. After 8 hours, the wind pack pressure signal is read and compared with the set value to determine which range it is. If the wind pressure is in the normal range, the fourth power frequency, the fifth frequency conversion; if it is lower than the normal range, the third, fourth power frequency, fifth frequency conversion. If it is higher than the normal range, only the fourth inverter will be started. In another 8 hours, starting from the first, second and third sets, the cycle is repeated, ensuring sufficient rest and heat dissipation of each machine.
(2) While the program determines the number of working machines and ensures the rotation, the program also performs PID intelligent control based on the read wind pressure signal to determine the given frequency of the inverter.
After the transmitter reads the water pressure of the main unit, the PLC compares it with the set value. If it is within the safe range, it performs PID adjustment and adjusts to the target value. Otherwise, an alarm is stopped.
The first and second terms are the starting conditions of the sth, and after being compared with the set value, if they are within the normal range, the start is allowed. On the contrary, the alarm is stopped. After comparing the third item with the set value, if it is in the normal range, it will be put into the power-off shutdown circuit after 5s. After comparing the fourth, fifth and sixth set values, if it is in the normal range, it will be put into the power-off shutdown circuit after 180s.
Go to page 141 L "Technology Communication" Application Technology 1 Construction Joint Waterproof Treatment Construction joints usually have two types of vertical joints and flat joints. In waterproof construction, firstly, within 4h12h after the secondary lining, the wire brush is used. Rinse the bristles at the seams or rinse with high pressure water until the surface stones are exposed. Before the new concrete is poured, clean the joints and keep them moist. First, brush the cement slurry twice, and then lay a 10mm thick cement mortar (with the original mix ratio, remove the coarse aggregate, or add the expansion agent). . After 5 hours, refill with sputum.
The structural ring-oriented construction joint treatment method is: a buried water stop belt. The arch wall and the invert arch are buried in the boundary between the light and dark holes. The water-stop belt is made of steel, and the rubber waterstop is used.
The longitudinal construction joint treatment method is as follows: the concrete contact surface is coated with water-swellable water-stopping glue, and an externally-applied waterstop is provided.
The self-made assembled steel mold or wooden mold joint head plate needs to be arranged according to the thickness of the lining and its form. The width of the single steel mold should be one-half of the thickness of the lining.
At the same time, the prepared steel molds can be numbered according to the order in which they are installed. After waiting for the full-section hydraulic steel mold lining trolley to be in place, install the steel die stop plate according to the numbering sequence. The rubber stop bar is clamped along the tunnel direction in the middle of the stop plate, and the U-shaped card is fixed at both ends. .
5.2 Deformation joint waterproof treatment The deformation joint is produced because the structure with different stiffness will produce certain uneven settlement after the different pressures, and then the structural gap will occur.
The deformation joint of this standard section adopts the slow expansion type water-swellable rubber waterstop to stop the water. The joint of the outer edge of the lining of the arch wall and the waterproof coil is sealed with polysulfide sealant, and the inner edge of the lining is sealed with polysulfide within 3cm. Glue plugging, U-shaped galvanized steel plate water box is set in the outer 2cm range, and the other gaps are filled with asphalt wood board; in order to reduce the settlement on both sides of the inverted arch deformation joint, 4>5 pairs in the secondary lining of the inverting arch part The layer is made of shear-resistant steel, and the distance between the reinforcing bars is 50cm. The inverted arch deformation joint is filled with caulking material.
After the initial setting of the longitudinal horizontal construction joint pouring wheel, before the final setting, a flat and smooth groove is rolled on the base surface according to the specifications of the water stop strip. Then, the water strip is stopped, a part of which is exposed to the plane of the construction joint, and then the concrete of the first stage is poured. Place half of the rubber waterstops in the concrete lining.
Before the concrete is poured, the horizontal mortar is laid on the base surface with 25mm30mm and the cement mortar with the same number. The vertical construction joint is controlled to have a certain distance from the base surface, and the base surface is evenly and fully vibrated. With the new pouring ç ¼ ff (upper page 155) ft 4mA20mA current input is controlled by the PLC's PID module. When the pressure sensor detects the wind pack pressure to determine the number of air compressor worktables, perform 10 calculations, 1 £, 10 modules output 411211 current to the 4-5 frequency adjustment terminal of the inverter, and change by adjusting the output frequency of the inverter. The air compressor drives the speed of the motor to achieve the purpose of adjusting the wind pack pressure to a standard value (.8 mp). The main unit inlet water pressure electric regulating valve PID control air compressor main engine inlet water pressure adjustment using PLC's PID module control.
When the pressure sensor detects the host water pressure is on. When between 4MPa1.2MPa, through the PID calculation, the PLC's PID module outputs 4mA20mA current to the ESC valve, and the inlet water is changed by adjusting the opening degree of the valve to achieve the purpose of adjusting the inlet pressure.
25mm30mm cement sand paddle, the new and old wheels are well combined.
2) The circumferential construction joint first needs to be placed with a back-mounted waterstop, and then the back-mounted waterstop is fixed at a certain position. After the fixing, the buried waterstop is placed in the middle. After the position is properly placed, it needs to be pasted or welded and positioned. Finally, the template is used to fix it. One end is equipped with a pouring wheel, and the other end is protected by box-shaped wood. After the strength reaches a certain strength, the template can be removed. Box protection.
The technical parameter for manufacturing the assembled steel die stop plate is that the width of the steel die should be 1/2 of the thickness of the lining. In the middle of the stop plate, the rubber waterstop is used, and the groove type positioning card is used at both ends. fixed. The rubber waterstop is fixed on the main rib or anchor of the lining by means of a positioning rib. A half of the rubber water stop is reserved for pouring in the next cycle wheel lining.
2.5.4 ç ¼Perfusion and vibrating at the deformation joints For the wheels on both sides of the vertical upward waterstop, it is necessary to strengthen the vibrating to ensure the compaction, and at the same time, the waterstop and the air bubbles on the wheel surface are required. Extrusion is carried out to ensure that the waterstop and the crucible can be tightly and firmly joined. For horizontal waterstops, wait for the water stop to fill the bottom of the waterstop and vibrate it. Then place the waterstop in a parallel position and press out a certain amount of slurry. Finally, water the upper wheel of the waterstop. .
In order to avoid affecting the quality of waterproofing, the kraft paper separator can be used to isolate the sealant on the outside of the deformation joint. However, it should be noted that the side wall of the deformation joint and the sealant are closely adhered to each other, so that the seal is tight, so as to prevent the seal. The occurrence of water leakage. The caulking quality is dense, and the surface is not allowed to have defects such as cracking, detachment, slippage, sagging, hollowing, collapse, etc. Before filling the sealant, remove the floating raft, dust, and water in the tank, and bond the base surface of the sealant. It must be smooth, dry, clean and free of any pollution.
3 Conclusion In the process of waterproofing and drainage construction of Daping Tunnel, effective control measures are taken to ensure that the structure does not seep water, there is no wet stain on the surface, and it can reach the level of first-grade waterproofing level without leaving the target.
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