One, foreword
Air compressor referred to as compressor or air compressor. With the development of mechanization, it is widely used in various fields. In the new period, to strengthen the regular maintenance and maintenance of the air compressor is an important guarantee for its normal operation.
Two, screw compressor working principle
Screw compressor unit is mainly composed of a pair of meshing Yin and Yang rotor and shell, its working principle is similar to reciprocating compressor, is a volumetric type, but the working mode has changed. If the cavity of the negative rotor groove and shell is compared to the cylinder of the piston compressor, then the spiral teeth of the positive rotor sliding in the negative rotor groove is equivalent to the reciprocating movement of the piston.
In a screw compressor, compressed gas is meshed with each other by two rotors with helical grooves (Yin and Yang rotors), the axes of which are parallel to each other, mounted in a case of high strength cast steel. The inlet and exhaust ports are arranged on the diagonal positions of the two end faces in the shell, and the inlet end of the rotor is provided with thrust bearings to limit the axial movement of the rotor. The grooves of the Yin rotor mesh with the Yang rotor, and driven by the Yang rotor, so that the gas from a port of the rotor into, compressed from another port discharged. The working process is generally divided into three stages: suction process, compression process and exhaust process.
Analysis of automatic shutdown during operation
1. Power supply network factors
The machine is equipped with undervoltage relay, fault-off relay and other safety protection devices. When the power grid voltage is below 83% of the rated voltage (420V) or the phase sequence of the power supply is incorrect or the three-phase power supply is out of phase, the unit will automatically trip and stop.
2. Exhaust temperature is too high
(1) Poor environmental ventilation. When there are wall obstacles near the air compressor affecting air circulation, it will cause poor heat dissipation; When there is a similar heat source near the air compressor, it will also affect heat dissipation; When the side doors are open, the cooling effect is also significantly reduced. These three situations will cause air compressor temperature rise and automatic shutdown.
(2) If the cooling oil oil level is too low and the cooling oil and oil filtration and oil and gas separation components are too dirty, they should be replaced or cleaned according to the situation.
(3) The fan belt is too loose or broken. Adjust the belt tensioner or replace the belt.
(4) the radiator appearance is too dirty, resulting in reduced heat dissipation effect and poor air circulation: the radiator inside is too dirty and partially blocked, causing poor cooling oil circulation, the radiator should be cleaned at this time.
(5) The temperature control valve fails. The valve is always in the open state, part of the cooling oil directly back to the compressor, not all through the radiator, should be repaired or replaced according to the standard temperature control valve.
(6) The oil cut-off solenoid valve cannot be opened or its opening is insufficient. At this time, it should first detect whether there is voltage at both ends, if so, further detect whether there is a card fault in the mechanical part and eliminate it.
3. Exhaust pressure is too high
The rated exhaust pressure of the machine is 12MPa. When the pressure is too high, the butterfly valve mechanism should be checked first for mechanical failure and whether it is stuck in the maximum opening position. If there is, check whether the loading solenoid valve leaks or is broken. If it is normal, further check the upper and lower limits of the pressure switch and adjust it to the rated range.
Iv. Daily maintenance and treatment of air compressor
1. Daily maintenance and treatment of air intake and shortage
(1) The compressor speed reduction to reduce the exhaust volume: because the exhaust volume of the air compressor is designed according to a certain altitude, suction temperature and humidity, especially in high altitude installation must be strictly in accordance with the instructions for correct installation, every period (60 days or so) should detect the intake pressure and exhaust volume.
(2) Scaling and blockage of the intake filter reduces the exhaust volume, and the filter should be cleaned regularly.
(3) the cylinder, piston, piston ring wear serious, out-of-tolerance, so that the relevant gap increases, the increase of leakage, affecting the displacement. Belong to normal wear, need to replace wearing parts in time, such as piston rings. It belongs to incorrect installation and improper clearance. It should be corrected according to the drawings. If there is no drawing, experience information should be obtained.
(4) Check the tightness of the stuffing box and whether the stuffing box itself is qualified when it is manufactured; Secondly, in the installation, pay attention to the neutral piston rod and stuffing box center; Generally, lubricating oil is added to the stuffing box, which can play the role of lubrication, sealing and cooling.
(5) the influence of compressor suction and exhaust valve failure on the exhaust volume. This problem may be due to one is manufacturing quality problems, such as valve warpage; The second is due to the valve seat and disc wear serious air leakage. In daily testing, the flatness of the valve plate and the gap between the valve seat and the valve plate should be measured so that it is in the normal range.
(6) The spring force of the air valve is not well matched with the air force. The elastic force is too strong to open the valve disc slowly, the elastic force is too weak to close the valve disc in time, which not only affects the gas volume, but also affects the increase of power, as well as the life of the valve disc and spring. Check spring preload pressure and working pressure regularly.
2. Key points of daily maintenance to avoid abnormal sound
(1) When the compressor is installed, pay attention to the clearance of the cylinder legs and the stress of the bolt to make it well supported.
(2) Regularly test the clearance of the compressor cylinder (generally, the clearance coefficient of the low-pressure cylinder of large and medium-sized compressors is less than 8%, and the clearance coefficient of the high-pressure cylinder can reach about 12%), regularly test the position of the piston at the upper and lower dead center, and timely adjust to ensure its normal operation.
(3) Check the connection of crankshaft shingle, nut, connecting rod bolt, crosshead bolt, and shaft diameter, exhaust valve plate, and spring force of valve spring in crankcase regularly.
(4) Detected due to large flywheel imbalance caused by balance iron, on the flywheel into action balance correction.
3. Measures to avoid compressor overheating
(1) Check the supply of cooling water.
(2) Check whether the oil pressure of the oil pump is normal, whether the oil circuit is blocked, whether the filter is blocked, and clean smoothly.
(3) the following methods are used to solve the heat problem of the air valve: the air valve has been changed several times, and the leakage experiment has been carried out before the installation of the air valve, which fully meets the installation technical requirements. When it is installed on the piston compressor, the heat problem still exists, thinking that the spring force is too large, the stroke volume of the cylinder is adjusted. The application of light transmission method to check the piston ring and cylinder with the application of the inner diameter micrometer cylinder roundness and cylindricity; The center line of crankshaft and the center line of piston rod and slideway were measured by drawing method, and the results all met the technical requirements. But the temperature of the cylinder is still high, and the cylinder rod has been calibrated for cylindricity and bending, and finally meets the technical requirements of installation.
4. Ensure the normal daily maintenance of pressure
(1) regularly detect the gas valve, liquefied gas contains light oil adsorption on the valve, so that the valve spring and valve plate can not work normally, affecting the exhaust volume of the compressor. The air valve should be cleaned or replaced regularly.
(2) Attention should be paid to the installation of the compressor. The interface between the gas ring and the oil ring should be installed incorrectly to avoid leaking liquefied gas.
(3) The piston in the cylinder reciprocating movement for a long time, the light oil in the liquid gas into the piston ring groove of the piston, firmly stuck on the piston ring, completely lost elasticity, the piston ring does not seal, so the piston ring should be cleaned or replaced regularly.
5. Daily maintenance of compressor cooling system
To achieve good cooling effect, it is necessary to ensure that the water quality of cooling water is within the scope of national standards to reduce scaling and blockage of the cooling system. At the same time, it is necessary to clean up the dirt of the cooling system regularly, so as not to reduce the circulation area of cooling water, hinder the heat exchange and reduce the cooling efficiency. Circulating water corrodes the metal surface, especially the cooling tube. The usual treatment method is to check the leakage part through pressure test, and use the method of blocking welding tube to deal with. At present, some manufacturers use corrugated tube as the tube of heat exchanger within 2.0MPa pressure level. The heat exchange effect is obvious when used. Under the same conditions, the volume of heat exchanger can be reduced, and its own self-descaling ability is recommended as a heat exchange.
Five, advice,
Air compressor is the lifeblood of factory production. Regular maintenance and maintenance of air compressor is the premise to ensure its normal operation. Equipment maintenance should be to implement the principle of "prevention first" should be the equipment failure in the bud, its main task is to prevent the loose fitting and not normal wear and tear, supervise operator according to the regulations on the use of procedures the correct use of equipment, to prevent accidents, prolong the service life of equipment and overhaul cycle, ensure the safe operation of the Production equipment in optimum condition for production.
Sixth, concluding remarks
To sum up, compressor is the core of factory operation. Therefore, we should strengthen the daily maintenance of the compressor to ensure its normal operation.