piston compressor
Working principle of piston compressor
Piston compressor is one of the earliest compressor designs, but it is still the most common and very efficient compressor. The piston compressor makes the piston move forward in the cylinder through the connecting rod and crankshaft. If only one side of the piston is used for compression, it is called single-acting type. If the piston is used on both sides, it is called double-acting type.
Piston compressors are widely used and have almost no restrictions. It can compress air and gas, and hardly needs any changes. Piston compressor is the only design that can compress air and gas to high pressure, which is suitable for breathing air and other purposes.
The configuration of piston compressor can range from single cylinder configuration suitable for low pressure/small capacity applications to multi-stage configuration that can be compressed to very high pressure. In a multistage compressor, the air is compressed in stages and the pressure is gradually increased.
Compression ratio:
Compai piston compressor series has a power range of 0.75 kW to 420 kW (1hp to 563hp), and produces working pressure of 1.5 bar to 4 14 bar (2 1 to 6004psi).
Its typical uses are:
Gas compression (compressed natural gas, nitrogen, inert gas, landfill gas)
High-pressure air (breathing air for underwater respirator cylinders, seismic surveys, pneumatic circuits, etc.). )
Keywords PET bottle blowing, engine starting, industry
Rotating screw
Working principle of rotary screw compressor
Screw compressor belongs to positive displacement compressor, and its piston is in the form of screw. This is the most important type of compressor in use today. The main components of screw compression element are convex rotor and concave rotor, which move close to each other, so that the volume between them and in the cavity is gradually reduced. The pressure ratio of the screw depends on the length and shape of the screw and the shape of the exhaust port.
The screw element is not equipped with any valve, and there is no unbalanced mechanical force. Therefore, it can work at high shaft speed, and it can give consideration to both large flow and small size.
Compression ratio:
Compai rotary screw compressor series has a power range of 4 kW to 250 kW (5 to 535 HP) and produces an operating pressure of 5 bar to 13 bar (72 to 188 psi).
Its typical uses are:
Food, beverage, brewing
Military, aerospace, automobile
Industry, electronics, manufacturing, petrochemical
Medical treatment, hospitals, pharmacies
Instrument gas source
Rotating skateboard
Working principle of rotary vane compressor
The vane compressor adopts traditional mature technology and is directly driven at a very low speed (1450rpm), which has unparalleled reliability. The rotor is the only part that runs continuously, and there are several grooves cut along the length direction on it, and sliders that can slide on the oil film are inserted in it.
The rotor rotates in the stator of the cylinder. In the process of rotation, centrifugal force throws the blade out of the groove, forming a separate compression chamber. Rotation reduces the volume of the compression chamber and increases the air pressure.
The heat generated by compression is controlled by injecting pressurized oil.
High-pressure air is discharged from the exhaust port, and the residual oil is removed by the final oil separator.
Compression ratio:
The power range of China Comac vane compressor is 1. 1 kW to 75 kW (1.5 to 100 HP), and the working pressures generated are 7 to 8 and 10 bar (10/kloc-0).
Its typical uses are:
OEM, printing, pneumatic
Laboratories, dentistry, instruments
Machine tools, packaging, robots
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Fault phenomenon:
1, winding short circuit, open circuit, winding touching the casing grounding: these faults are all caused by the motor part of the compressor, and the fault phenomenon is that the power supply is normal, and the compressor does not work when the open circuit is broken; In case of short circuit and shell collision, the protector acts after being energized, or the fuse is blown; It should be noted that if the winding turns are slightly short-circuited, the compressor can still work, but the working current is very large and the compressor temperature is very high. Before long, the thermal protector will start. Winding short circuit and winding contact bushing grounding can generally be checked by multimeter; Winding short circuit, especially slight short circuit, is not easy to judge because of the small resistance of the winding itself, and it should be judged according to the measured current.
2. Compressor shaft locking and cylinder sticking: If the compressor loses oil or impurities enter, it will often cause shaft locking or cylinder sticking. The fault phenomenon is that the compressor doesn't work and the protector acts after power-on.
3. The compressor suction and exhaust valves are not closed properly: the compressor suction and exhaust valves are damaged, and even if the refrigerant is sufficient, the system cannot establish high and low pressure or it is difficult to establish qualified high and low pressure, and the system does not cool or the cooling effect is poor.
4. Vibration and noise of compressor: This kind of problem often occurs in maintenance work, and generally has little influence on refrigeration performance, but it will make users feel abnormal, which is often caused by the collision between the pipeline and the casing, the loosening of the compressor fixing bolt and the fall-off of the damping block.
5. The thermal protector is damaged: the thermal protector is an accessory of the compressor, and the fault is generally an open circuit or a smaller working temperature point. Open circuit will cause the compressor not to work; When the working temperature point becomes smaller, the compressor will stop after working for a period of time, and so on. This problem is often easily confused with a slight short circuit between windings. The difference is that the working current is normal when the thermal protector is damaged, and the current is too large when the winding is short-circuited.
Maintenance method:
There is something wrong with the compressor motor, the compressor suction valve and exhaust valve are not closed properly, and the thermal protector is faulty, so it should be replaced.
The compressor shaft locking and cylinder sticking faults can be repaired first, and the specific methods are as follows:
(1) tapping method:
After starting, knock the lower half of the compressor with a wooden hammer to make the stuck parts inside the compressor vibrate.
(2) Capacitance starting method:
You can use a capacitor with large capacitance to access the circuit to start.
(3) High-voltage starting method:
A voltage regulator can be used to boost the supply voltage and then start it.
(4) Pressure relief method:
After all refrigerant is discharged, start the system.
If none of the above methods work, we have to replace them.
When dealing with the vibration and noise of the compressor, check and separate the parts that collide with each other; Check and tighten the anchor bolts of the compressor. Note that the anchor bolt of the compressor cannot be completely screwed to the end. The design requires that a clearance of about 1 mm must be maintained. During the maintenance, the compressor anchor bolt is screwed to death and the compressor vibrates violently. To check whether the damping block falls off and the paste is firm *, you can also try to add the damping block and try the specific position by trial and error. If it works there, stick it there.
Judgment and treatment of compressor fault;
1. How to identify the three terminals on the totally enclosed compressor shell? The resistance between running terminal (R), starting terminal (S), male terminal (C) and RS is greater than that between SC and RC. The resistance between RS is equal to the resistance between SC and RC. It can be judged by the above laws. It should be noted that the terminal resistance values of three-phase compressors are equal. 2. How to judge the short circuit of compressor motor winding? Select R× 1 with a multimeter, and measure the resistance of the compressor motor winding at C-R or C-S after zero adjustment ... If the measured winding resistance is less than the normal value, it can be judged that the winding is short-circuited. For a three-phase motor, use two probes to contact two of the three terminals respectively. If the resistance values measured three times are consistent, the winding is in good condition. If the resistance value measured twice is infinite, it means that a group of windings are open; If all three tests are infinite, at least two groups of windings are open; If the resistance measured in two of the three measurements is significantly smaller than that measured in the other one, it indicates a short circuit. 3. How to judge whether the compressor motor touches the casing and is grounded? When the compressor motor contacts the casing, the insulation inside the winding wire is damaged and collides with the compressor casing, forming a short circuit. When this fault occurs, the fuse may blow and the compressor motor will not run. Check the way the shell touches the ground, or use the resistance of the multimeter. First zero, then put a pen tightly against the common point, put another iron pen on the exposed metal part of the compressor process pipeline, or set up a small piece of paint on the shell plate for measurement. If the resistance value is very small, it can be judged that the winding or internal wiring is in contact with the shell and grounded. 4. How to judge the compressor motor winding open circuit? Adjust the multimeter to R× 1, then zero, connect the probe to the terminals of any two windings, and measure their resistance values. If the winding value is infinite (∞), that is, there is no conduction between the terminals of two windings, it can be judged that the winding is open. 5. The compressor cannot be started. (1) Check whether the compressor is overloaded, the pressure switch and the overcurrent protector are tripped or damaged. ⑵ Check whether the indoor temperature sensor and the tube temperature sensor are open or have poor contact in the cooling state and short-circuited in the heating state. (3) Check whether the compressor relay is engaged with a multimeter. (4) Wrong wiring. 5] compressor open circuit or short circuit. [6] The compressor capacitor is damaged. Once the AC contactor is broken. ⑻ Check whether the corresponding pin in 2003 has OV output. If there is OV, it is a relay problem. If there is no OV output, but 1 1.5V output, check whether the corresponding pin of the main chip has 5V output. If so, it was a problem in 2003. If not, it is the main chip problem. 6. The compressor is overheated, which causes it to stop soon after starting (protector action). Please check whether it is: (1) insufficient or excessive refrigerant. Please make up the leakage and vacuum, fill up the refrigerant or release excessive refrigerant. ⑵ Capillary components (including filters) are blocked and the suction temperature rises. Please replace the capillary assembly. (3) Internal leakage of the four-way valve constitutes misoperation. Confirm the damage before updating. (4) There is a fault in the compressor itself, such as short circuit, open circuit and grounding of the casing. Replace the compressor after inspection. 5] protection relay itself is faulty. When the compressor is not overheated, please use a multimeter to check whether its contacts are conductive. If not, please replace it with a new protector. When replacing compressors 5528 and 5532, it is necessary to check the starting capacitor and starting relay (if one of them is damaged, both must be replaced at the same time). [6] If the high pressure is too high, the pressure relay will act. Please analyze the reason and eliminate it according to the situation. Once the condenser is poorly ventilated or short-circuited, please remove obstacles on the outdoor side and clean the condenser. ⑻: Non-condensable gas (such as air) is mixed in the system. Please vacuumize and refill. Pet-name ruby compressor running current is too large, please find out the reason. ⑽ The ambient temperature of the outdoor unit is too high, please stay away from the heat source and avoid the sun exposure. ⑾ compressor cylinder or shaft. The rubber hammer or wood block on the hammer pad can be used to vibrate the compressor shell, or the compressor can be started to run by parallel capacitor and no-load fluorine discharge, but if it fails, the compressor should be replaced. ⑿ The vapor-liquid valve is not fully opened. 7. The judgment of low compressor efficiency. The reason for the low efficiency is that the moving parts are worn, which makes the fit gap too large, or the intake and exhaust valves are broken, or the asbestos plate of the cylinder pad is broken. Generally speaking, the exhaust pressure drops, the suction pressure rises, and the temperature of the compressor cylinder head and the suction and exhaust cavities is too high. If a low pressure gauge and a high pressure gauge are connected to the suction and exhaust pipes, when the exhaust pressure is above 0.6Mpa, the suction pressure still stays at 0Pa or the vacuum degree can only reach above 52.5Pa, so it can be judged that the compressor is inefficient. 8. Judgment of compressor loss of working ability. Refers to the normal operation of the compressor, but it has lost its suction and exhaust functions. First, cut the scissors of the compressor filling process pipe. If a large amount of R22 is ejected, it can be judged that R22 is not cooled due to leakage. At this time, the suction pipe and exhaust pipe of the compressor can be melted with a welding gun, and the compressor can be removed and started separately. After the compressor is running, you can test the suction and discharge pressures of the compressor by hand. First, try whether the suction port sucks in air, then try whether the exhaust port exhausts air, and block the exhaust port by hand. If the pressure is not very high, or even there is no exhaust, it can be considered that the compressor has lost its working ability. Because in normal operation, the compressor outlet cannot be blocked with fingers. 9. Why is the compressor motor current too large? (1) The compressor is short-circuited between turns, but it is not enough to blow the fuse. ⑵ The "secondary friction" of the compressor destroys the smoothness of the friction surface and increases the power and current of the compressor, but it has not reached the degree of "shaft locking" or "cylinder locking", which makes the compressor unable to rotate. You can use a multimeter to check the insulation resistance of the compressor motor to the ground. In general, it should be above 2M Ω. If it is significantly smaller or close to zero, it means that it has been short-circuited. If the insulation resistance to ground is normal, check the resistance values of starting and running windings. If the turns are short-circuited, the running current will increase. 10. What is the reason for the difficulty in starting the three-phase compressor motor? A. the power supply voltage is too low. B. short circuit of compressor motor winding. 1 1. How to eliminate the faults such as slow speed, blown one-phase fuse and increased single-phase current in the operation of three-phase compressor motor? The reason is usually due to the shell-to-shell contact of the compressor motor winding. After removing the grounding wire, you can use the electric probe to measure whether the shell is charged. If the casing is charged, unplug the power plug and touch the compressor casing with your hand, you should feel local heat. Please rewind the compressor motor winding or replace the compressor. 12. How to prevent the motor of three-phase compressor from making "beep" sound during operation? The "squeak" of three-phase compressor motor in operation is caused by the serious imbalance of three phases, and there must be a lack of phase in one phase power supply. Please use a multimeter to check the voltage range and restore three phases. 13. How to eliminate the motor reversal of three-phase compressor? It is caused by wrong wiring, so any two lines can be interchanged. 14. Replacement sequence of compressor and matters needing attention (1). The refrigerant (R22) used in the air conditioner is non-combustible, but it will decompose to produce toxic gas if it is in direct contact with high-temperature flame (if the pressure in the refrigeration system is too high and the welding operation is very dangerous, welding operation is absolutely not allowed at this time). Therefore, before the welding operation, the refrigerant in the refrigeration system is slowly discharged. 2. Determine whether the lubricating oil state is normal.
The condition of the oil is yellow-brown: the refrigerating machine oil is deteriorated and turned black due to high temperature; it is worn or severely carbonized by the refrigerating machine oil; it is yellow-green: water enters and produces acidic substances.
It doesn't taste as exciting as barbecue.
(3) When discharging residual refrigerant, please discharge it slowly. If it is too fast, the lubricating oil in the compressor will be discharged. If the compressor burns out, it will release the toxic gas produced during the thermal decomposition of refrigerant. Please pay attention. ⑷. After discharging the refrigerant, remove the electrical plug and parts on the compressor. 5]. Remove the welded part of the high and low voltage connecting pipe (to prevent the sound insulation material from being burned, a protective layer can be used). [6]. Remove the old compressor. Once. Pour out the compressor refrigeration oil and confirm the color of the oil. If the oil color is abnormal, clean the system. (8) Install a new compressor. Tax. Bend the high and low pressure connecting pipes with a pipe bender and install the original rubber feet. ⑽. Brazing operation, brazing pipe joint. ⑾. Connect the compressor wire. To avoid terminal wiring errors, you must refer to the circuit diagram for wiring. ⑿. The system is evacuated. Sufficient pumping time is needed to ensure the vacuum degree of the system. [13]. fluorine filling and leak detection. Fill fluorine according to the standard fluorine filling amount on the nameplate. 15. How to replace the scroll compressor? When replacing the scroll compressor, the high-pressure side and the low-pressure side should be discharged at the same time, and it is forbidden to discharge the refrigerant only from the high-pressure side. The axial seal of the scroll will keep the refrigerant on the low pressure side. During welding operation, in order not to form oxide film on the inner wall of copper tube, nitrogen gas must be introduced for enough time. The inspection method is to place a lit incense burner or cigarette butt at the other outlet of nitrogen. If the incense burner goes out, it means that the air in the system has been exhausted and the welding operation can be carried out. Because of the high requirements of scroll compressor, it is forbidden to use the compressor as a vacuum pump when replacing the compressor or other parts to evacuate the air in the pipeline of the external machine, otherwise it will burn out the compressor, and a vacuum pump must be used for vacuumizing. When the system is repairing the internal compressor to collect gas, it is not allowed to reduce the pressure in the system to a vacuum state, and the pressure in the system can only be controlled above the gauge pressure of 0.03MP, otherwise the axial seal of the scroll at the suction side of the compressor will form a vacuum, and improper operation will damage the compressor. 16. What should I pay attention to when using air conditioner for scroll compressor? Scroll compressor is easy to be damaged when moving to recover refrigerant, because it takes too long to recover refrigerant, the compressor runs in vacuum for a long time, the compression ratio is high, and the compressor temperature rises sharply, leading to combustion. Therefore, the time to recover the refrigerant does not exceed 3 minutes; Or observe the change of the low pressure gauge, when the low pressure gauge points to 0.03Mpa~0.05Mpa, pump for 20~30 seconds; Or shut down within 20 seconds after abnormal sound occurs during recycling. After moving and reloading, during debugging, it is necessary to check the low pressure to see if fluoride is needed. The low pressure is controlled between 0.45 MPa and 0.53 MPa according to the climate and temperature. 17. What are the types of overload protectors for air-conditioning compressors? There are two main types of overload protectors for air-conditioning compressors: (1) external overload protectors. The external overload protector is fixed on the compressor shell through a spring clip. It is connected in series to all the power lines through which current flows (if it is a three-phase compressor, it should be connected to two of the three lines). When the compressor is overloaded when the air conditioner is running or the ambient temperature exceeds 43℃, or the compressor is restarted less than 3 minutes after stopping, the overload protector will cut off the current and stop the compressor. The external overload protector consists of bimetallic disk (bimetallic strip), contacts, terminals and heating wires. The heating wire and bimetallic disc are installed in the heat-resistant resin base (some overload protectors only install bimetallic disc without heater). In case of overcurrent or overheating, the bimetallic disk will be heated and deformed, and the contacts will be disconnected to cut off the current, thus protecting the compressor motor. When the bimetallic disk is gradually cooled and restored to its original state, the contacts are closed and the current is switched on, so that the compressor can work again. ⑵ Embedded overload protector. In the structure of embedded overload protector, its temperature sensing element directly feels the temperature rise of motor winding. When the winding temperature exceeds a certain value, it will cut off the circuit and stop the compressor. When the winding temperature drops to the normal value, the protector turns on the power again to make the compressor work again. 18. What are the protective devices for air-conditioning compressors? Air-conditioning compressor is the most critical component in refrigeration system. When the power supply voltage is abnormal or the use environment is bad, it will often cause the compressor to overload. If there is no protection device, the compressor will be burned. At present, the commonly used protection devices have the following forms: (1) overload protector. It is mainly used for overcurrent and overheating protection of compressor motor. The casing of the overload protector is close to the surface of the compressor casing. When used in single-phase compressor motor, the protector should be connected in series on the power line through which all current passes; When used in three-phase compressor motor, the protector should be connected in series on two of the three-phase wires. ⑵ Internal protector. It is mainly used for single-phase compressor motor, which is connected in series on the same line of the motor winding inside the compressor to protect the compressor motor from overcurrent. (3) Thermal relay. It is mainly used for line overcurrent protection of three-phase compressor motor. Two groups of coils are connected in series on two phases in a three-phase circuit. When the overload current flows and reaches a certain time, its protection switch is turned off. (4) Reverse BOP. It is mainly used for the motor of three-phase rotary compressor to protect the phase sequence of three-phase power supply and prevent the rotation direction of compressor from reversing. In addition, it also has the function of phase failure protection. 19. How does the compressor overload protector of air conditioner work? Overload protectors generally have the protection function of starting and running. When the compressor starts, the rotor is "crushed" due to mechanical failure, and the current rises rapidly. When the current exceeds the rated value of the starting current, the contact of the protector jumps to cut off the current and avoid the motor starting winding from burning. When the compressor is running normally, when the temperature rise is too high or the current allowable value is caused by external reasons, the contact of the protector will also jump off, cutting off the power supply and avoiding the burning of the motor running winding. 20. What are the common faults of overload protector? What is the reason? How to check the maintenance? The common faults of overload protector are: the heating wire is burnt out, the contact is burnt out, the contact cannot be reset after the internal stress of bimetal changes, the insulation of embedded overload protector is damaged, and the contact fails. The reasons of overload are: (1) low power supply voltage and poor symmetry of three-phase voltage. ⑵ The compressor motor runs at low speed for a long time. (3) Long-term low-voltage load operation of compressor motor. (4) The cooling medium channel of the compressor motor is blocked. 5] Operating environment temperature is too high. Check the overload protector with a multimeter. Under normal circumstances, there should be a resistance value of several tens of ohms. If the resistance value is infinite, the overload protector is open. After the overload protector fails, except for poor contact and adhesion, other failures are generally not repaired, but only replaced and updated. After the embedded overload protector fails, it is generally difficult to repair and replace, and it can only be replaced with the compressor. In the three-phase compressor motor, most of the three-phase overload protectors used are bimetals. The bimetal element is connected in series with the contactor coil and low voltage (24V) line of the compressor. The heating wire is connected in series with the contactor of the compressor and the motor connector (in the power supply circuit). When the metal sheet feels overheated or overcurrent, the bimetal can open and close the motor circuit of the compressor. 2 1. What is the liquid hammer of compressor? Under the normal working condition of air conditioner, the compressor sucks back refrigerant vapor instead of liquid. However, due to the excessive refrigerant charge or the excessive flow regulated by the expansion valve, the refrigerant is not completely evaporated in the evaporator, which leads to the refrigerant being sucked back by the compressor in wet vapor or liquid state, resulting in the liquid impact of the compressor. It will lead to the damage of the port plate, port plate and piston, and may lead to the deformation of the connecting rod in serious cases. When the liquid hammer occurs, the compressor will make abnormal noise and vibration at the same time. If there is too much refrigerant or oil in the refrigeration system, the phenomenon of liquid hammer will occur. The evaporator of air conditioner is poorly ventilated. If the evaporator cannot be taken away by cold energy, it will frost or freeze, resulting in low pressure and low pressure, and it will also lead to frosting of compressor shell and liquid hammer.