【Useful Tips】The friend circle is flooded with posts about screw compressors, but do you know how many hardware components they have and what their functions are?

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I. Intake valve: There are two types of intake valves: one is a normally open intake valve, and the other is a normally closed intake valve. 1. The normally open intake valve ensures that when the air compressor starts operating but the Y–△ AC contactor has not been switched over, the control solenoid valve for the intake valve is de-energized, allowing air to flow directly into the valve and causing it to close. Once the Y–△ AC contactor is switched over and the control solenoid valve is energized, it cuts off the air supply, and the intake valve opens automatically. (Generally, normally open intake valves use normally open solenoid valves; the principle is that they close when powered and open when power is cut off.) 2. The normally closed intake valve remains closed when the air compressor starts operating and the Y–△ AC contactor has not been switched over; in this case, the control solenoid for the valve is not powered, so the valve does not open. Once the Y–△ AC contactor is switched over and the control solenoid is powered, air pressure flows through the control solenoid to the control tube of the intake valve, causing the valve to open. (Generally, normally closed intake valves use two-position three-way normally closed solenoid valves; the principle is that they open when powered and close when power is cut off.) ) II. Air compressor unit The operating principle of the air compressor unit: When the compressor starts, the Y–△ AC contactor is activated, which changes the speed of the motor. The motor drives the air compressor unit to draw in a small amount of air through the intake valve, thereby circulating oil for lubrication purposes. When the control solenoid valve for the intake valve is activated, the valve opens, and the compressor unit begins to compress a large volume of oil-air mixture, which is then sent into the oil cylinder. After passing through the oil-air separator, the air proceeds to the exhaust minimum pressure valve (this valve opens at a pressure of around 4 bar–4.5 bar). From there, the air enters the air-cooled radiator, where it is cooled before being sent to the air storage tank. It then passes through a pre-filter before reaching the refrigerated dryer, where the air is cooled and any moisture removed from it. Finally, after passing through an additional post-filter, the air becomes the compressed air required by the factory. III. Oil circuit circulation: The motor drives the air compressor; a small amount of air is drawn in through the intake valve and compressed into the cylinder. Once pressure is generated in the cylinder, the oil circuit begins to circulate. The oil from the cylinder passes through a thermostatic valve that maintains the temperature at below 75°C–90°C; it then goes straight through an oil filter before entering the compression chamber, where it supplies oil to the rotor and bearings for circulation. When the lubricating oil temperature is above 75°C–90°C, the thermostatic valve core opens automatically. The oil in the cylinder passes through this thermostatic valve and enters the air-cooled radiator, where it is cooled down. After that, the lubricating oil is filtered by the oil filter before entering the compression chamber to supply oil for the rotor and bearings in a continuous cycle. IV. Cylinder: The cylinder is used to store lubricating oil and separate the oil-gas mixture. When the oil-gas mixture discharged by the compressor enters the cylinder, the air after separation by the oil-gas separator is expelled, while the small amount of oil separated is drawn back into the compression chamber through the oil return pipe of the oil-gas separator. V. Minimum Pressure Valve The minimum pressure valve (also known as a check valve) prevents the pressure in the air tank from returning into the cylinder and compressor head. If the air tank’s pressure is too high and the pressure inside the cylinder has not been released fully, restarting the air compressor can lead to poor operation; this can result in an excessive load on the motor, causing it to shut down due to overload. Frequent restarts over an extended period can damage the motor coils. If the minimum pressure valve leaks, the cylinder will not maintain a sufficient pressure at the moment it starts up, which can prevent the intake valve from opening. If the valve element inside the minimum pressure valve is severely damaged, there will be no pressure in the cylinder at all. A lack of lubricant circulation can lead to high temperatures in the exhaust system; in severe cases, the compressor head may not receive enough supply of lubricant, resulting in damage to the compressor head. VI. Radiator: The radiator is used to cool the lubricating oil inside the cylinder, which then goes to the engine head to lubricate the rotor and bearings. Excessive dust on the outside of the radiator can cause high exhaust temperatures and machine shutdown; it is necessary to clean the radiator fins using an air blower. VII. Thermostatic valve: The function of the thermostatic valve is to prevent it from activating when the oil temperature has not yet reached a certain level right after the air compressor starts up. Once the temperature exceeds a specific value (above 75°C–90°C), the thermostatic valve opens automatically, allowing the lubricating oil to pass through the radiator in order to lose heat. VIII. Oil Filter. The function of the oil filter is to filter out iron particles resulting from friction in the compressor’s rotors and bearings, as well as impurities and dust present in the lubricating oil. A clogged oil filter can lead to excessive temperatures, poor supply of oil to the compressor components, and severe wear on the rotors and bearings. IX. Oil cut-off valve: The function of the oil cut-off valve is to automatically open the oil circuit and enable oil circulation when the air compressor starts up. If the valve gets stuck and cannot be opened, it can lead to excessive temperatures; whereas if the valve fails to close properly when the air compressor stops, it can cause significant oil spraying from the intake valve. X. Head exhaust check valve: The function of the head exhaust check valve is to allow a large amount of oil-gas mixture to flow into the oil cylinder once the intake valve opens during compressor operation, as the compression takes place. If the exhaust check valve becomes stuck and cannot open, it can cause the compressor’s current to exceed its limit, leading to shutdown. If the exhaust check valve does not close properly when the compressor stops operating, it can result in excessive oil spraying from the intake valve. XI. Oil circuit control valve: The oil circuit control valve is used to regulate the amount of oil flowing through it. If there is a leakage in the piston seal inside this valve, it will prevent the valve from opening, which can lead to a shutdown of the machine due to high temperatures. XII. Return Oil Pipe: The function of the return oil pipe is to carry the gas-oil mixture, after separation by the gas-oil separator, back to the engine head; the small amount of oil contained in this mixture settles at the bottom of the gas-oil separator, and the return oil pipe transports it back to supply lubrication to the bearings. 13. Check valve on the oil return pipe: The function of the check valve on the oil return pipe is to prevent the lubricating oil drawn back through this pipe from flowing in reverse. When the seal inside the check valve is damaged, the oil inside the compressor will flow back into the oil-gas separator when the compressor stops operating. When it is restarted, the oil cannot return to the compressor in time, which can lead to oil leakage. If the check valve becomes clogged, more and more oil will accumulate in the oil-gas separator, resulting in severe oil leakage. 14. Pressure relief valve: The function of the pressure relief valve is to release the internal pressure in the cylinder when the load on the air compressor reaches the set upper pressure limit; it activates to do this during unloaded operation. When the external pressure discharged by the air compressor drops to the set lower pressure limit, the pressure relief valve closes automatically, allowing the air compressor to start operating under load once again. If the pressure relief valve becomes stuck and cannot open, and the pressure continues to rise above the upper set limit, the safety valve will automatically release air. 15. Bleed solenoid valve: The function of the bleed solenoid valve is to open when the pressure generated by the air compressor reaches the upper set value, thereby releasing the internal pressure in the cylinder. It closes when the external pressure discharged by the air compressor drops to the lower set value, allowing the compressor to start operating again. If the sealing element inside the bleed solenoid valve is damaged or if the valve body becomes stuck and cannot be opened, the air compressor will continue to operate at a pressure above the upper set value; in such cases, the safety valve will automatically release air. 16. Loading solenoid valve: The function of the loading solenoid valve is to allow air to pass through it once the air compressor is in operation; only after this air reaches the control tube of the intake valve can the intake valve open. If the sealing element inside the loading solenoid valve is damaged or if the valve body gets stuck and cannot be opened, the intake valve will not open, and the air compressor cannot operate in loading mode. 17. Oil cut-off solenoid valve: The function of the oil cut-off solenoid valve is to allow oil flow when the air compressor starts up, thereby enabling the oil circuit to circulate. If the coil is damaged or does not receive power, if the internal seals of the solenoid valve are damaged, or if the valve body gets stuck and cannot open, it will prevent the lubricating oil in the air compressor from circulating, resulting in high exhaust temperatures. 18. Safety Valve: The function of a safety valve is to prevent excessive pressure from building up inside the air compressor’s cylinders. Situations such as a clogged oil-gas separator, a stuck minimum pressure valve, an intake valve that cannot close properly, a stuck exhaust valve that prevents internal pressure from being released, an exhaust solenoid valve that will not open, an excessively high set pressure, a malfunctioning pressure switch, inaccurate readings from the pressure sensor, or a safety valve spring that has lost its strength can all cause the safety valve to activate and release air. This article is from the WeChat official account of China Compressor Network