Reasons for excessive temperature in air compressors

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1. Excessively high ambient temperatures have the following two effects on screw air compressors: A: The higher the temperature, the thinner the air becomes (just as an air compressor operates less efficiently in high-altitude areas), which reduces its efficiency. This causes the compressor to operate in a loaded state for longer periods, with a greater load, resulting in more heat being generated by the compressor and thus an even higher temperature. B: Generally, air compressors are designed with a specified operating ambient temperature (30–40 degrees). When operating at this designated temperature, the maximum temperature reached by the compressor is usually close to its protection temperature. If the ambient temperature around the compressor is higher than the specified value, it will cause the compressor’s temperature to rise, potentially exceeding its shutdown temperature and resulting in overheating of the compressor. 2. If the air compressor is lacking oil, check the oil level in the oil-gas tank; when the machine is shut down and the pressure has been released, with the lubricating oil at rest, the oil level should be slightly above the high oil level mark H (or MAX). During equipment operation, the oil level must not drop below the low oil level mark L (or MIX). If the oil level is found to be low or cannot be seen, the machine should be stopped immediately to add oil. 3. The oil shut-off valve (oil cut-off valve) is not functioning properly. This valve is usually a two-position, normally closed solenoid valve that opens during startup and closes when the machine stops, in order to prevent the oil in the oil tank from continuing to flow into the machine head and escaping through the air intake. If this component is not activated when the unit is under load, the machine will heat up rapidly due to a lack of oil, and in severe cases this can lead to the destruction of the screw assembly. 4. Oil filter issue: A: If the oil filter becomes clogged and the bypass valve does not open, the air compressor oil will not reach the motor head, causing the machine to heat up rapidly due to a lack of oil. B: When the oil filter becomes clogged, the flow rate decreases. One reason for this is that the air compressor does not remove heat completely, which causes its temperature to rise gradually and lead to high temperatures. Another reason is that the compressor remains at high temperature after it stops operating; during operation, the internal oil pressure is high, allowing the oil to pass through the filter easily, but once the compressor stops working, the oil pressure drops, making it difficult for the oil to pass through the filter. As a result, the flow rate is too low, which in turn causes the compressor to reach high temperatures. 5. Failure of the thermal control valve (temperature control valve) to function properly. The thermal control valve is installed in front of the oil cooler; its role is to keep the exhaust temperature of the engine head above the pressure dew point. Its working principle is that at startup, due to the low oil temperature, the thermal control valve circuit opens while the main circuit closes; as a result, the lubricating oil is injected directly into the machine head without passing through a cooler ； Once the temperature rises above 40°C, the thermal control valve gradually closes, and oil flows simultaneously through the cooler and the branch circuit ； When the temperature rises above 80°C, the valve closes completely, and all of the lubricating oil passes through the cooler before entering the machine head, thereby achieving greater cooling of the lubricating oil. If the thermal control valve fails, the lubricating oil may enter the machine head directly without passing through the cooler, preventing the oil temperature from dropping and resulting in overheating. The main reason for its failure is that the elastic coefficients of the large and small thermosensitive springs on the valve core change due to fatigue, preventing them from functioning properly in response to temperature changes ； Secondly, the valve body is worn out, and the valve core gets stuck or does not move properly, preventing it from closing correctly. It can be repaired or replaced as appropriate. 6. Check whether the oil quantity regulator is functioning properly; if necessary, the fuel injection amount can be increased slightly. The fuel injection amount is set at the time the equipment leaves the factory, and it should generally not be changed. 7. The engine oil has exceeded its service life and has deteriorated; its fluidity decreases, resulting in a reduced heat exchange efficiency. The heat generated in the compressor head cannot be completely removed, resulting in high temperatures in the compressor. 8. Check whether the oil cooler is working properly. For water-cooled models, the temperature difference between the inlet and outlet water pipes can be checked; under normal conditions, this difference should be 5–8°C. If it is lower than 5°C, there may be scaling or blockages, which will affect the heat exchange efficiency of the cooler and lead to poor heat dissipation. In such cases, the cooler can be removed and cleaned. 9. Check whether the inlet temperature of the cooling water is too high, and whether the water pressure and flow rate are normal. For air-cooled models, check whether the ambient temperature is too high. The inlet temperature of the cooling water should generally not exceed 35°C, the water pressure should be between 0.3 and 0.5 MPA, and the flow rate should be no less than 90% of the specified value. The ambient temperature should not exceed 40°C. If the above requirements cannot be met, it can be addressed by installing cooling towers, improving indoor ventilation, or expanding the space of the machine room. It is also possible to check whether the cooling fan is working properly. If there is a malfunction, it should be repaired or replaced. 10. For air-cooled units, it is necessary to check whether the difference between the inlet and outlet oil temperatures is around 10 degrees. If this value is lower, it is necessary to examine whether the fins on the surface of the radiator are dirty or blocked; if so, clean the dust from the radiator surface using clean air. It is also important to check whether the radiator fins are corroded – if corrosion is severe, it may be necessary to replace the entire radiator assembly. Additionally, check whether there is any blockage in the internal pipes; if there is, a circulation pump can be used to flush them with an acidic solution. Be sure to pay attention to the concentration of the solution as well as the circulation time, to avoid damage to the radiator due to corrosion caused by the solution.

11. Problems with the fans in air-cooled units include fans that do not rotate, fans operating in the reverse direction, or only one of the two fans functioning properly.

12. Regarding the exhaust ducts installed by customers using air-cooled units, issues may include exhaust ducts with too small an air flow area, ducts that are too long, excessive bends along the ducts, or a lack of exhaust fans. In such cases, the flow rate of the exhaust fan may be lower than that of the fan designed for cooling the air compressor. 13. Inaccurate readings from the temperature sensor. 14. Inaccurate readings from the computer. 15. Problems with the compressor head. Generally, the bearings in the compressor head need to be replaced after 20,000–24,000 hours of use, as it is the bearings that ensure proper clearance and balance in the compressor. If the bearings wear out significantly, it will lead to increased heat generation in the compressor head, causing the compressor to run at high temperatures. 16. Incorrect lubricant specifications or poor quality: Lubricants for screw machines have strict requirements; they cannot be replaced arbitrarily, and the specifications stated in the equipment’s user manual must be followed. 17. Check whether the air filter is clogged. A clogged air filter can cause excessive load on the air compressor, and staying in a loaded state for a long time can lead to high temperatures. It can be checked or replaced based on the alarm signal from the pressure difference switch. The first problem that occurs when an air filter becomes clogged is a reduction in gas production, while high temperature of the air compressor is a secondary symptom. 18. Check whether the pressure is too high. The system pressure is usually set at the time of manufacture; if adjustment is necessary, it should be done in accordance with the rated gas generation pressure indicated on the equipment’s nameplate. If the adjustment is too high, the increased load on the machine will cause overheating. For this reason as well, the high temperature of the air compressor is a secondary symptom; the main issue is an increase in the current flowing through the air compressor’s motor, which leads to the compressor shutting down as a protection measure. 19. Clogged oil-gas separator: A clogged oil-gas separator can lead to excessive internal pressure, and high pressure can cause various problems, with high temperature being one of them. This is the same as the first two reasons; a clogged oil-gas separator is mainly characterized by high internal pressure.