Frequent high temperatures in screw air compressors during summer? Comprehensive Analysis of 16 Core Failure Causes (Professional Troubleshooting Version)

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As ambient temperatures continue to rise, faults such as high-temperature alarms and shutdowns in screw air compressors also become more frequent. To help everyone identify problems quickly and resolve faults efficiently, this article systematically outlines the key reasons that can cause high temperatures in air compressors. Each point includes practical troubleshooting tips, balancing professionalism with usability for reference by industry professionals. Shangji Mechanical & Electrical – Mingke Air Compressors is here to provide you with protection. 1. When checking for insufficient lubricating oil in the air compressor system, it is important to examine the oil level in the oil-gas tank: after the equipment is shut down and the pressure is released, once the lubricating oil has come completely to rest, the oil level should be slightly above the high-level mark H (or MAX) on the oil level gauge ； During normal operation of the equipment, the oil level must not drop below the low oil level mark L (or MIX). If it is found that the oil level is insufficient, or if the oil level cannot be seen with the naked eye, the machine must be stopped immediately to add lubricant that meets the specified standards, in order to prevent damage to the machine head due to a lack of oil. 2. Abnormal operation of the oil cut-off valve: The oil cut-off valve is usually a two-position, normally closed solenoid valve. Its primary function is to open automatically when the equipment starts up and to close promptly when it stops, thereby preventing the lubricating oil in the oil tank from continuing to flow into the machine head after it has stopped, and thus from leaking out through the air intake. If this component fails to operate properly when the equipment is started, the head will heat up rapidly due to a sudden lack of oil; in severe cases, this can damage the screw assembly irreversibly. 3. Oil filter failure (two common scenarios): A. The oil filter is clogged and the bypass valve is not activated: In this case, the lubricating oil cannot reach the engine head properly, causing the engine head to heat up rapidly due to a lack of oil; this is a relatively urgent fault scenario. B. Clogging of the oil filter leads to reduced oil flow: In one case, the lubricating oil fails to remove enough heat, causing the compressor temperature to rise gradually to high levels ； Another scenario is high temperature occurring after the air compressor is unloaded – when the device is under load, the oil pressure inside is high, allowing the lubricating oil to pass through the filter fairly easily; however, once the compressor is unloaded, the oil pressure drops, increasing the resistance for the lubricating oil to pass through the filter and resulting in a sharp decrease in flow rate, which ultimately leads to high temperatures. 4. Failure of the thermal control valve (temperature control valve). The thermal control valve is installed in front of the oil cooler; its primary function is to keep the exhaust temperature of the machine head above the pressure dew point, thereby ensuring the stable operation of the equipment. Its working logic is as follows: When the equipment starts up, the oil temperature is low; the thermal control valve circuit is in the open state while the main circuit is closed. The lubricating oil is injected directly into the machine head without passing through the cooler ； When the oil temperature rises above 40°C, the thermal control valve gradually closes, and the lubricating oil flows through both the cooler and the bypass at the same time ； When the oil temperature rises above 80°C, the thermal control valve closes completely, and all the lubricating oil passes through a cooler before entering the machine head, thereby minimizing the oil temperature as much as possible. If the thermal control valve fails, the lubricating oil may bypass the cooler and flow directly into the machine head, preventing the oil temperature from dropping effectively and thus leading to overheating. There are two main reasons for the failure: first, the large and small thermal springs on the valve core experience changes in their elastic coefficients due to fatigue, preventing them from functioning properly in response to temperature changes ； Secondly, wear of the valve body causes the valve core to get stuck or to not operate properly, preventing it from closing correctly. Depending on the severity of the fault, one can choose to repair the thermal control valve or replace it directly. 5. Abnormal operation of the fuel quantity regulator: The fuel injection volume of the fuel quantity regulator is calibrated at the time the equipment leaves the factory, and no adjustment is required under normal conditions. If high temperatures occur due to insufficient fuel injection, it is likely a problem related to the equipment design; if necessary, the fuel injection volume can be increased slightly to alleviate the high temperature issue. 6. Aging and deterioration of lubricant (exceeding the service life). When lubricant is used for an extended period of time, it ages and deteriorates; its fluidity significantly decreases, and its heat exchange capacity also drops markedly. As a result, it is unable to remove the heat generated by the compressor head in a timely manner, ultimately leading to high-temperature failures in the compressor. It is recommended to replace the lubricant regularly in strict accordance with the equipment’s operating instructions. 7. Troubleshooting abnormal operation of oil coolers: For water-cooled air compressors, it is possible to determine the operating condition of the cooler by checking the temperature difference between the inlet and outlet of the cooling water pipes; under normal conditions, this temperature difference should remain between 5-8℃ ； If the temperature difference is below 5°C, it is likely that scaling or blockage inside the cooler has occurred, resulting in reduced heat exchange efficiency and poor heat dissipation. At this point, the heat exchanger needs to be removed and thoroughly cleaned to restore its cooling performance. 8. Abnormal conditions in the cooling system (check separately for water-cooled and air-cooled models). For water-cooled models: it is necessary to verify whether the inlet temperature of the cooling water, as well as the water pressure and flow rate, meet the specified standards – the inlet temperature of the cooling water should not exceed 35°C, the water pressure should be maintained between 0.3–0.5 MPa, and the flow rate must not be less than 90% of the value specified by the equipment. For air-cooled models: It is necessary to pay close attention to the ambient temperature; the normal operating temperature should not exceed 40°C. If the above requirements cannot be met, it can be addressed by installing cooling towers, improving ventilation in the machine room, or expanding the space of the machine room ； It is also necessary to check the operating condition of the cooling fan; if the fan malfunctions, it should be repaired or replaced promptly. 9. Troubleshooting abnormal oil inlet and outlet temperature differences in air-cooled units: For air-cooled air compressors, it is important to check the temperature difference between the oil inlet and outlet; the normal value should be around 10°C. If the temperature difference is less than 10°C, it is necessary to first check whether the fins on the surface of the radiator are dirty or blocked; if dust has accumulated, it can be blown away using clean air ； At the same time, check whether the fins are corroded; if the corrosion is severe, replacing the radiator assembly should be considered. In addition, it is also necessary to check whether the pipes inside the radiator are blocked. If there is a blockage, a circulation pump can be used along with an appropriate amount of acidic cleaning solution for cyclic cleaning; care must be taken to strictly control the concentration of the cleaning solution and the circulation time, in order to avoid corrosion of the pipes and subsequent damage to the radiator. 10. Improper installation of exhaust ducts in air-cooled models: Some users encounter various problems with the exhaust ducts when installing air-cooled air compressors, which leads to poor heat dissipation and high temperatures in the equipment. Common issues include an insufficient air flow area of the exhaust ducts, excessive duct length, and too many bends along the ducts ； In some long and heavily curved exhaust ducts, exhaust fans are not installed, or the flow rate of these fans is lower than that of the cooling fans originally equipped on the air compressors, which prevents effective removal of heat from the machine room. 11. Inaccurate temperature sensor readings: If the temperature sensor is completely disconnected, the device will immediately issue an alarm and shut down, displaying “Sensor error”; troubleshooting in such cases is relatively simple ； If the sensor is not functioning properly and its readings are inconsistent, the fault becomes more hidden and it is more difficult to diagnose. It is recommended to use a replacement method (by installing a new sensor) to determine quickly whether the issue lies with the sensor. 12. In the case of faults in the compressor head itself, the recommended replacement cycle for the bearings in the compressor head is 20,000–24,000 hours. The adjustment of gaps in the head as well as the balancing of its components rely on the proper positioning of these bearings. If bearing wear worsens, it will cause direct friction between the internal components of the machine head, generating a large amount of heat and leading to high temperatures in the equipment ； In severe cases, it can cause the main unit to lock up, or even lead to the destruction of the machine head; therefore, it is necessary to regularly check the condition of the bearings and replace them on time. 13. Incompatible or low-quality lubricant: Screw air compressors have strict requirements regarding the specifications of the lubricant used; it is not permissible to use alternative oils. The lubricant type specified in the equipment’s user manual must be used strictly, to avoid a decrease in lubrication efficiency and poor heat dissipation as a result of incompatible or low-quality lubricant, which in turn can lead to high temperatures. 14. Clogged air filters can cause an increase in the load on the air compressor; remaining in a loaded state for an extended period can lead to high temperatures. Generally, the air filter can be checked or replaced in a timely manner based on the alarm signal from the pressure differential switch. It should be noted that the primary sign of a clogged air filter is a decrease in the amount of gas produced by the equipment, while high temperature is a secondary symptom. If a drop in gas production is observed, the air filter should be checked first. 15. Excessively high system pressure: The pressure of the air compressor system is set at the time of manufacture. If adjustment is indeed necessary, it must be done within the limit of the rated gas production pressure indicated on the equipment’s nameplate. If the pressure is set too high, it will increase the operating load on the equipment, leading not only to high temperatures but also to overcurrent in the motor and shutdown due to overload. Similar to air filter clogging, high temperature is not the main symptom of this fault; the key manifestations are an increase in motor current and the device shutting down as a result of protection measures. 16. Clogging of the oil-gas separator: A clogged oil-gas separator can lead to an increase in pressure inside the equipment, which in turn triggers a series of faults; high temperature is one of the more common ones. It should be noted that the main symptom of a clogged oil-gas separator is excessive pressure inside the device; high temperature is a secondary issue. When troubleshooting, internal pressure should be checked first to determine whether the oil-gas separator is clogged. The above are the 16 key causes of failures in screw air compressors under high summer temperatures, along with the key points for troubleshooting. These details are based on practical experience and are provided solely for reference by industry professionals when dealing with such failures. Proper inspection and timely handling are necessary to effectively reduce the damage caused by high-temperature failures to the equipment, ensuring the stable operation of air compressors during summer.