【2026 Mechanical Equipment】Key causes of frequent high-temperature issues in screw air compressors during summer
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As summer temperatures continue to rise, faults such as high-temperature alarms and shutdowns in screw air compressors also become more frequent. 1. Insufficient lubricating oil in the air compressor system. During troubleshooting, it is necessary to pay close attention to 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 low oil levels.
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 stops, 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) 3.1. 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 fairly urgent fault scenario. 3.2. Clogging of the oil filter leads to a reduced oil flow: In one case, the lubricating oil fails to remove enough heat, causing the temperature of the air compressor 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 circuit ； 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 coefficient 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 circumstances. If high temperatures occur due to insufficient fuel injection, it is likely a problem related to the equipment’s 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 greatly, preventing it from removing the heat generated by the compressor head in a timely manner, which ultimately leads 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 measuring 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 blockages inside the cooler are present, 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 resolved by installing cooling towers, improving ventilation in the machine room, or expanding the space of the machine room ； At the same time, it is necessary to check the operating condition of the cooling fan; if the fan malfunctions, it should be repaired or replaced promptly.
9. Investigation of abnormal temperature differences between oil inlet and outlet in air-cooled units: For air-cooled air compressors, it is essential to check the temperature difference between 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 resulting damage to the radiator.
10. Improper installation of the 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 airflow 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 this case is relatively simple； If the sensor is not functioning properly and its readings are inconsistent, the fault becomes more concealed 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.