In summer, high temperature faults of air compressors occur frequently. This paper summarizes the possible causes of high temperature.
1. Lack of oil in air compressor system.
This system monitors oil level in oil and gas cylinders. After shutdown and pressure relief, when lubricant is at rest, the oil level should be slightly higher than the high-level mark (H or MAX). During operation, the oil level must never drop below the low-level mark (L or MIX). If insufficient oil level is detected or the oil level cannot be visually observed, immediate shutdown for oil replenishment is required.
2. The oil stop valve (oil cut-off valve) does not work properly.
The oil stop valve is typically a normally closed solenoid valve with two-position operation. It opens during startup and closes upon shutdown to prevent residual oil from the oil-gas drum from spraying into the machine head and escaping through the air inlet. If this component fails to open during loading, the motor may rapidly overheat due to insufficient oil supply, which could potentially cause severe damage to the screw assembly.
3. Oil filter problem.
A: When the oil filter becomes clogged and the bypass valve remains closed, the air compressor's oil cannot reach the compressor head, causing rapid temperature rise due to insufficient lubrication. B: Clogged oil filters reduce oil flow. Two main scenarios occur: First, incomplete heat dissipation from the compressor leads to gradual temperature buildup. Second, when the compressor is unloaded, its high-temperature condition creates pressure that allows oil passage. However, during unloading when oil pressure drops, the compressed oil struggles through the filter, resulting in reduced flow and subsequent overheating.
4. The thermal control valve (temperature control valve) fails to work.
The thermal control valve is installed in front of the oil cooler, designed to maintain the engine head exhaust temperature above the pressure dew point. Its working principle involves: During initial startup when oil temperature is low, the branch circuit of the thermal control valve opens while the main circuit remains closed, allowing lubricating oil to bypass the cooler and directly enter the engine head. When temperature rises above 40℃°C, the valve gradually closes as both the cooler and branch circuit begin circulating oil. Upon reaching 80℃°C, the valve fully closes, directing all lubricating oil through the cooler before entering the engine head for maximum cooling. Malfunction of this valve may cause lubricant bypassing the cooler, preventing temperature reduction and resulting in overheating. Primary failure mechanisms include: 1) Fatigue-induced changes in elastic coefficients of large and small thermal springs on the valve core, impairing temperature-responsive operation; 2) Valve body wear causing valve core jamming or incomplete closure. These issues can be addressed through condition-based repairs or replacements.
5. The oil regulator is not normal, and the oil injection can be increased appropriately when necessary.
The injection oil is adjusted when the equipment leaves the factory and should not be changed under normal circumstances. In this case, it should be attributed to the design problem.
6. The oil has been used for more time and the oil has deteriorated.
The fluidity of oil is deteriorated and the heat exchange performance is decreased. As a result, the heat of the air compressor head cannot be completely removed and the air compressor is high temperature.
7. Check whether the oil cooler works normally.
For water-cooled models, the temperature difference between inlet and outlet pipes can be checked. Under normal circumstances, it should be 5-8℃. If it is lower than 5℃, there may be scaling or blockage, which will affect the heat transfer efficiency of the cooler and cause poor heat dissipation. In this case, the heat exchanger can be removed for cleaning.
8. Check whether the inlet temperature of cooling water is too high, whether the water pressure and flow rate are normal, and for air-cooled models, check whether the ambient temperature is too high.
The inlet temperature of cooling water should generally not exceed 35℃, with water pressure maintained between 0.3-0.5 MPa and flow rate not less than 90% of the specified capacity. Ambient temperature must not rise above 40℃. If these requirements are not met, solutions may include installing cooling towers, improving indoor ventilation systems, or expanding the equipment room space. Additionally, verify the proper operation of cooling fans – any malfunctioning units should be repaired or replaced immediately.
9. Main inspection of air cooling unit is oil inlet and outlet temperature
Check if the temperature difference is around 10 degrees. If it's less than this value, inspect whether the radiator fins are dirty or clogged. If so, clean the dust off the radiator surface with clean air and check for corrosion on the fins. If severe corrosion is observed, consider replacing the entire radiator assembly. Check for dirt or blockages in internal pipes. If present, use a circulation pump to flush with acidic solution for cleaning. Be sure to pay attention to the concentration of the solution and the circulation time to prevent the radiator from being corroded through its core.
10. Problems with the exhaust duct installed by customers of air-cooled models.
The air passing surface of the exhaust pipe is too small, the exhaust pipe is too long, the middle bend of the exhaust pipe is too many, most of the middle bend of the long exhaust pipe is not installed with a fan, and the flow rate of the fan is less than that of the original cooling fan of the air compressor.
11, temperature sensor reading is not accurate.
If the temperature sensor is completely disconnected, the equipment will alarm and stop, and display the abnormal sensor. If the working is not good, it is more hidden and difficult to troubleshoot, so it is better to use the alternative method to eliminate it.
12. Head problems.
The bearing of the General Air Compressor head requires to be replaced in 20,000-24,000 hours, because the gap and balance of the air compressor are positioned by the bearing. If the bearing wear increases, it will cause the air compressor head to directly produce friction, increase the heat, cause the high temperature of the air compressor, and in serious cases, the main engine may lock up and be scrapped.
13. The specification of lubricating oil is not correct or the quality is poor.
The lubricating oil of screw machine generally has strict requirements, can not be replaced at will, should be subject to the requirements in the equipment use manual.
14.Air filter is blocked.
Air filter blockage can cause excessive load on the air compressor. Prolonged operation under high load can lead to high temperature. The pressure switch alarm signal can be used to check or replace the air filter. Generally, the first problem caused by air filter blockage is reduced gas production, while high temperature of the air compressor is a secondary manifestation.
15. Too high system pressure.
The system pressure is typically pre-adjusted at factory. When adjustments are necessary, the upper limit should be set as the rated gas production pressure indicated on the equipment nameplate. Excessive adjustment may cause overheating and overcurrent overload due to increased machine load. Similar to the previous issue, high temperature in air compressors is a secondary symptom. The primary indicator of this problem is elevated motor current in the compressor, which triggers protective shutdown mechanisms.
16. Oil and gas separator blockage.
The blockage of the oil and gas separator will cause the internal pressure to be too high, which will cause many problems, high temperature is one of them. This is also the same as the first two reasons, the blockage of the oil and gas separator is mainly manifested as the high internal pressure.
