Analysis of Various Potential Causes of High Temperature in Air Compressors

High temperature is one of the common faults in the use of air compressors, especially for mobile air compressors working outdoors. This article aims to identify various potential causes of this problem and analyse them.

1. The impact of high environmental temperature on screw air compressors mainly comes from two aspects.

A: The higher the temperature, the thinner the air (just like the air compressor is inefficient in plateau areas), resulting in a decrease in the working efficiency of the air compressor. This causes the air compressor to be in a loading state for more time, resulting in more heat generated by the air compressor, and the air compressor will definitely have a higher temperature.

B: When designing an air compressor, there is a consideration of designing the operating environment temperature (30-40 degrees Celsius). Under the designed operating environment temperature, the operating temperature of the air compressor is generally close to the protection temperature of the air compressor. If the ambient temperature of the air compressor is higher than the designed operating environment temperature, it will increase the temperature of the air compressor, making it easier for the air compressor to exceed the shutdown temperature, resulting in high temperature of the air compressor.

2. The air compressor system is out of oil.

When the oil level in the air compressor system is insufficient and the cooling is not sufficient, the air compressor will definitely experience high temperatures. The oil level in the oil and gas tank can be checked. After the shutdown and pressure relief, when the lubricating oil is in static state, the oil level should be slightly higher than the high oil level mark H (or MAX). During equipment operation, the oil level should not be lower than the low oil level mark L (or MIX). If insufficient oil is found or the oil level cannot be observed, the machine should be stopped immediately for refuelling.

3. The cut-off valve is not working properly.

 The oil cut-off valve is usually a two position two normally closed solenoid valve, which is opened during startup and closed during shutdown to prevent the oil in the oil and gas barrel from continuing to spray into the machine head and exiting from the air inlet during shutdown. If the component is not turned on during loading, the host will rapidly heat up due to oil shortage, and in severe cases, it may cause the screw assembly to burn out.

4. Oil filter issue.

A: The oil filter is blocked by the bypass valve, and if it is not opened, it will cause the air compressor oil to not reach the machine head, and the main engine will quickly heat up due to oil shortage.

B: The oil filter is clogged and the flow rate decreases. One situation is that the air compressor does not completely remove heat, causing the temperature of the air compressor to gradually increase and form high temperatures; Another situation is that after the air compressor is unloaded, the air compressor becomes hot because the internal oil pressure of the air compressor is high during loading, and the air compressor oil can pass through. However, after the air compressor is unloaded, the pressure of the air compressor oil is low, and it is difficult for the air compressor oil to pass through the air compressor oil filter. The flow rate is too small, resulting in high temperature of the air compressor.

5. The temperature control valve (thermal control valve) is malfunctioning.

The temperature control valve is installed in front of the oil cooler, and its function is to maintain the exhaust temperature of the machine head above the pressure dew point. Its working principle is that when the machine is first started, due to the low oil temperature, the temperature control valve branch is opened, the main circuit is closed, and lubricating oil is directly sprayed into the machine head without passing through the cooler; When the temperature rises to above 40 ℃, the temperature control valve gradually closes, and oil flows through both the cooler and the branch at the same time; When the temperature rises above 80 ℃, the valve is completely closed, and the lubricating oil enters the machine head through the cooler to cool the lubricating oil to a large extent.

If the temperature control valve malfunctions, lubricating oil may enter the machine head directly without passing through the cooler, preventing the oil temperature from dropping and causing overheating. The main reason for its failure is that the elastic coefficient of the two thermal sensitive springs on the valve core changes after fatigue, and they cannot function normally with temperature changes; The second reason is that the valve body is worn, the valve core is stuck or the action is not in place and cannot be closed normally. It can be repaired or replaced according to the situation.

6. Check if the fuel volume regulator is functioning properly, and if necessary, increase the fuel injection rate appropriately.

The fuel injection quantity has been adjusted when the equipment leaves the factory and should not be changed under normal circumstances.

7. The oil has exceeded its usage time and deteriorated.

The fluidity of engine oil deteriorates and the heat exchange performance decreases. The heat from the air compressor head cannot be completely taken away, resulting in high temperature in the air compressor.

8. Check if the oil cooler is working properly.

For water-cooled models, the temperature difference between the inlet and outlet water pipes can be checked. Normally, it should be 5-8 ℃. If it is lower than 5 ℃, there may be scaling or blockage, which will affect the heat exchange efficiency of the cooler and cause poor heat dissipation. At this time, the heat exchanger can be removed and cleaned.

9. Check if the inlet temperature of the cooling water is too high, and if the water pressure and flow rate are normal. For air-cooled models, check if the ambient temperature is too high.

The inlet temperature of cooling water should generally not exceed 35 ℃, and the flow rate should not be less than 90% of the specified flow rate when the water pressure is between 0.3 and 0.5 MPA. The ambient temperature should not exceed 40 ℃. If the above requirements cannot be met, they can be solved by installing cooling towers, improving indoor ventilation, and increasing the space of the computer room. You can also check if the cooling fan is working properly. If there is a malfunction, it should be repaired or replaced.

10. The air-cooled unit mainly checks whether the temperature difference between the inlet and outlet oil is around 10 degrees. If it is less than this value, it should check whether the fins on the surface of the radiator are dirty or blocked. If it is dirty or blocked, clean air can be used to dust the surface of the radiator and check whether the fins on the radiator are corroded. If the corrosion is severe, it is necessary to consider replacing the radiator assembly and checking whether the internal pipelines are dirty or blocked. If this phenomenon occurs, a circulating pump can be used to clean with a certain amount of acidic solution, Be sure to pay attention to the concentration of the solution and the circulation time to avoid the radiator from penetrating the cavity due to the corrosion of the solution.

11. The problem with the fan of the air cooler is that the fan does not rotate, the fan is in reverse phase, and only one of the two fans is turned on.

12. There are issues with the exhaust duct installed by the air-cooled model customer.

There are exhaust ducts with too small ventilation surface, too long exhaust ducts, too many middle bends in the exhaust ducts, and too long exhaust ducts. There are many middle bends in the exhaust ducts, and there is no installed exhaust fan. The flow rate of the exhaust fan is lower than the original cooling fan of the air compressor.

13. The temperature sensor reading is not accurate.

14. The computer reading is not accurate.

15. Air end issue.

 Basically the bearings of compressor air end requires replacement within 20000 to 24000 hours, as the clearance and balance of the air compressor are determined by the bearings. If the wear of the bearings increases, it will cause an increase in compressor air end, resulting in high temperatures in the air compressor.

16. Incorrect specification or poor quality of lubricating oil.

 The lubricating oil for screw machines generally has strict requirements and cannot be arbitrarily substituted. The requirements in the equipment manual should prevail.

17. Check if the air filter is blocked.

 Blocking the air filter can cause excessive load on the air compressor, which can cause high temperatures if it is in a long-term loading state. It can be checked or replaced based on the alarm signal of the pressure difference switch. The common problem caused by clogging of air filters is a decrease in gas production, with high temperature in the air compressor being a secondary manifestation.

18. Check if the pressure is too high.

The system pressure is generally set at the factory. If adjustment is necessary, the rated gas production pressure marked on the equipment nameplate should be used as the standard. If the adjustment is too high, it will cause overheating due to the increase in machine load. This is also the same as the previous reason. High temperature of the air compressor is a secondary manifestation, mainly manifested by an increase in the motor current of the air compressor and the shutdown of the air compressor protection.

19. The oil gas separator is blocked.

Blocking the oil gas separator can cause excessive internal pressure, which can cause many problems, with high temperature being one of them. This is also the same as the first two reasons, the main manifestation of blockage in the oil gas separator is high internal pressure.

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