Preventing and Fixing Rotary Screw Air Compressor Overheating Problems
Check the Lubrication System
One important function of the lubricating oil in a rotary screw air compressor is to act as a coolant. When the amount of oil is insufficient or when some components of the lubrication system are malfunctioning, it can cause an increase in the oil temperature, resulting in an overheating failure.
Check if Oil is expired
If a rotary screw air compressor is running with oil that has been used past its recommended replacement date, the viscosity of the oil will decrease and its heat exchange capabilities will be weakened. This can lead to an increase in temperature due to inadequate heat removal from the compressor head.
Check whether Lack of Oil in the System
Oil level should slightly exceed the high marks when static, and cannot drop below the low marks when running. To check this, shut down and depressurize the gas chamber and then inspect the oil levels.
Check if Oil filter / Separator is Blocked
1. As the separator is made of multiple layers of glass fiber, it filters out oil mist in compressed air and prevents loss of lubricating oil. If the environment is bad with more dust, it’s better to shorten the replacement cycle accordingly.
2. Inspect the oil regulator to make sure it works properly and increase the amount of oil injection as necessary. The amount of oil injection has been adjusted when leaving the factory and should not be changed in general.
Check if shut-off valve is dysfunctional
The valve is used to prevent oil from being injected into the head and emitted from the intake when the machine is turned off. If the valve fails, there will be insufficient oil supplied to the system, causing it to rapidly heat up and potentially damaging the screw assembly in severe cases.
Check if thermostatic valve is malfunctioning
This valve is installed at the front of the oil cooler and its job is to maintain the temperature of exhaust gases above the pressure dew point. It works by allowing un-cooled lubricating oil to directly enter the head while the oil is cold, gradually closing as temperatures rise above 40°C, and fully shutting off when it reaches 80°C to ensure maximum cooling by passing the oil through an oil cooler before entering the head. If this valve fails, lubricating oil may bypass cooling, leading to dangerously high temperatures. Faults can arise due to worn valve body parts or tired heat sensitive springs that no longer respond to changes in temperature correctly. Depending on severity, repairs or replacements are necessary.
Check Air Compressor Cooling System
Rotary screw air compressors are usually cooled by either air or water.
Cooling System (air)
1.Check the environment temperature
If the temperature is high, it means the air is thinner and causes a lower working efficiency of the compressor. This leads to more time spent in loading state and creates more heat generated by the machine, resulting in a higher compressor temperature.
2.Check the fan operation
Check if there is an issue with the fans such as malfunctioning, running in reverse, or only one fan running.
3.Check the exhaust duct
Another potential cause of overheating could be problems in the exhaust duct such as inadequate size of the ventilation area, a long exhaust pipe, or too many bends in the pipe. However, this sort of design deficiency is generally less common.
Cooling system (water)
1.Check if the oil cooler is working properly
The temperature difference between the inlet and outlet pipes of the oil cooler should normally be 5℃ to 8℃. If it is lower than 5℃, there may be scaling or clogging, which will affect the heat exchange efficiency of the cooler and cause poor heat dissipation. In this case, you can remove the heat exchanger for cleaning.
In general, poor quality cooling water with high hardness rather than failures of devices itself are major reasons for abnormal work of oil coolers.
2.Check if the temperature of the incoming cooling water is too high, the water pressure, or the flow rate are adequate
The temperature of incoming cooling water should not exceed 35°C and one should make sure that the water pressure is between 0.15 and 0.3 MPa with a minimum flow rate of 90%. Companies often connect their air compressors with other equipment, creating a shared cooling system which can lead to too many accumulated contaminations which form scale on pipes’ walls. This reduces pipe volume resulting in reduced water pressure and inadequate flow. If environmental conditions don’t meet the requirements mention earlier, installing a cooling tower and improving indoor ventilation or increasing room space can help solve this issue.
Check intake and exhaust systems and control pipes
Overheating in a rotary screw air compressor can be caused by faulty or poorly operating intake and exhaust systems and control pipes.
Check whether or not the air filter is clogged
This can be checked by looking at the alarm signal from the pressure switch, or by replacing it.
Check is if the oil-gas separator gets clogged
Clogging of the separator affects air flow, resulting in excess internal pressure and therefore high temperature. To prevent this from happening, it is important to regularly check and replace the oil filter core. High internal pressure is usually an indicator of a clogged up separator. Hence it’s important to check and change the oil filter core as needed.
Check if minimum pressure valve is faulty
If a rotary screw air compressor’s minimum pressure valve is faulty, the internal pressure in the oil separator will increase. This will prevent the lubricating oil from circulating properly when starting, resulting in poorer oil-gas separation. This can lead to too much pressure difference across the oil-gas separator filter, leading to higher exhaust temperatures from the unit.
Check whether the system pressure is set too high
If the system pressure is adjusted too high, the load on the compressor will increase and cause an alarm for high temperature.The system pressure of the compressor is usually set at the time of shipment. If users need to adjust it, they should follow the rated pressure indicated on the equipment nameplate.
Overheating in a rotary screw air compressor can have several causes beyond those mentioned above, such as a faulty temperature sensor or unresponsive unloading valves. To ensure the compressor runs smoothly for an extended period of time, not only should regular weekly and monthly maintenance be done, but also professional training and learning should be increased to reduce operational mistakes and increase equipment efficiency in daily operations.
