Six reasons and solutions for oily exhaust of screw air compressors
Failure factors of screw engine exhaust with oil
Among the failures of screw compressors, the faults with oil in the exhaust are the most common. The main factors that cause the faults with oil in the exhaust are:
1 The oil separation core is damaged
During the operation of the screw compressor, if the oil separation core is damaged, such as breakage or perforation, it loses the role of oil and gas separation. That is to say, the mixed gas and the exhaust pipe of the compressor are directly connected, so a large amount of cooling oil is not separated, and it will be discharged out of the body along with the gas, causing an oil-carrying fault during the exhaust process.
2 The return line is faulty
In the working process of the screw compressor, the oil return pipeline shoulders important responsibilities. A pressure difference is formed between the inside of the oil separation core and the compressor inlet. Under the action of this pressure difference, the oil return pipeline is responsible for removing the oil. The oil collected at the bottom of the separation core is transported back to the compressor for continued use during the next cycle. If the oil return path is blocked, broken, or installed incorrectly, the oil collected at the bottom of the oil separation core cannot be transported back to the compressor, resulting in excessive oil accumulation at the bottom, which is not transported back to the compressor. As the gas is exhausted, oil will appear during the exhaust process.
3 System pressure control is too low
During the operation of the screw compressor, the system pressure control is too low, which will cause the centrifugal force in the separator to be less than the required centrifugal force of the work, then the function of the separator will not be fully reflected, and it will cause the separator to enter the next stage. The oil content of the gas in the core is too high, which exceeds its separation range, which leads to incomplete separation of oil and gas, and an oil-carrying fault occurs during the exhaust process of the compressor.
4 The minimum pressure valve fails
During the operation of the screw compressor, the function of the minimum pressure valve is to ensure that the system pressure is controlled above the minimum pressure during the operation. If the minimum pressure valve fails, the minimum pressure of the system will not be guaranteed. Because the air consumption of the air transport equipment is very large, the system pressure will be too low and the oil return line cannot return oil. The oil accumulated at the bottom of the oil separator core will not be able to return to the compressor, and will be discharged from the compressor with the compressed gas, causing oil-carrying failure during the flat exhaust process.
5 Too much cooling oil is added to the compressor
Before the screw compressor is operated, too much cooling oil is added, which exceeds the range of the compressor. During the operation of the compressor, due to the high oil level, although the separation system separates the oil and gas, it is The gas will also involve the cooling oil into the gas and discharge it, resulting in too high oil content in the discharged gas, causing oil-carrying faults.
6 Unqualified cooling oil quality
Before the compressor is running, unqualified cooling oil is added, or the cooling oil exceeds the applicable time, and the cooling effect cannot be achieved. Then during the operation of the screw compressor, the cooling oil loses its function and cannot separate the oil and gas. Then there will be oil faults during the exhaust process.
Fault inspection and troubleshooting steps
When oil is found in the exhaust of the compressor, it is not necessary to blindly disassemble the equipment, but to analyze the above causes and follow the steps from easy to difficult to determine the location of the fault. This can reduce a lot of repair time and manpower.
When the compressor starts normally and the system reaches the rated pressure, slowly open the exhaust gate valve, with the opening as small as possible to allow a small amount of gas to be discharged. At this time, use a piece of dry paper towel to face the exhaust airflow. If the paper towel changes color immediately and has oil droplets, it can be judged that the compressor's exhaust has excessive oil. According to the amount of oil in the exhaust gas and different time periods, the fault location can be correctly judged.
When increasing the opening of the exhaust gate valve, it is found that the exhaust airflow is in the form of uninterrupted dense fog, indicating that the airflow contains a large amount of oil, and then check the oil return situation of the oil return pipe observation mirror. If the oil return of the oil return pipe observation mirror increases significantly, it is usually because the separator core is damaged or the separator's cooling oil has been added too much; if the oil return pipe observation mirror does not return oil, the return pipe is generally broken or blocked.
When the opening of the exhaust gate valve is increased, it is found that the front part of the exhaust airflow is in a dense mist shape, and it becomes normal after a period of time; continue to increase the opening of the exhaust gate valve, open all the exhaust valves, then observe the system pressure gauge , If the display pressure of the pressure gauge is lower than the set pressure of the minimum pressure valve, the exhaust valve is still exhausting and the airflow is in an uninterrupted dense mist. When this phenomenon occurs, the fault is generally the failure of the minimum pressure valve.
After a normal shutdown, the automatic vent valve will exhaust. If there is a large amount of oil in the exhaust, the automatic vent valve is damaged.
Common troubleshooting measures
There are various reasons for the failure of the screw compressor with oil in the exhaust during operation, and different reasons require different solutions.
01 Damaged oil separation core
Oil separation core damage is a common phenomenon, so the equipment should be inspected before the operation of the screw compressor, and the operating procedures should be strictly followed during use, and the equipment should be maintained regularly after use. If the oil separation core is found to be damaged or perforated, it should be replaced in time to ensure the normal operation of the equipment.
02 There is a problem with the return line
During the operation of the equipment, if the oil return line is blocked, the pressure drop of the separator should be checked first. If there is no problem with the pressure drop, the oil separator core needs to be cleaned. If the oil separator core breaks, it must be timely Replace it.
03 System pressure control is too low problem
For the operator, he should be familiar with the control pressure of the equipment, and when a problem is found, reduce the load of the system so that the system pressure reaches the rated working pressure.
04Minimum pressure valve failure problem
In the actual operation, if the minimum pressure valve is found to be invalid, it must be replaced, and the work can be performed after the replacement is completed.
05 The problem of adding too much cooling oil to the compressor
When adding cooling oil to the compressor, you should first understand the theoretical value of how much cooling oil should be added to the equipment, and a special person should be responsible for the addition of cooling oil. Generally, it should be controlled below the middle of the sight glass.
06 Cooling oil quality problem
The cooling oil should be added strictly in accordance with the equipment's requirements for cooling oil, because different equipment has different requirements for cooling oil. The time of addition should be recorded after addition, and the cooling oil should be replaced on time when it reaches the service life. The quality of the added cooling oil should be strictly controlled to prevent the addition of unqualified cooling oil.
Precautions for exclusion and resolution
There are several points that must be paid attention to in the process of troubleshooting, otherwise the fault will not only be eliminated, but may lead to greater consequences.
If it is determined that the oil return pipe is the problem, the oil return pipe can be cleaned and blocked or re-welded. Attention should be paid to this process: firstly, the oil return pipe must be kept unobstructed, and the inner diameter of the pipe must not be reduced due to welding; secondly, the installation position of the oil return pipe must be correct, generally the gap between the center recess at the bottom of the separator core and the end of the oil return pipe Between 3～4mm.
If it is determined that the separator core is the problem, only replace the separator core. Attention should be paid in this process: first, carefully check whether the new separator core is deformed or damaged; second, clean the junction surface of the separator cylinder and the top cover; finally, check the separator core during installation Is there any conductor such as metal on the sealing paper pad on the top? Because the cooling oil rotates at a high speed inside the separator, a large amount of static electricity will be generated on the separator core.
If it is judged that the oil level of the separator is too much, it should be discharged appropriately. The method of checking the oil level of the separator should be correct. First, the unit must be parked horizontally. If the tilt angle of the unit is too large, the oil level gauge of the separator will be inaccurate; secondly, the inspection period should be half an hour before starting or stopping. Rear.
Although the screw compressor is a highly reliable model, it does not require maintenance and maintenance. It should be noted that any equipment is "three points in use, seven points in maintenance", therefore, regardless of exhaust gas oil or other faults, maintenance work should be strengthened in operation to eliminate the fault in the bud.
