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How to deal with the oil separation failure of oil-free screw air compressor

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Update time : 2020-11-27 14:12:52
The common causes of oil separation in oil-free screw air compressors mainly include the following aspects: oil quality problems, air compressor system failures, improper installation of oil, and defective oil and gas separation system design. In actual use, we found that most of the failures were not caused by the quality of the oil. So, in addition to oil quality problems, what other reasons can cause oil to run out of oil? In practice, we have concluded that the following situations can also cause run out of oil:
1. Too much lubricating oil

Too much oil is added, exceeding the normal oil level (generally the oil level is 1/2 to 2/3), the separation effect of the oil and gas separator is not good, and some lubricating oil will be taken away with the airflow, resulting in excessive oil consumption.
    Solution: After the unit is shut down, after the air pressure in the oil separator barrel is released to zero, open the oil drain valve and drain the oil to the normal oil level (generally the oil level is 1/2 to 2/3).

2. Irregular design of oil and gas separation tank
If the air compressor is designing the oil and gas separator, the design of the primary separation system is unreasonable and the primary separation effect is unsatisfactory, resulting in a high concentration of oil mist before the oil intake, excessive oil load, insufficient processing capacity, and excessive fuel consumption.
Solution: Improve the design of the oil and gas separator to improve the effect of primary separation.

3. The oil return line is blocked or improperly installed
When the oil return pipe (including the check valve on the return pipe and the oil return filter screen) is blocked by foreign matter, the oil condensed at the bottom of the oil separator after separation cannot return to the machine head, and the condensed oil droplets are blown up by the airflow. It is taken away with the separated air. These foreign objects are usually caused by solid impurities dropped during installation. When replacing, cleaning, and repairing the air compressor, the oil return pipe is not inserted into the bottom of the oil separator (reference: 1~2mm from the bottom of the oil separator is better), resulting in the separated oil cannot return to the machine head in time, and the accumulated oil will follow Ran out with compressed air.

4. Use unqualified lubricants
Screw air compressors have high-temperature protection, and their trip temperature is usually about 110-120℃. When the air compressor uses unqualified lubricating oil, different degrees of fuel consumption will occur when the exhaust temperature is high (generally The higher the temperature, the greater the fuel consumption). The reason is that after the primary separation of the oil and gas separator barrel at high temperature, some of the oil droplets can have the same order of magnitude as the gas phase molecules. The molecular diameter is ≤0.01μm, and it is difficult to capture and separate the oil. , Resulting in excessive fuel consumption.

Solution: Find the cause of the high temperature, solve the problem and lower the temperature, and select good quality and qualified lubricating oil.

5. The check valve is damaged
If the oil return check valve is damaged (from one-way to two-way), the internal pressure of the oil separator tank will pour a large amount of lubricating oil back into the oil separator through the oil return pipe after shutdown. The next time the machine runs, the oil inside the oil separator will The machine head cannot be sucked back in time, causing part of the oil to run out of the air compressor with the separated air (this situation is common in machines without an oil circuit stop valve and machine head exhaust outlet check valve).

Solution: Check the one-way valve after disassembly. If there is any sundries, clean the sundries; if the one-way valve is damaged, replace it with a new one.

6. Pressure valve failure
If there is a leakage point in the seal of the pressure valve or the pressure valve is opened in advance (because the opening pressure of each manufacturer is different, usually in the range of 3.5~5.5kg/cm2), the time for the machine to establish the oil and gas tank pressure at the beginning of operation will be Increase, at this time, the gas oil mist concentration in the low-pressure state is high, the flow rate is fast when passing through the oil, the oil load is increased, the separation effect is reduced, and the oil consumption is large.
Solution: Check and repair the pressure valve and replace it if necessary.

(1) Stop the machine, and after the pressure of the oil drum is discharged to zero, remove all the pipe fittings of the oil return pipe and blow out the blocked foreign matter. When installing the built-in oil separator, pay attention to clean the oil and gas barrel cover, and pay attention to whether there are solid particles at the bottom of the oil separator core.
(2) Stop the machine and adjust the oil return pipe to a reasonable height after the pressure relief returns to zero (the oil return pipe is 1-2mm away from the bottom of the oil separator, and the oblique oil return pipe can be inserted into the bottom of the oil separator).

7. Large gas consumption, low-pressure use with overload
The low-pressure use of air compressor load means that when the user uses the air compressor, the exhaust pressure does not reach the rated working pressure of the air compressor itself, but it can basically meet the gas requirements of some enterprise users. For example: enterprise users increase the use of gas equipment, and the gas consumption increases, so that the air compressor discharge volume cannot be balanced with the user’s gas consumption. Assuming the rated discharge pressure of the air compressor is 8kg/cm2, the pressure is only 5kg in actual use /cm2 or even lower, so that the air compressor is under load for a long time and cannot reach the rated pressure of the machine, resulting in increased fuel consumption. The reason is that under the condition of constant displacement, the flow rate of the oil-gas mixture increases when passing through the oil, and the oil mist concentration is too high, which increases the oil load and ultimately leads to high oil consumption.