Cause Analysis and Solution of Oil Separation Leakage of Oil Injection Screw Air Compressor

In the daily production and operation of oil-injected screw air compressors, the oil leakage of the air compressor is one of the common faults. The reasons for the oil leakage of the air compressor mainly include the following aspects: oil quality problems, improper oil installation, air compressor engine system failure, oil-gas separation system design defects, etc. In the actual use process, we found that most of the malfunctions were not caused by the quality of the oil. So, besides the oil quality problem, what other reasons can cause the oil to run out?

1. Use unqualified lubricating oil

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

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

2. Too much lubricating oil

If the amount of refueling is too much, exceeding the normal oil level (generally 1/2 to 2/3), the separation effect of the oil-gas separator is not good, and part of the lubricating oil will be taken away with the air flow, resulting in excessive fuel consumption.

Solution: After the unit stops, after the air pressure in the oil-gas 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 1/2~2/3).

3. Minimum pressure valve failure

If there is a leakage point at the seal of the minimum pressure valve or the minimum pressure valve is opened in advance (because the opening pressure of each manufacturer is different, usually the range is between 3.5~5.5kg/cm2), then the time for the machine to establish the pressure of the oil and gas tank at the beginning of operation At this time, the concentration of gas oil mist in the low pressure state is high, the flow velocity is fast when passing through the oil, the load of the oil is increased, the separation effect is reduced, and the fuel consumption is large.

Solution: Overhaul the minimum pressure valve and replace it if necessary.

4. The one-way valve is damaged

If the oil return check valve is damaged (change 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 the 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 that are not equipped with an oil circuit stop valve and a one-way valve for the exhaust outlet of the machine head).

Solution: Check the one-way valve after dismantling it. If there is debris stuck to it, just clean it up. If the one-way valve is damaged, replace it with a new one.

5. The oil return line is blocked or improperly installed

When the oil return line (including the one-way valve on the oil return line and the oil return filter) is blocked by foreign matter, the oil that has been condensed at the bottom of the oil component after separation cannot return to the machine head, and the condensed oil droplets are blown up by the air flow. It is taken away with the separated air. These foreign objects are usually caused by solid impurities dropped during installation. When replacing, cleaning, and maintaining the air compressor, the oil return pipe is not inserted into the bottom of the oil separator (reference: 1~2mm from the arc center of the bottom of the oil separator is better), so that the separated oil cannot return to the machine head in time, and the accumulated oil will follow Run out with compressed air.

Solution:

(1) Stop the machine, remove all the pipe fittings of the oil return pipe after the pressure of the oil barrel is released to zero, 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 at the same time, pay attention to whether there are solid particles remaining at the bottom of the oil separator core.

(2) Stop the machine, and after the pressure release returns to zero, adjust the oil return pipe to a reasonable height (the oil return pipe is 1~2mm away from the bottom of the oil separator, and the oil return pipe with an oblique opening can be inserted into the bottom of the oil separator).

6. Large gas consumption, overload and low pressure use

The low-pressure use of the 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 air consumption requirements of some enterprise users. For gas equipment, the air consumption increases, so that the exhaust volume of the air compressor and the air consumption of the user cannot be balanced. Assume that the rated discharge pressure of the air compressor is 8kg/cm2, but the actual pressure is only 5kg/cm2 or even lower. The air compressor is in the load operation state for a long time and cannot reach the rated pressure value of the machine, resulting in an increase in fuel consumption. The reason is that under the condition of constant displacement, the flow velocity of the oil-gas mixture increases when passing through the oil, and the concentration of oil mist is too high , so that the oil load increases, eventually leading to high fuel consumption.

Solution: It is recommended to contact the manufacturer to replace an oil product that can match the low pressure.

7. The design of the oil and gas separation tank is not standardized

If the air compressor is designed with an oil-gas separator, the design of the primary separation system is unreasonable, and the primary separation effect is not ideal, so that the concentration of oil mist before the oil inlet is high, the oil load is too heavy, and the processing capacity is insufficient, resulting in high fuel consumption.

Solution: Improve the design of the oil-gas separator to improve the effect of primary separation.

Conclusion

Oil leakage from the air compressor will cause the oil content in the air at the outlet of the air compressor to exceed the standard. Some production equipment was damaged to varying degrees. If the air compressor has oil leakage, do not simply blame the problem on the oil, but should conduct a systematic, scientific and reasonable inspection of the air compressor, and eliminate the influencing factors one by one, so as to find out the real reason and propose effective treatment measures. Therefore, in order to ensure the safe and stable operation of the unit, the daily and regular maintenance of the unit should be strengthened; the unit should be regularly inspected and inspected at fixed points to timely discover hidden dangers during the operation of the unit to ensure the safe operation of the unit. At the same time, post operators must operate in strict accordance with equipment safety operating procedures, and illegal operations are strictly prohibited. Only by adhering to scientific management in this way can we reduce the failure rate of equipment, reduce equipment maintenance and management costs, ensure the safe operation of equipment, and improve the economic benefits of enterprises.

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