Problem of oil not returning to the liqueifier in screw compressor units

1. “Open the return valves of the three liquefiers” – that doesn’t seem right... It’s the return valve located in the oil layer that needs to be opened; if all three are opened, it will be difficult to allow oil to flow back. 2. The level of Freon is fluctuating, but it should remain relatively stable under conditions of relative stability. If it is not stable, it means that the valves before and after the Freon inlet solenoid valve are opened too wide; adjust them slightly to prevent the solenoid valve from operating frequently. After all, those are just coarse-control valves. 3. Returning oil is a task that requires time and patience; assign a suitable person to handle it. Going back once a week is enough!

My sister is right; first, we need to stabilize the level of Freon, and then start the process of returning oil to its proper level. This process happens slowly – it doesn’t happen all at once. The layer of oil on the surface of the Freon is actually very thin, so it requires patience and time, just like when skimming oil from a soup with a spoon. The valve should be left slightly open; if the pressure difference seems low, the return air main valve can also be closed a bit. The return valve should be opened one by one from top to bottom to allow oil to return, and haste should be avoided. The oil should be returned frequently; do not wait until it deteriorates, solidifies, and adheres to the pipe walls. Determine the frequency based on your actual circumstances. The temperature of the oil cooler is very important; cooling needs to be enhanced to maintain the oil’s temperature. Ensuring an adequate circulation rate of cooling water and minimizing exhaust pressure to thereby reduce exhaust temperature can effectively slow down the rate of oil degradation. Keep the liquid level in the oil separator as low as possible.

Check the level of R22 in the liquefier; if the level of R22 is below the oil return port, then oil cannot return properly. The opening degree of the oil return valve should decrease gradually from top to bottom. Additionally, oil returns from the condenser of the refrigeration unit, so check the opening degree of that oil return valve (we have experienced incidents where the oil level in the main tank dropped due to this valve being closed, resulting in the compressor shutting down as a safety measure).

First of all, I would like to thank the three gentlemen for their prompt responses. There are still some points I don’t understand in their answers, so I would like to ask further questions: These are the parameters of our machine set. Inlet pressure: 0.12 MPa; inlet temperature: -19°C; outlet pressure: 1.08 MPa; outlet temperature: 62.3°C; oil temperature: 44°C; efficiency level: 96. Please help me check whether there are any abnormalities in our operating parameters Our circulating water has reached its maximum level; it can no longer be cooled further. Everyone says that the oil temperature should be kept as low as possible, but I think it can’t be too low either; too low a temperature makes it easier for oil to leak. I’m not sure if my understanding is correct Also, I always feel that our unit’s output doesn’t reach its rated design capacity. Of course, I can do the calculations myself; what do you think?

I wonder if the valve for returning oil back is slightly open in your system? Based on the data analysis, there are no issues with the operation.

Based on the parameters you provided, our previous assessments are no longer appropriate. I think the system isn’t supplying enough liquid; the liquefier hasn’t reached the level at which oil can be discharged. The exhaust pressure is 1.08, the intake pressure is 0.12, and the compression ratio is only 4.9; as a result, the exhaust temperature is very low, at just 62 degrees. Judging from the pressure-humidity diagram, these data are generally reasonable. The reason for such a low temperature in the pressure chamber is the low suction pressure; in addition, the suction temperature is also high. Therefore, it can be attributed to a low supply volume of liquid to the evaporator. I wonder if the chlorine pressure of yours is high. And the lack of return oil is precisely the reason for the low liquid level. As for the fate of the oil, it remains within the system; not only is there oil in the evaporator, but also in the condenser and the liquid storage tank. Especially in the evaporator, as the oil deteriorates, it adheres to the walls of the tubes. Under normal operating conditions, the machine must have its oil replenished according to the oil level. My sister spoke very practically, and her views on the soul make sense as well; they are all based on practical experience. The original poster still has to rely on their own efforts to solve the problem. It should be noted that Wu Leng’s machines are capable of achieving the designed cooling capacity without any problems. Chlorine liquefaction can be easily achieved under conditions of -25°C/35°C.

Thank you once again for your concern and answers. The liquid level of fluorine in our liquefier is indeed unstable; the gauge I saw was full of foam, making it impossible to tell whether it was liquid fluorine or gas. It was also impossible to see where the actual liquid level was. My sister said it’s because the opening degree of the supply valve is too high, right? Also, of the three oil return valves in the liquefier, only the one near the oil level is opened; the others remain closed. Is this valve also slightly open? Is the oil return valve on the heat fluorizer slightly open? Is the return oil valve located before that suction check valve at the nose of the machine also slightly open? Our free chlorine pressure is between 0.14 and 0.15. Low suction pressure and high suction temperature indicate insufficient Freon, while low exhaust pressure and low exhaust temperature are likely due to an excessive opening degree of the circulating water.

Low exhaust pressure and exhaust temperature are due to a large opening degree of the circulating water??? A lack of Freon is the main cause. For level gauge issues, you can check for frost! Aren’t there two level gauges? The return valve on the heat fluorizer is fully open, and the return valve in front of the suction check valve is also fully open. You can call the manufacturer for consultation

With a constant amount of circulating water, an increase in the suction pressure leads to an increase in the exhaust pressure as well. However, the temperature and flow rate of the circulating water remain relatively stable; therefore, the increase in exhaust pressure is not proportional to the increase in suction pressure. The exhaust temperature depends only on the compression ratio; you can check the pressure-temperature diagram. You can find the R22 pressure-han diagram by searching on the Haichuan Forum.

There are two level gauges; it seems that the one affected by frosting doesn’t give very accurate readings of the frost level. I have another question: We have a backup unit, and when it’s in standby mode, the fluorine level indicated by the glass gauge on the liquefaction tank is sometimes visible and sometimes not. When it does appear, there’s a lot of foam – similar to the foam produced by washing powder – which rises rapidly before sinking back down into the liquefaction tank. At this time, we have the supply valve closed. I really can’t figure it out. I’d like to ask the experts here: what’s going on here?