As the heart of the refrigeration system, the common fault of the compressor is the mechanical damage caused by poor lubrication.

There are two main phenomena of poor lubrication: one is that there is not enough lubricating oil, that is, lack of oil; one is that there is no shortage of lubricating oil, but it causes poor lubrication.

1. lack of oil

In order not to let the compressor lack of oil, many compressors are equipped with an oil separator on the exhaust to ensure the rapid return of the compressor. My compressor as the heart of the refrigeration system, the most common fault, is because of poor lubrication caused by mechanical damage. We know that Freon refrigerant and lubricating oil are partially miscible. There are about 2-3% lubricating oil in the exhaust of semi-sealed piston and screw compressors, and 0.5-1% for scroll compressors. Even if the oil is installed, only part of the refrigerant oil can be separated, and there will always be a part of the refrigerant oil to the system. Assuming a 6-cylinder compressor with a displacement of 100 m3/hr and a crankcase oil storage capacity of 5 liters, 3% Ben oil means about 0.3-0.8 liters/minute of Ben oil, or the operation time of the compressor without oil return is more than ten minutes. That is to say, for a small stand-alone system, even if there is no oil content and such a small amount of oil, as long as the system is installed and the oil return is good, we only need to supplement a small amount of refrigerating oil, so that the refrigerating oil can reach a balanced cycle in the whole system, and the compressor will not be damaged due to lack of oil. Large systems, even if oil and oil collectors are installed, it is also necessary to add a part of the oil at the beginning of the startup to make the oil in the system reach a balanced state. However, if the oil return of the system is not good, the refrigerating oil in the compressor and the oil collector will all go to the system in a short time and stay in the system, causing the compressor to lack oil.

So, how can the refrigeration oil in the system return to the compressor smoothly?

When designing the pipeline, the pipe diameter should meet the oil flow rate of the refrigerant required by the refrigeration design manual, so that the refrigerant oil can follow the flow of the refrigerant and circulate back to the compressor.

We know that Freon refrigerant and lubricating oil are partially miscible, and there are about half-sealed piston and screw compressor exhaust.2-3% lubricating oil, while scroll compressor is 0.5-1%. Even if the oil is installed, only part of the refrigerant oil can be separated, and there will always be a part of the refrigerant oil to the system. Assuming a 6-cylinder compressor with a displacement of 100 m3/hr and a crankcase oil storage capacity of 5 liters, 3% Ben oil means about 0.3-0.8 liters/minute of Ben oil, or the operation time of the compressor without oil return is more than ten minutes. That is to say, for a small stand-alone system, even if there is no oil content and such a small amount of oil, as long as the system is installed and the oil return is good, we only need to supplement a small amount of refrigerating oil, so that the refrigerating oil can reach a balanced cycle in the whole system, and the compressor will not be damaged due to lack of oil. Large systems, even if oil and oil collectors are installed, it is also necessary to add a part of the oil at the beginning of the startup to make the oil in the system reach a balanced state. However, if the oil return of the system is not good, the refrigerating oil in the compressor and the oil collector will all go to the system in a short time and stay in the system, causing the compressor to lack oil.

So, how can the refrigeration oil in the system return to the compressor smoothly?

When designing the pipeline, the pipe diameter should meet the oil flow rate of the refrigerant required by the refrigeration design manual, so that the refrigerant oil can follow the flow of the refrigerant and circulate back to the compressor.

The construction process of the pipeline should ensure the smooth flow of oil. When the liquid pipe branches out from the main pipe, the branch pipe is connected from the bottom or side of the main pipe.

③ On the return pipe, where there is a horizontal upward pipeline, the oil return bend should be installed, and the oil return bend should be as compact as possible to reduce the oil storage.

④ The tracheal branch pipe is inserted into the main pipe from the upper part; when the return main pipe is branched, the branch pipe should be inserted into the bottom of the main pipe.

⑤ All refrigeration pipes should be along the direction of refrigerant flow to ensure a downward slope of about 1%. The slope should not be too large, lest the refrigerant liquid flow back to the compressor too fast.

⑥ The oil return line of the system with large load changes must also be careful. When the load decreases, the return air speed will decrease, and too low speed is not conducive to oil return. In order to ensure oil return under low load, the vertical suction pipe can be double vertical pipe.

⑦ The frequent start of the compressor is not conducive to oil return. Because the continuous operation time is very short, the compressor stops, and there is no time to form a stable high-speed airflow in the air return pipe, so the lubricating oil can only stay in the pipeline.

2. it seems that there is no shortage of lubricating oil, it causes poor lubrication.

Sometimes the compressor seems to be damaged in an instant, the oil pressure difference has not had time to protect, or the oil level in the crankcase of the compressor does not look low, the oil pressure difference does not alarm and protection to stop the compressor, but a lack of oil failure has occurred, what is going on. During the shutdown of the compressor, if there is a large amount of refrigeration liquid in the crankcase, because the volume weight of Freon is greater than that of the refrigerating oil, it will be deposited at the bottom. When the compressor is turned on, the pressure of the crankcase will decrease rapidly, causing the refrigerant to evaporate rapidly, and all the refrigerating oil will be brought into the cylinder. The speed is very fast, because all the protection will have a delay. When there is no protection, the refrigerating oil. At this time, not only the operating part of the compressor will be damaged, the cylinder may also be due to the non-compressor characteristics of the liquid, causing damage to the cylinder valve plate. Therefore, it is very important to observe the oil level of the crankcase or high-pressure oil and the frosting of the compressor when it is just turned on. If it is found that the refrigerating oil becomes muddy,There seems to be bubbles, and the frost on the intake end of the compressor is serious, which is a very dangerous sign. The harm of liquid back to the normal boot is to dilute the lubricating oil. After the diluted lubricating oil reaches the friction surface, the viscosity is low and a protective oil film of sufficient thickness cannot be formed, which will cause wear over time. When the amount of liquid back is relatively large, the lubricating oil will be very thin, not only can not play a lubricating role, but also dissolve and wash the original oil film, causing refrigerant wash.

However, because the refrigerant is a liquid like the refrigerating oil, its flow can generate a pressure difference, which makes the oil pressure difference or the oil flow switch mistakenly believe that the refrigerating oil is normal, and will not issue an alarm and protection instructions, which will eventually cause wear and damage.

So, how to avoid the production of liquid back?

① If the evaporator is higher than the compressor, the return pipe of the evaporator will go through an oil return bend, rise to above the middle part of the evaporator or air cooler, and then run the pipe horizontally. For systems that rely on temperature shutdown, this One point is more important;

②The installation of the expansion valve's temperature bulb and balance pipe must comply with the specifications. The temperature bulb should be placed in the pipe section between the oil return bend and the evaporator, and it is best to place it in the middle or upper position on the side, so that the expansion valve The opening degree is consistent with the return air superheat;

③The closer the distance between the liquid supply solenoid valve and the evaporator, the better, to avoid that after the solenoid valve is closed, there is still a large amount of refrigerant supplied to the evaporator; ④After the exhaust pipe is separated from the oil, it is best to make an inverted U-shaped bend, To avoid long-term shutdown, the condensed liquid falls back from the exhaust pipe to the oil and enters the compressor.

⑤ For long-term shutdown, when restarting, at least 48 hours in advance to the compressor to allow the crankcase heater to evaporate the possible liquid refrigerant. And just boot, to do a good job of oil level observation and recording.

1. Low oil level failure: 1. Refrigerant is mixed into oil 2. Heater is not running 3. The higher the temperature, the lower the dissolution.

Add oil to the middle of the upper mirror.

2If the refrigerant is added less, the evaporator pressure will be reported to be too low.

3Refrigerant impure or lack of fluorine.

4If the oil pressure difference is low (general screw machine) is lower than 400, alarm will be given, and the condenser valve will be opened small (water flow is small) as long as the condenser water temperature is higher than that of the evaporator.

5The exhaust pressure is too high. If the temperature exceeds 5 degrees, the flow rate is too low and the flow rate is diverted (flowing to other devices). This situation will turn off other water pipe switches. The oil is high pressure, the compressor is low pressure, the condenser pressure is high, and the evaporator pressure is low

Six. Compressor water inlet: the copper pipe is broken or the evaporator temperature is too low or the copper pipe quality is poor.

SevenWhen the spring and autumn started, the oil pressure was reported to be too low: reason: lack of oil, small load demand, oil will run into the system. In this case, turn off the oil switch and then turn it on.

EightYork's after-sales oil is only guaranteed for 3 months, usually by the hour, and the compressor runs for 1,000 hours.