Ice machine compressor refrigerant oil replacement cycle and method

As the "blood" of the ice maker group, the frozen oil mainly plays the role of lubrication, sealing, cooling, cleaning and noise reduction. Due to the high temperature in the use process, the frozen oil will be decomposed by heat and produce carbon accumulation, leading to the wear of compressor parts. The oil decomposition will react with the refrigerant to reduce the cooling effect, and the acid produced will cause strong corrosion of the compressor. Therefore, the frozen oil needs to be replaced after it has deteriorated for a certain amount of time.

Generally speaking, the industry recommends that the oil change cycle of open-type units is 2000-3000h, and the oil change cycle of semi-closed units is about 6000h. For ice maker manufacturers, the refrigerant oil replacement cycle of compressor is related to the process control of its production process. If the cleanliness control of the evaporator and condenser of the refrigeration system and the system pipeline is better, the pollutants entering the compressor are relatively less, and the replacement cycle can be relatively prolonged.

Suggestion: After starting the ice machine group for the first time, it is recommended to change the lubricating oil and clean the oil filter after running 2500 hours (or 3 months) accumulated. Because the residue of the system assembly will accumulate in the compressor after the official operation. In the future, replace it every 8000 hours (or 2 years), or replace it according to the method in the above table.

Chilled oil change indicator

Generally, the indicators to judge whether the frozen oil can continue to be used are: appearance, viscosity, acid value, moisture, pour point, flash point, compressive strength, copper corrosion, mechanical impurities and insoluble matter.

1 Appearance

Whether the quality of chilled oil changes or not should be determined through certain chemical and physical analysis. Usually in the process of use, you can also intuitively judge the quality of the oil from the appearance of the color. High-quality frozen oil should be colorless and transparent, and will become light yellow after a period of use. With the extension of use time, the color of the oil will gradually become darker and the transparency will become worse. If the refrigerant oil turns orange or reddish brown, replace it.

2 Viscosity

The kinematic viscosity of frozen oil is the main index to reflect the lubricating property of oil, and also the basis for many countries to formulate the grade of frozen oil. Too large viscosity can not only guarantee the low temperature performance of the oil, is not conducive to heat transfer, and will reduce the power of the machine; If the viscosity is too small, the oil film can not be formed in the friction part, resulting in increased equipment wear, and even "pull cylinder", "bonding" and other failures.

3-acid number

Acid value is an important index of chilled oil, and its corresponding test method is GB/T4945 or GB/T7304. The acid value in frozen oil reflects the refining depth and oxidation degree of oil to some extent.

4 Moisture

In the refrigeration cycle system, even a small amount of moisture can produce ice jam at the low temperature throttling device and lead to premature flocculation of frozen oil. Moisture also reduces the stability of the oil at high temperatures. On the other hand, closed refrigerant oil is in direct contact with the motor coil, and the existence of moisture will cause insulation destruction, and even motor breakdown accident.

5 pour point

The lowest temperature at which an oil happens to flow is called the pour point. When the refrigerant is compressed, some oil mist often enters the pipeline. Even after the oil and gas separator, the two can not be separated clean, which requires the oil to have good low temperature liquidity (low pour point) in the freezing system, so as not to block the throttle part of the chiller to stop working or adhere to the evaporator heat exchange tube to reduce the heat transfer efficiency.

6 flash point

The flash point of frozen oil refers to the lowest temperature at which flash occurs when the oil vapor generated during heating is mixed with air. If the flash point of the frozen oil is reduced, it means that the oil is mixed with light oil or some oil has been decomposed to produce low boiling point decomposition products. Generally speaking, the flash point of the refrigerant oil is 15-30 ° C higher than the compressor outlet temperature.

7 Compressive strength

Voltage strength, also known as breakdown voltage or dielectric strength, refers to the frozen oil into a container with an electrode to apply voltage, when the voltage gradually increases to a certain value, the resistance of the oil suddenly drops to zero, the powerful current in the form of spark or arc through the oil, at this time the critical voltage value is called dielectric strength. The main factors affecting the breakdown voltage of refrigerant oil are moisture, impurities, temperature and so on.

8 Copper corrosion

Copper corrosion test is the most important corrosion measurement method of industrial lubricating oil at present. It is a test of corrosion tendency of oil and metal surface in contact under specified conditions. Corrosion resistance of oil can reflect the refining depth and deterioration degree of oil to a certain extent.

9. Mechanical impurities and insoluble matter

Mechanical impurities are one of the routine monitoring items of the chiller compressor lubrication management, because the mechanical impurities in the oil will accelerate the abnormal wear of the compressor, but also plug the oil circuit and filter, leading to the compressor lubrication failure. Mechanical impurity is one of the indicators to determine whether the refrigerant oil needs to be changed. In general, mechanical impurities below 0.005% are considered to be free of mechanical impurities. If it exceeds 0.005%, it contains mechanical impurities and is judged to be unqualified.

Procedure Replace refrigerant oil

The method of replacing refrigerant oil is different for different compressors. This paper takes screw compressor as an example.

Screw compressor freezing oil replacement method:

1. Recover the system refrigerant to the condenser side, remove the refrigerant in the compressor, and discharge the frozen oil from the oil discharge Angle valve of the compressor.

2. The lubricating oil of the compressor is released from the oil discharge valve on the oil filter. When the lubricating oil is close to the end, add some nitrogen from the detection joint of the high pressure end of the compressor, speed up the discharge of lubricating oil with pressure, stop the injection pressure, and close the oil discharge valve. Then remove the oil filter of the compressor, release all the lubricating oil in the oil tank, and then install the tight oil filter after cleaning.

3. Fill lubricating oil according to the standard amount of compressor and pump out the system at the same time. It is recommended that the high (low) pressure side Angle valve or other high point be used as the contact point of the vacuum pump to prevent refrigerant oil from damaging the vacuum pump. Observe whether the pressure bounces back during vacuum pressure preservation or leak detection.

4. Inject lubricating oil, connect it to the oil discharge valve with a clean plastic pipe, and put the other end of the plastic pipe into the oil drum (the plastic pipe is placed at the bottom of the oil drum). When filling oil, the oil drum should be closed to reduce air pollution to oil.