The oil used for lubrication of the moving parts in the refrigeration compressor is called refrigeration oil, also known as lubricating oil. According to the standards of the Ministry of Petrochemical Industry, there are five grades of refrigeration oils produced in China, namely, No. 13, No. 18, No. 25, No. 30 and No. 40 of the enterprise standard. Among them, the commonly used refrigeration compressor lubricants are No. 13, No. 18 and No. 25, R12 compressors generally choose No. 18, R22 compressors generally choose No. 25.
In the compressor, refrigeration oil mainly lubrication, sealing, cooling and energy regulation of four roles.
(1) Lubrication
Refrigeration oil in the operation of the compressor lubrication, in order to reduce the degree of friction and wear and tear of the compressor operation, thereby extending the service life of the compressor.
(2) Sealing
Refrigeration oil plays a sealing role in the compressor, so that the compressor piston and cylinder surface, between the rotating bearings to achieve the sealing effect, in order to prevent refrigerant leakage.
(3) Cooling
When lubricated between the moving parts of the compressor, the refrigerant oil can take away the heat generated during the working process, so that the moving parts maintain a lower temperature, thus improving the efficiency and reliability of the compressor.
(4) Energy regulation
For the refrigeration compressor with energy regulation mechanism, can use the oil pressure of the refrigerant oil as the power of the energy regulation machinery.
First, what are the requirements of refrigeration equipment on the refrigeration oil
Due to the use of different occasions and refrigerants, refrigeration equipment on the choice of refrigeration oil is not the same. Requirements for refrigeration oil have the following aspects:
1, viscosity
Refrigeration oil viscosity oil characteristics of an important parameter, the use of different refrigerants to choose different refrigeration oil accordingly. If the viscosity of the refrigeration oil is too large, the mechanical friction power, friction heat and starting torque increases. On the contrary, if the viscosity is too small, it will make the movement between the parts can not form the required oil film, so as not to achieve the desired lubrication and cooling effect.
2, turbidity point
The turbidity point of the refrigeration oil is the temperature is reduced to a certain value, the refrigeration oil began to precipitate paraffin, so that the lubricating oil becomes turbid temperature. Refrigeration equipment used in refrigeration oil turbidity point should be lower than the evaporation temperature of the refrigerant, otherwise it will cause throttle valve blockage or affect the heat transfer performance.
3, solidification point
Refrigerant oil in the experimental conditions of cooling to stop the flow of the temperature known as the freezing point. Refrigeration equipment used in the freezing point of refrigeration oil should be as low as possible (such as R22 compressor, refrigeration oil should be below -55 ℃), otherwise it will affect the flow of refrigerant, increase the flow resistance, resulting in poor heat transfer.
4, flash point
The flash point of the refrigerant oil is the lowest temperature at which the lubricant is heated to the point where its vapour ignites in contact with a flame. Refrigeration equipment used in the refrigeration oil flash point must be higher than the exhaust temperature of 15 ~ 30 ℃ or more, so as not to cause combustion and coking of lubricating oil.
5, chemical stability and oxygen resistance
Pure lubricating oil chemical composition is stable, not oxidation, will not corrode metal. However, when the lubricant contains refrigerant or water will produce corrosion, lubricant oxidation will generate acid, corrosion of metal. When the lubricant at high temperatures, there will be coke, if this material attached to the valve plate, will affect the normal operation of the valve plate, at the same time will cause the filter and throttle valve clogging. Therefore, it must be selected with chemical stability and oxidation resistance are good freezer lubricant.
6, moisture and mechanical impurities
If the lubricating oil contains water, will exacerbate the chemical changes in the oil, so that the oil deterioration, resulting in corrosion of the metal, but also in the throttle valve or expansion valve to cause “ice blockage”. The lubricating oil contains mechanical impurities, will aggravate the friction surface wear of the moving parts, and soon block the filter and throttle valve or expansion valve, so the freezer lubricating oil should not contain mechanical impurities.
7, insulation performance
In the semi-closed and fully enclosed freezer, freezing lubricating oil and refrigerant are directly and motor windings and terminal contact, thus requiring the lubricant has a good insulating properties and high breakdown voltage. Pure lubricating oil insulation performance is good, but contains water, impurities and dust, its insulation performance will be reduced, the general requirements of the freezer lubricating oil breakdown voltage of 2.5KV or more.
8, due to the characteristics of various types of refrigerants are different, the working temperature of the refrigeration system varies greatly, the freezer lubricant can generally be selected in this way: low-speed, low-temperature conditions of the refrigeration equipment can be selected viscosity, low freezing point of lubricants; and high-speed or air-conditioning conditions of the refrigeration equipment should be selected viscosity, freezing point of high lubricants.
二、 Specification for the use of compressor refrigeration oil
1. The HFC-134a (R-134a) air conditioning system and HFC-134a (R-134a) components can only use the specified refrigerant oil. Non regulated refrigeration oil will affect the lubrication effect of the compressor, and the mixing of different grades of refrigeration oil can cause oxidation and failure of the refrigeration oil, which may lead to compressor failure.
2. HFC-134a (R-134a) stipulates that refrigeration oil can quickly absorb moisture from the air. Please follow the following steps:
(1) When disassembling refrigeration components from refrigeration equipment, the components should be covered (sealed) as soon as possible to reduce the entry of moisture in the air.
(2) When installing refrigeration components, do not remove (or open) the cover of the components before connecting them. Please connect the refrigeration circuit components as soon as possible to reduce the entry of moisture in the air.
(3) Only specified lubricants stored in sealed containers can be used. After use, please immediately seal the lubricant container. If the lubricant is not properly sealed, it cannot be used again after being penetrated by moisture.
3. Do not use spoiled and turbid refrigerant oil, as it will affect the normal operation of the compressor.
4. The system should supplement the refrigerant oil according to the prescribed dosage. If the refrigerant oil is too low, it will affect the lubrication of the compressor. Adding too much refrigerant oil will also affect the cooling capacity of the air conditioning system.
5. When adding refrigerant, refrigerant oil should be added first, and then refrigerant should be added
Post time: Oct-23-2023