Classification of refrigerant oil
One is traditional mineral oil;
The other is synthetic polyethylene glycol esters such as PO,Polyester oil is also synthetic polyethylene glycol lubricating oil.POE oil can be used not only in HFC refrigerant system, but also in hydrocarbon refrigerant.PAG oil can be used in HFC, hydrocarbon and ammonia systems as refrigerants.
The main function of refrigerating oil
·Reduce friction work, friction heat and wear
·Fill the sealing area with oil to ensure the sealing performance and prevent the leakage of refrigerant
·The movement of oil takes away the abrasive particles produced by metal friction, thus cleaning the friction surface
·Provide hydraulic power for unloading mechanism
Performance requirements for refrigerating oil
·Suitable viscosity: the viscosity of refrigerating machine oil not only ensures that the friction surface of each moving part has good lubricity, but also takes away some heat from the refrigerating machine and plays a sealing role.If the refrigerant used by the refrigerating machine is of greater solubility to the oil of the refrigerating machine, the oil with higher viscosity should be considered to overcome the influence of the oil diluted by the refrigerant
·Small volatile, high flash point: freezing oil volatilization amount is larger, with the refrigerant cycle, oil amount is, the more so the refrigeration oil fractions a very narrow range of flash point should also be higher than machine exhaust temperature above 25 ~ 30 ℃.
·Good chemical stability and thermal oxidation stability: in the final compression refrigerating machine working temperature is 130 ℃ ~ 160 ℃, the temperature of frozen oil heats and decomposition of constantly metamorphism, generate carbon deposit in refrigerating machine malfunction and wear.Moreover, the decomposition products of oil will react with the refrigerant, which will make the cooling effect worse, and the resulting acid will strongly corrode the parts of the refrigerator.
·No water and impurities: because water freezes in the evaporator will affect the heating efficiency, contact with the refrigerant will accelerate the decomposition of the refrigerant and corrode the equipment, so the refrigerant oil cannot contain water and impurities.
·Others:The refrigerating oil should also have good anti-foaming property and not dissolve or expand to rubber, enameled wire and other materials.Good electrical insulation should be used in enclosed refrigerating machine.
Factors to consider in choosing refrigerating oil
·Viscosity: the higher the speed of the compressor, the higher the viscosity of the refrigerating oil should be.
·Thermal stability:The thermal stability is generally measured by the flash point of the frozen-engine oil.Flash point refers to the temperature at which the steam of refrigerating machine oil flashes after it is heated.Refrigerator oil flash point must be higher than that of compressor exhaust temperature, such as R717, R22 compressor using refrigerator oil flash point should be above 160 ℃.
·Fluidity: the refrigerating machine oil should have good fluidity at low temperature. In the evaporator, due to low temperature and increased viscosity of oil, the fluidity will be poor. When the refrigerating machine oil reaches a certain temperature, it will stop flowing.The freezing point of refrigerating machine oil is required to be low, especially the freezing point of oil of cryogenic machine is very important.
·Solubility: the solubility of various refrigerants and refrigerant oil is different, which can be roughly divided into three categories: one is insoluble, the other is insoluble, and the other is between the above two.
·Turbidity point: the temperature at which the refrigerant oil begins to precipitate paraffin (oil becomes turbid) is called turbidity point. When refrigerant exists, the turbidity point of the refrigerant oil will decrease.
The main cause of deterioration of refrigerating oil
·Mixing water: because of the infiltration of air into the refrigeration system, the water in the air is mixed with the refrigerating machine oil after contact.Water content in refrigerant is high, also can mix water into refrigerant oil.When water is mixed into the refrigerating oil, the viscosity decreases and the metal is corroded.In freon refrigeration system, “ice plug” is also caused.
·Oxidation: when the refrigerating oil is in use, when the exhaust temperature of the compressor is high, it may cause oxidative deterioration, especially the refrigerating oil with poor chemical stability, which is more prone to deterioration. Over a period of time, residues will be formed in the refrigerating oil, causing the lubrication of bearings and other places to deteriorate.The mixing of organic fillers and mechanical impurities into the refrigerating machine oil will also accelerate its aging or oxidation.
·Mixing of refrigerating machine oil: when several different types of refrigerating machine oil are used together, the viscosity of refrigerating machine oil will be reduced, and even the formation of oil film will be damaged.
If two kinds of refrigerating machine oil contain different anti-oxidation additives of different properties, when mixed together, chemical changes may occur and precipitates will be formed, which will affect the lubrication of compressor. Therefore, attention should be paid to when using.
·There are impurities in the refrigerating oil
How to choose refrigerating oil
·Select lubricating oil according to the compression type: the compressor of the refrigerating machine has three types of piston, screw and centrifugal. The first two types of lubricating oil are in direct contact with the compressed refrigerant, considering the interaction between lubricating oil and refrigerant.Centrifugal oil is only used to lubricate the rotor bearing. It can also be selected according to the load and speed.
·Select lubricating oil according to the type of refrigerant: the lubricating oil in direct contact with the refrigerant should consider the interaction between the two.For example, a refrigerant such as freon can dissolve in mineral oil, so the viscosity grade of the selected lubricating oil should be one grade higher than that of the insoluble refrigerant, so as to prevent the lubricating oil from being unable to be guaranteed after being diluted.In addition, it should be noted that a small amount of lubricating oil mixed with refrigerant will affect the work of the refrigeration system.The flocculation point of refrigerating machine oil is the quality index to check whether the lubricating oil mixed with refrigerant can precipitate wax crystal and block the refrigeration system.
·Select lubricating oil according to the evaporation temperature of refrigerant: generally speaking, refrigerant evaporator with low evaporation temperature should choose the refrigerant oil with low freezing point, so as to avoid the lubricating oil carried by refrigerant to the refrigeration system from condensing on the throttle valve and evaporator, affecting the refrigeration efficiency.
The freezing point of the lubricating oil used in an ammonia refrigerant cooler should be lower than the evaporation temperature.
Where freon is used as a refrigerant, the freezing point of the lubricating oil may be slightly higher than the evaporation temperature.
·Select lubricating oil according to working conditions of the freezer.
HERO-TECH only use high-class refrigerator oil. All the parts of our chillers are of high quality , the same goes for refrigerated oil. We need good refrigeration oil to support the stable and long running of the machine.
So, trust HERO-TECH, trust your refrigerantion service specialist .
Post time: Dec-14-2018
