The main function of Metal Working Fluid
(1) lubricate the friction surface, so that the friction surface is completely separated by oil film, thereby reducing the friction work, friction heat and wear;
(2) the flow of Metal Working Fluid take the friction heat, so that the temperature of the friction parts remain within the allowable range;
(3) in the sealed parts filled with oil to ensure that sealing performance, to prevent the leakage of refrigerant;
(4) the movement of oil take away the friction caused by metal friction, play the role of cleaning friction surface;
(5) to provide hydraulic power to the unloading mechanism.
Performance requirements for Metal Working Fluid
⑴ the appropriate viscosity
The viscosity of the Metal Working Fluid is to ensure that the friction surfaces of the moving parts are lubricated, and that part of the heat is removed from the chiller and that is sealed. If the refrigerant used by the chiller is large for the Metal Working Fluid, consider the use of larger oil to overcome the effect of the lubricant being diluted by the refrigerant.
⑵ lower pour point, flocculation point and R12 insoluble content
As the working temperature range of the refrigerator is large, such as ammonia refrigerant in the compression can be as high as 160 ℃, and expansion and down to -10 ℃. Therefore, the pouring of the Metal Working Fluid is low, typically below the freezing temperature of 10 ° C, and the viscosity of the oil is better. To ensure that the Metal Working Fluid can return to the compressor at low temperatures from the evaporator. Halogenated hydrocarbons R12 refrigerant and Metal Working Fluid mix will produce paraffin and other precipitation, that is, paraffin and petroleum resin in the cloud above the cloud point will be condensed. It will block the cooling system of the regulatory agencies and refrigeration equipment pipeline, affecting the heat exchange equipment, it should be tested Metal Working Fluid R12 insoluble content, the lower the content the better. This method of inspection can check the oil in different melting point of wax and may contain the content of resin substances meet the requirements. Flocculation point is also a test of Metal Working Fluid and refrigerant mixture at a certain temperature precipitation of paraffin may precipitate insoluble polar substances in the use of performance indicators, Metal Working Fluid flocculation point must not be higher than the evaporation temperature of the evaporator.
⑶ volatile small, high flash point
The greater the volatilization of the Metal Working Fluid, the greater the amount of oil that is circulating with the refrigerant, thus requiring that the fraction of the metal working fluid should be narrower and the flash point should be higher than the exhaust temperature of the chiller 25 to 30 ° C The
⑷ good chemical stability and thermal oxidation stability
The final compression temperature in the chiller operation can reach 130 ° C to 160 ° C. At this temperature, the Metal Working Fluid will heat and decompose and degrade continuously to produce coke and cause the refrigerator to malfunction and wear. On the other hand, the decomposition products of the oil react chemically with the refrigerant, deteriorating the cooling effect, and generating the acidic material to strongly corrode the refrigerator components. It is therefore required that Metal Working Fluid has good thermal oxidation stability and does not coke and not carbonized at high temperatures in the outlet valve. It also requires that Metal Working Fluid has good chemical stability and avoids the use of refrigerants such as halogenated hydrocarbons (RCI, RF) Class action to produce acidic corrosive substances.
⑸ does not contain water and impurities
Because the water in the evaporator ice will affect the heating efficiency, contact with the refrigerant will accelerate the decomposition of the refrigerant and corrosion equipment, so Metal Working Fluid can not contain water and impurities.
Metal Working Fluid should also have good anti-foam, rubber, enameled wire and other materials do not dissolve, no expansion. In the use of closed chillers should have good electrical insulation.