Key Notes on Refrigeration Oil Selection for Reciprocating Refrigeration Compressors

When selecting refrigeration oil for reciprocating piston refrigeration compressors, the type of refrigerant must be the primary basis for matching the oil type. For R22 refrigeration systems, 3GS or 4GS mineral refrigeration oils are recommended. However, for environmentally friendly refrigerant systems such as R134a, R404A, R407C, and R410A, POE synthetic oil must be used; mixing mineral oil and synthetic oil is strictly prohibited to prevent oil stratification and lubrication failure. The viscosity grade should be selected reasonably based on operating conditions. VG32 and VG46 viscosity grades are suitable for conventional operating conditions. Low pour point oils should be chosen for low-temperature units to avoid wax precipitation and reduced fluidity at low temperatures, while higher viscosity oils are required for high-temperature conditions to ensure oil film stability. Strict control of the oil's physicochemical indicators is also necessary, with requirements that acid value does not exceed 0.04 mgKOH/g, pour point is no higher than -50°C, and flash point meets standards, to prevent corrosion of components and high-temperature carbonization. Due to the reciprocating motion driven by the crankshaft connecting rod mechanism in reciprocating compressors, the lubrication and sealing properties of the refrigeration oil are highly demanding. The oil must meet the lubrication and sealing needs of friction pairs such as piston rings, cylinder walls, valve plates, and bearings, thereby reducing mechanical wear and internal leakage. In practical applications, the original equipment manufacturer's selection specifications should be followed, with a preference for brand-specific refrigeration oils. Regular oil quality testing and timely replacement according to operating hours should be conducted to ensure long-term stable and reliable operation of the compressor.