Reciprocating refrigeration compressor HFC refrigerant system compatibility and oil return matching rules

Reciprocating refrigeration compressor HFC refrigerant system compatibility and oil return matching rules

HFC refrigerants such as R404A, R134a and R410A are widely used in process refrigeration; HFCs are miscible with synthetic polyol ester lubricant and require strict oil return design. HFC refrigerant dissolves into POE oil heavily at low temperature; more than 15% refrigerant dissolved in oil will reduce lubricant viscosity by half and weaken bearing protection. Xiteliduo reciprocating compressor for HFC systems is filled with POE synthetic lubricant from factory; mineral oil cannot be mixed into the circuit, otherwise sludge will form rapidly. Small 4-cyl reciprocating refrigeration compressor HFC suction pipe must maintain minimum gas velocity of 3.5 m/s to carry oil back to compressor crankcase under partial load. Medium 4-cyl reciprocating refrigeration compressor HFC system liquid receiver must reserve proper oil storage space; oil accumulating in receiver will break normal oil circulation balance. Large 4-cyl reciprocating refrigeration compressor HFC system needs oil separator with high separation efficiency; recommended oil separation efficiency is not lower than 99.5%. Large 6-cyl reciprocating refrigeration compressor HFC system long pipeline layout needs periodic oil return operation under low load, to prevent oil trapping in low pipeline sections. Many field engineers mix mineral oil and POE oil during oil refill. Oil mixing will generate sludge, and the probability of oil circuit blockage increases by 71%. Single-unit two-stage refrigeration compressor HFC low-stage circuit has lower temperature; refrigerant-oil miscibility becomes stronger and oil viscosity reduction effect is more obvious. Cascade unit high-stage reciprocating refrigeration compressor can adopt HFC working medium; low-stage usually uses ultra-low temperature refrigerant and separate lubricant system.

FAQ

Q1: What type of lubricant is required for HFC refrigerant reciprocating compressor system? A1: Synthetic polyol ester (POE) lubricant must be used. Q2: What will happen when over 15% HFC refrigerant dissolves into POE oil? A2: Lubricant viscosity drops by half and bearing protection capability decreases. Q3: What suction gas velocity is required for small 4-cyl HFC reciprocating compressor to guarantee oil return? A3: Minimum suction gas velocity of 3.5 m/s. Q4: What oil separation efficiency standard is recommended for large 4-cyl HFC reciprocating compressor oil separator? A4: Oil separation efficiency shall reach at least 99.5%. Q5: What fault will be caused by mixing mineral oil and POE oil in HFC refrigeration system? A5: Sludge forms and oil circuit blockage probability rises by 71%. Q6: Why is oil viscosity reduction more serious on HFC single-unit two-stage compressor low-stage side? A6: Low temperature enhances miscibility between HFC refrigerant and POE oil. Q7: Can HFC refrigerant be used on cascade unit reciprocating compressor? A7: HFC can be used for high-stage reciprocating compressor; low-stage uses separate ultra-low temperature refrigerant and oil.