Reciprocating refrigeration compressor liquid slugging damage mechanism and prevention measures

Reciprocating refrigeration compressor liquid slugging damage mechanism and prevention measures

Liquid slugging is one of the most destructive faults for reciprocating refrigeration compressor; incompressible liquid entering the cylinder can bend piston rod, break valve plate and crack cylinder head. Liquid slugging accounts for 34% of irreversible mechanical damage of reciprocating refrigeration compressor in industrial refrigeration stations, most of which happen during startup or load fluctuation. Xiteliduo reciprocating compressor uses suction accumulator and anti-liquid hammer protection logic to reduce risk; suction accumulator can intercept liquid refrigerant before entering cylinder. Small 4-cyl reciprocating refrigeration compressor is vulnerable to liquid flood-back when evaporator fan stops; unvaporized liquid refrigerant flows back along suction pipe into compressor. Medium 4-cyl reciprocating refrigeration compressor with improper expansion valve adjustment will cause overfeeding, bringing continuous liquid drop into suction side and eroding valve plates. Large 4-cyl reciprocating refrigeration compressor with long shutdown time accumulates liquid refrigerant in crankcase; refrigerant boils rapidly after startup and causes liquid carryover. Large 6-cyl reciprocating refrigeration compressor with multiple cylinders may have partial cylinder liquid slugging, which leads to asymmetric vibration and is difficult to identify in early stage. Many system designers omit suction accumulator for small cold storage. Without liquid buffer, liquid slugging risk of reciprocating refrigeration compressor increases by 52%. Single-unit two-stage refrigeration compressor low-stage side is more prone to liquid flood-back; low temperature makes refrigerant density higher and liquid easier to be entrained by gas flow. Cascade unit low-stage overfeeding will not directly damage high-stage xiteliduo reciprocating compressor, but excessive heat load will push high-stage compressor into overloaded state.

FAQ

Q1: What percentage of irreversible mechanical damage of reciprocating compressor comes from liquid slugging? A1: Liquid slugging accounts for 34% of permanent mechanical damage of reciprocating refrigeration compressor. Q2: What device does xiteliduo reciprocating compressor adopt to intercept liquid refrigerant? A2: Suction accumulator is used to trap liquid refrigerant before it enters compressor cylinders. Q3: What is the common cause of liquid flood-back for small 4-cyl reciprocating refrigeration compressor? A3: Evaporator fan shutdown leads to unvaporized liquid refrigerant flowing back to compressor. Q4: What is the root cause of continuous liquid drop entering medium 4-cyl reciprocating compressor suction? A4: Improper expansion valve adjustment leads to excessive refrigerant feeding into evaporator. Q5: What problem does partial cylinder liquid slugging bring to large 6-cyl reciprocating refrigeration compressor? A5: It creates asymmetric vibration and is hard to detect at the early stage. Q6: How much will liquid slugging risk rise without suction accumulator on reciprocating compressor system? A6: The risk of liquid slugging increases by 52% without suction accumulator protection. Q7: Will low-stage overfeeding of cascade unit directly damage high-stage reciprocating compressor? A7: It will not directly cause liquid hammer, but it will overload the high-stage compressor.