Common faults and troubleshooting methods for refrigeration compressors

The compressor is the heart of the refrigeration system. It draws in low-temperature, low-pressure refrigerant gas from the suction pipe, compresses it using a motor-driven piston, and discharges high-temperature, high-pressure refrigerant liquid into the discharge pipe. This provides the power for the refrigeration cycle, achieving the refrigeration cycle of compression-condensation-expansion-evaporation (heat absorption).
Now let's look at common compressor faults and troubleshooting methods:
I. Compressor suddenly stops during operation:
1. Reasons for the compressor to suddenly stop during operation:
(1) Suction pressure is too low, below the low-pressure limit of the pressure relay;
(2) Discharge pressure is too high, causing the high-pressure relay to trip and cut off power;
(3) Oil pressure is too low, the oil pressure relay trips;
(4) Motor overload, thermal relay trips;
2. Troubleshooting methods for compressor suddenly stopping during operation:
(1) Check the cause; if it's a pipe blockage, clear the pipe; if the system is short of refrigerant, supplement it;
(2) Check the cooling capacity or cooling airflow of the condenser;
(3) Check the oil supply system piping and oil pump;
(4) Check if the supply voltage is too low or the cooling load is too high;
II. Excessive discharge pressure
1. Reasons for excessive discharge pressure:
(1) Insufficient cooling water for water-cooled condensers or insufficient cooling airflow for air-cooled condensers;
(2) Excessive scale or oil fouling on the condenser tube bundle surface, making heat dissipation difficult;
(3) Air in the refrigeration system;
(4) Excessive refrigerant charge;
(5) Valve failure in the discharge pipe, causing excessive pressure;
2. Troubleshooting methods for excessive discharge pressure:
(1) Check if the valve is fully open, increase water supply, or check the motor voltage, speed, and whether the drive belt is too loose;
(2) Clean scale and wash off oil to keep the condenser tube bundle surface clean;
(3) Bleed air;
(4) Discharge excess refrigerant;
(5) Check and correct valve;
III. Compressor wet compression
1. Reasons for compressor wet compression:
(1) Thermostatic expansion valve malfunction, opening too large;
(2) Solenoid valve malfunction, a large amount of refrigerant enters the evaporator tube after shutdown, and enters the compressor when it restarts;
(3) Excessive refrigerant charge in the system;
(4) The temperature sensor of the thermostatic expansion valve is loose and not tied, causing the thermostatic expansion valve to open wider;
2. Troubleshooting methods for compressor wet compression:
(1) Close the liquid supply valve and repair the thermostatic expansion valve;
(2) Repair the solenoid valve;
(3) Discharge excess refrigerant;
(4) Check the binding condition of the temperature sensor;
IV. Compressor seizure
1. Reasons for compressor seizure:
(1) Dirt and impurities in the lubricating oil;
(2) Oil pump pipe blockage, causing the cylinder to lack oil and the piston to seize;
(3) The main gear of the oil pump inserted into the crank pin is broken, causing the oil system to be out of oil;
2. Troubleshooting methods for compressor seizure:
(1) Replace with new lubricating oil;
(2) Repair the oil pump pipeline;
(3) Repair or replace the oil pump main gear shaft;
V. Abnormal noise in the cylinder
1. Reasons for abnormal noise in the cylinder:
(1) Too small dead space in the cylinder;
(2) Excessive clearance between the piston pin and connecting rod bushings;
(3) Valve plate breakage;
(4) Oil splashing sound from the crankshaft crank or connecting rod big end;
2. Abnormal noise in the cylinder
(1) Adjust and thicken the cylinder gasket;
(2) Replace the piston pin or bushing;
(3) Stop immediately and replace the valve plate;
(4) No need to stop the machine for a short time, but stop and check after several minutes;
VI. Noise in the crankcase
1. Reasons for noise in the crankcase:
(1) Connecting rod nut loose;
(2) Excessive clearance between connecting rod big end bearing;
2. Troubleshooting methods for noise in the crankcase:
(1) Stop the machine and retighten;
(2) Replace the tiles;
VII. Compressor fails to start
1. Reasons for compressor failure to start:
(1) Power failure, poor contact of fuse, or fuse blown;
(2) Poor contact of the starter's contact points;
(3) Temperature controller malfunction or failure;
(4) Improper setting of the pressure relay;
2. Troubleshooting methods for compressor failure to start:
(1) Check power supply and fuses;
(2) Check the starter and clean the contact points with gauze;
(3) Check the temperature indicator position and inspect each component;
(4) Check the pressure relay components or setpoints;
VIII. Insufficient compressor cooling capacity
1. Reasons for insufficient compressor cooling capacity:
(1) Piston ring wear or excessive clearance between piston and cylinder due to wear;
2. Troubleshooting methods for insufficient compressor cooling capacity:
(1) Replace with new piston rings or repair/replace components;
IX. Noise from the compressor and motor coupling
1. Reasons for noise from the compressor and motor coupling:
(1) Improper fit of the compressor and motor coupling;
(2) Improper fit of the coupling key and keyway;
(3) Loose or damaged elastic ring of the coupling;
(4) Belt too loose;
(5) Loose fit between the coupling bore and shaft;
2. Troubleshooting methods for noise from the compressor and motor coupling
(1) Reassemble according to correct assembly requirements;
(2) Adjust the fit of the key and keyway, replace the key;
(3) Tighten the elastic ring or replace it;
(4) Adjust the belt tension;
(5) Adjust and tighten the coupling.