Common troubleshooting and maintenance of refrigeration systems in cold storage.

1. Refrigerant leakage: After refrigerant leakage in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and the intermittent "squeaking" airflow sound can be heard at the expansion valve, which is much larger than usual. The evaporator does not have frost or a small amount of floating frost on the corners. If the expansion valve hole is enlarged, the suction pressure still does not change significantly. After shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.
Troubleshooting method: After refrigerant leakage, do not rush to fill the system with refrigerant. Instead, immediately identify the leakage point and repair it before filling the refrigerant. The refrigeration system using an open compressor has multiple joints, sealing surfaces, and potential leakage points. During maintenance, attention must be paid to exploring the areas that are prone to leakage, and based on experience, the main leakage points should be checked for signs of oil leakage, pipeline breakage, and street looseness.
2. Excessive refrigerant filling after maintenance: If the amount of refrigerant filled in the repaired refrigeration system exceeds the capacity of the system, the refrigerant will occupy a certain volume of the condenser, reduce the heat dissipation area, and reduce its refrigeration effect. This will result in suction and exhaust pressures generally higher than normal pressure values, frosting of the evaporator, and slow cooling in the warehouse.
Troubleshooting method: According to the operating procedure, it is necessary to shut down for a few minutes before releasing excess refrigerant at the high-pressure shut-off valve. At this time, residual air in the system can also be released together.
3. There is air in the refrigeration system: Air in the refrigeration system will reduce the refrigeration efficiency, and the prominent phenomenon is that the suction and exhaust pressure will increase (but the exhaust pressure has not exceeded the rated value). The temperature from the compressor outlet to the condenser inlet will significantly increase. Due to the presence of air in the system, the exhaust pressure and temperature will both increase.
Troubleshooting method: After a few minutes of shutdown, air can be continuously released from the high-pressure shut-off valve several times, and some refrigerant can also be filled appropriately according to the actual situation.
4. Low efficiency of compressor: Low efficiency of refrigeration compressor refers to the corresponding decrease in refrigeration capacity caused by a decrease in actual displacement under constant operating conditions. This phenomenon often occurs on compressors that have been used for a long time, with large wear, large clearances between various components, and a decrease in the sealing performance of the air valve, resulting in a decrease in actual displacement.
Exclusion method:
1. Check if the cylinder head paper gasket has been punctured and caused leakage, and replace it if there is any;
2. Check if the high and low pressure exhaust valve plates are not tightly closed, and replace them if there are any;
3. Check the clearance between the piston and cylinder. If the clearance is too large, replace it.
5. Excessive frost accumulation on the surface of the evaporator: The frost layer on the evaporator pipeline accumulates thicker and thicker. When the entire pipeline is wrapped in a transparent ice layer, it will seriously affect heat transfer, causing the temperature inside the warehouse to not drop within the required range.
Troubleshooting method: Stop the machine for defrosting, open the warehouse door to allow air circulation, or use fans or other devices to accelerate circulation and reduce defrosting time. Do not use iron tools, wooden sticks, etc. to strike the frost layer to prevent damage to the evaporator pipeline.
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6. There is refrigerant oil in the evaporator pipeline: During the refrigeration cycle, some refrigerant oil remains in the evaporator pipeline. After a long period of use, when there is a lot of residual oil in the evaporator, it will seriously affect its heat transfer effect and cause poor refrigeration.
Troubleshooting method: Remove the refrigerant oil from the evaporator. Remove the evaporator, blow it clean, and then dry it. It is not easy to disassemble and can be blown out by using a compressor at the inlet of the evaporator.
7. The refrigeration system is not smooth: Due to the cleaning of the refrigeration system, after several times of use, dirt gradually accumulates in the filter, and some mesh holes are blocked, resulting in a decrease in refrigerant flow rate and affecting the refrigeration effect. The filter screen at the expansion valve and compressor suction port in the system also shows slight blockage.
Troubleshooting method: The micro blocking components can be removed, cleaned, dried, and then reinstalled.
8. Refrigerant leakage: The compressor starts easily (when the compressor components are not damaged), the suction pressure is in a vacuum state, the exhaust pressure is very low, the exhaust pipe is cold, and there is no sound of liquid flowing in the evaporator.
Troubleshooting method: Inspect the entire machine, mainly focusing on areas that are prone to leakage. After discovering the leakage area, it can be repaired according to the specific situation, and then vacuum and fill with refrigerant.
9. Freezing blockage of expansion valve hole:
(1) Improper drying treatment of main components in the refrigeration system;
(2) The entire system is not vacuumed thoroughly;
(3) The refrigerant contains excessive moisture.
Troubleshooting method: Insert a filter containing moisture absorbent (silicone, anhydrous calcium chloride) into the refrigeration system, filter out the water in the system, and then remove the filter.
10. Dirty blockage at the expansion valve filter screen: When there is a large amount of coarse powdery dirt in the system, it will block the entire filter screen, making it impossible for refrigerant to pass through, resulting in non cooling.
Troubleshooting method: Remove the filter, clean, dry it, and reinstall it into the system.
11. Filter blockage: The desiccant is used for a long time and becomes a paste that seals the filter or dirt gradually accumulates inside the filter, causing blockage.
Troubleshooting method: Remove the filter, clean and dry it, replace the washed desiccant, and install it into the system.
12. Refrigerant leakage inside the expansion valve temperature sensing package: After the temperature sensing agent inside the expansion valve temperature sensing package leaks, the two forces below the membrane push the membrane upwards, causing the valve hole to close and the refrigerant in the system to not pass through, resulting in non cooling. At this time, the expansion valve does not frost, the low pressure is in vacuum, and there is no sound of airflow inside the evaporator.
Troubleshooting method: Stop the machine and close the shut-off valve. Remove the expansion valve to check if the filter is blocked. If not, use a nozzle to blow the inlet of the expansion valve to see if it is ventilated. It can also be visually inspected or disassembled for inspection, and replaced if damaged.