The refrigeration system is a general term for the equipment and pipelines through which the refrigerant flows, including compressors, condensers, throttling devices, evaporators, pipelines and auxiliary equipment. It is the main component system of air conditioning equipment, cooling and refrigeration equipment.
There are various forms of blockage faults in the refrigeration system, such as ice blockage, dirty blockage, and oil blockage. On the bypass charging valve, the indication is negative pressure, the sound of the outdoor unit running is light, and there is no sound of liquid flowing in the evaporator.
Causes and symptoms of ice blockage
Ice blockage faults are mainly caused by excessive moisture in the refrigeration system. With the continuous circulation of the refrigerant, the moisture in the refrigeration system gradually concentrates at the outlet of the capillary. Because the temperature at the outlet of the capillary is the lowest, the water freezes and gradually Increase, to a certain extent, the capillary will be completely blocked, the refrigerant cannot circulate, and the refrigerator will not cool.
The main source of moisture in the refrigeration system is: the motor insulation paper in the compressor contains moisture, which is the main source of moisture in the system. In addition, the components and connecting pipes of the refrigeration system have residual moisture due to insufficient drying; the refrigerator oil and refrigerant contain moisture exceeding the allowable amount; Absorbed by motor insulation paper and refrigeration oil. Due to the above reasons, the water content in the refrigeration system exceeds the allowable amount of the refrigeration system, and ice blockage occurs. On the one hand, ice blockage will cause the refrigerant to fail to circulate, and the refrigerator will not be able to cool normally; on the other hand, the water will chemically react with the refrigerant to generate hydrochloric acid and hydrogen fluoride, which will cause corrosion of metal pipes and components, and even cause damage to the motor windings. The insulation is damaged, and at the same time, it will cause the refrigeration oil to deteriorate and affect the lubrication of the compressor. Moisture in the system must therefore be kept to a minimum.
The symptoms of ice blockage in the refrigeration system are that it works normally in the initial stage, frost is formed in the evaporator, the condenser dissipates heat, the unit runs smoothly, and the sound of refrigerant activity in the evaporator is clear and stable. With the formation of ice blockage, the airflow can be heard gradually weakening and intermittent. When the blockage is severe, the sound of airflow disappears, the refrigerant cycle is interrupted, and the condenser gradually cools down. Due to blockage, the exhaust pressure rises, the sound of the machine increases, there is no refrigerant flowing into the evaporator, the frosting area gradually decreases, and the temperature gradually rises. At the same time, the capillary temperature also rises together, so the ice cubes begin to melt. The refrigerant starts to circulate again. After a period of time, the ice blockage will reoccur, forming a periodic pass-block phenomenon.
Causes and symptoms of dirty blockage
Dirty blockage faults are caused by excessive impurities in the refrigeration system. The main sources of impurities in the system are: dust and metal shavings during the manufacture of refrigerators, the oxide layer on the inner wall of the pipes during welding, the inner and outer surfaces of the parts are not cleaned during the processing, and the pipes are not tightly sealed. In the pipe, there are impurities in the refrigerating machine oil and refrigerant, and the desiccant powder with poor quality in the drying filter. Most of these impurities and powders are removed by the drier filter when they flow through the drier filter, and when the drier filter has more impurities, some fine dirt and impurities are brought into the capillary tube by the refrigerant with a higher flow rate. The parts with higher resistance accumulate and accumulate, and the resistance increases, making it easier for impurities to stay until the capillary is blocked and the refrigeration system cannot circulate. In addition, if the distance between the capillary and the filter screen in the dry filter is too close, it is easy to cause dirty blockage; in addition, when welding the capillary and the dry filter, it is also easy to weld the capillary nozzle.
After the refrigeration system is dirty and blocked, because the refrigerant cannot circulate, the compressor runs continuously, the evaporator is not cold, the condenser is not hot, the shell of the compressor is not hot, and there is no sound of air flow in the evaporator. If it is partially blocked, the evaporator will have a cool or icy feeling, but no frost. When you touch the outer surface of the dry filter and capillary, it feels very cold, there is frost, and even a layer of white frost will form. This is because when the refrigerant flows through the micro-blocked dry filter or capillary tube, it will cause throttling and pressure reduction, so that the refrigerant flowing through the blockage will expand, vaporize, and absorb heat, resulting in condensation or condensation on the outer surface of the blockage. Frost.
The difference between ice blockage and dirty blockage: after a period of time, the ice blockage can resume cooling, forming a periodical repetition of opening for a while, blocking for a while, opening again after being blocked, and blocking again after opening. After the dirty block occurs, it cannot be refrigerated.
In addition to dirty capillaries, if there are many impurities in the system, the dry filter will gradually be blocked. Because the capacity of the filter itself to remove dirt and impurities is limited, it will be blocked due to the continuous accumulation of impurities.
Oil plugging failure and other pipeline blockage failures
The main reason for oil plugging in the refrigeration system is that the compressor cylinder is severely worn or the gap between the piston and the cylinder is too large.
The gasoline discharged from the compressor is discharged into the condenser, and then enters the dry filter together with the refrigerant. Due to the high viscosity of the oil, it is blocked by the desiccant in the filter. When there is too much oil, it will form a blockage at the inlet of the filter, causing The refrigerant cannot circulate normally, and the refrigerator does not cool.
The reason for the blockage of other pipelines is: when the pipeline is welded, it is blocked by solder; or when the tube is replaced, the replaced tube itself is blocked and has not been found. The above blockages are caused by human factors, so it is required to weld and replace the tube , should be operated and inspected according to the requirements, it will not cause artificial blockage failure.
The method of removing the blockage of the refrigeration system
1 Troubleshooting of ice blockage
Ice blockage in the refrigeration system is due to excessive moisture in the system, so the entire refrigeration system must be dried. There are two ways to deal with it:
1. Use a drying oven to heat and dry each component. Remove the compressor, condenser, evaporator, capillary, and air return pipe in the refrigerant system from the refrigerator, and put them in the drying oven to heat and dry. The temperature in the box is At about 120°C, the drying time is 4 hours. After natural cooling, blow and dry with nitrogen one by one. Replace with a new dry filter, and then proceed to assembly and welding, pressure leak detection, vacuuming, refrigerant filling, trial operation and sealing. This method is the best way to troubleshoot ice blockage, but it is only applicable to the warranty department of the refrigerator manufacturer. General repair departments can use methods such as heating and evacuation to eliminate ice blockage faults.
2. Use heating and vacuuming and secondary vacuuming to remove moisture from the components of the refrigeration system.
2 Elimination of dirty blockage faults
There are two ways to troubleshoot capillary dirty blockage: one is to use high-pressure nitrogen combined with other methods to blow out the blocked capillary. exclude. If the capillary is seriously blocked and the above method cannot eliminate the fault, replace the capillary to eliminate the fault, as follows:
1. Use high-pressure nitrogen to blow out the dirt in the capillary: cut the process pipe to drain the liquid, weld the capillary from the dry filter, connect the three-way repair valve to the process pipe of the compressor, and fill it with a high pressure of 0.6-0.8MPa Nitrogen, and straighten the capillary, heat it with a gas welding carbonization flame, carbonize the dirt in the tube, and blow out the dirt in the capillary under the action of high-pressure nitrogen. After the capillary is unimpeded, add 100 ml of carbon tetrachloride for gas cleaning. The condenser can be cleaned with carbon tetrachloride on the pipe cleaning device. Then replace the drier filter, then fill with nitrogen to detect leaks, vacuumize, and finally fill with refrigerant.
2. Replace the capillary: If the dirt in the capillary cannot be flushed out by the above method, you can replace the capillary together with the low-pressure tube. First remove the low-pressure tube and capillary from the copper-aluminum joint of the evaporator by gas welding. During disassembly and welding, the copper-aluminum joint should be wrapped with wet cotton yarn to prevent the aluminum tube from being burned out at high temperature.
When replacing the capillary tube, the flow rate should be measured. The outlet of the capillary tube should not be welded to the inlet of the evaporator. Install a trim valve and a pressure gauge at the inlet and outlet of the compressor. When the external atmospheric pressure is equal, the indication pressure of the high pressure gauge should be stable at 1~1.2MPa. If the pressure exceeds, it means that the flow rate is too small, and a section of capillary can be cut off until the pressure is suitable. If the pressure is too low, it means that the flow rate is too large. You can coil the capillary several times to increase the resistance of the capillary, or replace a capillary. After the pressure is suitable, weld the capillary to the inlet pipe of the evaporator.
When welding a new capillary, the length inserted into the copper-aluminum joint should be about 4 to 5 cm to avoid welding blockage. When the capillary is welded to the dry filter, the insertion length should be 2.5cm. If the capillary is inserted too much into the dry filter and is too close to the filter screen, tiny molecular sieve particles will enter the capillary and block it. If the capillary is inserted too little, impurities and molecular sieve particles during welding will enter the capillary and directly block the capillary channel. Therefore the capillaries are inserted into the filter neither too much nor too little. Too much or too little creates a clogging hazard. Figure 6-11 shows the connection position of capillary and filter drier.
3 Troubleshooting of oil plugging
An oil plugging failure indicates that there is too much refrigerating machine oil remaining in the refrigerating system, which affects the cooling effect or even fails to refrigerate. Therefore, the refrigerating machine oil in the system must be cleaned.
When the filter oil is blocked, a new filter should be replaced, and at the same time, use high-pressure nitrogen to blow out part of the refrigerating machine oil accumulated in the condenser, and use a hair dryer to heat the condenser when nitrogen is introduced.
Post time: Mar-06-2023
