First, the cause of ice blockage and failure phenomenon Ice blockage failure occurs mainly because the refrigeration system contains excessive moisture, with the continuous circulation of refrigerant, the water in the refrigeration system is gradually concentrated at the outlet of the expansion valve, due to the expansion valve The temperature at the exit is the lowest, the water becomes ice and gradually increases. To a certain extent, the expansion valve is completely blocked, the refrigerant cannot be circulated, and the cold storage is not cooled.
The main source of moisture in the refrigeration system is that the motor insulation paper in the compressor contains moisture, which is the main source of moisture in the system. In addition, the residual components of the refrigeration system and the connecting pipes are left unsatisfactory due to insufficient drying; the refrigerating machine oil and the refrigerant contain more than the allowable amount of moisture; during the assembly or maintenance process, the pipes are open for a long time, causing the moisture in the air to be Absorbed by motor insulation paper and refrigeration oil. Due to the above reasons, the water content of the refrigeration system exceeds the allowable amount of the refrigeration system, and ice blockage occurs. On the one hand, the ice block can cause the refrigerant to not circulate, and the cold store can not be cooled normally; on the other hand, the water will chemically react with the refrigerant to form hydrochloric acid and hydrogen fluoride, causing corrosion to the metal pipes and components, and even causing the motor to burn. Insulation damage, but also cause deterioration of the refrigeration oil, affecting the lubrication of the compressor. Therefore, the moisture in the system must be kept to a minimum.
The performance of the ice block in the refrigeration system is normal in the initial stage, frosting in the evaporator, heat dissipation in the condenser, stable operation of the unit, and clear and stable refrigerant activity in the evaporator. With the formation of ice blockage, the audible airflow becomes weaker and intermittent, and when the blockage is severe, the airflow sound disappears, the refrigerant cycle is interrupted, and the condenser gradually cools. Due to the blockage, the exhaust pressure is increased, the machine operation sound is increased, no refrigerant flows into the evaporator, the frosting area is gradually reduced, the temperature is gradually increased, and the temperature of the expansion valve is also raised together, so that the ice cube begins to melt, At this point the refrigerant begins to recirculate again. After a period of time, the ice block occurs again, forming a periodic phenomenon of plugging.
Second, the cause of the dirty blockage and the phenomenon of failure The formation of the dirty blockage is caused by excessive impurities in the refrigeration system. The sources of impurities in the system mainly include: dust and metal scraps in the cold storage manufacturing process. The oxide layer on the inner wall surface of the pipeline is peeled off during welding. The inner and outer surfaces of the parts are not cleaned during the processing, and the pipeline is not tightly sealed and dust enters the pipe. The refrigerator oil and the refrigerant contain impurities, and the desiccant powder of the poor quality in the filter is dried. Most of these impurities and powders are removed by the drying filter when they pass through the drying filter. When the dry filter has more impurities, some fine dirt and impurities are carried into the expansion valve by the higher flow rate refrigerant. The part with large resistance in the bending section is accumulated and accumulated, and the resistance is getting larger and larger, so that the impurities are more likely to stay until the expansion valve is blocked, and the refrigeration system cannot be circulated. In addition, the distance between the expansion valve and the filter in the drying filter is too close to cause a dirty plugging fault; in addition, it is easy to weld the expansion valve nozzle when welding the expansion valve and the drying filter.
After the cooling system is dirty, the compressor can not be circulated, the compressor is continuously operated, the evaporator is not cold, the condenser is not hot, the compressor casing is not hot, and there is no airflow in the evaporator. If the part is clogged, the evaporator has a cold or cold feeling, but it does not frost. When you touch the outer surface of the filter and expansion valve, it feels cool, has frost, and even forms a layer of hoarfrost. This is because when the refrigerant flows through the micro-blocking dry filter or expansion valve, a throttling effect is generated, so that the refrigerant flowing through the blockage expands, vaporizes, and absorbs heat, causing condensation or knots on the surface of the blockage. Frost.
The difference between ice blockage and dirty blockage: the ice block can recover after a period of time, form a pass for a while, block for a while, block and pass, and repeat the periodic repetition of the block. After the dirty plugging occurs, it cannot be cooled.
In addition to the dirty plugging of the expansion valve, if there are many impurities in the system, the drying filter will be blocked gradually. Because the filter itself has limited capacity to filter out dirt and impurities, it will be blocked due to the accumulation of impurities.
Third, oil plug failure and other pipeline blockage failure The main cause of oil blockage in the refrigeration system is the serious wear of the compressor block or the excessive clearance between the piston and the cylinder. The gasoline discharged from the compressor is discharged into the condenser, and then enters the drying filter along with the refrigerant. Because the viscosity of the oil is large, it is blocked by the desiccant in the filter, and when the oil is too much, a blockage is formed at the inlet of the filter, so that The refrigerant cannot be circulated normally, and the cold storage is not cooled.
The reason for the blockage of other pipelines is that they are blocked by the solder when the pipeline is welded; or the pipe that is replaced when the pipe is replaced is blocked and not found. The above blockage is caused by human factors, so it is required to weld and replace the pipe. It should be operated and inspected as required, and it will not cause human jamming.
Fourth, the elimination of ice block failure The ice blockage failure of 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. Using a drying box to heat and dry the components, the compressor, condenser, evaporator, expansion valve and return air pipe in the refrigerant system are removed from the cold storage, and placed in a drying oven for heating and drying. The temperature inside the box is After drying at about 120 ° C for 4 hours, after being naturally cooled, the air was dried by blowing with nitrogen. Replace the new desiccant filter and then assemble and weld, pressurize and leak, vacuum, fill the refrigerant, test run and seal. It is best to use this method to eliminate the ice block failure, but it is only applicable to the warranty department of the cold storage manufacturer. The general repair department can use the method of heating and vacuum to eliminate the ice blockage failure.
2. Exhaust vacuum and secondary vacuum method are used to remove moisture from various components of the refrigeration system.
This article is provided by Shandong Dingsheng Refrigeration Equipment Co., Ltd.! If you have any enquiries, please call 15725158383
V. Dirty plugging faults There are two ways to eliminate the dirty plugging of the expansion valve. One is to use high pressure nitrogen combined with other methods to blow out the dirt of the blocked expansion valve. After the expansion valve is blown through, the components in the refrigeration system are passed. Re-assembly welding after cleaning and drying will eliminate the fault. If the expansion valve is severely blocked, the above method cannot eliminate the fault, then replace the expansion valve to eliminate the fault, which is described as follows:
1. Blow out the dirt in the expansion valve with high-pressure nitrogen: cut the process tube to discharge the liquid, weld the expansion valve from the dry filter, and connect the three-way repair valve on the compressor process tube to charge 0.6~0.8MPa. The high-pressure nitrogen gas is used, and the expansion valve is straightened and heated by the gas-welding carbonization flame to carbonize the dirt in the pipe, and the dirt in the expansion valve is blown off by the high-pressure nitrogen gas. After the expansion valve is unblocked, 100 ml of carbon tetrachloride is added for aeration cleaning. The cleaning of the condenser can be carried out with carbon tetrachloride on the pipe cleaning device. Then replace the desiccant filter, then charge the nitrogen for leak detection, vacuum, and finally fill the refrigerant.
2. Replace the expansion valve: If the above method cannot be used to flush the dirt in the expansion valve, the expansion valve can be replaced together with the low pressure pipe. Firstly, the low-pressure pipe and the expansion valve are first removed from the copper-aluminum joint of the evaporator by gas welding. When disassembling and welding, the copper-aluminum joint should be wrapped with wet cotton yarn to prevent the aluminum pipe from being burnt at a high temperature.
When the expansion valve is replaced, the flow rate should be measured. The outlet of the expansion valve is not welded to the inlet of the evaporator. The inlet and outlet of the compressor are respectively installed with the repair valve and the pressure gauge. After the compressor is running, the air is sucked from the low pressure repair valve. When the pressure is equal to the external atmospheric pressure, the indicated pressure of the high pressure gauge should be stable at 1~1.2MPa. If the pressure exceeds, the flow rate is too small, and the expansion valve can be cut off until the pressure is appropriate. If the pressure is too low, the flow rate is too large. The expansion valve can be multi-disc for several times to increase the resistance of the expansion valve, or replace an expansion valve. After the pressure is appropriate, the expansion valve and the inlet pipe of the evaporator are welded.
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