company news about Troubleshooting methods for refrigeration system blockage

Refrigeration system is a general term for the equipment and pipelines through which refrigerant flows, including compressors, condensers, throttling devices, evaporators, pipelines and ancillary equipment. It is the main system of air conditioning equipment, cooling and refrigeration equipment.
Refrigeration system blockage faults include ice blockage, dirty blockage, oil blockage, etc. The common fault characteristics of blockage are: the condenser is not hot when touched, the evaporator is not cool, and the operating current of the compressor is smaller than normal. Connect the pressure gauge to On the bypass filling valve, the indication is negative pressure, the outdoor unit operates softly, and there is no sound of liquid passing through the evaporator.
Causes and fault phenomena of ice blockage
The occurrence of ice blockage failure is mainly due to the excessive moisture in the refrigeration system. With the continuous circulation of the refrigerant, the moisture in the refrigeration system gradually concentrates at the capillary outlet. Since the temperature at the capillary outlet is the lowest, the water freezes and gradually freezes. Increases to a certain extent, the capillary tube 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 various components and connecting pipes of the refrigeration system have residual moisture due to insufficient drying; the refrigeration oil and refrigerant contain more than the allowable amount of moisture; the pipelines are in a state of development for a long time during the assembly or maintenance process, causing the moisture in the air to be Absorbed by motor insulation paper and refrigeration oil. Due to the above reasons, the water content in the refrigeration system exceeds the allowable capacity of the refrigeration system, resulting in ice blockage. On the one hand, ice blockage causes the refrigerant to be unable to circulate and the refrigerator cannot be cooled normally; on the other hand, water will react chemically with the refrigerant to generate hydrochloric acid and hydrogen fluoride, causing corrosion to metal pipes and components, and even causing damage to motor windings. Insulation damage will also cause the refrigeration oil to deteriorate, affecting the lubrication of the compressor. Therefore, moisture in the system must be controlled to a minimum.
The symptoms of ice blockage in the refrigeration system are that it works normally in the initial stage, frost forms in the evaporator, the condenser dissipates heat, the unit runs smoothly, and the sound of refrigerant movement in the evaporator is clear and stable. As the ice blockage forms, the air flow can be heard to gradually become weaker and intermittent. When the blockage is severe, the air flow sound disappears, the refrigerant cycle is interrupted, and the condenser gradually becomes cooler. Due to the blockage, the exhaust pressure increases, the operating sound of the machine increases, no refrigerant flows into the evaporator, the frost area gradually becomes smaller, and the temperature gradually increases. At the same time, the capillary temperature also increases, so the ice cubes begin to melt. The refrigerant starts to circulate again. After a period of time, ice blockage occurs again, forming a periodic traffic-blocking phenomenon.
Causes and fault phenomena of dirty blockage
Dirty blockage is caused by excessive impurities in the refrigeration system. The main sources of impurities in the system include: dust and metal shavings during the manufacturing process of the refrigerator, the oxide layer on the inner wall surface falling off during pipe welding, the internal and external surfaces of each component being not cleaned during the processing, and the pipeline sealing is not tight enough to allow dust to enter Inside the tube, there are impurities in the refrigeration oil and refrigerant, and low-quality desiccant powder in the drying filter. Most of these impurities and powders are removed by the filter dryer when they flow through the filter dryer. When there are more impurities in the filter dryer, some small dirt and impurities are brought into the capillary tube by the refrigerant with a higher flow rate. Parts with greater resistance accumulate and accumulate, and the resistance becomes larger and larger, making it easier for impurities to remain until the capillary is blocked and the refrigeration system cannot circulate. In addition, too close the distance between the capillary tube and the filter screen in the filter dryer can easily cause clogging. In addition, when welding the capillary tube and the filter dryer, it is also easy to weld and block the capillary tube mouth.
After the refrigeration system is clogged, the refrigerant cannot circulate, causing the compressor to run continuously. The evaporator is not cold, the condenser is not hot, the compressor shell is not hot, and there is no sound of air flow in the evaporator. If it is partially clogged, the evaporator will feel cool or icy, but there will be no frost. When you touch the outer surface of the filter dryer and capillary tube, it will feel cold and frosty, and there may even be a layer of white frost. This is because when the refrigerant flows through a slightly blocked dry filter or capillary tube, it produces a throttling and depressurizing effect, causing the refrigerant flowing through the blockage to expand, vaporize, and absorb heat, causing condensation or condensation on the outer surface of the blockage. Frost.
The difference between ice blockage and dirty blockage: After an ice blockage occurs for a period of time, cooling can be restored, causing a periodic repetition of being unblocked and blocked, blocked and unblocked, and unblocked and blocked again. After a dirty blockage occurs, cooling will no longer be possible.
In addition to the capillary being clogged, if there are too many impurities in the system, the drying filter will gradually be clogged. Since the filter itself has a limited capacity to filter out dirt and impurities, clogging will occur due to the continuous accumulation of impurities.
Oil blockage failure and other pipeline blockage failures
The main reason for oil blockage in the refrigeration system is that the compressor cylinder is severely worn or the matching 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 drying filter along 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 forms a blockage at the filter inlet, causing The refrigerant cannot circulate properly and the refrigerator does not cool.
The reasons for the blockage of other pipelines are: blockage by solder when welding the pipeline; or the replacement pipe itself is blocked without being discovered when the pipe is replaced. The above blockage is caused by human factors, so it is required to perform the welding and replacement of the pipe. , should be operated and inspected as required to avoid artificial blockage failure.
1. Troubleshooting of ice blockage
Ice blockage occurs in the refrigeration system because there is excess moisture in the system, so the entire refrigeration system must be dried. There are two ways to deal with it:
1. Use a drying box to heat and dry each component. Remove the compressor, condenser, evaporator, capillary tube, and return pipe in the refrigerant system from the refrigerator and place them in the drying box for heating and drying. The temperature inside the box is Around 120℃, drying time is 4 hours. After natural cooling, blow dry with nitrogen one by one. Replace the new filter dryer, and then proceed with assembly and welding, pressure leak detection, vacuuming, refrigerant filling, trial operation and sealing. This method has the best effect in troubleshooting ice blockage, but it is only suitable for the warranty department of the refrigerator manufacturer. Generally, repair departments can use methods such as heating and evacuation to eliminate ice blockage problems.
2. Use heating vacuuming and secondary vacuuming to remove moisture from various components of the refrigeration system.
2. Troubleshooting of dirty blockage
There are two ways to troubleshoot a clogged capillary tube: one is to use high-pressure nitrogen combined with other methods to blow out the dirt in the clogged capillary tube. After the capillary tube is blown out, the components in the refrigeration system are cleaned and dried and then reassembled and welded to remove the fault. exclude. If the capillary is seriously clogged and the above method cannot eliminate the fault, replace the capillary to eliminate the fault, as described below:
1. Use high-pressure nitrogen to blow out the dirt in the capillary tube: cut the process tube to drain the liquid, weld the capillary tube from the filter dryer, connect the three-way repair valve to the compressor process tube, and fill it with high pressure of 0.6~0.8MPa. Nitrogen, straighten the capillary and heat it with a gas welding carbonizing flame to 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 unblocked, add 100 ml of carbon tetrachloride for aeration and cleaning. The condenser can be cleaned with carbon tetrachloride on the pipe cleaning device. Then replace the dry filter, then fill with nitrogen, detect leaks, vacuum, and finally fill with refrigerant.
2. Replace the capillary tube: If the dirt in the capillary tube cannot be flushed out by the above method, the capillary tube can be replaced together with the low-pressure tube. First use gas welding to remove the low-pressure tube and capillary tube from the evaporator copper-aluminum joint. During disassembly and welding, the copper-aluminum joint should be wrapped with wet cotton gauze to prevent high temperature from burning out the aluminum tube.
When replacing the capillary tube, the flow rate should be measured. The capillary tube outlet should not be welded to the evaporator inlet first. Repair valves and pressure gauges should be installed at the suction and exhaust inlets and outlets of the compressor. After the compressor is running, air will be sucked in from the low-pressure repair valve until the suction pressure reaches the same level. When the external atmospheric pressure is equal, the indicated 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 the capillary tube can be cut off until the pressure is appropriate. If the pressure is too low, it means the flow rate is too large. You can turn the capillary tube several times to increase the resistance of the capillary tube, or replace a capillary tube. After the pressure is suitable, weld the capillary tube to the inlet pipe of the evaporator.
When welding a new capillary tube, the length inserted into the copper-aluminum joint should be about 4 to 5cm to avoid welding blockage. When welding the capillary tube to the filter dryer, the insertion length should be 2.5cm. If the capillary tube is inserted into the filter dryer too much and is too close to the filter screen, tiny molecular sieve particles will enter the capillary tube 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 should be inserted into the filter neither too much nor too little. Too much or too little creates the risk of clogging. Figure 6-11 shows the connection position between the capillary tube and the filter dryer.
3. Troubleshooting of oil blockage
The occurrence of oil blockage indicates that there is too much refrigeration oil remaining in the refrigeration system, which affects the refrigeration effect or even prevents refrigeration. Therefore, the refrigeration oil in the system must be removed.
When the filter oil is clogged, a new filter should be replaced. At the same time, use high-pressure nitrogen to blow out part of the refrigeration oil accumulated in the condenser. When passing nitrogen, use a hair dryer to heat the condenser.