Refrigeration components and common maintenance and treatment methods

Refrigeration components and common maintenance and treatment methods

1. Refrigeration components and functions

　　1. Compressor: It acts as a compression drive refrigerant in the refrigerant circuit. The compressor extracts the refrigerant from the low-pressure zone, compresses it, and sends it to the high-pressure zone for cooling and condensation. The heat is dissipated into the air through the radiating fins. The refrigerant also changes from a gaseous state to a liquid state, and the pressure increases. The compressor's working circuit is divided into evaporation zone (low pressure zone) and condensation zone (high pressure zone). The refrigerant flows from the high-pressure area to the low-pressure area, and is injected into the evaporator through a capillary tube or an expansion valve. The pressure drops sharply, and the liquid refrigerant immediately becomes a gaseous state, which absorbs a large amount of heat in the air through the heat sink. In this way, the compressor continues to work, and it continuously absorbs the heat at one end of the low-pressure zone into the refrigerant and then sends it to the high-pressure zone to be dissipated into the air, thereby regulating the temperature.

　　2. Condenser: It is one of the main heat exchange equipment in the cold storage refrigeration system. Its function is to cool and condense the high-temperature refrigerant superheated vapor discharged from the assembled cold storage compressor into a high-pressure liquid.

3. Evaporator: It absorbs the heat in the cold storage, so that the liquid refrigerant absorbs the heat transmitted from the freezer and evaporates under the low pressure and low temperature evaporation, and becomes a gaseous refrigerant. The gaseous refrigerant is sucked into the compressor and compressed. , And then discharged into the condenser to remove heat. Basically, the principle of the evaporator and the condenser is the same, the difference is that the former is to absorb heat into the library, and the latter is to discharge heat to the outside.

　　4. Liquid storage tank: storage tank for freon to ensure that the refrigerant is always saturated.

　　5. Solenoid valve: One prevents the high-pressure part of the refrigerant liquid from entering the evaporator when the compressor is stopped, to avoid the low pressure when the compressor is started next time, and to prevent the compressor from liquid shock. Second, when the temperature of the cold storage reaches the set value, the thermostat will act, and the solenoid valve will lose power, and the compressor will stop when the low pressure reaches the stop set value. When the temperature in the cold storage rises to the set value, the thermostat will act and the solenoid valve will When the low-pressure pressure rises to the compressor start-up setting value, the compressor will start.

　　6. ​​High and low pressure protector: protect the compressor from high pressure and low pressure.

　　7. Thermostat: It is equivalent to the cold storage brain controlling the opening and stopping of the cold storage refrigeration, defrosting, and the opening and closing of the fan.

　　 8. Dry filter: filter impurities and moisture in the system.

　　 9. Oil pressure protector: to ensure that the compressor has enough lubricating oil.

10. Expansion valve: also called throttle valve, it can make the high and low pressure of the system form a huge pressure difference, make the high pressure refrigerating liquid at the outlet of the expansion valve quickly swell and evaporate, absorb the heat in the air through the pipe wall, and exchange heat and cold. .

　　11. Oil separator: Its function is to separate the lubricating oil in the high-pressure steam discharged from the refrigeration compressor to ensure the safe and efficient operation of the device. According to the oil separation principle of reducing the airflow speed and changing the airflow direction, the oil particles in the high-pressure steam are separated under the action of gravity. Generally, if the air flow velocity is below 1m/s, the oil particles with a diameter of 0.2mm or more contained in the steam can be separated. There are four types of oil separators commonly used: washing type, centrifugal type, packing type and filtering type.

　　12. Evaporator pressure regulating valve: It prevents the evaporator pressure (and evaporating temperature) from falling below the specified value. Sometimes it is also used to adjust the force of the evaporator to adapt to changes in load.

　　 2. The cooling effect is poor or the cold storage is not cooling

　　 Check if the condenser of the refrigerator is dirty. Check whether the frost is too thick on the evaporator in the warehouse. Check if the refrigerant is leaking (coat the pipe connection with soapy water, there are bubbles that indicate refrigerant leakage). And ask professionals to add refrigerant and deal with the leakage. Check whether the seal of the cold storage door is intact and eliminate it. Check whether the refrigerator in the cold storage is working. Check whether the parameter setting of the computer controller of the cold storage is correct and readjust it. Check whether the controller of the cold storage is malfunctioning and replace it. Check whether there are enough gaps for the items stacked in the warehouse and clear them.

　　 1. There is abnormal noise when the machine is running?

　　 Please stop and check whether it is caused by vibration or mechanical failure. There is abnormal noise in the distribution box. This is the sound of the AC contactor. It is due to the inflexibility of the moving parts of the contactor. Please come back and press the iron suction of the contactor to eliminate the abnormal noise.

　　2. The refrigerator starts frequently or does not start for a long time, or does not stop after a long time, or it stops when the storage temperature is not reached?

A. Check whether there is dirt on the condenser. Poor heat dissipation will cause the condensing pressure of the refrigerator to be too high. In order to protect the compressor, the machine will stop running under the action of the pressure controller. After the heat dissipation is good, press the pressure controller. The black reset button, the machine can automatically resume operation. B. The parameter setting of the controller is wrong, just reset it. C. The refrigeration is not good, please refer to fault 2. D. The temperature control fails. E. The electrical appliance is damaged.

　　3. The cold storage distribution box does not respond after the brake, but the three-phase power is normal.

　　 Please check whether the neutral line has 220V voltage. The parts of the cold storage (various valves, controllers) have been set, and there are no parts that users need to adjust.

　　 4. The lighting in the library does not light up.

　　 Please check if the switch is malfunctioning and the bulb is damaged. When checking, cut off the power supply and pay attention to the waterproof of the lamp when installing the lamp cover.

　　5. When the ambient temperature is too high, after the refrigerator has been running for a period of time, the refrigerator has not reached the set value and the refrigerator will be stopped early?

This is because the condensing pressure of the refrigerator is too high due to the increase of the ambient temperature. In order to protect the compressor from stopping the operation of the machine under the action of the pressure controller, after the heat dissipation is good, press the black reset button on the pressure controller, and the machine can automatically Resume operation. And check whether the water condenser heats well. Do not arbitrarily adjust the set value on the pressure controller, otherwise the pressure controller will not play the role of protecting the refrigerator.

　　 3. Poor cooling effect

　　 Poor cooling effect means that the cold storage can operate normally, but the temperature in the storage cannot drop to the set temperature under the specified working conditions. The main reason is:

　　1, refrigerant leakage

　　 After the refrigerant leaks in the system, the cooling capacity is insufficient, the suction and discharge pressures are low, and the intermittent "squeaking" airflow sound can be heard much louder than usual at the expansion valve. The evaporator has no frost or a small amount of frost on the corners. If the expansion valve hole is adjusted, the suction pressure will not change much. After the shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.

　　Removal method: After the refrigerant leaks, do not rush to fill the system with refrigerant, but immediately find the leakage point, and fill the refrigerant after repair. The refrigeration system adopting the open-type compressor has more joints and more sealing surfaces, correspondingly more potential leakage points. During maintenance, attention must be paid to the easy leaking links, and based on experience, find out whether there are oil leaks, pipeline breaks, loose streets, etc. at a major leakage point.

　　 2. Too much refrigerant is charged after maintenance

The amount of refrigerant charged in the refrigeration system after maintenance exceeds the capacity of the system, the refrigerant will occupy a certain volume of the condenser, reduce the heat dissipation area, and reduce the cooling effect, and the suction and discharge pressures are generally higher than normal pressure Value, the evaporator is not frosted, and the temperature in the warehouse is slow.

　　Removal method: According to the operating procedure, the excess refrigerant must be discharged at the high-pressure shut-off valve after a few minutes of shutdown. At this time, the residual air in the system can also be discharged.

　　 3. There is air in the refrigeration system

The air in the refrigeration system will reduce the refrigeration efficiency. The prominent phenomenon is that the suction and discharge pressure increase (but the discharge pressure has not exceeded the rated value), and the temperature from the compressor outlet to the condenser inlet increases significantly. Air, exhaust pressure and exhaust temperature all increase.

　　Removal method: A few minutes after the shutdown, air can be discharged from the high-pressure shut-off valve several times in succession, and some refrigerant can be properly filled according to the actual situation.

　　4. Low compressor efficiency

　　 The low efficiency of the refrigeration compressor means that under the condition of the same working condition, the actual displacement decreases and the refrigeration capacity decreases accordingly. This phenomenon mostly occurs on compressors that have been used for a long time. The wear is large, the matching gap of each part is large, and the sealing performance of the valve is reduced, which causes the actual displacement to decrease.

Judgment method: Close the suction shut-off valve and let the compressor run for a few minutes, discharge the refrigerant in the crankcase into the condenser, stop the machine and immediately close the exhaust valve, and install high-pressure valves on the bypass holes of the suction and exhaust shut-off valves. , Low pressure gauge, turn on again, loosen the connection of the bypass hole of the suction stop valve, let the air slowly suck into the compressor, so that the pressure in the compressor's discharge chamber will rise slowly, and the pressure will rise to 1.MPa, then tighten Stop the intake of air and let the compressor continue to run for a few minutes to stop, and stop for 10 minutes to see the low-pressure vacuum recovery. If the high and low pressures are balanced within 10 minutes, it means that the valve plate has serious leakage.

　　Remedy: (1) Check whether the cylinder head paper gasket is broken down and cause leakage, and if it is, replace it. (2) Check whether the high and low pressure exhaust valves are not tightly closed, and replace them if they are. (3) Check the clearance between the piston and the cylinder. If the clearance is too large, replace it.

　　 5. The frost on the surface of the evaporator is too thick

Long-term use of cold storage evaporator should be defrosted regularly. If it is not defrosted, the frost layer on the evaporator pipeline will become thicker. When the entire pipeline is wrapped into a transparent ice layer, it will seriously affect heat transfer and cause the temperature inside the warehouse. It is not within the required range.

　　Removal method: stop defrosting, open the door of the storage room to allow air to circulate, or use a fan to accelerate the circulation to reduce the defrosting time. Do not hit the frost layer with iron or wooden sticks to prevent damage to the evaporator pipeline.

　　 6. There is refrigerating oil in the evaporator pipeline

　　 During the refrigeration cycle, some refrigerating oil remains in the evaporator pipeline. After a long period of use, when there is more residual oil in the evaporator, it will seriously affect the heat transfer effect and cause poor cooling.

　　 Judgment method: (1) Check whether the refrigerant oil in the crankcase of the compressor is less than before or open the expansion valve to observe the oil in the refrigerant. (2) Judging from the frosting condition of the evaporator, if the white frost on the evaporator is incomplete and unreliable, and no other faults are found at this time, it can be concluded that the cooling effect caused by oil is poor.

　　Removal method: remove the refrigerant oil in the evaporator. Remove the evaporator, blow it out, and then dry it. If it is not easy to disassemble, it can be pumped by a compressor from the inlet of the evaporator, and then dried with a blowtorch.

　　7, the refrigeration system is not smooth

　　Because the refrigeration system is not cleaned, after a certain period of use, dirt will gradually accumulate in the filter, and part of the mesh will be blocked, which reduces the refrigerant flow rate and affects the cooling effect. The expansion valve and the filter at the suction port of the compressor in the system are also slightly blocked.

　　 Judgment method: the exhaust pressure is low, the exhaust temperature drops, the temperature of the blocked part is lower than the normal temperature, when the blockage is serious, frost will appear, gentleman frosting.

　　Removal method: The micro-blocking parts can be removed, cleaned, dried, and then installed.

　　Four, small cold storage is not cooling

　　 1. All refrigerant in the system leaked,

　　 The cause of refrigerant leakage

　　Slow leakage: It is not used for a period of time, and the leakage is discovered when it is used or it is gradually not cold during use, and finally it is not cooled.

　　Quick leak: Due to the sudden rupture of the system pipeline, the refrigerant leaks out quickly.

　　 Judgment method: The compressor starts easily (when the compressor components are not damaged), the suction pressure is vacuum, the exhaust pressure is very low, the exhaust pipe is cool, and the sound of liquid water is not heard in the evaporator.

　　Removal method: check the whole machine, mainly check the leak-prone parts. After the leakage is found, it can be repaired according to the specific situation, and finally vacuumed and filled with refrigerant.

　　 5. The refrigeration system is blocked

　　 1. The expansion valve hole is frozen and blocked

　　Fault analysis: (1) Improper drying treatment of main components in the refrigeration system; (2) Incomplete vacuuming of the entire system; (3) The moisture content of the refrigerant exceeds the standard.

　　 Judgment method: Intermittent refrigeration: Start refrigeration normally. After maintaining for a period of time, the entire surface of the expansion valve begins to form frost. When the evaporation temperature reaches 0°C, moisture accumulates at the expansion valve hole and gradually blocks the valve hole. Then there is frosting at the evaporator, no airflow sound is heard, and the suction pressure is in a vacuum state. Use hot water to heat the expansion valve, the ice layer at the valve hole melts, and it can be cooled normally.

　　Discharge method: String a filter with moisture absorbent (silica gel, anhydrous calcium chloride) in the refrigeration system to filter out the water in the system, and then remove the filter.

　　2, the expansion valve filter is dirty

　　Fault analysis: When there are more coarse powdery dirt in the system, the entire filter screen will be blocked, and the refrigerant cannot pass, resulting in no cooling.

　　 Judgment method: knocking on the expansion valve, sometimes some refrigerant can be used to achieve refrigeration.

　　 discharge method: remove the filter, clean, dry, and reinstall it in the system.

　　3, the filter is clogged

　　Fault analysis: The desiccant has been used for a long time and becomes a paste to seal the filter or dirt gradually accumulates in the filter to cause blockage.

　　 Judgment method: Ventilation will occur after tapping the filter, and touching the filter by hand is cooler than usual.

　　Discharge method: Remove the filter for cleaning, dry, replace the washed desiccant, and put it into the system.

　　4. The refrigerant leaks in the expansion valve bulb

Failure analysis: After the temperature sensing agent in the expansion valve temperature sensor leaks, the two forces below the diaphragm push the diaphragm upward, and the valve hole is closed, and the refrigerant in the system cannot pass, resulting in no cooling. At this time, the expansion valve does not form frost. , The low pressure presents a vacuum, and no airflow sound is heard in the evaporator.

　　 Judgment method: (1) Loosen the inlet of the expansion valve to see if there is refrigerant spraying out, if yes, close it quickly. (2) Open the expansion valve port to see if there is refrigerant spraying out, if not, it means that it is blocked.

　　Discharge method: shut down the shut-off valve, remove the expansion valve to check whether the filter is blocked, if not, use the mouth to blow the inlet of the expansion valve to see if it is ventilated. It can also be inspected visually or disassembled for inspection, and replaced when damaged.

　　 5. Too much refrigerant is charged in the system

　　Fault analysis: Excessive refrigerant causes the exhaust pressure to rise significantly, exceeding the normal value.

　　Discharge method: Stop the machine and discharge the excess refrigerant out of the system through the high-pressure vent.

　　 6. There is residual air in the system

　　 Failure analysis: There is air circulation in the system, the exhaust pressure is too high, the exhaust temperature is high, the exhaust pipe is hot, the cooling effect is poor, the compressor runs shortly, and the exhaust pressure exceeds the normal value, forcing the pressure relay to act.

　　Exhaust method: Stop the machine and release air at the exhaust valve hole.

　　7. Shutdown caused by low suction pressure

　　Fault analysis: When the suction pressure in the system is lower than the setting value of the pressure relay, the electric shock action will cut off the power supply.

　　Discharge method: 1. The refrigerant leaks. 2. The system is blocked.

　　 8. The compressor suddenly stops during operation

Failure analysis: cold storage with air-cooled condenser (1) The fan is not turned on (2) The fan motor is damaged (3) The fan is reversed (4) The ambient temperature is high (up to 40 degrees or more) (5) The condenser heat sink is damaged Oil and dust block the air flow.

　　 Shutdown caused by excessive exhaust pressure. (Poor heat dissipation effect of condenser)

　　9, motor overload

　　Fault analysis: 1. Too much food was put in the warehouse during use; 2. The power supply was abnormal.

　　Discharge method: reduce the heat load, pay attention to the change of the power supply voltage.

　　10. There is a malfunction in the electrical appliance causing a shutdown.

　　Fault analysis: The thermostat is not adjusted properly or the temperature sensor is installed improperly.

　　Discharge method: Remove the thermostat to repair the electric shock, adjust, and adjust the position of the temperature sensor.

11, sudden changes caused by other reasons

Failure analysis: In the process of use and maintenance, it is often necessary to open and close the shut-off valves of the exhaust, suction and liquid reservoirs. Sometimes the shut-off valves are opened inadvertently, causing the exhaust pressure to rise sharply.

　　 discharge method: stop immediately to prevent danger.

　　 12. Normal shutdown: When the temperature in the storage reaches the set value, the thermostat will automatically shut down.