The things that the small cooling system fails to do
Small cold storage, including active cold storage, is usually below 100 tons. The refrigerated evaporator is composed of a tube or cold air unit, which is composed of a compressor unit (water cooling or air cooling), throttling expansion valve, etc. The compressor is mostly in semi-closed type, the larger system also has the use of open and open type, the smaller system adopts the fully enclosed type. Refrigerants are common in R22.
One, small cold storage refrigeration system failure cause
Cold storage refrigeration system, the general operation of the most common failure is: the refrigeration temperature drop slowly, blocking system operation condition caused by abnormal or unable to run, etc.
The cooling cooling temperature of the refrigerator is slow, and the adjustment of the expansion valve is the most critical. The expansion valve is less open and the refrigerant passes less and the pressure is low. The expansion valve is opened up, the coolant is flowing more and the pressure is high. According to the thermal properties of refrigerants, the lower the pressure, the lower the corresponding temperature; The higher the pressure, the higher the corresponding temperature. Under this law, if the outlet pressure of the expansion valve is too low, the corresponding evaporation pressure and temperature are too low. However, due to the decrease in the flow of evaporator, the decrease of the pressure caused the evaporation rate to slow down, the unit volume (time) cooling quantity decreased, and the cooling efficiency decreased. Conversely, if the outlet pressure is too high, the corresponding evaporation pressure and temperature are too high. Into the evaporator flow rate and pressure are increasing, due to the excess liquid evaporation, moisture gas (liquid) in the compressor, cause the wet stroke (liquid impact) of compressor, the compressor cannot work normally, causing a series of bad condition, even damage the compressor. The opening degree of the expansion valve shall be adjusted according to the library temperature at the time.
Second, small refrigerator fault handling method:
Closed fluid for total valve, open the compressor operation, inspiratory pressure is stable under 0, the exhaust valve closed compressor, stop at the end of the closed compressor operation (fluorine finished). Open expansion valve inlet fluid inlet, mesh back, after cleaning and replacement of fluids dry filters or filters, check the infusion after the performance of the solenoid valve (check is clean). Beside his open compressor exhaust (state) of the other with are still accept fluorine, boot operation, let the shutoff valves to compressor body fluid for all his spare from the exhaust air, stay inspiratory pressure is stable under 0 vacuum (extraction), closed his exhaust, open the compressor exhaust valve and total valve, fluid for system recovery operation.
If the expansion valve itself works well, just because the system caused by too much water or dirt jam phenomenon, cause serious ice blocking or dirty plugging, make the system work is not normal, expansion valve on the temperature of the liquid pipe is lower than at room temperature, condensation, even after the valve line no reaction temperature, the compressor suction pressure below 0, machine high temperature and exhaust temperature, appear even beat, refrigeration temperature does not drop, bad operation condition.
The system is overwater, mainly because the maintenance vacuum is not complete. The leak causes the low pressure to continue to run while the negative pressure is under pressure. The system is taken apart and shelved for too long. Machine parts backwater The amount of water in the refrigerated work is excessive; The cooling pipe of a water-cooled condenser is caused by the rupture of the condenser tube. The reason for the excessive system accumulation is mainly the sediment of the tube evaporator and the water cooled condenser iron oxide and the other wastes of the system.
Handle this problem, the system of sewage and water in addition to operating at the same time, the specific methods: connect the compressor of low-pressure valve beside his put fluoride, when set to 0 gage pressure, working medium can be regarded as system has been put out. To open the bottom of the evaporating pipe in front of the same side of the pipe, and install the corresponding fluorine valve. The outlet of the condenser (the condensation tube of the water cooled condenser should be resolved or replaced) should be installed with the same diameter tee and associated valve. Open compressor (water cooled condenser water supply valve should be opened), his sucked into the air from the suction, the booster compressor compression, pressure is 1.2 MPa gage pressure down, quickly open evaporation exhaust pipe lowest place beside his mouth valve and condenser liquid tee, compressed air system then dirt and water respectively by high voltage and low voltage side quickly discharge (a small space can temporarily connect hose outlet of cold storage of exhaust pipe which leads to the library, pay attention to the hose shall not be higher than outlet). When the system pressure is close to zero, restart the compressor lift and the discharge, so repeatedly, until the water and the contents of the system are identified. Stop then replaced immediately dry filters or new filter, clean the filter of the expansion valve and solenoid valve, the compressor suction strainer unpick and wash, replaced compressor lubricants, close the valve outlet of exhaust pipe and condenser liquid tee outlet, compressor of low-pressure valve fluorine bottles next to his, the exhaust valve closed compressor, open the exhaust next to his, other valve should be open in the system, start the compressor running for vacuum system and fluorine operation, restore system put into production.
In addition, the oil and air operation of the system should be done regularly or regularly to improve heat exchange performance and cooling effect of heat exchanger. Because of the large viscosity of frozen oil, it is usually adsorbed in the inner surface of the pipe or container, forming the oil film layer. Especially in the low voltage side (expansion valve outlet to compressor imported), because of the low temperature, the oil viscosity is bigger, the formation of oil film layer and a bigger, of course, thus increasing the thermal resistance of heat exchanger (evaporator and condenser), affect the heat transfer performance, reduces the refrigeration effect. The more oil in the system, the greater the disease, so it is bad for refrigeration. Air or other system exists non-condensable gas, can cause condensation pressure and temperature, increase power consumption, high operation temperature of the compressor, heavy load, reduce the refrigeration efficiency. Drain type evaporator which can be used at the lowest level of discharge; The lowest outlet of cold air unit type evaporator is an oil discharge outlet. Both oil and air operations should be carried out in a static system, and the air should be carried out when the temperature is low, which will be better. There is no system of dedicated air and air equipment, and the air is generally chosen for the highest elevation of the outlet. The evaporative drain tube of the cold bank and the cooling fan finned tube should be defrosted in time to ensure its good heat transfer effect.
