Solutions to Common Problems in the Installation, Maintenance and Use of Cold Storage

I. The refrigeration compressor unit is not installed with vibration reduction measures, or the vibration reduction effect is poor. According to the installation specifications, the whole vibration reduction device of the unit should be installed. If the vibration reduction is not standardized or there are no vibration reduction measures, the machine will vibrate violently, which is likely to cause the pipeline to crack, the equipment to be damaged, and even the machine room to be damaged.

II. The refrigerant pipeline does not have or lacks an oil return bend. When the pipeline transporting the refrigerant turns upward from the horizontal direction, it must be made into a small bend that first hangs downward and then goes upward, that is, a U-shaped bend. Only in this way is the pipeline qualified when it goes upward again. It cannot be directly made to turn upward at a 90-degree angle. Otherwise, the oil in the system cannot return to the compressor well, but will deposit in the air cooler in large quantities, making the air cooler and the whole system unable to function properly, and even damaging the air cooler and the unit equipment.

III. The connection of the refrigerant pipeline is unbalanced. When the unit pipeline is connected to a group of multiple compressors, to evenly distribute the oil return to each compressor, the interface of the main pipeline must be set in the middle position of multiple compressor heads, and then some branch pipelines should be set on both sides respectively, allowing the oil return to flow evenly into the branch pipes of multiple compressors. Moreover, valves should be installed on each branch pipe to adjust the amount of oil return.

IV. The pipeline is not insulated. Without insulation materials, the cold pipeline will frost under the ambient temperature, which will affect the refrigeration effect, increase the load of the unit, and then make the unit operate with excessive intensity, reducing the service life of the unit.

V. Regularly check various technical indicators and adjust them in a timely manner. The operating temperature and pressure of the system, as well as the amounts of lubricating oil and refrigerant, should all be checked and adjusted in a timely manner. The system should have an automatic control device and a compressor alarm device. Once there is a problem, it will issue an alarm prompt or automatically shut down for protection, and the compressor will stop running.

VI. Maintenance of the unit. Regularly replace the lubricating oil and the filter. Supplement the refrigerant as needed. The condenser should be cleaned at any time to keep it clean, so as to prevent dust, sediment, flying fluff or other debris from affecting the refrigeration effect. The lubricating oil has been running at a high temperature in the system for a long time, and its performance may have changed, failing to play its due role in lubrication and other aspects. The filter should also be replaced regularly. As we know, general machines have "three filters", which also need to be replaced regularly.

VII. Installation environment and maintenance issues of the air cooler. The position and environment of the air cooler inside the cold storage will affect its operation. Generally, the air cooler near the cold storage door is prone to condensation and frosting.

Although the air cooler can automatically heat and defrost regularly, if the door is opened too frequently and for too long, and the hot air flow enters for a long time and in a large amount, the defrosting effect of the air cooler will not be good. Because the defrosting time of the air cooler cannot be too long, otherwise the refrigeration time will be relatively shortened, the refrigeration effect will be poor, and the temperature in the cold storage cannot be guaranteed.

VIII. The drainage problem of the water melted during the defrosting of the air cooler. This problem is related to the severity of frosting. Due to severe frosting of the air cooler, a large amount of condensed water will inevitably be generated. If the water receiving tray of the air cooler cannot bear it and the drainage is not smooth, the water will leak and flow onto the ground inside the cold storage. If there are goods stored below, the goods will be soaked. In this case, a thicker diversion pipe can be installed to discharge the condensed water.
Some air coolers have the problem of water being blown out from the fan and spraying onto the goods stored in the cold storage.

This is also a frosting problem of the air cooler in a hot and cold exchange environment. It is mainly the condensed water generated by the fan blades in a hot environment, rather than a problem of the defrosting effect of the air cooler itself.

IX. Problems with the condenser fan motor and the electric heating tube of the air cooler. These are vulnerable components. The fan motor that runs for a long time in a high-temperature environment may malfunction and be damaged. If it is very important to ensure the temperature of the cold storage, some vulnerable parts should be ordered for timely maintenance.

X. Problems with the temperature of the cold storage and the cold storage door. The area of a cold storage, the inventory quantity, the number of doors opened, the opening and closing time and frequency of the doors, the in and out frequency of the inventory, and the cargo throughput are all factors affecting the temperature inside the cold storage.
The design and construction of the cold storage, as well as the setting and quantity of the cold storage doors, must be comprehensively arranged according to the inventory quantity and the frequency of opening and closing the doors. The user unit of the cold storage should also use the cold storage reasonably according to the design specifications. It cannot blindly increase the inventory quantity and the cargo turnover quantity regardless of the design conditions and the actual situation of the facilities, exceeding the normal load and bearing capacity of the facilities and equipment. Otherwise, many problems will occur.

XI. Fire safety issues of the cold storage. The temperature in the cold storage is generally around minus 20 degrees Celsius. Due to the low ambient temperature, it is not suitable to install a fire sprinkler system. Therefore, more attention should be paid to fire prevention in the cold storage. Although the ambient temperature in the cold storage is low, if there is a fire and there are combustibles in the warehouse, especially the goods are often packed in cartons and wooden boxes, which are very easy to burn. Therefore, the fire hazard of the cold storage is also very high, and fireworks are strictly prohibited in the cold storage. At the same time, the air cooler, its wire box, the power cord, and the electric heating tube should also be regularly checked to eliminate potential electrical fire hazards.

XII. The problem of the ambient temperature of the condenser. The condenser is generally installed on the roof of the building outdoors. In the environment with a high temperature in summer, the temperature of the condenser itself is very high, increasing the operating pressure of the unit. If there are many high-temperature days, a shed can be built on the roof above the condenser to block the sunlight, reduce the temperature of the condenser, so as to achieve the purpose of reducing the pressure on the machine, protecting the unit equipment, and ensuring the temperature of the cold storage. Of course, if the capacity of the unit is sufficient to ensure the temperature of the cold storage, the shed can also not be built.

XIII. The problem of low compressor efficiency. Due to long-term operation of the compressor, components such as the cylinder liner and the piston ring are severely worn, the clearance between the mating parts increases, the sealing performance will correspondingly decrease, the gas delivery coefficient of the compressor will also decrease, and the refrigeration capacity will be reduced. The refrigeration capacity of the compressor can be roughly judged by observing the suction and exhaust pressures of the compressor. If the refrigeration capacity of the compressor decreases, a common method is to replace the cylinder liner and the piston ring of the compressor.

XIV. The problem that there is a large amount of air or refrigeration oil in the evaporator of the cold storage. Once a large amount of refrigeration oil adheres to the inner surface of the heat transfer tubes in the evaporator of the cold storage, its heat transfer coefficient will decrease. Similarly, if there is a large amount of air in the heat transfer tubes, the heat transfer area of the evaporator will decrease, and its heat transfer efficiency will also decrease significantly, and the rate of temperature drop in the storage room will slow down accordingly. Therefore, in daily operation and maintenance, attention should be paid to timely removing the oil stains on the inner surface of the heat transfer tubes of the evaporator and discharging the air in the evaporator.

XV. The problem that the throttle valve of the cold storage is improperly adjusted or blocked, and the refrigerant flow rate is too large or too small. When the opening degree of the throttle valve is too large, the refrigerant flow rate is relatively large, the evaporation pressure and the evaporation temperature will also rise, and the rate of temperature drop in the storage room will slow down; at the same time, when the opening degree of the throttle valve is too small or blocked, the refrigerant flow rate will also decrease, and the refrigeration capacity of the system will also decrease, and the rate of temperature drop in the storage room will also slow down.

Generally, it can be judged whether the refrigerant flow rate of the throttle valve is appropriate by observing the evaporation pressure, the evaporation temperature and the frosting situation of the suction pipe.
Blockage is an important factor affecting the refrigerant flow rate. The main reasons for the blockage of the throttle valve are ice blockage and dirt blockage.
Ice blockage is caused by the poor drying effect of the dryer. The refrigerant contains moisture. When flowing through the throttle valve, the temperature drops below 0°C, and the moisture in the refrigerant freezes into ice and blocks the throttle valve hole.
Dirt blockage is caused by a large amount of dirt accumulating on the filter screen at the inlet of the throttle valve, resulting in poor refrigerant flow and blockage.