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Common pressure valves and protection devices for refrigeration units

November 30, 2021

1. The role of the evaporative pressure regulating valve
The evaporative pressure regulating valve is generally used in a refrigeration system with one machine and multiple storages in which a refrigeration compressor is responsible for cooling the high-temperature cold storage as well as the low-temperature cold storage. The evaporating pressure regulating valve is generally installed on the outlet pipe of the evaporator of the high and low temperature cold storage to maintain the stability of the evaporating pressure in the evaporator at different temperatures and working pressures of the system. The evaporating pressure regulating valve is divided into two types: direct acting type and control type.
2. The role of the condensing pressure regulating valve
When the condensing pressure regulating valve refrigeration system is running, the condensing pressure must be maintained within the normal range. If the condensing pressure is too high, it will cause damage to the refrigeration equipment and increase the power consumption; if the condensing pressure is too low, it will cause the refrigerant liquefaction process and the operation of the expansion valve, making the refrigeration system unable to work normally, resulting in a large cooling capacity Decline.
The condensing pressure adjustment of the water-cooled condenser is realized by adjusting the flow rate of the cooling water. According to different working principles, the condensing pressure regulating valve is divided into temperature-controlled water volume regulating valve and pressure-controlled water volume regulating valve.
Most of the condensing pressure regulating valves used in the refrigeration systems of small and medium-sized cold storages are pressure-controlled water volume regulating valves. The pressure-controlled water volume control valve directly uses the condensing pressure as the control signal to control the opening of the valve, and its working principle is the same as that of the temperature-controlled water volume control valve. In terms of structure, the pressure-controlled water volume regulating valve also has a direct-acting type.
3. The role of safety valve
In the refrigeration system of small and medium-sized cold storage, in order to prevent the high-pressure pressure of the refrigeration system from exceeding the limit value and causing the pipe burst, it is necessary to install a safety valve on the pipe of the refrigeration system. In this way, when the high-pressure pressure in the system exceeds the limit value, the safety valve is automatically activated to release the refrigerant to the low-pressure system or to the atmosphere.
It is mainly composed of valve body, valve core adjusting spring, adjusting screw and so on. The inlet end of the safety valve is connected with the high-pressure system, and the outlet end is connected with the low-pressure system. The working principle of the safety valve is that when the high-pressure pressure in the system exceeds the safety limit value, the high-pressure gas automatically pushes the valve core and discharges into the low-pressure system from the outlet. Generally, the limit value of the opening pressure of the safety valve is 2.0~2.1MPa for the R22 refrigeration system.
4. The role of fusible plugs
Fusible plugs are often used in small and medium-sized cold storage refrigeration systems that use Freon as the refrigerant to ensure the safety of high-pressure reservoirs. Fusible alloys are cast in the fusible plugs, and the melting temperature of the fusible alloys is very low, generally below 75°C. The composition of fusible alloys is different, and the melting temperature is also different. When the melting temperature parameter of the fusible alloy is used in the refrigeration system, the fusible plug with different melting temperature and composition of the fusible alloy can be selected according to the pressure to be controlled in the system.
When the refrigeration system is working, if the pressure in the accumulator suddenly rises, the temperature of the refrigerant in it will also rise. When the temperature rises to the melting temperature of the fusible alloy, the fusible alloy immediately melts, forming a gap, and the refrigerant in the reservoir is released into the atmosphere, thereby protecting the safety of people and equipment. After the fusible plug is melted, the fusible alloy must be recast and can be used after leak detection. Generally, replacement is often used in the repair process.
5. Check valve
Check valve, also known as check valve, check valve, check valve or check valve, its function is to ensure the directional flow of the medium in the pipeline without backflow. The check valve is installed on the exhaust pipe of the refrigeration compressor and the discharge pipe of the liquid pump. When installing, pay attention to the direction marked on the valve body to be consistent with the allowable refrigerant flow direction