Common pressure valves and protection devices of refrigeration unit

1. Function of evaporation pressure regulating valve

The evaporative pressure regulating valve is generally used in the refrigeration system of one machine and multiple warehouses in which a refrigeration compressor is responsible for cooling both high-temperature cold storage and low-temperature cold storage. The evaporation pressure regulating valve is generally installed on the outlet pipeline of the evaporator of high and low temperature cold storage to maintain the stability of the evaporation pressure in the evaporator at different temperatures and working pressures of the system. The evaporation pressure regulating valve is divided into direct action type and control type.

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2. Function of condensate pressure regulating valve

During the operation of the refrigeration system, the condensation pressure shall be maintained within the normal range. If the condensation pressure is too high, it will cause damage to the refrigeration equipment and increase the power consumption; If the condensation pressure is too low, it will cause the liquefaction process of refrigerant and the operation of expansion valve, so that the refrigeration system can not work normally, resulting in a significant decrease in refrigeration capacity.

The condensation pressure regulation of water-cooled condenser is realized by adjusting the flow of cooling water. According to different working principles, the condensation pressure regulating valve is divided into temperature controlled water regulating valve and pressure controlled water regulating valve.

The condensation pressure regulating valves used in the refrigeration system of small and medium-sized cold storage are mostly pressure controlled water volume regulating valves. The pressure controlled water regulating valve directly uses the condensation 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 regulating valve. Structurally, the pressure controlled water volume regulating valve also has a direct action type.

3. Function of safety valve

In the refrigeration system of small and medium-sized cold storage, in order to prevent the pipeline burst caused by the high pressure of the refrigeration system exceeding the limit value, it is necessary to set a safety valve on the pipeline of the refrigeration system. In this way, when the high-pressure pressure in the system exceeds the limit value, the safety valve will automatically start to discharge the refrigerant to the low-pressure system or to the atmosphere.

The utility model is mainly composed of a valve body, a valve core, an adjusting spring, an adjusting screw, etc. 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, the high-pressure gas will automatically open the valve core and discharge into the low-pressure system from the outlet. Generally, the opening pressure limit of the safety valve is 2.0 ~ 2.1MPa for R22 refrigeration system.

4. Function of fusible plug

Fusible plugs are often used to ensure the safety of high-pressure liquid reservoirs in the refrigeration system of small and medium-sized cold storage with freon as refrigerant. The fusible alloy is cast in the fusible plug. The melting temperature of the fusible alloy is very low, generally below 75 ℃. The melting temperature of fusible alloys varies with their composition. When the fusible alloy melting temperature parameters are used in the refrigeration system, the fusible plugs with different fusible alloy melting temperature and composition can be selected according to the pressure to be controlled in the system.

When the refrigeration system works, if the pressure in the reservoir rises suddenly, the temperature of the refrigerant will also rise. When the temperature rises to the melting temperature of the fusible alloy, the fusible alloy melts immediately to form a gap, and the refrigerant in the reservoir is released into the atmosphere, so as to protect the safety of personnel and equipment. After the fusible plug is melted, the fusible alloy shall be re cast and can be used after leak detection. Generally, it is replaced in the maintenance process.

5. Check valve

Check valve, also known as check valve, single flow valve, one-way valve or check valve, is used to ensure the directional flow of medium in the pipeline without backflow. The check valve shall be installed on the exhaust pipe of the refrigeration compressor and the outlet pipe of the liquid pump. During installation, it shall be noted that the direction marked on the valve body shall be consistent with the allowable refrigerant flow direction