What is the pressure relay used for?

- Oct 07, 2019-

Relays are a type of control device commonly used in our lives. In the common sense, they are switches that are turned off or on when conditions are met. The switching characteristics of relays are widely used in many control systems, especially discrete control systems.


The pressure relay looks very novel, and it is well understood when it is linked to the electric contact pressure gauge. In fact, they are similar. Compared with the commonly used relays, only the driving force for the contact action is different, the relay is powered by the coil to make the contact work, and the pressure relay is operated by the pressure.


Pressure relay basic information


The pressure relays are diaphragm type, plunger type, spring tube and bellows type. Although the four structures of the pressure relay are different, the pressure of the fluid medium is used to turn on or off the contacts. Therefore, when used in a hydraulic system, the pressure value is set according to the process, but when the hydraulic system pressure reaches the set value, a signal is sent to cause the electrical component, the actuator, the motor, and the like to operate.


The role of the pressure relay


The function of the pressure relay is to send an electrical signal to operate an electrical component (such as a solenoid valve coil or an intermediate relay) when the pressure of the hydraulic system rises to a certain value to achieve sequential action or safety protection.


The role of pressure relays in refrigeration systems


In industrial refrigeration, a pressure relay is an electrical switch that is controlled by a pressure signal. It is often used as a protection and regulation component to directly control the start and stop of a refrigeration compressor or to control the opening and closing of certain solenoid valves. Pressure relays used in refrigeration units are classified into low-voltage relays and high-voltage relays according to their pressure control ranges. There are also two types of relays assembled in one housing and sharing one electrical contact to form a combined high and low voltage relay. The refrigeration compressor is often equipped with a low-voltage relay that directly controls the starting circuit. The compressor suction pressure is used as an action signal, and its function is:

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(1) When the suction pressure is too low, the compressor is automatically stopped to prevent air from leaking into the system from the pipeline or shaft seal, and it plays a role of low pressure protection.


(2) In the small refrigeration device, in addition to the low-pressure protection, the compressor can be automatically started and stopped according to the set suction pressure to keep the temperature of the cold storage stable and to adjust the temperature of the storage. In the large and medium-sized devices, since the starting current of the compressor is large, the low-voltage relay is not used to automatically start the compressor, so it only serves as a low-voltage protection.


(3) In addition, some piston compressors are also equipped with low-voltage relays, which are the central part of the equipment, the heart of the normal operation of the control equipment, and the scavenger when the equipment has problems, so pick the good The equipment first depends on whether his pressure relay can withstand the damage of the equipment. If it is enough to carry the load of the equipment, it is a good pressure relay. Therefore, everyone must buy a brand-name product when selecting a pressure relay.