company news about How does a pressure controller work?

A pressure controller is a specialized instrument used to control pressure in industrial process measurement and control systems, and is often referred to as a pressure switch in engineering. It is an electrical switch that uses pressure as the control signal. In refrigeration systems, it is commonly used to control and alarm system pressure, thereby protecting the refrigeration system from operating outside a reasonable pressure range. A pressure controller can control the operation of the electrical system by converting the pressure of the refrigeration system into an electrical signal. It consists of two parts: high-pressure control and low-pressure control, which are respectively connected to the high-pressure and low-pressure pipes of the compressor. When the refrigerant enters the pressure controller, the gas pressure causes the bellows to deform. The deformed bellows forces the transmission rod to move, causing the micro-switch to close or open.

According to the working principle, it can be divided into the following two major categories:

1. Mechanical pressure controller;

2. Electronic pressure controller.

A mechanical pressure controller operates by mechanical deformation causing the micro-switch to act. Its working principle is as follows:

When the pressure in the system exceeds a certain set pressure, the free end of different pressure sensing elements (such as bourdon tubes, diaphragms, bellows, corrugated tubes, pistons, etc.) will move. Through the connecting rod, the disc inside the switch will move instantaneously. When the pressure drops to the rated recovery value, the disc will move instantaneously in the opposite direction, and the switch will automatically reset, ultimately outputting a switch signal. Usually, there is a set of normally open contacts and a set of normally closed contacts.

In a gas compression refrigeration system, the section from the compressor exhaust port to the condenser to the inlet of the expansion valve (capillary tube) is the high-pressure part. The section from the outlet of the expansion valve to the evaporator to the compressor suction port is the low-pressure part.

The high-pressure pipe of the pressure controller is connected to the exhaust port of the compressor; the low-pressure pipe is connected to the suction port of the compressor. The two pipes drive the pressure sensing elements (diaphragm or bellows) to move the switches, namely the high-pressure switch and the low-pressure switch. These two switches are both for protecting the refrigeration system. The high-pressure switch prevents the system from overloading, and the low-pressure switch is used to prevent system leakage or blockage. As long as one of these two switches operates, the protection mechanism will stop the machine to prevent further damage to the system.

The normal high-pressure should be between 1.3 and 1.7 MPa (13 to 17 kg/cm² or 190 to 250 lbf/in²), and the normal low-pressure should be between 0.15 and 0.25 MPa (1.5 to 2.5 kg/cm² or 20 to 35 lbf/in²).