Pressure Valve Switch: A Basic Introduction

A pressure valve switch is a device that controls the flow of fluid in a hydraulic system by opening or closing an electrical circuit at a preset pressure level. Pressure valve switches are widely used in industrial applications, such as pumps, valves, boosters, compressors, and other hydraulic equipment, to ensure the safety and efficiency of the system.

How does a pressure valve switch work?

A pressure valve switch works either mechanically or electronically, depending on the type and design of the switch. The basic principle is that the switch senses the pressure of the fluid in the system and compares it to a set point. When the pressure reaches or exceeds the set point, the switch activates or deactivates an electrical contact, which in turn controls the operation of the hydraulic device.

The most common types of pressure valve switches are:

  • Diaphragm pressure switches: These switches use a flexible diaphragm as the sensing element, which is attached to a spring and a contact. As the pressure increases, the diaphragm deflects and compresses the spring, until it reaches a point where the contact is made or broken. Diaphragm pressure switches are suitable for low to medium pressure ranges and can handle various fluids, such as air, water, oil, and gas.
  • Bellow pressure switches: These switches use a metal bellow as the sensing element, which is a cylindrical tube that expands or contracts with the pressure. The bellow is connected to a rod and a contact, which move along with the bellow. When the pressure reaches a certain level, the rod pushes or pulls the contact, opening or closing the circuit. Bellow pressure switches are suitable for high pressure ranges and can withstand high temperatures and corrosive fluids.
  • Electronic pressure switches: These switches use a pressure sensor, such as a piezoelectric, strain gauge, or capacitive sensor, to measure the pressure electronically. The sensor converts the pressure into an electrical signal, which is then processed by a microcontroller or a circuit board. The microcontroller or the circuit board then controls a relay or a transistor, which switches the electrical contact on or off. Electronic pressure switches are more accurate, reliable, and versatile than mechanical switches, as they can be programmed to perform various functions, such as displaying the pressure, setting the hysteresis, and adjusting the switching point.

What are the advantages and disadvantages of pressure valve switches?

Pressure valve switches have several advantages and disadvantages, depending on the type and application of the switch. Some of the common advantages are:

  • They are simple, robust, and easy to install and maintain.
  • They provide a reliable and fast response to pressure changes.
  • They can handle a wide range of pressures, fluids, and temperatures.
  • They can prevent damage, leakage, and overheating of the hydraulic system by regulating the pressure.

Some of the common disadvantages are:

  • They are prone to wear and tear, especially the mechanical switches, which can affect their accuracy and performance over time.
  • They can be affected by vibration, shock, and dirt, which can cause false or delayed switching.
  • They can have a limited number of switching cycles, which can reduce their lifespan.
  • They can have a high differential pressure, which is the difference between the switching point and the reset point, which can cause fluctuations and instability in the system.

How to choose the right pressure valve switch?

Choosing the right pressure valve switch depends on several factors, such as:

  • The pressure range and accuracy required for the application.
  • The type and properties of the fluid in the system, such as viscosity, density, and compatibility.
  • The environmental conditions, such as temperature, humidity, and dust.
  • The electrical specifications, such as voltage, current, and power.
  • The size, shape, and mounting options of the switch.
  • The cost, availability, and quality of the switch.

To help you choose the right pressure valve switch, you can use the following table, which summarizes some of the features and specifications of different types of switches:


Type Pressure range Accuracy Fluid compatibility Temperature range Differential pressure Electrical rating Advantages Disadvantages
Diaphragm Low to medium Low to medium Good Low to medium High Low to medium Simple, cheap, durable Prone to wear, affected by vibration, limited cycles
Bellow High Medium to high Excellent High Medium to high Medium to high Robust, stable, withstands high temperature and pressure Expensive, complex, affected by shock, limited cycles
Electronic Low to high High Good to excellent Low to high Low to medium Low to high Accurate, reliable, versatile, programmable Costly, sensitive, requires power supply, needs calibration

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