Pressure Switch -Indispensable Control Component in Modern Industrial and Control Systems
What is a pressure switch?
Pressure switch is an essential component for detecting and controlling pressure levels in various systems that automatically opens or closes circuits in response to pressure changes. It ensures the stable operation of systems such as pumps, compressors and hydraulic machinery and is widely used in everyday appliances such as water pumps, HVAC systems and even industrial equipment.
How does a pressure switch work?
The pressure switch actuates when process pressure will run:
The pressure source applies pressure through the process connection. This pressure exerts force on the actuator (also called the diaphragm) that causes it to move upward.
However the opposing force generated by the spring and adjusting nut prevents the actuator from moving upward.
To move the actuator assembly, the force from the pressure source must be greater than the opposing force from the spring.
The switch setting can be controlled by the adjusting nut:When the adjusting nut is raised, the spring force decreases (lowering the set point).When the adjusting nut is lowered, the spring force increases (raising the set point).
When the process pressure eventually overcomes the spring force, the actuator pushes upward that displaces the stem and causes the switch to change state.
The components of a pressure switch
Diaphragm or Piston: Senses pressure changes in the system.
Contacts: Open or close the circuit when pressure reaches a set threshold.
Spring: Holds the diaphragm or piston in place and adjusts the switch’s triggering time.
These components work together to ensure that the system maintains a safe and optimal pressure level.
Pressure Range
Choosing a pressure switch with an incompatible pressure range for your system can damage your system.
Pressure switch ranges include absolute, relative, differential and sealing pressure and usually include several key parameters:
Range: The total pressure range the switch can sense.
Adjustable Range: Within the range the user can set the pressure range at which the switch triggers. The adjustable range is typically smaller than the total range.
Setpoint: The specific pressure at which the user wants the switch to trigger.
Deadband/Differential Pressure: In an automatic reset switch this represents the difference between the reset pressure and the trip pressure.
Calibration Procedure
Calibration is the process of adjusting the switch so that it triggers at the correct pressure level. Ensuring proper calibration helps prevent over- or under-pressure in systems such as pumps that also can damage the system.
Before calibrating a normally open high-alarm pressure switch, first disconnect the device from the power supply to ensure safe operation. Next, properly connect the pressure standard, pressure source, and pressure switch, and ensure that all air is removed from the lines. Also, connect the multimeter probes to the switch’s output contacts and set the multimeter to the on/off position.
Once all preparations are complete, calibration can begin.
Types of Pressure Switch
The pressure switch has many kinds that are most commonly categorized into two types: mechanical and electronic. The following table summarizes the features and advantages of various pressure switches by major category.
| Type | Feature | Advantages |
| mechanical pressure switch | The electrical contacts are directly triggered through the physical interaction between mechanical elements and the pressure medium. | High reliability, ruggedness, low cost, and no external power supply required |
| Piston Pressure Switch | Fluid pressure causes the piston to move axially that directly or indirectly operates the electrical contacts. | Adaptable and rugged；it can handle high pressure. |
| Diaphragm Pressure Switch | A metal or elastic diaphragm bends in response to pressure changes, actuating the switch. | It is sensitive to low pressures and has good pollution resistance. |
| Bourdon Tube Pressure Switch | The coiled metal tube attempts to straighten under pressure that transmits motion to the switch mechanism. | Highly repeatable and suitable for high pressures |
| Differential Pressure Switch | Measures the difference between two pressure ports and activates when the pressure differential exceeds a set point. | Used for monitoring flow, liquid level or filter status |
| Snap Disc Pressure Switch | A metal disc rapidly switches between convex and concave shapes under specific pressure, actuating the switch. | Precise and fast operation, long life and high reliability |
| electronic pressure switch | The pressure sensor transmits the signal to the processor, which controls the output of the electronic switch after comparing it with the set value. | High accuracy, stable set points, rich functionality, and fast response |
| High Pressure Switch | Designed for extremely high pressures (up to over 10,000 psig); it adopts a robust metal diaphragm and piston mechanism. | High-pressure resistance, fast response, high safety and corrosion-resistant materials |
| Low Pressure Switch | Highly sensitive to even the slightest pressure changes or underpressure; it adopts a lightweight mechanism including a precision diaphragm. | High sensitivity |
How to Maintain Pressure Switch’s Operation?
Pressure switch failures can impact the operation of the entire system. Common failures include that contacts sticking prevent the switch from opening and closing properly due to dirt or corrosion and inaccurate pressure settings prevent the switch from reaching the desired level.
Use a multimeter to test the open and closed state of its contacts and a pressure gauge to verify that it actuates accurately at the specified pressure to determine whether a switch is functioning properly.
Failure can be caused by a variety of common reasons: Internal damage may be caused by pressure exceeding the operating limit of the pressure switch.
Long-term use of pressure switch will also cause mechanical wear and dust or corrosive substances will affect the contact performance.
Therefore when we choose a pressure switch, we need to ensure that its pressure range is suitable for the system and its material can withstand the temperature of the chemical environment during operation.
Conclusion
Pressure switch is an important component for ensuring safe and efficient operation of various systems. Whether mechanical or electronic, choosing the right pressure switch for your application ensures reliability and avoids costly downtime. China SNS Pneumatic is committed to providing high-quality pressure switches through robust research and advanced manufacturing.