What is a Pressure Switch and How Does it Work?

Pressure switch is a device that detects and responds to changes in pressure in a fluid, such as air, water, oil, or gas. The switch operates an electrical contact when a certain set pressure is reached, either on pressure rise or on pressure fall. A pressure switch can control or monitor various processes and systems that use pressurized fluids, such as pumps, compressors, boilers, HVAC equipment, etc.

It consists of a sensing element, a switching mechanism, and a set point adjustment. The sensing element is the part that deforms or moves according to the applied pressure. It can be a diaphragm, a bellows, a piston, or a Bourdon tube. The switching mechanism is the part that opens or closes an electrical circuit based on the movement of the sensing element. It can be a snap-action switch, a mercury switch, or an electronic switch. The set point adjustment is the part that allows the user to set the desired pressure level at which the switch will operate.

Principle of a pressure switch

The basic working principle of a pressure switch is as follows:

• When the fluid pressure reaches the set point, the sensing element deforms or moves and activates the switching mechanism.
• The switching mechanism then changes the state of the electrical contact, either from open to closed or from closed to open, depending on the type of switch.
• The electrical contact then sends a signal to a control device, such as a relay, a solenoid valve, an indicator light, an alarm, etc., to perform a desired action.
• When the fluid pressure drops below or rises above the set point, depending on the type of switch, the sensing element returns to its original position and deactivates the switching mechanism.
• The switching mechanism then restores the state of the electrical contact to its previous condition, and the signal to the control device is stopped.

Types of Pressure Switches

There are different types of pressure switch available in the market, depending on their design, function, and application. Some of the common types of pressure switches are:

• Mechanical pressure switches: These are pressure switches that use mechanical components, such as springs, levers, cams, etc., to operate the switching mechanism. They are simple, reliable, and inexpensive, but they may have limited accuracy and durability.
• Electronic pressure switches: These are pressure switches that use electronic components, such as transducers, sensors, microprocessors, etc., to operate the switching mechanism. They are more accurate, sensitive, and versatile than mechanical switches, but they may require more power and maintenance.
• Differential pressure switches: These are pressure switches that measure and compare the difference between two pressures in a system. They are useful for detecting clogs, leaks, filter conditions, flow rates, etc.
• Vacuum pressure switches: These are pressure switches that measure and respond to negative pressures or vacuums in a system. The applications such as vacuum pumps, suction devices, pneumatic systems, etc.

Applications of Pressure Switches

Pressure switches have a wide range of applications in various industries and sectors. Some of the common applications of pressure switches are:

• Compressed air systems: Pressure switches regulate and monitor the air pressure in compressors, tanks, pipelines, tools, etc. They can also control the start and stop cycles of compressors and prevent overloading or overheating.
• HVAC equipment: Pressure switches ensure the proper operation and safety of heating, ventilation, and air conditioning equipment. They can also detect low refrigerant levels, high condenser pressures, low suction pressures, etc.
• Pumping systems: Pressure switches control and protect pumps from dry running, overpressure, underpressure, etc. They can also maintain constant water pressure in water supply systems.
• Process equipment: Pressure switches monitor and control various parameters in process equipment such as boilers, furnaces, reactors, etc. They can also activate safety valves, relief valves, bypass valves, etc.

Regulations and Standards for Pressure Switches in UAE

The use of pressure switch in the UAE is regulated by various authorities and organisations that set the rules and guidelines for their design, installation, testing, inspection, and maintenance. Some of these authorities and organizations are:

• Dubai Civil Defence (DCD): DCD is the government authority that oversees all aspects of fire safety in Dubai. DCD issues approvals, licenses, certificates, permits, inspections, and audits for fire protection systems and equipment in Dubai. DCD also enforces the UAE Fire and Life Safety Code of Practice (FLSC), which is a comprehensive document that covers all aspects of fire safety in buildings.

• National Fire Protection Association (NFPA): NFPA is an international organization that develops and publishes consensus codes and standards for fire safety. NFPA has several standards that apply to fire protection piping systems, such as NFPA 13 (Standard for Installation of Sprinkler Systems), NFPA 14 (Standard for Installation of Standpipe Systems), NFPA 25 (Standard for Inspection Testing Maintenance Water Based Fire Protection Systems), etc.
• Underwriters Laboratories (UL): UL is an independent organization that tests and certifies products for safety. UL has several standards that apply to fire protection piping systems components such as valves, fittings couplings, etc., such as UL 1479 (Standard for Fire Tests of Penetration Firestops), UL 1821 (Standard for Thermoplastic Sprinkler Pipe and Fittings for Fire Protection Service), UL 2443 (Standard for Pipe Hanger Equipment for Fire Protection Service),etc.

Conclusion

A pressure switch is a device that detects and responds to changes in pressure in a fluid. A pressure switch can control or monitor various processes and systems. It use pressurized fluids, such as compressed air systems, HVAC equipment, pumping systems, process equipment, etc. Pressure switch consists of a sensing element, a switching mechanism, and a set point adjustment. Different types of pressure switches are available in the market, depending on their design, function, and application. The use of pressure switches in the UAE is regulated by various authorities and organizations. The rules and guidelines for their design, installation, testing, inspection, and maintenance.