How Does a Pressure Switch Work?
An insight into the crucial role that pressure switches play in hydraulic systems.
An incredibly important hydraulic accessory, a pressure switch is a mechanical or electronic device designed to detect the presence of fluid pressure.
In a hydraulic system, the pressure switch continuously monitors the process pressure and is activated when a specified pressure is reached. The pressure switch is responsible for activating or deactivating the hydraulic pump when the pressure threshold is met.
Without pressure switches, even the most simple hydraulic systems may struggle to function efficiently and accurately.
This article aims to provide an overview of pressure switches, including how they work and the different types available.
Components of a pressure switch
Pressure switches typically comprise five key components:
- Terminals – both incoming and outgoing power leads are connected to the pressure switch via the terminal points
- Contacts – made from conductive materials, the contacts complete the electric circuit and allow power to be transferred
- Diaphragm – detects pressure in the system and forces the contacts apart when the threshold is met, activating the switch
- Springs – used to adjust the setpoints or cut-out points
- Lever – activates or deactivates the pressure switch
The different types of pressure switches
When it comes to selecting a pressure switch for your application, it’s important to understand the two different types: mechanical and electrical pressure switches.
Mechanical pressure switch
Mechanical pressure switches convert fluid pressure into a mechanical movement, using a spring and a piston to control the pressure at which it is activated. The pressure threshold can be pre-set and adjusted by a screw or knob, which will revert to its original state when the set pressure is met and therefore activates the switch.
Mechanical switches are simple in design and don’t require a connection to a power supply. They are typically used in less complex, low-cost applications and can handle high voltages.
Electrical pressure switch
Electrical pressure switches use an electrical pressure sensor to measure changes in inlet pressure. They supply electronic switch output signals and can provide constant pressure readings with a full digital display. They can either be factory set to optimal switch points or programmed on-site according to the application requirements.
Electronic pressure switches are equipped with many programmable functions and allow for greater flexibility and control. They are ideally suited for automated and controlled equipment that requires additional functions, customisation and accuracy.
The operating principle of a pressure switch
Pressure switches rely on the pressure generated by the hydraulic fluid to operate. It’s this pressure that will trigger the switch to turn the electrical circuit on or off, therefore activating or deactivating the hydraulic pump.
The change in pressure in the hydraulic system moves up through the diaphragm in the pressure switch. The diaphragm presses against a piston and spring, which open or close the contacts within the switch when the pressure is applied.
Open contacts close when the pressure drops, completing the circuit and activating the pump. When the pressure threshold is reached, the contacts will open again – shutting off the circuit and turning off the pump.
Why pressure switches are important in hydraulic systems
Pressure switches serve two key purposes:
- To regulate the pressure in a hydraulic system
- To protect and safeguard the equipment and components from operating at a low efficiency or being susceptible to damage
The overarching need for pressure switches is the fact that they allow for the safe and optimal performance of a hydraulic system. Without these components, various factors such as overflow and a drop or increase in pressure may go unnoticed until it’s too late.
It goes without saying that pressure switches must be reliable, robust and consistent to ensure optimal performance and operating efficiency. For this reason, purchasing from a top-class manufacturer is essential.
Flowtech are proud partners of industry-leading manufacturers Honeywell,and can supply their full catalogue of pressure switches and sensors. To find out more or make an enquiry, please get in touch with us