A basic flow switch is a simple device designed to detect the presence or absence of fluid flow (liquid or gas) in a pipe. In the case of detecting gas flow in pipes, the flow switch operates based on the principle of differential pressure.
Here's how a basic flow switch works to detect gas flow in pipes:
Flow Sensing Element: The flow switch contains a flow sensing element, typically a paddle, vane, or a spring-loaded diaphragm. This element is positioned in the path of the gas flow within the pipe.
Differential Pressure: When gas flows through the pipe, it creates a pressure differential between the upstream (inlet) and downstream (outlet) sides of the flow sensing element. The gas pressure on the upstream side of the element is higher compared to the downstream side.
Threshold Pressure Setting: The flow switch is designed with an adjustable threshold pressure setting. This setting determines the minimum pressure differential required to activate the switch.
Switch Mechanism: Inside the flow switch, there is a switch mechanism that responds to the pressure differential across the flow sensing element. When the gas flow reaches or exceeds the threshold pressure, the switch is triggered.
Switch State: Once the switch is activated, it changes its state. For instance, if the switch was initially in the "OFF" state, it would switch to the "ON" state when the gas flow exceeds the set threshold. Conversely, when the gas flow drops below the threshold, the switch will revert to the "OFF" state.
Output Signal: The switch's change in state can be used to control other equipment, such as turning on or off a pump, actuating an alarm, or sending a signal to a monitoring system, depending on the application.
It's important to note that a basic flow switch is a simple device and may not provide precise measurements of gas flow rates. It is primarily used for flow detection and basic control functions rather than precise flow measurement. For more accurate flow measurement, specialized flow meters such as thermal mass flow meters, vortex flow meters, or differential pressure flow meters are used.