A basic flow switch is a mechanical or electronic device used to detect the presence or absence of fluid flow in pipes, including gas flow. It operates by responding to changes in the fluid flow rate and activating a switch or signal when a certain flow threshold is reached.
Here's how a basic flow switch typically detects gas flow in pipes:
Mechanical Flow Switch:
Design: A mechanical flow switch consists of a vane, paddle, or piston-like mechanism located within the pipe's flow path. The design varies, but it essentially obstructs the flow to some extent when there is no or very low flow.
Operation: When gas flow starts in the pipe, the gas pushes against the vane, paddle, or piston. As the flow rate increases, the force exerted on the mechanism also increases. At a certain flow rate threshold, the force becomes strong enough to overcome a spring or counterweight, causing the mechanism to move.
Activation: The movement of the mechanism triggers a switch or relay, which can be used to control other devices or send a signal. For example, it could start a fan, activate an alarm, or close a valve to prevent excess flow.
Electronic Flow Switch:
Design: An electronic flow switch typically uses sensors to measure the fluid's velocity, pressure, or other flow-related parameters.
Operation: Sensors such as thermal, ultrasonic, or paddle sensors are placed within the pipe. These sensors can detect changes in temperature, ultrasonic wave propagation time, or pressure drop as gas flows through the pipe.
Activation: When the measured parameters exceed a predefined threshold, the electronic circuitry of the flow switch is triggered. This can lead to an electrical signal being sent to a controller or other devices.
Rotameter Flow Switch:
Design: A rotameter is a specific type of flow meter that can also be adapted for flow switch functionality. It consists of a tapered tube with a float inside it.
Operation: Gas flow causes the float to rise within the tapered tube. The height of the float within the tube corresponds to the flow rate. When the flow rate reaches a certain level, the float position triggers a switch or signal.
Activation: The switch can be part of the rotameter assembly and can be used to activate alarms, valves, or other control systems.
In all these cases, the key principle is that the flow switch detects changes in the gas flow rate and responds by activating a switch or signal to perform a specific action. The specific design and components of the flow switch may vary based on factors like the type of gas, pipe diameter, and the required sensitivity of the detection.