What Is a Flow Switch?

A flow switch, also known as flow switches or flow sensors, is responsible for controlling and monitoring the flow rate of fluids. In the event of a significant increase or decrease in the flow rate beyond a preset level, it activates an alarm to protect equipment and sends an electrical signal to a PLC (Programmable Logic Controller) or electrical controllers.

In the following, we will introduce and examine various types of flow switches, which are one of the flow measurement devices.

Types of Flow Switches

• Paddle Flow Switch

• Piston Flow Switch

• Ultrasonic Flow Switch

• Thermal Flow Switch

• Piezo Flow Switch

• Flow Switches with Pipe Tees

• Turbine Flow Switch

Paddle Flow Switch

A paddle flow switch has a blade. Due to the fluid flow, the paddle moves, and when it reaches a preset point, it sends an electrical signal for a response. With an increase or decrease in fluid flow, it commands the microswitch for on or off. Paddle flow switches are used in steam boilers, HVAC (Heating, Ventilation, and Air Conditioning) systems, damper control based on flow, and protection of pumps, motors, chillers, and cooling systems, fire suppression, medical devices, and other equipment where fluid flow must be checked.

Piston Flow Switch

A piston flow switch consists of a piston and a spring; the piston moves due to the fluid flow and controls the system, while the spring returns the piston to its initial state.

Piston flow switches are used in systems with low flow rates and are used in detecting low flow in cooling lines and high-pressure oil, air, water, and gases processing systems.

Ultrasonic Flow Switch

The ultrasonic flow switch has a flow sensor that is installed outside the pipes. By changing the flow rate of fluid passing through the pipe, the sensor sends an electrical signal.

Thermal Flow Switch

Thermal or heat transfer flow switches operate based on convective heat transfer. These flow switches have two temperature sensors: one is the process temperature sensor, and the other is heated by the passage of the hot fluid flow. As the flow rate increases, the temperature difference between the sensors decreases. When the temperature difference reaches the set point, the relay changes and causes an increase or decrease in flow or flow interruption.

Piezo Flow Switch

Piezo flow switches are flow switches that act as on-off flow switches and are used in oil spray systems, drum rollers, distributors, and food processing.

Flow Switches with Pipe Tees

In the linear flow switch, a blade is embedded in the flow switch and is placed in the path of fluid flow. It sends an electrical signal based on the preset conditions, with an increase or decrease in fluid flow.

Turbine Flow Switch

Turbine flow switches are used in cases where fluid flow is low, and the process temperature and pressure are low (such as package flow switch).

Applications of Flow Switches

Flow switches have a wide range of applications in various industries and are classified into two categories: liquid flow switches and air flow switches.

• Cooling Systems

• Sprinkler Systems

• Water Heaters

• HVAC Systems

• Fluid Transfer Systems

• Water Purification and Chlorination

Applications of Air Flow Switches

• Exhaust Ventilation

• Room Air Purification and Filtration Systems

• Duct Heating

• Air Supply Systems

Key Considerations When Buying and Selecting a Flow Switch

• Type of Connection

• Connection Type

• Flow Range

• Viscosity or Fluid Density