Home Technology Understanding Flow Switch and It’s Working

Understanding Flow Switch and It’s Working


Industrial processes require various tools and instruments to increase efficiency and productivity. Among this equipment are flow meters and flow switches. These two devices help to sense, monitor, and measure liquid and gas flow rates accurately. Let’s focus on the flow switch device to see what it offers in the flow measurement industry. 

What is a Fluid Flow Switch? 

A flow switch is a liquid, gas, or steam controlling device that works mechanically. This essential flow device works by conveying a trip action to other machines in the system. Most of the time, flow switches are designed to send trip signals to pumps, prompting them to either turn on or off. Doing this helps protect other devices from breakage, cooling the circuit, or adjusting the flow rate when it’s too high or too low. 

Besides being used in many applications, flow switches also perform numerous functions within a hydraulic system. They are quite handy for protecting the pump or monitoring the flow rate efficiently. Electrical signals are sent by a flow meter to parts of an electronic controller, including PLC. The physical movement or velocity is liquid, steam, or gas within a pipe or an open channel is known as a flow. There must be some type of liquid, gas, or steam flow for flow switches to work. The flow usually triggers a flow switch. 

Velocity will drop or stop when the fluid is no longer flowing. Once this happens, the switch will go back to its original position. Once the flow is no longer there, the flow meter will indicate that flow has stopped or reduced.

How Flow Switches Work 

A flow switch is activated by a paddle connected to it. Displacement of the connected Paddle happens when gas, steam, or water passes through the switch. If the volume of the substance flowing through the pipe is too high or too low, the switch locks the circuit off. This action is meant to prevent any breakage within the system. 

Functions of a Flow Switch 

Liquid flow switches perform various functions in many flow systems, including heating hot water, chlorination of swimming pools, fire sprinkler systems, air conditioning, industrial laser cooling systems, liquid transfer systems, and many more. A water flow switch is used in sprinkler systems in fire break-out instances. It is used to trigger a fire alarm to turn on. In applications that use air, flow switches are ideal for air treatment systems, exhaust ventilation, and cleanroom filter systems. 

Other functions of a flow switch in industrial processes include:

  • In case the flow supply gets off, a flow switch is used to trigger an alarm
  • A flow switch will cause an electric motor to shut down if the flow is insufficient 
  • Flow switches are also used to control ventilation and air conditioning systems 
  • These flow measurement devices are also used in central heating systems
  • Duct type heating
  • Additive or blending systems
  • Water treatment systems
  • Air supply systems

When choosing a flow switch, you should consider these factors first:

The type of flow switch needed in that particular application. Since numerous flow switches perform different tasks, the user needs to know whether the flow switch is meant for pump protection, coolant systems, or lubricant systems. For flow switches to work accordingly, accurate measurement of flow rate is crucial. 

Dynamic energy or velocity change in liquid, gas, or steam is calculated to accurately flow. Velocity depends on the pressure that forces the substance into or out of the pipe. Velocity is ideal for monitoring and measuring flow rate since a cross-sectional area of a pipe is constantly known. To set the flow switch to work, calculating and knowing the flow rate is critical properly. 

Flow Switch Types 

Variable Area Flow Switch

An internal piston activates the switch in the device. Pressure from the fluid flowing through the port pushes the magnetic poppet, and the switch turns off once the pressure reaches the preset level. 

Vane-Operated Flow Switch

A vane-operated flow switch depends on the liquid flowing through the and pushing against the internal Paddle to function properly. The flow switch is tripped when an internal magnetic, mechanical, and coupling switch actuation lever is triggered. This occurs when flow drops to its preset levels. 

Ultrasonic Flow Switch

An ultrasonic flow switch is installed outside the pipe. If a change in flow occurs inside the pipe, it sends signals to alert other devices, which trigger actions.


To maximize the productivity and profitability of a plant or a system that uses liquids, gases, or steam, flow switches are required. Not only do these essential devices protect expensive machinery against damage, but they also help to improve efficiency in a liquid, gas, or steam flow system. Ask for guidance from the manufacturer if you are unsure which type of flow switch is required in your application. 


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