Flow Switch

$ 225.00$ 295.00

The SRS flow switch utilizes the force of liquid flow to propel its paddle and to detect the incoming flow or movement of the existing liquid in the pipe.  In static liquid or no liquid, the spring is in expanded and presses the magnet downward.  The reed switch is normally open.

As flow occurs and the paddle is raised at an upward angle of 20 to 30 degrees, the paddle will push the magnet upward to actuate the reed switch which then closes the circuit.  The length of the paddle can be adjusted to the diameter of the pipe.


Flow SwitchVane type of Flow Switch utilizes the flow rate of water to drive the vane to test whether the liquid in the tube/vessel flows or not.  When the liquid in the tube/vessel does not flow, the spring presses the magnet and makes the vane vertical, at this moment, the spring switch has no operation, the contact point is at a “NO” state.

When the liquid flows in the tube/vessel and the flow is big enough to crash the vane.  This happens when higher to 20 to 30 degrees.  It will also happen when the eccentric strap drive above the vane pushes the magnet upward.  Also, when the suction force of the magnet makes the magnetic spring switch operate, while the contact point is connected, the length of the vane changes due to the diameter of the pipe.

A flow switch is an essential device used in various industries to monitor the flow of liquids or gases in a pipeline or system.  It is designed to detect changes in the flow rate and trigger specific actions or control mechanisms accordingly.  In this article, we will explore the key components, working principle, types, applications, and benefits of flow switches.


At its core, a flow switch consists of four main components: a flow sensing element, a switch mechanism, a housing, and electrical connections.  The flow sensing element is responsible for measuring the flow rate, while the switch mechanism detects the changes and actuates the switch accordingly.  The housing protects the internal components from the external environment and provides a suitable connection to the system.  Lastly, the electrical connections allow for the integration of the flow switch with the control circuit.

The working principle of a flow switch is based on the principle of fluid dynamics.  When a fluid flows through a pipeline or system, it exerts a force on the internal components.  The flow sensing element, often a paddle wheel, vane, or turbine, is designed to rotate or move when exposed to this force.  As the flow rate increases or decreases, the rotation or movement of the sensing element changes.  This change is then detected by the switch mechanism, which triggers the opening or closing of the switch.

Various Types of Flow Switches

Flow switches come in various types, each suitable for different applications based on factors such as flow rate, fluid type, and system requirements.  Some common types include paddle flow switches, thermal flow switches, magnetic flow switches, and differential pressure flow switches.  Paddle flow switches use a paddle that moves or rotates with the flow, while thermal flow switches rely on temperature changes caused by flow variations.  Magnetic flow switches utilize the principles of electromagnetism to detect flow, and differential pressure flow switches measure the pressure difference across a constriction in the pipeline.

These flow switches find applications in numerous industries including HVAC systems, water treatment plants, oil and gas refining, chemical processing, and pharmaceutical manufacturing.  In HVAC systems, flow switches are used to monitor the flow of water or air and trigger the operation of pumps, fans, or alarms.  Water treatment plants employ flow switches to ensure proper water flow for filtration, disinfection, and distribution processes.  In the oil and gas industry, flow switches play a crucial role in monitoring the flow of various fluids during extraction, transportation, and refining processes.  Similarly, in chemical and pharmaceutical industries, flow switches help maintain precise flow control and prevent any unwanted variations.

Main Benefits of a Flow Switch

The benefits of using flow switches are multifold. Firstly, they ensure the safe and efficient operation of systems by detecting abnormal flow conditions such as low flow, no flow, or excessive flow.  This helps prevent equipment damage, system failure, or potential hazards. Secondly, flow switches enable automated control and feedback mechanisms, reducing the need for manual monitoring and intervention.  They can be integrated into control circuits, allowing for real-time data analysis and decision-making.  Additionally, flow switches are generally easy to install, require minimal maintenance, and offer long-term reliability and durability.

In conclusion, flow switches are indispensable devices used in a wide range of industries to monitor fluid flow and trigger necessary actions or controls.  Their key components, working principle, types, applications, and benefits have been discussed in detail.  Whether it’s maintaining the flow of water in a distribution system or ensuring the smooth operation of an industrial process, flow switches play a crucial role in maintaining efficiency and safety.


The length of the vane decides the position of the operating point. Firstly, determine the length of the vane according to the pipe size and the expected position of the operating point. Make some mark on the vane and cut the vane (Users also can cut the length in a no-mark place according to specific requirements).

The plane of vane should be installed with a section of pipe in parallel and fixed on the end of the thread.

Make sure that the “FLOW” mark on the product must be parallel with the catheter when the installation is finished. (The pipe of flow circuiting must be horizontal.)

When the float switch needs to fix on the T contact, it must be enlaced.  The enlacing is with a leaking-proof belt and is locked on the end of the thread.


Flow switches have numerous applications across various industries where monitoring and controlling fluid flow is crucial.  Some common applications of flow switches include:

HVAC Systems

Flow switches are widely used in heating, ventilation, and air conditioning (HVAC) systems.  They monitor the flow of water or air in pipes and channels, ensuring proper circulation.  Flow switches in HVAC systems can trigger the operation of pumps, fans, or alarms in case of inadequate flow, preventing equipment damage and system failures.

Water Treatment Plants

Flow switches play a critical role in water treatment plants.  They monitor the flow of water during filtration, disinfection, and distribution processes.  If the flow deviates from the desired range, flow switches can trigger alarms or control valves, ensuring efficient and consistent water treatment.

Oil and Gas Industry

Flow switches are extensively used in the oil and gas industry to monitor the flow of various fluids.  They facilitate flow measurement during extraction, transportation, and refining processes.  Flow switches help ensure optimal flow rates, detect leaks, and trigger alarms or emergency shutdowns if flow conditions deviate from the specified range.

Chemical Processing

In chemical processing plants, flow switches are employed to maintain accurate flow control and prevent variations that could impact the quality of the end product.  They help monitor flow rates during mixing, reactions, and transfer of chemicals from one process to another.  Flow switches play a crucial role in maintaining process efficiency and avoiding unwanted fluctuations.

Pharmaceutical Manufacturing

Flow switches find applications in the pharmaceutical industry, where precise control of fluid flow is imperative.  They are used in processes such as drug formulation, purification, and packaging, where consistent flow rates are essential for consistent product quality. Flow switches facilitate real-time monitoring and control, ensuring compliance with industry standards and regulations.

Industrial Cooling Systems

Flow switches are utilized in industrial cooling systems to monitor the flow of coolants or water used for temperature control.  They ensure that the required flow is maintained for effective cooling of machinery and equipment.  Flow switches also aid in detecting blockages or inadequate flow, preventing equipment overheating and potential breakdowns.

Fire Protection Systems

Flow switches play a vital role in fire protection systems, such as sprinkler systems.  They monitor the flow of water within the system and provide valuable feedback to the control panel.  If a sprinkler head is activated, flow switches detect the flow of water and trigger alarms or the appropriate response, enabling swift fire control and minimizing damage.

Hydraulic Systems

Flow switches are often integrated into hydraulic systems to monitor fluid flow rates.  They help regulate the flow to different components, such as valves, cylinders, and motors, ensuring optimal performance and preventing damage due to inadequate flow.

These are just a few examples of the diverse applications of flow switches.  Their ability to monitor and control fluid flow is invaluable across industries, where precise flow management is crucial for system efficiency, safety, and product quality.

Advantages of Flow Switches

Flow Monitoring

Flow switches allow continuous monitoring of fluid flow, ensuring that flow rates remain within desired parameters.  This helps maintain system efficiency and prevents potential issues caused by inadequate or excessive flow.

Automated Control

Flow switches can be integrated into control circuits, enabling automated control mechanisms.  They can trigger the operation of pumps, fans, alarms, or other devices based on flow conditions, reducing the need for manual monitoring and intervention.

Safety Measures

Flow switches play a crucial role in ensuring the safety of systems and processes.  They can detect abnormal flow conditions such as low flow, no flow, or excessive flow, triggering alarms or initiating shutdown procedures to prevent equipment damage or hazards.

Process Optimization

By monitoring flow rates, flow switches help optimize processes in various industries. Maintaining accurate flow control ensures consistent product quality, avoids variations, and enhances overall efficiency.


Flow switches are generally reliable and durable devices.  They are designed to withstand harsh environmental conditions and have a long operational life, making them suitable for demanding industrial applications.

Easy Installation

Flow switches are typically easy to install and integrate into existing systems.  They often come with simple mounting mechanisms and provide flexible options for connection to the control circuit.

Disadvantages of Flow Switches


Although flow switches generally require minimal maintenance, periodic inspection and cleaning may be necessary to ensure optimal performance.  Accumulation of debris or sediment can hinder the proper functioning of the flow sensing element and affect accuracy.

Sensitivity to Fluid Properties

Some flow switches may be sensitive to specific fluid properties, such as viscosity or chemical composition.  It’s important to select the appropriate flow switch model suitable for the fluid being monitored to ensure accurate measurements.


Depending on the specific requirements and industry, flow switches can vary in cost.  They may have a higher upfront cost compared to less sophisticated flow monitoring devices. However, their functionality and long-term reliability often outweigh the initial investment.

Limited Flow Range

Different flow switches have specific flow rate ranges within which they can accurately measure and respond to flow changes.  If the flow exceeds or falls below this range, the flow switch may not provide reliable readings or fail to trigger the required actions.

Size and Space Requirements

Some flow switches, especially those designed for high flow rates, can be relatively large in size.  This may pose challenges when space is limited or when retrofitting existing systems.

Overall, the advantages of flow switches, such as flow monitoring, automated control, safety measures, and process optimization.  This makes them valuable devices across various industries.  While they may have some limitations like maintenance requirements or sensitivity to specific fluid properties.  Additionally, these factors can often be addressed with proper selection, installation, and regular maintenance practices.

If you are looking for Coriolis, Turbine, Electromagnetic, Vortex, Ultrasonic Flow Meters.

Additional information

Weight 3 lbs
Dimensions 14 × 8 × 8 in

1/2", 3/4", 1", 1-1/2", 2"


120 / 208 VAC, 24 VDC


Explosion Proof, General Duty, Intrinsically Safe

Type of Connection

Flanged, NPT Threaded, Triclamp

QC Test Certificate

No, Yes


Flow Switch Specification Sheet



Housing Material:  Aluminum Alloy, NEMA 4 (IP65)
Operation Temp.:  -30 to 150°C (30 to 300°F)
Paddle Material:  SUS304 (Similar to 304 SS)
Operation Pressure:  355 psig
Pressure Drop Allowance:  3 psig
Set Point Tolerance:  ±25%
Repeatability Tolerance:  ±5%
Contact Capacity:  30 Watts/200 Vdc, SPDT
Max Viscosity:  200 SSU or 43 centistokes



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