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Computers and Technology

Flow Switch- Types, Applications, and Specification

A flow switch is an instrument mechanically made to monitor or control the flow of liquids, air, or steam. When one switches it on or off, it responds to the fluid available in the pipe.
They usually operate by sending a trip signal to other devices available in the system asking them to shut on or off in response to the flow that would lead to the destruction of the pipe. They also help in cooling the circuit since it can turn off immediately after it has heated up to the maximum temperature level. In this article, we will help you to select the best flow switch for your industries and details on its proper working and how to install a flow switch.

How do Flow switches work?

The need for output measurement and the type of media usually determine how a flow switch will operate. Flow switches contain paddles and magnetic triggers, which acts as the primary mechanisms.
The paddle or magnetic is linked to the sensor passing through the fluid flow channel. The flowing fluid displaces the paddle making it rotate, thus sending a signal to the transducer, the secondary component.

The transducer then passes the signals to the transmitter after converting them into a readable format. The transmitter measures the reading, compares it to the set parameter values, and does any action required. Therefore the flow switches, monitors, reports, and manages the media flow rate through the entire or specific system.

Flow switches also ensure that the fluid flow stays within the preset parameter value. In cases where the flow rate is higher than the drops at a set level, the device can be configured to activate power on a pump, external alarm, shutting off system parts, flow diversion, etc.

How to install flow switches?

There are many different methods and procedures you can follow to install a flow switch. The type of switch in your application will determine the best approach to follow for the installation. Although some designs are always the same when it comes to installation. For example;

a) The installation or the switch should be under a straight pipeline or a duct.
b) You should not connect a flow switch near bends, valves, fittings, drains, wider or narrow areas, etc., since it can cause flow rate change in the system.
c) Ensure a perfect length of straight pipe behind and in Infront of the switch, usually, 10x pipe diameter.

Testing a flow switch also depends on the type of media used, the switch type, and where you would like to install the button. The response given by the switch when the flow starts or stops makes the operator know it is working or not. Consider taking the device for repair for it to function effectively.

Types of flow switch

We can classify flow switches depending on the type of measurement or media of the fluid flow. I.e., we can put them together as volumetric liquid flow switches. For example;

1. Liquid flow switches

Liquid flow switches control the media flow like lubricants, chemicals, water, and slurries.

2. Velocity flow switches

Velocity flow switches measure the velocity flow rate of a moving media in velocity per minute.

3. Gas flow switches

Gas flow switches measure the flow rate of media fluids such as steam and air.

4. Volumetric flow switches

Volumetric flow switches measure the volumetric flow of gases and liquids in volume per unit time.

Applications of flow switches

I) Flow switches are used to detect fluid blockage or flow.
ii) Flow switches are used to protect the flow and system pipe since they can trigger an alarm and switch off in case of hazardous flow.
iii) They are used in pump staging.
iv) Flow switches are used in the tank storage system and reservoirs to put the tanks at their designation levels and ensure consistency in the media-flowing fluid in pipelines.
v) HVAC systems in commercial, residential, and large buildings usually use large flow switches in their applications.

Specification of flow switches

Below are some of the factors to consider for the adequate performance of a flow switch.

1. Operating pressure

Operating pressure is an essential factor to consider when choosing a flow switch material type. It involves the maximum pressure head of the fluid flow media that a flow control switch can survive.

2. Pipe diameter

For a flow switch to operate effectively, it must properly fit in a specific diameter pipe where the fluid is passing through. Consider choosing a flow switch after knowing the diameter pipe you want to use for the flow measurement to be effective.

3. The media temperature range

The liner material and the device’s construction determine the media temperature range of the fluid flow, which is the maximum level of media temperature that one can control or monitor using a flow control switch.

4. Type of media

It is always important to consider the type of media in which the flow switch should measure the flow. By doing this, you will find that bronze or brass materials make water devices due to their ability to resist rusting, breakdown, or corrosion.
In cases where the materials are unlikely to expand in sweltering conditions or freeze in icy conditions, plastic materials are always the best since they are rust-resistant and can last for long ( Durable).

Flow switches can also be categorized according to their kind of style. For example;

 i) Paddle type flow switches

Paddle flow switches measure and control the flow rate in large pipe size and is usually designed for liquids with up to pressure level of 2000 PSIG to 138bar. The device’s pivot is flexible and can move out of the place where the fluid is flowing.

Applications and uses paddle-type flow switches

i) A paddle flow switch is used in heat exchanger industries, boilers, chillers, compressors, engines, and turbines to detect the fluid flow that may bring damage if not taken care of.
ii) Paddle flow switches help protect low and high pressure in pumps, helps in detecting the sensitive reverse flow rate of a fluid.

2. Piston flow switches

Piston flow switches measure or detects low flow rate gases and liquids to provide highly accurate results.

Applications and uses of piston flow switch

i) Used water dispensing, purification, and filtration to ensure proper processing integrity system.
ii) Used in food and beverage industries as well as chemical industries to measure the fluid level.
iii) Used as a coolant agent in welding, laser heads, and power supply applications.

3. Shuttle flow switches

Shuttle flow switches control the flow of moderate and high flow rates of liquids.

Applications and uses of shuttle flow switches

i) Used in compressor systems, pumps, fuel, and oil separators to reduce the maintenance costs through lubrication.
ii) Helps in chlorination, filtration, reverse osmosis, etc., systems to ensure efficient and effective working process.
iii) Used in manufacturing industries, radio transmitters, induction furnaces to automatically switch off in case of the falling in coolant flow on electric materials.


flow control switch is an important device that can protect various industrial types of equipment by automatically shutting down after detecting an issue during the fluid flow. The type of flow switch to using will depend on your application area of the operation.

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