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How does a magnetic float switch work?

Liquid level measurement and control is all around us in our everyday lives, from your car fuel tank to your toilet cistern.

 

But liquid level measurement is also used extensively in production and processing plants, such as chemical plants, refineries and distilleries. Too much liquid and we risk spillage, waste, or damage.  Too little and we run out of product, or pumps and systems run dry. Each case represents a cost and also often a danger.

 

So, let’s look at how a magnetic float switch works, to understand how the technology enables rugged and reliable operation, day after day.

 

How does a magnetic float switch work

 

The need for rugged and reliable point level measurement stems back more than a century, to control water levels in boilers and other appliances.

 

Trusted reliability in aggressive environments

 

Established as the standard instrument for industrial level measurement in control, particularly in aggressive and extreme environments, magnetic float switches have proven to be a successful and reliable instrument in use throughout the world for a multitude of both routine and safety-critical applications.

 

Components of a typical horizontal float switch

 

Split into three main parts, a typical horizontal float switch consists of a switch enclosure, a switch mechanism and a float (as seen below).

 

Magnetic float switch body Magnetic float switch mechanism Magnetic float switch float
Switch enclosure Switch mechanism
(housed within the switch enclosure)
Float

 

The simplicity and reliability of the magnetic float switch is down to its two opposing magnets.  One ‘wet-side’ and one ‘dry-side’.

 

The switch enclosure literally houses the switch mechanism, encasing it within a tough alloy to protect it from damage.

 

The mechanism contained within the housing provides the switching signal and contains one half of the opposing magnets.

 

Finally, the float itself, well it floats, rising and falling depending on the level of the liquid, but importantly, the bar on the float contains the other half of the opposing magnet.

 

Simple ‘snap-action’ mechanism

 

When the liquid level rises in your typical storage tank, the float pivots upwards.  The ‘wet-side’ magnet on the float repels the opposing magnet within the ‘dry-side’ switch mechanism in a strong snap movement, activating the switch.

 

Magnetic float switch mechanism for high-level liquid alarm

Similarly, when the liquid level drops in a tank the float pivots downwards, repelling the opposing magnet and activating the switch.

 

Magnetic float switch mechanism for low-level liquid alarm

The beauty is that there’s no contact between the switch mechanism and the float – no springs or physical interaction, just a ‘snap’ action when the opposing magnets repel – and the only parts which come into contact with the liquid is the float.

 

This is why magnetic float switches have proven to be ideal for long-term, low maintenance use, since there are few parts to wear out, plus are also particularly suited for aggressive environments, since the snap action switch is unaffected by viscous liquids, temperature or pressure.

 

 

Float switches in industrial storage tanks

 

 

Regular & diverse industrial uses

 

Typically, the magnetic float switch is used for pumps or level alarm to provide highly reliable liquid level control, preventing costly or dangerous overflows and low storage levels depending on the application. Naturally, magnetic float switches are available in a range of options and configurations to suit a wide range of application demands.

 

 

Did you know?

 

Developed in 1947 by then Chief Engineer Leonard Bomyer, the first magnetic float switch was called ‘the Mobrey’ (an anagram of his surname).

 

 

Want to find out more? Download our datasheet…

 

View the Delta Mobrey magnetic float switch datasheet

 

Learn more about horizontal float switches »

 


 

About Delta Mobrey

 

With a proud history spanning over 100 years, Delta Mobrey Limited is a recognised global specialist in the design & manufacture of quality process instrumentation for the measurement and control of fluid and gases in all industrial plant and equipment.

 

Trusted Quality – Proven Value

 

Quality and reliability have always formed the cornerstone of the company’s success, recognised by industry with international approvals covering every aspect of our manufacturing and product portfolio, together with certifications spanning all areas of hazardous and regulated environments.

 

Global Team – Local Support

 

As a global organisation, Delta Mobrey is totally committed to delivering the best possible customer service and technical support, ensuring a lifetime value of ownership together with a flexible and responsive approach to meet each customer’s individual demands.

 

About Delta Mobrey