What Causes Float Switches to Fail?

Even although there are various types of level sensing technologies on the market today, many people associate a liquid level sensor with a “float switch”.

For many applications where liquids need to be monitored within a tank or other container, float switches are the most cost effective solution.

There are various types of float switches and they can be configured in a number of different ways. Typically, the way in which a float switch operates uses a magnetic reed switch, breaking or connecting an electrical circuit when liquids reach a designated level.

While these switches are commonly used for tank level applications, they can fail and cause unreliability issues. When failure occurs, it can cause malfunction or costly damage to equipment, proving that not all cost effective measurement methods can save money or time in the long term.

The main causes for failure in this type of float switch is down to three common faults.

  • Poor maintenance
  • Selecting the wrong switch for your application
  • Moving parts

The first is poor maintenance. All float switches require regular maintenance checks in order to prolong the lifetime of the product. If no or very little maintenance is carried out the lifetime is significantly reduced and will cause early failure. It is important to refer to the sensor manual for the recommended maintenance checklist or guidelines.

Poor research can lead to wrong decisions. Many customers often find themselves in a situation where the float switch is failing because it is not suited for the application. Depending on the application, you may need a switch that is made from a different material or a switch that is made with a specific mechanical configuration. Getting the best match between your equipment and your application is without a doubt the best preventative maintenance you can do. The functionality of the switch, environmental and physical factors are all important to consider before making a purchase to ensure the float switch will suit your application requirements.

In many applications the environment can be dirty, corrosive and in some instances hazardous. However, when you are faced with these conditions, it is important to ensure the technology you choose can a) survive when exposed to this environment and b) be a reliable source. More often than not, if no maintenance checks are being carried out on a regular basis, when the switch is exposed to these conditions, debris and dirt often jam in the switches moving parts causing false and unreliable readings.


Why Choose Optical vs Float?

Optical liquid level switches is another type of level sensing technology offering a competitive edge over float switches as they are maintenance free and solid state, with no moving parts. Optical liquid level switches are commonly used in tank level measurement applications. They can detect tiny amounts of liquid if positioned correctly, unlike floats where the liquid level has to be substantial before making contact with the switch. They are easy to install, the level switch protrudes very slightly into the wall of the tank with the sensor tip facing inwards. They are small and compact meaning they can be installed where space is limited.  They have a long operating life and low sensitivity to ambient light and robust enough to operate in wide operating temperatures and harsh liquid media.


How does the sensor work?

When in air, the infrared light inside the sensor tip is reflected back to the detector. When in liquid, the infrared light is refracted out of the sensor tip causing less energy to reach the detector. The output is either high or low, so they are very simple to understand and operate.


For more information on SST’s optical liquid level switches, please Ask our Experts!

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