Submersible Sensors: Features and Applications

Subsea operating conditions are some of the most challenging scenarios when choosing a position sensor technology. Although most machines and heavy equipment that run in these environments use sensors for a variety of processes, not all sensor technology is suitable for working reliably underwater.

 

A submersible sensor may be considered as among the most durable types of position sensors available today. The unique design and function of a submersible sensor make it possible to perform infinitely and reliably for many years.

 

Submersible linear variable differential transducer

 

Subsea or marine environments pose many challenges for engineers because saltwater has a chemical composition that can corrode and degrade ordinary metals. The microorganisms present in seawater can also contribute to the early deterioration of linear position sensors. Submersible LVDTs are typically constructed using a special alloy or high-grade stainless steel that can withstand these elements.

 

The housing of a submersible LVDT protects the internal assembly and keeps it airtight. It is essential to fabricate a highly reliable device because it is not cost-effective to keep replacing sensors once they start degrading.

 

Features of a submersible linear position sensor

 

It is possible for a submersible sensor to work underwater at depths of 7,500 feet and be subject to a pressure of 3500 psi. The alloy composition of the sensor housing contains nickel and chromium which are excellent in protecting the device from corrosion. Using these unique alloy combinations further enhances the durability of LVDTs when used underwater.

 

In general, a subsea LVDT has the same working principle and features of a standard LVDT but the unique composition and material used to fabricate them provide higher chemical resistance to saltwater. In many similar applications, subsea LVDTs have replaced traditional position sensors such as potentiometers, load cells, and magnetostrictive transducers.

 

Typical applications of submersible sensors

 

Since submersible linear position sensors are expected to work even in the harshest of conditions, some of the typical uses of these devices are in the offshore oil and gas mining industry. Nevertheless, it is also a suitable device for applications where the sensor is submerged in clean water such as in municipal utility facilities and desalination plants. Specifically, submersible sensors measure water in refineries, beverage manufacturing, oil mining, holding tanks, and reservoirs.

 

Possible drawbacks of LVDTs

 

Although we can conclude that subsea LVDTs are far superior to other sensor technologies when used in underwater applications, there are still a few potential drawbacks to this technology.

 

  • LVDTs are highly sensitive to an adjacent or stray magnetic field. When applied in any assembly, it is essential for the engineer to consider the impact of magnetic fields surrounding the device.
  • Extreme changes in temperature may impact the performance of an LVDT. But since subsea LVDTs are specially fabricated with hermetic sealing, a temperature change is not likely going to be an issue.

In conclusion, subsea LVDTs are a more advanced approach to traditional position sensing used many decades ago. With the availability of cheaper circuitry and exotic alloys, many of the earlier deficiencies have been improved upon or wholly eliminated.

 

Image: Pixabay.com

 

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