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Immersion Transducer: Function and Application

In this blog post, you’ll read:Immersion transducer is employed in examining parts with inconsistent configuration, applicable in flaw detection and time of flight measurement.

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Do you ever wonder or ask yourself, what immersion transducers are and what they do? 

In non-destructive testing, ultrasonic testing is one of the most accurate methods in detecting flaws and assessing component quality. However, the type of transducer employed is key. In the case of immersion ultrasonic transducers, their applications are unique and specific to certain circumstances. Primarily, immersion transducers are employed where contact with the test sample will not give accurate results and will need some sort of liquid interface between the sample and the ultrasonic testing device. 

In this post, we’ll give you all the information that pertains to immersion ultrasonic transducers and their applications. So, if you are ready, let’s begin. 



What is Immersion Transducer?


An immersion ultrasonic transducer or immersion probe is a non-destructive inspection tool utilized in examining parts with inconsistent configuration. It is a favorable option for obtaining reliable results that can be duplicated effectively with coherent coupling. Immersion transducer is often employed in automated and mechanized testing for equipment partially or wholly submerged in water as earlier mentioned.

Additionally, they are usually longitudinal wave transducers characterized by a quarter wavelength surface specially crafted to transmit ultrasounds in inspection where test subjects are immersed underwater. While immersion transducers create a stable and quick coupling technique for prompt examination of various parts, the results are also very accurate.


Immersion Transducer



What are the Features and Functions of Immersion Transducers?


An immersion transducer does not make contact with the test component and its main features are designed to implement inspections in water-tight conditions. These types of transducers are fabricated to function in a wet and fluid environment as all its connections are watertight. 

Immersion transducers typically have a resistive uniform layer that helps in getting more sound energy into the water and, accordingly, into the component under inspection. Some focus lenses could be purchased with the immersion transducer which increases the sensitivity of the transducer. The focused lens could either be cylindrically focused, a planer, or a spherically focused lens. 

A focused transducer can enhance axial resolution and sensitivity when the sound energy is focused on a smaller surface area. The focal range for a particular frequency and the size of the object of inspection determines if the focus lens to be attached to the immersion transducer should be spherical or cylindrical based on request. 

Immersion transducers are usually employed in water tanks or part of a bubbler or squirter system in inspecting applications.



How does Immersion Ultrasonic Testing Work?


The working principle of immersion ultrasonic testing entails moving an ultrasound probe over the surface of the object to be inspected, as the component is placed in a water-filled tank. The sound wave from the ultrasound probe is carried through the water and travels into the inspected component. When the sound interacts with the internal microstructure of the tested part, existing defects within the interior of the component are returned to the probe through an echoed sound wave. 

Consequently, the magnitude of the returned echo and the time of arrival to the probe allows deductions to be made as to what information is being received from the tested object and where it is coming from. 

The ultrasonic probe is usually positioned on a robotic arm with a rotational movement, and the bearing of the tested part is typically automated for a wider view and range of inspection.



What are the Advantages of Immersion Transducers?


Immersion ultrasonic transducers are of great value and essential to underwater inspection and some of these values are highlighted here which is not limited to but includes the following:

Advantages of Immersion Transducers

  • Immersion transducers permit efficient assessment of enormous components when compared to regular or standard inspections.
  • The repeatability of this sort of inspection technique is high due to the reliability of water as the coupling medium.
  • Immersion transducers are non-destructive inspection techniques that cause no impairment or vandalism to its test objects, dissimilar to what destructive methods offer.
  • There is increased dimensional accuracy in inspection due to the automation of probe movement and predetermined data gathering. This enables accuracy in the data collected and precise analysis is guaranteed.
  • With immersion transducers, there is increased versatility of inspected elements’ material, size, and shape.



What are the Limitations of Immersion Transducers?


As advantageous as immersion transducers are, they are also rigged with a few limitations which may restrict inspection scope and capacity. 

One of the limitations posed by an immersion transducer is the fact that components have to be submerged in water and this can lead to corrosion reliant on the type of material to be inspected. Water is capable of causing damage to materials such as metal, stone, and other materials. Therefore, inspected components can cause corrosion.

Another limitation of the immersion transducer is the limitation caused by probe access that hinders the inspection of complex geometries. 

Lastly, it can not be applied to in-service examination and inspection due to the immersion tank required to execute this inspection medium.



What are Ultrasonic Transducers Used for? 


Immersion ultrasonic transducers are applicable in numerous inspection mechanisms, and they are deployed in various quality assessment practices. 

For flaw detection in components such as tubes, bars, plates, pipes, and other related components, the immersion ultrasonic transducers are suitable for deployment and ensure high-speed defect detections in these components.

Components like shafts, axles, and disks are also tested for flaws and defects using the immersion ultrasonic transducers as well as on-line thickness gauging which permits sound energy transmitted through the element for measuring the thickness of a material. 

Application of Ultrasonic Transducers

Additionally, they can also be deployed in measuring time of flight which entails the time taken for an electromagnetic wave to travel a distance through an element; and amplitude or dimension-based testing. 

Immersion ultrasonic transducers also can be applied to velocity measurements and material analysis which helps determine the speed and direction soundwaves are channeled and material analysis.

Other applications of immersion transducers also include automated scanning and through transmission testing. 




In conclusion, immersion ultrasonic transducers entail automated and mechanized testing for equipment partially or wholly submerged in water through an immersion transducer probe which sends out sound energy through the test object for accurate information on detected flaws in the test material.

It is also established that to increase the sensitivity of the immersion transducer, a spherical, plane, or cylindrical lens could be attached to the transducer. Similarly, a focused transducer can amplify axial resolution and sensitivity when the sound energy is channeled to a smaller surface area.

And finally, a note of caution states that a transducer should not be immersed in water for a long period exceeding 8 hours. A period of 16 hours of dry time should be exercised to ensure the extended life of the unit.

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