Ultrasonic Testing (UT)

Ultrasonic Testing is a volumetric Non-Destructive Testing (NDT) method. Unlike surface inspection methods, UT makes it possible to find flaws inside the material. High-frequency sound waves are sent into the material with an ultrasonic transducer. The ultrasound that reflects off defects in the material is made visible in a graph. Ultrasonic Testing gives insight in the depth, size, nature and orientation of the detected indications. The thickness of the material, such as wall thickness of pipes, can also be measured. MME Group has decades of experience in applying UT inspections across all industrial sectors.

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Advantages of Ultrasonic Testing:

  • High penetrating power
  • High sensitivity
  • Usually only one surface needs to be accessible
  • Insight in size, orientation, shape and nature of defects
  • Non-hazardous to operations or nearby personnel
  • Portable equipment
  • Can be used in automated setup
  • Immediate test results

Limitations of Ultrasonic Testing:

  • Surface must be accessible to transmit ultrasound
  • Usually a couplant (gel or oil) is needed to enable interference-free transfer of the ultrasound
  • Objects that have a rough surface or are very small, thin or not homogenous are difficult to inspect
  • Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise
  • Linear flaws oriented parallel to the direction of the sound beam may go undetected
  • Reference standards are required for equipment calibration and for the characterization of flaws

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  • What sort of materials can be tested with Ultrasonic Testing?

    In industrial applications, UT is widely used on metals, plastics, composites, and ceramics with a sufficiently homogenic structure. The only materials that are not suitable for ultrasonic testing with conventional equipment are wood and paper products.

  • What kind of indications can be found with Ultrasonic Testing?

    This method can be used to find cracks, laminations, shrinkage cavities, gas holes, slag inclusions, incomplete fusion, incomplete penetration and lack of bonding in a wide variety of materials.

  • Why does Ultrasonic Testing require applying a liquid on the test piece?

    On a microscopic level, even polished materials have a rough surface. This means that there will be tiny air cavities between the ultrasonic probe and the test piece which do not conduct the ultrasound. By applying a couplant (usually water, a water based gel or oil) we create a perfect sound conducting connection between the probe and the test piece. This guarantees interference-free test results.  

Henk Schroots

Area Sales Manager NDT & Laboratory

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