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Ultrasonic Testing

Ultrasonic Testing

We are qualified to offer the following to PCN Level 2

  • Ultrasonic Testing of Welds 3.1 Plate, 3.2 Pipes, 3.7 T Butts and Cruciforms, 3.8 Nozzles and 3.9 Node welds.
  • Ultrasonic Testing of Forgings
  • Ultrasonic Testing of Castings

We also hold PCN Level 3 Ultrasonic Testing of Welds.

Ultrasonic Testing, What is it?

Ultrasonic Testing (UT) is a category of non-destructive testing (NDT) that applies high frequency sound waves to objects to detect flaws like cracking or to make measurements such as checking for density or thickness. Many plastics, ceramics, metals, woods, composites and concrete products can be tested or measured using this method, including plated items and alloys. One example application of this testing method is to measure the level of corrosion on a pipe. Ultrasonic testing is also commonly used to test the integrity of welds.

An ultrasonic sensor (sometimes also referred to as an ultrasonic transducer) is passed over an object that is separated from the sensor by a ā€œcouplant,ā€ most often a liquid (like oil, glycerin or water, as in immersion testing) that helps transfer the sound waves from the sensor to the test object. Without the couplant, the sound waves would not penetrate the object enough to render the testing successful. (When an Electromagnetic Acoustic Transducer is used, however, there is no need for a couplant.) Sometimes the couplant will have a rust inhibitor added to prevent damage to metal parts.

The ultrasonic sensor is attached to a diagnostic machine or interface for recording and displaying the results. The sound waves pass through the test object; however, these waves reflect back at any point where there is a flaw or a discontinuity in the surface of the item. These reflected sound waves help inspectors pinpoint the size and location of flaws and defects. A modification of this technique is to use both a transducer and a receiver (sometimes also called a pulser) to detect sound waves as they pass through an object from one side to the other. Any imperfections or defects in the object will reduce the amount of sound waves that pass through it. The travel time of the signal also conveys information about the density of the object being tested. The diagnostic device displays the resulting amplitude and data points so a technician can interpret the results.

Small objects can easily be tested this way in a laboratory or clean room environment, but ultrasonic testing can also be conducted out in the field. Sometimes when the item being tested is in service and hot to the touch, such as a pipe or a boiler that cannot be temporarily shut down during an inspection, special transducers that tolerate extreme temperatures will be required. Ultrasonic testing is often used in places like power plants and manufacturing facilities to gauge the depth of corrosion, which can lead to premature equipment failure if not monitored and controlled properly.

When it comes to defect detection, some of the types of flaws that can be detected with ultrasonic testing include cracks, porosity, laminations/delaminations, inclusions, and more. Weld and bond integrity can also be determined with ultrasonic testing.

Some of the advantages of ultrasonic testing include a high degree of accuracy when it comes to the size and shape of discontinuities and flaws; the ability to locate both surface and sub-surface defects; instant results displayed on the diagnostic device; and better depth of object penetration, as compared to other NDT methodologies.

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