Ultrasonic Inspection is a commonly used method of inspection with a wide range of applications. These include but are not limited to thickness checking, corrosion mapping and monitoring, volumetric weld inspection, lamination, inclusion and void detection.
Conventional manual ultrasonics comprises of an ultrasonic search unit and transducer connected via either a twin or single lead. The transducers can be of varying angles and frequency.
The most common frequency range being 0.5MHz through to 15MHz. The angles of a transducer can be made to suit a specific application. The most commonly used angles are 0⁰, 45⁰, 60⁰ and 70⁰. The 0⁰ transducer has a mode of propagation called compression or longitudinal wave, while the 45⁰, 60⁰ and 70⁰ all produce shear waves into the test medium. The mode of propagation depends upon the refracted angle of the sound wave entering into the test medium.
The search unit applies an electronic pulse to the piezo-electric transducer which then vibrates. This vibration displaces molecules which in turn creates a sound wave. The sound wave will travel through the object under test reflecting off the internal surfaces until the sound energy has dissipated.
Sound waves travel at different velocities within different materials. Knowing the material velocity and the time it takes the sound wave to travel from the transducer through the test material and back to the transducer. We can calculate the thickness of the test material.
Using the angled transducers, we send sound waves into the parent material as well as the weld volume. We will receive geometric responses from the cap and root regions of the weld. We are looking for any deviation from these signals.
A shortening of the root signal (lack of root penetration, root crack, root undercut).
An Increase in the root signal (excess root penetration)
A signal that appears within the weld volume (pore)
A signal from the side wall (lack of side wall fusion)
Using the appropriate transducer, the sound wave is introduced to the test medium. We are looking for any indications that cannot be attributed to the geometry of the item under test.
There are different methods of applying the Ultrasonic sound wave to the object under inspection. The most common way is by using a coupling medium between the probe and object to remove any air gaps. This allows the sound to pass back and forth between the probe and object under inspection.
Another method is by using an immersion bath. An immersion bath is essentially a bath containing water, or a special anti-corrosion liquid depending upon the specific requirements of the contract. This method ensures constant coupling of the probe and inspection object. It can also be made into an automated process with pre-programmed scanning patterns that can be recorded for offline interpretation and documentation. This system is very well suited for high volumes of inspection.
All of these techniques and more can be used on a wide range of materials from carbon steels, stainless steels, plastics and composite materials to name a few. This opens up a wide range of sectors that Conventional Ultrasonics can be utilised in, power generation, oil and gas, petrochemical, pharmaceutical, aerospace and many more.
There are numerous ways of utilising Ultrasonic inspection and its many flexible combinations of ultrasonic search units and transducers. From run of the mill thickness checks through to bespoke high integrity inspection plan. Ensuring that the correct technique is utilised is of the utmost importance. If you would like any further information to help build an inspection plan or for technical advice please do not hesitate in contacting ITCL.
As an addition to Conventional Ultrasonic Inspection we can also offer advanced ultrasonic inspection, namely Manual Phased Array and Time of Flight Diffraction. These advanced methods of ultrasonics add a plethora of advantages to conventional ultrasonics. These methods can be used as a sole inspection method or can be combined to create a very thorough inspection.
For more information on Manual Phased Array and Time of Flight Diffraction please have a look at their respective pages.
Here at ITCl we pride ourselves on the high quality of application and testing by our experienced technicians. Our workforce is fully qualified to current standards and work to approved procedures and control checks. Environmental and health & safety issues are of paramount concern to all staff working on your site, with expert consultation always available.
ITCL offers a comprehensive 24hr in-house and on-site service.
Contact a member of the ITCL team on 0151 356 7118 for more information.