Ultrasonic thickness testing is used to determine the remaining plate thickness and also the integrity of steel, aluminium, general metal vessels, plates and pipe work. While the process is non-destructive, physical contact with the surface is required.
Advancements in technology have removed the need for surface preparation and a reading can now be taken through a painted surface. The ultrasonic thickness report is a separate detailed report and includes diagrams that indicate where the readings were taken and the current state of the component. These reading can then be used for trending over time or compared against set standards to identify the remaining life or wear rates within the system.
There are two methods of receiving the ultrasound waveform, reflection and attenuation. In reflection (or pulse-echo) mode, the transducer performs both the sending and the receiving of the pulsed waves as the "sound" is reflected back to the device. Reflected ultrasound comes from an interface, such as the back wall of the object or from an imperfection within the object. The diagnostic machine displays these results in the form of a signal with an amplitude representing the intensity of the reflection and the distance, representing the arrival time of the reflection.
In attenuation (or through-transmission) mode, a transmitter sends ultrasound through one surface. A separate receiver will detect the amount that has reached it on another surface after traveling through the medium. Imperfections or other conditions in the space between the transmitter and receiver reduce the amount of sound transmitted, revealing their presence.
Using the couplant increases the efficiency of the process by reducing the losses in the ultrasonic wave energy due to the separation between the surfaces.
High-penetrating power which allows the detection of defects deep within the part
High-sensitivity which permits the detection of extremely small failings
Only one surface needs to be accessible
Greater accuracy than other non-destructive methods in determining the depth of internal flaws and the thickness of parts with a parallel surface
Some capability of estimating the size, orientation, shape and nature of defects
Non-hazardous to operations or to nearby personnel, also has no effect on equipment and materials in the vicinity
Capable of portable or highly automated operation