Why TOFD is the Most Accurate of all NDT Inspection Techniques
TOFD better known as Time of Flight Diffraction is one of the most trusted and widely used non-destructive testing methods. TOFD proved really useful and handy for in-service as well as pre-service inspection. Determining flawless assessment of welds is extremely vital in order to ensure top-class integrity and stability of welded structures. No other NDT method even come closer with TOFD when it comes to assess the health of a welded structure. It can be utilized independently along with other ultrasonic techniques.
Time of flight diffraction provides brilliant accuracy in measuring the critical through-wall size of crack-like-defects. The crack tips depth and defects can be easily calculated by utilizing the measured time of flight of the pulse in TOFD method. Nowadays, advanced NDT inspection method in Singapore is the preferred technique used in industries.
Some of the most common TOFD techniques are:
TOFD with pulse echo/creeping waves
Single group TOFD
TOFD with phased array
Multiple TOFD
The Basic Theory of TOFD
TOFD inspection is generally performed by employing two longitudinal waves as the primary detection method. The L-wave angle beam transducers arranged symmetrically opposite facing each other, straddling the weld or base material under test. One sensor releases ultrasonic beam into the material and the other sensor receives reflected and diffracted ultrasound from anomalies and geometric reflectors. A position encoder records the position of the weld and produces the real time digital image of the flaw. In the industry of replacement projects and the life cycle of new build, time of flight diffraction technique can save huge amount of time.
Areas of TOFD Application
Nozzle inspection
Root corrosion detection in piping vessels
Construction weld inspections
High temperature weld inspections of up to nearly 500°C
In service inspection at ambient or high temperatures
Inter granular stress corrosion cracking in welds
Examination of steam drums used in power generation
For the instant determination of weld quality, no other technique can come closer with TOFD. It is fast, reliable and cost-effective non-destructive testing method.