Time of Flight Diffraction is used for variety of applications, being the primary use is rapid weld testing of circumferential and axial weld seams, also known as perpendicular TOFD scanning. TOFD is performed using longitudinal waves as the primary detection method through the ultrasonic sensors that are placed on each side of the weld. One sensor sends the ultrasonic beam into the material and the other sensor receives reflected and diffracted ultrasound from anomalies and geometric reflectors.
Using ultrasonic beam spread, TOFD provides wide area of coverage for anomaly detection in the material being tested. When the beam comes in contact with a tip of flaw, or crack, diffracted energy is cast in all directions. Measurements of the time of flight of this diffracted beam enables accurate and reliable flaw detection and sizing. This is the case even if the crack is not oriented to the initial beam direction. During typical TOFD inspections, A-Scan are collected and used to create B-Scan (Side View) images of the weld. Post-acquisition analysis is done using software to measure the flaw length and through-wall height.
Advantages of TOFD over conventional Ultrasonic Testing are; 1) Based on diffraction, so relatively indifferent to weld bevel angles and flaw orientation. 2) Uses time of arrival of signals received from crack tips for accurate defect positioning and sizing. 3) Quick to set up and perform an inspection, as single beam offers a large area of coverage. 4) Rapid scanning with imaging and full data recording. 5) Can also be used for detecting irregularly shaped areas of metal loss during corrosion inspections. 6) Required equipment is more economical than phased array, due to conventional nature and use of probes. 7) Highly Sensitive to all weld flaw types.
IXAR professionals are highly trained and experienced in TOFD ultrasonic testing for various core industrial sectors. Our expertise in using the state-of-the art equipment such as Olympus Omniscan MX2 has allowed us to perform specific testing in: a) Inspection of high pressure and high temperature pipe welds on circumferential and seams weld between 20mm to 75mm wall thickness. b) Sizing of known defects has been performed all around country on pipeline welding, high pressure vessels. A generated analysis report outlining the sizing of defects can be provided to the client for their reference.