Timeofflight diffraction measurement using laser ultrasound. Time of flight diffraction inspection for weld flaw detection and sizing initially the timeofflight diffraction technique tofd was developed as a method of accurately sizing and monitoring the throughwall height of inservice flaws in the nuclear industry. Tofd offers rapid weld inspection with excellent flaw detection and sizing capacities. Time of flight diffraction tofd ndt for weld inspection. Consistent results between pre and inservice inspection. Tf techniques applied to tofd for the automation of railt.
A project in the power generation industry was carried out on piping from 4 with a 6 mm wall thickness and more. Introduction to timeofflight diffraction tofd for weld. Pdf ultrasonic time of flight diffraction technique for. Tofd has now been independently validated as the most. Time of flight diffraction tofd systems use a pair of ultrasonic probes, sitting on opposite sides of a weldjoint or area of interest. The tofd technique is an advanced ultrasonic inspection technique that fulfils a need for reliable inspections. Tofd uses the time of flight of an ultrasonic pulse to. It is a powerful technique because it can simultaneously detect and size defects. A transmitter probe emits an ultrasonic pulse which is picked up by the receiver probe on the opposite side. Venkatraman and 1 durga karthik 1 department of cseit, src, sastra university. In many cases, this can be done with a single pair of probes.
Tofd technique requires analyzing the acquired image. Pressure wave ultrasound technique to identify damage and defects within welds on thick plate to quickly provide an accurate picture of weld integrity for in service inspection. Tofd is now routinely used in a wide range of applications such as inspection of piping and pressure vessels. Ultrasonic time of flight diffraction eclipse scientific. Time of flight diffraction inspection for weld flaw. The diffraction technique provides critical sizing capability with relative indifference to bevel angle or flaw orientation. By implementing tofd for the inspection of the root, before completion of the welds in heavy wall piping, costly repairs at the final stage were avoided. Advances in tofd inspection nondestructive testing. This requires consideration of several factors, some of which are interrelated. Ultrasonic time of flight diffraction technique for weld defects. Ultrasonic techniques are still the most popular nondestructive testing methods applied to problems such as the inspection of rail track. Tofd can be utilized on its own or in conjunction with other ndt techniques. The tofd technique is a fully computerized and automated system able to scan, store, and evaluate indications in terms of height, length, and position with a grade of accuracy never achieved by other ultrasonic techniques 4. The tofd operator needs to then position the tofd probe pairs in a way that ensures the area of concern is suitably ensonified.
Time of flight diffraction tofd is a reliable method of nondestructive ultrasonic testing ut used to look for flaws in welds. Tofd is usually applied to inspect the entire volume of a weld. The algorithm automatically recognizes the lateral wave within a predefined gate. The uttofd software provided with dasel equipments includes several digital processing algorithms that improve defects detection and sizing. When applied to metals the paut image shows a slice view that may reveal defects hidden inside a structure or weld.