NDT.net - September 1999, Vol. 4 No. 9

TOFD - the emerging ultrasonic computerized technique, for heavy wall Pressure Vessel welds examination

F. Betti, A. Guidi, B. Raffarta - NUM PIGNONE - Massa (Italy)
G.Nardoni, P. Nardoni, D. Nardoni - I&T Brescia (Italy)
L. Nottingham - Structural Integrity - U.S.A
Corresponding Author Contact:
Email: nardoni@numerica.it - Web: http://www.nardoni.it



Fundamentals of the TOFD technique

TOFD norms

TOFD Applications

Physical principle of TOFD

Configuration of system

Fig 5: Block diagram of TOFD ultrasonic computerized system.
Fig 5a: The TOFD system in its practical aspect.

Scanning plan

Scanning direction

Fig 7a: - Scanning direction - parallel to the weld axis.
Fig: 7b - Scanning direction - perpendicular to the weld axis to improve sizing accuracy of indication.

Real time acquisition and records

Fig 8: B-Scan image in real time create and visualize on PC during the scanning of 1 meter length weld and 135 mm (5.3 inch.) of thickness.

Image evaluation

Fig 9: Normal Tube Support Plate Responses in Differential and Absolute Modes

Experiences on examination of welds

Fig 10: Lack of fusion not detected by radiography test and clearly displayed on the TOFD map. Thickness of weld 120 mm (4.7 inc.).
Fig 11: Small defects not clearly identified with standard pulse echo technique are clearly represented on TOFD map. Thickness of weld 183 mm (7.2 inc.) Step of weld represented 1 m (39 inc.)
Fig 12: The TOFD map shows elongated lack of fusion at different deeps clustered with isolated slag inclusions. Thickness of weld 13 1 min (5. 1 inc.) Step of weld represented 1 m (39 inc.)
Fig 13: The TOFD map shows clustered slag inclusions located near the root of weld. Thickness of weld 131 mm (5.1 inc.) Step of weld represented 1 m (39 inc.)
Fig 14: TOFD map of a cladded test block of 170 mm (6.7 inch) thickness with overlay weld. The TOFD map shows on the left a strong lateral waves, through the thickness the three holes and before the backwall an "interference" image like a transparency which represents the cladded layer.



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/DB:Article /AU:Nardoni /AU:et al /CN:IT /CT:UT /CT:tofd /ED:1999-09