INTRODUCTION & BASIC INFORMATION
Time of Flight Diffraction (TOFD) is a reliable and fastest method of nondestructive ultrasonic testing (UT) used to look for flaws in welds. TOFD uses the time of flight of an ultrasonic pulse to find the location of a reflector. It can also be used for weld overlays and the heat affected zones of other components as well such as piping, pressure vessels, clad material, storage tanks and structural steel. PAUT + TOFD combination is commonly used to inspect pipeline welds. To do this, TOFD uses a pair of ultrasonic transducers, one as a transmitter and the other as a receiver. The low frequency waves propagate at an angle and only diffract back to the receiver if they hit a defect. If this happens, the time it takes for both waves to make it to the receiver can be used to create a complete image of the weld and identify the size and location of the damage. Advantages are, high degree of repeatability, no radiation, higher POD, cost saving, more sensitive, Quick setup, precise sizing.
APPLICATION
TOFD is widely used in Oil & gas Industry, nuclear, (Refinery’s, Petrochemicals of piping, pressure vessels, clad material, In-service weld inspection)