TIME OF FLIGHT DIFFRACTION (TOFD) SERVICES

Time-of-Flight-Diffraction

NATTS TIME OF FLIGHT DIFFRACTION SERVICES

Time of flight diffraction is an advanced non-destructive testing method used for weld inspection.

Time of flight diffraction (TOFD) is among the most reliable nondestructive testing methods in testing welds for both pre-service and in-service inspection.

An accurate evaluation of welds is essential to make sure that defects don’t compromise the balance and integrity of welded structures.

This ultrasonic method can be used in a varied selection of industries including

  • petrochemical,
  • chemical,
  • Oil & gas
  • power generation and
  • fabrication

Calculating the amplitude of the reflected signal is usually a relatively unreliable approach to sizing defects because the amplitude strongly depends upon the orientation of the crack.

Instead of amplitude, TOFD uses enough time of flight of an ultrasonic pulse to look for the placement and size of a reflector.

In a TOFD program, a pair of ultrasonic probes sits on opposite sides of a weld. Among the probes, the transmitter, emits an ultrasonic pulse that’s found by the probe, on the other hand, the receiver.

In undamaged pipes, the signals detected by the receiver probe are from two waves: One that travels along the surface and one that reflects off the far wall.  When a crack is present, there is diffraction of the ultrasonic wave from the tips(s) of the crack.

Using the measured time of flight of the pulse, the depth of crack tips could be calculated automatically by basic trigonometry.

THE ADVANTAGES OF TIME OF FLIGHT DIFFRACTION INCLUDE

Can take place during creation work - zero shutdown is required

Zero radiation with this technique

Inspection data is recorded and may end up being stored digitally for potential reference

Inspection results are immediately available

Quick inspection method

Sensitivity to all or any weld flaw types including cracks, slag and insufficient fusion

Accurate sizing of defects

FEATURES

A computerised and automated program for weld inspection

Compared to conventional ways of ultrasonic testing, TOFD is delicate to cracks and steps their dimensions accurately.

TOFD has two blind zones where it isn't sensitive to defects. Therefore TOFD ought usually to end up being supplemented by a typical pulse-echo study of the close to and far walls. The pulse-echo probes are generally mounted on a single buggy as the TOFD probes. Requires ultrasound technicians with advanced training

Probes are mounted on a buggy that travels along a weld, recording data since it moves.

NATIONAL ACADEMY FOR TRAINING AND TECHNICAL SERVICES
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