Fabrication welds
Examining welds where geometry and access permit the required probe arrangement and scan coverage.
TIME OF FLIGHT DIFFRACTION (TOFD)
TOFD inspection for weld examination and indication sizing.
Time of Flight Diffraction records the travel time of sound waves diffracted from discontinuity tips. It can support detection and through-wall sizing in suitable welds when the scan setup and procedure are matched to the component.
Request a TOFD proposalHOW THE METHOD WORKS
Time of Flight Diffraction (TOFD)
A transmitting probe sends an ultrasonic beam across the weld while a receiving probe collects the signals. A typical TOFD record includes the lateral wave, back-wall reflection and, when present, signals diffracted from relevant discontinuities. Encoded movement along the weld produces a position-linked data record for interpretation.
WHERE IT MAY HELP
Potential inspection applications
In-service weld assessment
Collecting data to support investigation of relevant indications in accessible components.
Indication sizing
Using diffracted signals to estimate through-wall extent when signal quality and procedure allow it.
Applications are illustrative. Suitability depends on the component and approved inspection procedure.
SCOPE DEVELOPMENT
Information needed for a TOFD enquiry
Send available drawings or specifications with the details below. IAIS can use them to review coverage, calibration, site arrangements and reporting requirements.
01
Weld drawing, joint profile and nominal wall thickness
02
Material and surface condition on both sides of the weld
03
Required scan length, access and any obstructions
04
Applicable code, acceptance criteria and reference block requirements
TECHNICAL CONSIDERATIONS
Limits and complementary methods
TOFD can have reduced sensitivity close to the scanning surface and back wall. Complex geometry, attenuation, access and noise can affect interpretation. A complementary technique such as PAUT may be considered where the approved inspection plan requires it.
PROJECT ENQUIRY
Discuss the inspection objective.
Share component drawings, applicable code or specification, location and schedule. The team will review the technical basis before proposing a method and execution plan.