December 4, 2018

TOFD

TOFD


TOFD is usually performed using longitudinal waves as the primary detection method. Ultrasonic sensors are placed on each side of the weld. One sensor sends the ultrasonic beam into the material and the other sensor receives reflected and diffracted ultrasound from anomalies and geometric reflectors. TOFD provides a wide area of coverage with a single beam by exploiting ultrasonic beam spread theory inside the wedge and the inspected material. When the beam comes in contact with the tip of a flaw, or crack, diffracted energy is cast in all directions. Measuring the time of flight of the diffracted beams enables accurate and reliable flaw detection and sizing, even if the crack is off-oriented to the initial beam direction. During typical TOFD inspections, A-scans are collected and used to create B-scan (side view) images of the weld. Analysis is done on the acquisition unit or in post-analysis software, positioning cursors to measure the length and through-wall height of flaws.

TOFD is usually

UT Quality Arabia Co. Ltd. has experienced in various applications of TOFD in oil and gas industries:

APPLIES TOFD

• To verify compliance with fabrication requirements for piping and vessels in accordance to standards such as:
• ASME Section I,
• Code Case 189,or
• ASME VIII Division 1 and 2.
• For in-service defect monitoring.
• For detecting defects during the manufacturing process.

ADVANTAGES

• High degree of repeatability
• Position and size data for every flaw can be compared for repeat scans of the same area to track flaw growth or corrosion rates both generally and for individual pits
• Not limited by defect orientation
• Precise defect sizing capability
• Sensitive to all kinds of defects
• Portable, battery operated testing device
• On-line, volume inspection
• Very fast scanning
• Set-up independent of weld configuration

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