Time-Of-Flight Diffraction (TOFD) method of ultrasonic testing is a sensitive and accurate method for the nondestructive testing of welds for defects. TOFD originated from tip diffraction technique.
Time-Of-Flight Diffraction (TOFD) method of ultrasonic testing is a sensitive and accurate method for the nondestructive testing of welds for defects. TOFD originated from tip diffraction technique.
TOFD is usually performed using longitudinal waves as the primary detection method. Ultrasonic probes are placed on each side of the weld. One probe sends the ultrasonic beam into the material and the other probe 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 intial 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 can be used independently or in conjunction with other ultrasonic techniques. Some of the most common techniques are:
• Single group TOFD
• Multiple TOFD
• TOFD with pulse echo/creeping waves
• TOFD with phased array
APPLICATION
TOFD is commonly used to inspect vessel, exchanger Circumferential and longitudinal weld Inspection and Phased array and TOFD combination for pipeline welds.
ADVANTAGES
• Based on diffraction, so relatively indifferent to weld bevel angles and flaw orientation
• Uses time of arrival of signals received from crack tips for accurate defect positioning and sizing
• Precise sizing capability makes it an ideal flaw monitoring method
• Quick to set up and perform an inspection, as a single beam offers a large area of coverage
• Rapid scanning with imaging and full data recording
• Highly sensitive to all weld flaw types
“Our Specialized Inspection Divisions is fully equipped with latest data acquisition equipment’s and highly skilled/trained Operators to undertake any stringent job configurations.”
PHASED ARRAY
Phased array provides high speed electronic scanning and improved inspection capabilities through a software control, with a beam characteristic inspection in multiple angles with a single electronically controlled probe in which many configuration and greater flexibility for inspection of complex geometries. PA produces detailed cross sectional pictures of internal structures which will help the inspector in great extent to size up and differentiate the internal defects.
CORROSION MAPPING
Internal corrosion in static equipments are common phenomenons were the occurrence of corrosion is inevitable. The most important step is to clearly identify the type, size and root cause, of corrosion to avoid unexpected failures and accidence.
Automatic encoded C-Scan technique provides a very sensitive and reliable data to detect and monitor the static equipments in oil and gas sector.
We are an early investor in Automated Ultrasonic Testing (TOFD, PA, C-Scan) by procuring our first equipment in 2001. Our AUT Teams are highly qualified and experienced in all type of A, B, C Scans to identify the different type of Corrosion flaws.
