About Advanced Ultrasonic Testing
Advanced Ultrasonic Testing (AUT) is both a generic term which relates to the computerized collection of ultrasonic data and, specifically, to the ultrasonic inspection of a pipe girth welds. Advanced Ultrasonic Testing systems use two sets of ultrasonic probes scanned circumferentially on either side of the weld. The sets of probes are selected to provide coverage of specific zones of the weld and the fusion face. Advanced Ultrasonic Testing is used for pipe girth welds and can inspect the whole volume of a weld with a good controlled level. It can be used in combination with most common UT flaw detectors. The data collection can either be manual and/or automated and usually is triggered by an encoder. Our advanced ultrasonic testing specialists offer both ways of data collection dependent upon your request and specification. If additional techniques such as eddy-current testing (ET) or visual testing (VT) are used, then we define this as mechanized scanning.
DEKRA uses advanced ultrasonic testing methods for periodical and non-periodical industrial inspections in all sort of industries, both conventional and nuclear, where pipe welds need to be inspected according to a norm with an ultrasonic method.
DEKRA offers a wide range of advanced ultrasonic testing methods, including:
- Phased array ultrasonic testing - commonly used advanced ultrasonic testing method
- Time-of-flight-diffraction to detect cracks or flaws in a weld connection
- Guided Wave Ultrasonic Testing to rapidly screen long pipes and for detect corrosion
- IRIS ultrasonic testing – the back-up to verify calibration and accuracy
- Electromagnetic acoustic transducers to test magnetic or metallic materials
Phased Array Ultrasonic Testing
Phased Array Ultrasonic Testing (UT) is the name given to a special type of ultrasonic probe and belongs to the family of advanced ultrasonic testing techniques. The technology uses arrays of ultrasonic beams that are computer-controlled and steered electronically. An array is a group of transmitters, receivers or transmitter/receivers, generally called array elements.
The ability to change the beam shape and the angle, in combination with sophisticated data and software imaging to generate A, B and C- and S-scan of the inspected component, means that a highly accurate interpretation of the resulting data is possible. This advanced ultrasonic testing method is both fast and highly efficient at defect detection due to multiple simultaneous sound beams (angles).
Phased array ultrasonic testing is one of the most widely-used advanced ultrasonic testing methods. DEKRA uses phased array ultrasonic testing across all oil, gas, power and chemical industrial sectors to detect discontinuities such as cracks or flaws and to determine component quality. In addition to detecting flaws in components, phased array is also used for wall thickness measurements.
Typical applications of Phased Array UT at DEKRA are:
- Weld inspection to detect cracks or flaws in pipe welds
- Corrosion mapping to detect cold HIC (Heat introduced cracking)
Time-of-Flight Diffraction (TOFD) Ultrasonic Testing
Time-of-Flight Diffraction (TOFD) is an ultrasonic technique which measures the time of flight of a pulse as it travels from a transmitting probe to a receiving probe and belongs to the family of advanced ultrasonic testing techniques. It is necessary to scan a pair of time-of-flight-diffraction probes over the flaw for the technique to function correctly and divergent beams are used.
Time-of-flight-diffraction time measurements can be done with great accuracy. Which, combined with the fact that the scattering source is the flaw tip, forms the basis of a highly accurate sizing technique. It can detect planar defects and cracks not perpendicular to the measured surface. The defect height can also be exactly determined and the high probability of detection (POD) associated with this method greatly improves risk reduction and calculation accuracy.
Time-of-flight-diffraction is a widely used advanced ultrasonic testing method, at DEKRA to detect cracks or flaws and size them in welds.
Typical applications of time-of-flight-diffraction at DEKRA are:
- Welds in the oil, gas and power sectors
- Additional detection and sizing method for primary system welds in the nuclear sector
- Inspection of end caps of generators
Guided Wave Ultrasonic Testing
Guided wave ultrasonic testing uses low frequency ultrasonic waves that are transmitted along the pipes under inspection. This advanced ultrasonic testing technique is designed for rapid screening of long pipes, and for detection of external and internal corrosion.
The guides wave ultrasonic testing method is a fast and efficient way to test the full circumference of the pipe. Buried pipes, insulated pipes, pipes through foundations and other hard-to-access pipes are able to be inspected for both external and internal cross-sectional change. The guided wave ultrasonic testing method can also be used during operation on media filled pipes.
The guided wave ultrasonic testing equipment used at DEKRA consists of three main components: the transducer ring, the instrument (Wave Maker G4) and the computer for data collection. The transducer rings use mechanical or pneumatic pressure (depending on the ring) to push the transducers to the pipe (dry coupling). The transducer transmits waves along the cross section of the pipe. When an area with increased or decreased cross-sectional change is passed, they reflect as an echo with a magnitude representing the decrease or increase itself. Both long pipes and hard-to-access pipes are easily inspected, including pipe-racks, buried pipes under roads, insulated pipes, pipes in foundations and submerged pipes.
Internal Rotary Inspection System (IRIS) Ultrasonic Testing
Internal Rotary Inspection System (IRIS) is an ultrasonic method for the non-destructive testing of pipes and tubes. Because IRIS is an ultrasonic technique, it requires a couplant. In this case, water. Therefore, the internal rotary inspection system probe is inserted into a tube that is flooded with water, with the probe then pulled out slowly as the data is displayed and recorded.
Field-proven and commonly used in boilers, heat exchangers, and fin-fan tubes. The ultrasonic beam allows the detection of metal loss from both the inside and outside of the tube wall. The method produces highly accurate results, with wall thickness measurements typically accurate to within 0.15mm.
DEKRA’s inspection teams can deliver IRIS combined with other tube inspection techniques. Internal rotary inspection system is highly sensitive to cleanliness, which is something that can be compensated with different testing methods.
Electromagnetic Acoustic Transducers (EMAT) Ultrasonic Testing
Electromagnetic Acoustic Transducers (EMAT) is a common ultrasonic testing method limited to magnetic materials that is both ideal for inspections at temperatures below the freezing point and above the usual operating temperature for piezoelectric probes. Electromagnetic acoustic transducers ultrasonic testing is less sensitive to surface conditions, with the only requirement being the removal of loose particles.
The most common application of electromagnetic acoustic transducers testing is in thickness measurement. With different transducer configurations fast corrosion screening can be supplied, similar to the guided wave ultrasonic testing method, but with less range.