M2M Gekko PAUT Phased Array Instrument z TFM, UT, TOFD (2023) (2023)

FAQs

What is the difference between UT and TOFD? ›

In practice, testing with the TOFD method is only applied by continuously moving the probe pair along the weld seam, while in traditional UT techniques the probe must be also moved perpendicular to the weld seam. Depending on the equipment the scan is performed either manually or by use of an automated manipulator.

While PAUT uses reflection, TOFD uses diffraction. The transducer produces pulsed ultrasonic waves, which are diffracted to various degrees by irregularities in the scanned material, then collected on the material's far side by a receiver.

Phased Array is an ultrasonic testing technique that uses specialized multi-element “array” transducers and pulses those elements separately in a patterned sequence called “phasing”. This phasing sequence allows wave steering, focusing, and scanning. This is all performed electronically.

A PAUT transducer uses multiple elements during a scan. Beams are emitted sequentially at multiple angles allowing PAUT to create a more detailed scan. Other UT methods, on the other hand, use a single probe to analyze an asset. By emitting multiple beams, PAUT allows for the inspection of even the most complex assets.

Generally speaking, on the premise of meeting the requirements of flaw detection sensitivity, the probe with lower frequency shall be selected as far as possible; for forgings, rolled parts and weldments with finer grain, the probe with higher frequency shall be selected, usually 2.5-5.0mhz.

A disadvantage of TOFD is that the gain must be very high, which produces a very high back wall echo and it is not suitable for coarse grained materials. There is a dead zone for defect detection under the surface. It means, defects close to the surface could not be detected.

Principle of operation

In a TOFD system, a pair of ultrasonic probes sits on opposite sides of a weld. One of the probes, the transmitter, emits an ultrasonic pulse that is picked up by the probe on the other side, the receiver.

As is the case with conventional transducers, phased array probes may be designed for direct contact use, as part of an angle beam assembly with a wedge, or for immersion use with sound coupling through a water path. Transducer frequencies are most commonly in the range from 2 MHz to 10 MHz.

The advantages of phased array ultrasonic testing (PAUT) include faster scans, a higher probability of detecting flaws and anomalies and the best possibility of performing an inspection. The PAUT method of non-destructive testing uses multiple beams to scan an asset.

PAUT improves weld testing performance over single-probe ultrasonic testing and other NDT methods. Choosing the right ultrasonic testing equipment can increase efficiency, improve test reliability, and provide company managers the peace of mind of knowing that their welds will hold.

What is the minimum thickness for PAUT? ›

25 mm (1.0 in.).

Summary of the Discussion of TFM vs PAUT

The principal advantage of TFM is that the entire image is displayed with focused amplitude, compared to an image produced with PAUT, which is only highly resolved in the focal area of the beam.

There will be four significant types of ultrasound transducers — linear probes, curvilinear probes, phased array probes, and endocavitary probes.

TOFD uses the time of flight of an ultrasonic pulse to find the location of a reflector. It can also be used for weld overlays and the heat affected zones of other components as well such as piping, pressure vessels, clad material, storage tanks, and structural steel.

The lateral wave is simply the compression wave travelling parallel to the flat surface. If it is assumed to be travelling parallel to the flat surface (between the Tx and Rx probes) its refracted angle is therefore 90°.

A single TOFD setup is limited to a maximum thickness of about 30 - 40 mm. For thicker components, two zones with two PCS are used. They are called upper and lower TOFD zones. As the component gets thicker lower frequency probes such as 5 MHz 6 mm diameter are used for the lower zone.

TOFD – Time-of-Flight Diffraction – is an ultrasonic technique which measures the time of flight of a pulse as it travels from a transmitting probe to a receiving probe. Divergent beams are used and it is necessary to scan the TOFD probe pair over the flaw for the technique to function correctly.

Mode conversion occurs when a wave encounters an interface between materials of different acoustic impedances and the incident angle is not normal to the interface. It should be noted that mode conversion occurs every time a wave encounters an interface at an angle.

What are the 2 types of phased array antenna? ›

The three types of phased array antennas are 1) linear array, 2) planar array, and 3) frequency scanning array.

Applications of Loop Antenna

Aircraft direction finders. In radio receivers for receiving high-frequency waves. Loop antennas are also used as ultra-high frequency transmitters. In RFID devices, to detect the position of the transmitter.

Phased Array Ultrasonic Testing (PAUT), also known as phased array UT, is an advanced non-destructive inspection technique that uses a set of ultrasonic testing (UT) probes made up of numerous small elements.

Most ultrasonic testing is available within 400 kHz to 25 MHz. These vibrations are beyond the audible range and propagate in the test material as waves of particle vibrations. Sound beams of all frequencies can penetrate fine-grained material without difficulty.

Sounds with a frequency of 20 kHz and higher are referred to as ultrasound (or ultrasonic sound). High frequency sound is sound of which the frequency lies between 8 and 20 kHz.

Disadvantages of Phased Array Ultrasound Testing

While PAUT has a wide range of abilities, it's not a preferred testing method for the detection of surface cracks, metal fatigue, or bolt hole inspections compared to eddy current testing.

The main disadvantages of phased-array systems are that (i) they are more expensive to purchase, (ii) operation and data interpretation are more difficult and (iii) there can be greater difficulty in achieving good ultrasonic coupling due to the larger probe dimensions.

Phased array transducers are used for various NDT inspections, including: Tube inspection, where multiple probes are often used to detect cracks, find laminar flaws, and measure overall thickness.

What is one of the advantages of ultrasonic inspection in relation to radiographic testing? ›

There is no radiation hazard in ultrasonic examination, and hence no disruption of work as there is with radiography. Volumetric and crack like defects can be detected, irrespective of their orientation.

They can provide a larger depth of field than single-element transducers because of their dynamic focusing capability, and require fewer elements to form an image than linear-sequenced or linear-phased arrays [7].

Time of Flight Diffraction (TOFD) is a reliable method of nondestructive ultrasonic testing (UT) used to look for flaws in welds. TOFD uses the time of flight of an ultrasonic pulse to find the location of a reflector.

Advantages of ToFD

ToFD is a single pass operation, not amplitude dependent and very accurate for sizing of vertical defects. The technique is found to be substantially more accurate in sizing the height of defects than conventional pulse echo techniques, which are based on echo amplitude.

Time of flight diffraction is an advanced non-destructive testing method used for weld inspection. Time of flight diffraction (TOFD) is one of the most reliable non-destructive testing methods in testing welds for both pre-service and in-service inspection.

One of the major limitations of this method is the near-surface dead zone. The large pulse width of the lateral wave masks any signals from near-surface flaws and produces a near-surface dead zone. This dead zone limits detectability of flaws just below the weld cap. Typically, the dead zone can be 4 mm to 8 mm deep.

Basic principle of TOFD. The most significant distinction between TOFD and the other UT methods is that it monitors only forward-scattered diffracted energies from the tips of defects rather than reflected ultrasonic energies. Two wide beam angle probes are used in transmitter-receiver mode.

Ultrasonic testing can be performed using two basic methods – pulse-echo and through-transmission.

Several wave modes of vibration are used in ultrasonic inspection. The most common are longitudinal, shear, and Rayleigh (surface) waves. Ultrasonic waves are very similar to light waves in that they can be reflected, refracted, and focused.

Maurice Silk had invented the TOFD in the late 1970's [13]. TOFD System: The TOFD technique is a fully computerized and automated system able to scan, store, and evaluate indications in terms of height, length, and position with a grade of accuracy never achieved by other ultrasonic techniques [4].

What is time of flight diffraction equipment? ›

In time-of-flight diffraction (ToFD) systems, a pair of ultrasonic probes are used, sitting on opposite sides of a weld-joint or area of interest. A transmitter probe emits an ultrasonic pulse which is picked up by the receiver probe on the opposite side.