Phased Array Ultrasonic Testing is an advance method of NDT examination utilizing multi-element probes, which are individually excited under computer control. The software enables the user to control focal law, beam steer and beam focus. Phased array probes may consist of a transducer assembly from 16 to as many as 256 small individual elements that can each be pulsed separately and may be arranged in a strip (linear array). Transducer frequencies are most commonly ranging from 2MHz to 10MHz.
A phased Array system will also include a sophisticated computer-based instrument that is capable of driving the multi-element probe, receiving and digitizing the returning echoes, and plotting that echo information in various standard formats.
Now, Phased Array Ultrasonic Testing is widely used in steel fabrication industries as an alternative method of testing in lieu of radiography testing for thick wall materials. NUSATEK has extensive experiences, expertise and equipment in providing this kind of services to the industries.
The advantage of using Phased Array Ultrasonic Testing are:
Ability to penetrate thick sections
Faster inspection rate
Ability to inspect many different materials
Image Data is recorded and saved
Phased Array Ultrasonic Testing
Phased Array Ultrasonic systems utilize multi-element probes, which are individually excited under electronic control. The PA probe consists of many small ultrasonic transducers, each of which can be pulsed independently and by exciting each element in a controlled manner, a focused beam of ultrasound can be generated. The beam of ultrasound can be steered electronically and can be swept like a searchlight through the metal or object being examined. In this way two and three dimensional views can be generated showing the sizes and locations of any flaws detected in a "slice" view through the object. Because the beam angle and focus can be controlled and manipulated, this method is very efficient in terms of speed and flaw detection.
Application of Phased Array:
Corrosion monitoring (Hydroform )
Tube sheet inspection (Cobra Scanner)
Phased Array is usually used for weldment integrity in fabrication, power plant, chemical plant, oil refineries and fabrication yard.
Advantages of Phased Array
Ability to use multiple elements to steer, focus and scan beams with a single transducer assembly.
Simplify the inspection of components with complex geometry
Ability to focus at multiple depths also improves the ability for sizing critical defects for volumetric inspections.
Data and image inspection can be recorded. Images can be either in A- scans, S-scan, C –scan or B-scan.
Application of Phased Array:
Weldment Inspection and Integrity
Phased Array testing is carried out to determine weldment integrity. Testing is usually carried out on joints, or accessible and inspection areas for vessels, piping, pipelines and plates. The movement of the phased array probe is controlled by the semi auto encoder and auto encoder. The function of the encoder is to record the data of the scanning area. The scanned area can be evaluated with its corresponding gain to the amplitude signal that is indicated in different colours on the screen. The recorded data is published in 3 types of images where C –scan is the view from top, S-scan is the Sectorial scan and A-scan is amplitude based. With this, interpreter can use software and data for analysis and determine any indication inside the weldment.
Normally the thickness of a product/component can be measured by using a thickness gauge or any other conventional method but, instead of that, we are now using a more advanced method which is Phased Array, where data is presented in A-scan, B-scan, and C-scan. Results obtained from the thickness measurement can be of help for corrosion monitoring purposes. The concept used is the same with weldment inspection except wedges are used in thickness measurement. Usually a 0 degree flat wedge and a longitudinal wave will be used to perform this inspection.
Corrosion Monitoring (Hydroform)
The HydroFORM™ is designed to offer the best inspection solution for the detection of wall-thickness reductions due to corrosion, abrasion, and erosion. Our solution also detects mid-wall damage such as hydrogen-induced blistering or manufacturing-induced laminations, and can easily differentiate these anomalies from loss of wall thickness.
The unique quick adjustment device offered by both scanners allows the wedge/probe assembly to be positioned to any curvature greater than 4 in. OD (101 mm).
HydroFORM utilizes an ingenious water-column concept that eliminates the need for a wedge, thus providing the benefits of a phased array immersion-tank inspection. This concept, which uses a low-flow water supply and consumable gaskets, offers excellent surface conformance and optimized coupling conditions, even on rough surfaces.
Tube Sheet Inspection (Cobra Scanner)
The COBRA™ manual scanner, combined with the OmniScan® PA flaw detector, is used to perform circumferential weld inspections on small-diameter pipes. The COBRA holds up to two PA probes for inspections on pipes with outside diameters ranging from 0.84 in. to 4.5 in.
With its very slim design, this manual scanner inspects pipes in limited access areas where minimal clearance is required. Adjacent obstructions, such as piping, supports, and structures, can be as close as 12 mm (0.5 in.). This spring-loaded scanner is designed to clasp carbon steel and stainless steel pipes of various diameters using multiple links. This unique feature enables the scanner to be installed and operated from one side of a row of pipes. The COBRA scanner is characterized by its smooth-rolling encoded movement, which enables precise data acquisition. The scanner holds up to two phased array probes for complete inspection of the weld in one pass. For pipe-to-component inspections, the scanner can be configured quickly to perform one-sided inspections using a single probe and combine probe used with a Y-adaptor.