Phased Array Ultrasonic Testing is one of the advanced methods of non-destructive ultrasonic testing, which is called PAUT for short and sometimes it is also called 3D UT.

In this method, probes that have a large number of piezoelectric crystals are used. The appropriate timing for sending the pulse of each of the crystals is determined by the computer of the device and finally the Phased Array waves are produced.

1. History of PAUT

1.1. PA technology entered the industry in the 1980s. And in the mid-80s, with the development of piezo composites, the production of complex probes became possible. At the beginning of the 90s, PA technology was included in the NDT Handbook as a new technology.

The most important works done by this emerging technology in the interval between 1985 and 1992 are related to pressure vessels of atomic industries, large forged shafts and components of low pressure turbines.

PA technology reached commercial status in 1992, when a portable device was used by one person in the workshop and found the ability to transfer information, and in 2003, the first new generation devices entered the market.

Currently, reputable companies such as Sonatest and Olympus are updating and developing new equipment.

 

2. Getting to know the test method

In this method, like the usual ultrasonic method, ultrasonic waves are used to diagnose and inspect defects, with the difference that in this method, multi-element probes are replaced by single-element probes, and electronic scanning is used instead of mechanical scanning, which leads to a reduction in inspection time. And the test range is recorded.

Several piezoelectrics arranged with a special pattern in a chamber are called an array or ARRAY, which has 3 main modes: LINEAR, MATRIX, or ANNULAR. Arranged elements are usually small and flat.

 

In this method, to produce waves with different angles or to focus the wave at a specific point according to the law of interference of waves, a specific time delay is considered for connecting the current to each crystal, which leads to the angle taken or focus of the wave, which is called PHASED It is called ARRAY.

 

2.1. Types of scans

2.1.1. ELECTRONIC SCANNING:

The ability to move a sound wave along the arrangement of elements without mechanical movement is called electronic scanning.

This scan is limited to the number of elements and the number of channels in the processor system.

 

2.1.2. SECTORIAL SCANNING:

In this case, the wave bundle is propagated by changing the rules of the focal point and the delay time in a range of angles and the elements remain unchanged.

 

2.1.3. LINEAR SCANNING:

In this case, the waves propagate at an angle and the elements remain unchanged.

 

2.2. Types of views that can be registered in PAUT

A-SCAN

It is a view of receiving the intensity of ultrasound pulses with different sending or returning times. This view only represents the path taken by the sound.

 

Top view

It is a two-dimensional view of the stored ultrasound information that displays the width axis of the part and the length axis.

Side view

It is a two-dimensional view of the stored ultrasound information that displays the part’s width axis and depth axis.

End View

It is a two-dimensional view of the stored ultrasound information that displays the length axis of the part and the depth axis of the part

 

Sonatest Veo Phased Array Image

 

2.3. PHASED ARRAY scanning methods

2.3.1. Automated Motorized Scanning

In this method, after setting the settings and moving distance, the scanning is done automatically by the scanning equipment without the intervention of the operator.

 

2.3.2. Semi-Automated Scanning

In this method, the probes and encoder are placed on a scanner with appropriate distances of the test piece in a straight line and at an appropriate distance in terms of covering the weld volume, and with the movement of the scanner by the driving force of the operator, sound wave information is recorded based on the elapsed time. and is suitable for PA and TOFD methods

 

 

2.3.3. Manual Encoded Scanning method

With the movement of the probe and encoder, the sound wave information is recorded by the operator based on the distance traveled.

 

2.3.4. Manual Free Run Scanning method

In this method, the information obtained during the test is checked and the welding length information is not saved.

3. Applications

3.1. welding test

3.1.1. Welding on thick sections

Considering the limitation of radiographic sources to low thicknesses and the ability to penetrate high sound and the possibility of using more elements in the PAUT method, it is also possible to inspect very thick parts.

It should be noted that as the thickness of the piece increases, the sensitivity of the radiographic test decreases, but in the PAUT method, increasing the thickness has no negative effect on the sensitivity of the test.

 

3.1.2. Welding pipes

Currently, with the development of new equipment, it is possible to test pipes of any size and thickness.

 

3.1.3. Reservoir testing

Considering the widespread use of the ASME standard in Iran and the adoption of advanced ultrasonics instead of radiography in this standard, as well as the ability to test thick parts and the possibility of testing during the working hours of the workshop, this method has quickly replaced the usual methods.

One of the most important advantages is the possibility of testing repair parts immediately after repair, which has a significant impact on the speed of project progress.

 

3.2. Corrosion

3.2.1. Corrosion measurement of tanks and pipelines

Currently, corrosion measurement is one of the most widely used applications of PAUT method.

Corrosion measurement is done by various methods. Among these methods, the following can be mentioned:

Scanning sensitive points and recording images of corrosion points
Scanning all areas and recording the image of corrosion points
Scanning all areas and recording images by advanced scanners

3.3. Testing parts

Different methods can be used to control the health of products

Production used.

 

4. Comparison with other methods

4.1. Permanent document:

According to the desire of the respected employers to have a document that can be controlled by their inspectors, this method is practical compared to radiography, and in addition to the document that can be checked, all test steps and settings can also be controlled.
Each scan file is separate and cannot be changed.
Instead of using the movie archive, you can archive the files as a CD.
Inspectors can reinterpret the total weld length to match the results presented.