Phased Array for weld inspection and crack detection are the most common applications. These tests are done across a wide range of industries including oil and gas, petrochemical plants, power generation and chemical industries, especially for the construction of new piping, pipelines, vessels and structural welded materials. Phased Array can also be effectively used to profile remaining wall thickness in corrosion survey applications when surface condition and part geometry allows.
A Phased Array probe is composed of several small ultrasonic elements which are individually pulsed. By phasing the pulses across the array of elements, the ultrasonic beam can be steered and focused as needed for a particular application. Multiple beams can be generated for a single examination; therefore, a variety of beams can examine the area of interest thoroughly.
Applications for Phased Array Ultrasonic Testing (PAUT):
Volumetric inspection of forging or casting materials
Mapping Erosion and corrosion activity
Flaws that Phased Array can detect:
Weld flaws such as lack of fusion, slag inclusions, porosity, connection of surface and/or embedded cracks, and incomplete penetration
Erosion or corrosion – material loss, pitting, and root erosion
Inherent discontinuities in forged or casting materials such as laminations, forging bursts, cavity defects, cold shuts, hot cracking and inclusions
Environmentally or process induced damage such as Microbiologically-Influenced Corrosion (MIC), Hydrogen Induced Cracking (HIC), thermal fatigue cracking, caustic cracking and stress corrosion cracking
There are a multitude of phased array benefits due to its universal capability to perform so many inspection tasks. Here are some advantages of Phased Array:
Information can be displayed in multiple display formats (examples below), which aid in discontinuities/ flaw detection.
A-Scan displays the amount of received ultrasonic energy as a function of time
B-Scan displays a profile view (cross-sectional) of a specimen
C-Scan displays a plan type view of the specimen & discontinuities
S-Scan displays an end view of the specimen at the current position of the probe
The data can also be captured and stored for inspector review. This also makes future reference and inspections easier.
The replayed data can be processed and displayed in various ways using the instrument used to acquire the data or on analysis software that provides additional processing capabilities.
Limitations of Phased Array:
Accessibility to a clean smooth surface
Material of piece being scanned. Course grained materials and exotic alloys can attenuate Phased Array UT energy the same way it will attenuate conventional UT energy and cause limitations to the inspection.