Phased array ultrasonic testing (PAUT) uses a probe made of many small elements that are pulsed with precise timing. That lets one probe sweep the beam through a range of angles, steer it along a line, or focus it at several depths, giving far more coverage and flexibility than a single fixed-angle probe, and an image of the result.
- Finds
- Weld flaws with position and depth data, complex-geometry defects, corrosion mapping
- Typical use
- Critical welds, limited-access geometry, inspections requiring recorded encoded data
What phased array inspection finds
Weld inspection
PAUT examines the whole weld volume for cracks, lack of fusion, incomplete penetration, slag and porosity, and records each indication with its position, length and depth. With an encoder on the scanner, the data is tied to position along the weld, so it can be reviewed, audited and compared later.
Corrosion mapping
Linear scanning over a surface builds a thickness map of a plate, pipe or vessel wall, showing the extent and depth of corrosion and erosion far more completely than spot thickness readings.
Sectorial and linear scans
A sectorial scan (S-scan) sweeps the beam through a range of refracted angles from one probe position, which suits welds and limited-access geometry. A linear scan (E-scan) steps a beam at a fixed angle along the probe, which suits corrosion mapping and fast coverage. Many weld inspections use both, with the setup and coverage planned in a scan plan before the job.
For many jobs conventional ultrasonic testing is enough. PAUT earns its place on critical welds, difficult geometry and jobs where the data has to be recorded.
Where it’s used
- Pressure vessel, piping and pipeline welds
- Oil and gas, chemical and petrochemical plants
- Power generation and nuclear components
- Structural and fabrication welds with limited access
- Corrosion mapping of vessels, tanks and piping in API in-service inspection
Codes and standards
- ASME Boiler and Pressure Vessel Code, Section V, Article 4, which covers phased array techniques for weld examination
- ASME Code Case 2235 and the corresponding Code provisions for using ultrasonic examination in place of radiography
- API 1104, for mechanized ultrasonic testing of pipeline welds
- ASTM E2700, contact ultrasonic testing of welds using phased arrays
- ASTM E2491, evaluating phased array instrument and system characteristics
- Customer and owner specifications
Who does the work
Every Midgard technician who performs phased array ultrasonic testing holds current certification in that method, issued under a written practice. For most industrial work the written practice follows ASNT’s SNT-TC-1A; for aerospace and defense work it follows NAS410. A Responsible Level III oversees the program: approving procedures and technique sheets, examining and certifying technicians, and answering the technical questions that come up on the job.
If your contract calls for a different scheme, such as ANSI/ASNT CP-189 or NAVSEA requirements, tell us when you ask for a quote.
Training in phased array ultrasonic testing
Midgard also trains in phased array ultrasonic testing, along with all the other major methods. Instruction is given at Level I, II and III by certified Level III instructors, to SNT-TC-1A, CP-189, NAS410, NAVSEA or whichever code you certify to, with general, specific and practical examinations at your facility or ours. It suits new hires working toward first certification as well as technicians due for re-examination. See training and certification, or ask about a class.
Common questions
What is the difference between phased array and conventional ultrasonic testing?
A conventional probe sends one beam at one fixed angle. A phased array probe steers, sweeps and focuses its beam electronically, so it covers more of the weld from each position, produces an image, and can record encoded data. Conventional UT is simpler and cheaper and is often all a job needs.
Can phased array replace radiography?
Often, where the code allows it. ASME and API 1104 have provisions for using ultrasonic examination instead of radiography on welds, subject to their requirements. PAUT involves no radiation, so there is no exclusion area and other work can continue.
What is a sectorial scan?
An S-scan sweeps the ultrasonic beam through a range of angles from one probe position and displays the result as a fan-shaped image of the cross-section. It suits welds and parts where the probe cannot be moved far.
What does PAUT corrosion mapping show?
A color-coded thickness map of the scanned area, showing where wall has been lost and how deep the loss is. Because the data is encoded, the same area can be scanned again later and compared.
Tell us the welds or area, the material and thickness, access, whether you need recorded data, and the code you work to. Call 1-844-MIDGARD, email contact@midgardscientific.com, or use the contact page.