# Ultrasonic testing (UT)

> Ultrasonic testing (UT) sends high-frequency sound pulses into a material and analyses the echoes to detect internal discontinuities, measure thickness and size flaws.

- Source: https://amps.global/glossary/ultrasonic-testing/
- Type: Glossary
- Published: 2026-09-05
- Updated: 2026-09-10
- Tags: NDT, ultrasonic testing

## Key facts

- Typical frequencies 0.5 to 20 MHz; a couplant (gel, oil, water) is needed between probe and surface
- Straight-beam probes for laminations and thickness, angle-beam (shear wave) probes for welds
- Instrument checks such as horizontal and vertical linearity are required by ASME V; AMPS offers a free calculator
- Weld UT codes: ASME BPVC Section V Article 4, ISO 17640, AWS D1.1 Clause 8 (formerly 6)

Also known as: UT, ultrasonic inspection, ultrasonic examination.

## How it works

A transducer converts an electrical pulse into a sound wave that travels through the part. Reflections from the back wall and from discontinuities return to the probe and are displayed as an A-scan: amplitude against time of flight. Knowing the sound velocity in the material turns time into distance, so a technician can locate and size a reflector and measure remaining wall thickness.

Calibration is done on reference blocks (IIW V1 and V2 blocks, step wedges, blocks with side-drilled holes) before each job, and instruments are periodically checked for horizontal and vertical linearity, screen height linearity and amplitude control linearity as required by ASME V.

## Where it is used

Weld examination on pressure vessels, piping and structural steel, corrosion and erosion monitoring through thickness gauging, laminations in plate, castings and forgings, and bond quality. UT is portable, gives immediate results and, unlike radiography, has no radiation safety constraints, which is why phased array UT increasingly replaces RT for welds.

## UT in AMPS

In AMPS, reports are produced from your own Microsoft Word templates through the template engine: job data such as the client, purchase order number, equipment serial numbers, location and dates is filled in automatically, an AI assistant can tidy the wording, the report can be signed in AMPS, and the finished Word file is saved in the job's report folder in your OneDrive, SharePoint or Google Drive. Equipment calibration records for flaw detectors, probes and reference blocks sit on the equipment page with expiry flags. AMPS also publishes a free horizontal and vertical linearity tool based on ASME V.

## Related pages

- [Free UT linearity tool (ASME V)](https://amps.global/ndt-tools/linearity/)
- [Horizontal linearity](https://amps.global/glossary/horizontal-linearity/)
- [Vertical linearity](https://amps.global/glossary/vertical-linearity/)
- [Phased array UT (PAUT)](https://amps.global/glossary/phased-array-ultrasonic-testing/)
- [Ultrasonic thickness gauging](https://amps.global/glossary/ultrasonic-thickness-gauging/)
- [ASME BPVC Section V](https://amps.global/glossary/asme-bpvc-section-v/)

## Sources

- [Ultrasonic testing on Wikipedia](https://en.wikipedia.org/wiki/Ultrasonic_testing)
- [ASME Boiler and Pressure Vessel Code](https://www.asme.org/codes-standards/bpvc-standards)
- [ASNT - American Society for Nondestructive Testing](https://www.asnt.org/)