Inspection method · UT
Ultrasonic testing (UT)
Sound waves reveal what the eye cannot: internal flaws in welds, forgings, castings and plate, and remaining wall thickness.
01How it works
Ultrasonic testing introduces high frequency sound into the material through a probe and a couplant. Reflections from discontinuities or the back wall are received and displayed. Conventional pulse echo UT uses single element probes at fixed angles; phased array UT (PAUT) steers beams electronically and produces images; time of flight diffraction (TOFD) uses diffracted signals from flaw tips for accurate sizing.
Results depend on calibration on reference blocks, probe selection, scanning coverage and the evaluation method defined in the procedure.
02Typical industrial applications
- Butt and T-joint welds in plate and pipe
- Forgings and shafts
- Plate lamination checks
- Castings with suitable geometry
- Wall thickness measurement
- Bolts and pins
03Benefits and what it detects
- Detects planar flaws such as lack of fusion and cracks
- No radiation hazard
- Immediate results on site
- Depth and size information
- Suitable for thick sections
04Limitations
- Requires skilled, certified operators
- Coarse grained materials (austenitic welds, some castings) are difficult
- Complex geometry and thin sections limit coverage
- Conventional UT gives limited permanent record
- Surface condition and couplant affect results
05Specifying and reviewing the method
Specify the method standard, testing level or technique class, extent of testing, timing relative to heat treatment and acceptance levels. For welds the ISO 17640 series and ISO 11666 are commonly used; for forgings EN 10228-3 or ASTM A388.
Other references: ISO 17640, ISO 11666, ISO 13588 (PAUT), ISO 10863 (TOFD), EN 10228-3
06QUALITAS TR role
Frequently asked questions
UT or RT for welds?
UT is better at planar flaws such as lack of fusion and cracks and at thick sections; RT is better at volumetric flaws such as porosity and slag and gives a permanent image. Codes often allow either; critical joints may need both.