The ultrasonic testing method is applicable to almost all materials. The ultrasonic method uses the transmission of mechanical energy in wave form at frequency above the audible range. Reflections of this energy by discontinuities in metals are detected in a manner somewhat analogous to the detection of reflected light waves in transparent media.
Advantages of Ultrasonic testing
- The method can be used to detect both surface and subsurface discontinuities.
- For pulse-echo angle beam testing, access is necessary to only one side of the work (i.e Testing of TKY tubular joints in jacket, deck, boat landing and bridge fabrication, lifting pad eyes, lugs and trunnions, girth/long seam welds in jacket legs, braces, piles, conductors, deck framing, butt welds in process piping, plate and beam splices etc.)
- The size of flaws and their and their interface location may be measured quantitatively.
Ultrasonic testing limitations
The size of the flaws and their interface location may be measured quantitatively.
- Welds in some materials are very difficult to examine ultrasonically. For example, welds involving materials and process which produce large grain size (i.e Stainless Steel, Duplex, Inconel) tend to scatter and disperse the sound beam; penetration of the sound beam into these materials is limited and interpretation of the results can be difficult.
- Personnel must be qualified and in general, they require more training and experience for ultrasonic examination than for the other common examination methods.
- The scan pattern must be sufficient to pass the projected sound beam through the entire volume of the weld and heat-affected zone to permit detection of possible discontinuities.
- The test surface for scanning with the transducer must be smooth so liquid coupling may be obtained, or the part must be immersed in a liquid.