Major limitations of ultrasonic testing

Major limitations of ultrasonic testing are:

• Surface must be accessible
• Skill training is more extensive that with some other methods
• Normally requires couplant to promote sound transfer
• Surface roughness, complex geometries, small parts or exceptionally thin materials are difficult to inspect
• Coarse grained materials i.e. cast iron are difficult to inspect due to low sound transmission and high signal noise
• Linear defects oriented parallel to the sound beam go undetected
• Reference standards are required for equipment calibration
• Some kinds of noise like hissing and flow noice can throw the detector off
• austenitic steel because of large grain size is very troublesome