Nondestructive Testing Methods & Techniques Flashcards

What NDT method uses high-frequency sound waves transmitted through a couplant to detect internal flaws?

Answer: Ultrasonic testing

Ultrasonic testing (UT) transmits high-frequency sound waves (typically 1–10 MHz) through a liquid couplant into the material to detect reflections from internal discontinuities.

During a hydrostatic pressure test, what is the primary hazard compared to a pneumatic pressure test?

Answer: Pneumatic tests are more dangerous because compressed gas stores significantly more energy than liquid

Pneumatic tests using compressed gas store far more elastic energy than hydrostatic tests using liquid; a catastrophic failure in a pneumatic test releases energy explosively, making it significantly more hazardous.

In eddy current testing, what effect does a crack or void in a conductive material have on the eddy current flow?

Answer: It forces eddy currents to flow around the discontinuity, changing the impedance signal

Discontinuities interrupt the normal circular eddy current paths, forcing currents to reroute, which alters the coil impedance and produces a detectable signal change.

Which document typically establishes the specific acceptance criteria that a boilermaker NDT inspector must apply when evaluating weld indications?

Answer: The applicable construction or inspection code (e.g., ASME Section VIII)

Acceptance criteria for weld indications in pressure vessels are defined by the governing construction or inspection code, such as ASME Boiler and Pressure Vessel Code Section VIII.

What is 'signal-to-noise ratio' in the context of ultrasonic testing?

Answer: The ratio of the flaw signal amplitude to the background noise level

Signal-to-noise ratio (SNR) compares the amplitude of the relevant flaw indication to the background noise; a high SNR makes it easier to distinguish real defects from material noise.

When performing liquid penetrant testing on a rough, as-welded surface, what precaution is most important?

Answer: Ensure thorough pre-cleaning to remove weld spatter and contaminants from the surface

Rough as-welded surfaces trap contaminants that can mask discontinuities or cause false indications; thorough pre-cleaning is essential for reliable PT results.

In magnetic particle testing, the 'circular magnetization' technique is best suited to detect:

Answer: Longitudinal (lengthwise) discontinuities parallel to the current flow

Circular magnetization produces a magnetic field perpendicular to the current flow direction, making it most sensitive to longitudinal discontinuities that run parallel to the current path.