NDT Discontinuity Interpretation and Evaluation 3

Question 1

An ASME code requires that any linear indication greater than 3/16 inch in a weld be rejected. A PT indication measures 3/16 inch exactly. The correct disposition is:

Accepted Answer

Accept — it does not exceed the limit

Answer

The code specifies 'greater than' 3/16 inch, so an indication exactly at 3/16 inch is acceptable under that criterion.

Question 2

During UT inspection, multiple small signals appear scattered throughout the weld volume with low amplitude. The most likely cause is:

Accepted Answer

Distributed porosity

Answer

Scattered low-amplitude signals throughout the volume are characteristic of distributed porosity, where each pore produces a small reflection.

Question 3

A radiographic image shows a dark, irregular line with a herringbone or chevron pattern along the weld centerline. This pattern is associated with:

Accepted Answer

Solidification (hot) cracking

Answer

Solidification cracks form along weld centerlines during cooling and often display a jagged or herringbone pattern following dendritic grain boundaries.

Question 4

In magnetic particle testing, a broad fuzzy linear indication is observed. Compared to a sharp, crisp indication, this suggests the discontinuity is:

Accepted Answer

Deeper below the surface

Answer

Subsurface discontinuities cause broader, less defined magnetic particle indications because the leakage flux spreads as it reaches the surface.

Question 5

An eddy current scan of a heat exchanger tube shows a signal whose depth reading is 80% through-wall. Per most fitness-for-service criteria, this tube should be:

Accepted Answer

Plugged or repaired immediately

Answer

Most industry standards (ASME, TEMA) require plugging or repair of heat exchanger tubes when wall loss reaches or exceeds 40–80% depending on code; 80% typically requires immediate action.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Discontinuity Interpretation and Evaluation 3