CWI NDE Methods and Symbols 5

Question 1

On an NDE symbol, what does the flag symbol (a small filled triangle at the arrow-reference line junction) indicate?

Accepted Answer

Inspection is required in the field rather than in the shop

Answer

A filled triangular flag at the bend of the arrow indicates the NDE or welding operation is to be performed in the field at the erection site.

Question 2

What is 'acoustic impedance' in ultrasonic testing, and why is it important?

Accepted Answer

It is the product of material density and acoustic velocity; mismatches cause reflections at interfaces

Answer

Acoustic impedance (Z = ρv) determines how much sound is transmitted versus reflected at a boundary; large mismatches (like metal/air) cause near-total reflection.

Question 3

Which NDE method would be BEST suited to detect a lack-of-fusion defect in a thick-section weld when the defect may not be open to the surface?

Accepted Answer

Ultrasonic testing (UT)

Answer

UT can detect internal volumetric and planar defects such as lack of fusion because sound waves penetrate through the material and reflect from internal discontinuities.

Question 4

In radiographic testing, what is the effect of increasing the kilovoltage (kV) of an X-ray machine?

Accepted Answer

It increases penetrating power but decreases contrast

Answer

Higher kV increases the energy and penetrating power of X-rays, allowing thicker sections to be radiographed, but it reduces subject contrast making subtle thickness differences harder to distinguish.

Question 5

When performing MT using the yoke method, how do you verify the yoke's lifting power meets code requirements?

Accepted Answer

Lift a steel weight meeting the minimum specified mass (e.g., 10 lb for AC yokes per ASME)

Answer

ASME Section V requires AC yokes to lift at least 10 lb and DC yokes at least 40 lb to confirm adequate magnetic strength before use.

CWI Practice Test

CWI Practice Test

CWI NDE Methods and Symbols 5