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CWI Test Methods: NDE practice questions

Principles, uses and limits of visual, penetrant, magnetic particle, radiographic, ultrasonic, eddy current and leak testing. This domain is about 10% of the exam. Try each question, then open the answer.

Read the Test Methods: NDE study guide

Question 1

What is the correct order of the main steps in a solvent-removable visible penetrant test?
  1. Preclean, apply penetrant, dwell, remove excess, apply developer, inspect, postclean
  2. Apply developer, apply penetrant, dwell, remove excess, inspect
  3. Preclean, apply developer, apply penetrant, inspect, remove excess
  4. Apply penetrant, inspect immediately, preclean, apply developer
Show answer

Answer: A. Preclean, apply penetrant, dwell, remove excess, apply developer, inspect, postclean

The surface must be clean and dry so penetrant can enter openings. After the dwell time, excess penetrant is removed carefully so it is not pulled from discontinuities. Then a thin developer coat draws penetrant out to form indications.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (penetrant testing procedure); ASME BPVC Section V, Article 6

Question 2

For best detection with MT, how should the magnetic field be oriented relative to the discontinuity?
  1. Parallel to the discontinuity
  2. At about 45 degrees to the discontinuity
  3. Orientation does not matter
  4. Perpendicular to the discontinuity
Show answer

Answer: D. Perpendicular to the discontinuity

A discontinuity is easiest to find when it cuts across the lines of magnetic flux, producing leakage that attracts particles. Inspections are done in two directions about 90 degrees apart so cracks in any direction are found.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (magnetic particle testing); ASME BPVC Section V, Article 7

Question 3

On a radiograph of a steel weld, how does a tungsten inclusion appear?
  1. A dark area (higher film density), because tungsten lets more radiation through
  2. A light area (lower film density), because tungsten absorbs more radiation
  3. A dark straight line along the weld center
  4. It does not appear on radiographs
Show answer

Answer: B. A light area (lower film density), because tungsten absorbs more radiation

On film, areas that let more radiation through are darker (higher film density). Voids such as porosity are dark. Tungsten is denser than steel and blocks more radiation, so it appears lighter (lower film density) than the surrounding weld.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (radiographic interpretation); AWS Welding Inspection Handbook, 4th ed.

Question 4

Radiography is best at detecting which type of discontinuity?
  1. Tight planar cracks at any angle to the beam
  2. Volumetric discontinuities such as porosity and slag
  3. Laminations parallel to the plate surface
  4. Surface hardness changes
Show answer

Answer: B. Volumetric discontinuities such as porosity and slag

RT detects changes in material thickness or density along the beam path. Porosity and slag change that thickness noticeably. Cracks and lack of fusion are detected only when they lie close to the beam direction.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (radiographic testing, advantages and limits)

Question 5

Which condition makes conventional UT of welds most difficult?
  1. Coarse-grained austenitic stainless steel weld metal
  2. Fine-grained carbon steel plate with a uniform structure
  3. A smooth, ground weld surface
  4. A thick section of 2 in.
Show answer

Answer: A. Coarse-grained austenitic stainless steel weld metal

Coarse, directional grains in austenitic weld metal scatter and bend sound, producing noise and false signals. Thin sections, rough surfaces and complex geometry also make UT harder.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (ultrasonic testing, limitations)

Question 6

What does acoustic emission testing detect?
  1. Reflections of sound sent into the part by a transducer and timed on a screen
  2. Stress waves released by growing discontinuities under load
  3. Changes in magnetic flux at the surface
  4. Penetrant bleed-out
Show answer

Answer: B. Stress waves released by growing discontinuities under load

AE uses sensors to listen for energy released when discontinuities grow or materials deform under load, such as during a pressure test. It finds active flaws but does not size them precisely.

Source: AWS B1.10M/B1.10, Guide for the Nondestructive Examination of Welds (acoustic emission testing)

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