How the quiz works
Each set serves all 18 questions in a shuffled order, with the options shuffled too. Check your answer and the explanation tells you why the right option is right and why each of the other three is wrong.
Your score is one point per question, out of 18. At the end you see your misses by area (which method finds it, surface and volumetric reach, material limits, basic principles, and choosing the method), so you know what to study next. Hit New shuffle for a fresh order. Use the set number if you report an error.
Worked examples
Example 1: a surface crack on stainless steel
Step 1: the material is austenitic stainless steel, which is not ferromagnetic, so MT is out. Step 2: the crack is at the surface, so a surface method will do. Step 3: PT works on almost any nonporous material and finds flaws open to the surface. The answer is PT.
Example 2: porosity inside a groove weld
Step 1: the flaw is buried, so PT and VT are out. Step 2: MT reaches only just below the surface, so it is out too. Step 3: porosity has volume, which is what radiography shows best, and the image is a permanent record. The answer is RT, with UT as the other volumetric method.
NDE methods compared: the reference set
Read the table, then go back and beat your score.
| Method | What it finds | Limits and needs |
|---|---|---|
| VT | Surface only; the cheapest and quickest, and usually the first examination | Any material, with good light and a clean surface |
| PT | Flaws open to the surface; fails on a flaw with no opening | Almost any nonporous material, including stainless steel and aluminum |
| MT | Flaws at the surface and just below it; most sensitive to flaws across the field | Ferromagnetic material only |
| RT | Volumetric flaws such as porosity and slag; can miss planar flaws not lined up with the beam | Usually both sides; radiation controls; permanent image |
| UT | Planar flaws such as cracks and lack of fusion, with depth information | One side; couplant; skilled operator; coarse-grained welds are difficult |
| ET | Surface and near-surface flaws; common on tubing | The material must conduct electricity |
This is a study summary, not a rule. Want the flaws themselves? Try the weld discontinuities quiz and read weld discontinuities explained. For recall drills across all of Part A, use the CWI Part A flashcards.
NDE methods FAQ
Which NDE method finds flaws below the surface?
RT and UT look inside the weld, so they are the volumetric methods. RT is best on porosity and slag, and UT is best on planar flaws such as cracks and lack of fusion. MT reaches only just below the surface. PT and VT see only what is open or visible at the surface.
Why does MT not work on stainless steel or aluminum?
MT depends on magnetizing the part so that a flaw leaks magnetic flux that gathers iron particles. Austenitic stainless steel and aluminum are not ferromagnetic, so there is no field to disturb. PT does not depend on magnetism, so a surface crack on those metals points to PT.
What is the difference between a surface method and a volumetric method?
A surface method finds flaws open to the surface (PT) or at and just below it (MT). A volumetric method looks through the thickness of the weld (RT and UT). A clean result from a surface method says nothing about a buried flaw, which is why a scenario question usually turns on where the flaw is and what shape it has.