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§3.2 · Judging the weld

NDE test methods for the CWI

Ultrasonic weld testing, radiography, magnetic particle and penetrant each see a different slice of a weld, and the CWI's NDE domain is about matching method to material and flaw. You won't run the equipment, but you do need the principle behind each step: couplant, dwell time, image quality.

Exam
CWI
Clause
§3.2
Tags here
16
Part A minimum
at least 8%

3.2.1Method against flaw location

Open to surfaceJust belowsurfacePlanar, insideVolumetric,insidePT penetrantMain useNoNoNoMT magnetic particleMain useCan showNoNoUT ultrasonicCan showCan showMain useCan showRT radiographyCan showCan showIf lined upMain use
Highlighted cells are each method's home ground. RT finds planar flaws only when they line up with the beam.

3.2.2Three questions that pick the method

Weld NDT, as plenty of shops still call it, gets picked the same way every time. Three questions, asked in order, settle most method picks.

  1. What's the part made of? MT works only on ferromagnetic metal, so it's out on austenitic stainless and aluminum. PT works on any nonporous material.
  2. Where's the flaw? Open to the surface, PT or MT. Buried, UT or RT. The MT vs PT page covers the surface pair.
  3. What shape is it? Flat, planar flaws like cracks and lack of fusion suit UT, which also gives depth. Rounded, volumetric ones like porosity and slag suit RT. The RT vs UT page works through that choice.

Orientation decides more answers than the method name. A magnetic field has to cut across a crack to show it. A sound beam returns most from a flaw it hits square. A radiograph shows a crack well only when the crack runs parallel to the beam.

Reading a film or a report

On a radiograph, less metal in the beam path images darker, so gas pores and slag show dark. Tungsten inclusions are the exception: they're denser than steel and show light. That's why porosity is a radiography favorite on the exam. Eddy current (ET) rounds out the list as an electromagnetic method; expect it as a principle to recognize.

The CWI usually reads NDE results rather than producing them, and the NDE welding symbol on the drawing tells everyone which joints get which method (welding and NDE symbols). If you want hands-on MT or PT on your card, AWS offers separate endorsements for dry powder yoke MT and Type II Method C PT (AWS CWI page, checked October 2026); see CWI endorsements.

Ultrasonic weld inspection in the code

UT acceptance in D1.1 Clause 8 is split by loading: statically and cyclically loaded connections each have their own criteria. An answer that's right for a building column can be wrong for a crane runway girder, so read the loading in the stem before you read the options.

UT also earns its keep before welding starts. A lamination is a flat mill defect inside rolled plate, and a straight-beam scan finds it before anyone welds on top of it. Lamellar tearing looks similar on a report but it's caused by the weld; the difference matters when you write up where the flaw came from.

Phased array weld inspection (PAUT) is UT with many small elements fired in sequence, so the beam can be steered and focused electronically and the result displayed as a picture of the weld section. D1.1 has carried it as an annex since 2020. For the exam it's still ultrasonic testing, with the same strengths on planar flaws.

3.2.3Four methods side by side

What each method needs and gives you
PointPTMTUTRT
MaterialAny nonporousFerromagnetic onlyMost metalsAny
Access neededThe surfaceThe surfaceOne sideBoth sides: source and film or detector
Flaw it suitsSurface-breakingSurface and near-surfacePlanar, with depthVolumetric
What you keepPhoto or sketch of indicationsPhoto or sketch of indicationsReport of signals and positionsFilm or digital image
Tells you depthNoNoYesNo

≠ marks a row where at least one of them differs.

Visual examination comes before all four and has its own Part A domain: visual examination and discontinuities.

3.2.4Method-matching drill

Eddy current turns up here alongside the four main methods. Commit to one answer before anything opens.

0 of 16 tagged · 0 accepted

  1. Tag 01

    What is the primary purpose of using a penetrameter in radiographic testing?

    Remarks on every option
    1. A The film is protected by its cassette and screens, not by the penetrameter.
    2. B The penetrameter doesn't calibrate the source. It shows what the finished image can resolve.
    3. C Correct: A penetrameter (IQI) shows the radiograph has the required sensitivity. If the required hole or wire doesn't show, the film isn't acceptable.
    4. D The IQI is picked based on thickness, but it isn't a thickness gauge.

    Pick an option. The remarks on all 4 open here.

  2. Tag 02

    In radiographic testing, what does the term 'film density' refer to?

    Remarks on every option
    1. A Film weight has nothing to do with density. Density is how dark the image is.
    2. B Film size is chosen to cover the area of interest. It isn't density.
    3. C Emulsion thickness affects film speed and grain, but density is the darkness of the processed image.
    4. D Correct: Film density is the degree of blackening on the processed film, read with a densitometer. Less material in the beam path shows darker.

    Pick an option. The remarks on all 4 open here.

  3. Tag 03

    In radiographic testing, what causes geometric unsharpness?

    Remarks on every option
    1. A Material density changes how much radiation gets through (contrast), not how sharp the edges are.
    2. B Film grain causes graininess, a different thing from geometric unsharpness.
    3. C Correct: Geometric unsharpness comes from source size and the source-to-object and object-to-film distances. A smaller source farther away gives sharper edges.
    4. D Processing time and temperature affect density and fog, not geometric unsharpness.

    Pick an option. The remarks on all 4 open here.

  4. Tag 04

    What type of radiation source is most commonly used in portable radiographic testing equipment?

    Remarks on every option
    1. A Cobalt-60 is for thick steel. Its high energy and heavy shielding make it less common for portable work.
    2. B Correct: Iridium-192 is the workhorse isotope for portable field radiography of welds in common steel thicknesses.
    3. C Cesium-137 isn't a common choice for industrial weld radiography.
    4. D Selenium-75 is used on thinner sections, but it's less common than Ir-192.

    Pick an option. The remarks on all 4 open here.

  5. Tag 05

    What is the primary advantage of digital radiography over conventional film radiography?

    Remarks on every option
    1. A Some digital systems need less exposure, but that isn't the main advantage.
    2. B Digital equipment usually costs more up front than film.
    3. C Film still generally matches or beats digital detectors on fine resolution.
    4. D Correct: The image is ready right away. No chemical processing, so you can review and re-shoot faster.

    Pick an option. The remarks on all 4 open here.

  6. Tag 06

    What is the primary function of a coupling medium in ultrasonic testing?

    Remarks on every option
    1. A Couplant does let the probe slide, but that's not why it's there. Surface prep is its own step.
    2. B A contrast background belongs to MT and PT. UT reads a screen, not marks on the surface.
    3. C Correct: Couplant fills the air gap between probe and part. Air reflects almost all the sound, so without couplant nothing gets in.
    4. D Damping is done by the backing material inside the transducer, not by the couplant.

    Pick an option. The remarks on all 4 open here.

  7. Tag 07

    When using ultrasonics, what does 'dead zone' refer to?

    Remarks on every option
    1. A The strongest echoes aren't the dead zone. The dead zone sits near the surface, where the initial pulse hides reflections.
    2. B Running out of penetration is attenuation, not the dead zone. The dead zone is right under the probe.
    3. C Correct: Right under the probe, the initial pulse and ring-down mask any echo, so very shallow flaws can't be seen.
    4. D Poor coupling causes signal loss anywhere on the scan. It isn't the dead zone.

    Pick an option. The remarks on all 4 open here.

  8. Tag 08

    What is the purpose of a calibration block in ultrasonic testing?

    Remarks on every option
    1. A Correct: A calibration block with known reflectors lets you set range and sensitivity and confirm the instrument and probe work right.
    2. B Readings go in the inspection report. The block is a physical reference, not storage.
    3. C Wear plates or shoes protect the probe. The block is a reference standard.
    4. D Cleaning is housekeeping. The block exists for setting range and sensitivity.

    Pick an option. The remarks on all 4 open here.

  9. Tag 09

    When performing ultrasonic testing, what causes beam spreading?

    Remarks on every option
    1. A Higher frequency gives a narrower beam with less spread.
    2. B Rough surfaces scatter sound and hurt coupling, but beam spread is set by frequency and probe size.
    3. C Correct: Lower frequency, and a smaller probe diameter, give more beam spread in the far field.
    4. D Thicker material gives the beam more distance to spread over, but it doesn't cause the spread.

    Pick an option. The remarks on all 4 open here.

  10. Tag 10

    What type of light source is typically used for examining fluorescent penetrant indications?

    Remarks on every option
    1. A White light is for visible (color-contrast) penetrant, not fluorescent.
    2. B Correct: Fluorescent penetrant glows under UV-A (black light), viewed in a darkened area.
    3. C LED is just the lamp type. What matters is UV-A output; a white LED won't make the dye glow.
    4. D Infrared doesn't excite fluorescent dyes.

    Pick an option. The remarks on all 4 open here.

  11. Tag 11

    What is the purpose of a penetrant dwell time in liquid penetrant testing?

    Remarks on every option
    1. A Correct: Dwell time gives the penetrant time to soak into surface-breaking discontinuities before the excess is removed.
    2. B Drying is a separate step. Dwell is the time the penetrant sits on the part.
    3. C That's development time, after the excess penetrant is removed and developer is applied.
    4. D Pre-cleaning happens before the penetrant goes on. Dwell starts after it's applied.

    Pick an option. The remarks on all 4 open here.

  12. Tag 12

    What is the minimum surface cleanliness requirement before performing penetrant testing?

    Remarks on every option
    1. A Correct: The surface must be clean and dry, free of anything that could keep penetrant out of an opening.
    2. B Rust can fill and hide openings. It has to come off.
    3. C Paint seals over discontinuities, so the penetrant can't get in.
    4. D Oil fills the openings and contaminates the penetrant.

    Pick an option. The remarks on all 4 open here.

  13. Tag 13

    What is the purpose of using fluorescent magnetic particles instead of visible particles in MT?

    Remarks on every option
    1. A Correct: Under UV-A, fluorescent particles glow against a dark background, so fine indications are easier to see.
    2. B Fluorescent MT needs a darkened area and a UV lamp. Setup is more involved, not less.
    3. C Fluorescent particles and UV lamps cost more than visible dry powder.
    4. D Particle type doesn't change detection depth. MT finds surface and near-surface flaws, and current type sets the depth.

    Pick an option. The remarks on all 4 open here.

  14. Tag 14

    What is the primary advantage of using alternating current in magnetic particle testing?

    Remarks on every option
    1. A Subsurface flaws are DC's strength. The AC field stays near the surface.
    2. B The skin effect keeps an AC field shallow. Deeper penetration comes from DC.
    3. C Correct: The skin effect concentrates the AC field at the surface, which makes AC the better pick for surface-breaking cracks.
    4. D Power draw isn't why you pick AC. Surface sensitivity is.

    Pick an option. The remarks on all 4 open here.

  15. Tag 15

    What is the primary limitation of eddy current testing?

    Remarks on every option
    1. A Eddy current is fast and easy to automate. Speed is one of its strengths.
    2. B Eddy current works by electromagnetic induction. No ionizing radiation is involved.
    3. C Correct: Eddy current needs an electrically conductive part to induce currents in, so nonconductive materials can't be tested.
    4. D Cost isn't the defining limit. The basic limit is that the part has to conduct electricity.

    Pick an option. The remarks on all 4 open here.

  16. Tag 16

    What type of discontinuity is best detected using the eddy current method?

    Remarks on every option
    1. A Buried inclusions are mostly out of reach. Eddy current is strongest at the surface.
    2. B Correct: Eddy current is most sensitive to surface and near-surface flaws like cracks.
    3. C Internal porosity is a volumetric flaw. RT is the usual tool for it.
    4. D Lack of fusion is usually buried in the joint. UT is the typical method.

    Pick an option. The remarks on all 4 open here.

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