Liquid Penetrant Level II: 15 Practice Questions, Answered From the Code

How to use these fifteen questions

Each question states a situation, gives the correct answer, then explains the clause or the chemistry that makes it correct. Answer before you read on. A penetrant exam is unusually easy to pass by memorising numbers and unusually easy to fail by memorising the wrong ones, because the method has four different time windows, two different light regimes and three removal routes, and they look alike on a revision card. Reasoning separates them. If you can explain why the hydrophilic pre-rinse is capped at one minute, you will never confuse it with a dwell time.

The paragraph numbers are ASME Boiler and Pressure Vessel Code Section V, Article 6, 2019 Edition and later. That edition replaced the term black light with UV-A light throughout, inserted paragraphs covering LED sources, and corrected the metric conversions so that 100 fc reads 1076 lx and 2 fc reads 21.5 lx. Everything else in the values below carries back through earlier editions. Our Section V compliance page sets out how the articles relate to each other and to the referencing construction codes.

These are original questions written against the published body of knowledge, not reproduced from any examination. If certification rather than revision is the goal, training hours by method sets out what PT Level II requires in classroom and experience hours before the examination is even scheduled, and our training programme covers how those hours are delivered.

Types, methods and the two vocabularies

Question 1. A procedure calls for a Type II, Method C material set. What has it specified, and does Article 6 use that language? Answer: a visible colour contrast penetrant removed with solvent — and no, the Type and Method letters come from SE-165 and SAE AMS 2644 rather than from Article 6's own text. Why: T-651 describes two penetrant types, colour contrast and fluorescent, combined with three processes, water washable, post-emulsifying and solvent removable, giving six techniques. The letter system runs Type I fluorescent, Type II visible, Method A water washable, B post-emulsifiable lipophilic, C solvent removable, D post-emulsifiable hydrophilic. It simply splits post-emulsification into its two forms, which Article 6 also does at T-673.2.

Question 2. A part examined with visible penetrant is to be re-examined fluorescently for a second opinion. What does the code say? Answer: fluorescent penetrant examination shall not follow a colour contrast penetrant examination. Why: T-654 states it directly and adds that intermixing penetrant materials from different families or different manufacturers is not permitted. Residual visible dye quenches fluorescence, because the red pigment absorbs the emitted light before it leaves the developer layer, so a fluorescent retest on a previously dyed surface produces weaker indications than a first-pass examination would. The same clause warns that a retest with water washable penetrants can lose marginal indications through contamination.

Temperature and dwell: the windows people miss

Question 3. A wrought steel plate is examined for laps at a surface temperature of 45°F. What is the minimum penetrant dwell time? Answer: 20 minutes. Why: Table T-672 lists 10 minutes for laps and cracks in wrought material — extrusions, forgings and plate. The table's note qualifies every listed value for the range 50°F to 125°F (10°C to 52°C), and states that from 40°F (5°C) up to 50°F (10°C) the minimum penetrant dwell time is twice the value listed. Cold penetrant is more viscous, so capillary flow into a tight lap slows down, and the code buys back the lost mobility with time rather than with heat.

Question 4. The part surface reads 132°F in direct sun. Can the examination proceed? Answer: not as a standard technique. Why: T-652 requires the temperature of the penetrant and of the part surface to stay between 40°F and 125°F (5°C and 52°C) throughout the examination period, and permits local heating or cooling so long as the part returns to that band. Where compliance is impractical, T-653 sends you to Mandatory Appendix III, which qualifies the materials and the processing at the proposed temperature on liquid penetrant comparator blocks. Shade the part or qualify the technique: those are the two lawful routes, and proceeding without either is a procedure violation.

Removing excess penetrant without removing the indication

Question 5. During a solvent removable examination the technician sprays remover onto the part to clear a stubborn background before developing. What is wrong? Answer: Article 6 prohibits it outright. Why: T-673.3 requires excess solvent removable penetrant to be taken off by wiping with cloth or absorbent paper until most traces are gone, then lightly wiping with cloth or paper moistened with solvent. Flushing the surface with solvent following application of the penetrant and prior to developing is prohibited. Solvent flooding cannot distinguish between penetrant on the surface and penetrant held in a tight crack; it dissolves and carries away both, and the flaw reads clean.

Question 6. Why does Article 6 cap the hydrophilic pre-rinse at one minute? Answer: because the pre-rinse is a water wash, and water washes penetrant out of shallow discontinuities. Why: T-673.2(b) requires parts to be pre-rinsed with a water spray using the same process as for water washable penetrants, and states that pre-rinsing time shall not exceed one minute. The pre-rinse exists to strip the bulk of the surface penetrant so the emulsifier faces less work and needs a shorter contact time. Run it longer and it begins doing the emulsifier's job on the indications as well as on the background, and the loss is permanent.

Question 7. What is the mechanical difference between lipophilic and hydrophilic emulsification, and why does it matter for control? Answer: lipophilic emulsifier diffuses into the penetrant, hydrophilic emulsifier displaces it by detergent action, and only the second can be moderated by dilution. Why: T-673.2(a) applies the lipophilic emulsifier neat, by immersion or flooding, and diffusion starts on contact and cannot be reversed. T-673.2(b) applies the hydrophilic emulsifier as a bath at a manufacturer-set concentration, making the aggressiveness of the step a variable the shop controls. Over-emulsification strips penetrant from real discontinuities, and no amount of re-developing brings it back.

Question 8. What water pressure and temperature limits apply to removing water washable penetrant? Answer: pressure not exceeding 50 psi (350 kPa) and water temperature not exceeding 110°F (43°C). Why: T-673.1 sets both, and both are the variables that turn a wash into a strip. A high-pressure jet drives water into a discontinuity and displaces the penetrant column that would have fed the indication. Hot water lowers penetrant viscosity so it flows back out of the flaw more readily. Either fault produces a clean-looking part carrying no indications at all, which is the worst outcome the method can generate.

Developers: form, surface state and the clock

Question 9. Can dry powder developer be used with a visible red penetrant? Answer: no. Why: T-675 states that with colour contrast penetrants only a wet developer shall be used, while with fluorescent penetrants a wet or dry developer may be used. A visible dye indication is read as red against white, and it needs the uniform white background that a wet developer lays down as its carrier dries off. Dry powder gives a thin translucent dusting that does not hide the metal underneath, so the contrast the method depends on never forms. A fluorescent indication needs no white background, because it is read as light against dark.

Question 10. A nonaqueous developer follows a water washable penetrant. What does the code require about the surface and the application method? Answer: the surface must be dry, and the developer is applied by spraying. Why: T-675.2(b) requires nonaqueous developers to be applied by spraying except where safety or restricted access precludes it, in which case brushing is permitted. For water washable or post-emulsifiable penetrants the developer goes onto a dry surface, because the solvent carrier and residual water do not form an even film together. Brushing drags a wet coating across a forming indication and smears it, converting a sharp line into a diffuse stain.

Question 11. When does the interpretation window open and close? Answer: final interpretation is made not less than 10 minutes and not more than 60 minutes after developing time begins. Why: T-675.3 starts that clock immediately after a dry developer is applied, or as soon as a wet developer coating is dry, and T-676.1 sets the window. Ten minutes gives capillary action time to draw penetrant from tight flaws up into the developer layer. Sixty minutes is the point at which bleed-out has spread far enough to distort apparent size and shape. Longer periods are permitted where bleed-out does not alter the results.

Contaminant control on nickel, stainless and titanium

Question 12. Why must penetrant materials used on a nickel alloy be certified for sulphur, and materials used on 316L certified for halogens? Answer: because residues left in a crevice attack those alloys once the component sees service heat. Why: T-641 requires certification of contaminant content for all liquid penetrant materials used on nickel base alloys, austenitic or duplex stainless steels and titanium, tested in accordance with Mandatory Appendix II, with the manufacturer's batch numbers on the certificate. The limits are 1% sulphur by weight for the nickel group and 1% total chlorine plus fluorine for the stainless and titanium group. Sulphur embrittles nickel grain boundaries at temperature; retained chlorides drive stress corrosion cracking in austenitic stainless.

The clause catches shops out because it applies to the whole material set, not to the penetrant alone. Cleaner, emulsifier and developer all sit on the part and all leave residue, so all of them need certification. The record requirement is equally specific: batch numbers and test results, retained as the referencing code section requires. This is a documentation control problem more than a technical one, and it is the kind of gap that surfaces during report review rather than during the examination itself — see what makes an NDT report defensible.

Light levels and viewing conditions

Question 13. State the light requirements for a visible penetrant examination and for a fluorescent one. Answer: visible needs a minimum of 100 fc (1076 lx) on the surface being examined; fluorescent needs UV-A of at least 1000 µW/cm² on the surface throughout, ambient white light no greater than 2 fc (21.5 lx) in the darkened area, and 5 minutes of dark adaptation before interpreting. Why: T-676.3 and T-676.4 set them. The visible figure is an absolute floor for seeing red against white. The fluorescent figures are a ratio problem — the UV-A drives emission, the ambient ceiling protects the dark background, and dark adaptation shifts the eye onto its rod response.

Two supporting rules travel with those numbers and appear on exams as often as the numbers themselves. UV-A intensity is measured before use, whenever the light's power source is interrupted or changed, and at the completion of the examination or series of examinations. Reflectors and filters are checked and cleaned before use, and a cracked or broken filter is replaced immediately, because a broken filter passes visible light from the lamp straight onto the part. Glasses or lenses worn by the examiner must not be photosensitive, since a darkening lens defeats the dark adaptation the clause just required.

Reading bleed-out

Question 14. A developed surface shows a continuous fine line, a cluster of small round dots, and a broad diffuse smear. What does each pattern indicate? Answer: a crack or lap, porosity, and either a shallow open discontinuity or excess penetrant trapped in a surface irregularity. Why: bleed-out geometry follows flaw geometry. A tight linear flaw holds a column of penetrant that feeds a narrow, sharply defined line which keeps intensifying as you watch. Rounded porosity holds discrete volumes that produce discrete dots. A broad smear that appears immediately and never intensifies is a surface condition rather than a flaw, and T-676.2 recommends watching indications form during developer application to characterise exactly this case.

Question 15. An indication develops as a faint pink line rather than a deep red one. What does Article 6 say this suggests? Answer: excessive cleaning. Why: T-676.3 notes that with a colour contrast penetrant the developer forms a reasonably uniform white coating and surface discontinuities are indicated by bleed-out that is normally a deep red staining the developer, and that indications with a light pink colour may indicate excessive cleaning. The dye held in the flaw has been diluted or partly stripped, so what bleeds out is weak. The opposite fault has its own signature: inadequate cleaning leaves an excessive background that makes interpretation difficult. Both are removal-step faults and both require re-processing.

Where PT Level II candidates lose marks

The recurring failures are the four clocks. Penetrant dwell, hydrophilic pre-rinse, development time and the interpretation window are separate quantities with separate triggers, and candidates who revise them as a list of numbers rather than as a sequence merge them under pressure. Learn them as one timeline: penetrant on for the Table T-672 minimum, excess removed, developer applied, clock starts when dry, read between 10 and 60 minutes. Every number then has a position, and a question that changes the temperature or the material only moves one element of the chain.

The second recurring failure is treating the removal step as cleaning. It is not cleaning; it is a controlled partial removal, and every clause around it exists to stop the technician going too far. Wash pressure and temperature ceilings, the one-minute pre-rinse cap, the prohibition on solvent flushing and the warning about over-emulsification are four expressions of one idea. A candidate who holds that idea answers all four correctly without recalling any of the numbers individually.

If the gap is qualification rather than knowledge, our training programme covers PT Level I and II hours and the USA schedule covers where they run. Where the gap sits in a written procedure that no longer matches the current edition, technical procedure development is the faster fix. Technicians weighing whether to add methods will find the current United States picture on our NDT Level II salary page.

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