AWS Certified Welding Inspector — FundamentalsNondestructive Examination (NDE)Easy
A CWI is inspecting a critical pressure vessel weld using the liquid penetrant testing (PT) method. After applying the penetrant and allowing the required dwell time, the CWI removes the excess penetrant using a water washable remover. Which of the following is the MOST critical next step to ensure accurate defect detection?
- AApplying a solvent cleaner to thoroughly dry the surface.
- BRe-applying penetrant if any residue is visible.
- CApplying the developer immediately after penetrant removal.
- DEnsuring the surface is completely dry before developer application.
Show answer & explanationAnswer & explanation
Correct answer: D. Ensuring the surface is completely dry before developer application.
After removing excess penetrant, it is crucial to ensure the surface is completely dry before applying the developer. Any moisture can interfere with the developer's ability to draw penetrant from discontinuities, leading to inaccurate indications or masking of defects.
Why the other options are wrong
- A. Applying a solvent cleaner after water washable penetrant removal is generally not recommended as it could remove penetrant from discontinuities.
- B. Re-applying penetrant would restart the entire process and is not the correct next step after excess penetrant removal.
- C. Applying developer to a wet surface can dilute the penetrant, prevent proper developer action, and result in false or missed indications.
PT - Drying after Penetrant Removal
After removing excess liquid penetrant, the inspection surface must be thoroughly dried before applying developer to ensure accurate defect detection.
- Moisture interferes with developer action.
- Insufficient drying can mask discontinuities.
- Over-drying can evaporate penetrant from shallow defects.
Memory trick: Clean, Penetrate, Remove, Dry, Develop, Inspect, Clean.