AWS Certified Welding Inspector — FundamentalsNondestructive Examination (NDE)Easy
A CWI is performing a Liquid Penetrant Testing (PT) inspection on a non-ferrous casting. After the dwell time, the excess penetrant has been removed, and the developer applied. What is the primary purpose of the developer in this process?
- ATo provide a contrasting background for indications
- BTo draw penetrant out of discontinuities and make them visible
- CTo dissolve and remove residual penetrant from the surface
- DTo enhance the magnetic properties of the material
Show answer & explanationAnswer & explanation
Correct answer: B. To draw penetrant out of discontinuities and make them visible
The primary purpose of the developer in PT is to draw the penetrant that has seeped into discontinuities back to the surface, making the indications visible to the naked eye or under UV light. It acts like a blotter, creating a visible bleed-out against a contrasting background.
Why the other options are wrong
- A. While developer often provides a contrasting background, its primary purpose is to draw out the penetrant from flaws.
- C. Removal of residual penetrant is done by the emulsifier or remover, not the developer.
- D. Enhancing magnetic properties is related to Magnetic Particle Testing (MT), not PT.
PT Developer Function
A fine, absorbent powder applied to the surface after penetrant removal, which acts to draw penetrant from flaws and make indications visible.
- Acts as a blotter, creating a visible bleed-out.
- Comes in various forms: dry, wet, non-aqueous.
- Provides contrast for better visibility of indications.
Memory trick: Clean, Penetrate, Remove, Develop, Inspect.