A CWI is setting up a Magnetic Particle Testing (MT) inspection using the wet fluorescent particle method. Which of the following is a critical step to ensure proper particle concentration and dispersion?
- AApplying a thin film of developer after magnetization
- BDemagnetizing the part immediately after particle application
- CChecking the bath concentration using a centrifuge tube
- DUsing a black light with a wavelength outside the specified range
Show answer & explanationAnswer & explanation
Correct answer: C. Checking the bath concentration using a centrifuge tube
Checking the bath concentration using a centrifuge tube (settling test) is a critical step in wet magnetic particle testing to ensure the correct amount of particles are suspended in the liquid. Too high a concentration can lead to background fluorescence, while too low a concentration can result in missed indications. Developer is for PT, demagnetization is done after inspection, and incorrect black light wavelength will hinder detection.
Why the other options are wrong
- A. Developer application is part of Liquid Penetrant Testing (PT), not MT.
- B. Demagnetization is performed after the inspection is complete, not during particle application.
- D. Using an incorrect black light wavelength would impair the detection of fluorescent indications, it does not ensure proper concentration.
MT Wet Particle Concentration
The correct proportion of magnetic particles suspended in a liquid carrier to ensure effective detection of discontinuities without excessive background.
- Measured using a centrifuge tube (settling test).
- Too high concentration causes background; too low reduces sensitivity.
- Must be checked regularly during inspection.
Memory trick: Concentrate your particles, illuminate your findings, measure your bath.