To perform this settling test according to ASTM E1444, equal amounts 14A fluorescent magnetic particles were mixed with different carrier fluids, including Magnaflux Carrier II, in a centrifuge tube, and placed to rest for 60 minutes.
What We See
Keep an eye on the difference in particle volume in the stem of each centrifuge tube, and the clarity and fluorescence of the carrier fluid.
Notice how all the 14A particles move quickly to the bottom of the Carrier II centrifuge tube so the carrier left in the top of the tube is very clear and transparent. While in the other two carrier products, the 14A particles stick to the sides of the centrifuge tubes, making these products look darker and cloudy.
To ensure reliable, high-quality mag particle inspections, make sure your particle carrier looks like the Carrier II centrifuge tube, instead of Product A or B.
How to Check Magnetic Particle Concentration
ASTM E1444 Standard Practice for Magnetic Particle Testing requires wet method magnetic particle concentration to be checked every 8 hours, or every shift change, and whenever the particle bath is changed or adjusted.
Make sure the mag particle bath is completely agitated so the particles are evenly distributed throughout the bath suspension.
Fill a 100 mL pear-shaped centrifuge tube with 100 mL of mag particle bath. See ASTM E709 Standard Guide for Magnetic Particle Testing for additional information on the correct centrifuge tube to use.
Demagnetize the centrifuge tube and put it in a stand in a place where it will not be disturbed.
Let the mag particle bath settle for 60 minutes for petroleum-based carrier baths (like the one in the video) and 30 minutes for water-based particle baths.
Read the volume of settling particles in the stem of the centrifuge tube.
If the settling volume is above or below the acceptable range, then add suspension liquid or particles and then perform the settling concentration test again.