T.O. 33B-1-13.5.7.5.2.DeterminationofVehicleFluorescence.The settling test for particle concentration can be used to also judge vehicle f luorescence and is readilyperformed at a stationary unit. It is not as accurate as the laboratory test but is reasonably quantitative andreproducible. It can be easily standardized with the material in use, and is quite satisfactory as a daily guidefor the inspector. The following procedure SHALL be used in performing the vehicle f luorescence test afterthe steps in the settling test have been completed (see paragraph 3.5.6.8).a. Illuminate the suspension in the centrifuge tube with black light in a darkened area.Only the particle layer should f luoresce. Dirt, lint, etc. will usually settle more slowlythan the particles and may be seen as a nonf luorescent band or strip toward the top ofthe particle layer. For particle concentration determination, this layer of dirt must becarefully excluded from the total volume read. Dirt accumulation that exceeds 30% ofthe total volume of the particle layer can impede the formation of indications,requiring replacement of the bath.b. Fluorescence in the liquid may indicate bath breakdown (f luorescent pigmentationbeing stripped from the magnetic particles or fine magnetic particles remainingsuspended in the vehicle). If the vehicle f luoresces excessively, place the centrifugetube in its stand (which must not be ferromagnetic) with a horseshoe magnet incontact with the centrifuge tube (see Figure 3-34) and let sit on a vibration free surfacefor 1 hour for oil baths and 30 minutes for water baths. Illuminate the vehicle in thecentrifuge tube with black light in a darkened area. If the vehicle’s f luorescence isreduced or eliminated the cause of the f luorescence is fine magnetic particlesremaining suspended. If the level of f luorescence remains at the same level, thef luorescent pigmentation has been stripped from the magnetic particles.c. If it is determined that the cause of the vehicle’s f luorescence is stripping of thepigmentation, the suspension SHALL be replaced if it is serious enough to interferewith the results of the system effectiveness check using the Ketos ring.d. If it is determined that the cause of the excessive suspension f luorescence is finemagnetic particles remaining in the vehicle, and they are of a volume to interfere withthe results of the system effectiveness check using the Ketos ring an effort may bemade to remove them from the holding tank’s magnetic particle bath. This can bedone with magnets. The magnetic particle bath in the magnetic particle machine’sholding tank should be allowed to rest (not agitated) for forty (40) minutes. Place themagnets in the magnetic particle bath, taking care not to place them so deep that theywill attract the particles that have settled out of suspension. The length of time ornumber of times that the magnets will have to be cleaned of particles and submergedis dependent upon the seriousness of the problem. The bath SHALL be able to passthe system effectiveness check, after the removal of as many suspended particles aspossible or be replaced.3-74Change 1
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
