T.O. 33B-1-1
3-68
c. Remove cap, cover, seal, or plug from the bulk vehicle container. Obtain a clean glass tube of sufficient
length to reach from the bottom of the bulk vehicle container to at least six (6) inches above the
container opening when tube is held in the vertical position.
d. Place thumb over one end of the glass tube. Insert the other end of the glass tube slowly in a vertical
position into the bulk vehicle. Insure that the tube is all the way to the bottom of the container.
e. Release thumb on upper end of the glass tube for five (5) to ten (10) seconds, then replace thumb over
end of glass tube. Remove glass tube slowly from the bulk vehicle maintaining its vertical position.
f. Prior to removing thumb from the end of the glass tube, observe the level of contamination in the glass
tube. Water and other contaminants should be evident in lower portion of the glass tube, if present. (At
depot facilities, if the vehicle is suspected, the contents of the glass tube may be sent to the depot
chemical laboratory for analysis).
g. If contaminants are evident in the bottom of the container, siphon off the good vehicle to within two
inches of contamination level.
h. See paragraph 3.2.5.1.2 for disposition instructions of contaminated bulk vehicle.
3.5.6.6.3
Particle Concentration.
NOTE
Prior to adding the magnetic particles to the vehicle they SHALL be demagnetized
to eliminate any agglomeration that might have developed during storage because of
magnetization.
The strength of the bath is a major factor in determining the quality of the indications obtained. Too heavy a
concentration of particles gives a confusing background and excessive adherence of particles at external poles, reducing
the visibility of indications of very fine discontinuities. Add magnetic particles to obtain a suspension concentration as
follows:
a. Visible magnetic particle bath concentrations: 1.2 to 2.4 milliliters (ml) of particles per 100 ml of
vehicle.
b. Fluorescent magnetic particle bath concentrations: 0.1 to 0.4-ml/100 ml.
These ranges are rather broad for uniform results and should be reduced by the individual laboratories for their specific
requirements. The optimum range for most magnetic particle bath concentrations is 1.5 to 2.0 ml/100 ml for visible
particles and 0.15 to 0.20 ml/100 ml for fluorescent particles.
3.5.6.6.4
Dry Powder Concentrate.
Measure out the required amount of powdered concentrate and pour it directly into the bath liquid in the tank. The
agitation system should be running and the concentrate poured in at the pump intake, so that it will be quickly drawn
into the pump and dispersed. The new pre-wet concentrates will disperse very quickly even through the large volume of
bath in large units. After 10 minutes of operation the bath strength should be checked with a settling test. The amount
of settled material should check approximately with the volume requirements in paragraph 3.5.6.6.3.
3.5.6.6.5
Paste Concentrate.
The procedure is similar to that followed with the dry powder concentrates, except that the paste must be weighed
instead of measured. It is transferred to a mixing cup or bowl, bath liquid is added little at a time, and mixed until a
smooth thin slurry has been produced. This slurry is then poured into the tank at the point where the agitation system
