T.O. 33B-1-1
3-116
Table 3-7. Magnetic Rubber Equipment.
Electromagnetic yokes, fixed or articulated leg (same as used for magnetic particle inspection
Permanent bar magnets
Soft iron pole pieces
Stereo zoom microscope (7-10X) with light
Dial probe gaussmeter
Electronic gaussmeter
Table 3-8. Magnetic Rubber Inspection Materials.
Base material
Dibutyltin Dilaurate and Stannous Octoate catalysts.
Sealing compound (putty for forming dams)
Aluminum or plastic sheet material for forming dams
Lubricant (release agent) to aid in the removal of replicas from holes
Paper cups in which to mix magnetic rubber material
Tongue depressors for mixing the material
Isopropyl alcohol for cleaning replicas
Hypodermic disposable syringe for applying the rubber mixture to the inspection area
b. Prepare part for magnetic rubber inspection as follows:
(1)
Using cheesecloth or equivalent moistened with cleaning solvent MIL-C-38736 or equivalent,
remove grease, oil, dirt, lint, and similar contaminants from the area to be inspected.
(2) Remove paint topcoat or fuel tank coating, as appropriate, and primer coat and/or plating as
required.
CAUTION
If a delay is expected that would leave any area of steel in a bare metal state for over
1 hour, coat the area with corrosion preventive compound, Mil-C-16173, Grade 3.
The exterior topcoat or fuel tank coating shall be removed from the surfaces of holes
to be inspected.
The primer coat may be left on unless a specific procedure requires that it be
removed or unless the total thickness of the primer plus plating is greater than
0.005 inches.
NOTE
When building dams, make certain they are small enough to allow magnets or the
legs of an electromagnet to span the reservoir. Magnets or the legs of an
electromagnet should never be placed into the uncured magnetic rubber.
Using the procedures and materials as discussed above, virtually any area or
configuration can be prepared for magnetic rubber inspection. Upside-down
surfaces may be inspected by building a reservoir beneath the test area and pressure
filling with magnetic rubber. This type of reservoir must be provided with a vent
hole to prevent air entrapment.
