T.O. 33B-1-1
2-28
NOTE
With the elimination of the use of 1,1,1 trichloroethane (methyl chloroform), the
solvent remover in portable penetrant kits is most likely to be Class 2 (non-
halogenated). Most Class 2 solvent removers are hydrocarbon solvents such as
aliphatic naphtha. While they are excellent solvents, because of their high boiling
point (in excess of 300F) such Class 2 solvent removers will not rapidly evaporate
at room temperature. Consequently, when used as a precleaner, care must be taken
to assure there is no residual solvent remover on the part surface prior to the
application of penetrant. This can be accomplished by thoroughly drying the
surface with a cloth or rag or, alternatively, using a more volatile solvent such as
isopropyl alcohol to remove the less volatile solvent remover.
Portable penetrant kits contain aerosol spray cans of penetrant, developer and solvent remover. The solvent remover is
used in three ways: it serves as a precleaner before penetrant application; it removes the last of the excess penetrant
after completion of the penetrant dwell; and serves as a postcleaner to remove residual penetrant materials when the
inspection has been completed. This section deals with using the solvent as a precleaner.
2.3.7.2
Method of Applying Spray Solvent.
The method of applying spray solvent remover as a precleaner is different than when it is used to remove penetrant
following penetrant dwell. When used as a precleaner, the solvent remover may be sprayed directly on the test surface.
Spraying the solvent directly on the surface is not permitted when removing excess surface penetrant during a penetrant
inspection process. As a precleaner, a liberal amount of solvent should be applied and the excess solvent and
contaminants wiped from the test surface with a dry, lint free cloth or paper towels. The spray and wiping operation
should be repeated until a clean surface is obtained. Following the, application of spray solvent, a dwell period must be
allowed to permit evaporation of any residual solvent before applying penetrant.
2.3.7.3
Hazards Of Aerosol Cans.
Aerosol cans are a convenient method of packaging a wide variety of materials. Their wide use, both in industry and
the home, has lead to complacency and mishandling which can be hazardous. Some of the hazards in the use of aerosol
cans are discussed below:
a. The containers are gas pressure vessels. When heated the gas pressure increases. At temperatures
above 120°F (49°C) the container may burst.
b. Any combustible material, regardless of flash point, can ignite with explosive force when it is finely
divided and dispersed in air.
c. Penetrant materials (penetrant, cleaner/remover and developer) may contain petroleum distillates and
aliphatic (kerosene, mineral spirits, etc.) or aromatic (benzene type hydrocarbon) solvents. These
chemicals must be carefully used in the aerosol form to avoid health hazards.
2.3.8
Postcleaning After Penetrant Inspection.
2.3.8.1
Effects Of Inspection Residues on Subsequent Service.
Penetrant inspection residues can have several adverse effects on subsequent processing and service. Developer and
penetrant residues, if not removed, have detrimental effects on the application of surface finishes such a painting,
plating and anodizing. Penetrant residues in flaws or discontinuities can seriously affect weld quality if not removed
prior to repair welding. Parts that will contact liquid oxygen must be given special attention. Traces of oil can cause
an explosion when contacted by liquid oxygen. Developer residues can interfere with the functioning of the part if they
involve a moving or wear surface. In addition, developer materials can absorb and retain moisture resulting in
corrosion of the part.
