T.O. 33B-1-1
2-65
temperature reaches and remains at 140°F (60°C) for over ten minutes, the inspection sensitivity can be reduced. As a
guideline remove the parts while they are warm but can still be handled with bare hands. This is a temperature of
about 120-125°F (49-52°C).
2.6.3
Dry Developer.
2.6.3.1
Description.
Dry developers are characterized by their fluffy nature and low bulk density, i.e.; one pound of dry developer occupies 2
or 3 times the volume that would be required for wet developer powders. Dry developers can be used with any type of
fluorescent penetrant but not with any visible-dye penetrant. They are loosely held on the part surface by adhesion.
Dry developer particles are generally white. When the dry developer is applied to part surfaces, the coating layer is
very thin and uniform. In fact, dry developers leave very little visible trace, but their presence becomes readily obvious
when a finger or rag is wiped across the surface. Dry developers SHALL NOT be used with visible-dye penetrants
since they do not provide adequate contrast.
2.6.3.2
Application.
WARNING
Dry developer particles are not toxic materials; however, like any solid foreign
matter; they should not be inhaled. Air cleaners, face masks, or respirators may be
required. The Base Bioenvironmental Engineer SHALL be consulted if the process
generates airborne particles.
NOTE
Dry developers SHALL NOT be applied to a part until the surface and any
discontinuities are thoroughly free of moisture. The presence of even a little
moisture will interfere with the developer action and small flaws may be missed.
Dry developers can be applied in a number of ways:
a. Blowing the powder on with a bulb type blower.
b. Immersing the part in a container of dry particle powder.
c. Pouring the powder over the parts.
d. Using a dust or fog chamber where the particles are blown into an air suspension.
e. Spraying with an electrostatic system or a low pressure flock gun.
2.6.3.2.1
After application, the excess developer should be shaken off or removed with a hand air bulb or squeeze blower. The
developer particles are not loosely held but care should be taken to not remove them during handling. Wiping,
brushing, or compressed air in excess of 5 psig SHALL NOT be used. Care must be taken to prevent contamination of
the dry developer. The two most frequent contaminants are water or moisture and penetrant. Water in dry developer
comes from parts that have not been completely dried or from careless splashing during the wash step. Water or
moisture contamination will cause the dry developer to form lumps or to cake, thus reducing its effectiveness.
Penetrant contamination occurs when particles of penetrant-soaked developer fall from poorly washed parts or heavy
indications. Penetrant contamination will cause false indications either on the part being processed or on subsequent
parts.
