TM 1-1500-204-23-7
e.
Draining. After the part is coated with the penetrant, the part is set aside to drain. The length of time during
which the part is allowed to drain (penetration time) and the position of the part during draining are extremely important
factors for reliable penetrant inspection.
f.
Penetration Times. The minimum penetration time, in minutes, of penetrants on materials under test are shown
In table 3-1. Longer penetration time, or additional penetration application, may be necessary for questionable parts to
ensure full indication of defects.
g.
Emulsifier Application. Type I and II Method B emulsifiers can be applied by one of the following methods:
Dripping
Flow-on
Spraying
Any other method which will rapidly cover all the penetrant
CAUTION
Brushing on emulsifiers is not recommended since the brushing action mixes the emulsifier with
the penetrant prematurely and irregularly, and makes accurate control of emulsification time
Impossible
h.
Emulsifier Draining. After the emulsifier is applied to the penetrant-coated part or material under test, the part or
material is removed to a rising station for immediate rinsing at the end of the emulsifier dwell time In effect, therefore,
there is no emulsifier drain time.
i.
Emulsifier Dwell Time. The emulsifier dwell time is explained in the following paragraphs.
(1)
Type I, method B emulsifiers. The optimum emulsifier dwell time shall be determined and established by
trial on Identical or similar parts or materials The optimum time shall be as follows.
The minimum time necessary to remove the surplus penetrant for detecting wide shallow defects
The minimum time necessary to remove the surplus penetrant from the machine marks, dents,
or other shallow surface roughness condition for detecting fine cracks.
The maximum dwell time possible without over-emulsification
NOTE
The maximum dwell time of five minutes shall be used for Type I Emulsifiers.
(2)
Type ll., method B emulsifiers. The optimum emulsifier dwell time shall be determined In the same
manner as Type I emulsifiers, except the optimum time shall be held to the absolute minimum time necessary to remove
the surplus penetrant.
NOTE
Some Type II emulsifiers require rinsing within a few seconds after application
j.
Developer Application Aqueous wet, nonaqueous wet, and dry developers can be applied by the following
methods.
NOTE
The wet developer solution should be constantly agitated while In use to keep the developer
powder In suspension. For open tanks, a circulation pump, motor driven Impeller, or air
agitation are satisfactory For pressurized spray cans, the can should be shaken vigorously
before each use until the agitator in the can rattles.
(1)
Aqueous wet developers. Aqueous wet developers can be applied by one of the following methods.
Dipping (normal method)
Flow-on (normal method)
Spraying (for high sensitivity)
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