TM 1-1500-204-23-7
NOTE
Dusting may be accomplished by air fluffing the dry powder in a sealed chamber so that the
circulation of air deposits the absorbant powder on the vertical sides as well as on the bottom
horizontal surfaces of the object being inspected
k.
Developer Draining. Wet developers for Type I and II penetrants when applied, shall be allowed to drain prior to
drying. The part shall be positioned during draining (and drying) to ensure that pools of developer do not form and mask
indications.
l.
Developer Dwell Time. Developer dwell time will depend on the type of penetrant developer and type of defect.
Sufficient time should be allowed for an indication to form, but the penetrant should not be allowed to bleed into the
developer in such quantities to cause a loss of definition.
NOTE
Developer dwell time will vary from a few minutes to an hour or more. A good rule of thumb is
that development time for any given material or type of defect is about one-half of that
considered proper for penetration dwell time.
m.
Removal Methods. Type I and II, Method A penetrants shall be removed from the surface of the part under test
by rinsing as follows
(1)
A spray nozzle discharging a coarse spray and a high volume of water shall be held approximately 12
inches away from the part under test.
NOTE
Water shall be cold and under low pressure (20-30 psi).
(2)
The rinse time for water-washable penetrants shall be the minimum time necessary to remove background
color or fluorescence.
NOTE
Water rinsing of Type I, Method A penetrants shall be accomplished with the aid of black light to
ensure that the penetrant is completely removed from the surface. Washing must be done in a
darkened area.
3-11. Specific Procedures for Fluorescent Penetrant Inspection. Specific procedures for fluorescent penetrant
inspections are described in the following paragraphs.
a.
Inspection Conditions. Ensure all preinspection conditions are met prior to performing penetrant Inspection.
Refer to TM 55-1500-335-23 for specific information.
b.
Surface Preparation. Prepare surface of part by removing dirt, dust, loose scale, and oil or grease. Any foreign
matter left on surface may cause erroneous indications
c.
Lighting and Facilities. Complete darkness is desired for maximum visibility and contrast, since even minute
points of light emission are readily seen in complete darkness. A light-proof room is not necessary or possible. Absolute
darkness is never achieved, since the black light lamps give off some visible violet light. This small amount of violet
light is actually not a disadvantage, as it makes it possible to see the part being handled. Indications, which glow with a
bright yellowgreen, are in good contrast with the violet, and are easily seen.
WARNING
Ultraviolet radiation below the 3000A wavelength is harmful to the eyes. Cracked or improperly
positioned filters shall not be used.
d.
Black Light. The fluorescent quality of the penetrant is most brilliant when viewed under light of sufficient
intensity in a particular wave length. Good inspections cannot be performed unless adequate lights are used. Since the
light used is almost invisible, it is called black light. It must, however, be of proper wave length and intensity at the point
of inspection or the effectiveness of the inspection will be greatly reduced
(1)
Sources. The sources of black light are carbon arc system, low pressure fluorescent bulbs, and high
pressure mercury bulbs.
3-9
