DEVELOPER (also called Wet Developer)
A mixture of developing
powder and water that is used to draw the penetrant indications to
the surface. See
The environment against which an indication must be
evaluated. It may be the natural surface of the part.
Light in the near
ultraviolet range, just short of visible light. Fluorescent
penetrants absorb this ultraviolet radiation and emit light in the
visible region. The darker the surroundings the brighter this
emitted light appears to be. Extended exposure to black light can be
harmful unless protective eyewear is used. See
The action of the developer in "drawing out" the penetrant from a
surface discontinuity causing maximum bleed-out for increased
contrast and sensitivity.
The tendency of certain liquids to travel, climb or draw into tight
crack-like interface areas due to such properties as surface
tension, wetting, cohesion, adhesion and viscosity.
A discontinuity whose size, shape, orientation,
location or properties make it detrimental to the useful service of
the part in which it occurs or which exceeds the accept/reject
criteria for the given design.
Developers are used to
enhance the visibility of small amounts of penetrant bleeding from
small discontinuities. Developers draw or absorb penetrant materials
from a surface discontinuity to allow the penetrant to be visible
under natural or black light. See
Choose the Developer
Any interruption in the normal physical structure or configuration
of a part, such as crack, laps, seams, inclusions or porosity. A
discontinuity may or may not affect the usefulness of a part.
The time in which a penetrant or developer is in
contact with the surface of the part. Drain time is considered to be
part of the dwell time.
An emulsifier (sometimes called removers) is a surfactant used with
certain types of penetrants to make oil in the penetrant water
dispersible and therefore water washable. When a penetrant system
is used with an emulsifier it is possible to use the emulsifier to
control the sensitivity of the pentrant to find small flaws as well
as shallow wide defects. See
The minimum temperature at which a flammable-vapor mixture exists at
the surface of a liquid.
An imperfection in an item or material which may or
may not be harmful. If it is harmful, it is a defect.
Fluorescent penetrants require the surrounding area to be darkened
and can be seen only with the aid of a black light. Because of the
special requirements of fluorescent penetrants, they are chosen less
often for outside and portable applications. They are available in
a variety of sensitivity levels. See
Emulsifiers (sometimes called removers) are used with certain types
of penetrants to make oil in the penetrant water dispersible and
therefore water washable. Hydrophilic emulsifiers are the most
commonly used emulsifer - used only with non-waterwashable
The presence of penetrant on a surface that may or
may not show the location of a discontinuity.
A nondestructive tool used to find defects. Penetrants highlight
flaws and leaks that are open to the surface and are too small to
see by normal visual inspection. Penetrants show the presence,
location, nature and size of defects. See
Choose the Penetrant
How to use Penetrants
Lipophilic emulsifiers are used with certain types of penetrants to
make oil in the penetrant water dispersible and therefore water
washable. Lipophilic emulsifiers are oil based and are used
undiluted. They are faster than hydrophilic emulsifiers, but are
not as flexible and do not always give as sensitive results as do
hydrophilic. Disposal is often more difficult. AGC lipophilic
emulsifiers are less volatile and easier to dispose of than others
on the market. They can be used with any non water-washable
See Inspection Penetrants
A type of penetrant
containing no emulsifier but which is cleaned from a surface with
water after applying an emulsifier as a separate step. Often
abbreviated as P.E. See
Post Emulsification Penetrant Test.
QUALIFIED PRODUCTS LIST (QPL)
The US Government tests and approves inspection penetrants and
publishes a Qualified Products List. At present this is SAE AMS
A penetrant removal technique which is used with visible or
fluorescent penetrants which are not water washable. It is most
often used with portable kits, in aerosol form. It is one of the
easiest removal methods to use.
A visible penetrant produces a red indication which is easily
visible in bright light. It is often used outside with portable
kits. The main disadvantage of visible penetrants is that they can
only be used in one sensitivity. Their use is limited to less
critical applications. See
DEVELOPER (also called
A mixture of developing powder and water that is used
to draw the penetrant indications to the surface.