The document provides information on the basic principles of liquid penetrant testing (PT). It discusses how PT works via capillary action, with low surface tension penetrant entering surface-breaking discontinuities. It explains factors that influence penetrant dwell time and the ability to detect flaws. It also covers visual acuity of the human eye in PT, the history of the technique, basic processing steps, and the importance of cleaning surfaces to be tested.

1. OM NDT TRAINING & CONSULTANCY
www.omndt.org
PENETRANT TESTING L-II
Prepared by
MAHESH PANDIT
ASNT NDT L-III

2. Basic principle of a Liquid Penetrant
• DPI is based upon capillary action, where low surface
tension fluid penetrates into clean and dry surface-
breaking discontinuities. Penetrant may be applied to
the test component by dipping, spraying, or brushing.
After adequate penetration time has been allowed, the
excess penetrant is removed and a developer is
applied. The developer helps to draw penetrant out of
the flaw so that an invisible indication becomes visible
to the inspector. Inspection is performed under
ultraviolet or white light, depending on the type of dye
used - fluorescent or non fluorescent (visible).

3. Capillary action is the ability of a liquid to
flow in narrow spaces without the
assistance of, and in opposition to,
external forces like gravity. The effect can
be seen in the drawing up of liquids
between the hairs of a paint-brush in a
thin tube, in porous materials such as
paper. It occurs because of intermolecular
forces between the liquid and
surrounding solid surfaces

4. Intermolecular forces are forces of attraction or
repulsion which act between neighboring particles.
Surface tension is a contractive tendency of the
surface of a liquid that allows it to resist an external
force. The cohesive forces between liquid molecules
are responsible for the phenomenon known as
surface tension. Surface tension is typically measured
in dynes/cm, the force in dynes required to break a
film of length 1 cm. Water at 20°C has a surface
tension of 72.8 dynes/cm . The surface tension of
water decreases significantly with temperature .
Soaps and detergents further lower the surface
tension.

5. Basic principle of a Liquid Penetrant
• When a liquid comes into contact with a surface
both cohesive and adhesive forces will act on it.
These forces govern the shape which the liquid
takes on. Due to the effects of adhesive forces,
liquid on a surface can spread out to form a thin,
relatively uniform film over the surface, a process
known as wetting. Alternatively, in the presence
of strong cohesive forces, the liquid can divide
into a number of small, roughly spherical beads
which stand on the surface, maintaining minimal
contact with the surface.

6. Basic principle of a Liquid Penetrant
• Cohesive forces are the intermolecular forces
which cause a tendency in liquids to resist
separation. These attractive forces exist
between molecules of the same substance.
For instance, rain falls in droplets, rather than
a fine mist, because water has strong cohesion
which pulls its molecules tightly together,
forming droplets.

7. Basic principle of a Liquid Penetrant
• Adhesive forces are the attractive forces between
unlike molecules. In the case of a liquid wetting
agent, adhesion causes the liquid to cling to the
surface on which it rests. When water is poured
on clean glass, it tends to spread, forming a thin,
uniform film over the glasses surface. This is
because the adhesive forces between water and
glass are strong enough to pull the water
molecules out of their spherical formation and
hold them against the surface of the glass, thus
avoiding the repulsion between like molecules

8. Basic principle of a Liquid Penetrant
• When the cohesive force of the liquid is
stronger than the adhesive force of the liquid
to the wall, the liquid concaves down in order
to reduce contact with the surface of the wall.
When the adhesive force of the liquid to the
wall is stronger than the cohesive force of the
liquid, the liquid is more attracted to the wall
than its neighbors, causing the upward
concavity.

10. Basic principle of a Liquid Penetrant
• The meniscus : is the curve in the upper surface of a liquid
close to the surface of the container or another object,
caused by surface tension. It can be either convex or
concave, depending on the liquid and the surface.
• A convex meniscus occurs when the molecules have a
stronger attraction to each other (cohesion) than to the
material of the container (adhesion), causing the surface of
the liquid to cave downward.
• This may be seen between mercury and glass in barometers
and thermometers. Conversely, a concave meniscus occurs
when the molecules of the liquid are attracted to those of
the container, causing the surface of the liquid to cave
upwards. This can be seen in a glass of water.

11. Basic principle of a Liquid Penetrant
• The height to which the liquid rises is directly
proportional to the surface tension of a liquid and
to the cosine of the angle of contact.
• The viscosity of the liquid is not a factor in the
basic equation of capillary rise. Viscosity is
related to the rate at which a liquid will flow
under some applied unbalanced stress; in itself,
viscosity has a negligible effect on penetrating
ability.
• In general, however, very viscous liquids are
unsuitable as penetrants because they do not
flow rapidly enough over the surface of the work
piece; consequently, they require excessively long
periods of time to migrate into fine flaws.

13. Basic principle of a Liquid Penetrant
The ability of a given liquid to flow over a surface
and enter surface cavities depends principally on
the following:
• Cleanliness of the surface
• Configuration of the cavity
• Cleanliness of the cavity
• Size of surface opening of the cavity
• Surface tension of the liquid
• Ability of the liquid to wet the surface
• Contact angle of the liquid

14. Penetrant Dwell
The factors that influence the length of time for
the penetrant to enter and fill a surface void
include :
• Void size
• Penetrant material
• The type of discontinuity
• Penetrant viscosity and
• The cleanliness of the discontinuity.

15. Basic principle of a Liquid Penetrant
• If θ is less than 90° (Fig. 1a), the liquid is said
to wet the surface, or to have good wetting
ability;
• if the angle is equal to or greater than 90° (Fig.
1b and c), the wetting ability is considered
poor.
• If θ is greater than 90°, the liquid is depressed
in the tube and does not wet the tube wall,
and the meniscus is convex (Fig. 2c).

16. Figure 2

17. History of PT
• A very early surface inspection technique
involved the rubbing of carbon black on glazed
pottery, whereby the carbon black would
settle in surface cracks rendering them visible.
Later, it became the practice in railway
workshops to examine iron and steel
components by the "oil and whiting" method
by Magna flux in (Chicago)

18. History of PT
• In this method, a heavy oil was diluted with
kerosene in large tanks so that locomotive parts
such as wheels could be submerged. After
removal and careful cleaning, the surface was
then coated with a fine suspension of chalk in
alcohol so that a white surface layer was formed
once the alcohol had evaporated. The object was
then vibrated by being struck with a hammer,
causing the residual oil in any surface cracks to
seep out and stain the white coating

19. Why a Penetrant Inspection Improves
the Detectability of Flaws?
• 1) It produces a flaw indication that is much
larger and easier for the eye to detect than
the flaw itself.
• 2) it produces a flaw indication with a high
level of contrast between the indication and
the background
• 3) The developer serves as a high contrast
background as well as a blotter to pull the
trapped penetrant from the flaw.

20. Visual Acuity of the Human Eye
• Due to the physical features of the eye, there is a threshold
below which objects cannot be resolved. This threshold of visual
acuity is around 0.003 (0.076mm) inch for a person with 20/20
vision.
• 20/20 vision, it means that when you stand 20 feet away from
the chart you can see what the "normal" human being can see.
• The human eye is more sensitive to a light indication on a dark
background and the eye is naturally drawn to a fluorescent
indication.
• With a light indication on a dark background, indications down
to 0.003 mm (0.0001 inch) may be seen when the contrast
between the flaw and the background was high.
• But dark indication on a lighter background can’t.

21. Visual Acuity of the Human Eye
The eye has a visual acuity threshold below which an
object will go undetected. This threshold varies from
person to person, but as an example, the case of a
person with normal 20/20 vision can be considered.
As light enters the eye through the pupil, it passes
through the lens and is projected on the retina at the
back of the eye.
Muscles called extra ocular muscles, move the
eyeball in the orbits and allow the image to be
focused on the central retinal or fovea.

25. The retina is a mosaic of two basic types of
photoreceptors: rods, and cones. Rods are
sensitive to blue-green light with peak
sensitivity at a wavelength of 498 nm, and
are used for vision under dark or dim
conditions. There are three types of cones
that give us our basic color vision: L-cones
(red) with a peak sensitivity of 564 nm, M-
cones (green) with a peak sensitivity of 533
nm, and S-cones (blue) with a peak
sensitivity of 437 nm.

26. Visual Acuity of the Human Eye
• The standard definition of normal visual acuity (20/20
vision) is the ability to resolve a spatial pattern separated
by a visual angle of one minute of arc. Since one degree
contains sixty minutes, a visual angle of one minute of arc is
1/60 of a degree.
• For the case of normal visual acuity the angle Theta is 1/60
of a degree. By bisecting this angle we have a right triangle
with angle Theta/2 that is 1/120 of a degree. Using this
right triangle it is easy to calculate the distance X/2 for a
given distance d.
• X/2 = d (tan Theta/2)
• under normal lighting conditions, the eye is most sensitive
to a yellowish-green color.

27. Visual Acuity of the Human Eye
• When the light levels drop to near total darkness, the
response of the eye changes significantly by the scotopic
response curve .
• At this level of light, the rods are most active and the
human eye is more sensitive to the light present, and less
sensitive to the range of color.
• At this very low light level, sensitivity to blue, violet, and
ultraviolet is increased, but sensitivity to yellow and red is
reduced.
• Fluorescent penetrant inspection materials are designed to
fluoresce at around 550 nanometers to produce optimal
sensitivity under dim lighting conditions.

28. System performance checks
• System performance checks involve processing a test
specimen with known defects to determine if the
process will reveal discontinuities of the size required.
• The most commonly used test specimen is the TAM or
PSM panel. These panel are usually made of stainless
steel that has been chrome plated on one half and
surfaced finished on the other half to produced the
desired roughness. The chrome plated section is
impacted from the back side to produce a starburst set
of cracks in the chrome. There are five impacted areas
to produce range of crack sizes. Each panel has a
characteristic “signature” and variances in that
signature are indications of process variance.

29. Sherwin PSM-5 Penetrant System Monitor Panel
• A stainless steel panel, 0.090“(2.286mm) thick and
measuring 4 x 6 inches. A chrome plated strip runs the
length of one side of the panel. Five crack centers are
evenly spaced in the chrome plating in order of
magnitude; the largest is readily visible with low
sensitivity penetrants, while the smallest is difficult to
observe even with high sensitivity materials. Adjacent to
the chrome plated section is a grit blasted area of
"medium roughness", to judge penetrant wash
characteristics.

30. System performance on PSM
The minimum number of crack indications on
PSM panel shall be visible as follows:
Level ½ and 1 – three indications
Level 2 - four indications
Level 3 and 4 - five indications
Removability test on PSM
At least 75% of the grit blasted panel shall show
no evidence of background fluorescence

31. Basic Processing Steps of a Liquid
Penetrant Inspection
• 1) Surface preparation: The surface must be free
of oil, grease, water, or other contaminants that
may prevent penetrant from entering flaws.
• 2) Penetrant Application: Once the surface has
been thoroughly cleaned and dried, the
penetrant material is applied by spraying,
brushing, or immersing the part in a penetrant
bath.

32. 3) Penetrant Dwell: The penetrant is left on the
surface for a sufficient time to allow as much
penetrant as possible to be drawn from or to
seep into a defect. Minimum dwell times
typically range from five to 60 minutes.
Generally, there is no harm in using a longer
penetrant dwell time as long as the penetrant is
not allowed to dry.
4) Excess Penetrant Removal:
5) Developer Application: A thin layer of
developer is then applied to the sample to
draw penetrant trapped in flaws back to the
surface where it will be visible.

33. 6) Indication Development: The developer is allowed
to stand on the part surface for a period of time
sufficient to permit the extraction of the trapped
penetrant out of any surface flaws. This development
time is usually a minimum of 10 minutes.
7) Inspection: Inspection is then performed under
appropriate lighting to detect indications from any
flaws which may be present.
8) Clean Surface: The final step in the process is to
thoroughly clean the part surface to remove the
developer from the parts that were found to be
acceptable.

34. Contaminants
• Coatings, such as paint, are much more elastic than
metal and will not fracture even though a large defect
may be present just below the coating.
• The part must be thoroughly cleaned as surface
contaminates can prevent the penetrant from entering
a defect.
• Surface contaminants can also lead to a higher level of
background noise since the excess penetrant may be
more difficult to remove.
• contaminates that must be removed include: paint,
dirt, flux, scale, varnish, oil, etchant, smut, plating,
grease, oxide, wax, decals, machining fluid, rust, and
residue from previous penetrant inspections

35. Pre-cleaning
• Regardless of the penetrant chosen, adequate pre-
cleaning of work pieces prior to penetrant inspection is
absolutely necessary for accurate results. Without
adequate removal of surface contamination, relevant
indications may be missed because:
• The penetrant does not enter the flaw
• The penetrant loses its ability to identify the flaw
because it reacts with something already in it
• The surface immediately surrounding the flaw retains
enough penetrant to mask the true appearance of the
flaw

36. Cleaning
• Alkaline cleaners can be detrimental to the
penetrant inspection process if they have silicates
in concentrations above 0.5 percent.
• Sodium meta-silicate, sodium silicate, and related
compounds can adhere to the surface of parts
and form a coating that prevents penetrant entry
into cracks.
• some domestic soaps and commercial detergents
can clog flaw cavities and reduce the wettability
of the metal surface, thus reducing the sensitivity
of the penetrant.

37. Cleaning methods
Selection of a cleaning method depends upon
the type of contaminant to be removed and the
type of alloy being cleaned.
This cleaning methods are generally classified as
• Chemical,
• Mechanical,
• Solvent, (methylene chloride, isopropyl
alcohol,naptha)
• or any combination of these.

38. Cleaning methods
• Chemical cleaning methods include alkaline or acid cleaning, pickling or
chemical etching.
• Mechanical cleaning methods include tumbling, wet blasting, dry abrasive
blasting, wire brushing, and high pressure water or steam cleaning.
Tumbling or rumbling is a technique for smoothing and polishing a rough
surface on relatively small parts. Metal tumbling is used to burnish(plastic
deformation of a surface due to sliding contact with another object),
deburr(neaten and smooth the rough edges), clean, radius, de-flash, descale,
remove rust, polish, brighten, surface harden, prepare parts for further
finishing.
Mechanical cleaning methods should be used with care because they often
mask flaws by smearing adjacent metal over them.
• Solvent cleaning methods include vapor degreasing, solvent spraying,
solvent wiping, and ultrasonic immersion using solvents.
• Probably the most common method is vapor degreasing. However,
ultrasonic immersion is by far the most effective means of ensuring clean
parts, but it can be a very expensive capital equipment investment.

39. Mechanical methods
• Abrasive tumbling : Removing light scale, burrs, welding
flux, braze stop-off, rust, casting mold, and core material;
• Wire brushing removing light deposits of scale, flux, and
stop-off. Stop-off ,which are blends of metallic-oxides used
to "stops" molten brazing filler metal (BFM) from flowing
into areas where it is not required.
• Stop-Off is a brazing aid commonly used in silver and
aluminum brazing. It is used to prevent the flow of flux and
metal to unwanted areas during brazing.
• High-pressure water and steam used with an alkaline
cleaner or detergent; removing typical machine shop soils
such as cutting oils, polishing compounds, grease, chips etc.
• Ultrasonic cleaning used with detergent and water or with
a solvent; removing adherent shop soil from large
quantities of small parts

40. Chemical methods
• Alkaline cleaning Removing braze stop-off, rust, scale, oils,
greases, polishing material, and carbon deposits; ordinarily
used on large articles where hand methods are too
laborious;
• Acid cleaning Strong solutions for removing heavy scale; mild
solutions for light scale; weak (etching) solutions for
removing lightly smeared metal

41. Solvent methods
• Vapor degreasing removing typical shop soil, oil,
and grease; usually employs chlorinated
solvents; not suitable for titanium, Nickel alloys
and certain stainless steel.
• Solvent wiping Same as for vapor degreasing
except a hand operation; may employ non-
chlorinated solvents; used for localized low-
volume cleaning
• Minimal washing or under-emulsification can
result in excessive background, which could
mask the flaws and render them undetectable.

42. Common Uses of Liquid Penetrant Inspection
• LPI can be used to inspect almost any material
provided that its surface is not extremely rough
or porous. It include the following:
• Metals (aluminum, copper, steel, titanium, etc.)
• Glass
• Many ceramic materials
• Rubber
• Plastics

43. It can only be used to inspect for flaws that break
the surface of the sample. Some of these flaws
are listed below:
1. Fatigue cracks
2. Quench cracks
3. Grinding cracks
4. Overload and impact fractures
5. Porosity
6. Laps
7. Seams
8. Pin holes in welds
9. Lack of fusion along the edge of the bond line

44. Advantages of Penetrant Testing
• High sensitivity to small surface
discontinuities.
• Large areas and large volumes of
parts/materials can be inspected rapidly and
at low cost.
• Parts with complex geometric shapes are
routinely inspected
• Aerosol spray cans make penetrant materials
very portable.

45. Disadvantages of Penetrant Testing
• Only surface breaking defects can be
detected.
• Only materials with a relatively nonporous
surface can be inspected.
• Pre-cleaning is critical since contaminants can
mask defects.
• Metal smearing from machining, grinding, and
grit or vapor blasting must be removed prior
to LPI.

46. Disadvantages of Penetrant Testing
• The inspector must have direct access to the
surface being inspected.
• Surface finish and roughness can affect
inspection sensitivity.
• Post cleaning of acceptable parts or materials
is required.
• Chemical handling and proper disposal is
required.

47. TYPES OF PENETRANT MATERIALS
 Type 1 - Fluorescent Penetrants: High sensitive,
comes usually green in color and fluoresce
brilliantly under ultraviolet light.
 Type 2 - Visible Penetrants : Less sensitive,
usually red in color, viewed under adequate
white light. less vulnerable to contaminants.
 Type 3 – Dual mode penetrants : Viewed under
black light or white light.

48. The Type- I , Penetrant have five sensitivity
levels:-
 Level ½ - Ultra Low Sensitivity
 Level 1 - Low Sensitivity
 Level 2 - Medium Sensitivity
 Level 3 - High Sensitivity
 Level 4 - Ultra-High Sensitivity

49. Before selection of a type of penetrant
method, we must have a knowledge of
• Surface condition of the work piece being
inspected
• Characteristics of the flaws to be detected
• Time and place of inspection
• Size of the work piece
• Sensitivity required
• Materials cost, number of parts, size of area
requiring inspection, and portability.

50. Penetrants are classified on the basis
of penetrant type
• Type I: Fluorescent
• Type II: Visible
Method A: Water washable
Method B: Post emulsifiable-
lipophilic
Method C: Solvent removable
Method D: Post emulsifiable-
hydrophilic

51. Application of Penetrant
By
• Flowing
• Brushing
• Swabbing
• Dipping
• Spraying
Work pieces should not be submerged during the
entire penetrant dwell time. Heating is also not
recommended because volatization, difficulty in
washing, and decrease in fluorescence can occur.

52. Water-washable penetrant (method A)
• Designed so that the penetrant is directly
water washable from the surface of the work
piece.
• It is a self emulsifying penetrant.
• It is susceptible to over washing.

53. quality control
• The wash temperature, pressure and time are three parameters that are
typically controlled in penetrant inspection process specification.
• A coarse spray or an immersion wash tank with air agitation is often used.
• When the spray method is used, the water pressure is usually limited to
276 kN/m2 (40 psi).
• The temperature range of the water is usually specified as a wide range
(e.g.. 10 to 38oC (50 to 100oF) in AMS 2647A.)
• some penetrants can fade at high temperatures due to dye vaporization or
sublimation.
• To prevent harming the penetrant material, drying temperature should be
kept to under 71oC.
• In a fluorescent penetrant inspection, the amount of penetrant brought to
the surface by developer must exceed the dye's thin film threshold of
fluorescence, or the indication will not fluoresce.

54. Post-emulsifiable penetrants
• Emulsifiers are liquids used to render excess penetrant on
the surface of a work piece water washable.
• Method B, lipophilic emulsifiers: oil based, are used as
supplied in ready-to-use form, and function by diffusion.
• work with both a chemical and mechanical action.
• mechanical action remove excess penetrant as the mixture
drains from the part
• In Chemical action, the emulsifier diffuses into the
remaining penetrant and the resulting mixture is easily
removed with a water spray.
• Water content (method B, lipophilic) Monthly Not to
exceed 5%

55. Emulsifiers
• Method D, hydrophilic emulsifiers are water
based and are usually supplied as concentrates
that are diluted in water to concentrations of 5 to
30% for dip applications and 0.05 to 5% for spray
applications.
• Hydrophilic emulsifiers function by displacing
excess penetrant from the surface of the part by
detergent action.
• Hydrophilic emulsifier is slower acting than the
lipophilic emulsifier Concentration (method D,
hydrophilic) Weekly Not greater than 3% above
initial concentration

56. Hydrophilic emulsifiers
• The major advantage of hydrophilic emulsifiers is
that they are less sensitive to variation in the
contact and removal time.
• It is more sensitive than the lipophilic post
emulsifiable.
• No diffusion takes place
• Work with both a chemical and mechanical
action.
• Emulsification Time: ranges from approximately
30 s to 3 min.

57. Prerinse
• When using method D (hydrophilic), a coarse water spray pre-rinse is
needed to assist in penetrant removal and to reduce contamination of the
emulsifier.
• Hydrophilic emulsifiers are water based , water contamination is not a
problem.
• Water contamination of the lipophilic emulsifier is always a potential
problem due to the nature of the process. Generally 5% water
contamination can be tolerated.
• Contamination is not as a critical problem with post emulsifiable
penetrant because water is usually not miscible and will separate from the
penetrant.
• A coarse water spray is recommended, using a pressure of 275 to 345 kPa
(40 to 50 psi).
• The pre-rinse water temperature should be 10 to 40 °C (50 to 100 °F).
• The pre-rinse time should be kept to a minimum (that is, 30 to 90 s)
because the purpose is to remove excess penetrant so that the emulsifier
does not become contaminated quickly.
• Rinse time should be determined experimentally for specific work pieces;
it usually varies from 10 s to 2 min.

58. Drying
• Drying is best done in a recirculating hot-air drier
that is thermostatically controlled.
• The temperature in the drier is normally between
65 and 95 °C (150 and 200 °F).
• The temperature of the work pieces should not
be permitted to exceed 70 °C (160 °F).
• Excessive drying at high temperatures can impair
the sensitivity of the inspection.
• Because drying time will vary, the exact time
should be determined experimentally for each
type of work piece.

59. Penetrant Removal Process
• Washing is used to define for water washable
• Rinsing is used for method B and D penetrant
• There are no of factors that influence spray rinse :-
• The size of water droplet: A course droplet size
provides optimum removal because it increase the
mechanical force.
• Water pressure:-10-40 psi
• Water temperature:- 10-38 degree celcious
• Spray angle :- 45-75 degree is most effective.
• Nozzle to part distance :- 6-24” are acc and provide a
uniform rate of removal.
Washing/Rinsing is best with a fan shaped course spray. It
should stop once an acc background level is reached.

60. Post-emulsifiable penetrants
(methods B and D)
• Designed to ensure the detection of minute flaws in some materials.
• Separate emulsification is required to remove the penetrant.
• The danger of over washing the penetrant out of the flaws is reduced.
• These methods are the most reliable for detecting minute flaws.
• Application of lipophilic emulsifier is done by dipping. Brush on or spray on
application is not permitted because it would mechanically mix the
emulsifier into the penetrant.
• Pre-rinsing prior to application of Hydrophilic emulsifier is recommended
because it is incompatible with water.
• Concentration of hydrophilic emulsifier in spray application is usually 0.5-
1% by volume; however, up to 5% may be used.
• Concentration of hydrophilic emulsifier by immersion application is usually
5-35% by volume depending on the manufacturer direction for mixing. A
slight agitation is necessary.
• Solvent removers never be sprayed or flowed on because excessive
solvent will dilute entrapped penetrant, which degrade the process.

61. Methods B and D
1. pre-clean part, 2. apply penetrant and allow to dwell,
3. pre-rinse to remove first layer of penetrant, 4. apply
emulsifier and allow contact for specified time, 5. rinse
to remove excess penetrant, 6. dry part, 7. apply
developer and allow part to develop, and 8. inspect
Processing steps

62. Solvent-removable penetrant
(method C)
• Used to inspect only a localized area of a work
piece
• Inspect a work piece at the site rather than on a
production inspection basis.
• Normally, the same type of solvent is used for pre
cleaning and for removing excess penetrant.
• This method is labor intensive.
• When properly conducted and when used in the
appropriate applications, the solvent-removable
method can be one of the most sensitive
penetrant methods available.

63. Solvent-removable penetrant
(method C)
• The use of excessive amounts of solvent must
be avoided.

64. Solvent Cleaner/Removers
• Remove excess surface penetrant through direct solvent
action.
• There are two basic types of solvent removers:
• flammable and nonflammable.
• Flammable cleaners are essentially free of halogens but are
potential fire hazards.
• Nonflammable cleaners are widely used. However, they do
contain halogenated solvents, which may render them
unsuitable for some applications.
• Wipe the surface of the part with a clean dry cloth or paper
towel. Make only a single pass, then fold the cloth and
moisten with solvent to provide a clean surface for each
succeeding wipe. Repeat this procedure until there is little
or no trace of penetrant.

65. Solvent Cleaner/Removers
• Excess surface penetrant is removed by
wiping, using lint-free cloths slightly
moistened with solvent cleaner/remover.
• It is not recommended that excess surface
penetrant be removed by flooding the surface
with solvent cleaner/remover,
• Because the solvent will dissolve the
penetrant within the defect and indications
will not be produced

66. Penetrant Application
• Penetrants can be applied by :-
• Immersing
• Spraying
• Brushing
• The emulsifier on to the part is not
recommended by brushing either because the
bristles of the brush may force emulsifier into
discontinuities, causing the entrapped penetrant
to be removed.

67. Penetrant Application and Dwell Time
There are basically two dwell mode options:-
• immersion-dwell (keeping the part immersed in the
penetrant during the dwell period) and
• drain-dwell (letting the part drain during the dwell period).
• Prior to a study by Sherwin, the immersion-dwell mode
was generally considered to be more sensitive but
recognized to be less economical because more penetrant
was washed away and emulsifiers were contaminated more
rapidly. The reasoning for thinking this method was more
sensitive was that the penetrant was more migratory and
more likely to fill flaws when kept completely fluid and not
allowed to lose volatile constituents by evaporation.

68. Penetrant Application and Dwell Time
• However, Sherwin showed that if the specimens
are allowed to drain-dwell, the sensitivity is
higher because the evaporation increases the
dyestuff concentration of the penetrant on the
specimen.
• Sherwin also cautions that the samples being
inspected should be placed outside the penetrant
tank wall so that vapors from the tank do not
accumulate and dilute the dyestuff concentration
of the penetrant on the specimen.

69. Dwell Time
The time required to fill a flaw depends on a number of
variables which include the following:
• The surface tension of the penetrant.
• The contact angle of the penetrant.
• The dynamic shear viscosity of the penetrant
• The atmospheric pressure at the flaw opening.
• The capillary pressure at the flaw opening.
• The pressure of the gas trapped in the flaw by the
penetrant.
• The radius of the flaw or the distance between the flaw
walls.
• The density or specific gravity of the penetrant.

70. Dwell Time
• Microstructural properties of the penetrant. AMS
2647A requires that the dwell time for all aircraft and
engine parts be at least 20 minutes, while ASTM E1209
only requires a five minute dwell time for parts made
of titanium and other heat resistant alloys.
• Generally, there is no harm in using a longer penetrant
dwell time as long as the penetrant is not allowed to
dry.
• Deutsch makes about dwell time is that if the elliptical
flaw has a length to width ratio of 100, it will take the
penetrant nearly ten times longer to fill than it will a
cylindrical flaw with the same volume

71. Quality Control of Penetrant
• Deterioration of new penetrants primarily
results from aging and contamination.
• the water content of water washable
penetrants must be checked regularly. Water-
based, water washable penetrants are
checked with a refractometer.
• Non-water-based, water washable penetrants
are checked using the procedure specified in
ASTM D95 or ASTM E 1417.

72. Quality check of penetrant materials
Penetrant
• Fluorescent brightness Quarterly Not less than 90%of reference standard
• Sensitivity Monthly Equal to reference standard
• Removability (method A water wash only) Monthly Equal to reference
standard
• Water content (method A water wash penetrant only)-Monthly Not to
exceed 5%
• Contamination Weekly No noticeable tracers
Emulsifiers
• Removability Weekly Equal to reference standard
• Water content (method B, lipophilic) Monthly Not to exceed 5%
• Concentration (method D, hydrophilic) Weekly Not greater than 3% above
initial concentration
• Contamination Weekly No noticeable tracers
Developers
• Dry-developer form Daily Must be fluffy, not caked

73. Quality check of penetrant materials
Dry Developer
• Contamination Daily Not more than ten fluorescent specks
observed in a 102 mm (4 in.) circle of sample
Aqueous (soluble and suspended) developer
• Wetting/coverage Daily Must be uniform/wet and must coat part
• Contamination Daily Must not show evidence of fluorescence
contaminates
• Concentration Weekly Concentration shall be maintained as
specified.
Other
• Black lights Daily Minimum 1000 microwatt/cm2 at 381 mm (15
in.)
• White light Weekly Minimum 200 lx (20 ftc)
• System performance Daily Must equal reference standards

74. Physical and Chemical Characteristics
• Chemical stability and uniform physical consistency
• A flash point not lower than 95 °C (200 °F);
• Penetrants that have lower flash points constitute a
potential fire hazard.
• A high degree of wettability
• Low viscosity to permit better coverage and minimum
drag out
• Ability to penetrate discontinuities quickly and
completely
• Sufficient brightness and permanence of color

75. Physical and Chemical Characteristics
• Chemical inertness with materials being
inspected and with containers
• Low toxicity to protect personnel
• Slow drying characteristics
• Ease of removal
• Inoffensive odor
• Low cost
• Resistance to ultraviolet light and heat fade

76. Chemical stability
• Tendency of a material to resist change or
decomposition due to internal reaction, or
due to the action of air, heat, light, pressure,
etc.
• The properties of penetrant materials that are
controlled by AMS 2644 and MIL-I-25135E
include flash point, surface wetting capability,
viscosity, color, brightness, ultraviolet stability,
thermal stability, water tolerance, and
removability.

77. ultraviolet & Thermal stability
Excessive heat:
1. evaporates the more volatile constituents which
increases viscosity and adversely affects the rate
of penetration.
2. alters wash characteristics.
3. "boils off" chemicals that prevent separation
and gelling of water soluble penetrants.
4. kills the fluorescence of tracer dyes.
2. Generally, thermal damage occurs when
fluorescent penetrant materials are heated
above 71oC

78. Temperature
• The temperature of the penetrant materials and the part being
inspected should be from 10 to 49oC (80 to 120oF) .
• Surface tension of most materials decrease as the temperature
increases, raising the temperature of the penetrant will increase the
wetting of the surface and the capillary forces.
• Raising the temperature will also raise the speed of evaporation of
penetrants, which can have a positive or negative effect on
sensitivity.
• The impact will be positive if the evaporation serves to increase the
dye concentration of the penetrant trapped in a flaw up to the
concentration quenching point and not beyond.
• Freezing can cause separation to occur and exposure to high
temperature for a long period of time can affect the brightness of
the penetrant dyes.

79. Flash point
• The evaporation of the volatile constituents of
penetrants can alter their chemical and
performance characteristics,
• Resulting in changes in inherent brightness,
removability, and sensitivity.
• Liquid penetrant materials qualified to MIL-I-
25135D (and subsequent revisions) have a flash
point requirement of a minimum of 95 °C.
• Dilution of the penetrant liquid will affect the
concentration of the dye and reduce the
dimensional threshold of fluorescence.

80. A penetrant must:
• spread easily over the surface of the material being
inspected to provide complete and even coverage.
• be drawn into surface breaking defects by capillary
action.
• remain in the defect but remove easily from the
surface of the part.
• remain fluid so it can be drawn back to the surface of
the part through the drying and developing steps.
• be highly visible or fluoresce brightly to produce easy
to see indications.
• not be harmful to the material being tested or the
inspector.

81. Penetrant Color and Fluorescence
• LPI materials fluoresce because they contain one or more dyes that absorb
electromagnetic radiation over a particular wavelength and the absorption
of photons leads to changes in the electronic configuration of the
molecules. Since the molecules are not stable at this higher energy state,
they almost immediately re-emit the energy.
• Two different fluorescent colors can be mixed to interact by a mechanism
called cascading.
• The emission of visible light by this process involves one dye absorbing
ultraviolet radiation to emit a band of radiation that makes a second dye
glow.
• The measurement of fluorescent brightness is detailed in ASTM E-1135,
"Standard Test Method for Comparing the Brightness of Fluorescent
Penetrants.“
• When using fluorescent penetrants, a brightness comparison per the
requirements of ASTM E 1417 is also often required. This check involves
placing a drop of the standard and the in-use penetrants on a piece of
Whatman #4 filter paper and making a side by side comparison of the
brightness of the two spots under UV light.

82. Penetrant Color and Fluorescence
• The degree of fluorescence response, under a given
intensity of ultraviolet radiation, is dependent on the
absorption of ultraviolet radiation, which in turn depends
on dye concentration and film thickness.
• Beer's Law states that the intensity of the transmitted
energy is directly proportional to the intensity of the
incident light and varies exponentially with the thickness of
the penetrant layer and its dye concentration. Therefore,
when the dye concentration is increased, the brightness of
the thin layer of penetrant generally increases.
• A Meniscus-Method Apparatus can be used to measure the
dimensional threshold of fluorescence.

83. Function of developers
• Increase the brightness intensity of
fluorescent indications and the visible contrast
of visible-penetrant indications.
• The developer also provides a blotting action,
which serves to draw penetrant from within
the flaw to the surface, spreading the
penetrant and enlarging the appearance of
the flaw.
• Decreases inspection time by hastening the
appearance of indications.

84. Developer properties
• The developer must be adsorptive to maximize
blotting.
• It must have fine grain size and a particle shape
that will disperse and expose the penetrant at a
flaw to produce strong and sharply defined
indications of flaws.
• It must be capable of providing a contrast
background for indications when color-contrast
penetrants are used.
• It must be easy to apply.
• It must form a thin, uniform coating over a
surface.

85. Developer properties
• It must be non fluorescent if used with fluorescent
penetrants
• It must be easy to remove after inspection
• It must not contain ingredients harmful to parts being
inspected or to equipment used in the inspection
• It must not contain ingredients harmful or toxic to the
operator
• The fine developer particles both reflect and refract the
incident ultraviolet light, allowing more of it to interact with
the penetrant, causing more efficient fluorescence. The
developer also allows more light to be emitted through the
same mechanism. This is why indications are brighter than
the penetrant itself under UV light.

86. Developer Forms
• Form A, dry powder
• Form B, water soluble
• Form C, water sus-pendible
• Form d , Non-aqueous Type 1 Fluorescent
(Solvent Based)
• Form e ,Non-aqueous Type 2 Visible Dye
(Solvent Based)

87. Form A, dry powder
• Most common application by dusting or spraying.
• Only a portion of the surface of a large part,
applying with a soft brush is adequate.
• Dry developer does not provide a uniform white
background as the other forms of developers do
• Least sensitive but it is inexpensive to use and
easy to apply.
• Excessive powder can be removed by gently
blowing on the surface with air not exceeding 35
kPa or 5 psi.(max 20psi) or by shaking/gentle
tapping

88. Form A, dry powder
• Widely used with fluorescent penetrants, but should not be
used with visible dye penetrants because they do not
produce a satisfactory contrast coating on the surface of
the work piece.
• It should be light and fluffy to allow for ease of application
and should cling to dry surfaces in a fine film.
• powders should not be hygroscopic, and they should
remain dry.
• If they pick up moisture when stored in areas of high
humidity, they will lose their ability to flow and dust easily,
and they may agglomerate, pack, or lump up in containers
or in developer chambers.
• Dry-developer form inspected daily Must be fluffy, not
caked.

89. Safety requirement
• Handled with care because it can dry the skin
and irritate the lining of the air passages,
causing irritation.
• Rubber gloves and respirators may be
desirable if an operator works continuously
with this.

90. Water-soluble developers (form B)
• It can be used for both type I or type II
penetrants.
• It is not recommended for use with water-
washable penetrants, because of the potential to
wash the penetrant from within the flaw if the
developer is not very carefully controlled.
• Supplied as a dry powder concentrate
• Dispersed in water from 0.12 to 0.24 kg/L
• The bath concentration is monitored for specific
gravity with hydrometer.
• They should never be applied with a brush.

91. Water-suspendible developers (form C)
• It can be used with either fluorescent (type I) or visible
(type II) penetrants.
• With fluorescent penetrant, the dried coating of developer
must not fluoresce, nor may it absorb or filter out the black
light used for inspection.
• supplied as a dry powder concentrate, which is then
dispersed in water in recommended proportions, usually
from 0.04 to 0.12kg/L.
• Specific gravity checks should be conducted routinely, using
a hydrometer to check the bath concentration.
• aqueous wet developers can cause leaching and blurring of
indications when used with water-washable penetrants.

92. Water-suspendible developers (form C)
• It contains dispersing agents to help retard
settling and caking as well as inhibitors to
prevent or retard corrosion of work pieces
• It contains biocides to extend the working life
of the aqueous solutions.
• It contains wetting agents to ensure even
coverage of surfaces and ease of removal after
inspection.
• They should never be applied with a brush.

93. Drying
• Drying is achieved by placing the wet but well drained part
in a recirculating, warm air dryer that is thermostatically
controlled with the temperature held in between 65-95
degree celcious.
• The temperature of the work piece should not be
permitted to exceed 70 degree celcious(160 F) .
• Excessive drying at high temp can impair the sensitivity.
• If the parts are not dried quickly, the indications will be
blurred and indistinct.
• Properly developed parts in water soluble developer will
have an even, pale white coating over the entire surface.
• The surface of a part coated with a water suspendable
developer will have a slightly translucent white coating.

94. Advantages
• Not require any agitation in water soluble but
water suspendable developers require frequent
stirring or agitation to keep the particles from
settling out of suspension.
• Applied prior to drying, thus decreasing the
development time
• The dried developer film on the work piece is
completely water soluble and is thus easily and
completely removed by simple water rinsing.

95. Non-aqueous solvent-suspendible
developers (form D)
• used for both the fluorescent and the visible
penetrant process.
• This coating yields the maximum white color
contrast with the red visible penetrant indication
and extremely brilliant fluorescent indication.
• Supplied in the ready-to-use condition and
contain particles of developer suspended in a
mixture of volatile solvents.
• It also contain surfactants in a dispersant whose
functions are to coat the particles and reduce
their tendency to clump or agglomerate.

96. Non-aqueous solvent-suspendible
developers
• Most sensitive form of developer used with type I
because the solvent action contributes to the
absorption and adsorption mechanisms.
• It enters the flaw and dissolves into the
penetrant. This action increases the volume and
reduces the viscosity of the penetrant.
• There are two types of solvent-base developers:
• nonflammable (chlorinated solvents) and
flammable (non-chlorinated solvents). Both types
are widely used.

97. Non-aqueous solvent-suspendible
developers
• Since the solvent is highly volatile, forced drying is not required.
• A non-aqueous developer should be applied to a thoroughly dried
part to form a slightly translucent white coating.
• If the spray produces spatters or an uneven coating, the can should
be discarded.
• Plastic or lacquer developers are special developers that are
primarily used when a permanent record of the inspection is
required.
• Application by spraying either with aerosol container or by
electrostatic method. Dipping, pouring, brushing are not suitable
for applying solvent suspendible developer.
• Min recommended developing time is 10 min regardless of the
developer used. The developing time begins immediately after
application of the developer.

98. FUSIBLE WAX DEVELOPER
• A high-sensitivity, high-resolving power inspection penetrant developer in
which the: active developing ingredient is a waxy substance which is a
solid or near-solid at room temperature, but which becomes fluid at
slightly elevated temperatures.
• The waxy developer material may be dissolved in a suitable carrier liquid
such as water or other inert volatile solvent, and is deposited on test parts
by dipping, brushing or spraying, and allowing the carrier liquid to
evaporate.
• When heat is applied to the test parts, during oven drying or by heating
subsequent to air-drying, the waxy developer layer becomes a fluid, and a
liquid-film dilution expansion type development of penetrant entrapments
in surface defects then takes place.
• When the test parts cool to room temperature, the fluid waxy layer, which
now contains developed defect indications, solidifies and prevents
excessive bleeding and migration of the indications.

99. Sensitivity ranking of developers
Ranking
1
2
3
4
5
6
7
8
9
10
Developer Form
Nonaqueous, Wet Solvent
Plastic Film
Water-Soluble
Water-Suspendable
Water-Soluble
Water-Suspendable
Dry
Dry
Dry
Dry
Method of Application
Spray
Spray
Spray
Spray
Immersion
Immersion
Dust Cloud (Electrostatic)
Fluidized Bed
Dust Cloud (Air Agitation)
Immersion (Dip)
Sensitivity ranking of developers per the Nondestructive Testing Handbook.
Sensitivity Ranking (highest to lowest) Developer Form Application Technique.

100. .
Developer Advantages Disadvantages
Dry
Indications tend to remain brighter and more distinct over time
Easily to apply
Does not form contrast background so cannot be used with visible systems
Difficult to assure entire part surface has been coated
Soluble
Ease of coating entire part
White coating for good contrast can be produced which work well for both visible
and fluorescent systems
Coating is translucent and provides poor contrast (not recommended for visual
systems)
Indications for water washable systems are dim and blurred
Suspendable
Ease of coating entire part
Indications are bright and sharp
White coating for good contrast can be produced which work well for both visible
and fluorescent systems
Indications weaken and become diffused after time
Nonaqueous
Very portable
Easy to apply to readily accessible surfaces
White coating for good contrast can be produced which work well for both visible
and fluorescent systems
Indications show-up rapidly and are well defined
Provides highest sensitivity
Difficult to apply evenly to all surfaces
More difficult to clean part after inspection

101. Stationary Inspection Equipment
The type of equipment most frequently used in
fixed installations consists of a series of modular
subunits.
• Drain and/or dwell stations
• Penetrant and emulsifier stations
• Pre- and post-wash stations
• Drying station
• Developer station
• Inspection station
• Cleaning stations

102. Developer
• Developer Station. The type and location of the
developer station depend on whether dry or wet
developer is to be used.
• For dry developer, the developer station is
downstream from the drier, but for wet
developer it immediately precedes the drier,
following the rinse station.
• For wet, there should also be a rack or conveyor
on which parts can rest after dipping. This will
permit excess developer to run back into the
tank.

103. Developer
• Suspendible developer baths settle out when not in use;
therefore, a paddle for stirring should be provided.
Continuous agitation is essential because the settling rate is
rapid.
• Pumps are sometimes incorporated into the developer
station for flowing the developer over large work pieces
through a hose and nozzle and for keeping the developer
agitated.
• In automatic units, special methods of applying developer
are required. Flow-on methods are frequently used.
• This technique requires a nozzle arrangement that permits
the work pieces to be covered thoroughly and quickly.

104. Inspection Station
• Inspection station is simply a worktable on which work
pieces can be handled under proper lighting.
• For fluorescent methods, the table is usually
surrounded by a curtain or hood to exclude most of the
white light from the area.
• For visible-dry penetrants, a hood is not necessary.
• Generally, black (ultraviolet) lights (100 W or greater)
are mounted on brackets from which they can be lifted
and moved about by hand.
• Because of the heat given off by black lights, good air
circulation is essential in black light booths.

106. Black light Intensity
• UV ranging from 180 to 400 nanometers.
• Recommended black light intensity is 1000 to 1600
microwatt/cm2.
• The intensity of the black light should be verified at regular
intervals by the use of a suitable black light meter such as a
digital radiometer.
• Warm up prior to use--generally for about 10 min.
• UV light must be warmed up prior to use and should be on
for at least 15 minutes before beginning an inspection.
• The inspector should allow time for adapting to darkness; a
1-min period is usually adequate.
• White light intensity should not exceed 20 lx (2 ftc) to
ensure the best inspection environment.
• Switching the lamp on and off, shorten the bulb life.

107. Black light Intensity
• Penetrant dyes are excited by UV light of 365nm
wavelength and emit visible light somewhere in
the green-yellow range between 520 and 580nm.
• The source of ultraviolet light is often a mercury
arc lamp with a filter.
• UV emissions below 310nm include some
hazardous wavelengths.
• Bulbs lose intensity over time. In fact, a bulb that
is near the end of its operating life will often have
an intensity of only 25% of its original output.

108. Effect of UV light
• Excessive UV light exposure can cause painful
sunburn, accelerate wrinkling and increase the
risk of skin cancer.
• UV light can cause eye inflammation, cataracts,
and retinal damage
• Skin and eye damage occurs at wavelengths
around 320 nm and shorter which is well below
the 365 nm wavelength, where penetrants are
designed to fluoresce.
• UV lamps sold for use in LPI application are
almost always filtered to remove the harmful UV
wavelengths.

109. visible light intensity
• visible light intensity should be adequate to
ensure proper inspection; 320 to 540 lx (30 to 50
ftc) is recommended.
• Lighting intensity should be verified at regular
intervals by the use of a suitable white light
meter such as a digital radiometer & it should be
calibrated at least every six months.
• Ultraviolet light measurements should be taken
using a fixture to maintain a minimum distance of
15 inches from the filter face to the sensor

110. Dimensional Threshold of
Fluorescence
• The performance of penetrants based on the
physical constraints of the dyes can be predicted
using Beer's Law equation. This law states that
the absorption of light by a solution changes
exponentially with the concentration of the
solution.
• This equation does not hold true when very thin
layers are involved but works well to establish
general relationships between variables.
• It = Io x e-lCt

111. Dimensional Threshold of
Fluorescence
Where:
It = Transmitted light intensity
Io = Incident light intensity
e = Base of natural log (2.71828)
l = Absorption coefficient per unit of concentration
C = Dye concentration
t = Thickness of the absorbing layer controlled to a
certain degree by the concentration of the
fluorescent tracer dye in the penetrant

112. Removability
• Dilution of the penetrant liquid will affect the
concentration of the dye and reduce the dimensional
threshold of fluorescence.
• The adhesive forces of the penetrant must be weak
enough that they can be broken by the removal
methods used. However, in order for the penetrant to
have good surface wetting characteristics, the adhesive
forces (forces of attraction between the penetrant and
the solid surface being inspected) must be stronger
than the cohesive forces (forces holding the liquid
together). Proper formulation of the penetrant
materials provides the correct balancing of these
forces.

113. Post cleaning
• Some residue will remain on work pieces after
penetrant inspection is completed.
• Residues can result in the formation of voids
during subsequent welding or unwanted stop-
off in brazing,
• In the contamination of surfaces (which can
cause trouble in heat treating), or in
unfavorable reactions in chemical processing
operations.

114. Post cleaning
• ultrasonic cleaning may be the only satisfactory
way of cleaning deep crevices or small holes.
However, solvents or detergent-aided steam or
water is almost always sufficient.
• The use of steam with detergent is probably the
most effective of all methods.
• It has a scrubbing action that removes
developers, the heat and detergent remove
penetrants, it leaves a work piece hot enough to
promote rapid, even drying, and it is harmless to
nearly all materials.

115. Post cleaning
• Vapor degreasing is very effective for
removing penetrants, but it is practically
worthless for removing developers.
• It is frequently used in combination with
steam cleaning.
• If this combination is used, the steam cleaning
should always be done first because vapor
degreasing bakes on developer films.

116. Probability of detection
In general, penetrant inspections are more
effective at finding
• small round defects than small linear defects
• deeper flaws than shallow flaws
• flaws with a narrow opening at the surface
than wide open flaws
• flaws on smooth surfaces than on rough
surfaces

117. Indications
Typical source of contaminations are :-
 Penetrant on hands of operators
 Contamination of wet and dry developer
 Penetrant rubbing off an indication on the specimen to a clean
portion of the surface of another specimen
 Penetrant spots on the inspection table.
Non-relevant indications include those that appear on articles that are
Press fitted , keyed, splined, riveted or spot welded together and those
appearing on casting as a result of loosely adherent scale or a rough
surface due to burned in sand.
 The most common source of false indication is poor washing of
water washable and post emulsified penetrants.
 Penetrant inspection provides only indirect indications or flaws, it
cannot always be determined at first glance whether an indication
is real, false or non-relevant. A real indication is caused by
undesirable flaw such as crack.

118. True Indication

119. Flaws revealed by PT
• Hot tears, shrinkage crack open to the surface.
• Cold shuts,folds,inclusion,laps open to surface
• Crater cracks – characteristics star shaped
• Pipe- irregular shape
• Grinding cracks- tight shallow, random
• Fatigue crack-tight
• Stress corrosion cracks- tight to open
Non-relevant Indication
• weld spatter, scuff marks, press-fit, interference,
braze runoff, burrs etc.

120. Inspection
• If developer films are too thick, if penetrant
bleed-out appears excessive, if the penetrant
background is excessive, the work piece should
be cleaned and reprocessed.
• One of the most accurate ways of measuring
indications is to lay a flat gage of the maximum
acceptable dimension of discontinuity over the
indication. If the indication is not completely
covered by the gage, it is not acceptable.

121. Evaluation
• Each indication that is not acceptable should be evaluated. It may be
worse than it appears, it may be false or real.
Common method of evaluation includes:-
• Wipe the area of indication with a small brush or clean by cloth that is
dampened with a solvent.
• Dust the area with a dry powder or spray it with a light coat of non-
aqueous developer.
• Re-measure under appropriate lighting for the type of penetrant used.
Generally quality standards for the type of discontinuity detected by
penetrant are established by following methods:
 Adoption of standards that have been successfully used for similar work
pieces.
 Evaluation of the results of penetrant inspection by Destructive
Examination
 Experimental and theoretical stress analysis

122. ASTM STANDARDS
• ASTM E 165 Standard Practice for Liquid-Penetrant Inspection Method
• ASTM E 1208 Standard Method for Fluorescent Liquid-Penetrant Examination
Using the Lipophilic Post-Emulsification
• Process
• ASTM E 1209 Standard Method for Fluorescent-Penetrant Examination Using the
Water-Washable Process
• ASTM E 1210 Standard Method for Fluorescent-Penetrant Examination Using the
Hydrophilic Post-Emulsification
• Process
• ASTM E 1219 Standard Method for Fluorescent-Penetrant Examination Using the
Solvent-Removable Process
• ASTM E 1220 Standard Method for Visible-Penetrant Examination Using the
Solvent-Removable Process
• ASTM E 1135 Standard Test Method for Comparing the Brightness of Fluorescent
Penetrants
• AMS 2647 Fluorescent Penetrant Inspection--Aircraft and Engine Component
Maintenance
• ASME SEC V ASME Boiler and Pressure Vessel Code Section V, Article 6
• MIL-STD-6866 Military Standard Inspection, Liquid Penetrant
• MIL-STD-410 Nondestructive Testing Personnel Qualifications & Certifications
• MIL-I-25135 Inspection Materials, Penetrant

123. If you have any queries, can contact
@www.omndt.org or drop mail to
omndtcenter@rediffmail.com
Thanks
MAHESH PANDIT
ASNT NDT L-III