This document provides information on dye penetrant testing (DPT), including: 1. DPT uses capillary action to draw liquid penetrants into surface discontinuities, then uses developers to draw the penetrant back out for visualization. 2. The basic DPT process involves cleaning, applying penetrant, removing excess, applying developer, and visual inspection. 3. Proper selection of penetrants and developers depends on factors like material type, discontinuity size, and required sensitivity. Post-emulsifiable penetrants provide high sensitivity but require an extra processing step.

1. DYE PENETRANT TESTING(1850)
BY MANISH SHARMA

2. LIQUID PENETRANT INSPECTION (LPI/LPE/LPT)
DYE PENETRANT TESTING (DPT/ DPE/DPI)
PENETRANT FLAW DETECTION(PFD)
PENETRANT TESTING(PT)

3. Introduction:
Finding discontinuities open to the surface of
the material to work on the principle of capillary
action and it is applicable to both magnetic and
non magnetic materials.
Capillary action forces liquid into narrow
openings

4. Capillary Action
This is the phenomenon of a liquid rising or climbing
when confined to small openings due to surface
wetting properties of the liquid.

5. Basic Process of PT
1) Clean & Dry Component
2) Apply Penetrant
3) Remove Excess
4) Apply Developer
5) Visual Inspection

6. Basic Principle:
The liquid penetrant is applied on the surface of the
component to be tested. The penetrant enters into the
discontinuities by capillary action, if the discontinuity is
small or narrow, the capillary action assists the
penetration, If the discontinuity is large in nature, the
penetrant seep through the discontinuity. After sufficient
time has passed for the penetrant to enter the surface
discontinuity, The excess penetrant on the surface is
removed by washing or some other convenient manner.

7. But the penetrant in the discontinuity is
allowed to remain, Then developer is applied to the test
surface, the blotting action of the developer draws the
penetrant from the discontinuity & the penetrant
appears on the surface of the specimen as an
indication.

8. Requirements:
1. Job (Smooth, Non porous metal)
2. Approved Procedure
3. D.P. materials
• Cleaner • Penetrant
• developer • Lint free cloths/clean cloths
4. Light arrangement
• Ordinary light(sunLight or 100 Watt Bulb etc.)
• Black light ( U.V.Light)
5. Reference Block
• Aluminium Crack Block
• Nickel Chromium panel.
6. Technician(SNT-TC-1A)

10. NOTE: Materials that are commonly
inspected using LPI include the following.
1. Metals ( AL, CU, Steel, titanium etc. )
2. Glass
3. Many ceramic materials
4. Rubber
5. plastic

11. Basic Theory of Penetration:
Penetration (ability to penetrate)
↓depends upon
Wettability(ability to wet)
↓ depends upon
Contact Angle(the angle between
solid material and liquid or gas.

12. If Contact angle is less than 90⁰ then
wettability is very good.
If contact angle is 90⁰ then wettability is fair
(average good)
If Contact angle > 90⁰ then poor wettability.

13. Contact angles depends upon.
1. Surface Tension(T=F/L) The molecules in a
liquid are attracted to each other.
2. Viscosity (resistance to flow the liquid) & it is
affected by temp & pressure.

14. Steps in DPT
1. Precleaning (surface preparation)
Liquid penetrant test is based on ability of the
penetrant to enter into the surface discontinuity/
Discontinuities The specimen to be tested must be
clean and free from foreign matters that may covers
or block the discontinuity.

15. surface preparation

16. Types of Contaminant:
1. Paint on the specimen .
2. Oils, greases & other chemical impurities.
3. Dirt or dust that gets settled on the surface of
the job.
4. Polising component & scales from heat
treatment or welding.
5. Welding flux & weld spatters.

17. Cleaning Methods:
1. Mechanical Method: Mechanical cleaning
means removal of contaminants from the
surface by various mechanical operations.
(A) Abrasive tumbling: Removing light scales,
welding flux, rust etc.
It should not be used on soft materials such
as Al, Mg,etc.
(B) Wire Brushing: Removing light deposits of
scales, flux & rust.

18. (C)High pressure water & steam: we use water
and detergent to removes types of contaminants
Such as cutting oil, grease, chips, polishing
components.
(D) Ultrasonic cleaning: we dissolved detergent
in water to removes adherent shop soils in large
quantities from small parts by dipping the part in a
ultrasonic tank. The frequency of ultrasonic
vibration is 30 to 40 KHz is generally used but some
times higher frequency may be used.

19. CHEMICAL METHOD:
1. Alkaline Cleaning: (PH > 7)
Remove typical machine shop soils such as cutting
oil, polishing components, grease & wax, metal
chips, carbon deposits used on large specimen
where hand methods are too laborious.
Alkaline solution = Caustic Soda or lime. Sodium &
potassium Hydroxide (NaOH, KOH) etc.
Cleaning method Immersion at temp (50- 95⁰) &
then water rinse or spraying usually to remove
residue.

20. 2. Acid Cleaning:
Typically known as etching used acid to remove
scales & smeared metal pieces due to machining
operation. A concentrated solution for removing
heavy scales, mild solutions for light scales.

21. 3.Solvent Cleaning Methods:
1. Solvent wiping : It is the most common method for
pre & post cleaning & must be performed in a well
ventilated area due to toxicity of the vapors.

22. 2. Penetrants:
Almost any Liquid could be penetrant
but a modern penetrant must have the
following properties.

23. 1.It should be able to easily penetrate to very fine
openings.
2. Be able to remain on the openings.
3. Not evaporate or dry up too rapidly.
4. Clean easily off the surface on which it has been
applied.
5. uniform flow property.
6. In a short time, come back out to very fine
openings.
7. Dye should be high contrast colour like
Red/Pink.

24. 8. Good wettability.
9. Can be used on any material which has a
non absorbent surface.
10. Penetrant made of dye + solvent (dye for
contrast & solvent for carrier)
11. Not be harmful to the inspector or the
material being tested.

25. Types of penetrants: It depends upon Quality,
cost, service condition & sensitivity required.
penetrants are classified which are as.
1. Solvent removal visible colour contrast.
2. Solvent removal fluorescent.
3. Water washable visible colour contrast.
4. Water washable fluorescent.
5. Post emulsiable colour contrast.
6. Post emulsiable fluorescent.

26. Post Emulsification Penetrant system:
Post emulsification penetrants have high
sensitivity it can detect miner defects, than that
of water washable & solvents removable. such
penetrants have an oil base & require an
additional processing step. An emulsifier is
applied after the penetrant had sufficient time to
be absorbed by the defects.

27. They are of two types:
1. Hydrophilic (water based)
2. Lipophilic Emulsifier (oil based)
Emulsification dwell time is from a few
seconds to several minutes typically 15 sec to 4 min.
The Emulsifier can be applied by dipping or spraying
but not by brushing . The bristles of the brush may
enter the discontinuity.

28. Advantage of post Emulsification
Penetrant:
1. High sensitivity to very fine discontinuities.
2. Penetrant easily washed with water after
emulsification.

29. Disadvantages of post Emulsifiable
penetrant:
1. It is two step process & requires additional
time in making the penetrant water washable.
2. Separate emulsifiers are required , which
raises the cost of inspection.
3. Not good on rough surface.
4. Penetrant removal is difficult in threaded
parts, holes.

30. Application of Penetrant:
1. By Brush
2. By Spray
3. By Pouring
4. By Dipping
.

31. Physical properties of a good developer:
1. Have uniform well dispersed micro particals.
2. Have Light Scattering efficiency (i.e. high back
ground contrast (white)
3. Low contact angle between developer & solid
surface.
4. Non Toxic.
5. It must be easily removable after inspection.
Developers:
The primary function of the developer is to absorb or
draw the penetrant (blotting action ) from discontinuity .

32. There are five types of developers:
1. Dry
2. Wet(Aqueous –water Soluble)
3. Wet(Aqueous-Water Suspended)
4. Solvent (Non aqueous wet)
5. Film Type

33. a. Dry Developers:
Dry developer shall be applied only to a dry
surface by a soft brush or hand powder
bulb, powder gun, etc.

34. b. Wet Developer:
Prior to applying suspension type wet developer to
the surface, the developer must be thoroughly agitate
to ensure adequate dispersion of suspended particles.
Wet developers are applied by dipping, brushing,
spraying on the part. The part is then dried in a hot air
circulating oven, but surface temp of the part (job)
shall not exceed 52⁰c.

35. c. Non Aqueous Developers: (Solvent)
Suspended
Non aqueous developer shall be applied
only to a dry surface. It shall be applied by
spraying to a thoroughly dried & cooled part.

36. d. Liquid Film Developers:
The film type developer as the name implies
to form a plastic film over a surface as it dries. It is
normally applied by spraying as with the non-
aqueous wet type developer. As the film dries it
exposed penetrant indications set (fixed) in the
pattern. The film provide a permanent record of
the discontinuity pattern.

37. Application of Developer:
1. By Brush
2. By Spray
3. By Pouring
4. By Dipping
Same as application of penetrant.

38. Development Time:
The length of time the developer is
allowed to remain on the part prior to
examination, should not be less than 10
minutes.
Permitted developing time are 2 hrs
for aqueous developers & 1 hrs for non
Aqueous developers.
“ Generally developing time is double to
dwell time of penetrant”.

39. Dwell time or Penetration time:
The period of time during which the
penetrant is permitted to remain on the
specimen is a vital part of the test. This time
is often referred to as a penetration time, or
dwell time. Normally this time is dependent
on the nature of discontinuities, surface
finish, material type & temp,Penetrant type.

40. Material Form Type of
Discontinuity
Penetration
dwell time
Developer
dwell time
Brass, Al, Mg,
Steel Bronze Ti &
High
Temperature
Alloys.
Casting & Welds
Wrought
materials
extrusions
forgings & plates
Cold shuts
Porosity, LOF,
Cracks
Laps, Cracks
(all forms)
5
10
10
10
Plastic All Forms Cracks 5 10
Glass All Forms Cracks 5 10
Ceramics All Forms Crack 5 10
Carbide Tipped
tools
Porosity Cracks 5 10

41. The above table is valid for temperature
range= 10⁰ - 52⁰C .For temperature from 5⁰c
up to 10⁰c minimum penetrant dwell time
shall be 2 times the value listed.

42. Excess Penetrant Removal:
The excess penetrant removal technique depends
upon the type of penetrant used e.g.
1. Water washable
2. Post Emulsifiable
3. Solvent Removable

43. 1. Water washable penetrants:
After the required penetration time, the
excess penetrant is usually removed by coarse spray
of water. It can be washed off manually or by the use
of automatic or semi automatic water spray
equipments or by immersion.
This method is the easiest to employ & most
cost effective when inspecting large areas.

44. Used (Parameters)
a) The temp of the water should be relatively constant &
should be maintained within the range of (10⁰C – 38⁰C)
b) Spray rinse water pressure should not greater than 50
PSI(280 Kpa)
c) Rinse time should not exceed 120 sec unless other wise
specified by governing procedure.
d) Using a coarse spray at a minimum distance of 12
inches.

45. Water washable:
A coarse water spray removes loose
penetrant by scrubbing action :

46. 1. Water washable: (STEPS)
1. Precleaning by rinsing
2. Dry by blower (hot circulating air)
3. Application of penetrant
4. Dwell time
5. Removal of excess penetrant by water wash (shall be
applied by coarse bubble flow)
6. Drying

47. 7. Application of developer
8. Developing time
9. Interpretation
10. Post Cleaning
11. Report

48. 2.(A) Post Emulsifiable Penetrants
(Lipophilic):
After the required penetrant
dwell time, the part must be emulsified by
immersing with emulsifier, effective post
rinsing is done either by manual automatic or
semi automatic spray equipments.

49. 2(B). Post Emulsifiable Penetrants: (Hydrophilic)
After the required penetrant dwell time &
prior to emulsification the part shall be pre rinsed
with water spray using the same process as for
water washable penetrants. Pre rinsing time shall
not exceed 1 min after pre rinsing the excess surface
penetrant shall be emulsified by immersing in or
spraying with hydrophilic emulsifier. After
emulsification the mixture shall be removed by
immersing in or rinsing with water.

50. 2. Post Emulsifiable
Preclean
Penetrant application
Dwell time
Emulsification
water wash rinse
dry part Apply Aqueous developer(water)
Apply Developer Dry Dwell time
Dwell time
Inspection Inspection
Post Clean Post clean

51. 3. Solvent Removable:
Penetrants are removed by wiping with a
cloth, moistured with solvent. They are supplied
in aerosol cans for portability & are primary
used for spot checks (small area).

52. 3.Solvent Removal Penetrants
1. Precleaning
2. Application of penetrant
3. Dwell time
4. Excess penetrant removal
5. Application of Developer
6. Developer Dwell time
7. Interpretation
8. Post Cleaning
9. Reporting

53. 1.Solvent Removable
1. Visible 2. Fluorescent
1- Interpretation shall be carried out
in an ordinary light .At inspected
surface light intensity (minimum
1000 lux )
1- Interpretation Shall be carried out at a
dark place under UV light (black light)
Intensity = 1000 micro watt/cm² at a
distance from 12” and dark room
intensity should be less than 20 lux.
2- Colour indication
Yellowish green.
Min warming time of U.V lamp should be
(5-10) min prior to inspection.But in LED
Ultraviolet Lamp Warming is not required.
2-Colour indication
Red/ Pink
“ We should have pocket magnifier
range =3 -10 (x)

54. NOTE:
Distance of spray to specimen = 8”-10”
Angle of spray to specimen = 30⁰ -40⁰
To normal

55. Fluorescent light (u.v. light)

56. Summary of penetrant processes.

57. D.P. Set up
Portable D.P. Kit Permanent Online
setup
Kit Contains
1. Cleaner For Mass
Production
2. Developer
3. Penetrant
4. Lint free cloth
5. Light Arrangement
Cl, S, Free D.P Material is used.

58. Name of Manufacturers of developer &
Penetrant:
1. Magna Flux
2. P. Met
3. Check met
4. Pradeep Metal
5. Flaw Check
Reference Blocks: The Blocks made of aluminium
steel, nickel, glass or ceramics some of them are
used for checking the sensitivity of test system
by comparison.

59. 1. Aluminium Cracked Block.
(ASTMB 209 Type 2024)
Standard temp = 10⁰- 52⁰ (according to ASME
SEC V article 6 appendix III
To Compare DP material & performance of
Penetrants.
The Blocks are heated & quenched to produce an
overall circular cracks pattern.

60. Aluminium Cracked Block.
(ASTMB 209 Type 2024)

61. 2. Nickel Chromium Panel
The Ni– Cr test panel are ideal penetrant
sensitivity comparators . The comparators
are available with 10, 20, 30, 50 (microns).

62. Discontinuity can be detected by DPT
1. (Rolled Product)
PLATE : Cracks Porosity (pinhole) Edge lamination
Crack: Sharp linear with zigzag (~)
Porosity: Round, with defined boundaries
Edge Lamination: Sharp linear straight (-)
2. Welding : 1- crack & Porosity appear same as
plate
Undercut – Irregular width
3. Casting: Hot tear, blow holes, porosity, cold shuts
shrinkage.
4. Forging: Crack, Lap, external bursts.

63. Recording of Indications:
1. Photography (Video recorded by CCTV camera.
2. Sketch / design drawing.
3. Transparent adhesive tape (Replica transfer
coating (RTC).

64. INTERPRETATION
Evaluation of indication
Relevant
Indication from actual
discontinuities By capillary
action
Any indication whose
measure dimension exceed
1/16” (1.59mm) then it is
called relevant.
(1)-Linear – if L > 3w
(2)-Rounded – if L ≤ 3w
Non Relevant
Any indication less
than 1.59 mm due to
capillary action
False indication
due to improper
handling the method
or by design itself
without capillary
action.
Beyond acceptable limit of discontinuity is called defect.
All Discontinuity is not defect but all defect is discontinuity.

65. indication
Fluorescent indication Color contrast indication

66. indication
Color contrast Indication :
Crack indication. Bleed out shows a gross
defect.

67. Fluorescent indication
• Numerous crack Indications

68. Post Cleaning :
The final step in the penetrant inspection
process is to throughly clean the part that
has been tested.

69. Advantages of D.P.T
1. The process is relatively simple as no electric
system is required.
2. Low capital cost.
3. Establishment of procedure & standard is less
difficult.
4. Difficult shapes & sizes can be inspected.
5. Suitable for both metal & non metals
6. Aerosol spray cans make equipment portable.
7. Initial equipment investment is low.
8. D.P.T provides a proof that a defect has comes to
the surface.

70. Limitations
1. It can detect flaws which are open to the
surface / surface breaking discontinuity.
2. Require smooth non porous material.
3. Contamination can mask defects when cleaning
the specimen.
4. Chemical handling precaution necessary
(toxicity, fire)
5. Post cleaning is necessary to remove chemical
to avoid corrossion