PENETRANT TESTING
Introduction
Content of PT Subject
• NDT Methods
• General principles of Penetrant Testing
• Capillary action
• Penetrants
• Sensitivity
• Fluorescent
• Penetrant systems
• Parameter of Penetrant Testing
• Selection of Penetrant System
• Inspection of Penetrant System
Non-destructive testing
▪ the use of special equipment and methods to learn something about
an object without harming the object
▪ usually implies for a nonliving object, such as a piece of metal. It is
being evaluated to assure the object is free of defect
▪ applied to various industry such as airplanes, automobiles, nuclear
power plants, oil and gas facilities, etc
▪ based on the scientific principles of physics and chemistry.
Non-destructive testing (Regular Method)
▪ Visual testing
▪ Penetrant testing
▪ Magnetic testing
▪ Ultrasonic testing
▪ Radiographic testing
▪ Eddy current testing
Non-destructive testing (Advanced Method)
• Phased Array UT
• Computerized RT
• Digital RT
• Time of Flight Diffraction UT
• Infrared Thermographic Testing
• Acoustic Emission
Penetrant Testing Methods
• Penetrant testing is divided into several methods based on penetrant
types, methods of excess penetrant removal and type of developer.
• The methods differ by how basic principle of the method is applied
• Such example:
Fluorescent technique
Visible (color contrast) technique
Penetrant Testing vs. Magnetic Testing
• PT needs more surface preparation than MT.
• PT only detects surface breaking discontinuity, while MT detects
surface breaking discontinuity and near-surface discontinuity
• PT can be applied for various material, with consideration that the
material is not porous. MT can be applied for ferromagnetic material
only
• PT process can be more time consuming than MT
• PT process can be automated especially for small products in certain
PT methods
History of PT
• The very early form of PT is surface inspection of pottery. Carbon
black powder are rubbed on surface of glazed pottery to find any
crack. The carbon black would settle in surface crack rendering the
crack is visible.
• Later, it is applied in railways workshop and called as “oil and whiting”
method. Locomotive parts would be submerged into heavy oil diluted
in kerosene.
• After cleaning the oil, the surface parts were coated with fine
suspension of chalk in alcohol. When alcohol evaporate, a white
surface layer was formed.
• Vibration, such as by being struck with hammer, was applied causing
residual oil in any surface defect to seep out and stain the wahite
layer.
General Principle of PT
Capillary action
▪ Video :
https://www.youtube.com/watch?v=
MtEv8_oCZoM
▪ Capillary action is physics principle
implemented in penetrant testing.
▪ Capillary action may cause elevation or
depression of liquid surface when it is
in contact with solid surface.
▪ Effect of capillary action is shown by
capillary tubes.
▪ Liquid surface in smaller tube is higher
than liquid surface in bigger tube.
General Principle of PT
▪ Capillary action depend on two
properties of liquid:
oSurface tension (as effect of
cohesive force)
oWetting ability/contact angle (as
effect of adhesive force)
▪ If the adhesive force exceed the cohesive
force, the liquid will rise up the tube.
▪ The smaller the tube, the greater effect
of capillary action.
Penetrant Material
• Cleaning agent (Solvent-based or water)
• Penetrant (Fluorescent or Color contrast)
• Developer (Dry powder, solvent-based, etc)
PT Process Guide
• Video : https://www.youtube.com/watch?v=lMld2Td83Sw&t=63s
PT Process Guide
1. Pre-Cleaning
▪ PT only detect discontinuity which open to surface and free from
any contamination
▪ Pre-cleaning objectives is to remove any material block open
discontinuity
▪ Surface specimen must be clean, dry and within temperature
limits
PT Process Guide
2. Penetrant Application
▪ Penetrant must be applied on whole inspected area. The area
must be clean and dry.
▪ Sufficient dwell time is needed to ensure penetrant enter
discontinuity. Dwell time is called also as contact time.
▪ Penetrant can be applied by brushing, dipping/immeersion,
spraying, pouring
PT Process Guide
3. Removal of Excess Penetrant
▪ Removal of excess penetrant is a very crucial process in PT.
▪ Excess penetrant must be removed from the surface but leaving
entrapped penetrant in discontinuity
▪ Improper excess penetrant removal can lead to high background
level or mis-defect inspection, vice versa.
PT Process Guide
4. Developer Application
▪ A thin layer of developer is applied onto specimen surface.
▪ Sufficient time developing time is needed for penetrant
“bleedout” from discontinuity.
▪ Bleedout occurred because capillary action of developer.
Developer consist of small particle which create smaller pores
than discontinuity size. This make capillary action of developer
stronger than capillary action of discontinuity.
▪ Entrapped penetrant in discontinuity seep out into developer
and leave stain of penetrant.
PT Process Guide
5. Inspection
▪ When developing time elapsed, any observed indication (linear or
rounded indication) must be observed and evaluated under
proper viewing condition. NDT code cover the required viewing
condition under white light and UV light.
▪ Inspection must be conducted within inspection time stated by
NDT code.
PT Process Guide
6. Post-cleaning
▪ After inspection, specimen may be cleaned for further process
such as painting.
Reference
• TWI, CSWIP PT Coursenote
• www.nde-ed.org
• Magnaflux Penetrant Guide
• Chemetall Liquid Penetrant consumables
• A.A. Muhsen, Warsaw University of Technology, 2021, NonDestructive Testing Methods and their Application in Technology
• Anmol Birring Youtube Page
• De Edutainment Channel, Youtube
• www.tutorchase.com, Cohesion, Adhesion, and Surface Tension