Nondestructive test

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4. The use of noninvasive
techniques to determine
the integrity of a material,
component or structure
or
quantitatively measure
some characteristic of
an object.
i.e. Inspect or measure without doing harm.
Definition of NDT

5. Most Common NDT Methods
 Visual
 Liquid Penetrate
 Magnetic Particle
 Ultrasonic
 Eddy Current
 X-ray

6. Most basic and common
inspection method.
Tools include
fiberscope's, bore
scopes, magnifying
glasses and mirrors.
Visual Inspection
Robotic crawlers permit
observation in hazardous or
tight areas, such as air ducts,
reactors, pipelines.
Portable video inspection
unit with zoom allows
inspection of large tanks and
vessels, railroad tank cars,
sewer lines.

7. Liquid Penetration Test ~ LPT
 Liquid penetrant inspection is a method
that is used to reveal surface breaking
flaws by bleed out of a colored or
fluorescent dye from the flaw.
 The technique is based on the ability of a
liquid to be drawn into a "clean" surface
breaking flaw by capillary action.
 After a period of time called the "dwell,"
excess surface penetrant is removed and
a developer applied.It draws the
penetrant from the flaw to reveal its
presence.
 Colored (contrast) penetrants require
good white light while fluorescent
penetrants need to be used in darkened
conditions with an ultraviolet "black
light".

8. Liquid Penetration Test ~ LPT
A liquid with high surface wetting characteristics
is applied to the surface of the part and allowed
time to seep into surface breaking defects.
A developer (powder) is applied to pull the
trapped penetrate out the defect and spread it on
the surface where it can be seen
Visual inspection is the final step in the
process. The penetrate used is often loaded
with a fluorescent dye and the inspection is
done under UV light to increase test
sensitivity.

9. Basic Procedure
Pre-Clean
Penetrant Application
Excess Penetrant Removal
Developer Application
Inspect/Evaluate
Post-clean

10. Liquid penetrant inspection (LPI) is one of the most widely
used nondestructive evaluation (NDE) methods.
Its popularity can be attributed to two main factors: its
relative ease of use and its flexibility.
LPI can be used to inspect almost any material provided
that its surface is not extremely rough or porous.
Materials that are commonly inspected using LPI include
the following: Metals (aluminum, copper, steel, titanium,
etc.) Glass Many ceramic materials Rubber Plastics
Common Uses of Liquid
Penetrant Inspection

11. Advantages
The method has high sensitivity to small surface
discontinuities.
The method has few material limitations, i.e. metallic and
nonmetallic, magnetic and nonmagnetic, and conductive and
nonconductive materials may be inspected.
Large areas and large volumes of parts/materials can be
inspected rapidly and at low cost.
Parts with complex geometric shapes are routinely
inspected.
Indications are produced directly on the surface of the part
and constitute a visual representation of the flaw.
Aerosol spray cans make penetrant materials very portable.
Penetrant materials and associated equipment are relatively
inexpensive.

12. Disadvantages
Only surface breaking defects can be detected.
Only materials with a relatively nonporous surface can be
inspected.
Precleaning is critical since contaminants can mask defects.
Metal smearing from machining, grinding, and grit or vapor
blasting must be removed prior to LPI.
The inspector must have direct access to the surface being
inspected.
Surface finish and roughness can affect inspection
sensitivity.
Multiple process operations must be performed and
controlled.
Post cleaning of acceptable parts or materials is required.
Chemical handling and proper disposal is required.

13. Penetrant Type
Fluorescent
Visible
Method
Water Washable
Postemulsifiable – Lipophilic
Solvent Removable
Postemulsifiable – Hydrophilic
Developer Form
Dry Powder
Wet, Water Soluble
Wet, Water Suspendable
Wet, Non-Aqueous
Choices of Penetrant Materials

14. Magnetic Particle Test
 The part is magnetized. Finely milled iron particles coated
with a dye pigment are then applied to the specimen. These
particles are attracted to magnetic flux leakage fields and
will cluster to form an indication directly over the
discontinuity. This indication can be visually detected
under proper lighting conditions.

15. Basic Procedure
Component pre-cleaning
Introduction of magnetic field
Application of magnetic media
Interpretation of magnetic
particle indications

16. Permanent magnets and electromagnetic yokes are also
often used to produce a longitudinal magnetic field. The
magnetic lines of force run from one pole to the other, and
the poles are positioned such that any flaws present run
normal to these lines of force.
Producing a Longitudinal Field
Using Permanent or
Electromagnetic Magnets

17. Dry Magnetic Particles
Magnetic particles come in a variety of
colors. A color that produces a high level
of contrast against the background should
be used.

18. Wet Magnetic Particles
Wet particles are typically supplied as
visible or fluorescent. Visible particles are
viewed under normal white light and
fluorescent particles are viewed under black
light.

19. Advantages
Can detect both surface and near sub-surface defects.
Can inspect parts with irregular shapes easily.
Precleaning of components is not as critical as it is for some
other inspection methods. Most contaminants within a flaw will
not hinder flaw detectability.
Fast method of inspection and indications are visible
directly on the specimen surface.
Considered low cost compared to many other NDT methods.
Is a very portable inspection method especially when used
with battery powered equipment.

20. Disadvantages
Cannot inspect non-ferrous materials such as aluminum,
magnesium or most stainless steels.
Inspection of large parts may require use of equipment with
special power requirements.
Some parts may require removal of coating or plating to
achieve desired inspection sensitivity.
Limited subsurface discontinuity detection capabilities.
Maximum depth sensitivity is approximately 0.6” (under ideal
conditions).
Post cleaning, and post demagnetization is often necessary.
Alignment between magnetic flux and defect is important

21.  Flaw Detection and Evaluation
 Leak Detection
 Location Determination
 Dimensional Measurements
 Structure and Microstructure Characterization
 Estimation of Mechanical and Physical Properties
 Stress (Strain) and Dynamic Response Measurements
 Material Sorting and Chemical Composition Determination
 Assist in product development
 Screen or sort incoming materials
 Monitor, improve or control manufacturing processes
 Verify proper processing such as heat treating
 Verify proper assembly
 Inspect for in-service damage
Some Uses of NDT Methods

22. Reference
 How stuff works
 Wikihow
 Non destructive testing (Book by N.J.Shah)