Nondestructive

1
Nondestructive
Testing Methods
NDT
2

• Nondestructive Testing Methods
• Magnetic Particle
• Liquid Penetrant
• Eddy Current
• Radiography
• Ultrasonic
• Acoustic Emission

3
Magnetic Particle Testing
4
Magnetic Particle Testing
5
Magnetic Particle Testing
Magnetic particle inspection is a method that can
be used to find surface and near surface flaws in
ferromagnetic materials such as steel and iron.
6
Magnetic Particle Testing
The technique uses the principle that magnetic
lines of force (flux) will be distorted by the
presence of a flaw in a manner that will reveal
it's presence.
IRON POWDER
N
S
S
S
N
N
CRACK
7
Magnetic Particle Testing
IRON POWDER
N
S
CRACK
COIL (COMPLETELY CLOSED MAGNET)
8
Magnetic Particle Testing
The flaw (for example, a crack) is located from
the "flux leakage", following the application of
fine iron particles, to the area under
examination. There are variations in the way the
magnetic field is applied.
IRON POWDER
IRON POWDER
N
S
N
S
CRACK
S
N
CRACK
9
Magnetic Particle Testing
The iron particles can be applied dry or wet
suspended in a liquid, colored or fluorescent.
While magnetic particle inspection is primarily
used to find surface breaking flaws, it can also
be used to locate sub-surface flaws. But it's
effectiveness quickly diminishes depending on the
flaw depth and type.
10
Magnetic Particle Testing
Surface irregularities and scratches can give
misleading indications. Therefore it is necessary
to ensure careful preparation of the surface
before magnetic particle testing is undertaken.
11
Liquid Penetrant Testing
12
Liquid Penetrant Testing
Liquid penetrant inspection is a method that is
used to reveal surface breaking flaws by bleedout
of a colored or fluorescent dye from the flaw.
13
Liquid Penetrant Testing
The technique is based on the ability of a
liquid to be drawn into a "clean" surface
breaking flaw by capillary action.
Penetration
Penetrant
Fluorescent penetrant on surface seeps into the
crack.
14
Liquid Penetrant Testing
Emulsifies is applied to the penetrant.
Emulsifier mixes with penetrant on the surface,
but penetrant in the crack is not emulsified.
Emulsifier makes the mixture washable .
Emulsification
Emulsifier and penetrant
Penetrant only
15
Liquid Penetrant Testing
Water spray removes the emulsified penetrant.
Water removes the surface film as well.
Rinse
water
Penetrant only
16
Liquid Penetrant Testing
Developer draws the penetrant out of the crack.
Development
developer
Penetrant
17
Liquid Penetrant Testing
Black light causes the penetrant to glow in dark.
Inspection
Black Light
Developer
Penetrant
18
Ultrasonic Testing
19
Ultrasonic Testing
Ultrasonic inspection uses sound waves of short
wavelength and high frequency to detect flaws or
measure material thickness. It is used on
aircraft, the power stations generating plant, or
welds in pressure vessels at an oil refinery or
paper mill.
20
Ultrasonic Testing
Usually pulsed beams of high frequency ultrasound
are used via a hand-held transducer which is
placed on the specimen.
21
Ultrasonic Testing
Any sound from that pulse that returns to the
transducer like an echo is shown on a screen
which gives the amplitude of the pulse and the
time taken to return to the transducer.
Defects anywhere through the specimen thickness
reflect the sound, back to the transducer. Flaw
size, distance and reflectivity can be
interpreted. Because of its complexity
considerable technician training and skill is
required.
22
Eddie Current Testing
23
(No Transcript)
24
Eddie Current Testing
Eddy current testing is an electromagnetic
technique and can only be used on conductive
materials. It's applications range from crack
detection, to the rapid sorting of small
components for either flaws, size variations, or
material variation. Commonly it is used in the
aerospace, automotive, marine and manufacturinq
industries.
25
Eddie Current Testing
When an energized coil is brought near to the
surface of a metal component, eddy currents are
induced into the specimen. These currents set-up
magnetic field that tend to oppose the original
magnetic field. The impedance of coil in close
proximity to the specimen is effected by the
presence of the induced eddy currents in the
specimen.
26
Eddie Current Testing
When the eddy currents in the specimen are
distorted by the presence of the flaws or
material variations, the impedance in the coil is
altered. This change is measured and displayed in
a manner that indicates the type of flaw or
material condition.
27
Acoustic Emission Testing
28
Acoustic Emission Testing
Acoustic emission monitoring (AE) involves
listening to the sounds (which are usually
inaudible to the human ear) made by a material,
structure or machine in use or under load and
drawing conclusions about it's "state of health"
from what is heard, just as a Doctor would listen
to your heart and lungs.
29
Acoustic Emission Testing
The technique involves attaching one or more
ultrasonic microphones to the object and
analyzing the sounds using computer based
instruments.
The noises may arise from friction (including
bearing wear), crack growth, turbulence
(including leakage) and material changes such as
corrosion.
30
Acoustic Emission Testing
The advantages of AE are that a whole structure
can be monitored from a few locations, the
structure can be tested in use (without taking it
out of service) and continuous monitoring with
alarms is possible. Microscopic changes can be
detected if sufficient energy is released and
source location is also possible using multiple
sensors.
31
Acoustic Emission Testing
Applications include testing pipelines and
storage tanks (above and below the ground),
fibreglass structures, rotating machinery, weld
monitoring and biological and chemical changes.
32
Radiography(X-Ray Inspection)
33
(No Transcript)
34
Radiography(X-Ray Inspection)
X-rays are produced by high voltage x ray
machines whereas gamma rays are produced from
radioactive isotopes such as Iridium 192 .The
x-ray or gamma rays are placed close to the
material to be inspected and they pass through
the material and are then captured on film. This
film is then processed and the image is obtained
as a series of gray shades between black and
white.
35
Radiography(X-Ray Inspection)
The choice of which type of radiation is used (x
ray or gamma ) depends on the thickness of the
material to be tested. Gamma sources have the
advantage of portability which makes them ideal
for use in construction site working.
36
Radiography(X-Ray Inspection)
X-rays and gamma rays are very hazardous. Special
precautions must be taken when performing
radiography. Therefore the operator will use
these inside a protective enclosure or with
appropriate barriers and warning signals to
ensure there are no hazards to personnel.
37
Back to Table of Contents