Non destructive testing basics

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Basic Nondestructive
Testing
for EXPO 2012
by
Neville W. Sachs, P.E.
Applied Technical Services New York

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What we plan to cover
1. Definition of nondestructive testing
2. Some philosophy on why it is helpful
and the major pitfalls
3. Basic theory
4. Explanations of common techniques
5. Demonstrations of common analysis
techniques

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Nondestructive Testing
(NDT)
 Also known as nondestructive examination
(NDE)
 Involves inspection and analysis of
machinery or components without affecting
the operation or the properties of the subject.
(As opposed to a tensile test or other
destructive test such as sectioning.)

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From the ASNT Website
(American Society for Nondestructive Testing)
What Is Nondestructive Testing?
 Nondestructive testing asks “Is there
something wrong with this material?”
 Nondestructive testing (NDT) has been
defined as … “those test methods used to
examine an object, material or system without
impairing its future usefulness.”

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The British View (BINDT)
 “Non-destructive testing is the branch of engineering
concerned with all methods of detecting and
evaluating flaws in materials.”
 “The essential feature of NDT is that the test process
itself produces no deleterious effects on the material
or structure under test.”
 “The subject of NDT has no clearly defined
boundaries …”

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A Brief History
Formal NDE dates back to early railroad days
when a mixture of oil and talc were used to detect
cracking in axles and wheels.
Since then science has developed a wide range of
tools and abilities to noninvasively detect
problems before they become disasters.

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Wikipedia says
nondestructive testing is …
 Acoustic emission testing (AE or AT)
 Blue Etch Anodize (BEA)
 Dye penetrant inspection Liquid penetrant testing (PT or LPI)
 Electromagnetic testing (ET)
• Alternating current field measurement (ACFM)
• Alternating current potential drop measurement (ACPD)
• Barkhausen testing
• Direct current potential drop measurement (DCPD)
• Eddy-current testing (ECT)
• Magnetic flux leakage testing (MFL) for pipelines, tank floors, and wire rope
• Magnetic-particle inspection (MT or MPI)
• Remote field testing (RFT)
 Ellipsometry
 Guided wave testing (GWT)
 Hardness testing
 Impulse excitation technique (IET)
 Infrared and thermal testing (IR)
• Thermographic inspection
 Laser testing
• Electronic speckle pattern interferometry
• Holographic interferometry
• Low coherence interferometry
• Profilometry
• Shearography
 Leak testing (LT) or Leak detection
• Absolute pressure leak testing (pressure change)
• Bubble testing
• Halogen diode leak testing
• Hydrogen leak testing
• Mass spectrometer leak testing
• Tracer-gas leak testing method Helium, Hydrogen and refrigerant gases
Magnetic resonance imaging (MRI) and NMR
spectroscopy
Metallographic replicas [7] [8]
Near-infrared spectroscopy (NIRS)
Optical microscopy
Positive Material Identification (PMI)
Radiographic testing (RT) (see also Industrial
radiography and Radiography)
Computed radiography
Digital radiography (real-time)
Neutron radiographic testing (NR)
SCAR (Small Controlled Area Radiography)
X-ray computed tomography (CT)
Scanning electron microscopy
Surface Temper Etch (Nital Etch)
Ultrasonic testing (UT)
ART (Acoustic Resonance Technology)
Electro Magnetic Acoustic Transducer (EMAT)
(non-contact)
Laser ultrasonics (LUT)
Internal rotary inspection system (IRIS)
ultrasonics for tubes
Phased array ultrasonics
Time of flight diffraction ultrasonics (TOFD)
Time of Flight Ultrasonic Determination of 3D
Elastic Constants (TOF)
Vibration Analysis
Visual inspection (VT)
Pipeline video inspection
Corroscan/C-scan
IRIS - Internal Rotary Inspection System
3D Computed Tomography
Industrial CT Scanning
Heat Exchanger Life Assessment System
RTJ Flange Special Ultrasonic Testing

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So, going back to the ASNT website,
these are the common NDT
techniques
Acoustic Emission Eddy Current
Liquid Penetrant Magnetic Particle
Ultrasonic Testing Visual Inspection
Vibration Analysis Radiography (X-ray)
Also common are:
Infrared Thermography Hardness Testing

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Your Personal NDT
 When you go to the market to select fruit
or veggies, what do you do? How do you
make your choice?
 If your car is making a new strange noise,
what do you do?
 Do you ever glance at your car tires to
see if they are soft?

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The goal –
A. Look at it without causing a
damaging interruption
B. Use the test information to
form a plan

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NDT in everyday life
Would you rather have an MRI - or should
we do exploratory surgery for that knee
problem?
Would you prefer an EKG or exploratory
surgery?
For both of these, consider the possible
costs and the possible benefits.

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The goal of NDT is to analyze a piece of
material, without damaging its performance
capabilities, and then use that information to
predict future performance.
The graph below shows leaks in the roof of a process
vessel. (Replacing the vessel will cost about $50,000,000
and take about a year.)
300
200
100
0 4
Routine inspections of a vessel
with stress corrosion cracking
Roof leaks
vs.
Inspection date
Years from vessel installation
Numberofleaks
8 12 16 20

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The goal –
Look at it without causing a
damaging interruption
So, not only can we look at and inside
pieces, but we want to do that without
causing an interruption.
Then a question arises - Do humans
really commit that many errors?

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Human Error Experts say the average
person makes six significant errors per
week.
BUT, our surveys show the typical industry
person believes they make a significant
error about once every FIVE months

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In 23 years of doing industrial training
programs and asking people to compare their
skills with others in the same job,
only 37 people have rated themselves as below
average!
For the last six years we have also asked people
to rate their safety awareness. Only TWO have
said they were below average!!!
( 23 years x 15 seminars/year x 15 people/seminar = 5100 students
37/5100 = 0.7% )

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How Often Do Human Errors
Happen?
(From Chemical Engineering Magazine, McGraw Hill, NY,NY)
 Industrial Activities
• Critical routine task - 1/1000
• Non-critical routine task - 3/1000
• General error rate for high stress rapid activities - 1/4
• Non-routine operations (startup, maintenance, etc.) - 1/100
• Checklist inspection - 1/10
 General Human Error
• of Observance - 1/50
• of Omission - 1/100

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How Often Do Human Errors
Happen?
(From Chemical Engineering Magazine, McGraw Hill, NY,NY)
 Industrial Activities
• Critical routine task - 1/1000
• Non-critical routine task - 3/1000
• General error rate for high stress rapid activities - 1/4
• Non-routine operations (startup, maintenance, etc.) - 1/100
• Checklist inspection - 1/10
 General Human Error
• of Observance - 1/50
• of Omission - 1/100

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Infant MortalityFailureProbability
The "Reliability Bathtub"
Time (log scale)
Normal Run Period
Wear out
Infant Mortality
The period right after
the machine is started.
These failures are
usually related to errors
in assembly.
Normal Run Period
The long stable time when
successful operation can be
expected. Failure in this time
is usually from unexpected
wear or a change in operating
conditions.
Wear out -
A function of
the original design

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So, what % of equipment
actually suffers from Infant
Mortality
It really depends on the training of the installation
personnel and their training and care. There is data from
studies of maintenance activities around the country and
have seen it range from
a low of about 5% to as high as 22%!
Several North American studies have shown
the average is about 14% substantially
defective!

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The most important benefits of NDT are that
it allows us to inspect materials and
machinery:
1. Without introducing infant mortality.
2. Without damaging the material.

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And ..
The data shows that:
All humans make frequent errors.
We tend not to recognize those errors.
The benefit of NDT is that it can find
defective material/equipment without
damaging the pieces and without the
interruptions that increase the
probability of human error.

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Common Uses for NDT
• Component/machine condition
evaluation – Example – Inspection of a
ski lift component or an elevator rope.
•Predictive method - Vibration analysis
on motors, and pumps, infrared
inspection of transformers.
•Product and/or material quality
assurance – Examples – Run-in test
on a new vehicle, cleanliness of steel

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The PE’s Challenge
 We are asking technicians to conduct an
inspection.
 They are not engineers and, by definition,
must have criteria to inspect to, i.e., have
to know what is considered a defect.

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So, before we ask for a
specific NDT, we have to
know what to ask for!
Q. What is the difference between a flaw and
a defect?
A. Almost all materials have lots of flaws.
When the flaw impacts the performance of
the material, it becomes a defect.

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Important Terminology -
Defects and Flaws
 All parts have “flaws” of some magnitude
but the parts are not necessarily defective.
 A defective component is one that will not
perform as required for the necessary
time.
 A “defect” is a deviation from what is
allowable.

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Dialogue of a Common Problem
Client - “We want our xyz part mag particle tested. Can you do
that?”
Us – “Sure, we do lots of mag particle testing. What is your
standard?”
Client – “Huh? The drawing says it has to be tested.”
Us – “Does the drawing have a spec on it?”
Client – “Yeah. It says MIL-TDD41.” (Unfortunately, that is a
mil spec that was retired in 1990 and the last issue described a
procedure, without specifying flaw tolerances.)
Us – “Let’s talk about what you really need.” (More than once,
we’ve have had people ask us to MagnaFlux aluminum parts!)

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So, before we ask for an
NDT, we have to know what
to ask for!
… and one of the significant challenges is
to define what is considered a defect.
In a precision machined part, a 0.04” flaw
may be a defect, but in a large casting, it
may be just a 0.4” flaw!

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Defects or Flaws???
 When NDE people talk about flaws
(not serious stuff) they’re called
indications.
 Defects are called “relevant
indications”.

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Next, the inspection should
be done by a qualified and
certified person.

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Certification
 A certified inspector is a person who has
demonstrated their capabilities and met a legal
requirement.
 Please don’t risk your life or your reputation by
having inexperienced and uncertified inspectors
do the work. (Would you want to have a surgeon
operate on you who practices once a year? Or
one who has developed his skill by watching
other people do the job?)

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ASNT Personnel
Qualifications
 Level I – Can conduct a test under Level
II supervision
 Level II – Knows what they are doing
within specific inspection area
 Level III - Knows and can perform a wide
range of NDT methods
(Typical inspector may be certified Level II in
VT, PT, MT, and UT)

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Some of the more common NDT
methods
Thermography Vibration Analysis
Radiography (X-ray) Hardness Testing

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Some of the more common NDT
methods

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Visual Inspection
 An assurance that the person conducting
the inspection can see and recognize the
indications.
 Certification in VT is largely directed
toward weld inspection. However, to
maintain any certification, visual acuity is
tested every year.

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We have actually had experience
doing these:

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Glossary
 DEFECT – A flaw that can significantly impact the
performance of the material
 FLAW – An irregularity in the material
 TRANSDUCER – a device that converts a mechanical
force to and electrical signal and vice-versa
 RELEVANT INDICATION – something to be concerned
about

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Acoustic Emission (AE)
Common Applications
 Pressure vessels, especially tank cars
 Fiberglass and other composite tanks
 Long term bridge structure monitoring

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x
x x
x x
x
Computer
Inspected
vessel
Start with a selection of
transducers that are wired
into a computer.
Securely anchor the
transducers to a vessel or
structure in precisely
determined positions.
The computer records the
high frequency signals from
the transducers.

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 Start with a selection of transducers that are
wired into a computer.
 Securely anchor the transducers to a vessel wall
in precisely determined positions.
 One time test
• Increase the pressure (stress) in the vessel above the
normally experienced pressures (stresses).
 Long term test
• Compare the recorded data over the time period
 Analyze the noises detected by the transducers.
 If the noises are relevant, triangulate the signal
and specify additional testing in that area.

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A
D E
B C
F
Computer
Inspected
vessel
*
Start with a selection of
transducers that are wired
into a computer.
When the noise signals
exceed a limit, triangulate
the indication.
Then do further inspection
in that area with other
methods.
*

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Eddy Current (EC)
Common Applications
 Heat exchanger tubes
 Aircraft fuselage and wing surfaces
 Easily contacted surfaces
 Tube and wire production
 Ferrous and nonferrous bar production

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Eddy Current (EC)Testing
 A probe with an AC field is moved across
a metallic surface at a relatively controlled
speed and the response from the field is
monitored.
 When the field is interrupted by a change
in the structure, the response changes.

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Radiography (X-rays)
Common Applications
 Critical fabrication welds
 Any material inspection where a record
has to be available for future reference
 Searching for unwanted contaminating
materials

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Penetrant Testing
“PT”

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Penetrant Testing
“PT”
We’re going to do a penetrant test, but it is a
relatively time consuming procedure (and it is also
more prone to human error than other NDT). So
within the “PT time”, we’re going to do a magnetic
particle test.

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The Types
There are three types
of penetrant tests but
the common ones are
those using either
visible or fluorescent
dyes. The photo to
the right shows the
results of a visible
penetrant test on a
vessel weld.

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The Types
Also, there are solvent
cleanable and water
washable tests.
We’ll do a solvent-
based test.

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Visible PT - How it works
1. We suspect our piece has a defect that is open to the
surface. So we thoroughly clean the surface. Then
allow the part to dry. (5-10 minutes)
2. Next, we spray a coating of a thin red liquid, the
penetrant, onto the surface and allow the liquid to be
absorbed into the defect. (5 to 25 minutes)

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Visible PT - How it works
3. Then we thoroughly clean the surface again, but
carefully, so we don’t clean the penetrant out of the
defect. Then we allow the part to dry. ( 5 to 10 min.)
4. Next, we spray a very thin layer of a white paint-like
material onto the surface, allow the “paint” to absorb
the penetrant out of the defect, (5 to 15 minutes) and
visually inspect the piece.

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The Procedure
1. Clean
2. Spray penetrant
3. Dwell
4. Carefully clean off
excess penetrant
5. Spray developer
6. Wait and watch

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The
Procedure
 This shows a weld inspection. One of our
people is waiting for the penetrant dwell
period inside a large process vessel.

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Visible
Penetrant
After the penetrant is
cleaned off, the
developer is sprayed.
Note that there is
no dye remaining!!

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Applications
 Parts with cracks open to the
atmosphere that can be cleaned well
 For mechanical components -
structural components or aluminum,
stainless, or steel, etc.
 Relatively inexpensive initial cost for
materials

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What can it find
 Really depends on the surface
cleanliness and roughness.
 On polished stainless parts we have
found cracks that were 0.00004” wide
and 0.003” deep!

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PT Problem Areas
 Is probably the most frequently misused NDT
technique. Frequently done by inexperienced
personnel leading to gross procedure errors,
misinterpretation, and wasted $$$.
 Requires careful and thorough precleaning before
penetrant application.
 Grinding and other mechanical power cleaning
can hide indications.
 Time consuming, manpower intensive and
greatest opportunity for human error.

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PT Demonstration

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Magnetic Particle Testing
“MT”

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MT Procedure
1. Generally inspect the part and review the testing
criteria.
2. Clean the part well.
3. Set up a magnetic field in one direction.
4. Cover the field area with a contrasting magnetic
medium. (Can be a dry powder or an oil with
fluorescent particles.)
5. Set up a magnetic field in another direction.
6. Again, cover the field area with a contrasting
magnetic medium.
7. Inspect the areas where the particles accumulate.

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Set up the Magnetic Field
SouthNorth
Steel or Nickel
Plate
Particles on
Edges of FlawFlaw
SouthNorth
Then find the irregularities

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MT Procedure
1. Clean the part well.
2. Set up a magnetic field.
3. Cover the field area with a
contrasting magnetic
medium. (Can be a dry
powder or an oil with
fluorescent particles.)
4. Inspect the areas where
the particles accumulate.

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Two
views of
a weld
crack
This is WFMP testing –
wet fluorescent mag
particle.
It is viewed with a
black light.
Results of MT inspection with black light
Showing attracted particles after exam

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MP Tests
Dry powder particles
Both of these exams
used wet fluorescent
particles

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Typical Applications of MT
 Steel parts and martensitic stainless
with cracks open to the atmosphere.
(not many nickel parts)
 Moderate initial cost for materials.
Lowest applied cost.

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MT Problem Areas
 Training is not extensive or expensive and
leads to good results.
 Requires an understanding of the magnetic fields.
 Can’t be used on nonmagnetic materials.
 Poor cleaning and grinding can hide defects.
 Generally WFMP is far superior to dry particle
testing.

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Dry Magnetic Particle Demo

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Infrared Inspection
 Infrared inspections allows us to see
thermal images (radiation) much as our
eyes see visual images.

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A Belt Drive on a Air Handler
We can see that the belt
temperatures are suspect.
(c) 2012 by Applied Technical Services, Inc.

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We can see that these belts are
much too hot and are slipping.
(c) 2012 by Applied Technical Services, Inc.

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Infrared Inspection
Applications
 Transformers, switchgear, and other
electrical equipment where there may be
poor connections, etc.
 Insulation system effectiveness (air
leaks, wet insulation)
 Process equipment liquid levels, etc.
 Steam trap operation

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Infrared Inspection Cautions
 Two common errors with scanners:
• Reflections – In much the same manner as
light reflects, infrared radiation can also
reflect and give erroneous readings
• Emissivity – Black body objects have
significantly different emissivity that polished
and shiny objects and the images will differ.
 With hand-held infrared thermometers –
They will average the temperature over a given
target area, and that may be much larger than
your area of interest!

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Infrared Thermography
Demonstration
 Rather than me give a demo of how an infrared
scanner works, I’ll pass one of ours around so you
can look through it.
 COMMENTS:
• It is focused for the range from about 5 feet to
infinity.
• I know this is a bunch of engineers that want to
play with controls, so I’ve taped the controls
closed so the next person doesn’t get a useless
demo! (If you want to play with it, please see me
afterward.)

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Ultrasonic Flaw and
Thickness Testing
- “UT”

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UT
Common Applications
 Thickness testing of tanks, vessels,
piping, etc.
 Quality inspection of components such
as forgings, castings, welds, etc., looking
for internal voids
 Flaw testing of materials looking for
process induced cracking (bolts, shafts,
etc.)

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Ultrasonic
 Audible Sound - 20 to 20,000 cps (Hz)
 Normal UT Range
• 100,000 to 25,000,000 Hz
• 0.1 to 25 MHz
 Wavelength = Velocity/Frequency
10 100 1000 10000 100000 1000000 10,000,000
Sub
sonic
Cycles per second (Hertz)
UltrasonicAudible to Humans

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UT Transducer
Housing
Damping Material
Piezoelectric
Crystal
Power Cable
Inspected
Material
Sound
Pattern
Transducer sends
out a sound wave
and then reads the
reflected wave
To get an accurate
measurement, the signal
has to be essentially
perpendicular to the flaw FLAW

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Ultrasonic Testing
Ultrasonic Device
Transducer
1.500"
Sound Wave
The “black box” generates a signal and sends it to
the transducer, then reads the signals returning
from changes in “Acoustic Impedance”.

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Thickness Testing
Ultrasonic Thickness Tester
Transducer
Used to measure the
thickness of materials1.500"
Sound Wave

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Straight beam transducer
Housing
Damping Material
Piezoelectric
Crystal
Power Cable
Inspected
Material
Sound
Pattern

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Angle beam transducer
Housing
Piezoelectric
Crystal
Power Cable
Inspected
Material
Plastic
Wedge
45 deg
60 deg
70 deg
Changing Wedges
results in different
signal paths
But what do you do
when the flaw lies
at an odd angle?
(such as a weld)

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Ultrasonic Flaw Tester
Transducer
Used to search for internal
variations in materials
Ultrasonic Flaw Tester
Transducer
Sound echoes back from
changes in acoustic impedence
UT Flaw Testing

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dB
Calibrated Distance
Relativepower(dB)
6 dB
Calibrated Distance
Relativepower(dB)
How does the technician
know the true size of the
flaw?
Compare the size of the
echoes and we know that
6dB represents a doubling
in size.
Flaw Testing

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UT Testing Comments
What sort of accuracy is there
when a digital Thickness Tester
is used and the backwall isn't flat?
Transducer
1.500"
Where does that sound wave reflection go?

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Common UT Application
53 1/4"22 1/4"
228 13/16"
70 1/2"
31.3"
18 3/4"
64 1/16"
20"
29.49"
25.49"
27"
30.00"
30"
Bearing Fit Bearing Fit
Drum Fit
Find the depth of the crack in this headshaft
crack

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Unusual UT Inspection
Application
Transducer
Flaw Tester
Screen
Axle
Axle and Hub
Assembly
Ideal Sound
Path
Testing the shrink fit tightness

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Transducer
Flaw Tester
Screen
Axle
Axle and Hub
Assembly
Loose Fit
Sound Path
Unusual UT Inspection
Application (cont’d)
Finding it is loose!!

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Phased Array UT
Courtesy of Olympus NDT
Newer UT Method
This is essentially the same as the
ultrasound tests used on humans
and animals. There are multiple
crystals in the transducer and the
computer software analyzes them.

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Common Applications
 Complex and Internal Welds
 Shafts
 Bolts
 Internal areas that are hard to
inspect with other methods but
have a known crack geometry

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UT Problems Areas
 Very operator intensive
 Requires good knowledge of the part
geometry
 Insensitive to flaws that are basically
parallel to the sound path
Have to have certified, qualified inspector

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Vibration Analysis
A. Purpose of Vibration Analysis
B. Basic Principles of Vibration
Analysis
C. Basic Terminology

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Vibration Analysis
As mechanical machinery became larger and more
complex, science began to realize the problems that
resulted from excessive vibration. By the end of WWII the
first methods to analyze and control vibration had been
developed.
Vibration analysis is used to measure
machinery movement to understand
why it is happening.

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Comments
• Frequently used as an acceptance gage on new
machinery.
• Is an excellent comparative method for
monitoring machine condition.
• On existing operating machinery, monitoring and
analyzing vibration data allows for very early
warnings (2-3 months) of impending failures.
• The data is relatively easy to gather and, with
computers and software programs, relatively
easy to handle.
• Requires skilled, well-trained and certified
inspectors.

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Vibration Analysis Example
Readings on the motor
and the pump tell us the
condition of the bearings and
the coupling, the alignment,
and whether the base, grout,
and foundation are in good
condition.
High frequency monitoring of the
bearings can tell us the lubricant
film thickness.
Trending of this data can alert us to worsening problems.
Motor
Coupling
Pump
Base Plate
Foundation Block
Grout

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Typical Machine
Monitoring
How often do you have to check? That depends on
the operating conditions and the criticality of the
machine. It could vary from once per month to once
every six months.
Motor
Coupling
Pump
Base Plate
Foundation Block
Grout

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Vibration Terminology
Measurement Units
Amplitude - Describes the amount of
vibration and is expressed in three ways.
• Displacement (miles)
• Velocity ** (miles/hour)
• Acceleration (0 to 60 mph time)
Frequency - Describes the periodical nature of the vibration
and is expressed in one of three ways;
• CPM or Cycles Per Minute
• Hz or CPS or Cycles Per Second
• Orders or multiple of a frequency of interest

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Looking at a Vibration
Spectrum
Misalignment, imbalance,
structural problems, etc.
Bearing, gear, and
lubrication problems
Overall reading gives a general
guide to the machine condition.
A
M
P
L
I
T
U
D
E
FREQUENCY – CPM or Hertz

ATSNY© 2012 99
Data Trending
A doctor doesn’t need a lot of your medical history to diagnose a
broken arm, but it does help your long-term health to understand how
blood pressure, cholesterol, etc., are changing. In a similar manner, the
vibration analyst can immediately spot imminent serious problems, but
trending of data can alert the site to longer term situations.

ATSNY© 2012 100
100
One Last Nondestructive
Inspection Method –
Hardness Testing
There is a relationship between hardness and
tensile strength. The relationship is much
better for some (steel) than for others (cast
iron, rock).
The harder a material is, the stronger it is.

ATSNY© 2012 101
Commonly used as a QC tool to readily
verify the tensile strength or other
property of a metal or plastic.
Metals – Rockwell and Brinell are the
common types of test
Plastics – Barcol
Elastomers - Durometer
Hardness Testing

ATSNY© 2012 102
102
Hardness vs.
Tensile
Strength
for Steel
200 300 400 500
Tensilestrength(ksi)
80
0
Brinell Hardness Number
40
120
160
200
240
Typical Hardness -
Tensile Strength
Range for Steel
data from SAE handbook
100
HBN x 500 ≈ Tensile Strength
HRC x 10 ≈ HBN
Easy Conversions

ATSNY© 2012 103
103
Brinell Hardness
Circa 1900
Two common scales, 500
kg and 3000 kg
Very good for castings
where there may be
inhomogenities
Problems with thin
materials
Applied Load
10 mm ball
Measure impression
diameter, interpret
from ASTM chart
d

ATSNY© 2012 104
104
Rockwell Hardness
13 ranges - with the
most common as HRC, HRB,
HRA
Operation - Apply a minor
load to reduce surface
effects, then apply the major
load. After movement stops
measure the change in depth.
Versatile - with a wide
range of applications
Minor load depth
Major load depth
Indenter with load
depending on scale
Rockwell test indenters include
diamonds and balls. The loads
vary from 15 to 150 kg.

ATSNY© 2012 105
There are lots of other NDT tools
available from coating thickness
gauges to magnetic flux leakage
devices (checking for loss of material in tubes and tank
floors) to X-ray diffraction (checking for residual
stress in metallic components).

ATSNY© 2012 106
How do we suggest YOU
should approach NDT?
 Sit down with your knowledgeable folks and ask
yourselves what your real materials, mechanical,
and electrical challenges or unknowns are.
 Then ask, “Can they be anticipated?”
 If the answer is either “Yes” or “I don’t know.”,
call somebody in the NDT business, describe
your problem, and ask them for their ideas.

Non destructive testing basics

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