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Ultrasonic Inspection
WELCOME!
A brief overview of ultrasonic inspection
principles, applications, & techniques.
Presented by Superior SignalCompany, Inc.
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Copy righ t 2000, Superior Sig nal Company, Inc.
Not to be reproduced in any way with out wri t ten permission from Superior Signal Company, Inc.
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What is Ultrasound?
Sound frequencies above 20kHzare
considered Ultrasonic. These are frequencies
above the human range of hearing.
It doesnt matter how loud, or how strong the
amplitude of a particular ultrasound, our unaided
human ear can NOT hear it
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High Frequency Ultrasound
Comes from...
F riction
A rcingT urbulenceAlthough there are frequently sonic sounds also associated
with faults/leaks, we can not simply use our ears to hearthem because they are masked by high ambient noise levels.
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(In moving equipment)
(In electrical connections)
(In leaking systems)
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Important Characteristics of Ultrasound
It Does not travel as far as sonic sound.
Sounds waves are more localized, easier to trace to their source.
It Does not bend or penetrate as easily.
Sounds waves do not travel well around corners or through objects.
It Does reflect (echo).
Ultrasounds will bounce or reflect off surfaces, however reflections
are lower in amplitude than the original signal.
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Sound does not t ravel well f rom one
medium to ano ther.(liquid to gas, gas to solid, etc.)
Example;It is difficult for someone only a few
inches underwater to hear what is going on at the
surface.
This is the reason specific sensors are designed for
detection within a particular medium. (Contact,
Airborne or Liquid)
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Detection Methods
Contact Sensor
Airborne Sensor
Pressure Leaks
Vacuum LeaksExternal Valve Leaks
External Hydraulic Leaks
Electrical Arcing
Defective Steam Traps
Worn Bearings/Gears
Internal Valve Leaks
Internal Hydraulic Leaks
REMEMBER: Sound does not travel well from one medium to another.(liquid togas, gas to solid, etc.) This is why different pick up devices, orsensors, are used for the
specific job at hand.
Use to detect sounds which are created within ai r, and travel thr ough the air.
Use to detect sounds which are created withi n soli ds, and travel thr ough soli ds.
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Ultrasonic Instruments Detect and Convert
High (Ultrasonic)Frequency Sound
To low (Sonic) Frequency
Sound
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Sounds must be translated, or converted to lower /audible
frequencies in order to be heard by the user, or analyzed.
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There are two electronic processes used
in ultrasonic detectors to select and
convert high frequency ultrasound tolower, audible frequencies.
Heterodyne
DND
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The word is from the Greek, meaning Different Waves.
This is an acronym for Dynamic Noise Discrimination.
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Frequency Tuning (Heterodyne)
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When using a heterodyne type detector you have a limited window of
sound that you can hear at any one time. It is like a radio in a sense that
you can only tune to, or hear one frequency (radio station) at a time.
When using an instrument that allows you to tune, you are basically
adjusting a vertical window up and down the detection range of theinstrument (left and right in the example above). The width of this window
depends on the instrument, but it is generally not more than a few kHz
wide. A disadvantage to heterodyning is that if a key signal is outside of
this window, it will not be detected.
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Frequency Selection (DND)
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When adjusting the sensitivity of a DND type detector, think of it as moving a horizontal
threshold up and down over the detection range of the instrument. As you lower the
sensitivity only the signals of the greatest amplitude will be translated, while all sounds
will be translated when using a high sensitivity setting.
A detected sound will not trigger the translation process until the amplitude crosses this
threshold. Once it does, it does not matter where the original frequency came from, it will
be translated to an audible signal. This is the advantage to DND. No tuning is involved!
Low
Sensit iv i ty
High
Sensit iv i ty
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Technology Comparison
DND
HeterodyneClose to real sound translation
Best for contact applications
Best for using with analyzers
Limited frequency rangeMay miss signals if not tuned properly
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Automatic TuningBest for air leaks, especially in very loud areas.Very simple to use.
Sound does not maintain true signatureCan not use with analyzer
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Application; Air Leaks
When a pressurized gas leaks
from an orifice, it is forced into
turbulence where the moleculescollide and rub into each other.
It are these collisions that create
ultrasonic tones which can be
detected using an ultrasonic leak
detector.
Photo reference; An Album of Fluid Motion.
Van Dyke, Parabolic Press
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n How much turbulence is present, which
depends on...
Size of leak Shape of leak
Material composition of leak
Flexible material will not produce as much turbulence as
more solid material. Pressure behind the leak.
Atmospheric Conditions
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Finding leaks with ultrasound
depends on...
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Use Ultrasound to
Minimize Leakage!
Reduce power consumpt ion
Save Money
Reduce Chance o f Fai lure
Do your compressors run
between shifts?
Do you have difficultymaintaining optimum pressures?
Have you come to rely on a
backup compressor for routine
demand?
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Sound of an Air Leak
Click t o hear.
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This air leak was found on the main
air outlet pipe of a noisy
compressor. Listen to the
difference between the background
noise and the leak sound as theinstrument moves back and forth
across the direction of the leak.
Heterodyn e typedetector
DND type detector
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Air is NOT Free!Compressed Air Leaks at 100psi.
Days left
unrepaired
Number of
leaks
Estimated
orifice size
SCF/day at
100 psi.
cost per
day at
.25/1000 scf
Actual
dollar loss
180 6 1/64 584.64 0.88 157.85$
12 1/32 2332.8 7.00 1,259.71$
12 1/16 9345.6 28.04 5,046.62$6 1/8 37440 56.16 10,108.80$
2 1/4 149760 74.88 13,478.40$
At 100 psi, your system has lost approximately. $30,051.39
This chart estim ates the financial impact of 38 leaks of
var ious sizes wi th in a 6 month p eriod.
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Ultrasonic LeakDetection
n Ultrasound is the only technology that will detect ANY
type of gas, including systems under VACUUM!
n Unlike gas sniffers It is not affected by wind,
contaminants or concentrations of gas in the air.
n Detect leaks in areas NOT pressurized (Using Sound
Generator).
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Application; Steam TrapsDetect ultrasonic frequency of internalturbulent flow.
What is a steam trap?Simply stated, a steam trap is a mechanical device designed to remove
condensate (water) from the system while retaining (trapping) the steam.
Why are they needed? Efficiency; Keep system HOT, return water to boiler.
Eliminate Waterhammer
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n
Steam Traps Fail Open Pass live steam which is costly to produce.
Closed
Condensate will collect.
Why test them?Steam Traps are generally located at low points in the system,a natural collecting point for dirt, rust, and other contaminants.
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Video Clip
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One Leaking Trap...
Loses 27 lb/hr. or 226,800 lbs. of steam per year!
(5/64 in.ori f ice @ 150psig)
Ref: Assessing the Impact of Energy Losses in Steam Systems, Plant
Engineering, July 10, 1995
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12 tons of coal ($679.00)
2,500 gal. of fuel oil ($1392.00) 314,000 cu. ft. of natural gas ($1272.00)
Cost to p rodu ce? . . .
A typical petrochemical plant wil l use 5000 steam traps. I n plants with no
previous trap testing general ly 30% are leaking.
How many traps are leaking in you r faci li ty?
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Trap Sounds
n Continuous flow type traps require more of a
trained ear to detect leakage by listening
only. Compare meter readings with a known
good trap.
n Intermittent purge traps (inverted bucket)
usually fail open. Listen for rushing sound.
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Good Inverted
Bucket Trap
Bad Inverted
Bucket Trap
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Application; ValvesDetect ultrasonic frequency of
internalturbulent flow.
Why Test them?
Case : A pipeline where the contents are various gases; oxygen, carbon dioxide,
compressed air, and nitrogen. Pressure differential across the valves is approximately 60psi. Valve leakage causes non-conformance to the required purity standards, making the
final product unusable.
Solution: A monthly program of ultrasonic detection was successful in determining which
valves were leaking and how extensive the leaks were. The test consisted of taking a
reading upstream and downstream of the valve under test. Leaking valves showed higher
ultrasound in the turbulent area downstream of the valve.
Result:Maintenance time and costs formerly spent on rebuilding sound valves
were saved and product purity was significantly improved.
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Video Clip
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Application; Electrical Discharge
Use ultrasound to hear what you cant seein switchgear, breakers, distribution lines,
insulators, and transformers.
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Arc
Corona
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Arcing / Corona
n Detect problems which may be masked
by ambient heat.
n Onset of Corona does not cause
temperature change.
n Ultrasound does not require opening of
electrical cabinets.
n It is easy, fast and inexpensive.
Ultrasound compliments
thermography
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n Lubrication break down
n Impact
n Scraping / Grinding
n Friction
Listen For...
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As bearings and gears
wear, ultrason ic
s ignatures present
themselves.
Click to h ear.
Application; Bearings & Gears
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Video Clip
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There are two types of trending used
with ultrasonic inspection.
Comparat ive;
Pump Motor#
Intensity
#1 #2 #3 #4 #5
Compares to other simi lar machines.
Examp le; If you have a group o f 5 pum p
mo tors each performing the same job under
the same cond i t ions, inconsis tent ly high
ul trasonic reading s w i l l ind icate a defect, or
the on set of fai lure.
The condi t ion of mo tor #4 may be obvious, and
possibly even diagnosed simp ly by l is tening.
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Date
Intensity
The other type of trending typically used
with ultrasonic inspection is...
Histor ical; Loo ks for inco nsis tenc ies ov er a per iod oftime Example; If you had looked specifically
at reading s taken on p ump #4 (from the previous
page), they m ay loo k l ike this ...
The progressive increase in readings could be
due to lubr icat ion breakdown, or wear.
Lub ricate and retest. If readings are again
elevated after a sho rt period of tim e, the
bearing is on th e road to fai lure. Click when ready...
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Video Clip
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Spectrum AnalysisInexpensive software packages are also available. Here the
sounds were recorded with a cassette and played back into a PC.
Click when ready...
This graph shows the low level
of ultrasound from the motor
side bearing of a high-speed
overhung cantilever fan. The
sou nd is barely audib le.
This trace shows the fan side
bearing, approximately one foot
away, on the same fan. The
excessive ultrasound was due
to a bent fan shaft.
Click to hear!
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What is the difference between
Sound and Vibration?
VIBRATION:Any mechanical oscillatory motion of a machine
member.
SOUND:Vibration of air molecules (airborne sound), or
molecules in solids (solid borne sound).
Sound is the precurso r to vibrat ion. It is
vibrat ion that is too fast, and w ith an amp li tude
too small to move large masses.
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Why use Ultrasound on bearings?
n As a compliment to vibration analysis.
Test more points in less time.
Little training needed, less equipment to carry. Allows you to perform PM on less critical equipment
Increase window of prediction.
May see elevated ultrasonic levels before changes in vibration
are present.
Effective at fault detection on slow speed equipment. Help determine lubrication intervals and amounts.
Listen to sound levels decrease as lubricant is induced.
n As a stand alone program.
Capable of establishing basic trends and alarm levels.
Use your ear andinstrument readings to confirm problems. Inexpensive, and easy to use; little training required.
Excellent start for those implementing first PM program.
Very versatile
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AccuTrakUltrasonic Inspection Instruments
n Model VPE-1000
Low cost digital
n Model VPE-2000
Advanced Digital
n Model VPX-WR
The ultimate air leak detector
featuring DND technology
n Combo Package
Offers the best of everything
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Produc t l ine overview
Superior Signal has been provid ing excellent products at affordable prices for o ver
40 years. We are the only comp any offer ing true innovat ions in ul t rasonic inspect ion
technology. To prove i t , we hold 4 of the mo st recent ly issued patents in the f ie ld.
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AccuTrak
Model VPE-1000
When powerfu l perform ance is needed and bu dgets are limi ted,
ch oo se the versat i le VPE-1000. It is the first low c os t digital ultrason ic
detector of fer ing extraordinary features at a fract ion of th e cost o fother ul trasonic instrum ents!
Digi tal LED indicators (Alph anumeric and Bargraph)
Digital Peak Hold
Separate Volume & Sensit iv i ty
Dual Senso rs (no changing heads)
Perfect for hospitals, schools, hotels, and other large institutional or light
industrial environments.
Excellent for steam trap testing!Click when ready...
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AccuTrakModel VPE-2000
First in dig ital ultrason ics th e VPE-2000 is rich in features,
yet remains compact and easy to use. In addit ion to
everythin g offered o n t he VPE-1000, the VPE-2000 also
of fers selectable frequency mo des, including sonic m ode.
Digi tal LED indicators (Alphanumeric and Bargraph)
Digital Peak Hold
Digi tal ly tuned for maximum repeatabi l i ty
Separate Volume & Sensit iv i ty
Dual Senso rs (no changing heads)
5 sensor/ f requency modes, includin g SONIC
Includ es var iety of accessor ies (prob e extension s & mo re)
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Video Clip
Note:Format of video may not be compatible with all media drivers, and maynot run on your computer. I f video does not start automatical ly, try cl icking
withi n f rame to start and stop video.
Click when ready...
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AccuTrakCombo Offer
Get the best of Both,
Two units, One Great Price!
Allows you to have two people, with two
ins t ruments per forming numerous tasks. Combo
offer includes o ne Model VPX-WR and o ne Model
VPE-2000; Two s tate of the art instruments for the
price of one analog gun type detector.
Click when ready...
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Hit Escape to exit the program now.
For more informat ion o n ul t rasonic inspect ion contact ...
SuperiorSignal Company
P.O. Box 96
Spotswood, NJ 088841-800-945-TEST, or (732) 251-0800
www.SuperiorSignal.com
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