usintro ultrasonics

8/12/2019 USintro Ultrasonics

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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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A few InstructionsUse the following icons to move through the presentation...

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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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withi n f rame to start and stop video.

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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.

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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



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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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