Ultrasound in Leak Detection

Training Level 1 Version 2.0 1

Ultrasound in Leak Detection

Certification Training Level 1 Version 2.0

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Leaks

Pressure

Vacuum

Steam

Valves

Hydraulic

Electrical

Rolling Elements

Bearings

Gearboxes

Sheaves

Couplings

Pumps

Passive Ultrasound Sources


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Leaks happen when a fluid, gas or liquid goes from a high pressure to a low pressure medium through a hole that is

not supposed to exist, usually accompanied by irreversible lost of material and / or energy

Leaks

P1

P2 P1>P2

Definition


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• Safety• Explosions – Combustible fluids • Poison – Toxic/Corrosive gases

• Economic • Avoid material loss from leakage • Efficient energy management• Maintain efficient and reliable processes

• Quality control• Maintenance management• Detect faulty components• Decrease warranty cost

Introduction

Reasons for leak detection


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• Immersion or dunk method • Chemical trace• Chemical penetration• Gas sniffing• Airborne ultrasound• Soap method • Pressure decay• Search gas tracer probe• Water Tunnel

Pressure - Vacuum

Comparing methods for leak detection


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Airborne– Pressure– Vacuum– Steam traps– Electrical

Structure borne– Vacuum– Valves & Steam traps– Hydraulic

Introduction

Medium of Transport


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Leaks

External leakspressure and vacuum leaks


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When a fluid moves from a high pressure zone to

a low pressure zone, friction between fluid molecules and medium molecules generate ultrasonic waves

Pressure - Vacuum

Understanding the turbulence


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Air leaks in scfm according orifice size and Pressure in line

PSI 1/64” 1/16” 1/4 “ 3/8 “ 1/2 “ 5/8 “ 3/4 “ 7/8 “

5 0.062 0.99 15.9 35.7 63.5 99 143 195

40 0.194 3.1 49.6 112 198 310 446 607

100 0.406 6.49 104 234 415 649 394 1,272

120 0.476 7.62 122 274 488 762 1,097 1,494

Air is free, compressed air is not

Pressure - Vacuum

What is the cost of air?


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Assumptions•Motor service Factor = 110% •Power Factor = 0.9

•A typical compressor produce 4 CFM per 1 HP

1 HP = 110% x 0.746 KW/0.9 = 0.912 KW This means that produce 1 CFM = 0.228 kW With a cost of 0.06 $/kW/hr : 1 CFM = $0.0137/hr the 1 CFM in 8000 hr operations hours cost a year: 1 CFM x 8000 hr x 0.0137 $/hr = $109.6

Cost to compress 1 CFM of air


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Leaks - yearly cost in dollars

PSI 1/64” 1/16” 1/4 “ 3/8 “ 1/2 “ 5/8 “ 3/4 “ 7/8 “

60 19 305 4,884 10,991 19,538 30,529 43,962 59,837

90 26 427 6,846 15,404 27,385 42,790 61,618 83,869

100 29 468 7,500 16,875 30,001 46,877 67,503 91,879

120 34 550 8,808 19,818 35,232 55,051 79,273 107,900

Assuming energy cost 5 cents per Kw-h, and 365 operation days

Pressure - Vacuum


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• Pressure differential

• Orifice size and shape

• Fluid viscosity

Pressure - Vacuum

Leak factorfactors affecting leaks


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Pressure - Vacuum

Procedure for leak detection


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• Safety• Know the system• Select most suitable collector and accessories• Plan the inspection• Execute the inspection • Document and report findings• Take action

Pressure - Vacuum

General considerations


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There is no single rule of thumb for leak inspection safety.

Each and every circumstance can be different so SDT

encourages the Inspector to seek advice and guidance

from qualified safety personnel in each facility.

All safety procedures must be followed and every risk must

be avoided.

Pressure - Vacuum

Safety


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• Get updated layouts and blueprints of the air system

• Identify flow direction – supply / demand• Identify system components• Identify consumption points – general demand

and point demand by users

Pressure - Vacuum

Know the system


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Pressure - Vacuum

Know the system


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1. Ultrasonic detector with tuneable frequency, accessories, batteries fullycharged

2. Surfactant to intensify acoustic signal (to detect very small leaks)

3. Paper to record leaks

4. Tags to identify leaks

5. Flashlight, blueprints / Layouts

6. Thick fabric to shield and isolate leaks

Pressure - Vacuum

Select the right equipment


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• Define route to follow from the layouts or blueprints• Identify points most likely to have leaks

accessories (lubricators, filters, pipe unions, valves etc.) accessories threaded – welded, pneumatic tools

• Select most appropriate sensors• Prepare a list with required information• Coordinate with floor supervisors for the best time

to do the inspection – maximum pressure in the lines (low demand)

Pressure - Vacuum

Planning the inspection


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Begin

Compressors

End

End use points

Pressure - Vacuum

Execute the inspection


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1. Shielding TechniquePlace a barrier between different ultrasound sources

2. PositioningLook for the best body/sensor position

3. CoveringPlace a barrier around the inspection point to block other competing ultrasounds

4. Managing ReflectionLarge leaks reflecting off of hard surfaces may create false positives

Leak Detection

Managing the inspection area


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Shielding TechniqueBlocking a known source

Enables inspector to hear additional leaks in near vicinityUse a cloth, a rag, a piece of foam, or even a gloved hand (gloved for safety)

Leak Detection



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Leak Detection

PositioningUsing the body to block a known source of competing ultrasound

Enables inspector to find additional leaks



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Leak Detection

CoveringMinimizing the inspection area

Blocks all competing ultrasoundsEspecially useful finding vacuum leaks



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Managing ReflectionUltrasonic energy reflects

more than it absorbs

Ultrasound from turbulence reflects off hard surfaces

Sometimes, it seems as though a leak is coming from

a brick wall!

Follow the angle to the source

Leak Detection



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Special situations when pressure is not feasible

Threshold Leaks (= 10-2 std – cc/sec, 10 psi) At this level very little ultrasonic disturbance reaches the detector. Using the Acoustic Leak Magnifier the signal is intensified.

Un pressurized Systems

A bi sonic transmitter is used

Leak Detection

Leak Detection Techniques


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• When a leak is found it must be identified, and if possible, quantify the air loss using:

• Mass flow sensor• Graph Intensity versus volume• Sizing orifice (formula)

• Use a tag to identify the leak position• Document a leak report

Leak Detection

Documentation and reporting


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Leak # Location PSIG oC GAS cfm Comments

Leak Detection

Documentation examples


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“It is often noted that finding a leak never saved a dimeand no truer words can be spoken on the subject of ultrasonic compressed air

leak detection. As satisfying as it may be to spend 8 hours identifying 100’s of compressed air leaks, there is no payback in wrapping a yellow ribbon

around a leaking pipe fitting. It has to be fixed to save “

Dan Durbin, Chief Engineer, Anheuser-Busch, St. Louis, Missouri

Costs $

Leak Detection

Take action

Valve Inspection

Using Ultrasound


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2. Do a comparison method before and after the valve

1. Contact the valveand listen

Two ways to check

Valves

Easy as A B C • Checking valve for flow

– Upstream and downstream– Works for any gas or liquid


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Benefits• Find internal leaks

and passing valves• Find cavitation• Perform inspection

without disassembly• Save time

Use contact sensor

Hydraulic Systems


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Example

Cavitation in a pump

Hydraulic Systems

Steam Traps and Ultrasound


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it is vaporised water produced by adding heat energy to its boiling point, then more energy is given to change water to steam without further increasing the temperature

1 lb. water at 70 oF

1 lb. water at 212 oF

1 lb. steam at 212 oF

+ 142 BTU + 970 BTU

Steam Traps

What is steam?


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Gage Absolute Steam Heat of Latent Heat Total Heat Specific

Pressure Pressure Temperature Saturated Btu/lb of Steam Volume

Psig Psia F Liquid, Btu/lb Btu/lb cu ft/lb

-5.49 12.00 201.96 169.96 976.60 1146.60 32.40

0.00 14.70 212.00 180.07 970.30 1150.50 26.80

10.30 25.00 240.07 208.42 952.10 1160.60 16.30

50.30 65.00 297.97 267.50 911.60 1179.10 6.66

100.00 114.70 337.90 308.80 880.00 1188.80 4.23

150.30 165.00 365.99 338.53 857.10 1195.60 2.75

200.30 215.00 387.89 361.91 837.40 1199.30 2.13

250.30 265.00 406.11 381.60 820.10 1201.70 1.74

Steam Traps

Properties of saturated steam


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Steam application

Heating– Industrial

– Home

Industrial processes– Distillation

– Humidification

Cleaning

Steam Traps


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It is an automatic valve that opens for condensate, air and carbon dioxide (CO2) and closes for steam

Steam Traps

What is a steam trap?


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Steam Traps

How steam traps operate

Density Temperature Velocity

http://www.climaticcontrol.com/info/jjzgate/Infotec/Info-Tecs21-30/Infotec_29(rev1)_files/image008.gif

http://www.climaticcontrol.com/info/jjzgate/Infotec/Info-Tecs21-30/Infotec_29(rev1)_files/image008.gif


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• Occupies precious space in the steam line • Air/steam mix has less calorific energy to

transfer • Insulating property of air acts as heat transfer

barrier

Steam Traps

Effects of air in heating system


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Temperature reduction caused by air

Pressure

Psi

Temp. oF

steam

Temperature of steam mixed with different percentages of air (volume)

10 % 20 % 30 %

10.3 240.1 234.3 228 220.9

25.3 267.1 261 254.1 246.9

50.3 298 291 283.5 275.1

75.3 320.3 312.9 304.8 295.9

100.3 338.1 330.3 321.8 312.4

Steam Traps


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Effects of CO2 in a heating system

CO2 enters the system as carbonates from the feed water, a few ppm stays after the DI plant and mixes with the cooled condensate to form carbonic acid which is highly corrosive.

Steam Traps


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Effects of condensate in a heating system

Dramatic decrease in heat transfer capability of system

Occurrence of water hammer in steam lines

Steam Traps


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Air, CO2 and condensate are removed as quickly and as completely as possible

Steam traps do the job!

Steam Traps

Efficient heating system


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Operation: DensityHow it works

Uses the difference in density between condensate and steam.

When steam is predominant the trap is closed

When condensate is predominant the trap is open

Usual failure modeOpen

Steam Traps

Inverted bucket


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Operation: Temp./DensityHow its works

Float traps work on the basis of

the difference in density between

steam and condensate.

A thermostatic element opens a

valve when the trap cools to a

specified temperature

Usual failure modeClosed

Steam Traps

Float and thermostatic


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Operation: TemperatureHow its works

The float operates on the basis of a difference between

steam and condensate

Usual failure mode

Open

Steam Traps

Thermostatic


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Venting live steam to the atmosphere

Can pose safety issues

Steam Traps

Visual inspection


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Allows one to hear inside the trap

Steam Traps

Ultrasonic inspection

New generation of ultrasound systems

can record scalable,

comparable time signals

Now instead of just listening we can

compare:

Trap example Good trap:Temp 225 F

• Max RMS (43.3 dBµV) is higher than RMS (29.7 dBµV) Peak (51.7 dBµV)

RMS

Max RMS

Trap example Failed closed:

• Temp 140 F RMS is low (9.4 dBµV)

• Max RMS (11.5 dBµV) is close to RMS

RMSMax RMS

Trap example Failed open:

• Temp 226 F, RMS is high (39.5 dBµV)

• Max RMS is close to RMS (41.9 dBµV)

RMS

Max RMS


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You Decide


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Upstream and downstream temperature are taken and compared

Can be affected by back pressure

T1 T2

Steam Traps

Thermal inspection


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The value of a

steam trap inspection programme

Promotes efficient heating system

Save $$$ in chemicals, fuel, material and maintenance costs

Steam Traps

Lots of info here


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Keep Your Trap Shut Application Video Tutorial Series

Take Upstream Temperature

If Temp is too low If Temp is normal

Know the operating pressure of the steam system to determine the system temperature

Subtract 10% for heat transfer through pipe


If Temp is too low

CONFIRMIs Trap in Service?

NO! YES!

Listen to Ultrasound

Signal

Diagnosis Not Possible


If Temp is too low

Trap is in Service

Listen to Ultrasound Signal

Signal is Low & Constant

Trap is Failed in Closed Position

or there is a blockage up or downstream


If Temp is Too Low

Trap is in Service

Ultrasound Signal is Irregular

Record Dynamic Signal

Record Upstream Temperature

Compare data with a good trap to build a reliable diagnosis and baseline data


If Temp is Normal


Distinct On/Off Cycles

Yes No



Yes No

Confirm Downstream Temperature

Trap is in good condition



Yes No


Rushing Sound and High U/S Signal?

Yes No


Rushing Sound and High U/S Signal?

Yes No

Large Leak, Failed Trap in Open Position

Record Dynamic Measurement

Record Upstream Temperature

Analyze Time Signal to detect an early stage failure or confirm the good condition

of the trap


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Questions??


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Electrical Leaks


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There are no second chances

Learn and follow the safety procedures

Know your work environment

If have doubts, clarify them with a safety supervisor

Obey and understand reasons for lockouts

Safety

Electrical Leaks


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• Shock

• Arc Flash NFPA 70e

• Arc Blast

Electrical Leaks

Electrical risks


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Current can pass through the human body’s nervousor vascular systems, and across the surface of the body. The current required to light a 7 1/2 W, 120 V lamp, passing through the chest, can cause death. Of those killed while working on voltages below 600 V, half were intentionally working on "hot" energised equipment. Most electrocutions can be avoided with proper training, planning, job preparation,

procedures, and equipment.

Electrical Leaks

Shock


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An extremely high temperature conductive plasma and gasesresulting from an arc fault incident. As many as 80 percent ofall electrical injuries are burns resulting from an arc-flashcontact and ignition of flammable clothing. Arc temperaturescan reach 35,000 F four times hotter than the sun’s surface.Arc-flash can cause second and third degree burns.

Electrical Leaks

Arc flash


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A pressure wave caused by the rapid expansion of gases and conducting material with high flying molten materials and shrapnel. An arc-blast may result in a violent explosion of circuit components and thrown shrapnel. The blast can destroy structures, and knock workers from ladders or across a room. The blast can rupture eardrums and collapse lungs.

Electrical Leaks

Arc blast


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Faults lead to failure

• Short Circuit• Fires• Transformer explosion• Outages• Machine damage• Electrocution

Electrical Leaks


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• Transformer stations• Switchgears• Relays• Bushings• Transmission lines • Street poles• Junction boxes and circuit breakers • Bus bars• Insulators

Electrical Leaks

Where to inspect


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Electrical discharge or faults• Corona

• Nuisance corona

• Destructive corona

• Tracking• Arcing

All faults exist to find ground

What Look For


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Phenomenon that only occurs at high AC voltages (usually above 2000 V ac rms phase-to-phase)

Usually only problematic above 4000V

Is exaggerated at higher altitudes

The higher the voltage, the more destructive the activity

PD is a leading cause and indicator of insulation breakdown (will detect many mechanical defects)

What is Partial Discharge?


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PD is a localized electrical discharge in an insulation system that does not completely

bridge the electrodes.

What is Partial Discharge? Arc or Spark

Phase-conductor to Phase-conductor or

Phase-conductor to Ground

PD is destructive


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PD activity is influenced by– Voltage– Shape of void– Temperature– Insulation condition– Environmental influences

Time before failure is therefore related to these factors


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a discharge, frequently luminous, at the

surface of a conductor or between two

conductors of the same transmission line,

accompanied by ionisation of the

surrounding atmosphere and often by a

power loss.

Does not generate heat

Ultrasonic Sound CharacteristicSteady, regular, popping sound

Corona Discharge

Corona discharge


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• Atomic reaction which produces ionisation due to• electron movements• Ozone and nitrogen oxide are produced• High humidity makes it worse• Result: Breakdown of insulating compounds

Corona Discharge

Corona – what is it?


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Why locate corona discharge

• Leads to more serious electrical problems

• Breakdown of components - corrosion

• Unexpected shutdowns

• Fire and explosion

• Waste of electricity

Corona Discharge


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Corona characteristicsTwo types of Corona activity

•Nuisance Corona•Can be caused from dirty insulators or bushings and high humidity•Does not pose an immediate threat•Is wasteful

•Destructive Corona•Steady frying or buzzing sound accompanied•with an intermittent popping sound•Lower deeper sound •Oxidation by-products are being produced

Does not generate heat

Corona Discharge


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Corona signature displayed using AVM Ultranalysis

Corona Discharge


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• Exists to find ground. Uses any carbon build up to track as it starts a path toground

• As intensity builds, and as the amplitude increases and builds to a point of “flashover”, discharge occurs and starts this process all over again

• This condition normally requires immediate attention

• Record and save wave files for comparisons with colleagues

Tracking does not generate heat unless its very intense

Tracking

Tracking characteristics


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• The flow of electricity through the air from a conductor to another object that conducts electricity

• Clear indication of insulator failure• All electricity to ground (wasteful)• Ultrasonic sound pattern is a quick

stop and start at random intervals• Violent sound

Arcing

Arcing


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•Arcing can be seen with Infrared•Infrared and Ultrasound used together is most effective

in an electrical inspection.•Arcing is often accompanied by heat•Arcing can be identified as an “abrupt start and stop”.•Can be violent•When heard, should be inspected by a qualified technician

Arcing

Arcing characteristics


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Arcing Signature as displayed using AVM Ultranalysis

Arcing


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• Safety First

• Know your environment

• Note the ambient

temperature

• Note the conditions,

humidity, dusty, etc.

• Know the equipment

• Document your findings

Performing the Inspection

Electrical Applications

Use ultrasound to find electrical faults– Arcing– Tracking– Corona– Special areas

• Flow• Loose part monitoring

BEFORE CLEANING AFTER CLEANING

• Find it, Fix it, Check it

Measurement Cycle


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• Field inspections• Medium distance• Long distance

• Plant inspection• Short distance• Contact

Sensor Options


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Long rangeParabolic dish

Use up to200 ft (60 mts)

Medium rangeExtended Distance

SensorUse up to

30 ft (10 mts)

Scan 360 o up and down, right to left listening for characteristic fault sounds

Sensor Options


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Plant inspection

Short rangeInternal Sensor or

EDSContact

Flexible Sensor or magnetic sensor

Scan between doors grooves listening for characteristics fault sounds

Sensor Options


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Plant inspection-airborne

Sensor Options

• transmission line insulators, • bushings, • dry type transformers and reactors, • exposed joints and connections, • medium voltage switchgear panels, • cable terminations, • low voltage MCC panels.


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Plant inspection-structure borne

Sensor Options

• Oil cooled transformer core• windings • tap changers • trending can also be useful here if the load is

relatively constant


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Questions???

Ultrasound in Leak Detection

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