Ultrasound in Leak Detection

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Ultrasound in Leak Detection
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Passive Ultrasound Sources

• Leaks
• Pressure
• Vacuum
• Steam
• Valves
• Hydraulic
• Electrical

• Rolling Elements
• Bearings
• Gearboxes
• Sheaves
• Couplings
• Pumps

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Leaks
Definition
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
P1
P2
P1gtP2
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Introduction
Reasons for leak detection

• 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

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Pressure - Vacuum
Comparing methods for leak detection

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

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Introduction
Medium of Transport

• Airborne
• Pressure
• Vacuum
• Steam traps
• Electrical

• Structure borne
• Vacuum
• Valves Steam traps
• Hydraulic

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Leaks
External leaks pressure and vacuum leaks
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Pressure - Vacuum
Understanding the turbulence

• When a fluid moves from a high pressure zone to
• a low pressure zone, friction between fluid
  molecules and medium molecules generate
  ultrasonic waves

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Pressure - Vacuum
What is the cost of air?
Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line Air leaks in scfm according orifice size and Pressure in line 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
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Cost to compress 1 CFM of air

• 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

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Pressure - Vacuum
Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars Leaks - yearly cost in dollars 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
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Pressure - Vacuum
Leak factor factors affecting leaks

• Pressure differential
• Orifice size and shape
• Fluid viscosity

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Pressure - Vacuum
Procedure for leak detection
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Pressure - Vacuum
General considerations

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

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Pressure - Vacuum
Safety

• 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.

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Pressure - Vacuum
Know the system

• 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

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Pressure - Vacuum
Know the system
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Pressure - Vacuum
Select the right equipment
1. Ultrasonic detector with tuneable frequency,
accessories, batteries fully charged 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
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Pressure - Vacuum
Planning the inspection

• 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)

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Pressure - Vacuum
Execute the inspection
End
End use points
Begin
Compressors
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Leak Detection
Managing the inspection area
1. Shielding Technique Place a barrier between
different ultrasound sources 2.
Positioning Look for the best body/sensor
position 3. Covering Place a barrier around the
inspection point to block other competing
ultrasounds 4. Managing Reflection Large leaks
reflecting off of hard surfaces may create false
positives
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Leak Detection
Managing the inspection area

• Shielding Technique
• Blocking a known source
• Enables inspector to hear additional leaks in
  near vicinity
• Use a cloth, a rag, a piece of foam, or even a
  gloved hand (gloved for safety)

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Leak Detection
Managing the inspection area

• Positioning
• Using the body to block a known source of
  competing ultrasound
• Enables inspector to find additional leaks

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Leak Detection
Managing the inspection area

• Covering
• Minimizing the inspection area
• Blocks all competing ultrasounds
• Especially useful finding vacuum leaks

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Leak Detection
Managing the inspection area

• Managing Reflection
• Ultrasonic 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

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Leak Detection
Leak Detection Techniques

• 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

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Leak Detection
Documentation and reporting

• 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

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Leak Detection
Documentation examples
Leak Location PSIG oC GAS cfm Comments

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Leak Detection
Take action

• It is often noted that finding a leak never
  saved a dime
• and 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 100s 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
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Valve InspectionUsing Ultrasound
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Valves
Two ways to check
1. Contact the valve and listen
2. Do a comparison method before and after the
valve
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Easy as A B C

• Checking valve for flow
• Upstream and downstream
• Works for any gas or liquid

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Hydraulic Systems

• Benefits
• Find internal leaks
• and passing valves
• Find cavitation
• Perform inspection
• without disassembly
• Save time

Use contact sensor
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Hydraulic Systems

• Example
• Cavitation in a pump

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• Steam Traps and Ultrasound

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Steam Traps
What is steam?

• 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

970 BTU
142 BTU
1 lb. water at 70 oF
1 lb. water at 212 oF
1 lb. steam at 212 oF
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Steam Traps
Properties of saturated steam
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Steam Traps

• Steam application
• Heating
• Industrial
• Home
• Industrial processes
• Distillation
• Humidification
• Cleaning

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Steam Traps
What is a steam trap?

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

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Steam Traps
How steam traps operate
Velocity
Density
Temperature
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Steam Traps
Effects of air in heating system

• 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

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Steam Traps

• Temperature reduction caused by air

Pressure Psi Temp. oF steam Temperature of steam mixed with different percentages of air (volume) Temperature of steam mixed with different percentages of air (volume) Temperature of steam mixed with different percentages of air (volume)
Pressure Psi Temp. oF steam 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
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Steam Traps

• 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.

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Steam Traps

• Effects of condensate in a heating system
• Dramatic decrease in heat transfer capability of
  system
• Occurrence of water hammer in steam lines

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Steam Traps
Efficient heating system

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

Steam traps do the job!
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Steam Traps
Inverted bucket

• Operation Density
• How 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 mode
• Open

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Steam Traps
Float and thermostatic

• Operation Temp./Density
• How 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 mode
• Closed

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Steam Traps
Thermostatic

• Operation Temperature
• How its works
• The float operates on the basis of a difference
  between steam and condensate
• Usual failure mode
• Open

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Steam Traps
Visual inspection

• Venting live steam to the atmosphere

Can pose safety issues
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Steam Traps
Ultrasonic inspection

• Allows one to hear inside the trap

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• New generation of ultrasound systems can record
  scalable, comparable time signals
• Now instead of just listening we can compare

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Trap example

• Good trap
• Temp 225 F
• Max RMS (43.3 dBµV) is higher than RMS (29.7
  dBµV) Peak (51.7 dBµV)

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Trap example

• Failed closed
• Temp 140 F RMS is low (9.4 dBµV)
• Max RMS (11.5 dBµV) is close to RMS

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Trap example

• Failed open
• Temp 226 F, RMS is high (39.5 dBµV)
• Max RMS is close to RMS (41.9 dBµV)

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You Decide
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Steam Traps
Thermal inspection

• Upstream and downstream temperature are taken and
  compared

T1
T2
Can be affected by back pressure
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Steam Traps

• The value of a
• steam trap inspection programme
• Promotes efficient heating system
• Save in chemicals, fuel, material and
  maintenance costs

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Lots of info here
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• Know the operating pressure of the steam system
  to determine the system temperature
• Subtract 10 for heat transfer through pipe

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• Questions??

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Electrical Leaks
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Electrical Leaks
Safety
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
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Electrical Leaks
Electrical risks

• Shock
• Arc Flash NFPA 70e
• Arc Blast

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Electrical Leaks
Shock

• Current can pass through the human bodys nervous
• or 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.

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Electrical Leaks
Arc flash

• An extremely high temperature conductive plasma
  and gases
• resulting from an arc fault incident. As many as
  80 percent of
• all electrical injuries are burns resulting from
  an arc-flash
• contact and ignition of flammable clothing. Arc
  temperatures
• can reach 35,000 F four times hotter than the
  suns surface.
• Arc-flash can cause second and third degree
  burns.

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Electrical Leaks
Arc blast

• 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.

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Electrical Leaks

• Faults lead to failure
• Short Circuit
• Fires
• Transformer explosion
• Outages
• Machine damage
• Electrocution

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Electrical Leaks
Where to inspect

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

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What Look For

• Electrical discharge or faults
• Corona
• Nuisance corona
• Destructive corona
• Tracking
• Arcing
• All faults exist to find ground

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What is Partial Discharge?

• 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)

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What is Partial Discharge?

• PD is a localized electrical discharge in an
  insulation system that does not completelybridge
  the electrodes.

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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Corona Discharge
Corona discharge

• 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 Characteristic Steady, regular,
popping sound
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Corona Discharge
Corona what is it?

• 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

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Corona Discharge

• Why locate corona discharge
• Leads to more serious electrical problems
• Breakdown of components - corrosion
• Unexpected shutdowns
• Fire and explosion
• Waste of electricity

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Corona Discharge

• Corona characteristics
• Two 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

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Corona Discharge

• Corona signature displayed using AVM Ultranalysis

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Tracking
Tracking characteristics

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

• 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

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Arcing
Arcing characteristics

• 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

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Arcing

• Arcing Signature as displayed using AVM
  Ultranalysis

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Performing the Inspection

• Safety First
• Know your environment
• Note the ambient temperature
• Note the conditions, humidity, dusty, etc.
• Know the equipment
• Document your findings

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Electrical Applications

• Use ultrasound to find electrical faults
• Arcing
• Tracking
• Corona
• Special areas
• Flow
• Loose part monitoring

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Measurement Cycle

• Find it, Fix it, Check it

BEFORE CLEANING
AFTER CLEANING
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Sensor Options

• Field inspections
• Medium distance
• Long distance
• Plant inspection
• Short distance
• Contact

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Sensor Options

• Field inspection

Long range Parabolic dish Use up to 200 ft (60
mts) Medium range Extended Distance Sensor Use
up to 30 ft (10 mts)
Scan 360 o up and down, right to left listening
for characteristic fault sounds
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Sensor Options

• Plant inspection

Short range Internal Sensor or EDS Contact Flexib
le Sensor or magnetic sensor
Scan between doors grooves listening for
characteristics fault sounds
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Sensor Options

• Plant inspection-airborne

• 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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Sensor Options

• Plant inspection-structure borne

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

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Questions???