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Training Level 1 Version 2.0 1
Ultrasound in Leak Detection
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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
Managing the inspection area
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Leak Detection
PositioningUsing the body to block a known source of competing ultrasound
Enables inspector to find additional leaks
Managing the inspection area
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Leak Detection
CoveringMinimizing the inspection area
Blocks all competing ultrasoundsEspecially useful finding vacuum leaks
Managing the inspection area
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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
Managing the inspection area
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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
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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
Keep Your Trap Shut Application Video Tutorial Series
If Temp is too low
CONFIRMIs Trap in Service?
NO! YES!
Listen to Ultrasound
Signal
Diagnosis Not Possible
Keep Your Trap Shut Application Video Tutorial Series
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
Keep Your Trap Shut Application Video Tutorial Series
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
Keep Your Trap Shut Application Video Tutorial Series
If Temp is Normal
Listen to Ultrasound Signal
Distinct On/Off Cycles
Yes No
Keep Your Trap Shut Application Video Tutorial Series
Distinct On/Off Cycles
Yes No
Confirm Downstream Temperature
Trap is in good condition
Keep Your Trap Shut Application Video Tutorial Series
Distinct On/Off Cycles
Yes No
Listen to Ultrasound Signal
Rushing Sound and High U/S Signal?
Yes No
Keep Your Trap Shut Application Video Tutorial Series
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???