Transcript Severn Trent - Blue Gold Technology

Introduction to Correlation
General
 Please TURN OFF Mobile Phones!
 Special requirements for lunch
 Smoking
 Toilets
 Coffee Breaks
 Fire procedures
 Health & Safety while on site
Before we start
Tell us about yourself:
 Where do work?
 What is your Job?
 How long have you been doing it?
 What have you done in the past?
 What would you like to get out of the
course?
 What are your interests?
1. Background to Leak Noise
2. Correlator Terminology & Principles
3. Correlator Development
4. Correlator Equipment
5. Setting Up and Getting Started
6. Basic on Site Setup
7. Leak Field Correlation
8. Interpreting Results
9. Extra Features
10. Sources of Error
11. Velocity Check
12. Equipment Fault Checks
13. Other leak detection processes (LLP)
13. TEST !!
Background to Leak Noise
Different Noise Sources
 Leakage
 Partial obstruction of pipe bore (foreign object)
 Consumption
 Pressure reducing valves (PRV’s)
 Partially closed valves (throttled or passing)
 Close proximity of main to sewer/culvert pipe
 Changes in pipe diameter
 Water pumping
 Electrical interference
 Pipe lining
Leak Noise Quality
 Important Factors
- Clarity
- Strength
 Good Leak Noise
- Clear, light & easy to distinguish
- Strong & easy to hear
 Poor Leak Noise
- Dull, muffled & difficult to distinguish
- Weak & difficult to hear
Short section of water filled pipe
Mechanical
vibration
Pressure wave
Rupture
Pipe / Rupture with vibration & pressure wave
Section of water filled pipe
buried in hard backfill
High
pressure
inside pipe
Low pressure
outside pipe
Rupture
Water draining away
Hard backfill diagram
High pressure
inside pipe
Section of water filled pipe
buried in soft backfill
Water filled cavity
due to collection
in backfill
Rupture
Back pressure
Outside pressure
increasing as cavity
fills with water
Soft backfill diagram
Acoustic noise transfer from a leak in a pipe
Energy generated from the leak is
transmitted within the pipe through the water
energy from the leak is also
transmitted through the pipe wall
burst
Pressure within pipe is lost
Complete
rupture
Complete rupture diagram
Pressure
maintained
within pipe
Small rupture
Small rupture diagram
Different Material Types
 Steel
 Hardest material
 Ductile Iron
 Copper
 Asbestos Cement
 Lead
 PVC
 Polyethylene
 Softest material
Leak Noise Factors
F a c to rs p ro d u c in g g o o d
q u a lity le a k n o is e
H ig h w a te r p re s s u re
H a rd b a c k fill
S m a ll ru p tu re
C le a n p ip e s
M e ta llic p ip e s
S m a ll d ia m e te r p ip e s
F a c to rs p ro d u c in g p o o r
q u a lity le a k n o is e
L o w w a te r p re s s u re
S o ft b a c k fill
S p lit m a in s
E n c ru s te d p ip e s
S o ft/L in e d p ip e s
L a rg e d ia m e te r p ip e s
140 dB pain threshold
(100 Watts/Metre
2
)
130 dB
120 dB
2 minutes exposure
can damage hearing
110 dB noise from a concert
100 dB
8 hours or more exposure
can damage hearing
radio playing loudly
90 dB noisy factory (many people talking)
80 dB vacuum cleaner noise
70 dB
60 dB
normal speech
50 dB
40 dB very quiet noise
30 dB
20 dB
10 dB
0 dB Threshold of hearing
10
-12
Watts/Metre
2
@ 1KHz
100
40 dB - 100 dB - Leak found with
noise loggers & usually with conventional
methods
dB
10 dB - 40 dB - Leak found with noise
40
loggers only, correlation generally required
10
0
0 dB - 10 dB - No leaks
Leaks on plastic pipes are often found at intensities of 20-40dB
Principal of Correlation
To obtain a good correlation display, noise MUST be
heard at each sensor
A
B
Similar sounds
Dissimilar
sounds
Correlation Formula
L = D - (V x Td)
2
L
= Leak position (m) (meters)
V
= Velocity of sound along pipe (m/ms) (meters per millisecond)
D
= Length of pipe (m) (meters)
Td = time delay (ms) (milliseconds)
Velocity of Sound
Velocity
Speed
- movement in a specified direction
- movement in any direction
In practice, for most correlator users, Speed = Velocity
Speed / velocity = SOUND WAVE travelling along a pipe network
For all practical purposes the speed of water is not important.
Typical water velocity = 2 m/s
Typical speed of sound through iron pipe = 1300 m/s
Factors Affecting Velocity
 Material - metallic (harder materials) are faster; plastics (softer
materials) are slower
 Size - The larger the pipe diameter, the slower the velocity of sound
 Age (internal and external condition)
 Repairs (using mixed materials)
Time Delay
If a leak was exactly midway between the two correlation
points, the noise pattern would be identical.
If a correlated leak is closer to one sensor than the other,
then there is a “Time Delay”(of only a fraction of a second)
for noise to reach the furthest sensor.
The Principal of Leak Noise Correlation
Leak Noise
Correlator (LNC)
B Transmitter
Transmitter A
Valve
chamber
Valve
chamber
D1
Velocity of
leak sound
+
D2
Time delay of leak sound
arriving at each sensors
=
Precise location
of leak in pipe
..and the same with a ‘CORDLESS’ LNC
Cordless LNC
Transmitter
Valve
chamber
Transmitter
A
B
Valve
chamber
CORDLESS Transmitters can often be
positioned below ground, INSIDE valve
chambers, with valve chamber closed
But more about that later
Correlation Formula
D = 100m, v = 1m/ms, Td = 80ms towards ‘A’
Substitute in correlation formula
L
= 100 - (1 x 80)
Order of calculation
2
1.
Multiply
= 100 - 80
2.
Subtract
2
3.
Divide
= 20
2
= 10m (Transmitter ‘A’)
Examples
L = D - (V x Td)
Correlation formula examples
2
L = Leak position (m)
D = Length of pipe (m)
1.
D = 150m
2.
D = 70m
3.
D = 300m
V = Velocity of sound along pipe (m/ms)
Td = time delay (ms)
V = 1.2 m/ms Td = 60ms (Transmitter A)
V = 0.6 m/ms Td = 0ms (Transmitter A)
V = 0.2 m/ms Td = 70ms (Transmitter B)
4.
5.
6.
V = 0.9 m/ms Td = 6ms (Transmitter A)
V = 0.11 m/ms Td = 100ms (Transmitter B)
V = 1.0 m/ms Td = 80ms (Transmitter A)
D = 200m
D = 700m
D = 80m
Calculating with the wrong distance
If Velocity = 1.28, Time Delay = 28.2
& Distances change from 150, 145, 120m
L=150 - (1.28 x 28.2)
2
L=150 - 36.09
2
L=113.91
2
Length= 56.95m
L=145 - (1.28 x 28.2)
2
L=145 - 36.09
2
L=108.91
2
Length= 54.45m
L=120 - (1.28 x 28.2)
2
L=120 - 36.09
2
L=83.91
2
Length= 41.95m
Calculating with the wrong velocity
If Time Delay = 28.2, Distances 150m & Velocity change from 1.28, 1, 0.4
L=150 - (1.28 x 28.2)
2
L=150 - 36.09
2
L=113.91
2
Length= 56.95 m
L=150 - (1 x 28.2)
2
L=150 - 28.2
2
L= 121.8
2
Length= 60.90 m
L=150 - (0.4 x 28.2)
2
L=150 - 11.28
2
L=138.72
2
Length= 69.36 m
Calculating with Time Delays
Advantages of having the leak in the central position between sensors when unsure of the velocity
of the pipe.
IF Time Delay = 1.4, Distances 150m & Velocity change from 1.28, 1, 0.4
L=150 - (1.28 x 1.4)
L=150 - 1.792
L=148.21
Length= 74.10 m
2
2
2
L=150 - (1 x 1.4)
L=150 - 1.4
L=148.60
Length= 74.30 m
2
2
2
L=150 - (0.4 x 1.4)
L=150 - 0.56
L=149.44
Length= 74.72 m
2
2
2
The leak position in these examples is closer to one sensor than the other, therefore a larger Td
IF Time Delay = 31.3, Distances 150m & Velocity change from 1.28, 1, 0.4
L=150 - (1.28 x 31.3)
2
L=150 - (1 x 31.3)
2
L=150 - (0.4 x 31.3)
2
L=150 - 40.06
2
L=150 - 31.3
2
L=150 - 12.52
2
L=109.94
2
L=118.70
2
L=137.48
2
Length= 109.90 m
Length= 59.35 m
Length= 68.74 m
Leak Noise Correlators - The Early Days
Correlators have been around for
over 35 years
The first ones were very big, heavy
and complicated, often filling the
entire storage space in a leakage
inspectors van
The Evolution of Correlators
Early correlators..
..to Palm PDA multi-point digital LNCs
Progression
Technology began to improve, meaning smaller, quicker,
lighter, more portable and more accurate Leak Noise
Correlators (LNCs)
First came the Aquascan-500 & the early MicroCorr range
Then came newer, smaller
correlators such as the
Aquascan-600 & MicroCorr-6
More modern, waterproof
keyboard input.
Hydrophones became available for
non-metallic pipeline applications.
Small and easily portable
Gutermann Aquascan-600
Aquascan-600 Portable LNC
 Peak suppression to eliminate disturbing noise sources
 Frequency step analysis
 Transmitter battery life 15 hrs
Processor battery life
of 6 hrs
User replaceable
alkaline battery cells
 Single, portable robust
..IP66 enclosure
 Multiple materials
.. in one pipe section
Aquascan-6500 PC LNC
First PC correlator using user
..friendly Windows software
 Easy print-out of detailed site ..
zzreports and leak positions
 Colour display
 Multiple correlation modes
 Full coherence analysis
 Post correlation
 Supplied with lap-top PC
Aquascan-700
 Simultaneous multi-correlation
 Colour touch-screen operation
 On screen reporting and ‘sketching’
of site and leak position & report
 Hi-fi sound quality
 (FFT - Fast Fourier Transforms)
 Frequency Spectrum Analysis (FSA)
 Improved data processing speed
 Improved filters
New cordless ‘Streetworks Act’ NEW
Friendly Sensors
Replace all this
With this
610 ‘cordless’ transmitter
Competitors ‘traditional’ style transmitter with
separate accelerometer sensor
Traditional vs Cordless Sensors
NEW
Antenna
Antenna
Carry handle
Handle
Accelerometer
Transmitter
Headphones
Connector
Charger
Connector
Magnet
Cable
Integrated charger &
hydrophone connector
610 ‘cordless’ transmitter
Integrated Transmitter,
accelerometer &
magnetic base
Using Accelerometers
Accelerometers detect the sound propagation through the pipe wall
and are non-intrusive into the network.
More difficult applications:1.
Plastic pipes over 50m on plastic (MDPE is worse than PVC).
2.
Weaker performance at low frequencies (Below 75Hz).
3.
Long lengths of pipe e.g. over 600m (iron pipe).
4.
Large diameter pipes e.g. trunk mains (above 400mm dia).
Using Hydrophones
Hydrophones detect pressure waves travelling through the
liquid and are INTRUSIVE into the pipeline.
Potential difficulties/problems:1. Ease of access to water.
2. Damage on hydrant or general water leakage around the
hydrant structure.
3. Hydrophones tend to work better at lower frequencies and
over longer distances.
Correlator Equipment
Combined Radio Transmitter(s) and
Active Sensors (accelerometers)
Portable Central LNC Processor
(can also be a lap-top or ‘toughbook’ PC)
Headphones or earpiece (not shown)
Integrated battery charger (not shown)
First line: Pipe parameters
and quality of correlation
Screen contents from top to bottom
Second line: Battery power
and strength of the radio signal
Note: If the device is being charged,
a flash symbol is displayed next to
the battery symbol
Correlation graph
Position of leak
(maximum of correlation function)
Position of cursor
Spectrum (FFT) of signal A – Coherence spectrum – Spectrum (FFT) of signal B
Signal strength and filter settings
Press
key to enter pipe parameters:
Select material and diameter and enter length of pipe.
Change between the input fields with
.
Select manual to enter sound velocity instead
of material and diameter.
If pipe consists of different materials, select ‘Multiple’
Enter a section: Select it with
Discard changes with
/
and press
.
. Set the new parameters with
.
Listening
Connect the Bluetooth headset to the AQ610. The connection
can be made from the headset or from the AQ610.
Press
to enter the ‘headset’ menu.
Change channel with
/
.
Main Menu
Enter the main menu by pressing
Select item by using
/
.
.
Loading Measurements (memory)
A list with stored measurements appears with the newest at
the top. Select measurement and press
.
Scroll through the list using
/
.
Saving Measurements (to memory)
When saving a measurement to the internal memory, optional
text can be entered to identify the measurement.
Time and date of measurements is saved automatically.
Settings
Within the ‘Settings’ screen, various functions can be
changed, or switched on or off.
Scroll through the list using
/
.
Filters
Select
to bring up the filter menu.
Within the filter menu, filters can be adjusted using ‘A.S.A.’,
manually, and the ‘notch filter’ can be switched on or off.
Manual Filter Selection
Set filters manually with the cursor in the coherence spectrum graph.
Select lower limited and press
Select upper filter limit and press
.
.
The correlation and the result will then be updated.
Using the Notch Filter
Switch Notch Filter on or off. When selecting on the Notch
Filter frequency can be entered.
Notch Filter is used for suppressing disturbing signals in
a small frequency range e.g. nearby A/C currents
at 50/60 Hz.
Ensuring correct distance measuring
First Measurement = 110 m
Second Measurement = 190 m
Error Would Have Been = 80 m
60 m
40 m
40 m
A
B
110 m
Ensure correct distance measuring
B
A
Make sure that both transmitters are on the same pipe.
If they not, this would result in a
CENTRAL CORRELATION!
An ‘Out of Bracket’ result
Move ‘B’ (Yellow) to next fitting and correlate
A
B
Field Test Work
Example of a ‘typical’ site layout
Interpreting results
Shape of peak
Cursor
manually
adjusted
This represents the area in the ground to investigate further
Generally:Broad peaks = poor accuracy
Sharp peaks = greater accuracy
Interpreting results
Position of peak
Correlation screen
Large errors
Velocity is very important!
Small velocity errors will lead to large leak position errors.
Never dig a hole based on a correlation peak close to one end,
unless you have a very accurate measurement of velocity or
other evidence indicates a leak at that point.
Interpreting results
Correlation screen
Position of peak
Ideal position is the centre of the screen but beware of centre correlation.
Velocity has little effect.
Note:- Not Applicable on mixed materials.
In practice about +/- 10% from the centre.
Mixed Material Function
40m 125 MDPE
55m 100mm DI
30m 125MDPE
This function is used where a stretch of main to be correlated contains 2 or more
different materials or pipe diameters, thus changing the velocity of the pipe to be
correlated.
Up to 9 different materials / sizes can be entered in a single correlation.
Possible Sources of Error: Poor measurement
 Incorrect pipe material entered
 Incorrect pipe diameter entered
 Parallel mains (correlating on different pipes)
 Mixed materials
 T-connections
 Poor sensor contact (reduces signal intensity)
Overcoming Errors
 Poor Measurement - Manual Error
 Wrong Material - Velocity Check
 Wrong Pipe Diameter - Velocity Check
 Parallel Mains - Center Correlation
 Mixed Materials - Velocity Check
 Tee Connections - Mains Records
 Poor Sensor Contact - Manual Error
Performing a Velocity Check
Options:
 Out of Bracket Velocity Measurement
 In Bracket Velocity Measurement
Why do a Velocity Check ?
Ideal pipework
Assumed velocity for each section will
be accurate. Overall result good
Problem pipework
Encrusted or lined pipe
Assumed velocity for iron section may be inaccurate.
Velocity of iron section may be difficult to measure.
Overall result may be poor.
Velocity Formula
V = D - 2L m/ms
Td
L = Leak position (m)
V = Velocity of sound along pipe (m/ms)
D = Length of pipe (m)
Td = time delay (ms)
Velocity Check – “Out of Bracket”
A
B
Created leak noise
Need to create an “Out of Bracket” noise source.
A service draw off is best, but a hydrant can also be used.
Velocity Check – “In Bracket”
Created leak noise
A
B
Need to create an “In Bracket” noise source.
A service draw off is best, but a hydrant can also be used.
Noise source should be near to one sensor
for time delay (TD) calculations
Possible Transmitter/Sensor Problems
Symptoms
1.
2.
3.
4.
5.
Broken or damaged lead
(does not apply to ‘cordless’ sensors)
Fails ‘tickle test’.
No reading on transmitter bar indicator.
Centre correlation.
‘White noise’ in headphones/earpiece.
Radio Problems?
1. Poor reception
Causes
metal work, bushes, shrubs, trees, hills and valleys
Symptoms
1.
Correlator suggest radio signal ‘lost’
2.
Sounds heard at correlator different to
those heard at fitting.
3.
Poor correlation.
4.
Centre correlation.
Solutions
1.
2.
3.
4.
5.
Check Transmitter is on.
Check battery status of Transmitter
Move correlator closer to Transmitter.
Reposition (self) into ‘line of sight’
Use extended antennas.
Radio Problems?
2. Centre Correlation
A ‘fault’ condition, in which a correlation is displayed exactly
mid-way on the correlator’s main screen
Causes
1.
2.
One radio not working
eg. Switched off, low battery, stolen transmitter
Correlator too close to a transmitter.
Syptoms
1.
Different sounds heard at LNC (to fitting)
Solutions
1.
Check Transmitter and re-position LNC.
Any Questions ?
Objectives in Using Filters
a.
To improve shape of peak
b.
To “unmask” hidden sources of noise
Lower frequencies occur on PLASTIC pipes
Higher frequencies occur on IRON (metallic) pipes
Contact ‘Sounding’ on exposed
pipes, fittings or valves
Always perform surface above
ground (prior to excavation)
Leak Noise Transfer to the Surface

Depending on the backfill the
noise transferral is different
Noise is transferred to the surface

The pressure within the pipe
will affect the quantity of water
being lost and the noise
generated by the leak

The size of leak will affect the
transfer of noise
High pressure
inside pipe
Leak
Zonescan-800
Correlating radio loggers
‘Lift & Shift’ preferable
 Faster sweeping of DMAs and/or Zones
 Removal of need for acoustic ‘experience’ at
point of logger deployment and/or collection
 Automatic integration of daily data (including
plotted leak positions for verification) into
STW GIS (or Google Earth).
 Effectively offers an automated ‘job-sheet’ for
repair teams.
The 3 button layout resembles
a normal working day cycle
Collecting the deployed loggers.
Synchronization of the loggers
(transferring measurement data and
preparing next recording).
Deploying the prepared loggers.
“Send” – send an
email that has
been generated
© Gutermann 2006
Actual Leak Position
19m from logger #18
06/354 Linden Rd. DMA - Worcester
Zonescan-ALPHA
 Simple upgrade of existing loggers (at any
stage in the future) without alteration to
existing investment.
 “Babysitting” more critical DMA’s
 Wireless, permanent monitoring of ZS800
 Web Browser for easy remote access
 www.alpha.gutermann.eu/STW/today.php
Zonescan-ALPHA
Style of ALPHA module selected by Severn Trent Water
© Gutermann Ltd 2007
Zonescan-ALPHA
Installation Team
Zonescan-ALPHA Installation
Zonescan-ALPHA Installed
alpha.gutermann.eu/stw/today.php