U.S. patent application number 14/189440 was filed with the patent office on 2014-06-26 for system method and device for leak detection and localization in a pipe network.
This patent application is currently assigned to Aquarius Spectrum Ltd.. The applicant listed for this patent is Aquarius Spectrum Ltd.. Invention is credited to David Salomon.
Application Number | 20140174186 14/189440 |
Document ID | / |
Family ID | 43558225 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140174186 |
Kind Code |
A1 |
Salomon; David |
June 26, 2014 |
SYSTEM METHOD AND DEVICE FOR LEAK DETECTION AND LOCALIZATION IN A
PIPE NETWORK
Abstract
The invention provides a system for leak detection of a fluid in
a pipe network. The system includes flow meters, and vibration
detectors adapted to be attached to a pipe at a location in the
pipe network. A processor analyzes signals generated by the flow
meters and vibration detectors to identify the presence of one or
more leaks in the pipe network. The invention also provides a
method for detecting and localizing leaks in a pipeline network,
and a device comprising a flow meter integral with a vibration
detector for use in the system of the invention.
Inventors: |
Salomon; David; (Netanya,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aquarius Spectrum Ltd. |
Netanya |
|
IL |
|
|
Assignee: |
Aquarius Spectrum Ltd.
Netanya
IL
|
Family ID: |
43558225 |
Appl. No.: |
14/189440 |
Filed: |
February 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12830920 |
Jul 6, 2010 |
8665101 |
|
|
14189440 |
|
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|
61281199 |
Nov 16, 2009 |
|
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61293721 |
Jan 11, 2010 |
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Current U.S.
Class: |
73/587 |
Current CPC
Class: |
G01M 3/24 20130101; G01N
29/14 20130101; G01M 3/243 20130101; G01M 3/2807 20130101 |
Class at
Publication: |
73/587 |
International
Class: |
G01N 29/14 20060101
G01N029/14; G01M 3/24 20060101 G01M003/24 |
Claims
1. An integrated flow and vibration device comprising: a wet
chamber comprising a flow meter configured to generate a flow
signal; a dry chamber comprising a vibration sensor configured to
generate a vibration signal from vibrations generated by a leak; an
interface between the wet chamber and the dry chamber comprising an
acoustically coupling material configured to conduct vibrations
from the wet chamber to the vibration sensor of the dry chamber;
and a processor configured to receive and process the flow signal
and the vibration signal.
2. The device of claim 1, further comprising an antenna, wherein
the processor is further configured to transmit using the antenna a
processed signal based on processing the flow signal and the
vibration signal.
3. The device of claim 1, wherein the vibration sensor of the dry
chamber is provided at a bottom of the dry chamber in contact with
the acoustically coupling material.
4. The device of claim 1, wherein the interface is in the shape of
a disk.
5. The device of claim 1, wherein the interface is in the shape of
a cone.
6. The device of claim 5, wherein the cone has a base end directed
towards the dry chamber and a pointed end directed towards the wet
chamber.
7. The device of claim 1, wherein the flow meter comprises a vane
that rotates when driven by fluid flowing through the wet
chamber.
8. The device of claim 7, wherein the rotation of the vane causes a
rotation of a first magnet in the wet chamber.
9. The device of claim 8, wherein the rotation of the first magnet
in the wet chamber causes a rotation of a second magnet in the dry
chamber.
10. The device of claim 9, wherein the rotation of the second
magnet in the dry chamber causes generation of the flow signal.
11. The device of claim 10, wherein the flow signal is generated
using a wire coil in the dry chamber.
12. The device of claim 1, wherein the acoustically coupling
material is silicone rubber.
13. The device of claim 1, wherein the vibration sensor comprises a
piezo membrane.
14. The device of claim 13, wherein the piezo membrane comprises at
least one of: PVDF film and a piezo ceramic material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. application Ser.
No. 12/830,920, filed Jul. 6, 2010, which claims the benefit of
U.S. Provisional Application No. 61/281,199, filed Nov. 16, 2009,
and U.S. Provisional Application No. 61/293,721, filed Nov. 11,
2010, the contents of which are hereby incorporated by reference in
their entireties into the present disclosure.
FIELD OF THE INVENTION
[0002] This invention relates to systems, methods and devices for
leak detection.
BACKGROUND OF THE INVENTION
[0003] Electronic automatic meter reading (AMR) devices are used
for flow metering in a pipeline. These devices typically use an
electronic unit attached to a conventional magneto-mechanical or
electronic flow meter, for example as disclosed in U.S. Pat. Nos.
4,940,976 and 6,611,769. Magneto-mechanical flow meters typically
measure integrative water consumption by means of a mechanical
gear. The accumulated liquid consumption is read by opto-electronic
circuits, or by piezo-electric pick up of the gear rotation, which
are usually packed in a dry section-register. In electronic meters,
a magnetic sensor monitors the liquid meter rotor revolutions and
generates an electrical signal indicative of the water flow. The
sensor may be based, for example, on an inductive coil, a Hall
effect sensor, or a magnetoresistive device. Some devices use
optical pick-up systems to read the revolution of the magnetically
driven revolutions of the rotor. The consumption and/or rate data
is measured at various times and the data is transmitted to a
central server typically via an RF link. AMR systems can also
perform mass balance calculations by registering input and output
flow at different locations in a pipe network. However, the AMR
systems cannot detect leaks in pipes that are below their
measurement threshold. AMR systems also cannot detect leaks that
are less than 1% of the nominal flow in the distribution pipes nor
locate the leak as the mass balance is done over a relatively large
pipe network. Recently ultrasonic flow meters have been introduced
that are based on sound velocity or Doppler phase shift
measurements.
[0004] Several leak detection system and methods are known, such as
vibration data loggers and correlators that measure pipe vibrations
that are generated by the characteristic flow turbulence caused by
a leak. This leakage detection is mostly based on vibration energy
measurements and locating points where the vibration energy exceeds
a particular threshold. A leak detection system based on vibration
sensing is disclosed, for example, in U.S. Pat. No. 7,596,458.
[0005] Vibration data loggers include a vibration sensor such as a
piezo element that is attached to a pipe element. The data logger
is programmed to measure vibrations at certain times mostly at
night when the flow is minimal. The signal processing of the logger
calculates the vibrational energy at several locations of the pipe
network, stores the calculated energies in a memory, and transmits
the calculated energies to a processing station for leak detection
using correlation analysis. Correlation analysis requires
synchronization of the clocks of the sensors, and any drift in the
clocks can adversely affect the accuracy of leak location.
[0006] The accuracy of the leak detection is increased with
increasing number of sensors distributed over the pipeline network.
A high density of the sensors provides high resolution and improved
detection probability but increases the cost of the system.
Nonetheless, existing noise loggers are very sensitive to artifacts
due to noise generated by water consumption flow rather than
leakage.
SUMMARY OF THE INVENTION
[0007] In its first aspect, the present invention provides a system
for leak detection and location in a pipe network. The system of
the invention comprises two or more flow meters and a two or more
vibration detectors. Each flow meter and vibration detector is
provided with a microprocessor and a transceiver that allows each
flow meter and vibration detector to transmit data to a service
center over a communication network and, in some embodiments, also
to receive data from the service center The service center
processes data received from the flow meters and vibration
detectors and analyzes the data for the detection of a leak in the
pipe network, as explained below. When a leak is detected in the
pipeline, the service center issues an alert. The alert may display
on a map of the pipe network the location of any detected
leaks.
[0008] In one embodiment, each of one or more of the flow meters is
integrated with a vibration detector in an integrated unit.
[0009] In a second aspect, the invention provides a method for
processing signals generated by the flow meters and vibration
detects for detection and location of leaks in the pipe network. In
accordance with this aspect of the invention, the processing uses
flow data obtained from the flow meters to reduce vibration
measurement artifacts. In one embodiment, vibration detection is
performed essentially simultaneously with flow metering. As
explained below, this allows vibrations due to an inappropriate
leak to be distinguished from vibrations due to the flow of fluid
that occurs during normal consumption.
[0010] In another of its aspects, the invention provides an
integrated device comprising a flow meter and a vibration detector
that may be used in the system of the invention. The integrated
device comprises a wet chamber through which a fluid flows and is
metered, and a dry chamber containing a vibration detector.
[0011] Thus, in one of its aspects, the invention provides a system
for leak detection of a fluid in a pipe network comprising: [0012]
(a) two or more flow meters adapted to be installed on a pipe at a
location in the pipe network, each flow meter generating a signal
indicative of a flow rate of the signal at the location of the flow
meter; [0013] (b) two or more vibration detectors adapted to be
attached to a pipe at a location in the pipe network, each
vibration detector generating a signal indicative of vibrations in
the pipe at the location of the vibration sensor; and [0014] (c) a
processor configured to analyze the signals generated by one or
more of the flow meters and one or more of the vibration detectors
to identify the presence of one or more leaks in the pipe
network.
[0015] The flow meters and vibrations detectors may communicate
with the processor over a communication network, and each flow
meter and each vibration detector may comprise a transceiver for
communicating with the processor over the communication network.
The processor may be further configured to generate an alert when a
leak is detected. The system may comprise a display device, and
generating an alert may comprises indicating a location of a leak
in the pipeline network on a map of the network displayed on a
display device. At least one flow meter may be integral with a
vibration detector. The vibration detectors may be of a type
selected from an accelerometer, a strain-gage or hydrophone.
[0016] In another of its aspects, the invention provides a method
for detecting and localizing leaks in a pipeline network
comprising: [0017] (a) monitoring vibration signals generated by
vibration detectors deployed at two or more locations in the
network; [0018] (b) determining whether there are any significant
flow rates in the pipeline; [0019] (c) if no significant flows are
detected in the pipeline, executing a leak detection algorithm on
the vibration signals to locate leaks in the pipeline; and [0020]
(d) issuing an alert when a leak has been located in the
pipeline.
[0021] The method of the invention may comprise steps of: [0022]
(a) monitoring vibration signals generated by vibration detectors
deployed at two or more locations in the network; [0023] (b)
analyzing the vibration signals to determine whether any of the
vibration signals are indicative of exceptional vibrations in the
network; [0024] (c) when exceptional vibration signals are
detected, monitoring signals generated by vibration detectors
deployed at two or more locations in the network and flow meters
deployed at two or more locations in the network; [0025] (d)
determining whether there are any significant flow rates in the
pipeline; [0026] (e) if no significant flows are detected in the
pipeline, executing a leak detection algorithm on the vibration
signals to locate leaks in the pipeline; and [0027] (f) issuing an
alert when a leak has been located in the pipeline.
[0028] In the method of the invention, an exceptional vibration may
be a vibration whose amplitude or power exceeds a predetermined
threshold, or a vibration whose amplitude or power has increased
over a recent time period by a predetermined factor. The vibration
signals may be monitored periodically. A trigger for monitoring the
flow signals and the vibration signals may originate from a central
server, from an external clock, or from a roaming vehicle. The leak
detection and location algorithm may be based on the arrival times
of vibrations at the vibration detectors, the pipe network
configuration, and the speed of propagation of the vibrations. The
leak detection and location algorithm may comprise calculation of a
cross-spectrum or correlation of pairs of signals and identifying
an optimal filter corresponding to maxima of coherence of the two
signals.
[0029] In another of its aspects, the invention provides a device
comprising a flow meter integral with a vibration detector. The
flow meter may contained in a wet chamber, and the vibration
detector may be coupled to the wet chamber. The vibration detector
may comprise a piezo membrane placed at the bottom of the dry
chamber. The device of the invention may further comprise a
transceiver configured to transmit signals to a remote processor.
The transceiver may also be configured to receive signals from the
remote processor. The wet chamber may be separated from the dry
chamber by a surface having the shape of a truncated cone and
wherein a space between the wet chamber and the dry chamber
contains an acoustically coupling material. The vibration detector
may comprise a piezo membrane having an annular shape. The device
may comprises an ultrasound transducer having a first mode in which
the ultrasound transducer serves as the flow meter and a second
mode of operation in which the ultrasound transducer servers as the
vibration detector. The ultrasound transducer in the first mode of
operation may measure transmitted ultrasound waves for phase shift
or frequency shift. The ultrasound transducer in the second mode of
operation may measure low frequencies related to acoustic waves
generated in a water network. The device may be configured to
detect malfunctions in the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to understand the invention and to see how it may
be carried out in practice, embodiments will now be described, by
way of non-limiting example only, with reference to the
accompanying drawings, in which:
[0031] FIG. 1a shows a system for leak detection and location in a
pipeline network in accordance with one embodiment of the invention
having separate flow meters and vibration detectors, and FIG. 1b
shows a system for leak detection and location in a pipeline
network in accordance with a second embodiment of the invention
having integrated flow meters and vibration detector;
[0032] FIG. 2 shows the system of FIG. 1b deployed on a pipeline
network;
[0033] FIG. 3a shows a flow chart for a method of leak detection
and location in accordance with one embodiment of the invention,
and; FIG. 3b shows a flow chart for a method of leak detection and
location in accordance with a second embodiment of the
invention
[0034] FIG. 4 shows an integrated flow meter and vibration detector
in accordance with one embodiment of the invention;
[0035] FIG. 5 shows an integrated flow meter and vibration detector
in accordance with another embodiment of the invention;
[0036] FIG. 6a shows a vibration signal detected by an independent
vibration detector mounted on a metal pipe, FIG. 6b shows a
vibration signal measured simultaneously on the same metal pipe by
a vibration detector in an integral device comprising the vibration
detector and a flow meter; and FIG. 6c shows the Fourier transform
of the signals of FIGS. 6a and 6b; and
[0037] FIG. 7a shows a vibration signal detected by an independent
vibration detector mounted on a metal pipe, FIG. 7b shows a
vibration signal measured simultaneously on the same metal pipe by
a vibration detector in an integral device comprising the vibration
detector and a flow meter; and FIG. 7c shows the Fourier transform
of the signals of FIGS. 7a and 7b.
DETAILED DESCRIPTION OF EMBODIMENTS
[0038] FIG. 1a shows a system 2 for leak detection in a pipe
network, in accordance with one embodiment of this aspect of the
invention. The system 2 comprises two or more flow meters 4 and a
plurality of vibration detectors 6. Three flow meters 4a, 4b, and
4c, and three vibration detectors 6a, 6b, and 6c, are shown in FIG.
1. This is by way of example only, and the system of the invention
may be implemented using any number of flow meters that is at least
two, and any number of vibration detectors that is at least two.
The number of flow meters may be less than, equal to or greater
than the number of vibration detectors. The flow meters may be any
flow meter known in the art. Each flow meter has a flow inlet 8 and
a flow outlet 10 that allows the flow meter to be installed on a
flow line at a location in the pipe network. The vibration meters 6
may be any type of vibration detector known in the art, such as an
accelerometer, strain-gage or hydrophone type sensor. The
hydrophone tends to be more suitable for plastic pipes providing
better performance than the accelerometer. Each vibration meter 6
is adapted to be attached to a pipe in the pipe network. The
typical vibration frequencies are in the range of 1-100 Hz for
plastic pipes and 500-2000 Hz for metal pipes.
[0039] Each flow meter 4 is provided with microprocessor 13 and a
transceiver 12 that allows each flow meter to transmit data to a
server 16 over a communication network indicated by the cloud 14
and further allows the flow meter to receive data from the server
16. Similarly, each vibration detector 6 is provided with a
microprocessor 5 and a transceiver 17 that allows the vibration
detector to communicate with the server 16 over the communication
network 14.
[0040] The vibration detector may be attached to a pipe in the pipe
network adjacent to a flow meter.
[0041] The system 2 further includes a service center 18 that that
communicates over the communication network 14 with the server 16,
and through the server 16, with the flow meters 4 and the vibration
detectors 6. The service center 18 includes a processor 20 that
processes data received from the flow meters and vibration
detectors and analyzes the data for the detection of a leak in the
pipe network, as explained below. Data received at the service
center, as well as the results of any processing or analysis of the
data may be stored in a memory 22. When a leak is detected in the
pipeline, the processor 20 issues an alert. The alert may be
displayed on a display device, such as a CRT screen 24. The alert
may include the location in the pipe network of any detected
leaks.
[0042] FIG. 1b shows a system 2' for leak detection in a pipe
network, in accordance with another embodiment of this aspect of
the invention. The system 2' has several elements in common with
the system 2 of FIG. 1a, and similar components are indicated by
the same reference numeral in FIGS. 1a and 1b, without further
comment. The system 2' comprises a plurality of devices 28
comprising a flow meter 30 integral with a vibration detector 32
that may be assembled in a common housing. In an alternative
design, the the flow meter 30 and the vibration detector 32 of the
device 28 are in separate housings but share a common
microprocessor 13. Three devices 28a, 2bb, and 28c, are shown in
FIG. 1b. This is by way of example only, and the system 2' may
include any number of integrated units 28 that is at least two.
Each device 28 also includes a transceiver 34 that communicates
with the server 16 over the communication network 14. In this
embodiment, the flow meter 30 measures the flow at the same
location in the pipe network where the associated vibration
detector detects vibrations.
[0043] In one embodiment, the communication network 14 is a
wireless network, for example, using any known RF protocol, such as
Hubs or Cellular, Ethernet or TCP-IP. The communication can be one
way from each vibration detector 6, flow meter 10 or integrated
device 10 to the server 16. Alternatively, the communication
between each vibration detector 6, flow meter 10 or integrated
device 10 to the server 16 is two-way. For example, the server 16
may transmit data to the sensors in order synchronize the clocks of
the vibration detectors or flow meters, or may send commands or set
parameter values of the meters and detectors.
[0044] The vibration detector 6 or 32 when attached to a pipe in
the pipe network, detects pipe vibrations or acoustic waves in the
fluid generated by a leak and arriving through the network to the
detector. The vibration sensor signal is amplified, converted to a
digital signal, for example, at a sampling rate of 5 kHz and a
dynamic range of 12 bit. Typical vibrations at frequencies above
500 hz in metal water pipes range from between 10.sup.-4-10.sup.-3
m/sec.sup.2 in the absence of a leak to about 10.sup.-3-10.sup.-2
m/sec.sup.2 in the presence of a leak. The typical frequencies
generated by small leaks are about 1-8 kHz, but the high
frequencies undergo larger attenuation than low frequencies thus a
sampling rate of 5 kHz with a low pass filter of 2 kHz can provide
an adequate signal for leak detection. For plastic water pipes the
frequencies are lower, in the range of 10-200 Hz, and the
vibrations have a lower amplitude. Therefore for a plastic pipe,
the sampling rate should be around 600 samples per second and a low
pass filter. When some of the pipes are made of plastics such as
PVC or PU, the server can configure the sensor modules to measure
vibration at a higher sensitivity and in a lower frequency
band.
[0045] The microprocessor associated with the flow meters and
vibration detectors may be, for example, a CC430 microprocessor
from Texas Instruments having integrated ADC and RF circuits. The
microprocessor may have an internal clock in which case the
microprocessor may be configured to activate the flow meters and
vibration detectors at predetermined times. The signals of the
vibration detectors and the flow meters are input to the
microprocessor. In the case of the integrated device 28, the
vibration detector signal and the flow meter signal may be input
into the processor 33 via separate digital channels or via
multiplexer (not shown). The microprocessor digitizes the signals.
The microprocessor may transmit the raw data signals to the service
center for processing. The microprocessor may preprocess the
signals, and transmit the results of the preprocessing to the
service center. The preprocessing may include filtering noise from
the signal. The processing may include calculating a flow rate from
the signals generated by the flow meters. The processing may
include calculating a Fourier transform of the signals generated by
the vibration detectors and performing a peak search or power
estimation in the Fourier transform. Processing of the vibration
signals may use AR or LPC modeling of the signal spectra that is
phase preserving. Signal modeling in a particular frequency band
can be effective since pipes have characteristic frequency bands in
which they transmit vibrations effectively. The frequency band can
be predetermined when the system is calibrated or by raw signal
analysis at the server by coherence analyses. In another
embodiment, the vibration power or amplitude in pipes due to the
leak is determined is by the microprocessor and the determined
power or amplitude is transmitted to the server. The power
estimation is done by filtering the vibration signal using analog
circuits or a microprocessor and calculating the average power of
the signal in a predetermined time window, typically of about 0.5
sec. The estimated power is a number that can be easily stored and
transmitted to the server with low battery power consumption.
[0046] The data may be transmitted from the device to the service
center 18 on the fly, or alternatively, the microprocessor may
store data in a memory (not shown), and transmit the data to the
service center 18 at predetermined times. Each flow meter 4 and
each vibration detector 6 in the system 2, or each integrated
device 28 in the system 2' has an ID number that is transmitted to
the service center with the data.
[0047] FIG. 2 shows the system 2'of FIG. 1b deployed on a pipe
network. An underground pipe 40 that is part of the pipe network
conducts a fluid such as water or gas from a source (not shown in
FIG. 2) to each of a plurality of buildings 42. Each of the
buildings 42 is provided with an individual feeder line 44 that
conducts the fluid from the underground pipe 40 to the building. On
each feeder line 44 a device 28 is deployed. The feeder line 44 is
connected to the input port 10 of the flow meter 30 of the device
28. Fluid exits the device 28 at the output port 8 of the flow
meter 30 of the device 30 at the in port 10 of the device 28 and
then enters the building. Each deployed device 28 measures flow of
the fluid through the device 28, and also detects vibrations in the
feeder pipe 44 to which the device 28 is attached. Data collected
by each device 28 are transmitted to the service center 18, as
explained above.
[0048] Activation of the flow meters and vibration detectors and
transmission of data between the devices and the service at
predetermined times allows a significant reduction in the power
requirements of the system. The system can be maintained be in a
stand-by (sleep) mode and woken up on schedule to perform tasks and
then returned to the sleep mode until the next scheduled
activation. When a leak occurs in the pipe network, vibrations are
generated in the fluid emanating from the leak location. Vibration
detection is typically performed only a few times a day or week,
preferably at night when the flow is minimal. In one embodiment,
vibration detection is performed when the flow rate is minimal. The
vibration recording can be 0.5-1 second for estimation of vibration
power, while a longer recording time in the order of 2-10 seconds
might be preferred for correlating the signals for leak
location.
[0049] The service center 18 receives the signals from all of the
flow meters and vibration detectors in the system. The processor 20
of the service center executes an artifact detection and rejection
algorithm based on flow estimation in proximity to the locations
where vibrations were detected. The vibration power detected by
each vibration detector in the system, or the power in a
predetermined frequency band, may be indicated on a map of the pipe
network and displayed on the display. The frequency band may be
selected according to the material of the pipes in the pipeline.
The vibration power may be indicated as color code to draw a user's
attention to vibration detectors reporting unusually high. Trends
in the vibration power and the flow rates can also be displayed. If
the value at a particular sensor exceeds the threshold or
significantly increases relative to a previous value recorded by
the detector, this could be indicated on the display. Trends in the
vibration power and the flow rates at specific places with
increased vibration power can be presented to the operator.
[0050] In addition, the processor 20 of the service center
processes the received signals for the detection and location of
leaks in the pipe network. In accordance with the invention, the
processing uses flow data obtained from the flow meters to reduce
vibration measurement artifacts. This allows vibrations due to an
inappropriate leak to be distinguished from vibrations due to the
flow of fluid that occurs during normal consumption.
[0051] FIG. 3a shows a flow chart for a process 51 for detecting
and localizing leaks in a pipeline network in accordance with one
embodiment of the invention. In step 53 simultaneous recording of
flow signals and vibration signals is carried out. The trigger for
recording the signals may originate from the server which activates
the flow meters and vibration detectors at predetermined times,
under predetermined circumstances. Alternatively, a vibration
detector detecting an exceptional vibration may issue a trigger for
simultaneous recording of the flow signals and the vibrations
signals. As yet another alternative, the flow meters and vibration
detectors may receive a signal from a common clock, such as from a
geopositioning system (GPS) or a cellular network, and simultaneous
recording of the flow signals and the vibration signals occurs at
predetermined times. In another embodiment, a roaming vehicle
generates a series of synchronization signals and collects the
recorded signals and transmits the signals to the server. In step
55, it is determined whether there are any significant flow rates
that may introduce an artifact into the leak detection. A
significant flow rate may be, for example, consumption by a user
above certain value that can introduce significant vibration into
the network similar to the vibration caused by a leak. If yes, the
process returns to step 53 with the recording of the flow and
vibration signals. If no, the process proceeds to step 57 where a
leak detection and location algorithm is executed on the recorded
signals. If a leak is detected and located, then in step 59 an
alert is issued and the process returns to step 53.
[0052] FIG. 3b shows a flow chart for a process 50 for detecting
and localizing leaks in a pipeline network in accordance with
another embodiment of this aspect of the invention. The process 50
begins with the monitoring of vibration signals generated by
vibration detectors deployed at various locations in the network.
Monitoring of the vibration signals may be periodic, for example,
at one or more predetermined times over a 24 hour period. In step
54, when vibrations signals have been obtained, the signals are
analyzed to determine whether any of the vibration signals
indicated exceptional vibrations in the network. An exceptional
vibration may be, for example, a vibration whose amplitude or power
exceeds a predetermined threshold, or a vibration whose amplitude
or power has increased over a recent time period by a predetermined
factor. If no exception vibration signals are detected, the process
returns to step 52 and the monitoring of the vibration signals
continues. If in step 54 it is determined that exceptional
vibration signals have been detected, then the process continues
with 56 where vibration signals from at least some of the vibration
detectors and some of the flow rate signals from the flow detectors
are monitored synchronously. The inaccuracy of the timing of the
synchronous recording of the vibration is preferable be less than 1
ms, as a delay of every 1 ms in the timing of the readings can
introduce an error in the leak location of about 1.2 meters. The
process then continues with step 58 where it is determined whether
there are any significant flow rates in the pipeline. The flow rate
estimation is based on the reading of the water flow meters in the
area where the vibration is detected. If yes, then there is a great
chance for a false positive (a flow due to consumption being
interpreted as a leak) so that reliable leak detection or location
is not possible, and the process returns to step 52 with the
continuation of the monitoring and recording of the vibration
signals. If at step 58 it is determined that there is no
significant flow in the pipeline, the process continues to step 60
where a leak detection and location algorithm is executed which
analyzes the vibration signals in order to locate leaks in the
pipeline. After leak detection and location, an alert is issued
(step 62). The alert may an audible or visual signal. The alert may
involve indicating the location of the leak on a map of the
pipeline displayed on the display 24, whereupon the process returns
to step 52 and the monitoring of the vibration signals
continues.
[0053] The leak detection and location algorithm executed in step
60 of the process 50 is based on the arrival times of vibrations at
the various vibration detectors, together with the pipe network
configuration, and the speed of propagation of the vibrations.
Vibrations arrive at each vibration detector with a time lag
proportional to the distance of the detector from the leak (the
origin of the vibrations). The velocity of vibrations in pipes is
around 1250 m/s. A precision of around 2 meters in the location of
the leak is usually satisfactory.
[0054] The leak detection and location algorithm may involve, for
example, calculation of the cross-spectrum (coherence) of pairs of
signals and identifying the optimal filter that corresponds to the
maxima of the coherence of the two signals. Alternatively, pairs of
signals may be filtered in a maximal coherence spectral band, and
calculating the cross correlation of the filtered signals. Another
method uses finding the correlation maxima. When the correlation
exceeds a predetermined threshold, the leak position can be
determined from the time of the correlation or cross-cepstrum
maxima times the sound velocity in the pipes.
[0055] In another embodiment, the leakage detection and location is
based on flow metering and vibration power in a particular
frequency band that is measured by each vibration sensor, either
synchronously or not synchronously. The advantage of this method is
the ability to transmit a small data volume over one way
communication link. The power estimation is done at certain times
at night, by recording and filtering the vibration signal using
analog circuits or microprocessor and calculating the average power
of the signal in a predetermined time window, typically of about
0.5 sec. The measured vibration power and the flow value is sent to
the server over the communication network with a sensor identifier
(ID) and time stamp. Each sensor is associated with the
geographical position according to its installation. The first step
is artifact rejection using flow meter data. For each vibration
measurement the flow rate in the radius of 100-200 meters is
estimated based on the flow meter data. If the flow is larger than
a defined threshold the vibration data for the specific measurement
is labeled as unreliable. The flow threshold is calculated for each
area based on the statistics of the night flow. Reliable vibration
measurements are added to the list of measurements that is
currently updated. The second step is calculating the average (or
5-30 quantile) vibration power of the reliable measurements for
every sensor in a time window of 1-5 days in order to reduce
measurement noise. The leak detection is performed by finding a
maximum of the averaged vibration power that is above certain
threshold. The threshold can be a predetermined value or calculated
adaptively for each area and time of the year using statistics e.g.
three times the standard deviation of the vibration power of the
sensors in an area of about 50 sensors. The maximum value and
position can be optimized using fitting of the two-dimensional
function of vibration power P(x,y), where x-y are geographical
coordinates. The fitting can be performed by a spline function.
Another method for location of the leak more precisely between the
vibration sensors is solving an inverse problem of finding a
vibration source using the data of vibration sensors at specific
points. This method uses the pipe geometry and attenuation
coefficients of the acoustic waves in the specific pipes as well as
reflection coefficients in the pipe joints.
[0056] FIG. 4 shows an integrated device 70 comprising a flow meter
and a vibration detector that may be used for the device 28 in the
system 2' shown in FIG. 1b, in accordance with one embodiment of
this aspect of the invention. The integrated device 70 comprises a
wet chamber 72 through which a fluid flows between an inlet port 74
and an outlet port 76. Flow of a fluid through the wet chamber
causes a vane 78 to rotate about an axis 80. Rotation of the axis
80 drives rotation of a magnet 82, so that rotation of the vane 78
is coupled to rotation of the magnet 82. The integrated device 70
further comprises a dry chamber 84. The dry chamber 84 is separated
from the wet chamber by a space filled with an acoustically
coupling layer 86 that conducts vibrations from the wet chamber 82
to a piezo membrane 88 placed at the bottom of the dry chamber 84.
The acoustically coupling material may be, for example, silicone
rubber. The acoustic coupling material may be compressible to allow
easy attachment of the dry chamber to the wet chamber A magnet 90
located in the dry chamber rotates about an axis 92 when driven by
the rotation of the magnet 82 in the wet chamber 72. Thus, rotation
of the vane 78 is coupled to rotation of the magnet 92. Rotation of
the magnet 90 generates a signal that can be calibrated with the
flow rate in the wet chamber 72. The signal may be an electrical
signal generated in a wire coil 94 or an optical signal (not
shown). The piezo membrane 88 generates an electric signal that can
be calibrated with vibrations in the membrane 88, and may be, for
example, a polarized PVDF film or piezo ceramic material such PZT.
An amplification and processing unit 96 receives the signals
generated by the magnet 92 and the piezo membrane 88. The
processing unit 96 includes a microprocessor and a transceiver (not
shown) and an antenna 98, as explained above with reference to the
device 28 shown in FIG. 1b.
[0057] FIG. 5 shows an integrated device 100 comprising a flow
meter and a vibration detector that may be used for the device 28
in the system 2' shown in FIG. 1b, in accordance with another
embodiment of this aspect of the invention. The integrated device
100 has several components in common with the integrated device 70
shown in FIG. 4, and similar components are indicated by the same
reference numerals without further comment. In the device 100, the
interface between the wet chamber 72 and the dry chamber 84 has the
shape of an inverted truncated cone. A space 102 in the interface
contains an acoustically coupling material 104. An opening in the
truncated conical surface of the dry chamber is covered with a
flexible membrane 108. A magnet 110 extends from the flexible
membrane 108 into the dry chamber 84. Rotation of the magnet 110 is
coupled to the rotation of the magnet 82 as explained above with
reference to the magnet 90 of the integrated device 70 shown in
FIG. 4. Rotation of the magnet 110 thus generates a signal that can
be calibrated with the flow rate of fluid in the wet chamber 72.
The magnet 110 is surrounded by a cylindrical coupler 106 that
conducts vibrations from the acoustically coupling material 104 to
a piezo membrane 112. The piezo membrane 112 generates a signal
that can be calibrated with vibrations in the membrane 112. The
membrane 112 has an annular shape and surrounds the magnet 110. In
another embodiment, the truncated conical surface of the dry
chamber is corrugated to conduct vibrations from the acoustically
coupling material to the piezo membrane instead of, or in addition
to, the the cylinder 106.
[0058] In other embodiments, flow detection utilizes an optic
sensor that measures rotor revolutions, or ultrasound sensors that
are used to measure transit time or Doppler shift that can be
calibrated with flow rate.
[0059] In some embodiments of the integrated device, flow rate
metering and vibration detection is performed using a common
ultrasound transducer. The ultrasound transducer has a flow
metering mode of operation in which the ultrasound transducer
measures transmitted ultrasound waves for phase shift or frequency
shift that is caused by liquid or gas flow and generates a signal
that can be calibrated with the flow rate. In this mode, only
transmitted frequencies are used and all the other frequencies are
filtered out. The ultrasound transducer also has a vibration
detection mode in which the ultrasound transducer measures low
frequencies and generates a signal that can be calibrated with the
vibrations.
[0060] The processor may also be configured to analyze the flow
meter signals and vibration detection signals to detect a
malfunctioning flow meter. This can be done, for example, by trend
analysis of the vibrations and flow reading, for example, by
comparing the vibration signal power in one or several frequency
bands, to the flow rates. For example, if the rotor of a flow meter
is stuck or is slowed by an external magnet, the flow becomes more
turbulent and creates more vibrations than during normal operation.
By detecting the increased vibrations of a flow meter at different
flow rates, the server can issue an alarm for malfunction of the
flow meter.
[0061] Experiments were carried out to compare vibration detection
by an integrated device of the invention comprising a flow meter
and a vibration detector with vibration detection by a vibration
detector independent of a flow meter. The integrated device of the
invention was constructed by fitting a piezo membrane to a flat
register in a bronze Badger.TM. water meter. A Wilcoxon.TM.
accelerometer 728a (sensitivity 500 mv/g) was used as the
independent vibration detector. Both the integrated device and the
independent vibration detector were mounted on a pipe. Vibrations
in the pipe were induced by opening a tap. FIG. 6a shows the
vibration detected by the independent vibration detector, and FIG.
6b shows the vibrations detected simultaneously by the integrated
device when mounted on a metal pipe. FIG. 6c shows the Fourier
transform of the signal in FIG. 6a (120) and the signal shown in
FIG. 6b (122). FIG. 7 shows results of vibration detection by the
same detectors when mounted on a plastic pipe. FIG. 7a shows the
vibration detected by the independent vibration detector, and FIG.
7b shows the vibrations detected simultaneously by the integrated
device when mounted on a metal pipe. FIG. 7c shows the Fourier
transform of the signal in FIG. 7a (124) and the signal shown in
FIG. 7b (126). The results show that the integrated device has a
greater sensitivity, particularly at low frequencies, which
includes the frequencies of interest in leak detection.
* * * * *