Iisrt siddharth prabhu (electrical)

International Journal of Electrical, Electronics and Communication Engineering (IJEEC)
Vol. 1, Issue. 1, April – 2015 ISSN (Online): 2395-6747
19
Abstract - This project is mainly aimed at
developing a detector system which provides
reliable leak detection. It performs autonomous
leak detection in pipes, when compared to the
existing manual user-experience system. Leakage
is the major reason for most of the unaccounted
losses in the pipelines that carry oil, gas, etc., in
many parts of the world (i.e.) plain lands, terrains,
deserts, hilly areas, oceans, etc., Detection is based
on the presence of pressure gradient along the
pipeline. Also, this detector senses the leaks at any
angles in the pipeline by moving along the
circumference of the pipes with the two sensors.
This detection system is reliable, low cost, and
robust.
Keywords : Drum , Leakage ,Membrane, Pipe
Guard, Radial Pressure Gradient, Suction region
I.INTRODUCTION
Generally, water obtained through the limited
resources is treated for purifcation, which is critical
for humans.So are the resources as well,which are
forming the human needs. There occurs wastage in
resources and energy by transportation of resources
to the final destination. Also, lot of oil and gas
pipelines are poorly maintained around the world.
Therefore significant amount of total oil and gas
resourse is lost [1]. It also causes threat to the humans
and damage to environment. Leakage occurs in the
pipeline due to the bad maintenance of the pipes and
also because of any destructive cause such as
corrosion of the pipelines, change in the pressure,
cracks, and defects in the pipes [2]. Thus the water
utilities and the oil and gas authorities are seriously
concerning the loss of th-e product due to leakage..
There are basically two types of methods for leak
detection
 Out-of-Pipe Methods
 In-pipe Methods
Out-of-pipe Methods:
There are various techniques for leak
detection [3][4].One of the way is estimating leak
losses from the audits. Here difference between
amount of water supplied and the total amount of
water recorded by the meter indicates the amount of
unaccounted water while this gives information about
the water leakage rate, it does not give any
information about location of leak.
Acoustic leak detection not only identifies
but also locates leaks. It consists of listening rods of
aqua phones. These devices contact with valves or
hydrants. The techniques also include geo phones to
listen for the leaks on ground directly above pipes
[4]. Drawbacks of these methods need operator
experience. As the procedure is slow, this method is
not scalable.While, there are techniques which use
two sensors that are placed on either side of the leak
from the pipelines. The time lag between the acoustic
signals detected by two sensors is used to identify
and locate the leak [5]. Even though, this method
works well for metal pipes, it is difficult for plastic
pipes and is ineffective [6],[7]. Finally, several non
acoustic methods like infrared thermography, tracer
gas technique, and ground-penetrating radar have
been used in leak detection [8],[9]. These methods
have the advantage of being insensitive to the pipe
material and operating conditions. However, a map of
the network is needed, user experience is necessary
and the method is slow.
In-Pipe Methods:
When compared to Out-Of-Pipe Method, In-
Pipe inspection is more accurate, less sensitive to
external noise, and also more robust. Various in-pipe
leak detection approaches that are reported are as
follows,
Smartball is free-swimming mobile device
consists of porous foam ball that envelopes a
watertight, aluminum sphere containing sensitive
instrumentation. Another technique named Sahara,
will pinpoint location and estimate leak. Both
Design on In-Line Reliable Leak Detector
1
G.Shanmugaraj, 2
D.Siddharth Prabhu, 3
K.Viswanath, 4
V.Vijayakumar
1
Assistant Professor, 2,3,4
UG Students, Department of ECE
1,2,3,4
Velammal Institute of Technology, Chennai, INDIA

20
Smartball and Sahara are passive and cannot move
inside complicated pipelines. But operator experience
is needed for signal interpretation and leakage
localization.
Fig.1 , Pipe health monitoring using PipeGuard.
PipeGuard travels in the network, searches for leaks,
and transmits signals wirelessly via relay stations to a
computer
In oil industry, various nondestructive
testing methods are used for pipe inspection .Most of
systems use magnetic flux -leakage based detectors
while some use ultrasound to search pipe defects
[10].Their performance depends on the pipe material
which are power demanding and have limited
capabilities of large size. In this paper, a new
technique named PipeGuard is introduced, which
detects leaks in pipes in reliable and autonomous
manner. Here, PipeGuard is inserted into network via
insertion points .The system inspects network and
sends signals wirelessly via relay stations to a
computer [11].Leak signals stand out clearly on leak
occurrence, eliminating user experience. The leak
detection is done by detector based on identifying
pressure gradient in vicinity of the leaks [12],
[13].The system is optimized to operate in gas/air.
II.DETECTION BASED ON THE PRESSURE
GRADIENT
Here, the proposed detection concept and
detector design are discussed. Detection is based on
identifying presence of localized pressure gradient
(∂p/∂r, where r stands for radial coordinate of pipe)
which appears in pressurized pipes in leakage areas
and is independent of pipe size/material .Also, the
pressure gradient exists in different media which
makes detection applicable to any material.
A)Radial Pressure Gradient:
A straight pipe is considered here for the
analysis .All results can be used also for bent
sections, Y-and T-junctions and also for other
complex pipe configurations .Also, leak is assumed
to be existing in the middle of the pipe. Due to the
positive difference in pressures (∆p = pHigh - plow), the
fluid is escaping through the leak .Here small leaks
are considered. This helps to assume that line
pressure is constant across the leakage (in the
longitudinal dimension).But the large leaks can also
be easily detected but by other means. The pressure
sensors can easily sense large drop in line pressure
that arises in large leak. The proposed detection
method is based on the fact that any leakage in
pipeline changes the pressure and flow field of the
medium .This is studied, characterized and quantified
in detail [14].The conclusion is there is only small
effect in region near the leak .But, this region exhibits
a rapid change in static pressure, dropping from pHigh ,
inside pipeline to pLow at surrounding medium
outside. This phenomenon is the radial pressure
gradient.
The key feature in the proposed leak
detection scheme is the local drop. On the occurrence
of leaks, the radial pressure gradient represents
suction region. Statistics show radial pressure
gradient close to leak is large in magnitude and drops
quickly as distance increases. Here, the radial
pressure gradient is shown in the simulation as a
function of radial distance. This detection system
based on radial pressure gradient is effective and
reliable. Directly measuring the pressure at each
point to calculate the gradient is avoided as it is not
efficient. However, as leak happen at any angle ᶲ
around the circumference, full observance require
series of pressure sensors around the perimeter
pipe.Hence more efficient mechanism is introduced
to avoid complexity.
B)Detector concept:
The detection based on identification of
radial pressure gradient in leaks is presented here.
The main requirement is the system should detect
leaks at angle ᶲ around the circumference of the pipe.

21
To achieve the full observability around the
circumference, a circular membrane is used. The
membrane is moving close to the pipe walls at all
times for any variable diameter and defects on walls.
The membrane is suspended by rigid body called
drum.

It is rotated around the center point G .In
case of a leak, the membrane is pulled toward it. By
touching the walls, pressure difference ∆p creates
normal force F on membrane, given by
F = ∆p ALeak (1)
Where ALeak stands for cross sectional area of the leak
of any shape.
Fig.2 , Detection concept: [a] “Approach Phase”:
The detector is moving form left to right with the
carrier’s help.
Only the drum and the membrane are depicted for
simplicity.
[b] “Detection PhaseA”: The membrane is pulled
toward
the leak due to the suction caused by the drop in the
pressure.
[c] “Detection Phase B”: The membrane touches the
walls and covers the leak. As PipeGuard moves
along the pipe a new force, Fz is generated.
[d] “Detaching Phase”: The membrane detaches from
the leak and the drum returns to the initial position
As PipeGuard travels along the pipe, new
force is generated (FZ) force is a result of friction
between the membrane and pipe walls Fz related to
normal force,F, by friction model, say Fz =g(F).Fz
generates equivalent force and torque on drum. M
forces the drum to rotate about axis through the
center while orientation of axis depends on ᶲ.Effect of
M is sensed by force and displacement sensors
mounted on detector.F2 vanishes when membrane
detaches from the leak and drum bounces back to
neutral position. The proposed system can identify
leaks by measuring the forces on the drum.The
problem now has changed from radial pressure
gradient to measuring forces on a mechanism.
III.DETECTOR DESIGN
A)Detector Analysis:
Here, the analysis of forces acting on the
detector and placement of sensors on final design.
Also detection algorithm for leak detection is
proposed.
1)Force Analysis: First-order statics on detector is
discussed. It is assumed that drum is allowed to
perform small rotations and thus analysis is accurate
when motion of drum is small and dynamics
insignificant. We know, Fz =-Fz ez is generated at
leak positions. The force generates torque about
G,the center of gimbal mechanism given by,
M =FzReᶲ
=FzR(cos ᶲey - sin ᶲ ex) (2)
The drum is supported at three points A,B and C.
Distance between each of these points and the center
of gimbal G is equal to r. These points are 2 π /3
away from each other. Also, points A, B ,C are the
points where the springs are mounted. By adjusting
preloading on springs we, independently adjust the
forces on the supports at the neutral position .When
leak incidence occurs, disturbance torque M
stemming from Fz arises. This torque changes the
support forces at points A, B, and C, by ˜ FA, ˜ FB ,
and ˜ FC correspondingly and given as,
˜M x = [ ˜ FAr − ( ˜ FB + ˜ FC )rsin(π/6)]ˆex (3)
˜M y = [ ˜ FC − ˜ FB] rcos(π/6)]ˆey . (4)
And total change in support torque due to leak
incidence is given by ,
~ M support = ~ M x + ~ My (5)
For total support force at A ,
FA = ~FA + ~FA,
Where first component stands for mean value at all
times due to preloading of spring mounted at A.
And the latter component (˜ FA) valid only at
leak incidents and represents the change in the force
due to the disturbance from the leak.

22
It is assumed that for the analysis, that the
drum is allowed to perform small movements, and
thus, static analysis is accurate to first order. To
complete the analysis, we need to equilibrate the
torques and forces acting on the system in case of a
leak. For this, we need to set
˜M support = M,
using (2)–(5).Also, it is assumed that Fz is balanced
by the support provided by the axes of the gimbal at
point G. So, for the sum of the three changes in the
support forces at points A, B, and C ,
˜ FA + ˜ FB + ˜ FC ≈ 0. (6)
We can now solve the system of
equations for the three unknown support forces
˜FA = -2 Rsinᶲ / 3r Fz êz (7)
˜FB = R sinᶲ - √3 cosᶲ /3r Fz êZ (8)
˜FC = R sin (sinᶲ + √3 cos ᶲ) / 3r Fz êz (9)
It can be concluded that depending on the value of
the incidence angle φ, the signals captured by
appropriate force sensors mounted at points A, B, C
are different in the amplitude and phase. For
completeness, the forces that are sensed by the force
sensors installed on the detector’s sensor chassis are
always opposite in sign from the support forces
calculated in (7)–(9). We can write
˜FA Sensor
= −˜FA = 2Rsinφ / 3r Fzˆ eZ (10)
˜FB Sensor
= −˜FB = R √3cos φ − sin φ / 3r Fzˆ ez (11)
˜FC Sensor
= −˜FC = −R sin φ +√3cos φ /3r Fzˆ ez
(12)
.
2) Sensor Placement and Algorithm:
By installing two force sensors on the
supports, measure the corresponding forces directly.
The idea is to measure the support forces as a result
of the leak force Fz , instead of measuring the leak
pressure gradient directly. Consider a simple case of
a single leak at φ = 0o . In such case, a force sensor
installed on point A would not give any change in the
measurement (˜ FA Sensor = 0 for φ = 0o ). Another
sensor placed on either point B or C will be able to
measure change in the signals due to the leak and,
thus, the detector will be able to eventually identify
the leak/defect in the pipe. In addition, we use the
following metric in order to effectively trigger alarms
in case of leaks
J(t, T) = FBSensor
( )2
+~ FC Sensor
( )2
d
(13)
where T is the integration period. Whenever J(t, T) >
c, where c is a predefined constant, a leak is
identified. c represents a threshold, above which an
alarm is triggered and the existence of a leak is
assumed. This quantity should be in order to neglect
the noise and at the same time avoid false positives..
IV.PROTOTYPE AND INSTRUMENTATION
A)PipeGuard’s Carrier:
There are two modules namely carrier and
detector present in this PipeGuard. Some preceding
sections deals with the detector design and concepts.
System’s locomotion is provided by the carrier. The
carrier module contains sensors, actuators, power
along with communication and signal processing
unit.
B)Electronics Architecture:
According to our design requirements,the
robot must be capable of performing the following
tasks:
 Move and regulate the speed inside pipes;
 By measuring signal from two force censors
at higher sampling rates it should identify
leak;
 Has to communicate wirelessly with the
“Command Center”.

23
Fig.3 , High-level system architecture of PipeGuard.
Two microcontrollers are installed on the system for
simultaneous speed regulation and leak
detection.Wifi is used here for transmission of the
data signals from the detector to the central system.
Architecture of the pipeguard is developed
in such a way that it will meet all these requirements.
Two microcontrollers are used to perform above
tasks. Microcontroller#1 is dedicated to real-time
leak sensing while microcontroller#2 performs speed
regulation.The workflow is as follows: A motion
command is specified on the computer by the user
and the motion command along with desired position
and speed is sent to the PipeGuard by the computer.
The command is delivered to the microcontroller#2
after the robot’s Wi-Fi transceiver receives it. To
regulate the carrier’s speed, closed-loop speed control
is performed by microcontroller#2. At that instance it
evaluates the speed (by measuring the encoder signal)
and stop the system when it reaches the end point of
the pipe section (or any other point prescribed by the
operator along the pipe) by sending appropriate
command. On the other hand microcontroller#1 holds
the responsibility for leak detection and sending the
sensor data towards the Wi-Fi transceiver. Signals of
two force censors mounted on the detector are
received by this microcontroller. At that same
instance the measured position from the carrier’s
encoder is also received. This position data is
compiled with the correlated force sensor data and
sent towards the Wi-Fi transceiver. Then that datais
received and decomposed by theWi-Fi receiver on
the command center and supply it to the user through
the graphical user interface on the computer.
V .EXPERIMENTAL VALIDATION
A)Understanding leak Signals:
The initial detection results are evaluation of
the system moving at slow speed inside the pipe.
Hence the detector passes consecutive openings of
diameter 2-3 mm. A constant line pressure equal to
1.4 bars is maintained throughout the experiment.
Signals captured by the detector clearly indicates the
existence of leaks. The signals from two sensors
while the system came across two same kind of leaks
at an angle φ ≈ 270◦ is inversely related to the signals
from two sensors while the system came across two
same kind of leaks at an angle φ ≈ 45◦. Hence one’s
magnitude at each leak increases while other’s
decreases as both were inversely . From this we can
identify that the force on sensor 2 is of pulling while
force of sensor 1 is of pushing nature.These
differences exist because of each leak is located at
different angles and as a result different pair of FZ
and M about G is obtained. We can design and
develop algorithms for estimating magnitude of the
leaks and the position. Now we can conclude that a
change in signal will exist whenever the system
passes a leakage.
B)Low-Speed Detection :
In the next step, the system (carrier +
detector) is let to run inside the pipe at relatively
higher, but still at low speeds. Let’s we command the
PipeGuard to run at ωd= 2 Hz (almost equals to νd=
0.19 m/s). The system can traverse the entire distance
approximately at 5s. Signals may be corrupted by
noise when PipeGuard approaches leak, but the
amplitude of the noise is much smaller than that of
the signal. Hence in four phases the detection occurs.
First the PipeGuard approaches the leak and
then because of radial pressure gradient the
membrane moves towards the leak. As a result of
this small movement a small change is experienced
by the signals. A force Fzgets generated while the
membrane touches the wall at leak position. The
drum is pushed to move by the latter torque and
because of this, a significant change may exist in the
signals of the two force censors. When the membrane
detaches from the leak, the signals increases
continuously till a certain point. When the signal
reach this point the drum goes to the neutral positions
and the signals came back to their mean (nominal)
values.
Now another one experiment is carried out
by opening both the leaks in the pipe line. Once again
the pipe line is instructed to move at νd= 0.19 m/s.
The signals captured while the detector passes the
two consecutive leaks is shown in Fig.16. Because of
the existence of leak #2, the line pressure at leak #1 is
reduces and as a result leak #1’s signal magnitude

24
becomes smaller than leak #2’s magnitude. Alarm
can be made triggering at times ti
*
by selecting the
respective thresholds carefully.From this we can
know that the signals captured while the PipeGuard
passes leak #1 are in phase and the signals captured
at leak #2 are out of phase. Because of different angle
on the circumference it occurs.
C)High-Speed Detection:
The PipeGuard can move at high speed
inside the pipe. Experiment illustrated that the
saturation of PipeGuard’s motor is happens atωd=
9.23 Hz (almost equals to νd= 0.875 m/s) and the
PipeGuard can inspect at more than 3 Km/h rate at
this speed.The PipeGuard is capable of inspecting the
pipelines even at these high speeds in a reliable
fashion. One can trigger the alarms only at the
presence of leaks and can avoid false positives by
carefully selecting the triggering thresholds. Fig
illustrated below shows the leak signals captured at
those high speeds. We can see significant leak signal
though the noise level is higher in these cases. One
can make the sensor to avoid higher noise levels by
increasing the threshold so that It will avoid any
potential false positives but at the cost of reduction in
detection sensitivity.
Signals presented here are collected at 160 Hz for
each sensor. The line pressure (at the compressor) is
equal to 1.4 bar. PipeGuard is moving at
approximately 0.875 m/s inside the pipe. In addition,
the metric J(t, T = 0.1 s) is plotted here. Two leaks
are successfully identified.
Fig.4, Sensor signals as PipeGuard moves along the
pipe.
VI. CONCLUSION AND FUTURE WORK
This paper discussed about leak detection
concept and design. On the basis of the basic
principle behind detection it is stated that the system
is capable of detecting leaks in a robust and reliable
fashion. In specific the principle of detection is based
on the identification of localized pressure gradient
existence. Unlike most of the current methods the
proposed system is pipe size and pipe material
independent.Direct measurement of the pressure to
calculate the gradient at each point is inefficient. In
addition to this observing the leak, which can occur
at different angles around the pipe’s circumference
requires a series of sensors capable of measuring
pressure. The system that we propose and design
employs a mechanism in which the problem is shifted
from measuring the pressure directly at each point to
measurement of force by a mechanism.
In a laboratory setup prototype for the
proposed system was built and tested. The system has
the capability of identifying radial pressure based
leaks. Even at high speed and low pressure it detects
small consecutive leaks to a maximum accuracy.
Signal-to-noise ratio at high pressure is higher and it
detects in a robust and reliable manner. Trigger
alarms at leak’s positions and quantifying metric for
leak signals are proposed finally.Our future progress
eyes in optimization and refinement of the detector’s
design so that sensitivity at lower pressures can be
increased. Apart from this we plan to accommodate
both water and gas applications to this technology
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25
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