The document discusses methods for detecting gas leaks in pipelines. It begins with an introduction to the importance and challenges of monitoring vast pipeline networks transporting oil and gas. It then reviews several existing approaches for continuous and non-continuous leak detection, including pressure analysis, mass balance, and acoustic sensors. The document proposes a new hybrid system using both gas sensors and ultrasonic sensors to quickly detect leaks and pinpoint their location. It concludes that while technologies are advancing, the proposed system offers a more accurate and cost-effective solution compared to other current methods.

1. Advanced Gas Leakage Detection Using Acoustic
Sensors
Anushree Tiwari
Department of Instrumentation and Control Engineering
JSS Academy of Technical Education
Noida, India.
anushree.tiwari1995@gmail.com
Abstract—With increasing use of all petroleum-basedfuels in
every part of the world, the demand for transportation of these
energy sources has soared in the last 2 decades. And with most of
the oil wells being situated in the Middle East and Russia, the
process of transportation of these fuels on landorby sea link has
become an increasingly expensive trade. To counter these
expenses, the strongholds of the oil industry have come up with
the concept of pipelines to transport these fuels across continents.
But with transportation of these highly inflammable fuels across
of miles of pipes, the issue of damaging of pipes and subsequent
leakage of these fuels which have the potential to cause
unimaginable consequences has become more prominent. Many
ways have been developed to counter this problem, with various
electronic control systems being deployed with increasing
sensitivity each day. In this paper, we will go through some of the
more common and accurate methods to do the same.
I. INTRODUCTION
Sixty percent of energy in the world is from oil and gas
resources. So, to make transport independent and more
reasonably priced, pipelines were adopted as a more
economical means of transportation. Pipelines today transport
a wide variety of materials including oil, crude oil, refined
products, natural gases, condensate, process gases, as well as
fresh and salt water. Today there are some 1.9 million
kilometers of transport pipelines around the world. In many
cases, due to the longer lengths and the difficult runs of
remotely located pipelines, physical access may be limited.
Pipelines can run through desert, across mountain ranges,
along bodies of water, or be located underground or subsea,
even at depths exceeding 1.6 kilometers. There exists the
potential damage risk in gas pipeline such as impact of
internal and environmental issues, the wave of pressure,
fatigue cracks, tensile strength, material manufacturing errors,
e.g. these potential damage risks can lead to pipeline leakage
which can cause explosion in it. Therefore conducting a
monitoring exercise on gas pipeline is vital. Fault detection in
the gas transmission pipeline in particular the leakage
detection plays a major role not only in safety and protection
of the environment but also in economy of the projects. Thus
leakage detection systems are subject to official regulations
for example API1 and TRFL2. Leakage detection systems
must be sensitive, reliable, accurate, and robust.
Leakage detection systems can be categorized into two
major types; continuous and non-continuous systems. The
non-continuous systems include: Inspection by helicopter,
smart pigging, and even tracking dogs. Three approaches are
possible to avoid leakage over continues system:
• The first, internal on the basis of physical mode such
as mass or volume balance method, pressure point
analysis, statistical systems, Real Time Transient
Model (RTTM) based systems and Extended RTTM.
• Second external implementation based on hardware
such as sensor changing impedance, the volume of
capacitor, fiber optic cable, acoustic sensor, infrared
for image processing.
• Third hybrid, the combination of first and the second
for example, acoustic analysis by balancing mass and
volume.
Review of ways to detect leakage, industry establishes the
combination of sensor technology for monitoring pressure,
flow, compressor conditions, temperature, density and the
other variables. The breakage starts from a pin-sized hole
which can easily be detected by the means of instrumentation.
For instance smart pig sends inside the pipe to detect welding
effect and cracks of the sides using magnetic fluxfeatures and
ultrasounds waves. The use of fiber optic cables for the
monitoring of leakages is based on physical changes that occur
at the leak site. One of those physical changes is a typical
change in temperature profile. To detect such changes, the
fiber optic cable is placed along the pipeline. However, use of
this method is only possible up to limited lengths of pipeline
and many reflections are required to plot a useful temperature
profile Detecting gas leaks using infrared is made possible
through video cameras featuring a special filter which is
sensitive to a selected spectrum of infrared wavelengths.
Certain hydrocarbons absorb infrared radiation from this
spectrum. This makes it possible to detect the leaks as an
image of smoke on the video display. On the other hand there
are mechanical methods for the measurement of diameter and
the thickness of pipe for detection of corrosion. Even though
the above mentioned methods are exact nevertheless they have
sophisticated mathematical description and its analytical
knowledge.
Regarding internal leakage detection system Pressure point
analysis is based on the evaluation of pressure drop or the
pressure profile measured at individual points. As an
impulsive leakage brings up a characteristic change in the
pressure drop, you can check whether the measured pressure

2. drop, DP within a time period DT exceeds set thresholds. In
addition to an upper threshold, a lower threshold for the
pressure is also determined and if either one of these events
occurs; the systemtriggers a leak alarm.
Another type is based on mass principle. According to this
principle, mass in a closed system remains constant and is not
changed by processes within the system. If the pipeline is
considered to be a closed system and you compare the mass
flow at the inlet and the outlet, the difference in a leak-free
case should always equal zero. If, however, a leak occurs, the
system has been opened and mass escapes. This results in a
decrease in the measured mass flow at the outlet and an
increase in the mass flow at the inlet.
Real Time Transient Model or RTTM systems can
compensate for dynamic changes. To do this, they make use of
basic physical laws which the pipeline must obey:
• The conservation of mass principle, which includes
the density ρ, the time t, the flow velocity v and the pipeline
location coordinate s.
• The conservation of momentum principle, which
includes the flow velocity v, the time t, the pressure P, the
pipeline location coordinates s,and the pipeline friction fs.
• The conservation of energy principle, which
includes the enthalpy (h), the time (t), the density (ρ), the
pressure (P) , and the specific loss performance (L).
These physical principles precisely describe the stationary and
transient activity of the flow in the pipeline. Using these
equations flow, pressure, temperature and density can be
calculated and integrated in real time for each point along the
pipeline. These trends are also known as hydraulic profiles
and accurately predict the true performance along the entire
pipeline.
Artificial Neural Network (ANN) methods are used to model
the pipeline in cases where generating mathematical and
analytical models are complex. ANN is an appropriate
candidate for leakage detection by using classification and
estimation function. ANN is a robust method for facing noise
which is suitable for real-time usage. There are different
approaches for the detection of pipes leakage based on ANN.
Recent developments cater around using acoustic sensor and
analyze it by ANN. In a way acoustic sensors are sensitive on
magnitude or velocity of wave (leak signal) due to
characteristics of sound signals which are classified and
trained with ANN and it is used as an ANN input and features
of the signal from leakage analysis under the pipe pressure.
Such signal after passing a filter is classified in several voltage
signals by different frequencies and in output leakage is
detected. ANN has so called number of training stages. Other
researchers have used an approach based on ANN by using
sonic sensors for leakage detection. Such piezoelectric sonic
sensors impose by providing forces from magnitude of flow
changes.
Technologically point of view, WSN and IOT have attracted
the interest of researchers whereas many industrial branches
with different applications are used in the industrial WSN.
There are a variety of approaches in order to adopt advanced
technology in communication and wireless instrumentation
industry on basis of Electronic and Computer are common
shortcomings in monitoring such as weakness of automation
and Real-time is omitted. Regarding remote control based on
Zigbee and WiFi protocols due to limitation of wide band
frequency and low speed in data transmission that is
appropriate small plant and cannot be used for massive plants
for instance pipeline. Therefore these problems have tendency
to lead us towards IOT which TCP/IP protocol. Structure of
IOT is of three layers. Sensors, voltage and current
transducers are placed in the first layer. Microcontroller which
is needed for the processing and wireless communication
along with the servers is also located in this layer. The Second
layer is the network layer which consists of real-time
processed-data and the database. The third is the application
layer including suitable web services for the designed basis
data collection which is illustrated on graphical display for
monitoring of plant performance and exerts control to reduce
the decision making period.
II. LITERATUREREVIEW
A. IOT Based Detection System
In a 2008 paper by Ch. Manohar Raju and N. Shushmita
Rani, an automatic gas leakage detection system had been
mentioned which immediately reads and sends the data to an
android device in any hazardous place. An android application
is capable of accepting data directly via. Bluetooth.
Fig. 1 Block Diagram ofIOT BasedLeakage DetectionSystem.
It is also possible to controlthe bot using text commands or
tabs on the android application. Various otherrobots have been
mentioned which use GSM, GPS or internet based
communication systems. The problem with these types of
systems is the lack of communication in certain areas. To
irradiate these problems, Bluetooth based systems have been
proposed.Wireless communication protocols play an important
role in present trends.
B. Scada I/F Models
In another paper, various techniques were given which use the
SCADA I/F model. The SCADA system has the function of
transferring the acquired data from a pipeline system to a
transient simulation model. Dynamic parameters are collected
every 30 seconds, such as temperature, pressure and flow.

3. Numerical methods based on actual data are used while
simulating transient flow. Pressure and Temperature are taken
as independent variables so as to obtain average pressure and
average temperature. Hence all the parameters of the gas in the
pipeline systemcan be acquired.
Fig. 2 Block Diagram of SCADA BasedDetectionSystem
To carry out leakage detection, the data acquired through the
SCADA system is compared with the transient simulation
model.
Leakage detection model is set up based on continuity
equation, momentum equation, volume mass balance, state
equation and energy equation. The systemincludes 5 modules:
• SCADA I/F
• Dada Bass
• Transient Simulation
• Leakage Detection
• Output
This system is capable of detecting leaks as small as 0.3% of
the nominal gas flow. Pressure is even higher when leakage
point is closer to the inlet and the pressure difference between
gas pressure and atmospheric pressure is even higher. This
gives an almost linear relation between outlet pressure and
leakage detection i.e., this system is more sensitive closer to
the outflow.
C. MQ 9 Based Leakage and Fire Detection System
Fig.3 Block Diagram of User Interactive Gas Leakage andFire Alarmsystem.
The principal use of this leakage detection system is when
inflammable gases like CH4 and the LPG family are
concerned. Since these gases are highly inflammable, there is
a fair chance that any change in the surrounding parameters of
the leakage might cause a fire. Hence, a fire detection module
is also added to the system to prevent loss of life. A small 5V
DC supply is required to power up this system and hence
makes it very easy to install them in remote locations. The
output of the sensor is usually HIGH and goes LOW when gas
is detected.
D. Wireless Sensing Using Macro Fibers.
Flexible macro fibers are composite materials, made of
ceramic fibers which are capable of bending (or flexing) when
an electric current is applied to them. They can also produce a
current when flexed or vibrated. These materials are advanced
forms of piezoelectric materials. Long sensors are made using
this material which is then used to cover entire pipelines.
In one of the proposed system, a two-channel digital tensing
channel is used along with a pressure transducer which is
internally tuned to produce a voltage of 5V for 1 psi pressure.
This voltage is then used to activate a homing device which
notifies the control systemabout a possible leakage.
While this system is more sensitive as compared to other
detection techniques, but it can be activated by anything as
small as an insect. Also, since this system only works if the
leakage is in close proximity of the system. Hence, to
practically use it, entire pipelines will have to be covered with
this material. This makes its installation cost astronomically
high, and hence this method hasn't been used commercially.
III. PROPOSED SYSTEM
While various technologies have been discussed in the last
two decades to develop more efficient and universal leakage
detection techniques, the most efficient way still to detect the
leakage of gases is by using specific gas sensors. But this
process does not give the exact location of the leakage site.
Hence, to make this system more reliable, and with the ability
to detect the exact site of the leakage, a new systemis proposed
which uses the services ofan ultrasonic sensor along with a gas
sensor.
This systemhas 5 parts:
• Microcontroller
• Gas Sensor
• Ultrasonic Sensor
• Bluetooth Module
• Alarm and LED display
The output of any Gas Sensor is typically HIGH, but it
becomes LOW when it detects the gas. But this is a slow
process and does not give the exact location of the fissure.
When there is a sudden burst in the pipeline, a solid
material is sprayed outward due to the low pressure inside the
pipeline. If an active ultrasonic sensor is available in this
vicinity, the debris can be easily detected by it. This will give
the exact location of the fissure. Although any detection given
by the ultrasonic sensor does not essentially prove that there
has been a leakage as an ultrasonic sensorcan also be activated

4. by an insect or dust particles. Hence, post-detection, the
ultrasonic sensor will wait for a certain time, which will depend
on the number of gas sensors used and how far apart they are
placed, and if the gas sensor also goes LOW, the system will
notify of the leakage and will give the exact location of the
leakage. This method can be even more effective in liquid
pipelines like petroleum et all.
Both the modules need a minimum current to operate and
hence the system is cheap and more reliable than most of the
systems currently in use.
IV. CONCLUSION
With gas and petroleum being one of the largest industries
in the world, it is empirical to make sure that the transportation
of these materials is carried out in a much safer manner. Even
though various new technologies are emerging to make this
process even more safe and accurate, we are still a few years
away from such revolutionary technologies like optical fiber or
PZT materials being used for detection. Hence, the proposed
system is one of the more advanced ways to locate leakages
more accurately and effectively. This will not only save a lot of
money, but also will it reduce the various risks associated with
pipeline leakages.
ACKNOWLEDGMENT
I would like to thank Mr. K.C.Yatheesh for giving me this
opportunity to research on various models of pipeline leakage
detection and I would like to extend my gratitude to him for
being of such help throughout my research and the subsequent
work on this paper.
REFERENCES
[1] Vasudev Yadav, Akhilesh Shukla, "Areviewon Microcontroller based
Gas Leakage Detector." Journal ofVLSI Design andSignal Processing,
Volume 2 Issue 3.
[2] Mohsen Rahmati, " Leakage Detectionin Gas Pipeline usingArtificial
Neural Networks based on Wireless Sensor Network and Internet of
Things."
[3] MiladGolshan, Aidin Ghavamian, Ali MohammedAli Abdulshaheed, "
Pipeline MonitoringSystemby UsingWireless Sensor Networks."