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Raghied Atta and Naseer AhmadTaibah University, Saudi Arabia
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Importance of Underground Pipelines
•3.5 million km of
pipeline in 120 countries around theworld.
•The United States had65%, Russia had 8%,and Canada had 3%
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Pipeline Transport
Oil “steel or plastic pipes”
Natural gas “carbon steel pipes”
Water “Cold, Hot and Steam”
SewageBrine
Alcohol Ammonia
Milk
beer
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Underground Pipeline Failure Pipeline failure can
cause severe damage to human health andproperty and
interruption of water,gas or oil supplies
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Landslides and Displacement
Underground pipelines are difficult to be inspected
The systems should be designed for near zero leakage.
They must account for thermal expansion, degradation ofmaterial, high-pressure and hydraulic shock, heat loss/gain,and corrosion.
Displacement and possible failure of the pipeline might
result because of the displacement induced landslides.
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Ground Pipelines Installation The pipe network is buried
underground for safety and to
avoid any disruption“presence on ground” .
For buried non-pressureapplications trench
construction, bedding,haunching, initial backfill,compaction, and finalbackfill.
Following StandardPractice for UndergroundInstallation of
Thermoplastic Pipe andOther Gravit -Flow
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Trenches Specifications Adequate width to allow convenient installation,
As narrow as possible “Joining pipe outside thetrench and lowering it into the trench”
Trench widths will have to be wider where thermal
expansion and contraction is a factor.Trench depth is determined by intended service and
local conditions.
Susceptible to freezing liquids should be buried noless than 12" below the maximum frost level.
Permanent lines subjected to heavy traffic should
have a minimum cover of 24".
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Pipeline Materials Pipe material selection and joining methods are governed
by the utility service T & P. Commonly used direct-buried carrier pipes
Ductile iron (DI)
polyvinyl chloride (PVC)
high-density polyethylene (HDPE)
Crosslinked polyethylene (PEX)
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Faults in the Pipeline
The pipeline faults
depend on a variety ofconditions including:
Pipeline material
(e.g. metallic,concrete and HDPE)
Pipeline diameters
Difference ingeotechnical conditions
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Ground Deformation Effect Permanent ground deformation imposes :
Flexural bendingShear on the pipeline
Axial compression or tension, depending on theorientation of the pipeline crossing an active fault.
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Joint Failure Joint is also another primary cause of pipe failure.
Under axial compression Crushing of the jointbell
Under axial tension Joint pullout
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iron pipe joint failure (10 years). iron pipe joint corrosion (18 years
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Strain
High magnitude, repetitive strainscan lead to fatigue or yielding inthe material.
Strain is therefore an importantmeasurement for pipelines
structural integrity and condition monitoring.
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Pipelines Nondestructive Test Techniques
Technologies such as thermal imaging technique is used fordetecting pipelines failure but it has its own limitations.
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Ground Penetrating Radar and Guided Waves Techniques such as ground penetrating
radar and guided waves can also detectsubterranean conditions from the surface.
However, these techniques are stillunreliable for accurate characterization ofpipeline damage.
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Wire Integrated along the Pipelines Copper wires can be installed during
fabrication to aid in detecting andlocating liquid leaks in the pre-insulatedpiping system.
These systems can monitor the entirelength of the underground piping systemby looking for a short circuit test ormonitor the impedance change.
The copper wires can also be used as atracer wire for future locating the buriedpipe using metal detectors.
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Sensors Integrated into Pipelines Sensors integrated into
pipelines coupled witha delivery of sensedinformation
Benefits for pipelinesoperators include:
Fewer catastrophic failures Improved emergency response
Conservation of natural resources
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Data acquisition device
performs analog-to-digitalconversion of signals,filtration, hits (useful signals)detection and it parametersevaluation, data analysis andcharting “Sophisticated”!!”.
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Fiber-optic Sensor Recent studies have been conducted to monitor pipeline
buckling with distributed Brillouin fiber sensor.
Sensitive but temperature dependent
Strains gauges can also be used to estimate a structure’sstresses, loads and moments.
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Sensors Connection Sensors used to measure pipeline characteristics can be
connected by wires or fiber optic. Wires are usually long and can be a subject to breakage or
connector failures.
They need installation and long term maintenance .
Limits the number of sensors used
Affects the overall quality of reported data.
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Wireless Sensor Network “WSN” Using wireless networks for sensing making installation
much easier and more efficient.
The WSN is a smart programmable solution:
Fast data acquisition
Reliable
Accurate over long termRequires no real maintenance
Costs little to purchase
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Event-driven Triggering The proposed monitoring system is based on the
development of a sensor network with event-driventriggering of the wireless data transmission.
It can run on semi-active or even absolutely sleeping modes “make it consumes very little power”.
WSN Pl f d f Pi li
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WSN Platform used for Pipelines
Structural Monitoring
•Multiple nodes grouped in a star topology.
•Each of these groups can further form a node in a two-peer network topology
Wi l S N d F i l Bl k Di
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Wireless Sensor Node Functional Block Diagram
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Strain Gauges Every sensor node comprises 5 strain gauges
They are attached to one portion of the pipeline They detect stain changes in 3 different directions
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Quarter-bridge Circuit
Each strain gauge is connected as a part of quarter-bridge
circuit
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One-node Circuit
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Star Central NodeThe central node is used to support
communications with the sensor nodes within its star topology.
It consists of an RF-Solutions BRAVO 868 wireless transceiver connected with theMicrochip PIC16f88 microcontroller.
For a large network, multiple of centralnodes with their star node sensors are used.
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Central Nodes CommunicationsThe central nodes communicate with each other
to transfer the sensors’ strain information.Each central node is capable of communication with up to 70 other nodes.
Each node has its 16-digit unique ID
It is transmitted along with the stain informationto identify its location.
The main central node is connected to a PC tostore this information for further analysis &decision making.
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System Power ConsumptionsTo prolong the battery life for buried
wireless sensors a low power prototype was adopted.
the microcontroller is programmed to
operate in a pulsating mode which powerthe sensors’ electronics, whilesynchronously performing ADC.
The RF communications is onlyused if there is any change detected
in the data of the node.
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Battery Life Using a lithium-ion battery with 400 mAh and five
sensor nodes. The life cycle of the sensor network is calculated to be in
the range of three years.
b
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Lab System Setup The strain gauges are installed on 3 axis of the pipeline; X, Y
and R with their lead wires along the length of the pipeline to
measure its response introduced during events of pipelinedisplacement.
In total a set of five strain gauges are installed at each node; 2 horizontal “on opposite faces”, 2 vertical plan “on opposite
faces” and one along the circumference direction.
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Deformations Measurements (bending) Two nodes with 5 strain gauges each were prepared
The pipe was subjected to controlled deformations (bending)using three point bending procedure
C i d
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Compressive Loads
Pipe is subjected to compressive loads, which eventually
buckle the pipe.
l l h
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By measuring the change in the strain gauge resistance, the
output voltage V0 of the strain gauge can be calculated:
Alternatively the bridge voltage change is directly measured
Calculating the Strain ϵ
where GF = Gage Factor
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where GF = Gage Factor
A GF of 2 was selected as recommended by the manufacturer(Omega) for the strain gauges made of Constantan material
type
where RG is used to control the gain value of the
instrumentation amplifier.
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Results and Discussion The strain gauges showed the strain in the form of tension
and compression as per their location.
Strain at various locations during radial loading
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Data Prediction
The data in the Figure can be used to predictthe redial deformation at any node.
Known deformations were introduced at node 1.Predict deformations at node 2.
This can be further extended to know the radialdeformation at any other point along the pipe.
“provide that the bend is linear ”
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Applying Axial Compression Along the Pipeline
The pipe was compressed between 1 mm and 2 mm along the lengthand it can be seen that all the gauges showed approximately similarchange in strain.
B kli
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Buckling
When the pipe was further compressed axially to about 5.5
mm, this resulted in sudden buckling of the pipe. The gauges showed the effect in the form of strains in all
directions
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FBG Strain Measurement under Pressure
PVC pipe with 3 mm thick wall, standard dimensional ratio(SDR) of 41 and a length of 2 meters that was sealed on
both ends to facilitate its pressurizing with compressed air .
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FBG Spectrum The spectrum detected of 5 FBG sensors with different Bragg
wavelengths separated by 5 Km of single modecommunication fiber
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FBG vs Strain Gauge
R² = 0.9869
-0.05%
0.05%
0.15%
0.25%
0.35%
0 10 20 30 40 50 60 70 80 90 100 R E L A T I V E C H A N
G E
PRESSURE, PSI
ELECTRICAL GAUGERELATIVE CHANGE IN RESISTANCE
Increasing Pressure
Decreasing PressureLinear (DLB/LB0)
Linear (Decreasing Pressure)
R² = 0.999
-0.05%
0.00%
0.05%
0.10%
0.15%
0.20%
0.25%
0.30%
0 10 2 0 30 40 50 60 7 0 8 0 90 10 0 R E L A T I V E C H A N
G E
PRESSURE, PSI
FBG Relative Change (Detuning)in Bragg Wavelength
Increasing Pressure Decreasing Pressure
Linear (DR/R0) Linear (Decreasing Pressure)
Conclusions
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Conclusions
In this paper, a technique for predicting pipeline faults is
proposed by continuously sensing the strain across the pipeline
using WSN distributed along the longitudinal axis of thepipeline.
A set of 5 strain gauges connected to each node of thenetwork measures the hoop and axial strain along thepipeline.
Each node contains strain gauge regulated sensorexcitation, instrumentation amplifiers withprogrammable gains, microcontroller with an on-boardmemory and A/D, and bi-directional RF serial data
transceivers link.
The nodes are capable of continuous RF
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The nodes are capable of continuous RF transmission from over 70 nodes, over frequencybands of 868 MHz, at data rates of 9.6 Kbaud
over a distance of 1 km between them.Collected data from at least two points along the
length of the pipeline helped in predicting the
nature of bend, its direction, magnitude andlocation.
This data is sufficient for predicting any change in
pressure inside the pipe and calculating thechange in length either extension or contraction.
The data was also helpful in showing buckling in
the pipe.
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Acknowledgement
We would like to thank Bin Laden Chair, TaibahUniversity for facilitating measuring equipmentfor this research
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