defect identification in pipe lines using pipe inspection ... · 20 int. j. mech. eng. & rob....

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Int. J. Mech. Eng. & Rob. Res. 2012 E Navin Prasad et al., 2012

DEFECT IDENTIFICATION IN PIPE LINES USINGPIPE INSPECTION ROBOT

E Navin Prasad1*, M Kannan1, A Azarudeen1 and N Karuppasamy1

*Corresponding Author: E Navin Prasad,[email protected]

Inspection robots are used in many fields of industry. One application is monitoring the inside ofthe pipes and channels, recognizing and solving problems through the interior of pipes or channels.Automated inspection of the inner surface of a pipe can be achieved by a mobile robot. Becausepipelines are typically buried underground, they are in contact with the soil and subject to corrosion,where the steel pipe wall oxidizes, and effectively reducing wall thickness. Although it’s lesscommon, corrosion also can occur on the inside surface of the pipe and reduces the strength ofthe pipe. If crack goes undetected and becomes severe, the pipe can leak and, in rare cases,fail catastrophically. Extensive efforts are made to mitigate corrosion. Pipe inspection isnecessary to locate defects due to corrosion and wear while the pipe is transporting fluids. Thisability is necessary especially when one should inspect an underground pipe. In this work, PipeInspection Robot (PIR) with ability to move inside horizontal and vertical pipes has been designedand fabricated. The robot consists of a motor for driving and camera for monitoring.

Keywords: PIR, Inspection robot, Pipe inspection, Pipe defects, Mobile robot

INTRODUCTIONRobotics is one of the fastest growingengineering fields of today. Robots aredesigned to remove the human factor fromlabor intensive or dangerous work and also toact in inaccessible environment. The use ofrobots is more common today than everbefore and it is no longer exclusively used bythe heavy production industries. (Horodincaet al., 2002).

ISSN 2278 – 0149 www.ijmerr.comVol. 1, No. 2, July 2012

© 2012 IJMERR. All Rights Reserved

Int. J. Mech. Eng. & Rob. Res. 2012

1 Dhanalakshmi Srinivasan Engineering College, Perambalur 621212 (Affiliated to Anna University Chennai), India.

The inspection of pipes may be relevant forimproving security and efficiency in industrialplants. These specif ic operations asinspection, maintenance, cleaning etc. areexpensive, thus the application of the robotsappears to be one of the most attractivesolutions. Pipelines which are tools fortransporting oils, gases and other fluids suchas chemicals, have been employed as majorutilities in a number of countries for long time.

Research Paper

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Recently, many troubles occur in pipelines, andmost of them are caused by aging, corrosion,cracks, and mechanical damages from thethird parties. Currently, the applications ofrobots for the maintenance of the pipelineutilities are considered as one of the mostattractive solutions available (Mhramatsuet al., 2000) Pipe Inspection Robot is shownin Figure 1.

Figure 1: Pipe Inspection Robot (PIR)

SELECTION OF MATERIALSThe materials used for this machine are lightand rigid. Different materials can be used fordifferent parts of the robot. For optimum useof power the materials used should be lightand strong. Wood is light but it is subjected towear if used for this machine. Metals are theideal materials for the robot as most if theplastics cannot be as strong as metals. Materialshould be ductile, less brittleness, malleable,and high magnetic susceptibility.

Among the metals, aluminum is the materialchosen for the linkages and the common rod,which is made as hollow for reduction in weight.However, other materials are chosen for themotor. The materials chosen for the motor

should have high magnetic susceptibility andshould be good conductor of electricity. Thematerials are copper and so on. But aluminumis chosen as the materials for the linkages andcentral body because of its much-desiredproperties.

Aluminum has lightweight and strength; itcan be used in a variety of applications.Aluminum alloys with a wide range ofproperties are used in engineering structures.The strength and durability of aluminum alloysvary widely, not only because of thecomponents of the specific alloy, but alsobecause of heat treatments and manufacturingprocesses.

Effect of Temperature:

Another important property of aluminum alloysis their sensitivity to heat. Workshopprocedures involving heating are complicatedby the fact that aluminum, unlike steel, will meltwithout first glowing red. Aluminum alloys, likeall structural alloys, are also subject to internalstresses following heating operations such aswelding and casting. The problem withaluminum alloys in this regard is their lowmelting point, which make them moresusceptible to distortions from thermallyinduced stress relief.

• The toughness, as measured by crackpropagation energy, decreases as yieldstress increases.

• At the same yield stress, the under agedstructure has greater toughness than theover aged structure.

MECHANISMThe mechanism involved here is a four barmechanism consisting of three revolute joints

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and one prismatic joint as depicted (Figure 2)(Paul E Sandin, 2003).

consisting of three revolute joins and oneprismatic as depicted. Thus, the motion ofall revolute joints can be described in termsof the displacement d

b (Jadran and Roth,

2006).

Static Analysis

In order to decide the actuator size, it isnecessary to perform the static analysis.Assume that in (Figure 4), F

cx and F

cz denote

the reaction force and the traction force exertedon the four-bar by the driving wheel,respectively. Now applying the virtual workprinciple to the free-body diagram of (Figure4) gives:

Figure 2: Mechanism of PIR

Mechanism of Pipe Inspection Robot

H = 2r + 2d + 2h2cos

h1 = 24 mm, h

2 = 56 mm, h

3 = 84mm (h

1 =

OA, h2 = BC = D, h

3 = CF)

Where D-Diameter of the pipe in mm,

d-Distance between EE’ in mm.

h1, h

2, h

3 are the length of the links in mm.

r-Radius of the wheel.

For uniform Diameter, assume = 45°

D = 2*25 + 2*22.5 + 2*56*cos45°

D = 174.195 mm

Kinematics of Mechanism

The linkage structure can be represented as(Figure 3). This is a four-bar mechanism

Figure 3: Linkages of PIR

Figure 4: Static Analysis

Fcx

Fbx

Prismatic Joint

Fcz

1.33L

Wheel

C

L

BF

bz

TranslationalElement

CentralFrame

L

Hinge Joint

Faz

JointF

ax

A

Static Analysis

W = Fczz – F

bxx = 0

where Fbx

is a spring force.

This is because only Fcz

and Fbx

conductwork. The corresponding coordinates of theseforces relative to the coordinate located at theA hinge are expressed as:

z = 2.33l sin, x = 2.33l cos

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W = Fcz(2.33l sin) – F

bx(–2.33l cos)

= Fcz

*2.333l cos– Fbx

*2.33l sin.= 0

Rearranging gives

Fbx

= Fcz

*cos/sin

Thus, the spring force at the prismatic jointB is related to the normal force F

cz by

Fbx

= Fcz

*tan

And the total weight W of the robot is thesum of the six traction forces exerted on thebelt. Thus, each traction force F

cx is one six of

the whole weight of the robot structure. Thus,the size of the actuator enclosed in the wheelis calculated by

= Fcx

*R = WR/6

Where R is the radius of the wheel. Fromthe above static analysis, it is also known thatthe large weight of the robot does not influencethe foldable motion of the linkage.

The spring stiffness is found to be 0.9 N/mm and the spring force is found to be 4.5.Thus we came to the conclusion that theactuator should have atleast 3 kg torque. So,we used 3 actuators with 1.5 kg torque (total4.5 kg torque). It is safe to use an actuator withmore torque than the required torque.

DESIGN

Helical Spring (Figure 5)

Inner dia – 20 mm

Outer dia – 24 mm

Pitch – 5 mm

Length of the spring – 60 mm

Material – Stainless steel

Translational Element (Figure 6)

Inner diameter – 20 mm

Outer diameter – 25 mm

Length of the element – 40 mm

Material – Aluminum

Figure 5: Helical Spring

Figure 6: Translational Element

Wheel

Dia – 50 mm

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Distance Between the ExtremeDrilled Holes (Figure 7)

Link 1 – 24 mm

Link2 – 56 mm

Link3 – 84 mm

Thickness – 3 mm

Fillet – 5 mm

Width – 10 mm

Drilled holes – 6 mm

Material – Aluminum

EXPERIMENTATIONThe main part of the fabrication of the pipeinspection robot involves drilling and shearingoperations. The drilling is done for makingholes for insertion of the rivets. The linkagesare linked to one another using rivets. In asingle 4 bar linkage each of the four links areconnected by a rivet. Three linkages areconnected to the central body at 120 degreesusing rivets.

Thus, drilling operation is needed forfacilitating holes for the insertion of these rivets.The rivet diameter used here is 5 mm. Thus,the hole drilled must be 5 mm or higher. But,the drilled hole for the central body at its centrewould be 15 mm for insertion of pencil batteries.The actual linkages are cut from an aluminumsheet. The thickness of the aluminum sheet isaround 3 mm. The single aluminum is cut intorectangular sheets of required length andbreadth. This is done using a shearingmachine. Welding also needs to be done toattach the joints which hold the links by a rivet.Welding process used was the brazingprocess.

Figure 7: Distance Between the ExtremeLinks

Central Element (Figure 8)

Hollow

Inner dia – 15 mm

Outer dia – 20 mm

Length – 220 mm

Material – Al

Figure 8: Central Element

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COMPONENTS OF PI ROBOTCentral Frame

Central body is the frame of the robot(Figure 9). It supports all other componentsand holds batteries at the centre of the body.The joints are brazed on the central frameat 120 degrees. The central body is drilledand its ends are threaded internally for theinsertion of pencil batteries and closing withexternally threaded caps. Wireless camerais fixed at one end of the frame.

Compression Spring

A spring is an elastic object used to storemechanical Energy. Spring used here is madeout of hardened steel. Compression spring(Figure 9) is mainly used to exert tension. Thepurpose of spring is as follows:

• The force that the minirobot mechanismexercises on the pipe walls is generatedwith the help of an extensible spring.

• The helical spring disposed on the centralaxis assures the repositioning of thestructure, in the case of the pipe diameters’variation.

Links

Each resistant body in a machine which movesrelative to another resistant body is calledKinematic link or element. A resistant body iswhich do not go under deformation whiletransmitting the force. Links (Figure 10) arethe major part of the robot which translatesmotion. Links are connected to form a linkage.The mechanism involved here is a 4 barmechanism which has 3 revolute pairs and1 single prismatic pairs as depicted. Linksholds the receiver, switch, and 9v battery forthe camera. Also it supports the actuator.

Figure 9: Major Components

Translational Element

Translational Element (Figure 9) is themovable part in the robot which slides alongthe central body for repositioning in caseof pipe diameter variation. This element isdrilled at the centre for the translating alongthe central body. This will restrict the linksto some extreme angles beyond which itcould not be translated. The extreme anglesare found to be 15 degrees and 60 degrees.The joints are brazed on the translationalelement at 120 degrees for the links to befixed onto it.

Figure 10: Links

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Actuators

Actuators are the drive for the robot (Figure11). Since we have chosen aluminum materialfor fabrication, the weight is comparativelyless. So the motor should have 2 kg torque totravel inside the pipe. We used 3 motors whichhas 1 kg torque to make the robot in motion.The supply for the motor is 6v which is fromthe central body. The 3 motors are placed at120 degrees and are supported on the linksby a tag.

electrical conductors or “wires”. The distancesinvolved may be short or long (Figure 12).

Figure 11: Actuator

Batteries

Batteries give supply for a motor andwireless camera. Motor and radio frequencygets 6v supply from the central body andwireless camera gets supply from a 9vbattery. And 3v batteries for transmitter whichhas two toggle switch. One is for motorforward and reverse control and the otherone is for glowing LED’s.

Wireless Camera

Wireless communication is the transfer ofinformation over a distance without the use of

Figure 12: Wireless Camera

Wireless cameras have a channel also. Thereceiver has channels to tune in and then youget the picture. The wireless camera pictureis sent by the transmitter the receiver collectsthis signal and outputs it to your TV or in adesktop by a TV tuner card. Camera is fixedat the one end of the frame and the robot ismeant for inspection inside a pipe which couldbe monitored in a desktop. Camera transmitssignal to the receiver which receives the signaland is connected to the monitor to view theinner side of the pipe.

MACHINING PROCESSConventional machining is one of the mostimportant material removal methods. The threeprincipal machining processes are classifiedas turning, drilling and milling.

Machinability Ratings• Aluminum – Good to excellent

• Brass – Good to excellent

• Cast Iron – Fair to good

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There are various drilling tools or drillingmachines available. The drilling machine usedwas the radial drilling machine.

Radial Arm Drill Machine

The biggest radial arm drill presses are ableto drill holes as large as four inches (101.6 mm)in diameter. But for this project only holes of5 mm and 6 mm were needed. The drilling wasdone on the aluminum sheets for the requireddimensions and then the finished componentwas filed and reverses drilled using a largerdrill bit for a good finish.

Boring Operation

The boring process can be carried out on alathe for smaller operations, but for largerproduction pieces a special boring mill (workpiece rotation around a vertical axis) or ahorizontal boring machine (rotation aroundhorizontal axis) are used. A tapered hole canalso be made by swiveling the head.

Gas Welding

The most common gas welding process isoxyfuel welding, also known as oxyacetylenewelding. It is still widely used for welding pipesand tubes, as well as repair work. Oxy fuelequipment is versatile, lending itself not onlyto some sorts of iron or steel welding but alsoto brazing, braze-welding, metal heating (forbending and forming), and also oxyfuelcutting.

The equipment is relatively inexpensive andsimple, generally employing the combustionof acetylene in oxygen to produce a weldingflame temperature of about 3100 °C.

Brazing

Brazing is the joining of metals through the useof heat and a filler metal—one whose melting

temperature is above 840 °F (450 °C) butbelow the melting point of the metals beingjoined (Figure 13).

Figure 13: Principle of Brazing

Broad Heat toBase Metals

Filler Metal Applied,Instantly Melted andDrawn Through Joint

A brazed joint is made in a completelydifferent way from a welded joint. The first bigdifference is n temperature. Brazing doesn’tmelt the base metals. So, brazing temperaturesare invariably lower than the melting points ofthe base metals. If brazing doesn’t fuse thebase metals, how does it join them? It joinsthem by creating a metallurgical bond betweenthe filler metal and the surfaces of the twometals being joined (Figure 14).

Surface Grinding Operation is used toproduce a smooth finish on flat surfaces.

Figure 14: Bonding at Interfaces

Brazing Filler Metal 0.003 –Thick (0.076 mm)

Base Matel

Base Matel

Metallurgical Bonding at Interfaces

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Surface Finishing

Polishing and buffing (Figure 15) are finishingprocesses for smoothing a work piece’ssurface using an abrasive and a work wheel.Polishing is a more aggressive process whilebuffing is less harsh, which leads to asmoother, brighter finish.

THE WIRELESS CAMERATransmitter

The power is provided by battery and/ortransformer/adapter. The complete (Figure 16)wiring for the wireless camera and transmitterend follows:

Figure 15: Links Before and After Buffing

WIRELESSCOMMUNICATIONRadio Frequency

Radio Frequency (RF) radiation is a subset ofelectromagnetic radiation with a wavelengthof 100 km to 1mm, which is a frequency of 3KHz to 300 GHz, respectively. This range ofelectromagnetic radiation constitutes the radiospectrum and corresponds to the frequencyof alternating current electrical signals used toproduce and detect radio waves. RF can referto electromagnetic oscillations in eitherelectrical circuits or radiation through air andspace. Like other subsets of electromagneticradiation, RF travels at the speed of light.

Antenna

An antenna (or aerial) is a transducerdesigned to transmit or receiveelectromagnetic waves. In other words,antennas convert electromagnetic waves intoelectrical currents and vice versa.

Figure 16: Wireless Camera TransmitterBlock Diagram 1

WirelessTransmitter

WirelessCamera

Video Signal Wire

To Power Supply

Battery Pack

OR

AC Adapter(Plugs intothe Wall)

As in Figure 16, the camera sees animage, sends it to the transmitter, and thetransmitter sends the signal out to the air. Thereceiver picks up the signal and outputs it to aTV/Monitor/Digital Video recorder.

Receiver

After the wireless camera and transmittershave provided the wireless video signal thereceiver collects this signal and routes it theMonitor, TV, VCR or alternative recording orviewing device as shown in Figure 17. Thereceiver accepts the wireless transmitterssignal and then out puts it to your TV, VCR,Monitor or Other Recording Device. Thereceiver needs only power and a Device toview and or record the Signal/Video.

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PI ROBOT TEST RESULTFollowing the design and modeling of theproposed mechanism a prototype unit wasbuilt. The prototype was built for a robot withthe weight of 2.7 kg. The body of the robot wasfabricated mostly from aluminum. The Robot

Figure 17: Wireless Camera ReceiverBlock Diagram 2

Receiver

TV, VCRMonitorOther

Device

Video Signal Wire

Battery Pack

OR

AC Adapter(Plugs in the

Wall)

Figure 18: Pro-E Modeling of PIR

was driven by three dc motors. PIC robottested successfully for movement in horizontaland vertical pipes. The robot has a goodmobility and ability to pass over smallobstacles. The important thing is the amountof force between robot tracked units and pipewall. Even in horizontal moving, attachment ofthe up tracked unit in addition to bottom ones,improve the movement of robot. Because inthis state 3 motors participate in robot movealthough friction is more. In addition to this, therobot is more stable and distribution of loadon different actuators is more similar.Monitoring the pipe inside was suitable andthe control of different actuators was effectivelypossible. The model of PIR is drawn with thehelp of mechanical engineering software tool,Pro ENGINEER Which shown in (Figure 18)and PIR while inspection in various stages areshown in (Figure 19).

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Figure 19: Stages in Locating Defects Inside the Pipe

CONCLUSIONA very important design goal of the roboticsystems is the adaptability to the innerdiameters of the pipes. So, we had proposeda new design in inspecting pipelines. Themajor advantage is that it could be used in caseof pipe diameter variation with the simplemechanism. We developed a pipe inspectionrobot that can be applied to 140- 180mmpipeline. The kinematics of mechanism andactuator sizing of this robot have beeninvestigated. A real prototype was developedto test the feasibility of this robot for inspectionof in-house pipelines. We used a PCB boardthat can operate DC motor. Good conceptiveand element design could manage all theproblems. The types of inspection tasks arevery different. A modular design wasconsidered for PIC that can be easily adaptedto new environments with small changes.Presence of obstacles within the pipelines isa difficult issue. In the proposed mechanism

the problem is solved by a spring actuation andincreasing the flexibility of the mechanism. Thepropulsion of the robot has been successfullyconducted using only three motors, a radicalsimplification over existing efforts. The robot isdesigned to be able to traverse horizontal andvertical pipes. We had experimented our projectand we got the test results. Several types ofmodules for pipe inspection minirobot havebeen presented. Many of the design goals ofthe Pipe inspection robot have been completelyfulfilled.

REFERENCES1. Horodinca M, Dorftei I, Mignon E and

Preumont A (2002), “A Simple Architecturefor in Pipe Inspection Robots”, in Proc. Int.Colloq. Mobile, Autonomous Systems,pp. 61-64.

2. Jadran Lenari and Roth B (2006),Advances in Robot Kinematics:Mechanisms and Motion, 1st Edition.

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3. Mhramatsu M, Namiki N, Koyama U andSuga Y (2000), “Autonomous Mobile Robotin Pipe for Piping Operations”, in Proc.IEEE/RSJ Int. Conf. Intelligent Robots,Systems, Vol. 3.

5. Paul E Sandin (2003), Robot Mechanismsand Mechanical Devices, 1st Edition.

6. www.google.com

7. www.wikipedia.com

defect identification in pipe lines using pipe inspection ... · 20 int. j. mech. eng. & rob....

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