Mechanical accidents, fatigue, erosion, corrosion, as well as environmental attacks, are issues that can lead to a crack in a mechanical structure. Cracks are indications of an impending mechanical failure. In view of the fact that the presence of a crack in a structure could lead to devastating results, investigating the structural integrity of pipes was an extremely active area of research in the last two decades. Mechanical structures in real service life are subjected to combined or separate effects of the dynamic load, temperature and corrosive medium, due to the consequent growth of fatigue cracks, cracks due to corrosion and other type damages. Although the theory and technology of non-destructive testing is highly enhanced, inspecting the integrity of a structure is a labour-intensive and protracted process that should only be carried out when truly needed. One approach for reducing inspection related shutdown time and cost is to provide a mechanism with an early warning failure device. Such a device monitors, online, crack-related irregularity in the behaviour of a system. If the device gives a sound signal that a crack is present, a message is given out to the operator to shutdown the machine and have it checked. For the development of such early warning devices, knowledge of the dynamics of cracked structures is important.

1. SEMINAR PRESENTATION
ON
CRACK DETECTION IN PIPES
UNDER THE GUIDANCE OF
MR. A. V. DEOKAR
PRESENTED BY
AKANSHA JHA
DEPARTMENT OF MECHANICAL ENGINEERING
AMRUTVAHINI COLLEGE OF ENGINEERING, SANGAMNER
2011-2012

2. T.E MECHANICAL SEMINAR
MAIN POINTS TO BE DISCUSSED
INTRODUCTION
TYPES OF CRACK
CAUSES AND EFFECTS
METHODS OF CRACK DETECTION
NATURAL FREQUENCY BASED METHOD
CONCLUSION
BIBLIOGRAPHY
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INTRODUCTION TO CRACK
• Definition
 “Any deviation introduced to a structure, either
deliberately or unintentionally, which adversely affect the
performance of the system.”
 Damage Assessment
Four levels of damage assessment:
1. Determining the presence
2. Locating the damage
3. Quantifying the severity
4. Prediction of the remaining serviceability
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CAUSES OF CRACK EFFECTS OF CRACK
Mechanical Damage High production and
Material Defects maintenance Cost
Weld Cracks Leads to Catastrophic Failure
Incomplete Fusion Operational Problem
Incomplete Penetration Premature Failure
Fatigue Cracks Affects the Industrial
External Or Internal Corrosion Economic Growth.
Hydrogen Blistering
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5. T.E MECHANICAL SEMINAR
TYPES OF CRACK
1) Transverse cracks : Cracks perpendicular to the pipe axis are
known as “transverse cracks”
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6. T.E MECHANICAL SEMINAR
TYPES OF CRACK
2) Longitudinal cracks: Cracks parallel to the pipe axis are
known as “longitudinal cracks”.
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TYPES OF CRACK
3) Slant cracks: cracks at an angle to the pipe axis are known as “Slant
cracks”
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TYPES OF CRACK
4) Gaping cracks: Cracks that always remain open are known as “gaping
cracks” or “notches”.
5)Surface cracks: Cracks that open on the surface are called “surface
cracks”.
6)Subsurface cracks: Cracks that do not show on the surface are called
“subsurface cracks”.
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9. T.E MECHANICAL SEMINAR
METHODS OF CRACK DETECTION
 CONVENTIONAL METHODS :
(Non- Destructive techniques)
1. Pipeline injection gauze
2. Sewer scanner & evaluation technology
3. Automated pipe crack detection
4. Ultrasound acoustics based assessment technique
 NON-CONVENTIONAL METHOD :
• Natural Frequency
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CONVENTIONAL METHODS
1) Pipeline Injection Gauze(PIG) :‘Smart’ and Intelligent inline
inspection tools sent through the pipe via the circulation
of fluid.
Fully automatic
Data stored on solid state memories
Reliable in a hostile environment
Cannot be supervised during a run
The inspection speed depends on the medium
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11. T.E MECHANICAL SEMINAR
CONVENTIONAL METHODS
2) Sewer Scanner & Evaluation Technology(SSET) :
Technology for obtaining images of the interior of pipe
It can travel through the pipe at a uniform speed
Higher quality image data
Enables us to make critical rehabilitation decisions.
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12. T.E MECHANICAL SEMINAR
CONVENTIONAL METHODS
3) Automated Pipe Crack Detection :
Successfully able to detect cracks in varying pipe
backgrounds, colour, and crack patterns.
Better 2-D features from segmented crack images are available
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13. T.E MECHANICAL SEMINAR
NATURAL FREQUENCY AS BASIC CRITERION
 DATA OF UNCRACKED PIPE(l=900 mm, di=16 mm, do=21 mm
Analytical Experimental FE model
ω1 (Hz) 146.9 147.50 146.54
ω2 (Hz) 404.98 399.63 401.69
ω3 (Hz) 793.95 786.75 787.17
 EXPERIMENTAL DATA OF 1st PIPE(300 mm from one end for d=1
mm and d=2 mm)
Depth=1mm Depth=2mm
ω1 (Hz) 147.25 147.0
ω2 (Hz) 398.63 397.75
ω3 (Hz) 786.63 786.38
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14. T.E MECHANICAL SEMINAR
NATURAL FREQUENCY AS BASIC CRITERION
x-coordinate : Normalized
distance of the crack (x/l)
where, x= crack location
l=length of pipe
y-coordinate: Crack
dimensions(d/w)
where ,d= depth of crack
w=width of pipe
z-coordinate: Natural frequency
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NATURAL FREQUENCY AS BASIC CRITERION
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NATURAL FREQUENCY AS BASIC CRITERION
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NATURAL FREQUENCY AS BASIC CRITERION
 DATA OF UNCRACKED PIPE(l=650 mm, do =104.5 mm, di=112.5
mm
FE results Experimental
ω1 (Hz) 1084.2 1083.5
ω2 (Hz) 1413.0 1411.1
ω3 (Hz) 1659.4 1658.1
 EXPERIMENTAL DATA OF 2nd PIPE(325 mm from one end for
d=1.5 mm)
depth=1.5mm
ω1 (Hz) 1077.6
ω2 (Hz) 1412.0
ω3 (Hz) 1652.3
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NATURAL FREQUENCY AS BASIC CRITERION
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CONCLUSION:
 Significant changes in natural frequencies of the vibrating
pipes are observed at the vicinity of crack location.
 With the increase in crack depth, the natural frequency of
the pipe decreases
 The less is the wall thickness, less is the computational
effort
 This method is promising and can be used over a large-scale
,compared to other NDE techniques.
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20. T.E MECHANICAL SEMINAR
 “Material Science And Metallurgy”; V.D.Kodgire and S.V
Kodgire; Everest Publishing House; 25th Edition.
 “Crack Location In Pipes Using Modal Frequencies And Fem”;
M.J. Mahboob, A. Marzban and A.Shahsavri; The 11th
International Conference On Vibration Engineering, Timissoara,
Romania, 2005.
 “Crack Detection In Aluminum Structures”; Brad A. Butrym,
M.S. Thesis; Virginia Polytechnic Institute And State University;
2010.
 “Vibration Analysis Of Cracked Beam”; Prabhakar M.S, Thesis
Of M. Tech; National Institute Of Technology, Rourkela; 2009.
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QUESTIONS?
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THANK YOU
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