EPA/600/R-13/078 I December 2013 I www.epa.gov/research
United States
Environmental Protection
Agency
Evaluation of Opportunities to
Improve Structural Inspection
Capabilities for Water Mains: Large
Diameter Cast Iron Pipe
Office of Research and Development
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EPA/600/R-13/078
December 2013
Evaluation of Opportunities to Improve Structural
Inspection Capabilities for Water Mains: Large Diameter
Cast Iron Pipe
by
John Matthews, Ph.D., Bruce Nestleroth, Ph.D. and Wendy Condit, P.E.
Battelle Memorial Institute
and
James Thomson, C.Eng.
Independent Consultant
EPA Contract No. EP-C-05-057
Task Order No. 62
Michael D. Royer
Task Order Manager
Water Supply and Water Resources Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
2890 Woodbridge Avenue (MS-104)
Edison, NJ 08837
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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DISCLAIMER
The work reported in this document was funded by the U.S. Environmental Protection Agency (EPA),
through its Office of Research and Development, under Task Order (TO) 0062 of Contract No. EP-C-05-
057 to Battelle. It has been subjected to the Agency's peer and administrative review and has been
approved for publication as an EPA document. Any opinions expressed in this report are those of the
authors and do not, necessarily, reflect the official positions and policies of the EPA. Any mention of
trade names or commercial products does not constitute endorsement or recommendation for use by the
EPA. The quality of secondary data referenced in this document was not independently evaluated by
EPA and Battelle.
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ABSTRACT
The U.S. EPA and other organizations have projected that a large portion of the United States' aging
water conveyance infrastructure will reach the end of its service life in the next several decades. EPA
has identified asset management as a critical factor in efficiently addressing this projected surge in water
conveyance infrastructure renewal. An important tool in the asset manager's toolbox is cost-effective
structural inspection, since it provides data to help support optimized capital, operations, and maintenance
planning. However, there are many gaps in structural inspection capability and affordability, and many
options for addressing those gaps.
Recognizing the importance of structural inspection, and its shortcomings, as well as the many potential
options for its improvement, U.S. EPA's Office of Research and Development identified evaluation and
improvement of structural inspection technologies as an important component of its aging water
infrastructure research program. Selection of the most promising structural inspection technologies to
evaluate and/or improve is challenging due to the number of factors to be considered. This project
provides a protocol for screening innovative structural inspection concepts and technologies. The
protocol is focused on a single scenario ~ large diameter, cast iron water mains ~ because (a) it
substantially reduces the complexity of the decision protocol, (b) high consequence failures of this type
have already occurred and remain of concern for older cities; and (c) research by others has provided new
insights into the causes of these failures that enabled important pre-failure indicators to be identified and
quantified.
The initial target audience is EPA's aging water infrastructure research planning process. The protocol is
expected to be used as a guide for periodic reviews of the prospects of emerging structural inspection
technologies for large diameter cast iron water mains. Also, this protocol can potentially be utilized by
other organizations or individuals who are considering supporting or conducting water or wastewater pipe
structural inspection technology research. The protocol can potentially be modified to address other
high-interest pipe scenarios, such as large diameter ductile iron, pre-stressed concrete cylinder pipe
(PCCP), asbestos cement, and steel.
The protocol contains three levels and is used to evaluate eight technologies (four existing and four
emerging) to determine whether the protocol is implementable and produces reasonable results. The
report provides a brief overview of the potential failure modes, mechanism, and distress indicators for
high risk cast iron water mains. This report also briefly discusses structural inspection technologies and
the key stakeholders involved in structural inspection technology research and development.
The protocol guides information collection for proposed technology developments including: the potential
for inspection of water mains, the ability to detect specific anomalies or abnormal operating conditions,
the cost of the technology development, and the potential cost of utilization by water companies. The
application of these protocols was successful in demonstrating the potential of eight technologies, four of
which showed the potential for further development for detecting critical distress indicators in a relatively
cost-effective and reasonably implementable manner. The other four were considered to be inappropriate
for further development for use on large diameter, cast iron water mains.
in
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ACKNOWLEDGMENTS
The technical direction and coordination for this project was provided by Michael Royer of EPA's Urban
Watershed Management Branch. The project team would like to acknowledge the technical input of
several contributors to this report including Balvant Rajani and Yehuda Kleiner from the National
Research Council (NRC) of Canada; Frank Blaha from the Water Research Foundation (WaterRF); and
Walter Graf from the Water Environment Research Foundation (WERF). The authors would like to thank
the stakeholder group members (Frank Blaha of WaterRF, Walter Graf of WERF, and Yehuda Kleiner of
NRC Canada) for providing written comments.
This report includes an updated review of research on advances in structural inspection technologies for
cast iron water mains based on unpublished, comprehensive literature reviews conducted initially under
EPA Contract No. CWX089 entitled, Report on Evaluation of Opportunities to Improve Structural
Integrity Monitoring (SIM) Capabilities for Water Mains through Federal Research and Technology
Transfer, EPA STREAMS Contract No. EP-C-05-057, Task Order (TO) 62 sub-tasks entitled, Evaluation
of Opportunities to Improve Structural Integrity Monitoring (SIM) Capabilities for Water Mains, and
Critical Review of Recently Completed and Ongoing Water Main Condition Assessment Products and
Research.
IV
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EXECUTIVE SUMMARY
Introduction
The U.S. EPA and other organizations have projected that a large portion of the United States' aging
water conveyance infrastructure will reach the end of its service life in the next several decades. EPA
has identified asset management as a critical factor in efficiently addressing this projected surge in water
conveyance infrastructure renewal. An important tool in the asset manager's toolbox is cost-effective
structural inspection, since it provides data to help support optimized capital, operations, and maintenance
planning. However, there are many gaps in structural inspection capability and affordability, and many
options for addressing those gaps.
Recognizing the importance of structural inspection, and its shortcomings, as well as the many potential
options for its improvement, U.S. EPA's Office of Research and Development identified evaluation and
improvement of structural inspection technologies as an important component of its aging water
infrastructure research program. Selection of the most promising structural inspection technologies to
evaluate and/or improve is challenging due to the number of factors to be considered. This project
provides a protocol for screening innovative structural inspection concepts and technologies. The
protocol is focused on a single scenario ~ large diameter, cast iron water mains ~ because (a) it
substantially reduces the complexity of the decision protocol, (b) high consequence failures of this type
have already occurred and remain of concern for older cities; and (c) research by others has provided new
insights into the causes of these failures that enabled important pre-failure indicators to be identified and
quantified.
The initial target audience is EPA's aging water infrastructure research planning process. The protocol is
expected to be used as a guide for periodic reviews of the prospects of emerging structural inspection
technologies for large diameter cast iron water mains. Also, this protocol can potentially be utilized by
other organizations or individuals who are considering supporting or conducting water or wastewater pipe
structural inspection technology research. The protocol can potentially be modified to address other
high-interest pipe scenarios, such as large diameter ductile iron, pre-stressed concrete cylinder pipe
(PCCP), asbestos cement, and steel.
Characterization of Potential High Risk, Cast Iron Water Mains
The structural deterioration and failure pattern of high-risk, large diameter cast iron pipes is complex due
to factors such as the heterogeneous nature of cast iron, variability of handling and installation, and
differing soil properties along the line. Despite these complexities, structural inspection can be an
important component in estimating the current and future condition of cast iron pipe. Some failure
mechanisms have potentially reliable measurable distress indicators; therefore, it is reasonable to expect
that if monitored, these indicators could help determine if failure may be imminent or if an asset can
operate longer before failure.
The most common failure modes and mechanisms for large diameter cast iron pipe are: longitudinal
fractures, circular fractures, mixed fractures, bell splitting, and corrosion. Longitudinal cracking is more
common in large diameter pipes and can take various forms such as vertical cracks and slanted cracks
across the pipe wall. Circular cracking is the most common failure mode for small diameter pipes,
although there are cases recorded in large diameters. Mixed fractures can be either tensile hoop failures
in combination with bending or shattering due to the annealing process. Bell splitting is due to
longitudinal cracks at the bell end or bell shards. Corrosion in the form of pitting and/or graphitization is
a common but not exclusive factor in most pipe failures.
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Factors that could potentially contribute to failure include physical (e.g., pipe age, thickness, and vintage);
environmental (e.g., pipe bedding, soil type, and climate); and operational factors (e.g., internal water
pressure, transient pressure, and leakage). Measurable distress indicators that are the result of these
factors include: external coating defects, pipe barrel and bell wall thickness, graphitization, and cracks;
internal lining spalling; tuberculation; change in joint alignment; and joint displacement. Inferential
indicators (e.g., pipe vintage, pressure variations, and pipe location) can point to the potential existence of
a pipe deterioration mechanism, but they do not provide direct evidence of structural distress.
Structural Inspection Components and Systems
To successfully monitor structural condition, a combination of screening, monitoring, and condition
assessment techniques needs to be used. External condition assessment tools, which provide detailed
condition information for selected locations along the pipe, include corrosion pit depth measurements;
ultrasonic tools for measuring remaining pipe wall thickness; magnetic flux leakage (MFL) technology
for detection of graphitization and cracks on the exterior of pipe walls; and broadband electromagnetic
technology for detecting wall loss.
Inline inspection technologies include closed circuit television (CCTV) visual tools to inspect for cracks;
remote field technology tools to detect loss of wall thickness; and acoustic leak detection tools. Issues
that must be overcome for wide-spread use of inline inspection technologies for water mains include the
lack of launching and receiving facilities on existing water mains and the expense of conducting the
inspections. Other leak detection technologies can also be applied externally and do not require internal
access to the main.
Key stakeholders involved in structural inspection technology research and development include: federal
agencies (i.e., U.S. Environmental Protection Agency [EPA], U.S. Department of Transportation[DOT],
U.S. Department of Energy [DOE], U.S. Department of Commerce/National Institute for Standards and
Technology [NIST], National Science Foundation [NSF], etc.); non-profit organizations (e.g., Water
Research Foundation [WaterRF], Water Environment Research Foundation [WERF], etc.) and private
technology developers. These agencies and organizations would be the users of the protocol developed in
this report, which would serve as a guide for the screening and identification of emerging technologies
that could be evaluated for their suitability to large diameter cast iron water mains.
Protocol Development
The screening protocol is a three step process designed to assist EPA or other research funding
organizations to strategically evaluate the feasibility of emerging structural inspection technologies for
use on large diameter cast iron mains. The first screening protocol collects the data needed to enable a
user to determine if an inspection technology can be practically implemented on a large diameter cast iron
water main. After determining the intended capabilities of the tool, the user is led through a series of
flowcharts to determine how the tool is implemented (i.e., internal, external, from above ground, or the
air); what the requirements are for implementation; and the technology is given an implementation grade
(i.e., easy, moderate, or difficult) based on the user's answers.
The second screening protocol collects the data to enable a user to determine the degradation condition or
conditions that an inspection technology can detect and determines if the technology locates the key
distress indicators for large diameter cast iron water mains. First, the protocol is used to determine what
types of defects the tool is intended to detect (i.e., degradation conditions such as corrosion and leaks;
condition that could lead to failure such as pipe angle at the joints; etc.) and to what degree the tool can
detect them. Then the technology is given a cost-to-implement grade based on the current costs of the
system and the needed cost for further development. The third and final screening protocol determines
how a structural inspection technology compares to existing technologies and whether it is recommended
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for further development. Input from the first protocol about the types and degrees of defects the tool can
detect are used, along with implementation and cost grades to determine if the proposed technology has
the potential for further development.
Application of Protocols
To validate and calibrate the protocol, eight example applications using existing and emerging
technologies were conducted. Two remote field eddy current based technologies, which are used to
detect wall corrosion internally, were evaluated with one showing the potential for further development,
while the other approach was considered inappropriate for further development due to the cost to
implement. The two internal leak detection technologies both showed potential for further development,
and currently both are being designed for use on large diameter cast iron mains. Two technologies
designed for aboveground use to measure wall corrosion were also evaluated with one showing the
potential for further development, while the second was considered inapplicable due its need for
continuous electrical conductivity. The final two technologies were MFL technologies used to detect wall
corrosion internally, but each was considered inappropriate for further development due to their difficult
implementation and high costs.
Conclusions and Recommendations
The screening protocols developed for this report can help to guide EPA or other funding agencies in
evaluating the potential applicability of proposed structural inspection technologies for use with high-risk,
large diameter cast iron water mains, which can be very costly when they fail and when they are replaced.
The protocols collect information for proposed technology developments including: the potential for
inspection of water mains, the ability to detect specific anomalies or abnormal operating conditions, the
cost of the technology development, and the potential cost of utilization by water companies. The
application of these protocols was successful in demonstrating the potential of eight technologies, four of
which showed the potential for further development for detecting critical distress indicators in a relatively
cost-effective and reasonably implementable manner. The other four were considered to be inappropriate
for further development for use on large diameter cast iron water mains.
It is recommended that EPA or other funding agencies interested in supporting the evaluation and
improvement of structural inspection technologies use these protocols as a screening measure to
determine if a proposed technology is applicable to large diameter cast iron water mains, capable of
detecting key distress indicators, and implementable at a reasonable cost. This methodology was
developed for large diameter cast iron mains as an example and can be expanded to small diameter mains
and other pipe types.
It is also recommended that screening protocols be developed for other potentially high-risk mains such
as large diameter ductile iron, prestressed concrete cylinder pipe (PCCP), asbestos cement, and steel.
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TABLE OF CONTENTS
DISCLAIMER ii
ABSTRACT iii
ACKNOWLEDGMENTS iv
EXECUTIVE SUMMARY v
TABLE OF CONTENTS viii
FIGURES x
TABLES xi
ABBREVIATIONS AND ACRONYMS xii
1.0: INTRODUCTION 1
1.1 Project Background 1
1.2 Project Objectives 1
1.3 Organization of the Report 2
2.0: CHARACTERIZATION OF POTENTIAL HIGH RISK, CAST IRON WATER MAINS 3
2.1 Background 3
2.2 Overview of Cast Iron Pipe 3
2.2.1 Horizontally Cast Pipes Using Sand Molds 3
2.2.2 Vertically Cast Pipes Using Sand Molds 4
2.2.3 Horizontally Spun Cast Pipe Using Metal Molds 4
2.2.4 Horizontally Spun Cast Pipe Using Sand Molds 4
2.2.5 Joints in Cast Iron Pipes 4
2.3 Failure Modes and Mechanisms 4
2.3.1 Longitudinal Split Fracture 6
2.3.2 Circular Fracture 7
2.3.3 Mixed Fracture 8
2.3.4 Bell Splitting 8
2.3.5 Corrosion 8
2.4 Potential Contributory Factors to Failure 9
2.4.1 Physical Factors 9
2.4.1.1 Pipe Age, Material, and Manufacture 9
2.4.1.2 Pipe Wall Thickness and Vintage 11
2.4.1.3 Pipe Diameter 11
2.4.1.4 Type of Joints 12
2.4.1.5 Pipe Lining and Coating 13
2.4.1.6 Pipe Installation 13
2.4.1.7 Other Physical Factors 13
2.4.2 Environmental Factors 13
2.4.2.1 Pipe Bedding and Backfill 13
2.4.2.2 Soil and Groundwater 13
2.4.2.3 Galvanic Corrosion 14
2.4.2.4 Stray Electric Currents 14
2.4.2.5 Microbiologically Influenced Corrosion 14
2.4.2.6 Soil Movement and Disturbances 14
2.4.2.7 Climate 15
2.4.3 Operational Factors 15
2.4.3.1 Hydraulic Factors 15
2.4.3.2 Leakage 15
2.4.3.3 Other Operational Factors 15
2.5 Condition Assessment - Distress and Inferential Indicators 15
2.5.1 Distress Indicators for Cast Iron Pipe 15
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2.5.2 Inferential Indicators for Cast Iron Pipes 17
SECTION 3.0: STRUCTURAL INSPECTION COMPONENTS AND SYSTEMS 18
3.1 Overview 18
3.2 Available Inspection and Monitoring Technologies 18
3.2.1 External Inspection Technology Description 18
3.2.2 Internal Inspection Technology Description 19
3.2.3 Leak Detection Technology Description 20
3.2.4 Summary 20
3.3 Structural Inspection Technology Research Applicable to Cast Iron Water Mains 20
4.0: PROTOCOL DEVELOPMENT 23
4.1 Basic Screening Protocol 23
4.2 Secondary Screening Protocol 32
4.3 Tertiary Screening Protocol 42
4.4 Protocol Summary 54
5.0: APPLICATION OF PROTOCOLS 55
5.1 Overview 55
5.2 Tethered Remote Field Eddy Current 55
5.3 Robotic RFEC 56
5.4 Free Swimming Acoustics 58
5.5 Flexible Rod Sensor 59
5.6 Magnetic Tomography 60
5.7 Multi-Frequency Field Variation 61
5.8 MFL Inline Free Swimming Pig 61
5.9 Tethered MFL 63
5.10 Application Summary 64
6.0: CONCLUSIONS and recommendations 65
6.1 Summary 65
6.2 Recommendations 65
7.0: REFERENCES 66
APPENDIX A 1
ORGANIZATIONS FUNDING STRUCTURAL INSPECTION RESEARCH 2
A.I U.S. Environmental Protection Agency 2
A.2 U.S. Department of Transportation 2
A.3 U.S. Department of Energy 2
A.4 U.S. Department of Defense 2
A.5 U.S. Department of Commerce 3
A.6 U.S. Department of Homeland Security 3
A.7 U.S. Department of the Interior 3
A.8 National Science Foundation 3
A.9 National Aeronautics and Space Administration 3
A. 10 Water Research Foundation 4
A. 11 Water Environment Research Foundation 4
A. 12 Gas Technology Institute 4
A. 13 Industrial Research 4
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FIGURES
Figure 2-1. Longitudinal Fracture: Vertical Crack (left), Dip Slip (center), and Reverse Slip (right) 7
Figure 2-2. Graph of Failures Modes to Diameter (UKWIR) 8
Figure 2-3. Typical Stress vs. Strain Relationship for Cast Iron and Ductile Iron 11
Figure 2-4. Typical Bell-Spigot Joint Configuration 12
Figure 4-1. First Step of Basic Screening Protocol, Determine Technology Capabilities 24
Figure 4-2. Primary Technology Categories 25
Figure 4-3. Required Internal Condition 26
Figure 4-4. Installation Conditions 26
Figure 4-5. Permanently Installed 27
Figure 4-6. Required External Condition 29
Figure 4-7. Excavation Requirements 29
Figure 4-8. Above Ground Implementation 31
Figure 4-9. From the Air Implementation 31
Figure 4-10. Defect Detection Categories 32
Figure 4-11. Degradation Defect Categories 33
Figure 4-12. Corrosion Detection in the Pipe Barrel 33
Figure 4-13. Corrosion Detection in the Bell 34
Figure 4-14. Leak Detection 34
Figure 4-15. Conditions Leading to Degradation or Failure 35
Figure 4-16. Pipe Angle Between at the Bell and Spigot 35
Figure 4-17. Defects in the Internal Coating 36
Figure 4-18. Defects in the External Coating 36
Figure 4-19. Inferential Indicators of Higher Probability of Failure 37
Figure 4-20. Determines Pipe Vintage 38
Figure 4-21. Measures and Assesses Water Pressure Variations 38
Figure 4-22. Assesses Location Issues 39
Figure 4-23. Assesses Soil Issues 39
Figure 4-24. Assesses Cathodic Protection and Stray Currents 40
Figure 4-25. Key Defect Categories 42
Figure 4-26. Detecting Barrel Corrosion 43
Figure 4-27. Potential for Detecting Barrel Corrosion from Above Ground 43
Figure 4-28. Potential for Detecting Barrel Corrosion on an Exposed Pipe 44
Figure 4-29. Potential for Detecting Barrel Corrosion with a Permanently Installed Internal Device 44
Figure 4-30. Potential for Detecting Barrel Corrosion with a Temporarily Installed Internal Device 45
Figure 4-31. Detecting Bell Corrosion and Cracks 45
Figure 4-32. Potential for Detecting Bell Defects from Above Ground 46
Figure 4-33. Potential for Detecting Bell Defects on an Exposed Pipe 46
Figure 4-34. Potential for Detecting Bell Defects with a Permanently Installed Internal Device 47
Figure 4-35. Potential for Detecting Bell Defects with a Temporarily Installed Internal Device 47
Figure 4-36. Detecting Leaks 48
Figure 4-37. Potential for Detecting Leaks from Above Ground 48
Figure 4-38. Potential for Detecting Leaks on an Exposed Pipe 49
Figure 4-39. Potential for Detecting Leaks with a Permanently Installed Internal Device 49
Figure 4-40. Potential for Detecting Leaks with a Temporarily Installed Internal Device 50
Figure 4-41. Detecting Pipe Angle 50
Figure 4-42. Potential for Detecting Pipe Angle from Above Ground 51
Figure 4-43. Potential for Detecting Pipe Angle on an Exposed Pipe 51
Figure 4-44. Potential for Detecting Pipe Angle with a Permanently Installed Internal Device 51
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Figure 4-45. Potential for Detecting Pipe Angle with a Temporarily Installed Internal Device 52
Figure 4-46. Detecting Coating Defects 52
Figure 4-47. Potential for Detecting Internal Coating Defects 53
Figure 4-48. Potential for Detecting External Coating Defects 53
Figure 4-49. Potential for Detecting Inferential Indicators of Failure 53
TABLES
Table 2-1. Longitudinal and Circumferential Breakage Patterns in Large Diameter Mains 5
Table 2-2. Mixed Fracture and Bell Split Breakage Patterns in Large Diameter Mains 6
Table 2-3. Percentage of Failures by Mode for Iron Pipe (< 15 in.) 7
Table 2-4. Factors Contributing to Water System Deterioration 9
Table 2-5. Changing Wall Thickness for a36-in. Pipe Operating at 150 psi 11
Table 2-6. Failures per km/yr. by Diameter 12
Table 2-7. Soil Types and Impact on Structural Defects 14
Table 2-8. Distress Indicators that Influence Pipe Condition for Cast Iron Pipes 16
Table 2-9. Inferential Indicators for Cast Iron Pipes 17
Table 3 -1. Tools and Technologies for Inspecting Structural Integrity Externally 19
Table 3 -2. Tools and Technologies for Inspecting Structural Integrity Internally 19
Table 3-3. Tools and Technologies for Leak Inspection 20
Table 3-4. Available Inspection and Monitoring Technologies Applicable to Cast Iron Mains 21
Table 3-5. Organizations Funding Structural Inspection Research Potentially Relevant to Water 22
Table 4-1. Inline Applicability Grade Card 29
Table 4-2. External Applicability Grade Card 30
Table 4-3. Cost Grade Card 41
Table 5-1. Inline Applicability Grade Card for Tethered RFEC 56
Table 5-2. Cost Grade Card for Tethered RFEC 56
Table 5-3. Inline Applicability Grade Card for Robotic RFEC 57
Table 5-4. Cost Grade Card for Robotic RFEC 57
Table 5-5. Inline Applicability Grade Card for FSA 58
Table 5-6. Cost Grade Card for FSA 59
Table 5-7. Inline Applicability Grade Card for FRS 59
Table 5-8. Cost Grade Card for FRS 60
Table 5-9. Cost Grade Card for MTM 61
Table 5-10. Inline Applicability Grade Card for Inline MFL 62
Table 5-11. Cost Grade Card for Inline MFL 62
Table 5-12. Inline Applicability Grade Card for Tethered MFL 63
Table 5-13. Cost Grade Card for Tethered MFL 63
Table 5-14. Summary of Protocol Application 64
XI
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ABBREVIATIONS AND ACRONYMS
AC alternating current
AWWA American Water Works Association
AWWARF American Water Works Association Research Foundation
BEM broadband electromagnetic
BOEMRE Bureau of Ocean Energy Management, Regulation, and Enforcement
CCTV closed circuit television
CEIT Center for Environmental Industry & Technology
CERL Construction Engineering Research Laboratory
CI cast iron
CIPRA Cast Iron Pipe Research Association
CWA Clean Water Act
DHS U.S. Department of Homeland Security
DIPRA Ductile Iron Pipe Research Association
DOC U.S. Department of Commerce
DOD U.S. Department of Defense
DOE U.S. Department of Energy
DOI U.S. Department of the Interior
DOT U.S. Department of Transportation
EPA U.S. Environmental Protection Agency
ESTCP Environmental Security Technology Certification Program
ETV Environmental Technology Verification
FRS flexible rod sensor
FSA free swimming acoustic
GTI Gas Technology Institute
IRC Institution for Research in Construction
ITSC International Science and Technology Center
LaRC Langley Research Center
MFFV multi-frequency field variation
MFL magnetic flux leakage
MIC microbiologically influenced corrosion
MTM magnetic tomography
NASA National Aeronautics and Space Administration
NCER National Center for Environmental Research
NDE nondestructive evaluation
NETL National Energy Technology Laboratory
NIST National Institute of Standards and Technology
NRC National Research Council
NREC National Robotics Engineering Center
NRMRL National Risk Management Research Laboratory
xii
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NSF National Science Foundation
NTIAC Nondestructive Testing, Information, and Analysis Center
OP operating pressure
OPS Office of Pipeline Safety
ORD Office of Research and Development
PRCI Pipeline Research Council International
R&D research and development
RDT&E Research, Development, Test & Evaluation
RFEC remote filed eddy current
RFT remote field technology
S&T Science and Technology Directorate
SAM Strategic Asset Management
SBIR Small Business Innovation Research
SDWA Safe Drinking Water Act
SERDP Strategic Environmental Research and Development Program
SRB sulfate reducing bacteria
STAR Science to Achieve Results
TA&R Technology Assessment & Research
TIP Technology Innovation Program
TO Task Order
USAGE U.S. Army Corps of Engineers
UKWIR UK Water Industry Research
WaterRF Water Research Foundation
WERF Water Environment Research Foundation
WSWRD Water Supply and Water Resources Division
xni
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1.0: INTRODUCTION
1.1 Project Background
Cost-effective structural inspection can be an important component of effective condition assessment and
asset management of water conveyance infrastructure. Structural inspection involves collecting data
about meta-stable and/or transient indicators of the condition of the pipe. The data are used as inputs for
estimating the current and future condition of the pipe.
Cost-effective structural inspection can provide value to utilities in three primary ways. First, it can help
the utility prevent catastrophic failures in their deteriorating water mains, which they cannot afford to
replace at present. Secondly, it can help the utility reduce the amount perceived to need replacement,
which may enable them to replace only the pipes that are structurally deteriorated to the point that their
probability of failure is unacceptable. Finally, it may help the utility reduce the rate of deterioration of its
aging water mains. This could enable the utility to more promptly identify pipes that are deteriorating at
an accelerated rate, which could lead the utility to mitigate the conditions causing accelerated
deterioration with action (e.g., leak repair, retrofit cathodic protection, and/or spot rehabilitation).
These benefits provided by structural inspection technologies are important for utilities that must
strategically select water mains for replacement since they cannot afford to replace their entire aging
infrastructure. No references are readily available outlining how much utilities would be willing to pay
for condition assessment versus replacing costs, but rehabilitation and maintenance activities are typically
cheaper than replacement and can extend the asset life for years before replacement is needed (Baird,
2010).
These technologies can be improved by identifying failure modes and indicators; improving technology
performance (e.g., efficiency of detecting critical flaws; better spatial, temporal, and indicator coverage);
and reducing cost (e.g., mobilization/demobilization; pipe preparation/access; data collection; data
analysis; speed; and share cost [i.e., use same data or platform or data transmission system]). Scientific
and engineering research is being conducted to develop and improve these technologies and to accelerate
commercial implementation; portions of the development work are funded in part by government and
industry associations. Unfortunately, some developments are unsuccessful because they are not feasible
for water pipelines, do not properly address the structural integrity issue, or are not as cost effective as
competing structural inspection methods.
This report presents a protocol to assist research funding organizations, such as the U.S. Environmental
Protection Agency (EPA), in strategically evaluating the feasibility of emerging structural inspection
technologies for large diameter cast iron (CI) mains. This technology evaluation protocol could be used
as a guide for periodic expert panel reviews of the prospects for proposed innovations to pipe inspection
technologies. There is additional benefit from operating the evaluation protocol on potential technology
transfer opportunities from other industries, and innovative technologies from small businesses and
university research and development.
1.2 Project Objectives
The objective of this work was to develop a targeted, sound, and easy to use screening protocol for
evaluation of structural inspection technologies that are used to provide data that can support estimates of
current and future structural condition of water mains. These estimates can be used to help optimize
decisions about inspection, rehabilitation, and replacement of water mains. The value of optimal renewal
decision making arises from (1) safely utilizing installed infrastructure to its full life, (2) reduction of
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main break failures and their adverse health, safety, environmental, and economic effects, and (3) prompt
recognition and correction of significant leakage or deterioration.
The screening protocol developed focuses on large diameter, cast iron water mains. The screening
protocol evaluated the feasibility for further development of structural inspection technologies that could
be used to cost effectively prevent catastrophic failures, reduce the amount of pipe that needs to be
replaced, and/or reduce the rate of deterioration. The protocol contains three levels and was used to
evaluate eight technologies consisting of existing and emerging technologies to see whether the protocol
is implementable and produces reasonable results.
This report was developed based on EPA Quality Assurance Project Plan (QAPP) requirements set out in
EPA (2001). The quality of the secondary data reported in this document was not independently
evaluated by EPA and Battelle.
1.3 Organization of the Report
The first section of the report, Section 2.0, provides consolidated information on potential failure modes
and damage indicators for large diameter cast iron mains that could guide the development of new
inspection technologies. Section 3.0 presents a brief overview of the various structural inspection
technology components for cast iron pipe. The details of the specific technologies are available in the
references. Section 4.0 presents the three part protocol. The first protocol is a basic screening protocol to
answer whether the technology is feasible for water pipelines. The result of the evaluation is pass/fail.
The second screening protocol produces ratings on how well the structural inspection technology will
perform in water pipelines and how well it locates defects that will grow to failure and potential
conditions that are associated with failures (indicators). The third screening protocol determines how the
new structural inspection technology compares to existing technologies. Section 5.0 discusses the testing
of the protocol on eight technologies that are commercial, under development or available from other
industries. Section 6.0 summarizes key findings and provides recommendations for future research.
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2.0: CHARACTERIZATION OF POTENTIAL HIGH RISK, CAST IRON WATER MAINS
2.1 Background
The first cast iron water pipes in the U.S. were installed in Philadelphia in 1804 and many cast iron water
pipes in the U.S. have been in continuous operation for over 100 years. An American Water Works
Association (AWWA) survey of 337 water utilities determined that about 35% of the U.S. water pipe
network was laid with cast iron pipes made up of approximately 18% unlined and 17% lined (AWWA,
2004;U.S. EPA, 2009 ). Out of approximately 900,000 miles of water pipe in the U.S., it is estimated
that 315,000 miles is cast iron.
The structural deterioration and subsequent failure of cast iron water mains is a complex process
involving numerous factors both physical and dynamic. Particularly for large diameter cast iron pipes,
the pattern of failure (discussed in Section 2.3) may be complex due to factors such as the heterogeneous
nature of cast iron, variability of handling and installation, and differing soil properties along the line. A
number of physical and dynamic factors such as mechanical strength, loadings, and corrosion rates cannot
be precisely defined for each situation. These uncertainties and combinations of factors that create failure
make any condition assessment of the remaining life complex. Research has suggested that many failures
occur as a series of multiple events rather than a single event (Makar, 2000).
Despite these complexities, effective structural inspection can be an important component in estimating
the current and future condition of water mains. Some large diameter cast iron failure mechanisms have
potentially critical and reliable measurable distress indicators (e.g., corrosion, graphitization, cracks,
leakage, and angled pipe joints) and inferential indicators (e.g., pipe vintage, pressure variations, pipe
location, and soil issues), although the critical values that must be measured for each indicator may not be
known. Therefore, it is reasonable to expect that reliable condition indicators, if monitored and measured
accurately, can help determine if failure is imminent or if an asset can operate for longer before failure.
It is worth noting that a particular inspection technology is only going to be useful for the indicators that it
is designed to detect and the failure modes associated with that indicator. It may take a combination of
technologies to obtain the desired level of warning. This report focuses on large diameter cast iron mains,
defined as 16 in. diameter or greater. These are nearly exclusively transmission mains; fire hydrants and
connections are not normally found on such pipes.
2.2 Overview of Cast Iron Pipe
In the early nineteenth century, the first cast iron pipes in the U.S. were imported from England and
Scotland. In 1819, the City of Philadelphia installed a 16 in. diameter water main manufactured at
Weymouth, New Jersey. It was not until around 1830 that local production became more widely
established. Casting of pipes, boilers, and other items was undertaken in many local foundries around the
U.S. with variations in quality. Four techniques were employed in the casting of iron pipe (Stanton
Ironworks, 1936; CIPRA, 1927) and are briefly described below.
2.2.1 Horizontally Cast Pipes Using Sand Molds. Prior to 1850, the pipes were cast horizontally
using an inner core and outer mold. The outer mold was in two halves and formed from moist green sand
to form the outer pipe diameter. The inner core forming the internal bore was formed from baked sand
reinforced with iron rods. The space between molds was filled with molten iron. The length of pipes was
limited to a few feet because of the sagging of the inner core. It was difficult to place the cores
concentrically and a tendency to float led to non-uniform wall thickness. Another problem with
horizontal casting was the tendency for scum and air bubbles to float to the top of the pipe, which created
an area of weakness.
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2.2.2 Vertically Cast Pipes Using Sand Molds. From around the 1850s, vertical casting became
the method most commonly used for pipe production allowing longer pipe sections to be cast. Sections
up to 16 ft for diameters less than 12 in. and 8 to 12 ft for larger diameters could be cast, although by
1927 lengths up to 16 ft were produced.
These pipes were cast in vertical pits. The outer mold was formed from damp sand rammed around an
inner metal casing. The casing was withdrawn and the sand baked to form the outer mold. The inner core
was formed from sand and clay packed into an inner cylinder and also baked. The outer and inner cores
were assembled vertically in the pit and molten iron was poured into the annular space. Originally the
pipe bells were formed at the top of the pit, but from around 1914, casting the bell at the bottom was
introduced and over a period of time became standard practice. This obviated the weakening of bells due
to accumulation of scum and air bubbles in the top of the mold.
A characteristic of cast pipes is a lower fracture toughness and mechanical strength that arises from larger
graphite flakes than spun cast iron pipes, which act as crack initiator sites. This is particularly a problem
in larger pipes where the slow cooling promoted flake growth.
2.2.3 Horizontally Spun Cast Pipe Using Metal Molds. The de Lavaud technique developed in
Brazil in 1915 was licensed to companies in the U.S. in the early 1920s. The method was a great
improvement in that casting defects were greatly reduced and pipe with consistent uniform wall thickness
was produced. The system was based on pouring molten iron into a metal mold and spinning at high
speed to create uniform wall thickness. The rotating mold was dipped into cold water to cool it. This
caused the exterior surface of the pipe to be hardened by direct crystallization, which was then softened
by heat annealing treatment. Annealing was a difficult process for larger diameters as they had to be
rolled onto skids when still at temperatures of 900°C, which could lead to hairline cracking.
2.2.4 Horizontally Spun Cast Pipe Using Sand Molds. This process, introduced in 1925, was
based on using dry sand molds which obviated the need for heat annealing as the porous sand allowed for
ventilation and cooling. Both spun systems allowed pipe lengths up to 20 ft to be produced. From around
the 1850s, pipes were dipped in a Dr. Angus Smith coal-tar oil solution while hot to coat the internal and
external surfaces. They were also pressure tested and hammer tapped to detect cracks. Cement lining
was first applied to cast iron mains in Charleston in 1921 (CIPRA, 1927).
It cannot be assumed that cast iron pipes will have the mechanical strength as required by the standards in
use at the time of their installation. Tests (Kleiner and Rajani, 2000) have shown strengths ranging from
33 MPa to 231 MPa (6,600 to 34,000 psi). There are likely to be wide variations even from the same pipe
due to the changing distribution of graphite flakes and casting flaws.
2.2.5 Joints in Cast Iron Pipes. The bell and spigot joint system has found general use in all
forms of cast iron pipes. The joint was first made by caulking yarn or hemp into the space between the
bell and spigot and then pouring molten lead and caulking using hammers and caulking tools into the
remaining space. An alternative jointing material was "leadite" which was introduced initially around
1900 (Rajani and Kleiner, In Press 2013). Leadite is a mixture of iron, sulfur, slag, and salt, which is
heated and becomes a vitreous mass when cooled. Leadite had advantages in that it melts at 121°C
compared to lead at 322°C and does not have to be caulked. The use of a compressible flexible gasket
was introduced in the late 1950s for a push-on joint, with rubber being one of the widely used materials.
2.3 Failure Modes and Mechanisms
Failure in pipes is defined here as a condition caused by collapse, break, or bending, so that a structure or
structural element can no longer fulfill its purpose. Other definitions include failures where relatively
small amounts of water are lost from defective joints. Failure occurs when the pipe is weakened by
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corrosion or other defects to an extent when it can no longer resist the imposed stresses. Failure modes,
as described in this section based on Rajani and Kleiner (In Press 2013), are the manner in which a cast
iron pipe fails and the mechanisms that cause failure.
Smaller diameter pipes generally have smaller moments of inertia making them more susceptible to
longitudinal bending failures. Larger diameter pipes have greater moments of inertia which creates a
tendency to longitudinal cracking and shearing at the bell. For pipes less than 16-in. in diameter, both the
length of pipe and the break frequency are much greater than pipes with larger diameters. Although a
number of utilities record failures, there is a dearth of detailed records on the frequency and mode of large
diameter pipe failures.
The National Research Council (NRC) of Canada has undertaken detailed investigations of failures in the
U.S., UK, and Canada (Rajani and Kleiner, In Press 2013; Makar et al., 2001; Makar, 2001) as has the
University of Toronto (Seica et al., 2002). These reports include useful recommendations on the
examination of failures of cast iron mains. Reference to these findings is included in the following
discussion of failure modes and mechanisms. Tables 2-1 and 2-2 outline the failure modes and
mechanisms (Rajani and Kleiner, In Press 2013).
Table 2-1. Longitudinal and Circumferential Breakage Patterns in Large Diameter Mains
Breakage Pattern Principal Stress
Location
Possible Cause/Comment
Vertical crack(s) across pipe wall thickness.
• Pull apart - crack Tensile (hoop)
with no movement.
§5 Slanted crack(s) across pipe wall thickness.
a • Dip slip - vertical Tensile (hoop)
'•3 movement.
'Bo • Reverse slip - Compression
^ vertical movement.
At spring line (3 or 9 o'clock) if
backfill (dense soil) provides
good support. At any of 12, 3, 6,
9 o'clock positions if backfill
(loose) provide poor support.
Crack position would also depend
on location of defects or
inclusions (weakest link).
Previously initiated crack
that eventually propagates
along pipe length. If crack
remains open, significant
residual stresses were
present
Crack initiates through
presence of defect, void or
inclusion that eventually
propagates longitudinally.
Direction of the dip helps
establish if failure
movement is dip or reverse
slip.
«
§
U
Crack(s) at the
invert, spring line or
crown.
Crack(s) across the
whole pipe
circumference.
Tensile
(longitudinal)
Tensile
(longitudinal)
Crack initiates at invert if poor
bedding is present or soil support
is lost and propagates towards the
spring line in circumferential
direction.
Not usually observed in
large diameter pipes.
Rajani and Kleiner, In Press 2013.
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Table 2-2. Mixed
Breakage Pattern
Principal crack is
longitudinal with
arc(s) formed at each
end of crack;
occasionally
transforms into a
^ spiral crack.
u
sS
•a
0)
1
Shattered into
multiple pieces of
broken pipe.
Longitudinal crack at
bell end.
_*-
"3.
s
(S5
_Se// shard.
Fracture and Bell Split Breakage Patterns in Large
Principal Stress Location
Tensile (hoop) +
bending (arc end) r~3*Cr~~r——
Crack initiates at midpoint of
crack and propagates on either or
both directions. Subsequently,
earth loads come into action
causing a bending (flap failure).
Tensile (hoop) + , — ______
residual ^--O§3 ' — — &~\
^~"V-^
Tensile (hoop)
^_______
C^^ ~~-srr-\
^^^^ ~^N\\
^^^Qvy
^vy
Tensile (hoop + / _______
flexural) V^_^ "~~~~~~V/~\
^^^^^ yrjl
^^J/
Diameter Mains
Possible Cause/Comment
Initiates as indicated for
longitudinal split and
propagates in direction
where soil offers little or
no support.
External restraint or
boundary conditions play a
major role on how the
crack changes direction to
dissipate energy.
Multiple cracks with
fallout of pieces occur in
pipes with annealing
treatment (spun cast with
metal molds).
Crack introduced by
wedge action when lead
caulked (hammered) into
place or excessive
hammering action.
Subsequently propagates
with time with stress
fluctuation caused by
variations in pressure.
Reaction caused by spigot
on the bell as result of
settlement of barrel part of
pipe.
Rajani and Kleiner, In Press 2013.
2.3.1 Longitudinal Split Fracture. Longitudinal cracking is typically more common in large
diameter pipes. The failure mechanism shown in Figure 2-1 (Rajani and Kleiner, In Press 2013) can take
various forms:
• A vertical crack across the pipe wall thickness due to tensile hoop stress
• A slanted crack across pipe wall thickness which takes two forms:
o A dip slip: vertical movement due to tensile hoop stress
o Reverse slip: vertical movement due to compression
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Figure 2-1. Longitudinal Fracture: Vertical Crack (left), Dip Slip (center), and Reverse Slip (right)
Longitudinal cracking is initiated by a crack or a defect in the pipe manufacture. This failure mode can be
caused by internal water pressure, external loading which can create bending and crushing forces on the
pipe, or compressive forces acting along the pipe particularly where the backfill or bedding support is
suspect. Any of these loadings could result in a longitudinal crack. Once the crack has been initiated, it
may travel the length of the pipe. Cracks can form on opposite sides of the pipe, resulting in a section of
the top of the pipe being removed.
2.3.2 Circular Fracture. Circumferential cracking is the most common failure mode for small
diameter (< 380 mm [15 in.] diameter) grey cast iron pipes (Table 2-3) and can be located at the invert,
springline, crown, or across the whole pipe (Marshall, 2001). The principal failure mechanism is due to
longitudinal tensile stress.
Table 2-3. Percentage of Failures by Mode for Iron Pipe (< 15 in.)
Circumferential
66.4%
Longitudinal
13.3%
Hole
16.1%
Joint
4.2%
Some studies suggest that the majority of failures in all grey cast iron are due to circumferential breaks
(Makar, 1999a). Typically, this type of failure occurs in small diameters and is caused by bending forces
applied to the pipe with a failure crack propagating across the circumference of the pipe. Investigations
of failures by NRC Canada's Institution for Research in Construction (IRC) have indicated that 90% of
failures have corrosion pits or graphitization located at the fracture surface. In addition, IRC found that
95% of the failures showed evidence of multi-stage failure (Makar, 1999b).
Large diameter pipes generally have a higher moment of inertia and are less prone to circumferential
failures (Rajani and Kleiner, In Press 2013). Although not common, there are recorded cases of
circumferential cracking in large diameters (Rajani and Kleiner, In Press 2013). The relationship of
circumferential to longitudinal failure modes for small (<15 in.) diameter cast iron pipe is illustrated in
Table 2-3 and for all diameters in Figure 2-2. This was developed from 72,000 UK water systems data
records of burst failures in the period from 1992 to 1998 collected by UK Water Industry Research
(UKWIR) (Marshall, 2001). In general, circumferential failures were more prevalent in smaller diameter
mains, and, by comparison, longitudinal failures were more common than circumferential failures for
mains 10 in. and larger.
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2.3.3 Mixed Fracture. Mixed fractures take two forms as illustrated in Table 2-2. One form is
principally longitudinal cracking where a crack initiating at mid-point propagates in either or both
directions depending on where soil support is least. The failure mechanism is tensile hoop stress in
combination with bending.
The shattering form of failure is due to the annealing process that was used on spun cast pipes with metal
molds and takes the form of multiple cracks. In this case, the failure mechanism is hoop tensile stress in
combination with residual stress.
2.3.4 Bell Splitting. Bell splitting can take two forms: (1) a longitudinal crack at the bell end
(Rajani and Kleiner, In Press 2013) or bell shard (Moser, 2008). The former failure mechanism is due to
hoop stress and the latter is caused by hoop and flexural tensile stress. Large diameter gray cast iron
pipes can fail by having a wedge section or shard of the bell shear off as shown in Table 2-2. Rajani and
Kleiner suggest bending forces are more likely to be the cause of this type of failure where a wedge is
split off to relieve the bending stresses and produce the type of shearing shown in the figure. Fatigue
crack growth is now also suggested as a possible failure mechanism. For fatigue failure to occur there has
to be a pipe defect such as a crack or manufacturing flaw, which may go undetected for years. Rajani and
Kleiner (In Press 2013) performed a failure analysis on a 30 in. cast iron main that failed in Cleveland in
2008 due to a bell split. The most likely failure scenario was determined to be due to additional rotation
of the pipe joint, which likely induced a small crack in the bell that grew uncontrollably under fatigue
loading and eventually causing the bell to split.
3
o
Circumferential
Longitudinal
8 10 14 16 20 22 28 36
Nominal Diameter (in)
Figure 2-2. Graph of Failures Modes to Diameter (UKWIR)
2.3.5 Corrosion. Corrosion in the form of pitting and/or graphitization is a common but not
exclusive factor in most pipe failures. Possible causes are localized corrosion cells, adverse soil
chemistry, and bacteria. Pitting is the most common form and occurs quite randomly and leads to leaks
rather than structural failures. Corrosion pitting thins and weakens the pipe wall to the point where the
water pressure blows out the remaining, very thin pipe wall. This type of corrosion failure may produce a
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very small hole or a large one, depending on how localized the corrosion process has been and the
pressure experienced by the pipe.
Wall thinning can also make the wall susceptible to failure from external loads (e.g., live loads, traffic
loads, bending loads, etc.), but these loads are relatively small compared to internal pressures. Where the
through wall perforation is small, the pipe does not structurally fail or in some cases even leak as the
corrosion product can act as a stopper in the pipe wall hole (Marshall, 2000).
Graphitization, which is an important form of failure, is a corrosion process that removes some of the iron
leaving a matrix of graphite flakes held together by iron oxide. Graphitization is often not discernible to
the eye as it forms a substance with some strength albeit considerably reduced and with the appearance of
normal cast iron.
2.4
Potential Contributory Factors to Failure
Pipe condition is the cumulative effect of many factors acting on the pipe (Table 2-4; Al-Barqawi and
Zayed, 2006). These factors are classified into three categories: physical, environmental, and operational.
The factors in the first two classes could be further divided into static and dynamic (or time-dependent).
Static factors include pipe material, pipe geometry, and soil type, while dynamic factors include pipe age,
climate, and seismic activity. Operational factors are inherently dynamic.
Table 2-4. Factors Contributing to Water System Deterioration
Physical Factors
Pipe age and material
Pipe wall thickness
Pipe vintage
Pipe diameter
Type of joints
Thrust restraint
Pipe lining and coating
Dissimilar metals
Pipe installation
Pipe manufacture
Environmental Factors
Pipe bedding
Trench backfill
Soil type
Groundwater
Climate
Pipe location
Disturbances
Stray electrical currents
Seismic activity
Operational Factors
Internal water pressure
Transient pressure
Leakage
Water quality
Flow velocity
Backflow potential
Operation and maintenance
(O&M) practices
Al-Barqawi and Zayed, 2006.
Many of the factors are not readily measurable or quantifiable, and the quantitative relationships between
these factors and pipe failures are not completely understood.
2.4.1
Physical Factors
2.4.1.1 Pipe Age, Material, and Manufacture. Manufacturing defects can play a large role in the
failure of pipes including non-uniform wall thickness with the earliest forms of manufacturing being the
most variable. CI pipes were basically manufactured by two systems, namely pit casting and
centrifugally, or spin casting. Vertical pit casting was the preferred method of manufacturing due to the
longer sections of pipe that could be cast. Horizontal casting was limited by the flexural rigidity of the
mold core where bending of the core could cause inconsistent wall thickness along the length of the pipe.
In the 1920s, the process of centrifugally casting gray cast iron pipe was introduced and became the
primary manufacturing method of cast iron pipe by the early 1930s. This method involved pouring the
molten iron into a mold that was horizontal and spinning. The speed of the spinning depended on the
9
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required thickness of the pipe. In turn, cast iron pipe was gradually replaced by ductile iron pipe starting
in the 1950s. Cast iron pipe was being manufactured and installed until the 1970s, albeit in limited
quantities, so by definition even the most recent spun iron pipelines are 50 years old.
Probably the most common manufacturing defect is the inclusion of air trapped in the metal during the
casting process. Other common manufacturing defects are unintentional inclusions of material such as
ferrosilicon or iron oxide during casting, which can act as crack formers. The addition of phosphorus
during the casting process to lower the melting point and viscosity can produce an iron phosphide
compound which is more brittle than cast iron and weakens the pipe. Spun cast pipes have fewer casting
defects than pit cast and variations in wall thickness are less. The spin casting process can produce
surface flaws such as laps, laces, and pinholes. These flaws are due to the uneven cooling process that
can trap air creating boundary layers that can lead to fissure cracking.
With numerous producers of pit and spun cast iron pipes using varying feed stock there are often
significant differences in the micro-structure and quality. An American Water Works Association
Research Foundation (AWWARF) report "Investigation of Grey Cast Iron Water Mains to Develop a
Methodology for Estimating Service Life" (Rajani et al., 2000) provides detailed data on mechanical tests
and metallurgical analyses properties. It is noted that the tests showed that the tensile strength and
fracture toughness are significantly lower for pit than spun grey cast iron. This is attributable to the
microstructure of the metal. Carbon grey flakes act as crack formers. The larger flakes in pit cast pipe
make it easier for cracks to initiate.
Pit cast and spun cast iron exhibit brittle behavior. A typical stress-strain curve for both pit cast and spun
cast iron together with ductile iron is shown in Figure 2-3 (from Cassa, 2008 and Sears, 1964). The
brittle behavior of both pit cast and spun cast iron is apparent in the figure, with rupture failure occurring
at a low value (<1%) of axial strain. The pit cast iron, which fails at a slightly lower axial strain, is
slightly more brittle than the spun cast iron. Ductile iron is, as its name suggests, substantially more
ductile. It has a yield point at an axial strain near the breaking strength of pit cast and spun cast iron, but
then it undergoes plastic strain until it fractures at an axial strain in the low percent range, e.g., 4.5%, as in
the figure. Rajani et al. (2000) has test results for failure strain for nearly 200 test samples of pit and cast
iron. The variations in mechanical properties of cast iron are discussed in considerable detail in Chapter 2
of Rajani and Kleiner (In Press 2013), with spun iron having better and more consistent properties than
pit cast pipes.
10
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Typical Ductile Iron and Cast Iron Pipe Stress-Strain
Ultimate Strength
Pit Cast Stress-Strain
Spun Cast Stress-Strain
Ductile Iron Stress-Strain
Fracture
1.5 2 2.5
Tensile Strain (%)
3.5
4.5
Figure 2-3. Typical Stress vs. Strain Relationship for Cast Iron and Ductile Iron
2.4.1.2 Pipe Wall Thickness and Vintage. The wall thickness of pit cast iron pipes can frequently
vary around the circumference of the pipe. This can be up to 30% plus and minus variation from the
average wall thickness. Spun pipes are less variable but may have some wall thickness variation. Pipe
wall thickness over time has reduced for the same pressure rating, as shown in Table 2-5.
Table 2-5. Changing Wall Thickness for a 36-in. Pipe Operating at 150 psi
Year
1908
1952
1957
Material
Cast iron
Spun iron
Spun iron
Wall Thickness (in.)
1.58
1.22
0.94
In any evaluation it is important to know the pipe vintage and the original wall thickness. The vintage can
assist in determining the method of production, which is important in understanding the physical and
mechanical properties and potential manufacturing defects. Early cast iron foundries were numerous and
set up to serve local markets. Considerable quality variations have been identified. Original pipe
thickness is important in setting the baseline for determining loss of metal.
2.4.1.3 Pipe Diameter. In terms of failure rates, diameter is a significant factor and typically the
larger the diameter the lower the failure rate. Based on a set of UK failure records for cast iron pipes
spanning 60 years, an analysis showed the average failure rates by diameter (Table 2-6). As can be seen,
the average failure rate for a 6 in. pipe is five times greater than for a 21 in. pipe.
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Ta
ble2-6. Failures
Diameter (in.)
6
8
10
12
15
18
21
per km/yr. by Diameter
Failures/km/year
0.204
0.141
0.105
0.083
0.062
0.049
0.040
2.4.1.4 Type of Joints. The types of joints commonly found in cast iron pipes are:
• Bell-spigot jointed with lead
• Bell-spigot jointed with leadite (a sulfur based compound)
• Push joint sealed with a rubber gasket
A typical bell-spigot joint configuration for cast iron pipes is shown in Figure 2-4 (Rajani and Kleiner, In
Press 2013). Joints in cast iron pipes were originally sealed using rope packed between the bell of one
pipe and the spigot of the other. Molten lead was then poured into the joint to complete the seal. The
behavior of these joints is highly dependent on the type and condition of the packing and caulking
materials. In water mains, where the packing remained pliable and deformable, rotation is allowed at the
joint. The packing also swelled with the absorption of water, which helps in sealing any points of
leakage.
Failure at a joint can be partial or complete. Partial failure occurs at lead caulked joints when the rotation
is enough to cause an opening to form in the joint where the packing and the pipe are in contact. This
allows leakage to occur at the joint. Complete failure occurs when the rotation at the joint is great enough
to cause the spigot to force the packing out of place and for the spigot and bell to come into contact.
Leakage can also result from undetected cracks in bell and/or spigot, which may have occurred as
described in 2.4.1.6.
Lead
caulking
Groove
(a) Unrelated bell and spigot
(b) Rotated bell and spigot
Figure 2-4. Typical Bell-Spigot Joint Configuration
This metal-to-metal contact between the two pipe sections, called metal binding, is the point where the
joint is considered to have completely failed because the addition of a small rotation will cause a large
increase in the stress within the joint. It has been noted that spigots that have had the asphaltic coating
12
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removed can develop significantly large moments compared to joints with asphaltic coatings (Rajani and
Kleiner, In Press 2013). Other noted problems include overzealous caulking particularly with pneumatic
hammers, and use of oversized tools which can cause bell cracks.
Leadite, a rigid, sulfur based compound was used in the 1930s and 1940s as a substitute for lead. As a
non-metallic compound, leadite has a different thermal coefficient of expansion than lead and it was a
widely held belief that for very cold temperatures it was a cause of bell splitting. Rajani and Kleiner
carried out a detailed test program on leadite using a temperature range of -20° to +20° C. No significant
coefficient changes were noted over the range and the study demonstrated that a difference in thermal
coefficients between lead and leadite is not significant enough to confirm that leadite joints are more
prone to failure (Rajani and Kleiner, In Press 2013).
In the same study, Rajani and Kleiner also undertook an in-depth study of rotation limits in cast iron lead
and leadite joints. They developed bi-linear and non-linear models based on limited data, much of which
related to smaller diameters. They determined that a joint rotation of 0.5° is likely to allow leakage. The
analysis showed that the extent to which a pipe joint can rotate without failure when subject to soil
movement decreases with an increase in diameter. They also noted that the likelihood of perfect
alignment when installed was unlikely, so the need is to monitor the relative changes in joint rotation
rather than the absolute, as a relatively small change could put the joint in an overstressed position.
2.4.1.5 Pipe Lining and Coating. Cement mortar lining is used for potable water lines not only for
potability, but also for inhibiting internal corrosion. Damage to any coating of the pipe wall can affect the
performance of the pipe by facilitating corrosion and degradation of the pipe wall. Unlined pipe is
susceptible to tuberculation and internal corrosion. Cement lining may be degraded by carrying water
with a low pH or abrasion due to high water velocity and sediments.
2.4.1.6 Pipe Installation. A significant number of pipe failures can be attributed to the original
installation. A number of reports, some going back to the early twentieth century, have drawn attention to
the potential for cracks to have been created because of the way pipes were loaded, transported, unloaded,
stored, and installed. There are numerous references, one dating back to 1911, which are listed and
reviewed in Chapter 1 of "Fracture Failure of Large Diameter Cast iron Water Mains" (Rajani and
Kleiner, In Press 2013). Small undetected cracks both in the bell and spigot can be created, which can fail
over time due to fatigue from external loads and internal pressure. Detection of these cracks that have not
surfaced with inspection technologies could potentially indicate a pipe in distress.
2.4.1.7 Other Physical Factors. Other factors include thrust restraint and dissimilar metals (see
Section 2.4.2.3). Inadequate thrust restraint can increase the longitudinal stresses in the pipe, which can
lead to circumferential fractures.
2.4.2 Environmental Factors
2.4.2.1 Pipe Bedding and Backfill. Many early installations did not take into account the need for
proper bedding and backfill and practices such as supporting pipes in the trench on blocks of wood were
used. The first AWWA standard issued in 1908 (AWWA 7C. 1) did not address how pipes should be laid.
CIPRA's pipe manual of 1927 indicated the need for continuous support and avoiding sharp or hard
objects under the pipe. The manual also emphasized the need to compact trench backfill. During the
1920s, research was conducted at the University of Illinois and Iowa State on the importance of bedding
and backfill. This work was fundamental to the standards that were developed over the next decades.
2.4.2.2 Soil and Groundwater. Depending on the way they were installed, pipes may be surrounded
by natural occurring soil or by imported material. In general, soil and groundwater are not very
aggressive and correlations between soil type and deterioration can be unreliable and tenuous. However,
13
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there are exceptions where aggressive and contaminated soils are involved, and external corrosion can be
created. There is a great deal of literature from researchers and vendors proposing relationships between
soil properties and corrosion: Ductile Iron Pipe Research Association (DIPRA, 2005); Ferguson and
Downey (2009); Booth et al. (1967); and Jarvis and Hedges (1994).
2.4.2.3 Galvanic Corrosion. Galvanic corrosion can occur when dissimilar metals are electrically
connected. This is more likely to occur in distribution mains where connections are made onto the pipe.
A galvanic cell can also occur when a CI pipe is installed in a non-uniform soil. An example would be
where lumps of clay are in contact with the pipe in a sand backfill. Another factor contributing to
corrosion is pipe location (e.g., the migration of road salt into the soil can increase the corrosion rate).
2.4.2.4 Stray Electric Currents. Stray electric currents are generated by an adjacent direct current
(DC) source. A ferrous pipe can offer a better earthen route for conveying stray currents from electrified
transport systems, electrical installations such as pylons, and cathodic protection systems. Most cast iron
installations are not electrically continuous as lead and leadite are poor electrical conductors. Pipes
jointed with rubber gaskets are also not considered to be electrically continuous. A number of authorities
have retrofitted lines with impressed current or sacrificial anodes to achieve cathodic protection of pipes.
2.4.2.5 Microbiologically Influenced Corrosion. The two forms of microbiologically influenced
corrosion (MIC) are anaerobic and aerobic. Sulfate reducing bacteria (SRB) are typical examples of
anaerobic bacteria. Corrosion can occur even in the absence of dissolved oxygen (Ferguson and
Nicholas, 1984).
2.4.2.6 Soil Movement and Disturbances. When pipes are laid in trenches, they are subject to
external pressures that act on the pipe. These external loads are not symmetrical; therefore, the
differential loading can cause bending in the pipe wall. Possible loads on buried pipes include vertical
soil pressure, superimposed live loads due to vehicles, frost loading, self weight of pipe and its contents,
crushing or bending by heaving, swelling, or contraction of soils, and even seismic activity causing
increased stresses on the pipe. Thus, the excessive loads can result in failure due to either crushing or
compression in the pipe.
Failure of cast iron pipe with bell joints was reviewed earlier in this section. Soil movement can cause
joint rotation, leading to leakage and ultimately failure. The soil movement can be due to external causes
or by joint leakage eroding bedding support. It is quite common to find that leakage has gone undetected
for long periods. Table 2-7 provides information on the potential for loss of support, soil movements, and
soil expansion.
Table 2-7. Soil Types and Impact on Structural Defects
Soil Type
Rock
Gravel above water table
Gravel below water table
Sand/silts above water table
Sand/silts below water table
Clay
Organic
Potential for
Loss of Support
Low
Low
Moderate
Moderate
High
Low
High
Potential for Soil
Movements
Low
Low
Low
Moderate
High
Low
High
Potential for Soil
Expansion
Low
Low
Low
Low
Low
High
High
14
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2.4.2.7 Climate. Changing soil temperatures are of concern in northern regions where freeze/thaw
cycles can cause soil movement. The impact appears to be greatest on small diameters. Precipitation is
another factor, as it impacts soil moisture, which in turn impacts frost penetration and expansion and
shrinkage of expansive clay soils.
2.4.3 Operational Factors. Poor or incorrect operational and maintenance practices can be a
factor in the failure process.
2.4.3.1 Hydraulic Factors. Hydraulic operational factors that can influence failures include internal
water pressure, transient pressures, and water hammer. Large and rapid changes in flow velocity (e.g.,
fast valve closures or power outages in pumping stations) can create transients greater than the design
limits. High pressures create high stress in the pipe and a higher likelihood of failure. Frequent pressure
changes can be a factor in fatigue failure. A combination of loss of metal or flaws and transient pressures
can be a significant cause of failure.
2.4.3.2 Leakage. Leakage is common and often goes undiscovered. As discussed in Section 2.4.1.4,
as little as 0.5° of rotation will lead to leakage from a bell and spigot lead or leadite joint. This leakage
can erode support and allow further rotation and failure.
2.4.3.3 Other Operational Factors. Other factors include: water quality (e.g., aggressive water
promoting corrosion); flow velocity (e.g., unlined dead-ended water mains having a higher rate of
corrosion); backflow potential from cross connections with non-potable water systems; and poor O&M
practices.
2.5 Condition Assessment - Distress and Inferential Indicators
Many of the factors contributing to failure are not readily measurable or quantifiable, nor are the
quantitative relationships between these factors and pipe failures always well understood. In undertaking
a condition assessment program and undertaking a condition investigation, the use of distress and
inferential indicators can greatly aid the process.
Distress indicators are defined as the observable/measurable physical manifestations of the aging and
deterioration process. Distress indicators are a result of some or all of the factors listed above. Each
distress indicator provides partial evidence for the condition of specific pipe components.
Inferential indicators (U.S. EPA, 2012a) point to the potential existence of a pipe deterioration
mechanism. They do not provide direct evidence, but rather indicate the possibility without knowing if
this potential has actually been realized. Environmental indicators, such as soil type, groundwater
fluctuations, etc., are inferential in nature. These indicators are cost effective in pre-screening pipes to
select those that should receive more expensive direct inspection.
2.5.1 Distress Indicators for Cast Iron Pipe. Distress indicators as set out in Table 2-8 can be
discerned by direct observation in some case, while many require more sophisticated methods of
investigation (Kleiner et al., 2005). It is important to understand that the information obtained will come
from a variety of sources and forms and needs to be aggregated and interpreted by some kind of pipe
condition rating system to quantify the condition.
15
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Table 2-8. Distress Indicators that Influence Pipe Condition for Cast Iron Pipes
Category
External coating
(poly wrap/tar/etc)
External pipe
barrel/bell
Inner lining/
surface
Joint
Distress Indicator
Crack/tear/holiday
Remaining wall thickness
Graphitization (pit) aerial
extent
Crack (pit) type
Crack (pit) width
Cement lining spalling
Remaining wall thickness
Tuberculation
Change in alignment
Joint displacement
Comments
State of external coating will dictate how external corrosion
is likely to encourage damage to the pipe.
Remaining pipe wall thickness is usually obtained from
nondestructive evaluation (NDE) tests or from spot
exhumations and sand blasting samples. Casting defects
(voids or inclusions) can be of significant size in CI pipes.
Areal extent as percentage of pipe diameter times unit length
indicates the size of affected area. Severe graphitization may
not always mean the pipe should have failed. In practice,
graphitized area can still provide some resistance - it acts as
a form of sticky plaster. In CI graphitization is typically in
the form of graphite flakes.
Circumferential cracks indicate some type of longitudinal
movement, loss of bedding support, or increase in vertical
load (e.g., frost) has taken place. Longitudinal cracks occur
due to low hoop resistance and can be caused by internal
water pressure, external vertical loads, or compressive forces
acting along the pipe.
Crack width is another indicator of corrosion. A wide crack
together with a deep pit will be more detrimental to the pipe
than a narrow but shallow crack.
Inner lining deterioration is often due to incompatible water
chemistry or abrasion due to the presence of high water
velocities and sediments.
Occasionally closed circuit television (CCTV) scans can
indicate internal corrosion pits. NDE testing is required to
give qualitative information on remaining wall thickness.
Heavy tuberculation can hide defects in the wall including
pitting. It also needs to be removed for internal inspection by
NDE tools. It can significantly reduce water delivery and
produce red water condition.
Changes in joint alignment (rotation) indicate pipe
susceptible to ground movement. As little as 0.5° or rotation
can lead to leakage and eventually joint failure (Rajani and
Kleiner, In Press, 2013).
Joints can displace without undergoing joint misalignment
and hence is also an indicator of other forces at play.
16
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2.5.2 Inferential Indicators for Cast Iron Pipes. Inferential indicators are a pointer to a potential
cause or causes of failure without providing any direct information on pipe deterioration. Some indicators
can be found in data records, while others are environmental and will be specific to the location. They are
valuable as a pre-screening tool and relatively easy and cheap to use. The inferential indicators described
in Table 2-9 are adapted from Kleiner et al. (2005).
Table 2-9. Inferential Indicators for Cast Iron Pipes
Category (Level 1)
Pipe vintage
Water quality
Water loss
Water pressure
Location
Soil
Corrosion
Agent (Level 2)
Material type
Water pH
Leaks
Operating pressure
(OP)
Pressure change
amplitude
(% OP)
Pressure change
frequency
Pipe embedment
Surface loads - traffic
type
Wet/dry cycle(s)
Water table level
Soil type / backfill
Soil resistivity (ohm-
cm)
Soil pH
Redox potential
Soil chloride
Soil sulfate
Soil sulfide
Frost susceptibility
(load)
Cathodic protection
Stray current
Comments
Pipes of specific vintages have experienced a higher breakage
rate.
Water with low pH can leach the internal cement lining or pipe
wall itself if lining is absent.
May be due to through wall pitting corrosion or joint
displacement
High pressure subjects pipe to high stress and hence higher
propensity to failure.
Large pressure changes (% of OP) can induce higher stresses
than expected by design.
Either slow or fast fatigue mechanism can induce early failure.
Pipes exposed to wet/dry conditions have higher failure rate
than pipes totally below water table or pipes totally exposed to
atmosphere.
Heavy surface loads will subject the pipe to high stresses and
hence faster deterioration in the long term.
Changing environment can promote corrosion.
Water table position will indicate if wet/dry cycle is likely to
occur.
Non-draining backfill leads to moisture retention and hence
promotes corrosion.
Low resistivity soil leads to higher corrosion rates.
Low pH (< 4) means soil is acidic and likely to promote
corrosion; high alkaline conditions (pH > 8) can also lead to
high corrosion.
High availability of oxygen promotes MIC in the presence of
sulfates and sulfides.
Low chloride levels in high pH (> 1 1.5) environments can lead
to serious corrosion.
Accounts for MIC and possible food source for SRB in
anaerobic conditions under loose coatings.
Sulfate reducing bacteria give off sulfides, which are excellent
electrolytes.
CI pipes are not designed for frost loads. If conditions exist to
develop significant frost loads, then pipe will be subjected to
additional stresses (annual) and lead to pipe failure if already
significantly corroded. These conditions are: high water table;
thermal gradient; right soil type to develop suction (i.e., silt or
clayey silt).
Impressed current is likely to reduce corrosion.
Stray current is known to accelerate corrosion unless adequate
measures have been taken.
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SECTION 3.0: STRUCTURAL INSPECTION COMPONENTS AND SYSTEMS
3.1 Overview
To successfully monitor structural condition, a combination of screening, monitoring, and condition
assessment techniques need to be used. This section briefly presents available inspection and monitoring
technologies with the potential for detecting and monitoring pre-failure damage indicators in large
diameter cast iron mains (greater than 16 in. in diameter). The broad categories of available inspection
technologies are presented, along with a summary of the types of defects and pre-failure indicators that
can be detected. For each category of inspection tool or component, the applicability and/or known
limitations for the inspection of large diameter cast iron water mains are also noted.
The purpose of the protocol development in this report is to identify and evaluate emerging inspection and
monitoring technologies, including those developed for other applications, and to assess their
applicability and suitability for large diameter cast iron water mains. For that reason, this section also
documents the organizations involved in structural inspection technology and component research.
Although this report only provides a snapshot of the research currently being conducted for structural
inspection components and systems, several of the key stakeholders involved in inspection technology
research remain fairly constant over time including certain Federal agencies and non-profit research
organizations. In addition, private companies and technology vendors are an important source of
fundamental research and technology development of inspection tools and platforms. These key
stakeholders and their overall research interests are summarized here in order to aid in the identification
and screening of emerging structural inspection technology research for cast iron water mains discussed
later in this report.
3.2 Available Inspection and Monitoring Technologies
This section provides a broad overview of structural inspection technologies with some observations on
their suitability and known limitations for cast iron water main inspections. More detailed reviews of
these technologies can be found in the EPA reports titled, Condition Assessment of Ferrous Water
Transmission and Distribution Systems (U.S. EPA, 2009) and Condition Assessment Technologies for
Water Transmission and Distribution Systems (U.S. EPA, 2012a). In addition, numerous sources provide
detailed information on inspection and monitoring technologies including: American Water Works
Research Foundation (AWWARF) reports titled, Techniques for Monitoring Structural Behavior of
Pipeline Systems (Reed et al., 2004) and Workshop on Condition Assessment Inspection (Lillie et al.,
2004); the Water Environment Research Foundation (WERF) reports titled, Inspection Guidelines for
Ferrous Force Mains (Jason Consultants, 2007) and Condition Assessment Strategies and Protocols for
Water and Wastewater Utility Assets (WERF, 2007); Control and Mitigation of Drinking Water Losses in
Distribution Systems (U.S. EPA, 2010); Rajani and Kleiner (2004); and the UKWIR report titled, A
Survey of Practices for the Detection and Location of Leaks (UKWIR, 2011).
3.2.1 External Inspection Technology Description. External condition assessment tools provide
detailed condition information for selected locations along the pipeline and then rely on statistical
methods to predict the condition of the entire pipeline segment. Often the detailed external assessments
are supplemented with soil corrosivity and coating condition data to improve confidence in the statistical
predictions. Although these technologies are capable of inspecting the entire pipeline length, excavation
is required but it is rarely practical.
External inspection of pipelines has been widely used because it allows the pipeline to remain in service
while the localized condition of the pipe is being assessed. Often small areas around the pipe must be
cleared because the sensors on the device need to have contact with the outside pipe surface. Table 3-1
18
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summarizes the overall applicability of structural inspection tools for external inspection of cast iron
water mains and the type of defects that can be detected.
Table 3-1. Tools and Technologies for Inspecting Structural Integrity Externally
Application
Diameters
Typical Length Scanned
Line in Operation
Scan through Coatings
Scan through Pipe Wall
Loss of Metal
Pit Depth
Graphitization
Cracks
Mobilization Costs
Scanning/Processing Cost
Suitable for Water Mains
Pit Depth
Measurement
Any
3 to 6 ft
Yes
No
No
Yes
Yes
No
No
Low
Low
Yes
Ultrasonics
Any
3 to 6 ft
Yes
No
Yes
Yes
No
No
No
Low
Med
Yes
MFLb
>6in.
3 to 12 ft
Yes
Yes
Yes
Yes
No
Yes
Yes
Med
Med
Yes
(BEM)C
>2in.
3 to 12 ft
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Low
Low/Med(a)
Yes
(a)Real time provides immediate condition, while full data processing is an additional cost.
(b)MFL = Magnetic Flux Leakage.(c)BEM=Broadband Electromagnetic
Adapted from U.S. EPA, 2009.
3.2.2 Internal Inspection Technology Description. Inline inspection technologies have been
used for years in the oil and gas industry to inspect pipelines for structural integrity issues such as
corrosion and mechanical damage. Inline inspection technologies for water mains can range from
relatively simple closed circuit television (CCTV) visual tools that assess the inner diameter of the pipe to
complex tools that assess the pipe wall thickness including remote field technology (RFT) tools. The
more complex technologies have only recently been used by utilities for inspection of large water mains
after a few main breaks that resulted in extensive service disruptions, significant property damage, and
costly repairs. Inline inspection systems provide valuable pipeline condition information especially for
water mains that cannot be taken out of service.
Issues that must be overcome for wide-spread use of inline inspection technologies for water mains
includes the lack of launching and receiving facilities on existing water mains, the variety of materials
used to construct water pipelines, and the expense of conducting such inspections. Table 3-2 summarizes
the overall applicability of structural inspection tools for internal inspection of cast iron water mains and
the types of defects that can be detected.
Table 3-2. Tools and Technologies for Inspecting Structural Integrity Internally
Application
Diameters
Typical Length Scanned
Line in Operation
Scan through Linings
Loss of Metal
Pit Depth
Graphitization
Cracks
Mobilization Costs
Scanning /Processing Cost
Suitable for Water Mains
Man-Entry
> 24 in.
Any
No
No
No
Yes
Yes
Yes
Med
Low
Yes
CCTV
>4in.
500ft
No
No
No
No
No
Possibly
Med
Low
Yes
RFT
up to 28 in.
10,000 ft
Possibly
Possibly
Yes
No
Yes
Yes
Med
Med
Yes
BEM
>6in.
3,000 ft
No
Yes
Yes
No
Yes
Yes
Med
Med/High
Yes
Adapted from U.S. EPA, 2009.
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Internal MFL technology was not included in Table 3-2, but the use of this technology for large diameter
water mains is currently being explored (Hannaford et al., 2010).
3.2.3 Leak Detection Technology Description. The main objectives of leak detection are the
reduction (or elimination) of water losses through leaks, as well as reducing the possibility of small leaks
developing into pipe failures. While addressing these two main objectives, information about leakage
rates provides an important indication about the condition of the pipe (U.S. EPA, 2012a,b). Table 3-3
summarizes leak detection technologies suitable for cast iron water mains.
Table 3-3. Tools and Technologies for Leak Inspection
Application
External/Internal
Diameters
Typical Length Scanned
Line in Operation
Joint Leaks
Wall Perforation Leaks
Accuracy Locating Small Leaks
Insertion into Line
Mobilization Costs
Scanning/Processing Cost
Suitable for Water Mains
Visual
Inspection(a)
External
Any
Any
Yes
No
No
Poor
N/A
Low
Low
Yes
Leak
Correlators
External
Most
300ft
Yes
Yes
Yes
Good
N/A
Low
Low
Yes
Listening
Sticks
External
Most
3ft
Yes
Yes
Yes
Fair
N/A
Low
N/A
Possible
Acoustic Leak
Detection
Internal
> 12 in.
Miles
Yes
Yes
Yes
Excellent
via valve or tap
Low/Med
Low/Med
Yes
a> Can detect leakage or ground movement, but not leak type or location.
3.2.4 Summary. Table 3-4, which is adapted from the 2009 and 2012 EPA reports, focuses the
structural inspection technology discussion on the advantages and limitations of the technologies suitable
to large cast iron water mains (>16 in. diameter).
3.3
Structural Inspection Technology Research Applicable to Cast Iron Water Mains
Key U.S. stakeholders involved in structural inspection technology research are briefly mentioned here to
serve as a preliminary guide to potential sources of emerging technologies that could be evaluated for
their suitability for large diameter CI water mains. Research from multiple Federal organizations has
been reviewed including the: EPA; U.S. Department of Transportation (DOT); U.S. Department of
Energy (DOE); U.S. Department of Defense (DOD); U.S. Department of Commerce (DOC); U.S.
Department of Homeland Security (DHS); U.S. Department of the Interior (DOI); National Science
Foundation (NSF); and National Aeronautics and Space Administration (NASA). Also, research from
non-profit research organizations such as WaterRF, WERF, and the Gas Technology Institute (GTI) as
well as private industrial research is briefly discussed. International stakeholders, particularly from
Canada, the UK, Australia, and Germany are also important sources of innovative inspection technologies
and procedures.
Appendix A briefly describes the role of each agency in structural inspection technology research. Table
3-5 summarizes the organizations that fund research that is potentially relevant to structural inspection for
large diameter cast iron water mains. For each organization, example research activities and projects are
listed, but this is not a comprehensive list. The EPA report White Paper on Improvement of Structural
Integrity Monitoring for Drinking Water Mains (Royer, 2005) lists other projects undertaken by these
organizations for non-drinking water systems, which may have potential for application to water
conveyance systems.
20
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Table 3-4. Available Inspection and Monitoring Technologies Applicable to Cast Iron Mains
Technology
Diameters
Advantages
Limitations
External Technologies
Pit depth
measurement
Ultrasonics
Magnetic
flux leakage
Broadband
electro-
magnetic
Acoustic
wall
thickness
All
All
>6in.
>2in.
>2in.
• Direct measurement of pit depth, no need
for interpretation.
• Provides good indication of sample
condition.
• Exposed pipe does not need to be taken
out of service.
• Sensitive to both surface and subsurface
discontinuities.
• Provides instant results of metal loss.
• Probes of different sizes and frequencies
are available.
• Supply shutdown is not necessary.
• Detects cracks, graphitization, and
measures wall thickness.
• Does not require a service interruption.
• Contact with the pipe wall not required.
• Scans through coatings and linings.
• Detects cracks, graphitization, and metal
loss.
• Finds average wall thickness between
excavation points.
• No contact with water.
• Requires statistical analysis to infer
general condition of CI.
• Existing coating must be removed and
pipe exposed.
• Thickness must be known for corrosion
estimate and testing varies.
• CI and other coarse grained materials
are difficult to inspect due to low sound
transmission and high signal noise.
• Surface to be inspected must be
accessible and clean.
• Coupling medium required for some
products.
• Accuracy is higher if sensors maintain
direct contact with the CI pipe wall.
• Not widely used due to cost.
• Resolution depends on size of the
sensor.
• Unable to define/quantify pin-hole
failures or isolated pits.
• Scanning process is not continuous.
• Resolution depends on spacing between
excavation points.
• One bad pipe length in a pipeline that is
generally good may not be detected
Internal Technologies
Man entry
inspection
Broadband
electro-
magnetic
Closed
circuit TV
Remote field
eddy current
Internal
acoustic wall
thickness
> 24 in.
>6in.
>4in.
< 28 in.
>2 in.
• No special equipment required.
• Assessment can provide an indication of
the cause of the deterioration and the
likelihood of being more widespread.
• Contact with the pipe wall not required.
• Scans through coatings and linings.
• Detects cracks, graphitization, and metal
loss.
• Digital recording is convenient for data
storage, as well as future developments in
automatic data interpretation.
• Inspection of in-service pipes is possible.
• Detects cracks, graphitization, and metal
loss.
• Finds average wall thickness at discrete
intervals as small as 1 ft and as large as
tens of feet.
• Has the potential to determine relative
wall thickness for specific pipe lengths.
• Only for man-entry CI pipes.
• Not effective finding defects not on the
inner pipe surface.
• Mains need to be taken out of service.
• Resolution depends on size of the
sensor.
• Unable to define/quantify pin-hole
failures or isolated pits.
• Scanning process is not continuous.
• Data for inner pipe wall only and
results need interpretation.
• Not for in-service mains and does not
find structural defects.
• Data interpretation needs experience.
• Some tools require pipe cleaning and/or
dewatering.
• Individual anomalies not detected.
• Used internally which requires
excavation and access.
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Table 3-4. Available Inspection and Monitoring Technologies Applicable to Cast Iron Mains (Cont.)
Leak Detection Technologies
Visual
inspection
Leak
correlators
Listening
sticks
Acoustic
leak
detection
All
Most
Most
> 12 in.
• Reveals leakage and ground movement
from the surface.
• Allows for assessment of the backfill.
• Used externally on operational lines.
• Locates leaks in joints and pipe walls.
• Used externally on operational lines.
• Locates leaks in joints and walls.
• Used internally on operational lines.
• Long surveys with a single insertion.
• Detects small noise disturbances.
• Cannot detect leak type or location from
the surface.
• May not detect non-surfacing leaks and is
costly to expose pipe.
• Scan length is limited to around 300 ft.
• Not as effective on transmission mains.
• Scan length is very short (~3 ft).
• Difficulty locating small leaks.
• Requires tapping for access points.
• May not see large leaks.
Table 3-5. Organizations Funding Structural Inspection Research Potentially Relevant to Water
Orgs Example Research Activities
EPA
Extramural research (e.g., cooperative agreements and contracts; condition assessment of ferrous
water transmission and distribution systems [U.S. EPA, 2009])
Periodic SBIR solicitations (e.g., in situ imaging of water pipelines using ultrasonics [Mu, 2011])
and STAR grants from the ORD NCER or Regional programs
NRMRL WSWRD water supply research
ETV, CEIT, and ITSC research programs
Leak detection research, pipeline test facilities, and in-house research
SDWA research (i.e., stakeholder input/assessment) of adverse water quality and health effects from
distribution systems in Total Coliform Rule
DOT
OPS; large extramural research program for natural gas and hazardous liquid pipelines, focus on 3-5
year horizon; on-line R&D project database; SBIR component; demonstration program
DOE
Fifteen national labs, many with NDE R&D
Natural gas pipeline research - NETL; sensors - Argonne, Sandia, Oak Ridge National Labs; R&D
for nuclear power (e.g., boiler tubing) and waste (e.g., pipe transport of low level waste); Intelli-Pipe
to enhance data transfer from drill bit to surface
DOD
USACE/CERL infrastructure research; RDT&E program; SERDP/ESTCP: leak detection research
Industrial Ecology Center- depot environmental management and compliance-related R&D
ARL sensors; NTIAC; Naval Facilities Command: study spill and leak prevention for pipes
DOC
NIST TIP: projects to advance composite pipes for energy exploration and recovery; and supporting
innovation through high-risk, high-reward research in areas of critical need.
TIP Project: Defect recognition using ultra wide band pulsed radar profilometry (NIST, 2011)
DHS
Science and technology research into pipeline security monitoring
DOI
BOEMRE/TA&R program supports operational safety and pollution prevention research
NSF
Sponsors a broad range of basic research in relevant areas (e.g., innovative sensors, materials, NDE,
information technology, data analysis); SBIR; grant programs
National Workshop on Future Sensing Systems (Glaser and Pescovitz, 2002)
No. 9901221: Non-contact sensors for pipe inspection by lamb waves (Kundu, 2005)
NASA
LaRC research of NDE technologies and interest in new materials
WaterRF
2727: Effects of corrosion pitting on circumferential failures in grey cast iron pipes (Makar, 2005)
2689: Potential techniques for the assessment of joints in water distribution pipes (Reed et al., 2006)
4035: Fracture failure of large diameter cast iron water mains (Rajani and Kleiner, 2011)
4234: Practical tool for deciding rehabilitation vs. replacement of cast iron pipes (WaterRF, 201 la)
4360: Acoustic signal processing for pipe condition assessment (WaterRF, 201 Ib)
WERF
Ol-CTS-7: Examination of innovative inspection methods (WERF, 2004)
04-CTS-6UR: Inspection Guidelines for Ferrous Force Mains (Jason Consultants, 2007)
03-CTS-20CO: Condition assessment strategies for utility assets (WERF, 2007)
GTI
Project No. 4.8.D: Broadband electromagnetic technology - sensor to measure wall thickness.
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4.0: PROTOCOL DEVELOPMENT
Effective and economical structural inspection can be an important component of asset management for
aging and deteriorating water conveyance infrastructure. Structural inspection provides data that can be
used to support estimates of current and future structural condition of water mains. These estimates can
be used to help optimize decisions about inspection, repair, rehabilitation, and replacement of water
mains. The value of optimal renewal decision making arises from (1) safely utilizing installed
infrastructure to its full life, (2) reduction of main break failures and their adverse health, safety,
environmental, and economic effects, and (3) prompt recognition and correction of significant leakage or
deterioration.
Scientific and engineering research is being conducted to develop and evaluate better, faster, and less
costly inspection technologies for water mains and other applications. To accelerate commercial
implementation, portions of the development and evaluation work are funded by government and industry
associations. Since resources are limited, it is very desirable to focus available resources on the most
useful and promising innovative condition assessment technologies. A thorough, systematic protocol for
reviewing innovative condition assessment technology options would be a useful tool for making and
justifying structural inspection technology research decisions. It is expected that any technology
evaluation protocol will be strongly influenced by the type of pipe and its associated failure behavior.
Large diameter cast iron pipe is an excellent type of pipe upon which to focus the initial condition
assessment technology evaluation protocol. Large diameter cast iron pipes have been commonly
installed, the consequences of failure can be high, and they are among the older pipes in the inventory.
Also, their failure behavior has been studied in some detail (e.g., by Cleveland Water Department,
WaterRF, NRC Canada), and the results of these studies can potentially help identify the monitoring
parameters and levels that are required for successful structural inspection and remaining life estimation.
The objective of the three screening protocols described in this section is to assist research funding
organizations, such as the EPA, in strategically evaluating the feasibility of emerging structural inspection
technologies for large diameter cast iron mains. The first screening protocol collects the data needed to
enable a user to determine if an inspection technology can be practically implemented on a large diameter
cast iron water main. The second screening protocol collects the data that enables a user to determine the
degradation condition or conditions that an inspection technology can detect and determines if the
technology locates the key distress indicators for large diameter cast iron water mains as identified in
Section 2 of the report. The third screening protocol compares a candidate technology to existing
technologies and determines the potential for further development.
A user is asked to answer the protocol questions in the series of flowcharts that follow based on the
current configuration of the technology. A second pass through the protocols can be performed based on
the development of a technically feasible modified configuration to the technology.
4.1 Basic Screening Protocol
Protocol 1 begins (Figure 4-1) by determining suitability for large diameter cast iron pipe and general
information about the intended capabilities of the technology. A reasonable large diameter minimum was
determined to be 16 in. based on a survey of experienced water utilities and researchers. Conditions that
may limit the suitability of a technology for inspecting large diameter cast iron mains include: tool length
(e.g., some technologies require a two pipe diameter separation between source and receiver, which
translates to a 4 ft separation for 24 in. pipe); large number of sensors (e.g., two sensors per inch of
circumference is 25 for a 4 in. pipe and 100 for a 16 in. pipe) for which the data must be processed and
stored); and launch and receive methods (e.g., cost of valves and fittings increases with diameter).
23
-------
/- -N
Nol appropriate for
-No-W
Vfurther development.
Technology
uitable for laree diamete
Note specific
defects, anomalies
or conditions.
Finds specific
defects?
Note what is
generally
assessed.
Provides general
assessment?
Detailed
measurements
at specific
locations?
Note defects and
extrapolation
methods.
Other
Capabilities
of note?
Note other
capabilities
Go to Section 1.0
Figure 4-1. First Step of Basic Screening Protocol: Determine Technology Capabilities
Now that the intended capabilities of the technology have been noted, Section 1.0 can be used
to determine the primary category of the technology.
24
-------
Section 1.0: Primary Categories
The primary categories of technologies are broken down into five primary categories, determined by the
flowchart in Figure 4-2. Once the correct category is selected, the user can follow the hyperlink below
each box to the appropriate section.
Section 1.0
Is equipment
inserted into the
•Yes-WGo to Section 1.1J
Is assessment
external with the
ipe exposed?
•Yes-WGo to Section 1.2J
Is inspection
performed from
xabove ground?/.
-Yes-WGo to Section 1.3J
No
Is inspection
performed from a
noving vehicle!/-
-Yes-WGo to Section 1.4)
Is equipment a
combination?
•Yes-WGo to Section 1.5J
Internal
Go to Section 1.1
External
Go to Section 1.2
Above Ground
Goto Section 1.3
From the Air
Goto Section 1.4
Combination
Goto Section 1.5
Figure 4-2. Primary Technology Categories
25
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Section 1.1: Internal Inspection
Section 1.1.1: Internal Condition. The internal inspection begins by determining the internal conditions
required for the technology to be used, determined by the flowchart in Figure 4-3.
Section 1.1.1
Internal Condition
Method
can work with
tuberculation and
sediment.
Does pipe
need to be clean to
bare metal?
Does pipe
need to be clean to
ternal coatine?
The internal surface of cast iron is not
accessible due to coatings and/or
natural deposits and tuberculation.
Limited use precludes development.
The pipe must be free of tuberculation,
debris, and sediment. Generally, the
pipe must be taken out of service to use
this method and the potential results
would have to be significant for utilities
to adopt this technology.
The method can operate with some
tuberculation, debris, and sediment in
the main. Note the amount of
tuberculation, debris, and sediment
allowable.
Not appropriate for
urther development.
Restart
Go to Section 1.1.2
Go to Section 1.1.2
Figure 4-3. Required Internal Condition
Section 1.1.2: Implementation Questions. Implementation issues (Figure 4-4) that govern the use of
structural inspection technologies are evaluated next. If a technology provides useful and detailed data,
the water utility will accept some significant implementation inconvenience to use the technology. If a
structural inspection technology provides more general data, the utility may still use the technology, if
implementation is easy. This section collects the data needed to make an implementation decision.
Section
Installation
tion 1.1.2 ~"\
ion Condition/
Is the
equipment
permanently in
the pipe?
Equipment is
temporarily inserted
into the pipe.
Go to Section 1.1.3
Go to Section \
1.1.4 J
Go to Section 1.1.4
Figure 4-4. Installation Conditions
26
-------
Section 1.1.3: Permanent Installation. If the method is permanently installed in the water main, the
sensors used, connection method, power source, and data handling should be determined and noted,
determined by the flowchart in Figure 4-5, and then Protocol 2 can be used.
Section 1.1.3 \
^Permanently Installed^/
Is the
method connection
continuous across
joints?
Series of
discrete monitoring
stations outside
the pipe.
Note the connection:
conductor, fiber optic or
sensor inside the pipe?
Will closin
a valve break the
connection?
Note how the sensors are
powered, how the data gets
out of the pipe, and how the
sensors communicate.
Method has potential to
work through extended
distances.
The method will work for
main valve to main valve.
f Go to Protocol 2 ]
Note how the sensors are
powered and how the data
gets out of the pipe.
Figure 4-5. Permanently Installed
Section 1.1.4: Temporary Internal Installation. If the device is temporarily installed in the water main,
the following questions should be answered and noted before going to Protocol 2.
Section 1.1.4.1: How does the device maneuver through the pipe?
A. Free swimming, propelled by water flow
B. Tethered, pushed or propelled by water flow
C. Powered by robotic crawler
D. Pulled through the main
E. Other, note process
Section 1.1.4.2: What is the launch diameter of the method tool?
A. Tool diameter < 6 in.
B. 6 in. < Tool diameter < !/> the pipe diameter
C. Tool diameter > !/> the pipe diameter
D. Tool diameter is nominally the pipe diameter
Section 1.1.4.3: What is the launch angle of the method tool?
A. Perpendicular to the pipe
B. With a '¥' fitting to the pipe
C. Parallel to the pipe
D. Other, note angle or configuration
27
-------
Section 1.1.4.4: What is the receive angle of the method tool?
A. Perpendicular to the pipe or returns to launch point for retrieval
B. With a '¥' fitting to the pipe
C. Parallel to the pipe
D. Other, note angle or configuration
Section 1.1.4.5:
Can the fitting be installed while the pipe is pressurized?
A. Yes
B. (Intentionally blank)
C.No
Section 1.1.4.6: How much flow is needed/allowed in the main?
A. Line is operational, no flow restriction or flow is allowed within a specific range
B. Line is full, but not operational
C. Line is partially full
D. Pipe must be taken out of operation and dewatered
Section 1.1.4.7: What is the smallest diameter of tees, branches, etc. that the flow must be stopped or
barred to prevent the tool from entering the connection for the tool to work?
A. Diameter > % main diameter
B. !/2 main diameter < diameter < % main diameter
C. % main diameter < diameter < !/> main diameter
D. Diameter < % main diameter
E. Other
Section 1.1.4.8: Can the method pass protrusions in the pipeline?
A. Large diameter (nominally % of main diameter or greater) !/> diameter into the main
B. Large diameter (nominally % of main diameter or greater) 1 in. into the main
C. Small diameter (nominally 2 in. or less) !/2 diameter into the main
D. Small diameter (nominally 2 in. or less) protruding 1 in. into the main
E. Other (describe the limits)
Section 1.1.4.9: Can the method pass inline obstructions?
• Butterfly valves
A. Yes, partially opened
B. Yes, fully opened
C.No
• Smooth bends:
A. Yes, sharp or miter bends
B. Yes, long smooth bends with bend radius > 3 diameters
C.No
Section 1.1.4.10: Do pipe obstructions need to be known prior to inspection?
A. No
B. (Intentionally blank)
C.Yes
The answers for the 10 questions above should be noted in the inline applicability grade card shown in
Table 4-1. The scale can then be used to determine the implementation factor before continuing on to
Protocol 2.
28
-------
Table 4-1. Inline Applicability Grade Card
1.1.4.1
Scale:
1.1.4.2
1.1.4.3
1.1.4.4
1.1.4.5 | 1.1.4.6
1
1.1.4.7
1.1.4.8
1.1.4.9
1.1.4.10
Implementation factor Easy: Mostly As and no Cs (or worse)
Implementation factor Moderate: Mostly Bs with a few As or Cs (or worse)
Implementation factor Difficult: Mostly Bs and Cs (or worse)
Section 1.2: External Inspection
Section 1.2.1: External Condition. The external inspection category begins by determining the external
condition required for the technology to be used, determined by the flowchart in Figure 4-6.
Section 1.2.1
External Condition
Method
can work with
corrosion and
scale.
Does pipe
need to be clean to
bare metal?
Does pipe
need to be clean to
ternal coatine?
Caution. Unless area is small, cleaning
the pipe to bare metal will preclude
development. (If only a small area is
needed go to Section 1.2.2.)
Note that the main must be cleaned
externally to the coating surface.
The method can operate with some
corrosion and scale on the main. Note
the amount of debris, sediment, and
scale allowable.
Not appropriate for
further development.
Restart or Go to Section 1.2.2
Go to Section
Goto Section 1.2.2
/ Go to Section >
V 1'2'2 J
Goto Section 1.2.2
Figure 4-6. Required External Condition
Section 1.2.2: Excavation Requirements. The excavation requirements that govern the use of a
structural inspection technology are described on the flowchart in Figure 4-7.
Section 1.2.2
Excavation
Sites
periodically
excavated for
ssessing state
Method
used when pipe is
accessed
for repair.
Sites
excavated for
assessing current
state?
Does the
entire pipe need to
be excavated?
Go to Section
1.2.3
Go to Section
1.2.3
Go to Section
1.2.3
Not appropriate for
urther development.
Restart Go to Section 1.2.3
Figure 4-7. Excavation Requirements
Go to Section 1.2.3 Go to Section 1.2.3
29
-------
Section 1.2.3: Number of Sites. If the method requires excavation, the requirements should be noted
below before going to Protocol 2.
Section 1.2.3.1: How many sites per distance are needed?
A. 1 per 1,000 ft
B. 1 per 500 ft
C. 1 per 200 ft
D. 1 per 100 ft
Section 1.2.3.2: What best describes the type of excavation?
A. Key hole
B. Crown of pipe, over ft
C. Top half of pipe, over ft
B. Full pipe circumference, over ft
Section 1.2.3.3: Do inspectors need to go into the trench?
A. No
C.Yes
Section 1.2.3.4: What best describes how long the sites must be open?
A. 1 excavation at a time, open less than: (Circle one) hour, !/> day, day, 2 days, week
B. 2 excavations at a time, open less than: (Circle one) hour, !/> day, day, 2 days, week
C. (no.) excavations at a time, open less than: (Circle one) hour, !/> day, day, 2 days,
week
Section 1.2.3.5: Is traffic permitted in lanes next to excavation?
A. Yes
B.No
Section 1.2.3.6: Once sensors are installed, can excavations be plated and traffic maintained while
inspection is being conducted remotely?
A. Yes
B.No
Section 1.2.3.7: Any other issues or features of the excavation?
The answers for the seven questions above should be noted in the external applicability grade card shown
in Table 4-2. The scale can then be used to determine the implementation factor before continuing on to
Protocol 2.
Table 4-2. External Applicability Grade Card
1.2.3.1
1.2.3.2
1.2.3.3
1.2.3.4
1.2.3.5
1.2.3.6
Scale:
Implementation factor Easy: Mostly As and no Cs (or worse)
Implementation factor Moderate: Mostly Bs with a few As or Cs (or worse)
Implementation factor Difficult: Mostly Bs and Cs (or worse)
30
-------
Section 1.3: Above Ground Inspection
Section 1.3.1: Implementation Questions. The above ground inspection category has fewer
implementation issues and hence fewer questions, as shown in Figure 4-8. Few cast iron pipes have
above ground electrical connections and continuous electrical conductivity. Modifying a pipe for
continuous conductivity and electrical connections would typically require excavation making the
inspection an external inspection.
Section 1.3.1
Above Ground
Pipe needs
bove ground electrica
connection and proven
continuous electrical
conductivity?
Technology
functions through
pavement?
Go to Protocol 2
Not appropriate for
further development.
Restart Go to Protocol 2
Figure 4-8. Above Ground Implementation
Section 1.4: From-the-Air Inspection of Buried Pipe
Section 1.4.1: Implementation Questions. The from the air inspection of buried pipe category has few
implementation issues as shown in the flowchart in Figure 4-9.
Is it
ecessaryto work a
slow or stationary
speeds?
Are there
conditions that limit
its use?
Yes Yes/No
V V
Consider developing as a
ground based application.
Limited use precludes
development.
Note use conditions.
Not appropriate for
further development.
Restart
Figure 4-9. From the Air Implementation
I \
Go to Protocol 2
V J
Go to Protocol 2
31
-------
Section 1.5: Combination Inspection
The combined inspection category includes technologies that may be evaluated multiple ways. An
example of a combination technology is one that has a simple non-intrusive transmitting unit in the pipe
and a robust detection system above ground. The transmitter could output acoustic or electromagnetic
energy that propagates through the pipe, soil, and pavement, and could be free swimming or on a tether.
This method would span both the inline and above ground categories, with the higher resolution generally
provided with an inline system and the simpler implementation of an above ground system. The first
category, which the technology fits in, should be chosen before repeating the process for any other
applicable technologies.
Internal Inspection
Go to Section 1.1
External Inspection
Go to Section 1.2
Above Ground
Goto Section 1.3
From the Air
Goto Section 1.4
4.2 Secondary Screening Protocol
Protocol 2 is used to determine if the structural inspection technology is capable of detecting key distress
indicators of large diameter cast iron water mains.
Section 2.0: Types of Defect Detection
The groups of key distress indicators are found in Figure 4-10 and the appropriate hyperlinks lead to the
group sections.
Section 2.0
Defect Detection
Detects
degradation that
could lead to
failure?
Detects
conditions that
could lead to
YesN Go to Section 2.1
YesW Go to Section 2.2
Detects
inferential indicators
of failure?0
Have
inspection costs
een calculated?
YesN Go to Section 2.3
/ At least
one of the 4
uestions above wa
'Yes'?
:ot appropriatefo
ther development.
Yes^Goto Protocol 3j
Go to Section 2.1 Go to Section 2.2 Go to Section 2.3 Go to Protocol 3
Figure 4-10. Defect Detection Categories
Note:
(a) Degradation includes corrosion, graphitization, cracks, or leakage.
(b) Conditions leading to degradation or failure include angled joints, and coating and lining defects.
(c) Inferential indicators of potential failure include pipe vintage, pressure variation, location and soil issues,
and cathodic protection.
32
-------
Section 2.1: Degradation Leading to a Failure
The types of degradation that could lead to a failure can be broken down into three areas (i.e., corrosion,
graphitization, or cracks in the barrel or bell, or leaks). The ability of the technology to detect one or
more of these types of degradation can be systematically characterized by completing the flowchart in
Figure 4-11.
f Section 2.1
( Detects degradation that
could lead to breakage
Detects
corrosion or
raphitization in th
barrel?
Detects
corrosion or
raphitization in th
bell?
NoWGo to Section 2.2
Corrosion in Barrel
Go to Section 2.1.1
Corrosion in Bell
Leaks
Go to Section 2.1.2 Go to Section 2.1.3 Go to Section 2.2
Figure 4-11. Degradation Defect Categories
Section 2.1.1: Corrosion in the Pipe Barrel. The flowchart in Figure 4-12 collects data about corrosion
detection in the pipe barrel.
X" Section 2.1,1 >^
f Detects corrosion in the
\^ pipe barrel,
Note the following:
1. Detection threshold (depth, diameter,
and volume).
2. How the specification was established,
Continue below.
Detection
specification for
prrosion in the pip
barrel?
Note the Ft) lowinp.:
1. If detection is a function of both length and
No> depth.
2. Minimum metal loss required to be detected,
Continue below.
Can size the
corrosion in the pipe
barrel?
Finds avg.
wall loss or signs of
deterioration?
-w Go to Section 2.1.2
Finds
potentially service
limiting wall
loss?
Note the foIlowinR;
/ Not appropriate f
1. Has a sizing specification.
further development,
2. How the specification was established
-Yes
Goto Section2.1.2
Figure 4-12. Corrosion Detection in the Pipe Barrel
33
-------
Section 2.1.2: Corrosion in the Bell. The flowchart in Figure 4-13 collects data about corrosion detection
in the bell.
/- section
Detects corrosion in the
V bell.
Note the following:
1. Detection threshold (depth, diameter,
and volume).
2. How the specification was established,
Continue below.
ection
specification for
corrosion in
the bell?
Note the following:
1. Depth/length metal loss that must be detected.
.. If detection is a function of both length and depth,
3. Minimum metal loss required to be detected.
Continue below.
Can size the
corrosion in
the bell?
Finds avg.
wall loss or signs of
deterioration?
Go to Sect ion 2.1.3
Finds
potentially service
limiting wall
loss?
Note the followine;
Not appropriate for
developme
1. Has a sizing specification.
I. How the specification was established
-Yes
Goto Section2.1.3
Figure 4-13. Corrosion Detection in the Bell
Section 2.1.3: Leaks. The flowchart in Figure 4-14 collects data about leak detection.
Section 2.1.3
Delects leaks.
dentifies if the
a k is at a joint, from a
crack, or from a hole in
the barrel?
joint leaks can lead
to joint angle change
and displacement,
Performs
botier than exist Ing
methods?
( Go to Section 2,2.1 J
Note the followins:
Go to Section 2,2
1, Detection threshold,
Z, How the specification was established.
Go to Section 2.2.1
Figure 4-14. Leak Detection
Go to Section 2.2
34
-------
Section 2.2: Conditions Leading to Degradation
The types of conditions that could lead to degradation or failure can be broken down into three areas (i.e.,
pipe angle, internal linings, and external coatings) determined by the flowchart in Figure 4-15.
S~ Section 2.2 ~\
[ Detects a condition that )
Vcould lead to degradation/
Detects
pipe angle at bell
and spigots?
Detects
defects in internal
coating?
Detects
defects in external
coating?
to Section 2.3
Pipe Angle Internal Coating External Coating Go to Section 2.3
Go to Section 2.2.1 Go to Section 2.2.2 Go to Section 2.2.3
Figure 4-15. Conditions Leading to Degradation or Failure
Section 2.2.1: Angle between Pipe Lengths at the Bell and Spigot. The flowchart in Figure 4-16 collects
data about the pipe angle at the bell and spigot.
/"" Section 2.2.1 ~~\
( Detects angle between pipe )
Mgngths at bell and spigots./
Can size
the angle between
pipe lengths?
Go to Section 2.2.2 j
^/
Note the following:
1. Detection threshold.
2. How the specification was established.
3. The specification on the measurement
(e.g., <2°; 2° to 5°; or >5°)?
Go to Section 2.2.2
Figure 4-16. Pipe Angle Between the Bell and Spigot
35
-------
Section 2.2.2: Defects in the Internal Coating. The flowchart in Figure 4-17 collects data about defect in
the internal coating.
Section 2.2.2
Detects defects in the internal coating (including
^spalling, wall thickness, and/or tuberculation).^
Sizes defects
in the internal
coating?
1. The specification on the measurement.
2. How the specification was established.
Go to Section 2.2.3
Figure 4-17. Defects in the Internal Coating
Section 2.2.3: Defects in the External Coating. The flowchart in Figure 4-18 collects data about defects in
the external coating.
Section 2.2.3
Detects defects in the external coating (including
tears, cracks and/or holidays).
Sizes defects
in the external
coating?
Note the following:
1. Type of coating (tar, zinc, poly wrap)
2. Detection threshold.
3. How the specification was established.
4. The specification on the measurement
Goto Section 2.3
Figure 4-18. Defects in the External Coating
36
-------
Section 2.3: Inferential Indicators of Failure
The inferential indicators of pipes with a higher probability of failure can be broken down into five areas
(i.e., pipe vintage, pressure variations, location issues, soils issues and cathodic protection) determined by
the flowchart in Figure 4-19. Technologies that detect water quality issues are not considered structural
inspection technologies.
/"" Section 2.3
(Indicates pipe segments that have
higher probability of failure
ave)
\J
Go to Section
Determines pipe
vintage?
Measures and
assesses pressure
variations?
Go to Section
Measures and
assesses location
issues?
Go to Section
2.3.3
Measures and
assesses potential
soil issues?
Go to Section
2.3.4
Measures and
assesses stray
currents?
Goto Section
Go to Section 2.4
Pipe Vintage
Section 2.3.1
Pressure
Section 2.3.2
Location Issues
Section 2.3.3
Soil Issues
Section 2.3.4
Stray Current
Section 2.3.5
Section 2.4
Figure 4-19. Inferential Indicators of Higher Probability of Failure
37
-------
Section 2.3.1: Pipe Vintage. The flowchart in Figure 4-20 is used to collect data about pipe vintage,
nominal wall thickness, pipe properties, or other baseline values that would help determine operational
factors.
/ Section 2.3.1 ^
\Determines pipe vintage./
Detection
specification for pipe
vintage?
Note the following:
1. If method determines pipe mill,
casting method, and or grain structure.
2. How the specification was established.
Goto Section 2.3.2
Figure 4-20. Determines Pipe Vintage
Section 2.3.2: Pressure Variations. The flowchart in Figure 4-21 is used to collect data about pressure
change.
S~~ Section 2.3.2 ~^\
(Measures and assesses water)
pressure variations.
Correlates
pressure change to
otential structural
changes?
Note the following:
1. Sensitivity and accuracy to pipe
condition changes.
2. How the specification was established.
—W Go to Section 2.3.3 )
Goto Section 2.3.3
Figure 4-21. Measures and Assesses Water Pressure Variations
38
-------
Section 2.3.3: Location Issues. The flowchart in Figure 4-22 is used to collect data about location issues.
' Section 2.3.3 ^
Measures and assesses location issues (e.g., pipe embedment,
\ surface load, wet/dry cycles, and water table). /
Correlates
location issues to
otential structural
changes?
Note the following:
1. Sensitivity and accuracy to pipe
condition changes.
2. How the specification was established.
—W Go to Section 2.3X
Go to Section 2.3.4
Figure 4-22. Assesses Location Issues
Section 2.3.4: Soil Issues. The flowchart in Figure 4-23 is used to collect data about soil issues.
f Section 2.3.4 >.
[Measures and assesses potential soil issues (i.e., soil]
type, backfill, resistivity, pH, and redox.
Correlates
soil issues to
otential structural
changes?
1. Sensitivity and accuracy to pipe
condition changes.
2. How the specification was established.
—W Go to Section 2.3.5
\ s
Go to Section 2.3.5
Figure 4-23. Assesses Soil Issues
39
-------
Section 2.3.5: Cathodic Protection. The flowchart in Figure 4-24 is used to collect data about cathodic
protection and stray currents.
"
S~ Section 2.3.5 "~~\
f Measures and assesses cathodic
^protection or stray currents.^/
Correlates
stray currents to
otential structural
changes?
1. Sensitivity and accuracy to pipe
condition changes.
2. How the specification was established.
Goto Section2.4
Figure 4-24. Assesses Cathodic Protection and Stray Currents
Section 2.4: System Cost and On-site Inspection Costs
If system and on-site inspection costs are known, the following questions can be used to determine the
relative cost grade for using and developing the technology further. Note all answers and calculate the
cost grade before moving to Protocol 3.
Section 2.4.1: What is the capital cost of an inspection system?
A. Less than $50,000
B. Between $50,000 and $200,000
C. Between $200,000 and $500,000
D. Over $500,000
Section 2.4.2: How much more capital is needed to complete the technology development?
A. Less than $100,000
B. Between $100,000 and $400,000
C. Between $400,000 and $1,000,000
D. Over $1,000,000
Section 2.4.3: How many technicians are needed on-site to apply the technology?
A. 1
B.2
C. 3
D. more than 3
Section 2.4.4: Transporting equipment?
A. Carry on or checked baggage
B. Shipping
C. Dedicated truck
Section 2.4.5: How many man days are needed to analyze one day of data?
A. Same day on-site or next day
B. Within 2 weeks
C. Within 1 month
D. More than 1 month
40
-------
Section 2.4.6: How many feet can be inspected in one day?
A. More than 10,000 feet
B. 4,000 to 10,000 feet
C. Distance between valves, nominally 2,000 feet
D. Less than 1000 feet
Section 2.4.7: What is the estimated cost to modify the pipeline for assessment? What are the
costs to return the pipeline to operation?
A. 1 day for atypical contractor, fittings around $100
B. 2 - 3 days for a typical contractor, fittings around $500
C. 1 - 2 weeks for a typical contractor, fittings around $1,000
D. More than 2 weeks, fittings more than $1,000
Section 2.4.8: What is the basis for these costs?
The answers for the eight questions above should be noted in the cost grade card shown in Table 4-3. The
scale can then be used to determine the cost factor before continuing on to Protocol 3.
Table 4-3. Cost Grade Card
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Scale:
Implementation cost Low: Mostly As and no Cs (or worse)
Implementation cost Medium: Mostly Bs with a few As or Cs (or worse)
Implementation cost High: Mostly Bs and Cs (or worse)
41
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4.3 Tertiary Screening Protocol
Protocol 3 is used to determine how the new structural inspection technology compares to existing
technologies and whether the technology has the potential for further development for application to
water mains.
Section 3.0: Types of Defect Detection
Protocol 3 begins by selecting the types of defects the technology can detect based on the answers from
Protocol 2 shown in the flowchart below (Figure 4-25).
Section 3.0
Detects barrel
defects
(from 2.1.1)?
'sWco to Section 3.ij
elects bell defects
(from 2.1.2)?
•Yes-WGo to Section 3.2
•Yes-WGo to Section 3.3]
Detects pipe angle
(from 2.2.1)?
•Yes-WGo to Section 3.4
elects coating
defects (from 2.2.2
and 2.2.3)?
•Yes-WGo to Section 3.5
Detects
inferential indicators ^>—Yes^jGo to Section 3.6
(from 2.3)?
Goto
Section 3.1
Goto
Section 3.2
Goto
Section 3.3
Goto
Section 3.4
Goto
Section 3.5
Figure 4-25. Key Defect Categories
Goto
Section 3.6
42
-------
Section 3.1: Detects Barrel Corrosion
The types of inspections for detecting barrel corrosion are outlined by the flowchart in Figure 4-26.
Section 3.1
Detects barrel defects
Permanent
internal installation
(from 1.1.3}?
Temporary
internal installation
(from 1.1.4}?
rom above groun
(from 1.3}?
Pipe is exposed
(from 1.2}?
Go to Section
Go to Section
Go to Section
3-i:3
Go to Section
Above Ground
Go to Section 3. 1.1
Pipe is Exposed
Go to Section 3. 1.2
Permanent Installation
Go to Section 3. 1.3
Temporary Installation
Go to Section 3. 1.4
Figure 4-26. Detecting Barrel Corrosion
Section 3.1.1: Barrel Corrosion, Above Ground. The flowchart in Figure 4-27 is used to determine
which approaches for detecting barrel corrosion from above ground have the potential for further
development. All cost categories are determined from Section 2.4 (see Table 4-3).
Section 3.1.1
Barrel corrosion,
above ground
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (from
2.1.1)?
Has potential for
Yes—
Vfurther development
her development
Figure 4-27. Potential for Detecting Barrel Corrosion from Above Ground
43
-------
Section 3.1.2: Barrel Corrosion, Pipe is Exposed. The flowchart in Figure 4-28 is used to determine
which approaches for detecting barrel corrosion on an exposed pipe have the potential for further
development.
Section 3.1.2
Barrel corrosion,
exposed pipe
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (from
2.1.1)?
Cost
(from 2.4)
= Medium?
. / Has potential for
c^^^j Itf
^further development.
Cost
(from 2.4)
<= High?
Not appropriate for
further development.
Figure 4-28. Potential for Detecting Barrel Corrosion on an Exposed Pipe
Section 3.1.3: Barrel Corrosion, Permanent Internal Installation. The flowchart in Figure 4-29 is used to
determine which approaches for detecting barrel corrosion using an internal device permanently installed
in the main have the potential for further development.
Section 3.1.3 "N
Barrel corrosion, )
ermanent installation]/
Provides
arning with sufficie
time to remediate
with negligible
false calls?
Has potential for
\further development
Figure 4-29. Potential for Detecting Barrel Corrosion with a Permanently Installed Internal Device
44
-------
Section 3.1.4: Barrel Corrosion, Temporary Internal Installation. The flowchart in Figure 4-30 is used to
determine which approaches for detecting barrel corrosion using an internal device temporarily installed
in the main have the potential for further development.
Section 3.1.4
Barrel corrosion,
^temporary installatio
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (fro
2.1.1)?
rther development
mplementation
easy (from 1.1.4),
cost (from 2.4)
<= Medium?
Sizes wall loss
anomalies
(from 2.1.1)?
Has potential for
further development.
mplementation
moderate (from 1.1.4)
cost (from 2.4)
<=High?
ot appropriate for
rther development
Has potential for
further
development.
Figure 4-30. Potential for Detecting Barrel Corrosion with a Temporarily Installed Internal Device
Section 3.2: Detects Bell Corrosion and Cracks
The types of inspections for detecting bell defects are outlined by the flowchart in Figure 4-31.
Section 3.2
Detects bell defects
Permanent
internal installation
(from 1.1.3)?
Temporary
internal installation
(from 1.1.4)?
rom above groun
(from 1.3)?
Pipe is exposed
(from 1.2)?
3o to Section
Go to Section \
3.2.2
3o to Section
Go to Section
Above Ground
Go to Section 3. 2.1
Pipe is Exposed
Go to Section 3.2.2
Permanent Installation
Goto Section3.2.3
Temporary Installation
Go to Section 3. 2. 4
Figure 4-31. Detecting Bell Corrosion and Cracks
45
-------
Section 3.2.1: Bell Defects, Above Ground Techniques. The flowchart in Figure 4-32 is used to
determine which approaches for detecting bell corrosion and cracks from above ground have the potential
for further development.
Section 3.2.1
Bell defects,
above ground
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (from
2.1.2)?
Has potential for \
further development. /
^ iy
-Yes
jrther development.
-No-
Figure 4-32. Potential for Detecting Bell Defects from Above Ground
Section 3.2.2: Bell Defects, Pipe is Exposed. The flowchart in Figure 4-33 is used to determine which
approaches for detecting bell corrosion and cracks on an exposed pipe have the potential for further
development.
Section 3.2.2
Bell defects,
exposed pipe
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (from
2.1.2)?
Cost
(from 2.4)
C= Medium
Has potential for
further development.
No
V
t appropriate for
her development.
Figure 4-33. Potential for Detecting Bell Defects on an Exposed Pipe
46
-------
Section 3.2.3: Bell Defects, Permanent Internal Installation. The flowchart in Figure 4-34 is used to
determine which approaches for detecting bell corrosion and cracks using an internal device permanently
installed in the main have the potential for further development.
Section 3.2.3
Bell defects,
permanent installation
Provides
arning with sufficie
time to remediate
with negligible
false calls?
t appropriate
further develoom
Has potential for
\further development.
Figure 4-34. Potential for Detecting Bell Defects with a Permanently Installed Internal Device
Section 3.2.4: Bell Defects, Temporary Internal Installation. The flowchart in Figure 4-35 is used to
determine which approaches for detecting bell corrosion and cracks using an internal device temporarily
installed in the main have the potential for further development.
Section 3.2.4
Bell defects,
temporary installatio
Finds
potentially service
limiting wall
loss?
Finds avg.
wall loss or signs o
deterioration (from
2.1.2)?
mplementation
easy (from 1.1.4)
cost (from 2.4)
<= Medium?
'Sizes wall loss
anomalies
(from 2.1.2)?
Has potential for
further development.
mplementation
moderate (from 1.1.4)
cost (from 2.4)
<=High?
ot appropriat
rther develop
Has potential for
V further development^
Figure 4-35. Potential for Detecting Bell Defects with a Temporarily Installed Internal Device
47
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Section 3.3: Detects Leaks
The types of inspections for detecting leaks are outlined by the flowchart in Figure 4-36.
Section 3.3
Detects leaks
Permanent
internal installation
(from 1.1.3}?
Temporary
internal installation
(from 1.1.4}?
rom above groun
(from 1.3}?
Go to Section
Go to Section
3-3-2
Go to Section
3.3.3
Above Ground
Go to Section 3.3.1
Figure 4-36. Detecting Leaks
Pipe is Exposed
Go to Section 3. 3. 2
Permanent Installation
Go to Section 3.3.3
Go to Section \
3.3.4 J
Temporary Installation
Go to Section 3.3.4
Section 3.3.1: Leaks, Above Ground. The flowchart in Figure 4-37 is used to determine which
approaches for detecting leaks from above ground have the potential for further development.
Section 3.3.1
Leaks,
above ground
Cost
(from 2.4)
<= Low?
Measures
leak rate and
dentifies type (fro
2.1.3)?
Has potential for \
Attaches to
rom above ground?
further development. I
t appropriate for
further development.
Measures
leak rate and
dentifies type (fro
2.1.3)?
Advantages
ower cost or better
erformance)?
Cost
(from 2.4)
<:= Medium
Cost
(from 2.4)
<= Low?
ot appropriate fo
further development
Has potential for
further development.
Figure 4-37. Potential for Detecting Leaks from Above Ground
48
-------
Section 3.3.2: Leaks, Pipe is Exposed. The flowchart in Figure 4-38 is used to determine which
approaches for detecting leaks on an exposed pipe have the potential for further development.
Section 3.3.2
Leaks,
exposed pipe
Measures
leak rate and
identifies type (fro
2.1.3)?
Cost
(from 2.4)
<= Medium?
Not appropriate for
Advantages
(lower cost or better >-Ye
erformance)?
Cost
(from 2.4)
<= Low?
Has potential for
further development.
further development
Figure 4-38. Potential for Detecting Leaks on an Exposed Pipe
Section 3.3.3: Leaks, Permanent Internal Installation. The flowchart in Figure 4-39 is used to determine
which approaches for detecting leaks using an internal device permanently installed in the main have the
potential for further development.
f Section 3.3.3
f Leaks,
Vpermanent installation^
Installed
permanently in
water main (from
1.1.3)?
Commercial technologies currently exist for
continuous leak monitoring. Does the
technology offer significant advantages to
existing technologies (lower cost or better
performance)?
Yes
Y
-No)
Not appropriate for
further development.
Has potential for
\further development./
Figure 4-39. Potential for Detecting Leaks with a Permanently Installed Internal Device
49
-------
Section 3.3.4: Leaks, Temporary Internal Installation. The flowchart in Figure 4-40 is used to determine
which approaches for detecting leaks using an internal device temporarily installed in the main have the
potential for further development.
Section 3
Leaks
temporary installatio
Measures
leak rate and
dentifies type (fro
2.1.3)?
Not appropriate for
Advantages
(lower cost or better
erformance)?
Cost
(from 2.4)
<= Low?
No
^ Has potential for
\further development./
Not appropriate for
ier developme
Figure 4-40. Potential for Detecting Leaks with a Temporarily Installed Internal Device
Section 3.4: Detects Pipe Angle
The types of inspections for detecting the pipe angle between bells and spigots are outlined by the
flowchart in Figure 4-41.
V Detects pipe angle
Temporary
internal installation
(from 1.1.4)?
Permanent
internal installation
(from 1.1.3)?
rom above groun
(from 1.3)?
Go to Section \
3.4.1 )
->. ./
Above Ground
Go to Section 3.4.1
( Go to Section \
C. ™ )
Pipe is Exposed
Go to Section 3.4.2
/ Go to Section \
v 3-4-3 )
Permanent Installation
Go to Section 3.4.3
/ Go to Section \
v 3-4-4 J
Temporary Installation
Go to Section 3.4.4
Figure 4-41. Detecting Pipe Angle
50
-------
Section 3.4.1: Pipe Angle, Above Ground. The flowchart in Figure 4-42 is used to determine which
approaches for detecting pipe angles from above ground have the potential for further development.
Section 3.4.1
Pipe angle,
above ground
^ Has potential for
\further development./
Figure 4-42. Potential for Detecting Pipe Angle from Above Ground
Section 3.4.2: Pipe Angle, Pipe is Exposed. The flowchart in Figure 4-43 is used to determine which
approaches for detecting pipe angles on an exposed pipe have the potential for further development.
Section 3.4.2
Pipe angle,
exposed pipe
^~
Cost
(from 2.4 and 1.2.3)
<= Medium?
~X
„ ./ Has potential for \
•Yesw
Vfurther development./
ppropriate for
ther development.
Figure 4-43. Potential for Detecting Pipe Angle on an Exposed Pipe
Section 3.4.3: Pipe Angle, Permanent Internal Installation. The flowchart in Figure 4-44 is used to
determine which approaches for detecting pipe angles using an internal device permanently installed in
the main have the potential for further development.
Section 3.4.3 ^X
Pipe angle, 1
srmanent installation^/
Installed
permanently in
water main (from
1.1.3)?
Retrofitting pipe for continuous monitoring
for pipe angle is not a practical approach;
consider for new pipe first. A permanent
internal device that monitors for these
events would not have much use.
it appropria
further development.
Figure 4-44. Potential for Detecting Pipe Angle with a Permanently Installed Internal Device
51
-------
Section 3.4.4: Pipe Angle, Temporary Internal Installation. The flowchart in Figure 4-45 is used to
determine which approaches for detecting pipe angles using an internal device temporarily installed in the
main have the potential for further development.
/"Section 3.4.4 X
f Pipe angle, )
\jemporary installation.
^ Has potential for
\further development.y
Not appropri
Figure 4-45. Potential for Detecting Pipe Angle with a Temporarily Installed Internal Device
Section 3.5: Detects Coating Defects
It is not likely that a water utility would only look for coating defects using a standalone system. The
method may have potential for further development if the assessment method would augment another
technology for minimal additional cost. The types of coatings that can be detected are outlined by the
flowchart in Figure 4-46.
Section 3.5
Detects coating defects
In internal coating
(from 2.2.2)?
In external coating
(from 2.2.3)?
Internal Coating
Goto Section3.5.1
External Coating
Go to Section 3.5.2
Figure 4-46. Detecting Coating Defects
52
-------
Section 3.5.1: Internal Coating Defects. The flowchart in Figure 4-47 is used to determine which
approaches for detecting internal coating defects have the potential for further development.
Focuses
detailed inspection or
augments other method,
thus increasing
value?
Has potential for
further development.
Not appropriate for
further development.
Figure 4-47. Potential for Detecting Internal Coating Defects
Section 3.5.2: External Coating Defects. The flowchart in Figure 4-48 is used to determine which
approaches for detecting external coating defects have the potential for further development.
Section 3.5.2
External coating
Focuses
detailed inspection or
augments other method,
thus increasing
value?
Has potential for
further development.
Not appropriate fo
further developme
Figure 4-48. Potential for Detecting External Coating Defects
Section 3.6: Detects Inferential Indicators
It is not likely that a water utility would only look for inferential indicators using a standalone system.
The method may have potential for further development if the assessment method could be used to focus
detailed inspections or would augment another technology for minimal additional cost. The flowchart in
Figure 4-49 is used to determine which approaches for detecting inferential indicators have the potential
for further development.
/^ Section 3.6
(Detects inferential indicators of I
yjiigher probability of failure^/
Focuses
detailed inspection or
augments other method,
thus increasing
value?
appropriate f
her developme
^ Has potential for
>> further development.J
Figure 4-49. Potential for Detecting Inferential Indicators of Failure
53
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4.4 Protocol Summary
The three protocols described herein provide agencies that could potentially fund structural inspection
technology research and development with a process for determining if promising technologies have the
potential for further development. The protocol first determines if a technology is applicable to large
diameter cast iron water mains (i.e., Protocol 1); then it determines if the technology is applicable to
detecting the key distress indicators of large diameter cast iron pipe (i.e., Protocol 2); and finally, based
on the responses from Protocols 1 and 2, it determines the potential for further development (Protocol 3).
The following section demonstrates the application of the protocols on eight technologies that could
potentially be used for structural inspection of large diameter cast iron water mains.
54
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5.0: APPLICATION OF PROTOCOLS
5.1 Overview
The purpose of this section is to demonstrate the use of the structural inspection technology evaluation
protocols outlined in Section 4. The goal is to determine if the protocol is implementable and produces
reasonable results. Four general types of both existing and emerging technologies (i.e., eight total
technologies) were examined. A brief description of each technology is provided before applying the
protocols.
An overview of the existing technologies available for structural inspection in large diameter cast iron
water mains was presented in Section 3.2. Eight technologies that have the potential to be used for
structural inspection in large diameter cast iron pipes are described below. These technologies were used
to evaluate the accuracy of the protocols by the authors based on their knowledge and the available
reference material for the proposed technologies.
5.2 Tethered Remote Field Eddy Current
Remote field eddy current (RFEC) is a commonly used NDE testing method that can be used to measure
pipe wall thickness in pipes made from various materials including cast iron (ASNT, 2004). RFEC
technology uses an alternating current (AC) electromagnetic field generated by a coil that is concentric
with the axis of the pipe. A sensor, or circumferentially distributed array of sensors, is placed near the
inside of the pipe wall, displaced from the source of the AC field wall. The through-wall nature of the
technique allows external and internal defects to be detected with approximately equal sensitivity. As the
pipe wall thickness increases, the AC frequency must be reduced to maintain comparable defect
sensitivity. However, when lower frequency signals are used, the inspection speed must be reduced
accordingly.
Tools for boiler tube inspection are readily available for small pipes less than 16 in. in diameter. Systems
for larger diameter pipe such as large cast iron greater than 16 in. are less common. For large diameter
pipes, the tools have to be long since the field source and sensors have to be separated more than two pipe
diameters.
The tool can be free swimming or tethered on a wire line. When wire line tethered, lengths up to a few
thousand feet can be inspected from one launch point, limited by the number of bends and other factors
that affect pull force. The free swimming version can inspect longer distances, and are often limited by
obstructions and water system pipe configurations.
Protocol 1: Basic Screening
Protocol 1 is used to answer whether tethered RFEC is feasible for use in large diameter cast iron water
mains. First, the suitability to large diameters and the intended capabilities are assessed as outlined in
Protocol 1. A tool has recently been built and used for inspections in a 24 in. diameter pipeline
(Nestleroth, et al, 2010). The tool is intended to detect wall thickness and thinning caused by corrosion
or erosion, as well as joint couplings, branches, and elbows. Next, the primary category from Section 1.0
is selected based on its intended use. The tool is intended to be inserted into the pipe; therefore internal
inspection (Section 1.1) is selected. The pipe does not have to be cleaned to base metal; the tool can
operate in pipes with tuberculation that does not extend into the main more than 1 in. (Section 1.1.1), and
the tool will be temporarily installed in the pipe (Section 1.1.2). Section 1.1.4 questions are answered for
use in Protocol 2 as shown in the inline applicability grade card in Table 5-1. Based on the inline
applicability grade card, the technology would be difficult to implement in water mains.
55
-------
Table 5-1. Inline Applicability Grade Card for Tethered RFEC
Question
.1.4.1
.1.4.2
.1.4.3
.1.4.4
.1.4.5
.1.4.6
.1.4.7
.1.4.8
.1.4.9
1.1.4.10
Rating
D
C
C
C
C
D
A
B
C
C
Comment
The system as proposed is pulled through the main
High accuracy RFEC needs many sensors, making the tool diameter > l/i the pipe diameter
Launch angle parallel to the pipe
Receive angle parallel to the pipe
Pipe must be cut
Pipe must be taken out of operation
Flow from branches not an issue
Large protrusions are of some concern
Butterfly valves and bends are a problem
Obstructions need to be known
Score: Implementation factor Difficult: Mostly Bs and Cs (or worse)
Protocol 2: Secondary Screening
Protocol 2 is used to determine if tethered RFEC can locate the key distress indicators for large diameter
cast iron water mains as identified in Section 2. Tethered RFEC is used to detect wall thickness which is
a form of degradation that could lead to failure (Section 2.1). The wall thickness could indicate corrosion
in the pipe barrel (Section 2.1.1). The tool has the theoretical capability to find and quantify potentially
service limiting wall loss (Section 2.1.1) and the accuracy depends on implementation factors and design
compromises needed to adapt to pipeline inspection constraints. This remote field implementation can
only examine the barrel of the pipe; hence Sections 2.1.2, 2.1.3, 2.2, and 2.3 are not applicable for this
technology. Section 2.4 determines the cost grade for the technology as shown in Table 5-2. Based on
the cost grade card, the technology has a medium cost to develop and implement in large diameter cast
iron water mains.
Table 5-2. Cost Grade Card for Tethered RFEC
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
B
A
C
C
C
C
B
Comment
Capital cost between $50,000 and $200,000
Less than $100,000 of additional developmental capital
Large tools mean more labor intensive
A dedicated truck is required
Detailed data requires a month to process
The inspection distance is the distance between valves, nominally
2,000 ft.
The cost to modify the pipeline is medium
Score: Implementation cost Medium: Mostly Bs with a few As or Cs (or worse)
Protocol 3: Tertiary Screening
Protocol 3 is used to determine if the tethered RFEC tool should or should not be developed further for
use in large diameter cast iron water mains. Since the tool is designed to detect barrel defects from inside
the main, Protocol 3 leads the user to Section 3.1.4. While the tool has the potential to detect and size
wall loss in the barrel of the pipe, the method is difficult to implement and the cost to implement is
medium. Therefore, tethered RFEC is not considered appropriate for further development for large
diameter cast iron water mains. If this technology could inspect the bell for cracks or corrosion, the
tethered RFEC may be considered appropriate for further development.
5.3
Robotic RFEC
Robotic RFEC is an untethered, remote-controlled robot for inspection of live natural gas mains. The
tools have been designed to be used for visual inspection of cast iron and steel gas mains and can be
equipped with an RFEC system to detect barrel corrosion by Carnegie Mellon's National Robotics
56
-------
Engineering Center (NREC, 2011). The robot can be launched into the pipeline under live conditions and
is designed to negotiate diameter changes, 45° and 90° bends, and tees. Like the tethered RFEC system,
tool length can be an issue for larger diameter lines. One of the benefits of a robotic system is the
inspection speed can be controlled, with higher speeds used for screening and lower speeds for detailed
assessment.
Protocol 1: Basic Screening
Robotic RFEC is suitable for cast iron pipe, but it is currently used in gas mains up to 8 in. in diameter.
The tool is intended to detect barrel corrosion while performing a visual inspection as well. The primary
category from Section 1.0 is internal inspection (Section 1.1). The tool could work in pipes with
tuberculation and sediment (Section 1.1.1), and the tool will be temporarily installed in the pipe (Section
1.1.2). Section 1.1.4 questions are answered for use in Protocol 2 as shown in the inline applicability
grade card in Table 5-3. Based on the inline applicability grade card, the technology would be moderate
to implement in water mains.
Table 5-3. Inline Applicability Grade Card for Robotic RFEC
Question
.1.4.1
.1.4.2
.1.4.3
.1.4.4
.1.4.5
.1.4.6
.1.4.7
.1.4.8
.1.4.9
1.1.4.10
Rating
C
B
A
A
A
B
A
B
C
A
Comment
The system as proposed is a robotic crawler
The tool diameter is nominally equal to !/2 the pipe diameter
Launch angle perpendicular to the pipe
Receive angle perpendicular to the pipe
Fitting can be installed while the pipe is pressurized
Line is full, but not operational
Flow from branches not an issue
Large protrusions are of some concern
Butterfly valves and bends may be a problem
Obstructions do not need to be known
Score: Implementation factor Moderate: Mostly Bs with a few As or Cs (or worse)
Protocol 2: Secondary Screening
Robotic RFEC is used to detect barrel corrosion, which is a form of degradation that could lead to failure
(Section 2.1). The tool has the theoretical capability to find and quantify potentially service-limiting wall
loss (2.1.1); the accuracy depends on implementation factors and design compromises needed to adapt to
pipeline inspection constraints. Sections 2.1.2, 2.1.3, 2.2, and 2.3 are not applicable for this technology.
Section 2.4 determines the cost grade for the technology as shown in Table 5-4. Based on the cost grade
card, the technology has a high cost to develop and implement in large diameter cast iron water mains.
Table 5-4. Cost Grade Card for Robotic RFEC
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
C
B
C
C
B
C
B
Comment
Capital cost between $200,000 and $500,000
Between $100,000 and $400,000 of additional developmental capital
Large tools mean more labor intensive
A dedicated truck is required
Onsite analysis available for identifying significant anomalies and detailed data requires a
month to process
The inspection distance is the distance between valves, nominally 2,000 ft.
The cost to modify the pipeline is medium
Score: Implementation cost High: Mostly Bs and Cs (or worse)
57
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Protocol 3: Tertiary Screening
Since robotic RFEC is designed to detect barrel corrosion from inside the main, Protocol 3 leads the user
to Section 3.1.4. The tool can size wall loss anomalies, and since implementation is moderate despite the
high cost to implement, the approach has the potential for further development.
5.4
Free Swimming Acoustics
The free swimming acoustic (FSA) inspection system is an autonomous inline system that uses miniature
electronic data acquisition systems and acoustic technology to detect and locate leaks and gas pockets in a
pipeline and to assess average wall thickness. The FSA consists of two primary components: a core with
data recording hardware and a lightweight shell for cushioning the device and propelling the unit in the
pipe. The core houses the acoustic sensors, tracking equipment, data storage equipment, and power
supply. The core is placed within the shell that can vary in diameter depending on the size, operation, and
configuration of the pipeline to be surveyed. The shell is usually less than one third of the diameter of the
pipe and can negotiate most pipeline obstructions such as valves as long as they are open.
Protocol 1: Basic Screening
Protocol 1 was used to determine if the FSA was feasible for use in large diameter cast iron water mains,
which it is. The tool is intended to detect leaks and assess pipe wall thickness. The tool is intended to be
inserted into the pipe; therefore internal inspection (Section 1.1) is selected. The pipe does not have to be
cleaned to base metal; the tool can operate in pipes with tuberculation and sediment (Section 1.1.1), and
the tool will be temporarily installed in the pipe (Section 1.1.2). Section 1.1.4 questions are answered for
use in Protocol 2 as shown in the inline applicability grade card in Table 5-5. Based on the inline
applicability, the technology would be moderate to implement in water mains.
Table 5-5. Inline Applicability Grade Card for FSA
Question
1. .4.1
1. .4.2
1. .4.3
1. .4.4
1. .4.5
1. .4.6
1. .4.7
1. .4.8
1. .4.9
1.1.4.10
Rating
A
A
A
A
A
A
D
A
B
A
Comment
The system is free swimming, propelled by water flow
Small tool diameter, can be < 6 in.
Launch angle perpendicular to the pipe
Receive angle perpendicular to the pipe
Fitting can be installed while the pipe is pressurized
Pipe can be full and operational
Flow from branches < % of the main diameter must be stopped
Protrusions are of little concern
Butterfly valves must be fully opened
Obstructions do not need to be known
Score: Implementation factor Moderate: Mostly Bs with a few As or Cs (or worse)
Protocol 2: Secondary Screening
Protocol 2 is used to determine if the FSA can locate the key distress indicators for large diameter cast
iron water mains as identified in Section 2. The FSA is used to detect leaks, which is a form of
degradation that could lead to failure (Section 2.1). The tool does not detect whether or not the leak is at
a joint, crack, or barrel of the pipe, but it has the potential to perform better than many existing methods
(Section 2.1.3). Sections 2.2 and 2.3 are not applicable for this technology and Section 2.4 determines the
cost grade for the technology as shown in Table 5-6. Based on the cost grade card, the technology has a
medium cost to develop and implement in large diameter cast iron water mains.
58
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Table 5-6. Cost Grade Card for FSA
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
A
A
B
B
B
A
B
Comment
Capital cost less than $50,000
Less $100,000 of additional developmental capital
Low labor intensive (2 technicians)
Equipment can be shipped in a container
Detailed data requires two weeks to process
The inspection distance can be more than 10,000 ft
The cost to modify the pipeline is medium
Score: Implementation cost Medium: Mostly Bs with a few As or Cs (or worse)
Protocol 3: Tertiary Screening
Protocol 3 is used to determine if the FSA should be (or needs to be) developed further for use in large
diameter cast iron water mains. Since the tool is designed to detect leaks from inside the main, Protocol 3
leads the user to Section 3.3.4. The tool locates leaks and has a cost grade less than high, so the
technology has the potential to be developed further. The development should include the capability to
detect whether a leak is a joint, crack, or in the barrel of the pipe.
5.5
Flexible Rod Sensor
Flexible rod based systems can be used to move sensors in the pipe both up and down stream of the
insertion point. Using systems similar to those used to fish or snake wires in walls in the building
industry, distances from the insertion point can be hundreds of feet. For these protocols, the flexible rod
sensor (FRS) is a tethered system that can be used for leak detection and video assessment of water
transmission mains. The system is able to determine the location of leaks and at the same time allows for
the detection of tuberculation, liner condition, and service and valve placement.
Protocol 1: Basic Screening
The FRS is suitable for large diameter cast iron pipe, and can be used on pressurized trunk mains. The
tool is intended to detect water leaks while performing a visual inspection as well. The primary category
from Section 1.0 is internal inspection (Section 1.1). The tool could work in pipes with tuberculation and
sediment (Section 1.1.1), and the tool will be temporarily installed in the pipe (Section 1.1.2). Section
1.1.4 questions are answered for use in Protocol 2 as shown in the inline applicability grade card in Table
5-7. Based on the inline applicability grade card, the technology would be easy to implement in water
mains.
Table 5-7. Inline Applicability Grade Card for FRS
Question
1. .4.1
1. .4.2
1. .4.3
1. .4.4
1. .4.5
1. .4.6
1. .4.7
1. .4.8
1. .4.9
1.1.4.10
Rating
B
A
A
A
A
A
A
A
B
A
Comment
The system is tethered
Small tool diameter, can be < 6 in.
Launch angle perpendicular to the pipe or using hydrants
Receive angle perpendicular to the pipe or using hydrants
Fitting can be installed while the pipe is pressurized
Pipe can be full and operational
Flow from branches not an issue
Protrusions are of little concern
Butterfly valves must be fully opened
Obstructions do not need to be known
Score: Implementation factor Easy: Mostly As and no Cs (or worse)
59
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Protocol 2: Secondary Screening
The FRS is used to detect leaks, which is a form of degradation that could lead to failure (Section 2.1).
The tool may be able to identify if a leak is at a joint since it works with a CCTV camera as well (Section
2.1.3). Sections 2.2 and 2.3 are not applicable for this technology. Section 2.4 determines the cost grade
for the technology as shown in Table 5-8. Based on the cost grade card, the technology has a medium
cost to develop and implement in large diameter cast iron water mains.
Table 5-8. Cost Grade Card for FRS
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
A
A
B
B
B
C
A
Comment
Capital cost less than $50,000
Less $100,000 of additional developmental capital
Low labor intensive (2 technicians)
Equipment can be shipped in a container
Detailed data requires two weeks to process
The inspection distance is the distance between valves,
nominally 2,000 ft.
Potentially no or minimal cost to modify the pipeline
Score: Implementation cost Medium: Mostly Bs with a few As or Cs (or worse)
Protocol 3: Tertiary Screening
The FRS is designed to detect leaks from inside the main, so Protocol 3 leads the user to Section 3.3.4.
The tool can measure leak rates and identify leak type, and since implementation is easy and cost to
implement is medium, the approach has the potential for further development. The development should
include verification of the system's ability to detect the location of the leak.
5.6
Magnetic Tomography
Magnetic tomography (MTM) is an emerging technology that makes magnetic measurements using
sensitive magnetometers from above ground to assess the structural integrity of the pipeline. The method
does not directly detect pipeline anomalies; rather it detects the increased level of stress caused by the
internal pressure. While data on minimum detectable flaw size are not available, for older large diameter
water mains that have wall thicknesses greater than a half inch and operating pressures less than 100 psi
(which is very low pressure for a transmission main), the corrosion size would have to be substantial to be
detected. Data are collected by a non-contact scanning magnetometer and are subsequently analyzed.
The inspection record provides the location and extent of corrosion defects and other stress risers. The
method works best on higher pressure transmission pipelines. Accuracy may be affected by either the
close proximity of other pipelines and power lines, and would have to be investigated.
Protocol 1: Basic Screening
MTM may be suitable for large diameter cast iron pipe. The tool is intended to detect wall corrosion from
the ground surface. The primary category from Section 1.0 is above ground inspection (Section 1.3). The
tool does not require electrical conductivity of the pipe and technology works through pavement.
Protocol 2: Secondary Screening
MTM is used to find stress risers, which is a form of degradation that could lead to failure (Section 2.1).
Significant corrosion in the barrel would be the most detectable anomaly, but stress in the bell due to
misalignment may also be detectable (Section 2.1.1). Section 2.4 determines the cost grade for the
technology as shown in Table 5-9. Based on the cost grade card, the technology has a medium cost to
develop and implement in large diameter cast iron water mains.
60
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Table 5-9. Cost Grade Card for MTM
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
B
B
B
B
C
D
A
Comment
Capital cost between $50,000 and $200,000
Between $100,000 and $400,000 of additional developmental capital
Low labor intensive (2 technicians)
Equipment can be shipped in a container
Detailed data requires a month to process
The inspection process is slow, rate less than 1,000 ft per day
No cost to modify the pipeline
Score: Implementation cost Medium: Mostly Bs with a few As or Cs (or worse)
Protocol 3: Tertiary Screening
MTM is designed to detect primarily average wall thickness variation; therefore Protocol 3 leads the user
to Section 3.1.1, and potentially bell corrosion (3.2.1) and effects of pipe angle (3.4.1). The tool locates
these anomalies and has a cost grade less than high, so the technology has the potential to be developed
further for large diameter cast iron water mains. One of the first steps in this development should be a
sensitivity study to determine the size of anomalies that are detectable. This method is likely to screen
pipes to determine which pipes should be excavated for detailed analysis.
5.7
Multi-Frequency Field Variation
Multi-frequency field variation (MFFV) was investigated for oil and gas pipelines to detect corrosion. It
uses a current at high and low frequencies impressed onto the pipe over typically less than a few
kilometers. An above ground magnetic field sensor array is used to detect field changes related to
anomalies in the pipeline. It was tested by some pipeline transmission companies as a screening
technique. It was reported to have merits, but not as a detailed pipeline integrity assessment method in
the same way that inline inspection is used by that industry. Therefore, it was not further developed.
Protocol 1: Basic Screening
MFFV may be suitable for large diameter pipe. The tool is intended to detect field changes related to
anomalies in the pipe from the ground surface. The primary category from Section 1.0 is above ground
inspection (Section 1.3). The tool does require an above ground electrical connection of the pipe, and
typically uses the cathodic protection systems used by oil and gas systems. Since these connections are
not common on water systems, this approach is not appropriate for further development for use in large
cast iron water mains.
5.*
MFL Inline Free Swimming Pig
Inline inspection is an integral part of many oil and gas pipeline company integrity management plans.
The most common inspection technology for both natural gas and liquid pipelines is MFL. MFL was first
used in the 1960s and was significantly improved in the 1980s and 1990s. While improvements are still
being implemented, the performance capability of MFL tools has remained relatively unchanged for a
decade. The major attribute of MFL is the ruggedness of the implementations that enable this technology
to perform under the rigors presented by the pipeline environment. This technology can locate and size
metal loss anomalies. The nominal depth sizing specification of most MFL inline tools is a tolerance of
+/-10% of wall thickness with a certainty of 80% (4 of 5 depth readings are within the tolerance). The
method can work through cement liners, but with degraded performance.
MFL tools are typically propelled through the pipeline by the product flow. Since water pipelines do not
have simple methods for inserting the tool into the pipe and retrieving the tool, application of this method
61
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could be difficult. This technology has been offered by the oil and gas company Rosen Inspection as well
as the water inspection service provider Pure.
Protocol 1: Basic Screening
MFL inline inspection may be suitable for large diameter cast iron pipe. The tool is intended to detect
wall corrosion from inside the pipe. The primary category from Section 1.0 is internal inspection (Section
1.1). The pipe would need to be cleaned to the internal coating to be used (Section 1.1.1) and the tool will
be temporarily installed in the pipe (Section 1.1.2). Section 1.1.4 questions are answered for use in
Protocol 2 as shown in the inline applicability grade card in Table 5-10. Based on the inline applicability
grade card, the technology would be difficult to implement in water mains.
Table 5-10. Inline Applicability Grade Card for Inline MFL
Question
1. .4.1
1. .4.2
1. .4.3
1. .4.4
1. .4.5
1. .4.6
1. .4.7
1. .4.8
1. .4.9
1.1.4.10
Rating
A
D
C
C
C
A
B
D
C
C
Comment
The system is free swimming, propelled by water flow
The tool diameter is nominally the pipe diameter
Launch angle parallel to the pipe
Receive angle parallel to the pipe
Fitting cannot be installed while the pipe is pressurized
Pipe can be full and operational
Flow from branches between !/2 and % of the main diameter must be
Any protrusion is of some concern
Butterfly valves and tight bends are a problem
Obstructions need to be known
stopped
Score: Implementation factor Difficult: Mostly Bs and Cs (or worse)
Protocol 2: Secondary Screening
MFL inline inspection could be used to detect barrel corrosion, which is a form of degradation that could
lead to failure (Section 2.1). The tool can find and quantify potentially service limiting wall loss (2.1.1).
Sections 2.1.2, 2.1.3, 2.2, and 2.3 are not applicable for this technology. Section 2.4 determines the cost
grade for the technology as shown in Table 5-11. Based on the cost grade card, the technology has a high
cost to develop and implement in large diameter cast iron water mains.
Table 5-11. Cost Grade Card for Inline MFL
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
C
A
C
C
B
C
C
Comment
Capital cost between $200,000 and $500,000
Less than $100,000 of additional developmental capital
Large tools mean more labor intensive
A dedicated truck is required
Detailed data requires two weeks to process
The inspection distance is the distance between valves, nominally
2,000 ft
The cost to modify the pipeline is high
Score: Implementation cost High: Mostly Bs and Cs (or worse)
Protocol 3: Tertiary Screening
Since MFL inline inspection is designed to detect barrel corrosion from inside the main, Protocol 3 leads
the user to Section 3.1.4. The tool can size wall loss anomalies, but since implementation is difficult and
the cost to implement is high, the approach is not appropriate for further development.
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5.9
Tethered MFL
While most MFL tools are typically propelled through the pipeline by the product flow, some have been
designed to work with a pull cable or tether. Some tools are based on well casing inspection tools, while
others are variations on free swimming pigs. Inspection companies have offered this as a service for
municipal water and sewer lines as well as nuclear feed water lines with large diameters. These tools
have a similar performance specification as free swimming MFL tools. Often, these tools have not been
designed to pass tight bends and obstructions.
Protocol 1: Basic Screening
MFL inline pull-through inspection may be suitable for large diameter cast iron pipe. The tool is intended
to detect wall corrosion from inside the pipe. The primary category from Section 1.0 is internal
inspection (Section 1.1). The pipe would need to be cleaned to the internal coating to be used (Section
1.1.1) and the tool will be temporarily installed in the pipe (Section 1.1.2). Section 1.1.4 questions are
answered for use in Protocol 2 as shown in the inline applicability grade card in Table 5-12. Based on the
inline applicability grade card, the technology would be difficult to implement in water mains.
Table 5-12. Inline Applicability Grade Card for Tethered MFL
Question
1. .4.1
1. .4.2
1. .4.3
1. .4.4
1. .4.5
1. .4.6
1. .4.7
1. .4.8
1. .4.9
1.1.4.10
Rating
B
D
C
C
C
B
A
D
C
C
Comment
The system as proposed will be pulled through the main
The tool diameter is nominally the pipe diameter
Launch angle parallel to the pipe
Receive angle parallel to the pipe
Fitting cannot be installed while the pipe is pressurized
Pipe can be full but not operational
Flow from branches not an issue
Any protrusion is of some concern
Butterfly valves and tight bends are a problem
Obstructions need to be known
Score: Implementation factor Difficult: Mostly Bs and Cs (or worse)
Protocol 2: Secondary Screening
MFL inline pull-through inspection could be used to detect barrel corrosion, which is a form of
degradation that could lead to failure (Section 2.1). The tool can find and quantify potentially service
limiting wall loss (Section 2.1.1). Sections 2.1.2, 2.1.3, 2.2, and 2.3 are not applicable for this
technology. Section 2.4 determines the cost grade for the technology as shown in Table 5-13. Based on
the cost grade card, the technology has a high cost to develop and implement in large diameter cast iron
water mains.
Table 5-13. Cost Grade Card for Tethered MFL
Question
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
Rating
C
A
C
C
B
C
C
Comment
Capital cost between $200,000 and $500,000
Less than $100,000 of additional developmental capital
Large tools mean more labor intensive
A dedicated truck is required
Detailed data requires two weeks to process
The inspection distance is the distance between valves, nominally
2,000 ft
The cost to modify the pipeline is high
Score: Implementation cost High: Mostly Bs and Cs (or worse)
63
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Protocol 3: Tertiary Screening
MFL inline pull-through inspection is designed to detect barrel corrosion from inside the main, so
Protocol 3 leads the user to Section 3.1.4. The tool can size wall loss anomalies, but since
implementation is difficult and the cost to implement is high, the approach is not appropriate for further
development.
5.10
Application Summary
The application of the three protocols to the eight technologies above is intended to demonstrate the
applicability of the protocols to various technologies. The two RFEC technologies had differing results
since one was considered to be more difficult to implement. Both internal leak technologies were
considered appropriate for further development, and both are currently being designed as tools for use on
large cast iron water mains. The two above ground wall corrosion detection technologies had differing
results as well. The first technology (MTM) was easily implementable on large diameter cast iron for a
moderate cost, but the second technology (MFFV) required an above ground electrical connection of the
pipe, which is not applicable on cast iron water mains. The final two technologies were both based on
MFL technology and neither was considered to be appropriate for further development as both were
determined to be difficult to implement for a high cost. A summary of the application for the eight
technologies described above is shown in Table 5-14.
Table 5-14. Summary of Protocol Application
Technology
Tethered
RFEC
Robotic RFEC
Free Swimming
Acoustic System
Flexible Rod
Sensor
Magnetic
Tomography
Multi-frequency
field variation
Free Swimming
MFL
Tethered MFL
Intended
Use
Barrel
Corrosion
Barrel
Corrosion
Leaks
Leaks
Barrel
Corrosion
Barrel
Corrosion
Barrel
Corrosion
Barrel
Corrosion
Applicability
Grade
Difficult
(1A,1B,6C,2D)
Moderate
(5A,3B,2C,OD)
Moderate
(8A,1B,OC,1D)
Easy
(8A,2B,OC,OD)
N/A
N/A
Difficult
(2A,1B,5C,2D)
Difficult
(1A,2B,5C,2D)
Cost Grade
Medium
(1A,2B,4C,OD)
High
(OA,3B,4C,OD)
Low
(3A,4B,OC,OD)
Medium
(3A,3B,1C,OD)
Medium
(1A,4B,1C,1D)
N/A
High
(1A,1B,5C,OD)
High
(1A,1B,5C,OD)
Decision
Not appropriate for
further development.
Has potential for further
development.
Has potential for further
development.
Has potential for further
development.
Has potential for further
development.
Not appropriate for
further development.
Not appropriate for
further development.
Not appropriate for
further development.
64
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6.0: CONCLUSIONS AND RECOMMENDATIONS
6.1 Summary
High-risk, large diameter cast iron water mains are very costly when they fail, creating the need to
determine how much longer these mains can safely operate. These mains are also expensive to replace
and sound pipe that is replaced significantly before the end of its service life is a waste of limited
resources. Structural inspection technologies are an important factor in determining the current and future
condition of these water mains, although inspection can be expensive. Many factors affect the
performance and value of structural inspection technologies, so organizations interested in supporting
inspection technology improvement should attempt a thorough, systematic assessment of innovative
structural inspection technology improvement options.
This report describes the most common failure modes that occur in large diameter cast iron mains and
outlines the distress indicators that could alert a utility that failure may be imminent. Technologies
currently available for detecting these indicators are briefly discussed and referenced as are organizations
funding research to develop new and innovative ways to inspect water mains. The three protocols
outlined in Section 4 are useful in screening new technologies potentially applicable to structural
inspection by determining their feasibility for water mains; applicability in detecting large diameter cast
iron water main distress indicators; and whether or not the technology should be developed further based
on its applicability and comparison with existing technologies. The strength of the protocols is the
objective process for selecting technologies for development. The weaknesses of the protocols include:
• The threshold for the rating criteria are estimates and may need to be adjusted when initially
using the protocol
• The examples use theoretical systems that may be proposed for development. The decision to
develop a system is based on the details of the system. The example may not reflect actual
systems.
• The current protocol could be strengthened by providing addition discussion and information on
the preparation and cleanup requirements for in-line inspection.
The protocols are demonstrated on eight technologies to validate the approach.
6.2 Recommendations
The authors recommend that EPA and other organizations interested in supporting the development of
structural inspection technologies use the aforementioned protocols as a screening measure to determine
if a proposed technology is applicable to large diameter cast iron mains, capable of detecting their key
distress indicators, and implementable at a reasonable cost as to be potentially used by water utilities.
This process was developed for large diameter cast iron mains as an example and can be expanded to
small diameter mains and other pipe types. The authors recommend that screening protocols be
developed for other potentially high risk mains such as large diameter ductile iron, prestressed concrete
cylinder pipe (PCCP), asbestos cement, and steel.
65
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U.S. Environmental Protection Agency. 2012b. Field Demonstration of Innovative Condition Assessment
Technologies for Water Mains: Leak Detection and Location. EPA/600/R-12/018,
U.S. EPA, Office of Research and Development, Cincinnati, OH. 184 pp.
Water Environment Research Foundation (WERF). 2004. An Examination of Innovative Methods Used in
the Inspection ofWastewater Systems. Ol-CTS-7, WERF, Alexandria, VA.
Water Environment Research Foundation (WERF). 2007. Condition Assessment Strategies and Protocols
for Water and Wastewater Utility Assets. 03-CTS-20CO, WERF, Alexandria, VA.
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Water Research Foundation (WaterRF). 201 la. Practical tool for deciding rehabilitation vs. replacement
of cast iron pipes. Project No. 4234, WaterRF, Denver, CO.
Water Research Foundation (WaterRF). 201 Ib. Acoustic signal processing for pipe condition assessment.
Project No. 4360, WaterRF, Denver, CO.
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APPENDIX A
ORGANIZATIONS FUNDING STRUCTURAL INSPECTION RESEARCH
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ORGANIZATIONS FUNDING STRUCTURAL INSPECTION RESEARCH
A.I U.S. Environmental Protection Agency.
Improving structural inspection technology capability through research and development (R&D), testing,
and verification is a proactive, flexible approach to accomplishing a number of EPA's short- and long-
term drinking water protection goals. Reducing high risk main breaks supports the Safe Drinking Water
Act (SOW A) goals of protecting public health and drinking water quality. Reducing main breaks,
optimizing maintenance planning, extending infrastructure service lives, and reducing water leakage
support the goals of EPA for reducing the infrastructure funding gap and improving utilities'
infrastructure management capability. The EPA provides avenues for structural inspection technology
R&D through the: National Risk Management Research Laboratory's (NRMRL's) Water Supply and
Water Resources Division (WSWRD); Environmental Technology Program (ETV); Small Business
Innovation Research (SBIR); Center for Environmental Industry & Technology (CEIT); Clean Water Act
(CWA); International Science and Technology Center (ITSC); and Science to Achieve Results (STAR)
grants from the Office of Research and Development (ORD) National Center for Environmental Research
(NCER).
A.2 U.S. Department of Transportation.
Under the direction of the DOT, the Office of Pipeline Safety (OPS) is the primary authority regarding the
safety of natural gas and hazardous liquid pipelines for the large amount of energy product that is
transported throughout the nation. The mission of OPS is to ensure that the operation of the nation's
pipeline system is safe, reliable, and environmentally sound. The OPS conducts and supports research to
maintain conformity with regulatory guidelines and provides tools and information regarding
maintenance to maximize the impact on pipeline safety. The research and development projects focus on
technologies for leak detection, improved system controls, prevention of damage, improvement of pipe
materials, and monitoring.
A.3 U.S. Department of Energy.
The DOE provides almost 40% of total Federal funding in the area of research for energy, biological,
computational, and environmental science. Most of the research is conducted by a variety of national
laboratories, such as the National Energy Technology Laboratory (NETL) and technology centers. The
Office of Scientific and Technical Information (OSTI) provides a searchable database that can be used to
review ongoing or completed research and a search revealed that DOE has funded some projects related
to structural inspection and leak detection in natural gas pipelines.
A.4 U.S. Department of Defense.
DoD has an in-house Research, Development, Test & Evaluation (RDT&E) program that applies basic
research and advanced development of innovative technologies. There is also the Strategic
Environmental Research and Development Program (SERDP), the corporate environmental research and
development program executed in full partnership with the DOE and the EPA. Additionally, the
Environmental Security Technology Certification Program (ESTCP) will demonstrate and validate
promising technologies that target the DoD's most urgent environmental needs through implementation
and commercialization. The result is a return on investment through savings in costs and improvement in
efficiency. Successful demonstration of such technologies helps gain acceptance from regulatory
communities and end-users. Additional avenues of research are through DoD laboratories and centers,
including the: U.S. Army Corps of Engineers (USAGE) Construction Engineering Research Laboratory
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(CERL); Army Research Laboratory (ARL); and Nondestructive Testing, Information, and Analysis
Center (NTIAC).
A.5 U.S. Department of Commerce.
The National Institute of Standards and Technology (NIST) is a non-regulatory federal agency within the
DOC's Technology Administration. The mission of NIST is to develop and promote measurement,
standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. The
two main cooperative programs used by NIST to meet their mission is the NIST Laboratories, which
conducts research to advance the nation's technology infrastructure, and the Technology Innovation
Program (TIP), which supports innovation through high-risk high-reward research in areas of critical
need. One critical area identified as part of TIP is civil infrastructure, which includes new technologies
for infrastructure inspection.
A.6 U.S. Department of Homeland Security.
Under the DHS, the Science and Technology Directorate (S&T) is the primary research and development
agency for providing leading technologies to federal, state, and local officials for the protection of people
and infrastructure from possible threats. DHS also uses the established National and Federal Laboratory
system for development and research currently used by the DOT and DOE.
A.7 U.S. Department of the Interior.
The DOI's Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) is the
federal agency responsible for overseeing the safe and environmentally responsible development of
energy and mineral resources on the Outer Continental Shelf. Under BOEMRE, the Technology
Assessment & Research (TA&R) Program supports research associated with operational safety and
pollution prevention, as well as oil spill response and cleanup capabilities. The TA&R program operates
through contracts with universities, private firms, and government laboratories to assess safety-related
technologies and to perform necessary applied research. A search revealed that one TA&R report
addressed pipeline assessment methods relating to welded steel pipelines.
A.8 National Science Foundation.
NSF is an independent federal agency created by Congress in 1950. The purpose of NSF is to initiate
and support scientific and engineering research through grants and contracts conducted at colleges and
universities. NSF acts as a central agency for the collection, interpretation and analysis for all levels of
scientific research. This information is provided to federal agencies for assistance in the generation of
policies and procedures. NSF sponsors a broad range of research in the areas of NDE, sensors, materials,
and other relevant topics. A search for applicable structural inspection systems and components
conducted using the NSF award database for those dealing with pipe and NDE inspection techniques
revealed a couple projects that could be applicable to large diameter cast iron water mains.
A.9 National Aeronautics and Space Administration.
NASA has a NDE Working Group that uses the Langley Research Center (LaRC) and the Ames
Research Center for most of its research and development of NDE technologies. LaRC leads the major
thrust of the NDE research program. The program focuses on maintaining an NDE science base core,
developing new technologies for NASA, and transferring problem solutions to their clients. LaRC
interacts with scientists, engineers, field centers, aerospace contractors, US industry, and universities.
The LaRC NDE research program is focused in two offices (Safety and Mission Quality and Aero-Space
Transportation Technology) which cover applications primarily for Space Operations/Transportation
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System (spacecraft integrity), Subsonic, Supersonic and Hypersonic Aeronautics (aircraft integrity).
There was some limited information regarding previous demonstrations, and testing of NDE technologies
that theoretically could be applied to fatigue cracking and monitoring of ferromagnetic pipes.
A.10 Water Research Foundation.
WaterRF, formally known as AwwaRF, is a member-supported, international, nonprofit organization that
sponsors research to enable water utilities, public health agencies, and other professionals to provide safe
and affordable drinking water to consumers. WaterRF sponsors a scientific research program that is
responsive to the needs of the water community by promoting the benefits of research and sharing the
results with the community. WaterRF has a close partnership with EPA and has worked on nearly 200
projects. Several research projects have dealt with the reliability of cast iron water mains and the causes
of deterioration, which have been consulted in preparation of this report.
A. 11 Water Environment Research Foundation.
WERF is a non-profit organization that funds the development of independent scientific research
dedicated to wastewater and stormwater issues. WERF operates with funding from subscribers and the
federal government. Subscribers include wastewater treatment plants, stormwater utilities, and regulatory
agencies. Industry, equipment companies, engineers, and environmental consultants also lend their
support and expertise as subscribers. WERF takes a progressive approach to research, stressing
collaboration among teams of subscribers, environmental professionals, scientists, and staff. All research
is peer-reviewed by leading experts. The majority of the research programs fall under the broad
categories of collection and treatment, infrastructure management, watersheds, ecosystems, and human
health. The WERF program relevant to this report is the Strategic Asset Management (SAM) Challenge.
The SAM Challenge seeks to evaluate and improve decision-making tools, techniques and methods to
assist utilities in implementing asset management. Research under this challenge includes projects that
have examined possible technologies for inspection and monitoring that could apply to large diameter cast
iron water mains such as research into force main inspection.
A.12 Gas Technology Institute.
GTI is a not-for-profit research and development organization that funds the development and
deployment of energy technology. GTI addresses key issues impacting natural gas and energy markets in
the areas of energy supply, delivery, and end use and provides programs and services to industry,
government, and consortia that include contract and collaborative R&D, technical services, and education
programs. One key area of natural gas delivery research is pipeline integrity management, which includes
technology research that could be applicable to large diameter cats iron main research. Included in this
focus area are technologies used for: external and internal corrosion detection, inline inspection, and
pipeline NDE such as broadband electromagnetic technology.
A. 13 Industrial Research.
Several private companies and technology vendors continuously invest in the in the development of new
technologies and improvement of existing technologies. For cast iron water mains, a recent example
includes the Pressure Pipe Inspection Company (PPIC) PipeDiver®, which uses RFEC technology to
generate magnetic currents in ferrous pipes for detection of pipe anomalies (EPA, 2001 Ib). For the same
EPA demonstration project, Russell NDE custom developed a 24-in. See Snake® RFT tool for measuring
pipe wall thickness (Nestleroth, et al., 2010). Other technologies demonstrated as part of the EPA study
included: PPIC's Sahara®' Pure's SmartBall™; Echologics' LeakfinderRT and ThicknessfinderRT;
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Advanced Engineering Solutions, Ltd. External Condition Assessment Tool; and Rock Solid Group's
Hand Scanning Kit and Crown Assessment Probe.
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