Corrosion Condition Assessments
of Force Mains
James T Lary
Corrpro
1055 W Smith Road
Medina, OH 44256
Tel: 330-723-5082 (x1215)
Email: JLary@corrpro.com
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IRON OXIDE
REFINING
IRON,STEEL,PCCP
CORROSION
MILLING
IRON OXIDE
Corrosion Process
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2
Internal & External Corrosion
of Force Mains….
H2S
Anodic Area
Solids
Buildup
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24” Ductile Iron Force Main
 Internal failure following
loss of internal mortar
lining
 Failure was along top of
pipe due to formation of
hydrogen sulfide gas
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Dual 26” Force Mains
 Internal failures at
bottom of pipe
 Failure following loss of
internal mortar lining
 Failures concentrated at
low areas (dips) in
pipeline alignment
 Cause is corrosion under
accumulated solids
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36” Above Ground Crossing
• Failure of force main
at above ground crossing
• Crown of pipe attacked
by hydrogen sulfide gas
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External Corrosion
 Caused by Aggressive
soil conditions
 Galvanic Corrosion
 Stray DC Currents
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External Corrosion Attack
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1.58 in.
1.22 in.
0.94 in.
0.87 in.
0.58 in.
1908
CLD
CI
1952
CL 150
CI
1957
CL 23
18/40
CI
1957
CL 22
21/45
CI
1976
CL 3
DI
0.43 in.
1985
CL 50
DI
0.38 in.
1991
CL 150
DI
0.21 in.
Less
Tolerances
Actual size of AWWA Specification Thickness Reductions
for 36-inch Diameter Cast and Ductile Iron Pipe - 1908 to Present
(150 PSI Operating pressure)
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Cast (Grey) Iron
Failures
Cast Iron Pipe
(thicker walled pipe)
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Ductile Iron
External pitting
(concentrated) corrosion
attack on thinner walled
ductile iron pipe.
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Temporary Fix ?
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 The rate and magnitude of corrosion depends
on a number of factors:

Pipe Material and Characteristics

Operating Conditions

Construction Methods

Environment (age not a good primary metric)

Internal or External Corrosion Attack
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Pipeline Condition Assessment Process
 Initial development driven
by federally regulated
pipeline integrity rules
#1 – Pre Assessment
#2 – Indirect Inspection
 Methodology also quite
applicable to water /
wastewater
#3 – Direct Examination
#4 – Post Assessment
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#1 Pre-Assessment:
 Define pipe segments by
construction contracts and similar
characteristics, e.g. material,
construction practices
 Identify specific locations along
the pipeline
 Air Release Points/Man ways
 Pipeline crossings
 Known area where piping
failures have occurred
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#1 -Pre-Assessment Data Gathering & Planning:




“Good listening” – operating history,
criticality, consequences of failure
Leak & Repair Records
Pipe “Bone Yard”
Coordination of Condition
Assessment Efforts With Other
Activities


Excavations
Repairs


Project construction drawings and
specifications
Pipe materials and characteristics










Wall thickness
Pressure rating
Flow Rates
Air Release points/operational status
Coatings and Linings
Bedding and backfill material
As-built documentation
Soil corrosivity, e.g. resistivity, pH,
chlorides, moisture
Adjacent utilities and crossings
Sources of stray current corrosion



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Nearby cathodic protection systems
Direct current powered transit systems
High voltage overhead AC power lines
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#2 - Indirect Inspection:
Indirect Inspection techniques:
In-Situ Soil Resistivity Measurements
 Soil Sample Collection and Analysis
 Ultrasonic Thickness Measurements (if applicable)
 Direct Examination of Exposed Pipe Sections
 Stray Current Evaluations

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#2 - Indirect Inspection:
 Integrate all data along pipeline alignment
 Analyze Data and Rank Indications:
 Severe
 Moderate
 Minor
 Select at sites for direct inspection – locations should
be where corrosion activity is most likely
 Select control site where corrosion activity is the least
likely
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#3 - Direct Examination








Excavating the pipe
Performing physical
inspection & photograph
Evaluating integrity of
coating/wrap, if present
Testing the pipe surface,
e.g. corrosion pitting
UT measurements
Measuring dimensions of
corrosion defects
Analyzing surrounding soil
/ groundwater
Performing root cause
analysis
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Force Main Pipeline Inspection Report
Inspector name_________
1) Type of Pipe: cast iron_____
Date____
Address of pipeline inspection ________________
ductile iron____ carbon steel___ copper______ carbon steel_____
2) Diameter of pipe _____” Pipeline Name_________ Service Type: Water____ Wastewater____
Leak? Yes____
No____
File Number:_____________
non metallic_____ concrete________other____
Estimated date of pipe installation______ Depth of pipe______’
3) Type of Pipe: Distribution____ Transmission____ Service_____ Hydrant _____ Mechanical joint_____ Fasteners_____
Other____
Unknown____
4) Type of Coating: Polyethylene Encased____ Shop applied coating___ No Coating____ Tape Wrap____ Unable to determine____
5) External Pipe Condition: Very Good____ Good____ Poor____
comments:____________________________________________________________________
___________________________________________________________________________________________________________________________________________
6) Ultrasonic Thickness Measurements and comment______________________________
6) Is corrosion pitting evident? ____ Yes ____ No
Number of Pits______
Internal Lining Present _____ Yes ____No comment_________________
Typical Size of Pits______
Quantity of pits:______
7) Is graphitization evident (longitudinal or circumferential breaks) ____Yes ____ No
8) Is the pipe installed in (check off appropriate items): Industrial area____ Residential area____
Rural area____
Near street or road ____
Near creek or waterway ____ In reclaimed land___ Near oil or gas pipelines____ Near high voltage lines ____.
8) Describe soil conditions where inspection occurred: wet____
dry____ clay soil ____ rocky soil____ cinders ____ other____________________
9) Where soil samples obtained, sealed and analyzed for chlorides, moisture content, pH, sulfides, resistivity? If yes results were: _____________________________
10) Were previous repairs made on the pipeline (leak clamps, etc) Yes____ No ____. Was new pipe installed____ Yes ____ No.
11) Was a repair clamp installed on the pipe during inspection ___ Yes ___ No
12) Was a galvanic anode installed as part of the inspection process? ___ Yes ___ No, if yes size and quantity
13) Please relay additional comments:
_____________________________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________________________
14) Plan of Action____________________________
15) Insert digital photos below:
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#3 - Direct
Examination:

When corrosion is found, perform
a root cause analysis

Implement localized corrosion
protection

Install instrumented test station
for future assessment of
corrosion activity, e.g. corrosion
rate probes
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#4 – Post Assessment:
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Corrosion rate
Uac
Jdc
1000
20
900
10
800
0
700
-10
600
-20
500
-30
400
-40
300
-50
200
-60
100
-70
0
17/03/06
JDC A/m2
Uac (V)
Pit growth rate and wall
thickness
 Internal or External Corrosion
 Coupons
 Electrical resistance (ER)
probes
 Maximize benefit by
 Capture ideas for improvement
 Determine need/timeframe for
update evaluations
 Identify corrective action
options

Probe-Tag: 5500 K11A-1
Probe Type: PA-0.4-10-0.1-6
Probe serial No.: PA04270025
Test initiated: 20-12-2005
AC current - A/m2
Corrosion rate micron/y
 Calculate remaining life
18/03/06
19/03/06
20/03/06
21/03/06
22/03/06
23/03/06
24/03/06
-80
25/03/06
Date
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#4 – Post Assessment Recommendations:
 Identify Corrective Options







Operational Procedures
Treatment Practices
Internal Lining
Cathodic Protection
Stray Current Mitigation
Pipeline Replacement
Pipeline Monitoring
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Program for Existing Mains
Break Reduction Life Extension Through Cathodic Protection
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Anode Lead Wire Connection
Pipe
Galvanic
Anode
Metallic Coupling
Cathodic Protection of Metallic Fitting
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Meter Vaults
(Keep dry if possible)
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Impressed Current CP System on Oil/Gas Lines can
Create Stray Current Problem on Water Lines
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Summary
 Effective management of force mains pipeline includes
understanding and managing the risk of corrosion
 A systematic approach to condition assessments results
in the most value at the lowest cost
 Retrofitting with accepted industry practice such as
internal linings, treatment programs, operational
adjustments, or cathodic protection may be a cost
effective options for extending the life of existing mains
 A key asset management strategy is to include suitable
corrosion control in the design of new force mains
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Other Structures
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Thank You
James T Lary
(330) 723-5082 ext 1215
JLary@corrpro.com
©Corrpro. All Rights Reserved.
Criteria No. 2
Approach to the Project and Methods Used to Plan, Design, and Administer the Project
Prioritizing Distribution Systems
Retail
Industry
School
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Program for Existing Mains
Break Reduction Life Extension Through Cathodic Protection
Anode Installation
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25
100 Breaks Prior to Cathodic Protection
3 Breaks After Cathodic Protection
Number of Breaks
20
15
1988 C.P.Totals
Length Protected = 12,780 feet
10
5
0
74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
Year
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Copper Service Connections
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Stray Current
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Polyethylene Encasement of Ductile Iron Pipe
-Follow DIPRA installation procedures
-Clean pipe before installing polywrap
-Repair tears or damage to encasement
-Engage an inspector to oversee installation
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Insituform
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Repair of Break Should
Include Anode Installation
Completed Repair
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Lower Stress Area
(Cathode)
Pipe
Threaded Bolt
Higher Stress Area
(Anode)
Metallic Coupling
Stress Corrosion
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Polyethylene Encasement of Ductile Iron Pipe
-Follow DIPRA installation procedures
-Clean pipe before installing polywrap
-Repair tears or damage to encasement
-Engage an inspector to oversee installation
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Force Main Recommendations
 Use coatings and cathodic
protection for external corrosion
control of steel and ductile iron
pipe
 Replace pipe at failure sites with
PVC, HDPE or fiberglass
 For long sections of deteriorated
pipe, replace with PVC, HDPE or
fiberglass, or, internally line with
cured in place polyester resin
(CIPP)
 Where metallic piping must be
used, line with ceramic epoxy.
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History of Iron Pipe
Cast Iron
- Introduced to North America during the 1800’s and
installed till the 1970’s.
- Early on, statically cast process produced a thick
walled, heavy pipe.
- No longer produced in North America.
Ductile Iron - Introduced in 1955 as an improvement to
cast iron.
- Centrifugal casting process produces a thinner
walled, lighter pipe which is stronger and
more ductile than cast iron.
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Anode Installed on Metallic Fitting
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Investigative Structure (Existing)
Corrosion Assessment
 Review of General Characteristics
of Water System
- Age
- Material Type
- Wall Thickness
- Construction Practices
 Review Break / Leak History
 Field Survey
- Soil Conditions (Resistivity,
Moisture Content, Chemical
Analysis)
- Electrical Test
 Data Analysis & Risk Management
 Priority Index (Identification of
Opportunities to Reduce
Replacement / Repair Costs)
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Effectiveness of Well Designed Corrosion Management Programs
CUMULATIVE BREAKS
1000
665 breaks
projected
without
protection
after 25 years
Cathodic Protection
applied at Year 17
94 breaks after 17 years
100
10
3 breaks after 8 years
1
0
5
10
15
20
25
30
YEARS AFTER INSTALLATION
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Value of Well Designed Corrosion Management Programs
Benefit to Cost Ratios ($ saved/ $ spent):
City of Houston, TX
8
Marin Water District, CA
9
East Bay MUD, CA - All Facilities
7
Annualized Costs – 20 Yr. Cycle
Life Extension Cathodic
Protection 58% less expensive
than continuing with repairs
$12,000
$10,000
East Bay MUD, CA - Steel Pipelines
24
$8,000
$6,000
Chicago Area Utility
25
$4,000
$2,000
$-
REPLACEMENT
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CONTINUE
REPAIRS
CATHODIC
PROTECTION
47
Existing Force Mains:
 Internal Corrosion is likely the leading cause of
main breaks
 External Corrosion may also be a factor
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#2 – Indirect Inspection:
Non-Invasive Over-the-Line Techniques
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Existing Force Mains: Condition Assessment
…need to cost effectively understand and manage
pipeline condition and operational risk…
Criticality
Scale
1
2
3
5
Objective 1:
Thorough Understanding
of High Risk Regions
5
Condition
4
4
3
2
Objective 2:
Cost Effective
Field Evaluation
1
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The four fundamental elements of a successful
coating system involve:
1.
2.
3.
4.
Material Selection
Specification
Application
Inspection
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Technologies





Material Selection
Protective Coatings
Cathodic Protection
Stray DC Current Control
AC Interference Mitigation
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24” DIP
 Multiple failures at Buffalo
Bayou on bottom of pipe
 Performed ultrasonic
thickness measurements
in lift station
 Cases of failure are
scouring and turbulent
flow
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Force Main Corrosion Mechanisms
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30” Ductile Iron
 Internal corrosion
failure at crown of
pipe.
 Hydrogen sulfide gas
formed sulfuric acid
which attacked the
mortar coating and
then the underlying
metal surface.
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H2S & Silt Accumulation May Cause
Internal Corrosion Problem….
H2S
SILT
ACCUMULATION
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Piping Inspection Phases
1. Identification of Problem
or High Consequence
Areas
2. Field Study/Inspection
3. Post
Assessment/Identify
Corrective Options
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Accurate leak records are an invaluable predictive tool
CUMULATIVE BREAKS
1000
665 breaks
projected
without
protection
after 25 years
100
94 breaks after 17 years
10
3 breaks after 8 years
1
0
5
10
15
20
25
30
YEARS AFTER INSTALLATION
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#2 – Indirect Inspection:
Data Integration for Non-Invasive Over-the-Line Techniques
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#2 - Indirect Inspection:
Available decision-assisting tools, among others:
 DDMTM – Risk-based “Design Decision Model”
 MTCFSM – “Mean Time To Corrosion Failure”
Predictive Model
C
O
N
S
E
Q
U
E
N
C
E
DDMTM
LIKELIHOOD OF CORROSION
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#3 - Direct Examination:








Excavating the pipe
Performing physical
inspection
Evaluating integrity of
coating/wrap, if present
Ultrasonic Testing of the pipe
surface
Measuring dimensions of
corrosion defects
Analyzing surrounding soil /
groundwater
Obtain coupon
Performing root cause
analysis
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24” DIP & Steel
 Internal pipe failures
along crown of pipe
 Failures following loss of
internal mortar lining
 Cause is formation of
hydrogen sulfide gas
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#3 - Direct Examination:
Procedures for data collection
 Physical Examination
 Photographic Documentation
 Pipe-to-Soil Potential Measurements
 Bi-metallic Connections, e.g. services
 Soil, Bedding, Backfill and Groundwater Tests
 Coating Assessment (if applicable)
 Mapping and Measurement of Corrosion Defects
 Ultrasonic Thickness Measurements
 AC and DC Stray Current Measurements
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