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Pipelines 2017
Technology for Assessing the Condition of Your Pipelines: Two Decades in the
Allison Stroebele1 and Anna Lee2
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Pure Technologies U.S. Inc., 8920 State Route 108, Suite D, Columbia, MD 21045.
Pure Technologies Ltd., 5055 Satellite Drive, Unit 7, Mississauga, Ontario, L4W
5K7. E-mail:
In the 1990’s the failure of Prestressed Concrete Cylinder Pipes (PCCP)
became more common and owners looked for solutions. At the time, options were
limited and owners were often faced with full-scale pipeline replacement. This need
was further fueled by the catastrophic nature and impact of the failures combined
with public pressure for action. As budgets tightened and pipelines continued to age,
the need for a better way to evaluate and manage these pipelines became apparent.
This eventually led to many changes in the industry including the development of
several condition assessment tools, technologies and techniques. Today, owners have
access to a wide variety of options for condition assessment tools, technologies and,
in combination with asset management, can make informed decisions and manage
pipelines more efficiently and effectively.
Electromagnetics for the assessment of PCCP was among the first of the
technologies developed for inline assessment of water pipelines. On-going
developments have produced an array of inline inspection tools using
electromagnetics including physical entry carted applications, free-swimming tools
and robotics platforms. Testing, research and experience in the data collection,
analysis methodologies, and calibration and verification exercises have further
improved the understanding of the data. Recent advances have been made in the
technologies for their application and use in metallic pipelines.
This paper reviews the advancements in electromagnetic inspection platforms
and analysis techniques on PCCP and the eventual adoption of the technology for
metallic pipes. It will include a historical look at the industry and the possible future
PCCP is a common material found in the construction of water and wastewater
pipelines in North America. The earliest application of PCCP in the United States was
in 1942 (AWWA C301-99 Foreword). Various studies report that over 19,000 miles
have been produced in the United States (WRF Report 91214 2008). Catastrophic
failures of PCCP, beginning the 1970’s and continual increase into to the 1990’s,
drove owners to look for proactive solutions. The most common failure mode of
Pipelines 2017
Pipelines 2017
PCCP is due to prestressing wire breaks. The cause of wires breaks can be due to
several factors including, manufacturing, installation, operation and environment.
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By the early 1980’s owners began using over-the-line potential surveys to identify
areas of increased likelihood of corrosion. In the mid-1980’s, Robert Price, while
investigating PCCP failures hypothesized that longitudinal cracking of the concrete
core would precede failures. This finding in combination with the discovery of
“hollows”, indicating core delamination, formed the practice of Visual and Sounding
inspection as a proactive measure of PCCP condition assessment to identify pipe
sections that are at risk of failure. Acoustic sensors were used as early as 1989 for
monitoring and identifying wire breaks in PCCP at the Washington Suburban
Sanitary Commission (WSSC) and through the Bureau of Reclamation at the Central
Arizona project.
The first known tests using electromagnetics on PCCP were in 1990 at WSSC and the
Schlumberger Well system. (Lewis, 2003) By 1994, research was being conducted at
Queen’s University led by Professor A. L. Atherton with the Applied Magnetics
Group, to use electromagnetics to detect the broken prestressing wires in PCCP. The
Pressure Pipe Inspection Company was established in 1997 to commercialize the
university’s efforts. The technology was further advanced and understood through an
AWWARF study conducted from 1998 to 2000 and focused on embedded cylinder
PCCP. The study verified that the remote field eddy current/transformer coupling
inspection technology was able to detect broken wires, resolve multiple regions of
broken wires, demonstrate that the size of signal showed strong and direct correlation
to number of broken wires and predicted number of wire breaks with calibration.
(AWWARF #2564)
Rapid early adoption of this method of condition assessment followed and within five
years the technology was widely accepted. (Mergelas, 2001) By 2001, 19 utilities had
used the RFEC/TC technology and a totaling 500 km (300 miles) of pipe inspected
ranging from 36-inches to 252-inches in diameter. Some of the early adopter utilities
that helped to establish and advance this technology included; WSSC, Dallas Water
Utilities, Tarrant Regional Water District, San Diego County Water Authority,
Metropolitan Water District of Southern California, APS and the Central Arizona
The original platform used for inspection was a cart that was pushed manually
through the pipeline. This allowed a detailed visual and sounding inspection to
supplement electromagnetics data collected. This method required full dewater and
confined space entry for personnel into the pipeline. This is not without its
disadvantages; safety concerns for people in the pipe exists and dewatering is a
disruptive and costly undertaking. Through further innovation other platforms were
developed. In 2001, bicycle based carts were introduced to allow easier access to
smaller diameter pipelines. By 2005, pipe crawlers with video were used to eliminate
the need for personnel entry on short distance inspections. The cart, bike and crawler
platforms are shown in Figure 1, respectively.
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Pipelines 2017
Figure 1. Different
Eleectromagnetiic Inspectionn Tools
Onee of the bigg
gest advancees in the tecchnology cam
me in 2007 when a freee-swimming
verrsion of the tool
becamee available as
a seen in Fiigure 2. This tool was ffirst used in
Hallifax, Canad
da in Decemb
ber of 2007. The tool waas able to insspect the pippe while the
system remain
ned in serviice, eliminaating the neeed for proolonged shuutdowns or
watering. Th
he tool wass neutrally buoyant
andd flexible, aallowing naavigation off
nds, tees and
d inline valvee. The availaability of thiss tool alloweed many utillities access
to condition assessment th
hat had beeen previous ly unavailabble due to operational
nstraints of th
heir pipelinee.
Figure 2. Free-Swim
mming Electrromagnetics Tool
Pure Technologie
es establisheed a competiing technoloogy called P
P-Wave that
In 2003,
useed electromaagnetics to detect
wire breaks
in PC
CCP pipes. They offereed a similar
tool that utilizeed a cart pusshed manuallly in the pippeline to carrry the electtromagnetic
uipment. An
n advanced robotics un
nit was addeed to the ccompany’s pportfolio off
elecctromagneticc inspection tools in 200
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Thee two com
mpanies con
ntinued to innovate and advannce their teechnologies
dependently until
2010 when,
gh an acquiisition, they became onee company.
Thiis has allow the shared knowledge
nd expertise to further addvance the ttechnology.
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me accepted aas best practtice in the inndustry and
By 2012, electrromagnetics had becom
ommended for conditio
on assessmeent on highh criticality PCCP (W
WRF, 2012).
pical PCCP assessment projects com
mbine leak detection, eelectromagneetics, visual
d sounding inspections to understtand the baaseline conddition of thhe pipeline.
vanced prog
grams add permanent acoustic moonitoring syystems to iddentify and
locaate wire breaaks trends on
n an ongoing
g basis.
Thee combined experience has contribu
uted in buildding the sinngle largest database off
elecctromagneticc condition assessment results avaailable in thhe industry. More than
4,500 km (2,80
00 miles) off PCCP pipeelines have bbeen inspectted in the paast 20 years
ng these too
ols. Included
d in this totall are a numbber of reinsppections thatt have been
mpleted for various utiilities. The experience extends to utilities frrom several
diffferent counttries, howev
ver, predom
minantly the United Staates and Caanada. The
longest inspecttion perform
med to date was nearlyy 112 km ((70 miles) llong in the
ople’s Repub
blic of Chinaa. The averaage inspectioon length is approximateely 4 miles.
Ressults of electtromagnetic inspection in
i Canada annd US indiccated approxximately 4%
of the
t total pipe sections in
nspected hav
ve any levell of wire breeak damage (Semanuik,
06) and lesss that 1% reequire repairr or rehabil itation (Higggins, 2012) which has
chaanged industtry perceptio
on of this ty
ype of pipe. The summaary of miles of pipeline
pected using
g electromag
gnetics per yeear is shownn in Figure 3.
Figure 3 PCCP Insp
pected per Year
Y using E lectromagneetic Technoloogy
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Pipelines 2017
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uch time and energy iss needed to research annd develop new technoologies and
vance existin
ng ones. Th
his is particularly truee for technoology that operates in
pressurized piipeline. Thee environm
ment inside a pipelinee can be harsh and
predictable. Many unkn
nowns existt and manyy assumptioons during the design
ocess must be
b made. Some unknowns exists due to lackk of docum
mentation off
pipeline config
gurations succh as the loccation, statuus and type of inline vaalves. Other
knowns stem
m from the lack of kn
nowledge o f flow condditions, pressures, and
haviors in pressure pipess. Testing faccilities can oonly simulatee a small sam
mple of real
worrld condition
ns and confiigurations. The
T combinaation of diam
meter, pipe ddesign, pipe
type, configuraation, operatiion and watter type are ttoo numerouus to simulaate. Lessons
learrned and utility feedback during ong
going inspecctions promoote constantt innovation
d improvemeents.
Thee product liffe cycle of a technology
y begins witth a proof oof concept oor prototype
thatt is refined and
a improveed through th
he phases off introductionn, growth, m
maturity and
finaally declinee. Figure 4 below shows
the first prooff of conceept of the
elecctromagneticcs cart in 19
996. Pictureed with the cart is Xianngjie Kong, one of the
hnologies orriginal inven
ntors. On thee right of Figgure 4 is thee current verrsion of the
nual electrom
magnetic too
Figure 4.
4 Example of
o Progress from
Proof of Concept too Advanced Tool
vancements to the technology can
n take variious forms. Field expeerience and
dback often
n drives chaanges to th
he mechaniccal design of the equiipment, for
exaample, the ab
bility to operrate in harsh
h condition, be assembleed quickly annd navigate
nds or valvees. Calibratio
ons and valiidations helpp to inform and advancce the tools
elecctronics and
d analysis tecchniques. While
the tecchnology as a whole is pproprietary,
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Pipelines 2017
many components of the systems that are considered “off the shelf”. The continual
advancement of these components, such as memory cards, batteries and computers,
both allow and necessitate constant evolution of the technology. Here are a few
examples of recent developments in the delivery of the electromagnetics technology.
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Recent advancement in the free-swimming electromagnetics tool has seen the
adoption of the technology in metallic pipelines. Electromagnets can be used
to identify, quantify and locate areas of wall loss in steel and ductile iron
pipelines. Electromagnetics has been in the oil and gas industry for assessing
metallic pipelines since the 1950’s and the first use in the water industry
occurred in the 1990’s.
Upgrades to the detector electronics have been made in recent years to
improve data quality when in proximity to high voltage power lines. Often at
power plants and occasionally in transmission or force mains, high voltage
power lines interfere with the electromagnetic signal created by the inspection
equipment and result in noisy or unusable data. In response to this problem,
developments were made to the detectors to allow for electronic
configurations that reduce or eliminate any interference from external power
Pipeline location accuracy is an important part of delivering inspection results.
Finding the right pipe and digging in the right location isn’t always easy. To
make this process more accurate when locating results based on the freeswimming tool, locating units were developed that do not need direct access
to the pipeline. Traditional tracking methods require direct contact with the
pipeline, however, some transmission mains and most force mains to do have
many access points. This new locating unit sits on the ground above the pipe.
During post-processing of the data, these units improve the accuracy of
locating damaged pipe sections.
60-inch Embedded Cylinder PCCP
All technologies have limitations and it is important to understand these limitations
and challenges before embarking on a condition assessment inspection. By
understanding the limitations of the technology, engineers can make informed
decisions when managing their PCCP. This case study shows an example of a
limitation of electromagnetic tools and how this understanding prompted the correct
course of action.
An 11 km (7 miles) of a 60-inch embedded cylinder PCCP water transmission main
was inspected two times over a six year period as part of a condition assessment
program. The pipe was inspected using a manually operated electromagnetics cart in
conjunction with a visual and sounding inspection. In November 2009, 25 broken
wire wraps were identified in two regions of the pipe. During a second inspection in
Pipelines 2017
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ne of 2016, a total of 40
0 broken wiire wraps weere identifieed. A new reegion of 15
oken wraps had
h developeed since the 2009
In 2016
the pip
pe was excav
vated and reeplaced. Desstructive testting of the ppipe section
ntified 63 brroken wire wraps
as shown in Figuure 5 below. The numbers indicate
the quantity of broken wiree wraps and the
t red shadiing the apprroximate possition.
Figure 5.. Reported vs Actual Brooken Wire W
Figure 6. Corroded an
nd Broken P
Prestressing W
Acccurate quanttification of broken wirees depends oon many facttors, some eexternal and
is based
on exp
pert judgemeent by the daata analyst. T
The results ttypically yieeld the right
nagement deecision when made with
h the undersstanding of the technoloogy. In this
case, the underr quantificatiion of wire breaks
occurrred in the rregion next tto the joint.
o wire break
ks in the regiion next to thhe joint is a kknown limittation of the
Identification of
hnology. Th
he joint rin
ng of the pipe
sectionn causes a large respoonse in the
elecctromagneticc signal and masks the signal
brokeen wires wouuld make in this region.
owing this, when
a regio
on of broken
n wires is ideentified adjaacent to the joint region,
a co
onservative approach assumes that all
a wires aree broken in th
this area andd the correct
gineering jud
dgement wass applied to replace
the ppipe section.
nt Mortar Lined
Steel Water
32--inch Cemen
In April
2016, a 2.75 km (1.7 miles) stretch of 8 15 mm (32--inch) steel water main
wass inspected using a freee-swimming electromaagnetic insppection tool. Four pipe
sections in weree identified as
a having arreas ranging between 30%
% and 60% wall loss as
Pipelines 2017
Pipelines 2017
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seen in Figuree 7. Three of
o the four locations w
were excavaated for valiidation and
posssible repairrs. Location #1 was no
ot able to be excavate due to proxximity to a
roadway and th
he presence of
o trees.
gure 7. Overv
view of Inspection and E
Electromagnnetic Results
3 and location #4 were similar. Insspection resuults showed
Thee findings att location #3
smaall anomaliees at the in
nvert of the pipe with approximateely 30% waall loss. At
locaation #3, sho
own in Figu
ure 8, approx
ximately 25%
% wall loss was identified using an
ultrrasonic thick
kness gaugee at the inv
vert of the ppipe. At loccation #4, w
wall loss off
proximately 35% was meeasured at th
he invert.
Figure 8. Locatio
on #3 Electro
omagnetic D
Data and Fielld Validationn
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Pipelines 2017
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Loccation #2 yieelded a someewhat unexp
pected but usseful result. T
The data, whhen initially
anaalyzed appeaared to show
w wall loss att the crown of the pipeliine. When thhe pipe was
exccavated, a welded
in plaace patch was
w discovereed. Althouggh not exactlly what the
utillity was look
king for, they
y were happy to find an unknown reepair on the ppipe, which
wass potentially
y at higher rissk of failure. Video coll ected duringg the inspecttion showed
thatt the mortar lining appeaared to be missing at thiss location.
Figure 9. Location #2 Electrom
magnetic Datta and Excavvation Findinngs
72--in Non-cylinder PCP Failures
d Validation
On January 8, 2016, an ellectromagneetic inspectioon was com
mpleted along a 2.6 km
6 mile) strettch where a 72-inch non
n-cylinder ppipeline had recently expperience its
firsst major faailure. The results of
o the insppection idenntified 18 pipes with
elecctromagneticc anomalies indicative of
o broken w
wire wraps. A second m
major failure
occcurred on Jan
nuary 11, 20
015 shortly after refillinng the pipeliine at a locaation where
the electromagn
netic scan haad previously
y identified a large wire related anom
Figure 10. Firrst (left) and
d Second (rigght) Failure L
ures promptted the repaiir of 8 addittional pipes where largee anomalies
Theese two failu
d also been identified.
A the time of this inspeection, areass of broken wire wraps
d been reporrted qualitattively as sm
mall, medium
m or large ddue to the abbsence of a
caliibration curv
ve applicablee for 72-inch
h non-cylindder prestresseed concrete ppipe.
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Figure 11. Cracking an
nd Corrosion
n on a Pipe R
Reported witth Large Anoomalies
Aftter the repairrs were com
mpleted, the inspection sccope was furrther expandded to cover
27 miles of pip
pe in Februaary 2016. The
T results oof this new inspection sshowed two
ncentrated regions
of pipes with medium aand large aanomalies. A closer
exaamination off these locatiions showed
d that one off the sites haad salty wateer routinely
spriinkled on th
he soil over the pipe. The
T other sitte had suspeected overlooading from
dustrial equipment driviing over th
he pipe witth no encassement. Thhe findings
ompted the design
of a parallel
pipelline using 7 2-inch steel at the two llocations off
ncentrated an
Figure 11. Two Conceentrations off Pipes with M
Medium andd Large Anoomalies
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uipment Im
mprovementts to Elimina
ate Signal In
nterferencee from Poweer Lines
Reccent upgrad
des to the electronics
within the detector asssemblies haave greatly
proved the quality of data collected from pipeline innspections nnear power
nsmission lin
nes. High vo
oltage poweer lines can create signaal interference and as a
ult comprom
mise the eleectromagnetiic data nearr the pipe jooints. There have been
merous reviisions to th
he detector design oveer the yearss. Howeverr, the most
pactful updaates involved
d a change in
i the gain ccontrol strattegy and finne tuning off
filteers to elimin
nate the inteerference caaused by pow
wer lines. The newestt version off
deteector has beeen used succcessfully to
o rescan a seection of pippeline that w
was affected
by nearby pow
werlines in Arizona.
As shown in F
Figure 12, a region of bbroken wire
wraaps that wass masked usiing an olderr version of the detectorrs can be cleearly seeing
with the new veersion of dettectors.
Figure 12. Data Comp
parison Usin
ng Old (left) and Updatedd (right) Dettectors
veloping, reefining and advancing technologyy can take years (decaades!), and
requires effort from both providers
d utilities. P
Proactive utillities play ann important
parrt in technollogy develop
pment by participating in trials, prroviding feeedback, and
ding acceptance of vallidated techn
nology. Thee use of eleectromagnettics for the
ndition assesssment of water
pipelinees has seen significant advancemennts over the
passt two decad
des. From th
he first application on em
mbedded cyylinder PCCP
P to current
pabilities including non-ccylinder pipee, non-shortiing strap pippe, ductile, stteel and bar
wraapped pipe. From a prottotype cart to
t the currennt array of pplatforms raanging from
botics to free swimming tools.
provements can be co
onceived th
hrough ideaas and need from cliient, onsite
hnicians, ressearch teamss, sales peop
ple, data anaalysts or maarketing. Deevelopments
get improvin
ng different aspects
of th
he technologyy such as increasing thee sensitivity,
proving usaability, increeasing robu
ustness or bbroadening the applicaation range.
pabilities can
n be added through
utiliization of neew sensors too collect moore or better
dataa. So, what’s next? Pipeelines will co
ontinue to aage, the needd for more efficient and
geted metho
ods of manag
ging pipelin
nes will incrrease and brring more oppportunities
for new solutions and techn
Pipelines 2017
Pipelines 2017
American Water Works Association (1999). C301-99: AWWA Standard for
Prestressed Concrete Pressure Pipe, Steel-Cylinder Type. Foreward. 1999
Water Research Foundation (2008). Failure of Prestressed Concrete Cylinder Pipe.
Report 91214 2008. 53-60
Downloaded from by University Of Florida on 10/25/17. Copyright ASCE. For personal use only; all rights reserved.
Lewis, R. A. and Wheatly, M. (2003) Prestressed Concrete Cylinder Pipeline
Evaluation, A Toolbox Approach. ASCE Pipelines. Pipeline Engineering and
Construction International Conference, July, 2003. Baltimore, MD, United States
Mergelas, B. and Kong, X. (2001) Electromagnetic Inspection of Prestressed
Concrete Pressure Pipe. AWWA Research Foundation, Project #2564, 2001
Water Research Foundation (2012). Best Practices Manual for Prestressed Concrete
Pipe Condition Assessment: What Works? What Doesn’t? What’s Next? Chapter 7.
Semanuik, S. and Mergelas, B. (2006) Comparison of Identified Distress in CCP
Pipelines Operated by Water Utilities in North America. ASCE: Pipeline Division
Specialty Conference August, 2006. Chicago, IL, United States
Higgins, M., Stroebele, A. and. Sahidi, S. (2012) Numbers Don’t Lie, PCCP
Performance Based on a Statistical Review of a Decade of Condition Assessment
Data. ASCE Pipelines Conference. August 2012. Miami, FL, United States
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