U.S. patent application number 10/093620 was filed with the patent office on 2003-09-11 for system and method to accomplish pipeline reliability.
Invention is credited to Pittalwala, Shabbir H., Wittas, Daniel J..
Application Number | 20030171879 10/093620 |
Document ID | / |
Family ID | 29548099 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030171879 |
Kind Code |
A1 |
Pittalwala, Shabbir H. ; et
al. |
September 11, 2003 |
System and method to accomplish pipeline reliability
Abstract
A system and method is disclosed for facilitating the management
of pipeline reliability, maintenance, repair, and/or replacement.
Embodiments may be computer-implemented, and may be suitable for
prestressed concrete cylinder pipe (e.g., PCCP). Method steps
include inspecting the pipe and storing or inputting design and
inspection parameters, as well as the maximum expected pressure
within the pipe. A relation of pressure versus degradation (e.g.,
number of broken wires) may be used, which may have zones of risk
or classifications corresponding to pipe management actions. The
pipe may be analyzed for lack of prestress over various portions of
circumference and length. The pipe rupture pressure, crack onset
pressure, or can rupture pressure may be analyzed and compared to
the expected pressure. The method may be tested and the inspection
repeated while tracking changes. The action may involve, for
instance, doing nothing, monitoring the pipe, repairing the pipe,
or replacing the pipe.
Inventors: |
Pittalwala, Shabbir H.;
(Litchfield Park, AZ) ; Wittas, Daniel J.;
(Phoenix, AZ) |
Correspondence
Address: |
SNELL & WILMER
ONE ARIZONA CENTER
400 EAST VAN BUREN
PHOENIX
AZ
850040001
|
Family ID: |
29548099 |
Appl. No.: |
10/093620 |
Filed: |
March 8, 2002 |
Current U.S.
Class: |
702/34 |
Current CPC
Class: |
F17D 5/00 20130101 |
Class at
Publication: |
702/34 |
International
Class: |
G06F 019/00 |
Claims
what is claimed is:
1. A method of facilitating the determination of whether to take
pipe management action, the method comprising, in any order, at
least the steps of: acquiring a first parameter, the first
parameter being a design parameter for the pipe; inspecting the
pipe at least a first time; acquiring a second parameter, the
second parameter being an inspection parameter comprising at least
an evaluation of the structural integrity of the pipe; acquiring a
third parameter, the third parameter comprising at least a pressure
within the pipe; and using at least a relation of the evaluation of
the structural integrity of the pipe and the pressure within the
pipe, facilitating a determination of whether or not to take pipe
management action.
2. The method according to claim 1: the pipe having a diameter; the
first parameter comprising at least the diameter of the pipe; the
pressure within the pipe being substantially a maximum pressure
anticipated within the pipe in future service; the method further
comprising at least a step of facilitating a determination of when
to take pipe management action.
3. The method according to claim 1 further comprising at least the
steps of: waiting until the next time to inspect; inspecting the
pipe at least a second time; and acquiring at least a fourth
parameter, the fourth parameter being an inspection parameter
comprising at least an evaluation of the structural integrity of
the pipe at the second time.
4. The method according to claim 3 further comprising at least the
step of: calculating a degradation rate of the pipe; the
degradation rate being determined from the difference in the
structural integrity of the pipe from the first time to the second
time.
5. The method according to claim 4: the pipe being prestressed
concrete cylinder pipe; the second parameter comprising at least a
quantity of broken wires; and the method further comprising at
least the step of using the degradation rate of the pipe,
calculating when the pipe should be repaired or replaced.
6. The method according to claim 5, said inspecting comprising at
least eddy current inspection.
7. The method according to claim 1: the pipe being prestressed
concrete cylinder pipe, and the second parameter comprising at
least a quantity of broken wires.
8. The method according to claim 1, the pipe management action
being selected from the group consisting of repairing, replacing,
and monitoring the pipe.
9. The method according to claim 1, said inspecting comprising at
least eddy current inspection.
10. The method according to claim 1, said inspecting comprising at
least ultrasonic inspection.
11. The method according to claim 1, said inspecting comprising at
least visual inspection and sounding.
12. The method according to claim 1: the relation being embedded
within a computer program; and the relation having at least a
plurality of zones of risk.
13. The method according to claim 1 further comprising at least the
step of testing the method over time to verify that it works.
14. A system for facilitating a determination of whether to take
pipe management action, the system comprising at least: a relation
of pressure versus a quantification of the degradation of the
structural integrity of the pipe; said relation being at least one
of: a physically-viewable graph, an algorithm stored within a
computer, and data stored within a computer; and said relation
having at least:: a zone of higher risk, and a zone of lower
risk.
15. The system according to claim 14, the pressure being maximum
anticipated pressure within the pipe.
16. The system according to claim 14, the relation further having
at least a zone of medium risk, the zone of medium risk being
between the zone of higher risk and the zone of lower risk.
17. The system according to claim 14, the pipe being prestressed
concrete cylinder pipe.
18. The system according to claim 17, the quantification of the
degradation of the structural integrity of the pipe comprising at
least a quantity of broken wires.
19. The system according to claim 18, the relation further
comprising at least the anticipated pressure for the ultimate
strength of the cylinder.
20. The system according to claim 14: the pipe comprising at least
a concrete core; and the relation comprising at least: the
anticipated rupture pressure of the pipe; and the pressure
anticipated to cause the concrete core to crack.
21. The system according to claim 20, the relation further
comprising at least: an action pressure; the action pressure being
less than the anticipated rupture pressure of the pipe; and the
action pressure being greater than the pressure anticipated to
cause the concrete core to crack.
22. A method of facilitating the management of a pipeline, the
pipeline comprising at least a plurality of sections of prestressed
concrete cylinder pipe, the method comprising, in any order, at
least the steps of: storing design data for each of at least a
plurality of the sections, the design data comprising at least one
dimension of each section; inspecting at least a plurality of the
sections, said inspecting comprising at least evaluating the
quantity of failed wires within the sections; estimating the
maximum pressure that is likely to exist in future service within
each of at least a plurality of the sections; using at least the
design data, the quantity of failed wires, and the maximum
pressure, designating a classification for the condition of at
least a plurality of the sections; and implementing pipe management
action based on at least one classification.
23. The method according to claim 22, the design data further
comprising at least external loading on at least one of the
sections.
24. The method according to claim 22, said inspecting being
repeated at different times, the method further comprising at least
the step of tracking changes in the quantity of failed wires over
time for at least a plurality of sections.
25. The method according to claim 25, each classification having a
corresponding action, the method further comprising at least the
steps of: calculating the rate of wire failures for at least a
plurality of the sections; and predicting when at least one of the
sections will enter another classification.
26. The method according to claim 22, the action being selected
from the group consisting of: monitoring the section, repairing the
section, and replacing the section.
27. The method according to claim 22, each classification having a
corresponding action: the method comprising at least two
classifications, the two classifications being a first
classification and a second classification; the action
corresponding to the first classification being doing nothing to
the section, at least until the next inspection; and the action
corresponding to the second classification being selected from the
group consisting of: repairing at least the section and replacing
at least the section.
28. The method according to claim 22, each classification having a
corresponding action: the method comprising at least three
classifications, the three classifications being a first
classification, a second classification, and a third
classification; the action corresponding to the first
classification being doing nothing to the section, at least until
the next inspection; the action corresponding to the second
classification being monitoring at least the section; and the
action corresponding to the third classification being selected
from the group consisting of: repairing at least the section and
replacing at least a plurality of adjacent sections.
29. The method according to claim 22 further comprising at least
the step of analyzing at least one of the sections for lack of
prestress pressure: over the section's entire circumference; and
over a limited length of the section.
30. The method according to claim 22 further comprising at least
the step of analyzing at least one of the sections for lack of
prestress pressure: over just a portion of the section's
circumference; and over a limited length of the section.
31. The method according to claim 22 further comprising at least
the step of analyzing at least one of the sections for lack of
prestress pressure: over a first limited length of the section; and
over a second limited length of the section; a segment of pipe with
intact prestressed wire being located between the first limited
length and the second limited length.
32. The method according to claim 31: the segment being more than
3-inches long; the segment being less than 25-inches long; and the
effective length of failed wires being a function of: the first
limited length, the second limited length, and the length of the
segment.
33. The method according to claim 22 further comprising at least
the step of analyzing the rupture pressure of at least one of the
sections.
34. The method according to claim 33, the designating a
classification comprising at least determining whether the maximum
pressure exceeds the rupture pressure of the section.
35. The method according to claim 33, the designating a
classification comprising at least determining whether the maximum
pressure exceeds, by more than a predetermined non-zero amount, the
rupture pressure of the section.
36. The method according to claim 33 further comprising at least
the step of analyzing crack onset pressure.
37. The method according to claim 36, the designating a
classification comprising at least determining whether: the maximum
pressure is less than the rupture pressure of the section; and the
maximum pressure exceeds the crack onset pressure.
38. The method according to claim 36: the designating a
classification comprising at least analyzing an action pressure;
the action pressure being less than the rupture pressure of the
section; the action pressure being greater than the crack onset
pressure of the section; and the designating a classification
comprising at least determining whether the maximum pressure is
greater than or less than the action pressure of the section.
39. The method according to claim 38, the designating a
classification comprising at least determining whether the maximum
pressure is less than the rupture pressure of the cylinder.
40. The method according to claim 22: said inspecting being
repeated at different times, the method further comprising at least
the step of tracking changes in the quantity of failed wires over
time; each classification having a corresponding action the method
further comprising at least the steps of: calculating for at least
a plurality of sections the rate of wire failures, and predicting
when a plurality of sections of the pipeline will enter a lower
classification; the method comprising at least two classifications,
the two classifications being a first classification and a second
classification; the action corresponding to the first
classification being doing nothing, at least until the next
inspection; and the action corresponding to the second
classification being selected from the group consisting of:
monitoring the section, repairing the section, and replacing at
least a plurality of adjacent sections.
41. The method according to claim 40: further comprising at least
the step of analyzing at least one section for lack of prestress
pressure: over the section's entire circumference, and over a
limited length of the section; further comprising at least the step
of analyzing at least one section for lack of prestress pressure:
over just a portion of the section's circumference, and over a
limited length of the section; further comprising at least the step
of analyzing at least one section for lack of prestress pressure:
over the section's entire circumference, over a first limited
length of the section, and over a second limited length of the
section, a segment of pipe with intact prestressed wire being
located between the first limited length and the second limited
length.
42. The method according to claim 40: further comprising at least
the step of analyzing the rupture pressure of at least one section;
the designating a classification comprising at least determining
whether the maximum pressure exceeds the rupture pressure of the
section; the designating a classification comprising at least the
step of analyzing the crack onset pressure of the section; and the
designating a classification comprising at least determining
whether the maximum pressure exceeds the crack onset pressure.
43. A computer implemented system for facilitating a determination
of whether to take pipe management action, the system comprising at
least: a processor, said processor being configured to: acquire a
first parameter, the first parameter being a design parameter for
the pipe; acquire a second parameter, the second parameter being an
inspection parameter comprising at least information indicating the
degradation of the structural integrity of the pipe; acquire a
third parameter, the third parameter comprising at least a pressure
within the pipe; and using at least a relation of the second
parameter and the third parameter, output information to facilitate
determining at least whether or not to take pipe management
action.
44. The system according to claim 43: the pipe having a diameter;
the first parameter comprising at least the diameter of the pipe;
the pressure within the pipe being substantially a maximum pressure
anticipated in future service; the processor further being
configured to output information to facilitate determining when to
take pipe management action.
45. The system according to claim 43 the processor being further
configured to: acquire at least a fourth parameter, the fourth
parameter being an inspection parameter comprising at least
information indicating the degradation of the structural integrity
of the pipe, the fourth parameter having been determined at a later
time than the second parameter; and using at least the difference
between the second parameter and the fourth parameter, calculate a
degradation rate of the pipe.
46. The system according to claim 45: the pipe being prestressed
concrete cylinder pipe; the second parameter comprising at least a
quantity of broken wires; and the processor being configured to use
the degradation rate of the pipe to calculate when the pipe should
be repaired or replaced.
47. The system according to claim 43, said system recommending pipe
management action selected from the group consisting of repairing,
replacing, and monitoring the pipe.
48. The system according to claim 43, the second parameter
comprising at least results of eddy current inspection.
49. The system according to claim 43, the relation having at least
a plurality of zones of risk.
Description
FIELD OF INVENTION
[0001] This invention relates generally to systems and methods for
analyzing the reliability and need for replacement of components,
and more specifically, to a forecasting tool for a utility network,
such as a pipeline network.
BACKGROUND OF THE INVENTION
[0002] As used herein, a pipe includes a cylindrical structure or
tube that fluids, such as water, oil, or gas, can flow through.
Further, also as used herein, a pipeline typically may include a
plurality of discrete sections of pipe arranged in series so that
the fluid may flow through the pipeline, through each section in
turn, for instance, from one end of the pipeline to the other. In
addition, as used herein, a pipe system may include a plurality of
sections of pipe arranged as needed or desired to perform the
intended function of the system. As used herein, a section of, for
example, bell and spigot pipe, may be the length from one bell to
the next, or may be a greater or lesser predetermined length of
pipe.
[0003] Pipes may be comprised of, for example, concrete, ductile
iron, and/or steel, which may deteriorate due to corrosion,
leaching, cracking, and other processes. For example, pipes in
industrial cooling water processes and municipal water systems
installed over the past 20 to 50 years are aging and the
degradation of these pipes may be related to inadequate design,
manufacturing defects, improper installation, or simply the pipes
approaching the end of their useful life. Such degradation may lead
to pipeline or system failures, which may result in costly
unplanned outages or down times.
[0004] In the past, management techniques for pipelines were
typically minimal. In general, pipelines were typically not
maintenanced regarding their structural integrity until a failure
occurred, at which time either the failed section, or the entire
pipeline, would be replaced. Pipelines may have been inspected at
planned outages, at which time obvious problems were typically
repaired. However, systematic methods of managing pipe, pipelines,
or pipe systems were typically not used to anticipate failures and
attempt to conduct preventative maintenance or replace the pipe
before failure occurs. However, the previous approach of fixing the
pipe when it breaks may not be acceptable such as in cases in which
a burst pipe may result in damage to property or injury to people,
or where loss of the process fluid would have deleterious
environmental consequences. Thus, although methods for inspecting
pipe for deterioration exist in the art, a pipeline reliability
management system and method is needed for such pipelines to
increase their reliability and availability for use, and to
effectively manage and minimize maintenance, repair, and
replacement costs over the long term.
[0005] As discussed above, a variety of types of pipe typically
exist in the municipal, industrial, and commercial industries,
including a concrete pipe which may be precast (e.g., centrifugally
cast) such as in bell and spigot construction, or may be cast in
place. The pipe is often reinforced with embedded reinforcement
steel or rebar, which is typically not significantly stressed when
the pipe is not pressurized, or may obtain its structural strength
(i.e., ability to withstand internal pressure, from prestressed or
post tensioned wires or tendons). Such wires or tendons may be
circumfrentially installed or helically wound around the pipe, and
may be covered with mortar or another coating or material to
protect the wire or tendon from corrosion or other environmental
degradation. As examples, pipe may comply with American Water Works
Association (AWWA) standard 303 or 304.
[0006] For instance, referring to FIG. 1, the pipe may be
prestressed concrete cylinder pipe (e.g., PCCP) 100, which may
consist of a cylindrical concrete core 105 helically wound with
steel wire 111, and coated with mortar 114. The steel wire 111 may
be highly stressed in tension when wound around the outer surface
112 of the core 105. For design and pipeline reliability management
purposes, the prestressed wire 111 is typically considered to
withhold the entire pressure (e.g., hydrostatic pressure) of the
contents of the pipe or fluid (e.g., water 106). In other words,
the wire 111 holds the hoop stress of pipe 100. Due to the high
prestressed tension in the wire 111, the concrete of the core 105
typically remains in compression, thereby minimizing the early
development of cracking in the concrete (of core 105) since cracks
are more likely to develop when concrete is loaded in tension.
[0007] The mortar 114 generally protects the steel wire 111 from
corrosion by excluding moisture, and/or oxygen, or by maintaining a
high pH. However, since the wire 111 may be so highly stressed, if
the wire 111 slightly deteriorates, the wire 111 may break.
Experience in the industry has revealed that such wire 111 breaks
occur with PCCP, due to, for example, damage to the mortar 114
during installation of the pipe 100, defective wire 111, hydrogen
embrittlement of wire 111, inadequate cleanliness of the outer
surface 112 of concrete core 105 when the wire 111 is installed,
corrosion of wire 111, and other causes, which sometimes cannot be
accurately identified. When a wire break occurs, the wire 111 may
slightly slip near the break, but friction between the wire 111 and
outer surface 112 of concrete core 105, typically prevents the wire
111 from loosening over the entire section of pipe 100. Moreover,
even if a certain number of wires were found to be broken, the
compression from the adjacent non-broken wires was found to extend
over the area of the broken wires. In most applications, one or
even several wire breaks may occur without failure of the pipeline;
however, if enough wires 111 break, the pipeline may fail.
[0008] In the past, despite the presence of the can 107, for PCCP
design and pipeline reliability management purposes, the
prestressed wire 111 was typically considered to withhold the
entire pressure (e.g., hydrostatic pressure and surge) of the
contents of the pipe (e.g., water 106). In other words, can 107 was
not considered to take any circumferential load or hoop stress. As
described above, due to the high tension in the wire 111, the
concrete of the core 105 typically was assumed to remain in
compression. However, this model often resulted in overly
conservative and expensive pipe management practices, which
resulted in, for example, the replacing of pipe that could have
remained in service for some time.
[0009] Various methods have been developed to inspect the various
types of pipe in service throughout the world. For instance, the
degree of physical degradation or deterioration of the pipeline may
be determined by inspection. However, effective and economical
inspection may require considerable ingenuity, since the
load-bearing component, (e.g., prestressing wire 107) may be
located underneath other layers, and the pipeline (e.g., pipe 100)
may be buried under the ground. Still, PCCP, as an example, may be
inspected in several ways. These ways include, as examples, eddy
current inspection, ultrasonic inspection, visual inspection,
sounding, and acoustic monitoring.
[0010] Eddy current inspection, such as remote field eddy
current/transformer coupling (RFEC/TC) testing, provides
estimations of broken prestressed wires 111 in PCCP (e.g., pipe
100) and identifies sections of PCCP with no degraded prestressing
wires 111. For PCCP with distress, RFEC/TC provides an estimated
number of wire breaks and the location of the breaks along the
axial length of PCCP.
[0011] Ultrasonics or Ultrasonic Testing (UT) is another method of
inspection, which has applications beyond PCCP. In fact, UT
thickness and defect examination of metallic piping has been used
since at least the late 1960s for construction and monitoring of
piping systems. For instance, UT is used as a volumetric
examination for certain critical welds at nuclear power plants.
Power plants (fossil and nuclear) also use UT for erosion/corrosion
inspection of high energy process piping lines.
[0012] Visual inspection is another option, when access permits, to
determine the level of pipeline degradation. Referring once again
to FIG. 1, the inside 102 and/or outside 122 of pipe 100 may be
visually inspected, and visual inspection may be either direct or
remote (e.g., via a camera inserted within pipe 100 to view inside
surface 102). Corrosion, spawling, cracking and deflection provide
visual indications that piping is in distress.
[0013] Sounding is another method of inspecting pipe, which
involves tapping on the pipe and listening for the resulting sound.
In the recent past, engineers attempted to analyze a pipe for areas
of delamination by simplistic manual methods, such as by walking
through a pipe and tapping on the inside of the pipe in an effort
to hear tone changes which were often indicative of hollow areas
within the pipe wall. The engineers often determined that the
hollow areas in the pipe wall were areas of concrete failure. When
access permits, such sound (impact echo) can be used to determine
the level of degradation in pipes.
[0014] Sounding may be performed manually (e.g., with a hammer and
the human ear) or may also be performed with sophisticated
equipment that may provide a consistent impact, record the
resulting sound, and display or analyze the frequency response of
the sound, rate of attenuation, or other characteristics. However,
in order for UT, visual inspection, or sounding to be effective, it
may be necessary to uncover the pipe. Even if access to the inside
102 of the pipe is possible, the prestressing wires 111 are
typically located far from the inside surface of the pipe, and
distress may not show up on surface concrete until failure is
imminent. As can be appreciated, uncovering buried pipelines for
periodic inspection of the outside 122 may also be cost
prohibitive.
[0015] Another method of inspection is acoustic monitoring, which
was invented by Douglas Buchanan of the U.S. Bureau of Reclamation
in the 1990's for use on the Central Arizona Project. Acoustic
monitoring involves installing listening devices on or within the
pipeline, and monitoring the devices for the sounds generated by
the degradation of the pipe. As an example, hydrophones may be
installed in water 106 carried by PCCP (pipe 100), which may be
monitored by one or more computers or processors, which may be
programmed to recognize the sound made by breaking prestressing
wires 111. The location of the breaks along the pipe 100 may be
determined by comparing the arrival times of the sound at
hydrophones on either side of the break. Hydrophones may be
installed through taps in the pipe wall (e.g., through core 105) or
in a string located within pipe 100.
SUMMARY OF THE INVENTION
[0016] The present invention provides, inter alia, a system and
method for facilitating the forecasting of pipeline and pipe system
reliability to effectively manage maintenance, repair, and
replacement costs over the long term. The system and method may be
employed in the design, installation, testing, and operational
phases of new pipelines, for instance, to maximize service
life.
[0017] In specific embodiments, the present invention provides a
method of facilitating the determination of whether to take pipe
management action such as repairing or replacing pipe. The method
generally includes (in any order) the steps of: acquiring a first
parameter (e.g., a design parameter for the pipe, such as the
diameter); inspecting the pipe a first time; acquiring a second
parameter (e.g., an evaluation of the structural integrity of the
pipe); and acquiring a third parameter (e.g., a pressure within the
pipe, which may be the maximum pressure anticipated in future
service). The method generally also includes the step of: using at
least a relation (e.g., a graph) of the evaluation of the
structural integrity of the pipe and the pressure within the pipe,
facilitating a determination of whether or not to take pipe
management action. When the pipe management action should be taken
may also be determined.
[0018] The method may also include the steps of: waiting until the
next time to inspect; inspecting the pipe a second time; and
acquiring a fourth parameter (e.g., another evaluation of the
structural integrity of the pipe taken at a later time). The
degradation rate of the pipe may be calculated, (e.g., from the
difference in the structural integrity of the pipe from the first
time the pipe was inspected to the second time it was inspected).
In the alternative, the degradation rate may be assumed, (e.g.,
from prior experience). Whether assumed or calculated for the
particular pipe or section of pipe, the degradation rate may be
used, for instance, to calculate when the pipe should be, for
example, repaired or replaced.
[0019] In an exemplary embodiment, the pipe may be prestressed
concrete cylinder pipe, and the second parameter may include a
quantity of broken wires. The inspecting may utilize, as examples,
eddy current inspection, ultrasonic inspection, visual inspection,
or sounding (or a combination thereof). The pipe management action
may involve, as examples, repairing, replacing, or monitoring the
pipe.
[0020] The relation or graph may be either physically-viewable or
embedded within a computer or computer program (e.g., in a computer
implemented method), and may have a plurality of zones of risk
(e.g., high and low risk). As an example, in the case of PCCP, the
graph or relation may include the anticipated maximum pressure
within the pipe versus the number of failed prestressing wires
discovered during inspection. The method may further be tested over
time to verify that it works.
[0021] In another embodiment, the present invention further
provides a system for facilitating a determination of whether to
take pipe management action. The system generally includes a
relation of pressure versus a quantification of the degradation of
the structural integrity of the pipe. Similar to as described above
for the method, the relation may be either a physically-viewable
graph or embedded within a computer, such as an algorithm, data, or
a combination thereof. The relation may have a zone of higher risk
and a zone of lower risk, and may also have a zone of medium
risk.
[0022] The pipe for which the system is used may have a concrete
core, and may be prestressed concrete cylinder pipe. Thus, the
quantification of the degradation of the structural integrity of
the pipe may include a quantity of broken wires. The quantity of
broken wires may be, for example, an actual number of contiguous
broken wires, a length of pipe wherein all wires are broken, or an
equivalent length of pipe where in actuality not all contiguous
wires are broken. Further, the pressure that is used may be maximum
anticipated pressure (e.g., within the pipe). The relation (e.g., a
graph) may further include the anticipated pressure for the
ultimate strength of the cylinder, the anticipated rupture pressure
of the pipe, or even the pressure anticipated to cause the concrete
core to crack. The relation may even further include an action
pressure, which may be less than the anticipated rupture pressure
of the pipe, but greater than the pressure anticipated to cause the
concrete core to crack.
[0023] The present invention even further provides a method of
facilitating the management of a pipeline. In this embodiment, the
pipeline may include a plurality of sections of prestressed
concrete cylinder pipe. The method may include in any order the
steps of storing design data (e.g., one or more dimensions,
external loading, etc.) for each of the sections, inspecting a
plurality of the sections (e.g., evaluating the quantity of failed
wires within the sections), and estimating the maximum pressure
that is likely to exist within the sections in future service. The
method may also include using the design data, the quantity of
failed wires, and the maximum pressure to designate a
classification for the condition of the sections of pipe, and
implementing pipe management action based on these
classifications.
[0024] The inspecting may be repeated at different times, and
changes in the quantity of failed wires may be tracked over time.
In addition, there may be two, three, or more classifications, and
each classification may have a corresponding action. Furthermore,
the method may include the steps of calculating the rate of wire
failures for the sections, and predicting when the sections will
enter another classification.
[0025] The pipe management action that is taken (e.g.,
corresponding to a classification) may be, for instance, doing
nothing to the section (at least until the next inspection),
monitoring the section, repairing the section, or replacing one or
more sections. In some embodiments, sections may be repaired
individually until the pipeline deteriorates to the point that it
is advantageous to replace the entire pipeline.
[0026] The method further may include the step of analyzing one of
the sections for lack of prestress pressure over the section's
entire circumference, but over a limited length of the section. The
sections may also be analyzed for lack of prestress pressure over
just a portion of the section's circumference, and over a limited
length of the section. The sections may even further be analyzed
for lack of prestress pressure over a first limited length of the
section, and over a second limited length of the section, where
there is a segment of pipe with intact prestressed wire located
between the first limited length and the second limited length. The
segment may be, for example, more than 3-inches long, but less than
25-inches long, and an effective length of failed wires may be
used, which may be calculated as a function of the two limited
lengths of failed wires and the length of the segment in
between.
[0027] The method further may include the steps of analyzing the
rupture pressure of the sections, and designating a classification
based on whether the maximum pressure exceeds the rupture pressure.
Whether the maximum pressure exceeds the rupture pressure of the
section by more than a predetermined non-zero amount, may also be
determined. In addition, crack onset pressure may be analyzed, and
whether the maximum pressure exceeds the crack onset pressure may
be determined. Even further, an action pressure may be determined,
which may be less than the rupture pressure of the section, but may
be greater than the crack onset pressure. Thus, the step of
designating a classification may include determining whether the
maximum pressure is greater than or less than the action pressure
of the section. The designating a classification may also include
determining whether the maximum pressure is less than the rupture
pressure of the cylinder or can.
[0028] The present invention still further provides a computer
implemented system for facilitating a determination of whether to
take pipe management action. The system generally uses a processor
that is configured to acquire or input one or more design
parameters (e.g. the diameter of the pipe), input one or more
inspection parameters (e.g. information indicating the degradation
of the structural integrity of the pipe, such as a quantity of
broken wires in PCCP, that may be determined via eddy current
inspection), and input the pressure within the pipe (e.g. the
maximum pressure anticipated in future service). The system
generally uses at least a relation of these parameters (e.g. the
number of broken wires v. pressure) to output information to
facilitate determining whether or not to take pipe management
action (e.g. to recommend whether or not to repair, replace, or
monitor the pipe). In some embodiments, information indicating the
degradation of the structural integrity of the pipe may also be
determined again at a later time, and the change in the structural
integrity may be used to calculate the degradation rate of the
pipe. Further, when to take pipe management action may also be
output, (e.g. using the degradation rate of the pipe).
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention is illustrated by way of example and
not limitation in the accompanying figures, in which like reference
numbers indicate similar elements, and in which:
[0030] FIG. 1 is an orthographic projection of a section view of
prestressed concrete cylinder pipe, showing typical layers in the
wall of such pipe;
[0031] FIG. 2 is a block diagram illustrating a system in
accordance with the present invention;
[0032] FIG. 3 is a flow chart illustrating the steps of one
exemplary embodiment of a method in accordance with the present
invention;
[0033] FIG. 4 is a graph of pressure versus number of wires broken,
illustrating various aspects of an exemplary embodiment of the
present invention;
[0034] FIG. 5 is another flow chart illustrating the steps of
another exemplary embodiment of a method in accordance with the
present invention; and
[0035] FIG. 6 is another flow chart illustrating the steps of a
further exemplary embodiment of a method in accordance with the
present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0036] The present invention includes systems and methods for
analyzing the reliability and replacement of components, and more
specifically, to a forecasting and reliability management tool for
a utility network, such as a pipeline network or pipe system. As
such, while the system and methods shall be described in relation
to a pipeline or pipe system, one skilled in the art will
appreciate that much of the functionality is applicable to other
components, utilities, networks and/or the like. For example, at
least certain aspects of the present system and method may be
applied to any portion of roads, canals, sewer systems, power
lines, railroad tracks, buildings, circuits, fences, walls or any
other system with components that may fail or degrade. The present
invention may also be applicable to heat exchanger tube inspections
and monitoring pipelines for erosion or corrosion.
[0037] In this regard, the present invention may be described
herein in terms of functional block components and various
processing steps. It should be appreciated that such functional
blocks may be realized by any number of hardware, firmware, and/or
software components configured to perform the specified functions.
For example, the present invention may employ various integrated
circuit components, such as memory elements, digital signal
processing elements, look-up tables, databases, and the like, which
may carry out a variety of functions under the control of one or
more microprocessors or other control devices. Such general
techniques and components that are known to those skilled in the
art are not described in detail herein.
[0038] It should further be understood that the exemplary process
illustrated may include more or less steps or may be performed in
the context of a larger processing scheme. Furthermore, the various
flowcharts presented in the drawing figures are not to be construed
as limiting the order in which the individual process steps may be
performed.
[0039] As a general overview, the present invention provides a
system and method for managing or facilitating the management of
pipe, pipeline, or pipe system reliability, for example, to
increase the reliability of a pipeline and availability for use,
and to effectively manage actions that may be taken such as
maintenance, repair, and replacement, and their costs (e.g., over a
longer term). Embodiments include a system and method that may be
employed in the design, installation, testing, and operational
phases of new or existing pipelines or pipe systems, for instance,
to maximize service life or minimize life cycle costs. Many
embodiments are computer-implemented, and comprise, inter alia, a
method of forecasting, managing or determining whether or when to
take pipe management action such as to repair or replace
prestressed concrete cylinder pipe (e.g., PCCP). Various
embodiments include steps such as inspecting the pipe and storing
or inputting various parameters, such as design parameters,
inspection parameters, and environmental parameters. Inspection may
involve, for instance, eddy current inspection, ultrasonic
inspection, visual inspection, sounding, or some combination of
these. Embodiments may also include acquiring or inputting the
maximum pressure (e.g., expected within the pipe) and determining
whether or not to repair or replace the pipe, and in some
embodiments, whether or not to monitor the pipe.
[0040] In general, various embodiments may use a relation or graph
of pressure versus a quantification of the structural integrity or
degradation of the structural integrity of the pipe, wherein the
degradation of the structural integrity of the pipe may include,
for instance, the number of broken prestressing wires in PCCP or
the degree of wall thinning in other pipes. As would be apparent to
a person skilled in the art, the structural integrity of the pipe
and the degradation of the structural integrity of the pipe are
usually related. For instance, the structural integrity of the pipe
may be the number of wires that are intact, while the degradation
in the structural integrity may be the number of wires that are
broken. Thus, as the terms are used herein, a relation or graph
that involves the structural integrity of the pipe also generally
includes the degradation of the structural integrity of the pipe,
and vice versa.
[0041] The relation or graph may have zones of high, medium, and
low risk and may show the pressure for the ultimate strength of the
cylinder (in the case of PCCP). The method may also include
designating a zone of risk or classification for the condition of
the pipe, and implementing pipe management action based on the
classification. The pipe may be analyzed for lack of prestress
pressure over various portions of the pipe's circumference and
length. The method may also include analyzing the rupture pressure
of the pipe, the crack onset pressure, or the rupture pressure of
the cylinder (of PCCP) alone, each of which may be compared to the
maximum pressure anticipated within the pipe. The method may
further include the steps of testing the method over time to verify
that it works or repeating the inspection at different times, and
tracking changes in the quantity of failed wires. The action may
involve doing nothing (at least until the next inspection),
monitoring the pipe, repairing the pipe, or replacing the pipe.
[0042] More particularly, embodiments of the present invention may
provide a system and method of facilitating the determination of
whether to take pipe management action such as repairing or
replacing pipe. The system or method may be used for pipeline or
pipe system reliability management, which may include manual
mapping, automation and/or analysis facilitated through a computer
or processor.
[0043] With respect to system components, FIG. 2 is a block diagram
illustrating an exemplary system in accordance with the present
invention. More particularly, FIG. 2 illustrates in an exemplary
embodiment, a computer implemented system 200 for facilitating a
determination of whether to take pipe management action, for
instance, determining the next action for the management of a
pipeline. The system 200 generally uses a computer or processor 230
that is configured to receive or input various parameters (e.g.
first parameter 201, second parameter 202, etc.). Seven inputs or
parameters are shown (first parameter 201 through seventh parameter
207); however, fewer or more parameters could be used as would be
apparent to a person of ordinary skill in the art. Parameters
201-207 may include one or more design parameters (e.g. the
diameter of pipe 100), one or more inspection parameters (e.g.
information indicating the degradation of the structural integrity
of the pipe, such as a quantity of broken wires in PCCP, that may
be determined, for instance, via eddy current inspection), and the
pressure within pipe 100 (e.g. the maximum pressure anticipated in
future service). Processor 230 is generally configured to receive
these inputs, which are described in more detail below.
[0044] In the exemplary embodiment shown, processor 230 is
configured to analyze the input parameters (e.g., some or all of
parameters 201-207) and output recommended action 260, which may
include a mapping function and/or a recommended action ranging
from, for instance, doing nothing to repairing or replacing pipe
100 (e.g., pipe management action as described herein). To
determine the recommended action 260, processor 230 may use a
relation of at least some of parameters 201-207 (e.g. the
degradation of the structural integrity of pipe 100 or the number
of broken wires 111 v. pressure). This relation (described in more
detail with reference to FIG. 4 below) may be used to determine and
output via recommended action 260, information configured to
facilitate determining whether or not to take pipe management
action, or which pipe management action to take.
[0045] Still referring to FIG. 2, in some embodiments of the
present invention, information indicating the degradation of the
structural integrity of pipe 100 may be determined again at a later
time, and processor 230 may be configured to use the change in the
structural integrity to calculate the degradation rate of pipe 100.
Further, processor 230 may be configured so that recommended action
260 includes when to take pipe management action, which may be
calculated (e.g. by processor 230), as an example, using the
degradation rate of pipe 100. Output (e.g. recommended action 260)
may be tabular or graphic, and processor 230 may be programmed to
provide numerical data or graphic information. In addition, as
would be apparent to a person of skill in the art, although system
200 shows a processor 230, some or all of the functions or analysis
performed by processor 230 could also be performed manually.
[0046] systems (such as system 200 illustrated in FIG. 2) utilizing
a computer, the system may include a host server or other computing
systems, including, as examples: a processor for processing digital
data; a memory coupled to the processor for storing digital data;
an input digitizer coupled to the processor for inputting digital
data; an application program stored in the memory and accessible by
the processor for directing processing of digital data by the
processor; a display coupled to the processor and memory for
displaying information derived from digital data processed by the
processor; and a plurality of databases, which may include input
data, historical data, specification data and/or like data that
could be used in association with the present invention. As those
skilled in the art will appreciate, user computer will typically
include an operating system (e.g., Windows NT, 95/98/2000, Linux,
Solaris, etc.) as well as various conventional support software and
drivers typically associated with computers.
[0047] Similarly, the software elements of the present invention
may be implemented with a spreadsheet or computer program such as
Excel or Dbase. In addition, a programming or scripting language
may be used such as C, C++, Java, COBOL, assembler, PERL,
extensible markup language (XML), with the various algorithms being
implemented with any combination of data structures, objects,
processes, routines or other programming elements. Further, it
should be noted that the present invention may employ any number of
conventional techniques for data transmission, signaling, data
processing, network control, and the like. Still further, the
invention could be used to detect or prevent security issues with a
client-side scripting language, such as JavaScript, VBScript or the
like. The users may interact with the system via any input device
such as a keyboard, mouse, kiosk, personal digital assistant,
handheld computer (e.g., Palm Pilot.RTM.), cellular phone and/or
the like. Similarly, the invention could be used in conjunction
with any type of personal computer, network computer, workstation,
minicomputer, mainframe, or the like running any operating system
such as any version of Windows, Windows NT, Windows2000, Windows
98, Windows 95, MacOS, OS/2, BeOS, Linux, UNIX, Solaris, ArcSoft
(GIS) or the like.
[0048] The database may be any type of database, such as
relational, hierarchical, object-oriented, and/or the like. Common
database products that may be used to implement the databases
include DB2 by IBM (White Plains, N.Y.), any of the database
products available from Oracle Corporation (Redwood Shores,
Calif.), Microsoft Access by Microsoft Corporation (Redmond,
Wash.), or any other database product. The database may be
organized in any suitable manner, including as data tables or
lookup tables. Association of certain data may be accomplished
through any data association technique known and practiced in the
art. For example, the association may be accomplished either
manually or automatically. Automatic association techniques may
include, for example, a database search, a database merge, GREP,
AGREP, SQL, and/or the like. The association step may be
accomplished by a database merge function, for example, using a
"key field" in each of the manufacturer and retailer data tables. A
key field partitions the database according to the high-level class
of objects defined by the key field. For example, a certain class
may be designated as a key field in both the first data table and
the second data table, and the two data tables may then be merged
on the basis of the class data in the key field. In this
embodiment, the data corresponding to the key field in each of the
merged data tables is preferably the same. However, data tables
having similar, though not identical, data in the key fields may
also be merged by using AGREP, for example.
[0049] Turning now to exemplary methods, FIGS. 3, 5, and 6 are flow
charts illustrating various steps of various embodiments of the
present invention. Embodiments of methods in accordance with the
present invention may contain, inter alia, steps from one or more
of these drawing figures. In general, FIG. 3, illustrates input
steps, pipe management action, and the decisions regarding which
pipe management action to take. In comparison, FIG. 5 illustrates
input steps, calculations, and the decisions made based on those
calculations. In further comparison, FIG. 6 illustrates input
steps, analyses, and various other intermediate steps such as
tracking changes.
[0050] Specifically, FIG. 3 illustrates an exemplary embodiment of
a method in accordance with the present invention, which depicts,
inter alia, a method of pipeline reliability management, for
example, a method of determining or facilitating the determination
of whether or when to take pipe management action such as repairing
or replacing pipe. The pipe may be, for example, PCCP, although the
present system and method 300 would generally work for other types
of pipe, conduit, and ductwork, as well, which may be made of, as
examples, concrete, welded steel, screwed steel, riveted steel,
ductile iron, cast iron, plastic, copper, stainless steel, or
aluminum bronze. Method 300 may include steps that are
computer-implemented, (e.g., via processor 230 illustrated in FIG.
2) although some steps (e.g., replacing the pipe (step 324))
generally must be performed manually or by mechanical means and/or
other means. Such external steps may not be part of embodiments of
the present invention involving only the computer system. In
addition, a computer simulation of pipeline systems and replacement
of pipes may be part of the system and method.
[0051] Method 300 generally includes the steps of acquiring or
inputting design parameters (step 305), inspecting the pipe (step
302), and acquiring or inputting inspection parameters (step 308).
Although shown and described in the plural, in some embodiments
only one design parameter or inspection parameter may be acquired
or input. In other embodiments, multiple design parameters and
inspection parameters may be acquired or input. Design parameters
(e.g., as input in step 305) may include dimensions of the pipe,
such as diameter, configuration, hydraulic performance, design
loading, degraded pipe performance and/or the like. Other input
data may include the diameter, thickness, and material strength of
can 107, the diameter, thickness, and material strength of core
105, the wire size (e.g., diameter), spacing, tensile strength, and
prestress tension of wire 111, the maximum operating pressure and
anticipated transient pressure, the process fluid temperature and
chemistry, and the pipe dead load (e.g., soil cover) and live load
(e.g., road or railroad loading), and information related to the
degradation rate of particular systems.
[0052] The inspection parameters (input in step 308) may include an
evaluation of the structural integrity of the pipe, which, in the
case of PCCP, may be the length or quantity of continuous or
adjacent wire (e.g., wire 111 shown in FIG. 1) breaks within the
section of pipe being analyzed. As used herein, a quantity of
failed or broken wires may mean the actual number of wires broken
or another value that is convertible to the actual number of wires
broken, such as the length of pipe having adjacent broken wires.
Further, a quantity of broken wires may include an effective value
(e.g. an effective length as described in more detail below) where
not all wires in a continuous portion of pipe have failed or are
broken.
[0053] The inspection from which the inspection parameters (of step
308) are derived may involve eddy current inspection, ultrasonic
inspection, visual inspection, sounding, acoustic monitoring, or
other methods, which may be known in the art. FIG. 3 also shows the
step of acquiring or inputting internal pressure 311, which may be
either a design parameter or an inspection parameter depending on
various factors including whether the design pressure is still the
best information available. The maximum future pressure within the
pipe may be estimated considering design data, field conditions,
and planned use. However, the internal pressure (of step 311) could
be based only on design data or historical measured pressure, for
instance, the maximum pressure measured to date in service similar
to that anticipated. The steps of acquiring or inputting design
parameters (step 305), and acquiring or inputting inspection
parameters (step 308) may include acquiring or inputting one or
more environmental parameters or conditions specific to the site.
These may include the amount of moisture or pH of the soil,
etc.
[0054] Program inputs or parameters (e.g., 201-207 in FIG. 2) may
originate from a piping design review (e.g., for step 305 in FIG.
3) and inspection (e.g., step 302 in FIG. 3), and the system (e.g.,
200) or method (e.g., 300) may result in various outputs (e.g.,
recommended action 260). The piping design review (e.g., for step
305 in FIG. 3) may involve gathering various design data, which may
already exist within drawings, specifications, and other
documentation typically kept for pipelines. An understanding of the
design, installation and construction of the pipeline may be
helpful as a baseline for a pipeline reliability management
determination. A typical review may consider the pipeline and
control systems (including cathodic protection, if any),
interconnected/adjacent systems, the fluid or gases conveyed by the
pipeline, and the pipelines environmental conditions. One area that
may be reviewed is the configuration of the pipeline. The original
design, manufacture and installation drawings/specifications and
field observations may be used to establish the materials of
construction, diameter, and unit length for each spool or section
of the pipeline. Where applicable, this data may be entered into
the computer or processor (e.g., 230 in FIG. 2) and may be
verified. Another area that may be reviewed is the hydraulic
performance of the pipeline. The hydraulic performance
characteristics (i.e., operating pressures, temperatures as a
result normal/abnormal design conditions) of the pipeline may be
reviewed, verified, and where applicable, entered into the computer
(e.g., processor 230 in FIG. 2) for each corresponding pipe spool
(i.e., section of pipe or unit length).
[0055] A further area that may be reviewed (e.g., for step 305 in
FIG. 3) is design loading. Live and dead loads on the pipeline may
be documented, which may include soil cover, roads and railroads,
seismic conditions (e.g., earthquake loads), etc. An even further
area that may be reviewed is the performance of pipe that has
undergone degradation. A design review/study may be performed to
determine how the piping system will perform under design loading
with varying degrees of degradation. Specifically, an understanding
of the failure progression for the pipe may be needed. As an
example, prestressed concrete cylinder pipe (PCCP) may be analyzed
to determine the amount of loss of prestressing wires (e.g., 111 in
FIG. 1), concrete core (105) cracking, or loss of steel cylinder
(can 107) thickness that can be withstood for a given system design
and pressure. Similar engineering reviews for ductile iron or steel
pipe may model wall thickness reductions in terms of area, minimum
wall thicknesses, and corrosion allowances. Results of such a
review may be expressed in numerical terms (e.g. number of broken
wires 111, minimum wall thickness, minimum design, corrosion
allowance per year, etc.) which in computer implemented embodiments
may be entered into the computer (e.g., processor 230 in FIG. 2)
for each spool or section.
[0056] The second type of data or program inputs to the system and
method of pipeline reliability management are the result of
inspection (e.g., inspection parameters of step 308 shown in FIG.
3). Various methods have been developed to inspect (e.g., step 302)
the various types of pipe to evaluate the integrity or extent of
physical degradation of the pipeline. Some of these methods are
described above, including, as examples, eddy current, ultrasonic,
visual inspection, sounding, and acoustic monitoring. The
application to different pipelines may be selected based on access,
materials of construction, and cost. In embodiments where a
computer or processor (e.g., processor 230 in FIG. 2) is used,
results of the above inspections may be input into the computer or
processor. As an example, in addition to applications of the above
inspection techniques with PCCP, UT could also be used for
reliability evaluation of metallic piping systems. In the exemplary
embodiment of use with PCCP, wire break numbers and locations may
be entered into the computer or processor (e.g., processor 230) for
each spool or section of pipe. RFEC techniques may also be used to
measure wall thinning in metallic pipe, such as 12-inch ductile
iron fire protection piping. These values/degradation parameters
could also be input to the computer or processor (e.g., processor
230) for reliability evaluation of ductile iron piping systems.
[0057] Still referring to FIG. 3, in the exemplary embodiment
illustrated, after the data input steps (input parameters of steps
305, 308, and 311), the data may be analyzed (as described below)
(e.g., by processor 230 shown in FIG. 2), and the output may
include one or more recommended options regarding corrective
action, or action to manage the pipe or pipeline. The output may
include, for example, whether to replace (step 314), repair (step
317), or monitor (step 319) the pipe. The output may involve, for
instance, each section or spool of pipe (e.g., each bell and spigot
section), or larger sections of pipe, up to the entire pipeline.
Although these three options are shown in method 300, embodiments
of the present invention may have fewer, more, or different options
for pipe management action.
[0058] Taking a closer look at the pipe management actions
illustrated in FIG. 3, method 300 illustrates and may include the
steps of replacing the pipe (step 324), repairing the pipe (step
327) or monitoring the pipe (step 329). Method 300 illustrates and
may also include the steps of determining when to inspect the pipe
(e.g., 100) next (steps 332 and 339), and either monitoring the
pipe (step 329) or simply waiting until it is time to inspect the
pipe again (step 335). Replacing the pipe (step 324) may involve
replacing with the same kind or a different kind of pipe (e.g.,
replacing PCCP with steel pipe or cast-in-place).
[0059] Determining when to inspect next (step 332), may involve
making a determination of how quickly the pipe is deteriorating,
(e.g., a degradation rate). The degradation rate may be determined
from the difference in condition of the pipe between at least two
successive inspections performed at different times. For instance,
methods of extrapolation may be used, which may be commonly known.
The degradation rate may be used not only to determine when to
inspect the pipe next, but may also be used to estimate or forecast
when the pipe will need to be or should be repaired or replaced.
This estimate may be used to determine when funding, manpower, or
equipment will be needed, or otherwise to plan the work. In the
alternative, a degradation rate may be assumed rather than
determined for a particular pipe, and when the pipe will need to be
or should be repaired or replaced may be determined from the
assumed degradation rate and the results of one inspection.
[0060] Repairing the pipe (step 327) may involve installing post
tensioned tendons around the outside surface 122 of pipe 100,
installing a steel liner within the inside surface 102 of pipe 100,
or other methods of repairing pipe, including those known in the
art. Post tensioned tendons may comprise wire rope, which may be
installed within a polymer sleeve to protect the wire rope from
corrosion. The sleeve may further contain a corrosion inhibiting
material or grease. However, a possible disadvantage of this repair
method includes the need to excavate all the way around the pipe
(e.g., pipe 100), which may need to be done for each tendon at a
time below spring-line, in order to install post tensioned tendons.
Once excavated, the tendon may be wrapped once around the pipe, and
then tensioned (e.g., to replace the lost prestress). The
excavation may require hand excavation to avoid damaging the pipe,
and may be labor intensive and expensive. However, it may be
possible to do it while the pipeline is in service, and it may be
considerably less expensive than replacing the entire pipeline.
[0061] In contrast, repairing pipe (step 327 of FIG. 3) by
installing a steel liner may involve taking the pipe out of service
for an extended period of time to install the liner, and may
involve extensive field welding and grouting between the liner and
interior 102 of pipe 100. In addition, a liner ultimately results
in a reduction of the inside diameter of the pipe, which may reduce
capacity or increase the pumping energy required for a given flow.
Further, a protective coating, such as coal tar epoxy or cement
mortar, may need to be applied and maintained on the steel liner to
protect it from corrosion.
[0062] Whether a pipe is repaired or replaced may depend on how may
spools or sections of pipe are in a seriously distressed condition,
the importance of the pipeline, whether funding is available now,
the time value of money, and other factors. It may be less
expensive to replace a pipeline than to repair the entire pipeline;
however, if areas of distress can be consistently identified prior
to failure, considering the time value of money, it may be less
expensive to repair a portion of a pipeline each year for an
extended period of time than to incur the up-front cost of
replacing the entire pipeline. Monitoring the pipe (step 329) may
involve installing and using an acoustic monitoring system (e.g.,
as described above) or inspecting the pipe frequently.
[0063] The analysis of the present invention (e.g., of method 300)
may involve using a graph 400 or relation of pressure versus a
quantification of the structural integrity or the degradation of
the structural integrity of the pipe, an example of which is
illustrated in FIG. 4, and is described in more detail below.
Although graph 400 is depicted in FIG. 4 as being physically
viewable, as would be apparent to one skilled in the art, a
relation may be used in the present invention that is, for
instance, embedded within a computer program and may not be readily
viewable. Thus, the zones or curves (such as shown in graph 400)
may be defined by equations, look-up tables, or the like. Further,
as used herein, a relation may be embedded within a computer
program and may not be readily viewable, or may be a physically
viewable graph such as graph 400. For the sake of explanation
herein, a viewable graph 400 is described. However, the
characteristics described for graph 400 may apply to a relation in
various embodiments of the present invention.
[0064] The relation or graph (e.g., 400) may have at least zones of
high risk (e.g., 1a and 1b) and low risk (e.g., 4 and 5). Further,
the relation or graph (e.g., 400) may include additional zones of
intermediate or medium risk (e.g., 2a, 2b, 3a, and 3b). Thus, the
various zones may have higher risk or lower risk, e.g. relative to
each other. For instance, on graph 400, the higher the number of
the zone, the lower the risk. The boundaries of these zones (e.g.
the curves shown on graph 400), among other factors in the
analysis, may be refined over time based, for example, on failures
in service and destructive or non-destructive testing (e.g., of
pipe that is designated for replacement). Thus, the determinations
of whether to replace (step 314), repair (step 317), or monitor
(step 319) the pipe may include the step of testing the method over
time to refine the accuracy of the method.
[0065] Referring generally to FIGS. 1-5, once the necessary
information is obtained or input into a computer or processor
(e.g., processor 230 in FIG. 2), the data may be analyzed in
accordance with various aspects of the present invention. One step
may be to analyze or calculate the rupture pressure of the pipe
(step 551). In the example of PCCP, the analysis of rupture
pressure may involve considering a loss of prestress (wire 111
failure) extending over a significant part of the pipe 100. To do
so, the core 105 may be modeled as a long cylindrical shell
subjected to the effective external pressure of prestressing, and
the anticipated maximum pressure (e.g., of step 311) within the
pipe. In the case of a liquid fluid, such as water 106, the maximum
pressure within the pipe (internal pressure) may include
hydrostatic pressure, but may also include local dynamic effects
such as surge or potential water hammer.
[0066] Referring still to FIG. 1, other external pressures such as
soil loading or groundwater pressure may also be considered where
applicable and ascertainable. Pipe weight and fluid weight may also
be considered. These loads may produce bending in the pipe wall,
but may not have a significant effect on the can 107 after cracking
of the core 105. In some cases, thrust effect of external loading
may be considered, although they may be small relative to internal
pressure. In more sophisticated embodiments of the present
invention, in addition to the foregoing effects, the effects of
microcracking and cracking of the concrete core 105, and yielding
and strain (work) hardening of the steel cylinder or can 107 may
also be considered.
[0067] To perform the analysis or decide what pipe management
action to take or recommend, the loss of prestress over the pipe's
entire circumference may be simulated by removing the prestressing
pressure around the entire circumference over a limited length of
pipe 100. Using the loss of pre-stress and the maximum pressure
within the pipe, the maximum circumferential stresses in the
concrete core may be calculated. The maximum stress may be compared
with the allowable stress for the degraded pipe (i.e., the pipe 100
with broken wires 111). For instance, the ultimate strength of the
degraded composite structure (e.g., concrete core and steel
cylinder or can 107, with no wires 111) may be determined.
Allowable stresses may be set lower to provide a design or safety
margin. In this way, risk of failure can be measured by how close
actual stresses compare to allowable or ultimate stresses.
Generally, all other things being equal, the closer actual stresses
are to the ultimate stress, the higher the risk.
[0068] If the maximum circumferential stress in the core 105
exceeds the cracking strength, then it may be assumed that the core
105 cracks around pipe 100, resulting in softening (generally a
significant reduction in strength in the circumferential direction)
of core 105 around the entire circumference. However, since in this
scenario can 107 is still intact and wire 111 is still intact
nearby, the concrete core 105 can still resist the internal
pressure, for example, by longitudinal strips of the core 105
loaded (as beams) in bending. (The analysis of these strips is
performed in step 546 shown on FIG. 5 and described below.) Thus,
in the case of PCCP, the steel cylinder or can 107 may increase the
strength of the core 105. The tensile strength of the can 107 can
be considered in the circumferential direction; however, the
tensile strength of the can 107 may also increase the strength of
the longitudinal strips of the core 105 loaded as beams in
bending.
[0069] A loss of prestress may also exist over just a portion of
the circumference of the pipe 100. As an example, such a localized
loss of prestress may be modeled as being absent within an 11.25
degree angle. In this scenario, bending moments may develop along
the termination points of prestressing, which may lead to cracking.
The strength of the core 105 beyond the prestress-loss zone will
prevent cracking if the length of such a zone is small, as may be
analyzed and revealed by a finite element analysis. In addition,
the analysis of the loss of prestress may be effected by whether
the loss is at the end of a section of pipe 100, or somewhere in
the middle.
[0070] Embodiments of the present invention may analyze the case in
which there are multiple prestress loss zones or areas near each
other, with a segment of intact prestressed wire 111 in between. If
the segment of intact prestressed wire 111 in between is large
enough (e.g., greater than 25 inches), then the two areas of
prestress loss may be analyzed independently from each other. In
such a case, the worst case scenario is the larger of the two
lengths of prestressed loss, and there may be no reason to consider
the shorter section. On the other extreme, if the segment of intact
prestressed wire 111 in between is small enough (e.g., less than 3
inches), then the lengths of the two sections of prestress loss may
be added together into one effective length. In addition, there may
be an intermediate length of the segment of intact prestressed wire
111 between the two sections of prestress loss wherein an effective
length of prestress loss may be given by a formula such as:
effective length =L2(0.6064-0.02424B)+L1(1.0754-0.00303B)
[0071] where L1 and L2 are lengths of the two area of prestress
loss, L1>L2, and B is the length of the area of intact
prestressed wire 111 in between the two areas of prestress
loss.
[0072] As would be apparent to a person skilled in the art, the
constants in the above equations, and the range of B for which the
equations apply, may vary depending on the size and design of the
pipe.
[0073] Returning to FIG. 4, in various embodiments of the present
invention, different designs and sizes of pipe may be evaluated for
rupture and cracking. For each pipe design, the length of the
prestress loss and the magnitude of the internal pressure may be
varied to calculate, for example, the maximum stress in the core
105. The relationship between prestress loss length and internal
pressure may then be determined. The length of prestress loss,
which may be readily convertible to the number of wire 111 breaks
(and vice versa), may be plotted as a function of pressure that
causes cracking or rupture. In one exemplary embodiment, separate
relations or plots may be prepared and considered for prestress
loss at the end of the pipe, and prestress loss in the middle of
the pipe.
[0074] An example of a plot of pressure versus wires broken (graph
or plot 400) is shown in FIG. 4, which illustrates a relation that
may be computer implemented. Four curves (407, 410, 415, and 420)
are shown on graph 400. In the embodiment illustrated, curve 410
indicates rupture, curve 420 indicates cracking onset, and curve
415 is located between curve 410 and curve 420, dividing the zone
in between into repair priority zones, described in more detail
below. Graph 400 also shows pressure 412, which may be essentially
the rupture pressure of the steel cylinder or can 107 without the
benefit of any prestressing wire 111 or concrete core 105 strength.
The right hand portion of pressure 412 is in common with the right
hand portion of curve 410 wherein a large number of wires 111 are
broken. Thus, the condition of wire 111 may not be relevant for
pipe operated at maximum anticipated pressures significantly below
pressure 412, since can 107 may adequately withstand the
pressure.
[0075] Referring further to FIG. 4, an exemplary embodiment of the
present invention is a system or method of facilitating the
management of a pipeline, such as determining whether or when to
repair or replace pipe (e.g., PCCP) that involves using a relation
or graph such as graph 400 of pressure versus a quantification of
the degradation of the structural integrity of the pipe (e.g.,
100). As mentioned above, the relation or graph 400 has repair
priority zones of high risk (e.g., 1a and 1b) and low risk (e.g., 4
and 5), plus additional zones of intermediate or medium risk (e.g.,
2a, 2b, 3a, and 3b). (However, other zones could be considered
high, medium, or low risk, or higher or lower, e.g. relative to
each other.) The quantification of the degradation of the
structural integrity of the pipe may include, for example,
determining the quantity of broken wires (111 shown in FIG. 1), and
the pressure may be, for example, the maximum pressure anticipated
in the pipe 100. In the exemplary embodiment shown, the relation or
graph 400 further shows the pressure 412 for the ultimate strength
of the cylinder or can 107. This may be the pressure at which the
can 107 will rupture absent any prestressing force (e.g., from wire
111).
[0076] Still referring to FIG. 4, and occasionally to FIG. 1, the
repair priorities or repair priority zones in the exemplary
embodiment shown in FIG. 4 are as follows: Priority 1a is generally
located where the expected maximum pressure exceeds by more than a
predetermined amount, the rupture pressure of the composite pipe
100 given the number (or effective number) of wire 111 breaks that
were found. Thus, priority 1a is generally located where the
maximum pressure exceeds curve 407 for the quantity of wire breaks
found during inspection. The predetermined amount may be, as
examples, 10 percent of the rupture pressure (depicted by curve
410). Priority 1a is the highest priority or zone of highest risk
shown on graph 400.
[0077] Priority 1b is generally located where the expected maximum
pressure exceeds, by less than the predetermined amount, the
rupture pressure of the pipe 100 given the number (or effective
number) of wire 111 breaks that were found. In other words,
priority 1b is generally located between curves 410 and 407.
[0078] Priority 2a is generally located where the expected maximum
pressure exceeds the pressure that causes the concrete core 105 to
crack (depicted by curve 420), by more than the amount delineated
by curve 415, but is generally below the rupture pressure of the
pipe 100 (the rupture pressure depicted by curve 410) given the
number (or effective number) of wire 111 breaks that were found.
Priority 2a is generally located between curves 415 and 410, and
above (can 107 rupture) pressure 412 (of the composite pipe
100).
[0079] The action pressure or curve 415 may be generally located,
as an example, halfway between the onset of core 105 cracking
(curve 420) and rupture pressure (curve 410). However, the action
pressure or curve 415 may be located higher or lower for various
applications, as may be determined by experience. For instance, if
experience shows that pipe sections just below curve 415 often fail
in service, then it may be advisable to lower curve 415 so that
such pipe sections are classified in a higher repair priority and
are then repaired or replaced before they fail. On the other hand,
if pipe sections designated for replacement are hydrostatically
tested to failure, and it is found that they consistently fail far
above curve 415, then it may be advisable to raise curve 415 such
that sections of pipe are classified in a lower repair priority to
avoid the unnecessary expense of repairing or replacing sections of
pipe that are fit for service. In addition, although only one curve
415 is shown, additional action pressures or curves defining
additional priority zones or classifications may be utilized, as
would be apparent to a person of skill in the art.
[0080] Continuing to refer to FIG. 4, in the exemplary embodiment
illustrated, priority 2b is generally located where the expected
maximum pressure exceeds the pressure that causes the concrete core
(e.g., core 105 shown in FIG. 1) to crack, by less than the amount
delineated by curve 415, and is further less than the rupture
pressure of the pipe 100 given the number (or effective number) of
wire 111 breaks that were found. Priority 2b is located between
curves 420 and 415, and above pressure 412.
[0081] Priority 3a is generally located where the expected maximum
pressure exceeds the pressure that causes the concrete core 105 to
crack, by more than the amount delineated by curve 415, but the
expected maximum pressure is less than the rupture pressure of the
pipe 100 given the number (or effective number) of wire 111 breaks
that were found. Priority 3a is generally located between curves
415 and 410, and below pressure 412.
[0082] Priority 3b is generally located where the expected maximum
pressure exceeds the pressure that causes the concrete core 105 to
crack, by less than the amount delineated by curve 415, and is
therefore significantly less than the rupture pressure of the pipe
100 given the number (or effective number) of wire 111 breaks that
were found. Thus, priority 3b is generally located between curves
420 and 415, and below pressure 412.
[0083] Priority 4 is generally located where the expected maximum
pressure is less than the pressure that causes the concrete core
105 to crack (and is therefore much less than the rupture pressure
of the pipe) given the number (or effective number) of wire 111
breaks that were found. Priority 4 is generally located to the left
of, or below, curve 420, and is above pressure 412. Priority 4 is
the zone in which PCCP is typically designed to operate.
[0084] Priority 5 is generally located where the expected maximum
pressure is less than the pressure that causes the concrete core
105 to crack (and is therefore much less than the rupture pressure
of the pipe) given the number (or effective number) of wire 111
breaks that were found. Priority 5 is generally located to the left
of or below curve 420, and is below pressure 412. Priority 5 is the
lowest risk zone shown on graph 400.
[0085] Generally, the lower the number of the priority zone
described above, the greater the risk or urgency that pronounced
action be taken in the management of the pipe 100 such as repairing
(step 327 in FIG. 3) or replacing (step 324 in FIG. 3) the pipe
100. Zones 2a and 2b are considered to be a higher priority than
zones 3a and 3b because additional wire 111 breakage will
theoretically not lead to pipe 100 failure in zones 3a and 3b since
the anticipated maximum internal pressure is less than the pressure
required to rupture the can 107 absent any prestressed wires 111.
Although cracking of core 105 may allow water 106 to leak into can
107, it has been found that corrosion of the embedded steel
cylinder or can 107 may be a very slow process, even if the
concrete core 105 is cracked. However, embodiments of the present
invention may take into consideration deterioration of can 107 such
as via corrosion. This may be particularly important where the pipe
is operated for a long time below (can 107 rupture) pressure 412
(e.g. in zones 3a or 3b).
[0086] Returning once again to FIG. 2, the analysis or program
outputs or recommended action 260 may include tracking the
condition of the pipe. In embodiments where a computer or processor
230 is used, the computer or processor 230 may store design,
configuration, and repair history for the pipeline, which may be
input (at least at one time) as parameters (e.g., 201-207, for
example, via step 305 shown in FIG. 3). This may include design
information (e.g., step 305) and as-built conditions for the piping
system, and may be useful in outage and emergency situations where
rapid and accurate feedback may be essential. The computer
(processor 230) may also predict trends such as considering the
element of time-related degradation rate. As an example, the
computer or processor 230 may calculate the time interval that may
be used to predict when a degraded pipe spool or section will enter
the next zone of risk, classification, or repair priority, using
the following algorithm: 1 TIME INTERVAL TO ENTER REPAIR PRIORITY X
= WB INCREASE NEEDED TO ENTER PRIORITY X RATE OF WB INCREASE PER
UNIT TIME = ( xWBT - GWB ) WB CORROSION RATE PER UNIT TIME
[0087] where:
[0088] WB=number of wire breaks
[0089] xWBT=wire break threshold, i.e., the number of wire breaks
it takes to enter repair category X. (from engineering review of
prestress concrete cylinder structural performance data, and pipe
management risk assessment).
[0090] GWB=governing wire break, i.e., the number of wire breaks
used to determine repair priority X. (from engineering review of
remote field eddy current data).
[0091] The computer or processor 230 may also output repair
prioritization, operating methods, design, maintenance and repair
alternatives, or some combination of these.
[0092] Referring primarily to FIG. 5, a further exemplary
embodiment of the present invention is a method 500 of managing or
facilitating the management of pipe (e.g., pipe having a plurality
of sections of PCCP). Method 500 may include, for example, the
steps of inspecting the pipe (step 302), acquiring or inputting
design parameters (step 305) acquiring or inputting inspection
parameters (step 308), and acquiring or inputting the internal
pressure (step 311), which may be an estimated maximum pressure
that is likely to exist in future service as described above. All
or part of the step of acquiring or inputting design parameters
(step 305) may be performed before the inspection of the pipe (step
302), and once the design parameters are acquired or input (step
305), it may not be necessary to repeat this step when additional
inspections (step 302) are performed in the future. Method 500 may
also include the step of calculating the crack onset pressure
(e.g., of core 105), for instance, absent any prestress (in wire
111). This step is also described above.
[0093] In the example of Method 500, a determination may then be
made whether the internal pressure (input in step 311) exceeds the
crack onset pressure (calculated in step 541) (step 543). If not,
then the risk of pipe failure is fairly low (zones 3a, 3b, or 5
shown in FIG. 4), and in the exemplary embodiment depicted in FIG.
5, no further action is taken other than to determine when to
inspect the pipe again (step 332), and to wait until it is time to
perform the next inspection (step 335). However, as would be
apparent to a skilled artisan, in other embodiments, other action
may be taken, which may include further analysis and classification
into zones 3a, 3b, or 5 shown in FIG. 4.
[0094] If the internal pressure exceeds the crack onset pressure
(as determined in step 543), then FIG. 5 shows the steps of
calculating the maximum load of the longitudinal strips of the core
105 (step 546) (the analysis of the strips was described in more
detail above). If the internal pressure exceeds the crack onset
pressure (as determined in step 543), then in the case of PCCP, the
maximum load of the can 107 is also calculated (step 548)
(generally pressure 412 shown in FIG. 4). The maximum load of the
longitudinal strips of the core 105 (calculated in step 546), and
the maximum load of the can 107 (calculated in step 548) may be
used to calculate the rupture pressure of the pipe (step 551), as
described above. The rupture pressure of the pipe (calculated in
step 551) may, for instance, be a point on curve 410 illustrated in
FIG. 4 for the corresponding number of broken wires (e.g., input in
step 308).
[0095] In the next step shown in the exemplary embodiment
illustrated in FIG. 5, the action pressure between the crack onset
pressure (calculated in step 541) and the rupture pressure
(calculated in step 551) is calculated (step 556). The action
pressure between the crack onset pressure and the rupture pressure
may be, for instance, the same or analogous to curve 415 shown in
FIG. 4 and described above. Once the action pressure is calculated
(step 556), a determination is made whether the internal pressure
(input in step 311) exceeds the action pressure (step 563). If so,
then in the exemplary embodiment depicted in FIG. 5, action is
taken (step 570), e.g. pipe management action. This action (of step
570) may involve, inter alia, repairing, replacing, or monitoring
the pipe, for instance, as described in more detail elsewhere
herein. Pipe management action in this and other embodiments, may
also (or in the alternative) include other activities such as
making operational changes to reduce the pressure or flow rate in
the pipe, adding devices or procedures to relieve or reduce surge
or water hammer, constructing a back-up pipeline to be used if the
original pipeline fails, stockpiling materials or equipment or
arranging for properly skilled labor to be available in the event
repair or replacement is needed, or initiating action to reduce the
harm or damage that would be caused by a failure. Pipe management
action may even further (or in the alternative) include doing
nothing (as used herein, "doing nothing" may include undertaking no
new pipe management action for the section of pipe, e.g. until the
next time to inspect the pipe, but would generally not preclude
initiating action that would have been taken anyway, such as using
or cleaning the pipe), monitoring the pipe differently, inspecting
the pipe sooner, initiating any of the above identified pipe
management actions sooner, or other action that may be identified
by a person of skill in the art.
[0096] In the exemplary embodiment depicted in FIG. 5, if the
internal pressure (input in step 311) is less than the action
pressure (compared in step 563), then the risk of pipe failure may
be fairly low (zones 2b or 3b shown in FIG. 4), and no further
action may be needed, other than to determine when to inspect the
pipe again (step 332) and to wait until it is time to perform the
next inspection (step 335). As would be apparent to a person of
skill in the art, other embodiments of the present invention may
involve other calculations and comparisons, for example, to
differentiate between the various zones depicted in FIG. 4.
[0097] FIG. 6 illustrates, as a further exemplary embodiment, a
method 600 of managing or facilitating the management of pipe or a
pipeline, (e.g., PCCP). The present invention (e.g., Method 600)
may be applied, for instance, to each section or spool of pipe
(e.g., each bell and spigot section), or for larger sections of
pipe, up to the entire pipeline. Method 600 may include the step of
storing design data (step 605) for the pipe (e.g., pipe 100 shown
in FIG. 1). The design data (of step 605) may include dimensions of
the pipe 100, external loading on the pipe 100 and other design
data described herein, for instance, with reference to step 305 of
FIGS. 3 and 5. As an example, method 600 may involve a computer or
processor (e.g., processor 230 shown in FIG. 2) which may store
e.g., 100 design drawings, and data for 150 degraded PCCP spools or
sections and 100 repaired PCCP spools or sections, or what is
needed for storage for the particular application.
[0098] Still referring to FIG. 6, method 600 may also include the
step of inspecting the pipe (step 302), which may be as described
above, and may include an evaluation of the quantity of broken or
failed wires (e.g., wires 111 shown in FIG. 1, for instance, within
a predetermined length of pipe (e.g., pipe 100). The predetermined
length may be, for example, one spool or section of bell and spigot
pipe. However, shorter or longer predetermined lengths may be used,
for instance, as would be conducive to inspection, repair, or other
pipe management action. Method 600 may further include the step of
estimating pressure (step 611) which may be the maximum pressure
that will, or is expected to (e.g. is likely to), exist within pipe
100 in future service. The pressure (of step 611) may be the same
or similar to the pressure of step 311 described above with
reference to step 305 of FIGS. 3 and 5.
[0099] Method 600 may also include a step of facilitating a
determination or designating a classification (step 660 (e.g., for
the condition of the pipe). This step may involve using the design
data for the pipe (e.g., stored in step 605), the quantity of
failed wires (e.g., from step 302), and the maximum pressure (e.g.,
from step 611). The inspecting step (step 302) may be repeated at
different times (e.g., along with other steps as shown in FIG. 6),
and method 600 may include the step of tracking the condition of
the pipe 100, such as tracking changes (step 640), for example, in
the quantity of failed wires 111 over time. For instance, tracking
changes (step 640) of method 600 may include calculating the rate
of wire 111 failures, and predicting when pipe 100 will enter the
next lower classification (designated in step 660) or zone (e.g.,
of risk as shown in FIG. 4 and described above with reference
thereto).
[0100] Method 600 generally also includes the step of taking,
initiating or implementing pipe management action (step 670) which
may be based on the classification (e.g., of step 660) or zone (as
shown in FIG. 4). Each classification (e.g., of step 660) may have
a corresponding action (taken in step 670), which may be, as
examples, doing nothing, monitoring the pipe, repairing the pipe,
or replacing the pipe. Method 600 may involve two classifications,
three classifications, or more (e.g., eight classifications
corresponding to the eight zones shown in FIG. 4). As an example,
if there are three classifications, the action corresponding to the
first classification may be doing nothing, at least until the next
inspection; the action corresponding to the second classification
may be monitoring the pipe; and the action corresponding to the
third classification may be repairing or replacing the pipe.
[0101] The parameters or criteria upon which the classification is
determined (e.g., in step 660) may involve crack onset pressure
(e.g., as described above, for instance, with reference to steps
541 and 543 in FIG. 5), rupture pressure (e.g., as described above,
for instance, with reference to steps 551 in FIG. 5), the maximum
load of the can (e.g., as described above, for instance, with
reference to steps 548 in FIG. 5), or an intermediate action
pressure (e.g., as described above with reference to steps 556 and
563 in FIG. 5), or other measurable or calculable parameters or
criteria, including those described herein.
[0102] Still referring to FIG. 6, method 600 may further include
the step of analyzing the pipe 100 for lack of prestress pressure
(step 650). This analysis (of step 650) may be over the pipe's
entire circumference and over a limited length of pipe 100, or it
may be over just a portion of the pipe's circumference, and over a
limited length of pipe. In addition, this analysis (of step 650)
may include analyzing the pipe 100 for lack of prestress pressure
over two limited lengths of pipe with a segment of intact
prestressed wire 111 located between the first limited length and
the second limited length. The segment with intact prestressed wire
111 may be, for instance, more than 3-inches long, and less than
25-inches long, and may involve using the formula described above.
These analyses may be as described in more detail above.
[0103] Still referring to FIG. 6, method 600 may include the step
of analyzing the rupture pressure (step 610), e.g., of the pipe 100
shown in FIG. 1. Thus, the step of designating a classification
(step 660) may include determining whether the maximum pressure
(e.g., estimated in step 611) exceeds the rupture pressure of the
pipe (e.g., curve 410 shown in FIG. 4). Further, the step of
designating a classification (step 660) may include determining
whether the maximum pressure exceeds, by more than a predetermined
amount, the rupture pressure of the pipe (e.g., exceeds curve 407
shown on FIG. 4).
[0104] Method 600 may even further include the step of analyzing
the crack onset pressure (step 620) (e.g., of pipe 100 shown in
FIG. 1). The step of designating a classification (step 660) may
include determining whether the maximum pressure (e.g., estimated
in step 611) is less than the rupture pressure (e.g., analyzed in
step 610) of the pipe (e.g., pipe 100 shown in FIG. 1), and the
maximum pressure exceeds the crack onset pressure (e.g., analyzed
in step 620). Further, the step of designating a classification
(step 660) may include determining whether the maximum pressure
(e.g., estimated in step 611) is closer to the rupture pressure
(e.g., analyzed in step 610) of the pipe (e.g., pipe 100 shown in
FIG. 1), than to the crack onset pressure (e.g., analyzed in step
620), or vice versa. Even further still, the step of designating a
classification (step 660) may include determining whether the
maximum pressure (e.g., estimated in step 611) is less than the
crack onset pressure (e.g., analyzed in step 620). Still further,
method 600 may include the step of analyzing the rupture pressure
of the can 107 (step 612), for instance, without any prestressing
wire 111. Thus, the step of designating a classification (step 660)
may include determining whether the maximum pressure (e.g.,
estimated in step 611) is less than the rupture pressure of the
cylinder or can (e.g., pressure 412 shown in FIG. 4). In other
embodiments, the step of designating a classification (step 660)
may involve, inter alia, identifying any of the repair priority
zones or zones of risk shown in FIG. 4, described herein, or known
in the art.
[0105] Other variations and modifications of the present invention
will be apparent to those of ordinary skill in the art, and it is
the intent of the appended claims that such variations and
modifications be covered. The particular values and configurations
discussed above can be varied, are cited to illustrate particular
embodiments of the present invention, and are not intended to limit
the scope of the invention. It is contemplated that the use of the
present invention can involve components having different
characteristics as long as the elements of at least one of the
claims below, or the equivalents thereof, are included.
* * * * *