safely managing the life cycle of pipelines

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Pipeline Integrity Remediation and Repair
Stress Engineering Services, Inc. Chris
Alexander, Staff Consultant chris.alexander_at_stress
.com

• safely managing the life cycle of pipelines

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Disclaimer

• Although Stress Engineering Services (SES)
  will discuss specific composite repair systems
  and products today, SES does not endorse any
  particular composite repair system.
• Users are encouraged to know and understand
  the capabilities and limitations of each
  composite repair system. SES has observed
  incorrect distribution and improper use of
  technical data and information.

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Pipeline Repair(the why, what, and how)
If you were to develop a composite repair system,
how would you design it? What would be the
important design features?
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Pipeline Repair(the why, what, and how)

• Consider a needs statement for pipeline repair
• What are the fundamental issues?
• For what period of time should the repair be
  designed?
• What is important from an installation and
  quality control standpoint?

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Todays Presentation

• Understanding why we repair pipelines
• Background in pipeline evaluation and repairs
• Examples of when composites can be used to repair
  pipelines
• Background on the major pipeline repair systems
  using composite materials
• U.S. government regulations
• Guidelines for repair using composites and test
  program elements
• Repair of dents and gouges (mechanical damage)
• Question Answer Session

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Laying the Groundwork

• In terms of pipeline damage and repair, the
  key to operating pipelines in the future is to
  properly integrate experience and technology to
  effectively assess damage as it is found. When
  this is done, the pipeline community can respond
  appropriately and continue the safe operation of
  pipelines.

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The Key Components
The Optimized Solution putting it all together
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Points to Consider

• In terms of characterization, the sweet spot
  exists in balancing between the following call
  levels
• too few dangerous due to potential failure
  levels
• too many expensive and generates a false sense
  of alarm
• Defect characterization often involves developing
  an appropriate priority level to rank the
  severity of defects

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The Assessment Process
Finding the defects (inspection technology)
Detection
Assessing the severity (experience, operating
history, testing, analysis, and research)
Characterization
Defining acceptability (rank defects if
required) (evaluation relative to codes,
standards, and government regulations)
Determination
Repair (if appropriate)
Repairing the damage (if required) (use available
technology to determine the best repair options)
Restore Service
Continue operation (restore service once
integrity has been reestablished)
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Typical Aims of PipelineRepair Methods

• Restore strength to damaged pipes
• Reduce strain in damaged areas of pipe
• Seal corroded area of pipe from further
  development of corrosion

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Target Applications of Repairs

• Gas and Liquid Pipelines
• Water Pipelines
• Small Utility Lines
• Chemical Plants
• Gas Plants and Refineries

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Uses of Composite Materials(repair and
structural reinforcement)

• Metal wall loss (due to corrosion)
• Plain dents
• Mechanical damage (dents with a gouge)
• Re-rating pipeline system to achieve higher
  operating pressures
• Corrosion repair and replacement
• Under insulation coating (UIC)
• Wear-resistant coatings (e.g. saddles)
• Underwater coatings

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Types of Composite Repairs(used to repair
pipeline systems)

• Wet lay-up systems (e.g. Armor Plate Pipe Wrap,
  Black Diamond, and Aquawrap)
• Monolithic
• Can be applied to non-straight geometries
• Versatility in range of epoxy products (e.g.
  underwater, high temperature, etc.)
• Layered systems (e.g. Clock Spring and PermaWrap)
• First widely-used composite repair system
• Layered repair system
• Limited to repair of straight pipes

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Government Regulations(from the U.S. Department
of Transportation)
On January 13, 2000, Pipeline Safety Gas and
Hazardous Liquid Pipeline Repair, was issued by
the RSPA of the Department of Transportation,
went into effect. According to this document,
the requirement for repairing corroded and dents
in pipelines is as follows, repaired by a
method that reliable engineering tests and
analyses show can permanently restore the
serviceability of the pipe.
Page from the RSPA-98-4733 document
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Guidelines for Evaluation of Composite Repair
Methods
The basic fundamental issues for evaluating
composite repair methods are as follows

• Strength of the composite material
• Environmental effects (e.g. cathodic
  disbondment, temperature, acids and alkalines)
• Effects of pressure (both static and cyclic)
• Mechanics of load transfer from pipe to wrap
• Long-term performance issues
• Consistency in application and quality control
  in manufacturing

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Elements of a Typical Testing Analysis Program

• Corrosion repair (burst testing)
• Cyclic pressure effects on burst strength
• Repair of mechanical damage (static and cyclic)
• Load transfer analysis using strain gages and
  Finite Element Analysis (FEA)
• Tensile testing of composite materials
• Adhesive lap shear testing
• Effects of pressure at time of installation
• Long-term testing

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Specific Technical Items(discussed in todays
presentation)

• Corrosion Repair and load transfer
• Repair of Mechanical Damage (dents with gouges)
• Repair of Pipe Fittings
• Pipeline Re-rating using composites

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CORROSION REPAIR
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Load Sequence of Composite Repairs during
Pressurization

• Pipe and wrap stressed as internal pressure
  increased (load distribution dependant upon
  relative stiffness of two components)
• Once yielding in corroded region occurs, local
  stiffness of pipe reduced and load transferred to
  wrap
• Final burst pressure governed by ultimate
  strengths of pipe and composite materials

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Mechanics of CompositeRepair Methods
Equation defining burst pressure
P Internal pressure s Material failure
stress t Thickness of material r Radius
of pipe
Note The above calculation is based on thin-wall
shell theory and is not applicable for
thick-walled pipes with diameter to wall
thickness ratios less than 20.
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Pipe-to-Composite Load Transfer (Hoop Strain
During Pressurization)
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MECHANICAL DAMAGE
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Repair of Mechanical Damage
Based upon reportable incident data, third-party
mechanical damage is the leading cause of
pipeline failures in the United States.
Mechanical damage normally involves a dent with
some type of gouge with cracks.
Process for repairing mechanical damage with
composites

• Inspect dent for presence of gouges and cracking
• Remove metal in cracked area by grinding
• Insure removal of cracks by Magnetic Particle or
  Dye Penetrant
• Fill in dented region with epoxy putty
• Repair damaged region using the appropriate
  number of wraps

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Dent Configuration
Dimples created in dents
Dent test rig
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Mechanical Damage(Test Methods)
Dent installation rig
Installation of Armor Plate Pipe Wrap
Dye penetrant inspection
Armor Clamp installed on dent
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Verification of Crack Propagation

• The gouge in Sample P3C (from PRCI Research
  project) developed a crack that propagated from
  an initial gouge depth of 20 (a/t) to a final
  crack depth that was 50 of the wall thickness

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Mechanical Damage Fatigue Testing
(Results for Armor Plate Pipe Wrap, Aquawrap, and
Clock Spring similar)
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2
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Index of curves 1 Dents with gouges not
repaired 2 Dents with gouges repaired by
grinding out gouge 3 Dents with gouges repaired
using composite material and grinding
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MECHANICAL DAMAGE (Conclusions)

• Samples repaired by grinding had fatigue lives
  that were approximately 10 times those of
  unrepaired dents and gouges.
• Those defects that were repaired by grinding and
  composite had fatigue lives that were
  approximately 1,000 times those of unrepaired
  dents and gouges.
• Slight improvements were obtained over the
  grinding/composite repair with the installation
  of the stainless steel clamp.

- composite testing based on Armor Plate Pipe
Wrap, Aquawrap, and Clock Spring
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REPAIR OFPIPE FITTINGS
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Repair of Pipe Fittings
(Test results from Armor Plate Pipe Wrap test
program)
6-in STD Tee (50 corrosion) Unrepaired 6,546
psi Repaired 7,500 psi
6-in STD Elbow (50 corrosion) Unrepaired 4,532
psi Repaired 6,780 psi
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INSTALLATIONAND APPLICATION TECHNIQUES
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Steps in Pipeline Repair

• Locate damaged section(s)
• Assess severity of damage (e.g. corrosion,
  mechanical damage, etc.) and determine if repair
  is possible
• Calculate required number of wraps (if
  appropriate for respective repair type)
• Clean and prepare pipe (surface preparation
  critical)
• Install composite repair
• Allow repair to cure per manufacturers
  recommendations
• Restore pipeline environment (e.g. backfill and
  re-pressurize)

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WRINKLEBENDS
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Wrinkle Bend Fatigue Testing

• 36-in x 0.281-in pipe material
• Wrinkle bends created using a CRC bending machine
• Local wrinkle bend depths of 2, 4, and 6 percent
  of pipe diameter studied
• Three samples cycled until failure (or reasonable
  number of cycles applied)
• Testing performed as part of research on rock
  dents for the American Petroleum Institute (1998)

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Wrinkle Bend Fatigue Testing(photos of test
set-up)
Four percent Wrinkle
Three 36-in pipe samples
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Wrinkle Bend Fatigue Testing(cycle test results)

• 2 percent wrinkle - NO failure after 44,541
  cycles
• 4 percent wrinkle - failure after 2,791 cycles
• 6 percent wrinkle - failure after 1,086 cycles

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Wrinkle Bend Fatigue Testing(plots of local
profiles)
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Observations on Current Composite Repair Methods

• For more than 10 years, the pipeline industry has
  been making repairs using composite materials
• A significant body of research exists addressing
  a variety of repair types
• It is critically important to consider long-term
  performance (especially the adhesives and resins)
  when considering the use of composite materials

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QUESTION ANSWER SESSION