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Abstract of Papers:-
Long Term Durability of Clock Spring Repairs – Recent Removals and Examinations
The Clock Spring repair system was the subject of a rigorous Research and Development
program conducted under the management of the Gas Research Institute (GRI). The
program extended over a decade and considered long term degradation.
As part of this program an extensive field validation program was required by the US
Department of Transportation. This requirement was added to verify the laboratory
experimental results and to provide and to validate the real world behaviour on actual
pipelines. Statistical sampling was required and a matrix of various soil types, location and
environmental conditions were created as the basis for the field validation study. The
results were published in the public report GRI 1998-0032. This peer reviewed report was
relied upon by the industry and regulators as the basis of documentation to suggest
amended code language for both liquid and natural gas pipeline which was subsequently
proposed and adopted in CFR 192 and 195.
Abstract of Papers (cont’d) :-
Over two decades of time has past since the GRI established the first steering committee of
industry experts to design the scope and methods of the investigations. Subsequently
several hundred thousand Clock Spring repairs have been made. Units have been installed
in many countries and in almost all conceivable environmental conditions.
The purpose of this paper is to document where various repairs have been taken out of
service and to document the subsequent investigations and findings in respect to the
condition and overall effectiveness of the repair.
Clock Spring®
Long Term Durability of Clock Spring
Repairs: Recent Removals and
Examinations
Darren Looi
Asia Pacific Representative
Clock Spring Company, L.P.
Abstract
With over 20 years of commercial
experience and over 750,000 repairs
installed in over 72 countries the purpose of
this paper is to case study recent removals
of Clock Spring repairs from high pressure
pipelines and riser service and to
substantiate the original test and validation
data and acceptance of Clock Spring as a
permanent repair system.
The history
The removals
The conclusions
The History
The R+D of Clock Spring started in the early
1980’s and was driven by actual pipeline
operators who were interested in a repair
alternative to:
- Welded steel sleeves
- Hot tapping / cut and replace
The History
Industry pre-requisites were established:
- Repair had to be proven to be permanent
- Easy and quick to install for all pipe diameters
- No hot work
- No shielding of C.P
- No shut down of pipeline operation
Industry pre-requisites cont….
- Suitable for use in all environments andsoil types.
- A standard off the shelf product to suit alldefects of up to 80% metal loss on anyoperating pressure pipeline.
The History
Industry pre-requisites cont….
- Validated with a mathematical modelwhich allows permanency to beconfirmed in accordance to variousdefect assessment criteria (B31.G,modified and effective area), classlocation and based on material propertiesderived from an extrapolation of a 50 yearperformance.
The History
The History
A steering committee wasestablished under the auspices of theGas Research Institute (GRI) andincluded:
- The GRI
- Battelle
- South West Research
- Kiefner & Associates
Steering committee cont….
- Stress Engineering Services
- North Western University
- ITW – Devcon
- PRCI
- Pipeline Operators
- NCF Industries
- The Clock Spring Company, L.P.
The History
The History
In addition the US DOT/OPS providedtheir own requirements and pre-requisites for an acceptable repairdesign including:
• Tensile tests
• Stress rupture tests
• Lap shear strength
• Durability
• Burst pressure testing
• Adhesive testing
• Fatigue testing
• Field tests
• Durability tests
The History
The GRI R+D program took 10 years and involved both in-
depth laboratory and in-field testing to determine if a
composite product could meet the established industry,
GRI and DOT pre-requisites and provided thorough
evaluation of:
- The most suitable fibre type and architecture
- Resin matrix
- Adhesive and filler systems
Composite Coil
• Composite coil
• E-glass filaments
• Polyester resin
• Memory matrix
• Conforms tightly to
pipe
• Unidirectional
filaments
• Hoop reinforcement
Adhesive
• Methyl Methacrylate
Polymer
• Proprietary composition
• 1200 psi lap shear
strength
Filler
• High compressive strength• Greater than 8,000 psi
compressive strength
• Transfers load from the pipe to the Clock Spring
History
Throughout the 10 year R+D program
topical reports were released by the GRI
for peer review and evaluation.
The GRI stated in 1998 “Several years ago
the research team proved the durability of
the Clock Spring product through
hydrostatic testing and accelerated
corrosion testing.”
History
“These laboratory predictions indicated that
Clock Spring can provide safe repairs
beyond 50 years. However to further verify
its performance required that repaired
sections remain buried for up to 7 years in
actual operating conditions.”
History
“Through this recent field based research
we confirmed repairs will last at least 50
years but we feel that most repairs will last
much longer.”
History
Following this work the DOT accepted the
use of alternative repair technologies for
high pressure oil and gas transmission
pipeline service providing the pipeline is
“repaired by a method that can permanently
restore the serviceability of the pipe as
shown by reliable engineering tests and
analyses.”
History
Many other recognised approvals werealso given allowing the acceptance ofcomposite repair sleeves including:
ASME 31.4
ASME 31.8
API 1160
API 570
History
Clock Spring has now been used
for over 20 years in all regions of
the world.
Africa
Middle East
U.S.A.
Asia
In all environments
The History
Offshore
Desert
Tropical
Underwater
The History
For many applications
Tank Farms
Refinery
Pipe Supports
Structural
The Removals
CASE 1
Location: North America
Pipeline: High pressure natural gas 30”
Repair made in: 2005
Removed in: 2010
The Removals
Reason for removal:
An OLI survey performed in 2009 indicated
corrosion growth under the repair.
Conclusion:
The units were difficult to remove and well
bonded in place. No new corrosion under
the repair was identified.
The Removals
CASE 2
Location: Asia
Pipeline: 20” oil export pipeline.
Initial repair: significant dent due to poor
backfill.
Repair made in: 2006
Removed in: 2010
The Removals
Reason for removal:
Operator decided to cut and replace the
section to allow safe passage of future OLI
surveys.
Repair excavation
Installed Clock Spring after coating removal
Cutting the coil into sections for removal
Cuts in both 3 and 9 o’clock positions
Removing the cut sections by chisel
Crowbars used to prise the coil from the pipe
Layers of the bonded Clock Spring and filler on
the pipe
Final coil removal
Removing the filler from the pipe surface using a
chisel
Final filler removal – no corrosion present
The removed Clock Spring sections including the
original molded filler from the dent section
The Removals
CASE 3
Location: North America
Pipeline: 30” oil pipeline.
Initial repair: 1995 external corrosion and
potential reinforcement of SCC.
Removed in: 2010
The Removals
Reason for removal:
Evaluation of performance of Clock Spring
repair.
Conclusion:
The unit had to be sand blasted and pry
bars used to remove the various layers of
the coil. The coil was well bonded within
each layer and to the carrier pipe.
Conclusion cont….
No evidence of any active corrosion, no
evidence of any cathodic disbondment or
cathodic shielding effects. After 15 years of
service the repair remained sound and
durable.
The Removals
CASE 4
Location: Middle East
Pipeline: 18” high pressure high
temperature oil riser in the splash zone.
Initial repair: 1997 external corrosion.
Removed in: 2006
The Removals
Reason for removal:
The riser was selected for shut down and
replacement and client decided to evaluate
the repair performance.
Conclusions:
The repair was well bonded to the riser and
very difficult and time consuming to remove.
After 9 years …….
Coil cut away in sections to be removed
Cleaning to remove filler, adhesive and fibre still
bonded to the riser
Final preparation for UT inspection
Conclusions
Several more case studies are availableand reported in the correspondingtechnical paper.
- As part of the initial validation processthe US DOT required the GRI to conductlong term field validation.
- This was conducted over a 7 yearperiod and was an integral part of theoverall permanent repair acceptanceand validation of the Clock Springproduct.
Conclusions
- The findings in the above case studiesand removals of repairs with up to 15years operating service are consistentwith the original reported anddocumented long term testing asconducted in the 10 year GRI program.
Conclusions
Conclusions
- The operational history of the case
studied repairs shows the GRI made
sound technical decisions in terms
of the composite architecture used
and the constituent components
within the Clock Spring repair.
- The approvals attributed to the use of a
long term, tested composite repair
sleeves for reinforcement of corrosion
and mechanical damage on high
pressure pipeline and riser systems
has been validated.
Conclusions