DEEP7 2017 - Subsea 7 - page 8

water injection lines. Until now, it has been
necessary to use a proprietary CRA end
connector, WeldLink®, to terminate the
internal liner for such applications as tie-in
connections.
Procurement and qualification
requirements for WeldLink® connectors are
cost-intensive. Swagelining has recently
developed and qualified a matching
polymer connector, LinerBridge®, to replace
the need for a CRA connector.
With LinerBridge®, the polymer liner welds
are accomplished using an electrofusion
process adapted from proven technology
from the gas utilities industry, and the
external carbon steel welds are made
conventionally without risk of damaging
the underlying liner material.
The qualification programme has included
both simulated reeling and hydrostatic
testing.
The availability of the LinerBridge®
connector now makes the use of polymer-
lined pipe for larger-diameter water
injection lines installed by S-Lay and for
dynamic steel catenary risers an attractive
economic alternative to clad pipe.
The next boundary to be extended
for polymer linings is their use for
hydrocarbon service.
The main technical challenge to be
addressed will be to mitigate and manage
the risk of gas permeation through the
polymer lining, which would expose the
steel substrate to a corrosive environment.
Composite materials
When faced with the need to adapt
to harsher conditions, the oil and gas
industry typically leans towards scaling-
up established technologies rather than
opening up to new materials and tools.
This approach has major limitations
where components become too heavy,
too expensive and too complex to
manufacture or install, which can
especially be the case when considering
High Pressure/High Temperature (HP/HT),
deep and ultra-deepwater developments.
While constantly extending our current
capabilities, Subsea 7 also continuously
evaluates alternative materials and
methods for development. We have
successfully replaced steel with
composites in many subsea structures
such as protection covers or plates.
Although driven by technical require-
ments, these alternative products are
also commercially attractive, which
is the ultimate goal for our clients.
We are also evaluating alternative pipeline
materials such as thermoplastic composite
pipes (TCP), assessing both their technical
and commercial capabilities.
Pipeline in TCP materials provide a fully
bonded structure with a smooth bore
giving superior corrosion resistance,
flow assurance and thermal performance
capabilities to comparable steel pipeline.
In addition, the combination of low weight
and high strength of TCP pipeline material
makes it an attractive enabling solution
for deepwater SURF architecture.
Challenges still remain to be met in practical
pipeline fabrication and installation before
some of these technical advantages can be
realised cost-effectively.
Subsea 7 continues to extend the
boundaries of innovative pipeline material
development to reduce the costs of pipeline
fabrication.
This enables our clients to benefit from
new technologies that can transform the
economics of field development.
programmes have demonstrated a
capacity to meet more critical fatigue
service requirements avoiding the need
to use metallurgically clad pipe for such
applications.
BuBi® lined pipe can be extended to high-
strength steel substrate pipe which is not
normally possible with metallurgically clad
pipe. Butting has demonstrated a capability
to manufacture CRA-lined X80 pipe using
similar equipment to that used for lined
pipe in X65 material, making it possible
to provide high-strength steel pipe with
improved corrosion performance.
Girth welding development by Subsea 7
required a novel approach utilising internal
welding of the CRA material followed by
external welding using C-Mn weld metal.
This welding approach ensured that the
weld metal strength overmatch required
for Reel-Lay could be achieved, which
would otherwise be difficult to accomplish
with a conventional dissimilar weld metal
joint. The suitability of X80 BuBi® has
been demonstrated by full-scale reeling
simulation.
Butting is presently engaged in developing
manufacturing technology to eliminate the
need for internal pressurisation of BuBi®
pipe for reeling.
This is accomplished through the use of an
adhesive layer between the substrate pipe
and the liner which results in an enhanced
grip condition that can be maintained
during reeling to prevent liner wrinkling.
Subsea 7 will work closely with Butting
over the coming months to qualify this
new Mechanically Lined Pipe product for
Reel-Lay applications.
Polymer-lined pipe
The use of polymer-lined pipe, inserted by
the Swagelining process, is well established
for the fabrication of corrosion resistant
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deep7
Technology Magazine from Subsea 7
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