THE
OFFSHORE
COATING
TECHNIQUE
Renato Sanchez, Engineering
Manager, and Caroline A.
Fisher, Technical Writer, CRTS,
Inc., USA, examine the use of
internal field joint coatings in
unique, offshore locations.
W
hen building a pipeline of nearly 13 000 welds,
corrosion management is naturally part of the
design. Unfortunately, while the majority of
pipelines are built with reasonable monitoring and
inspection plans in place, little attention is paid to the bare steel
on the internal field joints (IFJs) where leaks and internal corrosion
often occur. This bare steel represents approximately 2% of the
entire pipeline, yet easily becomes the pipeline’s weakest link if
not protected.
To prevent internal corrosion, one of the largest oil
companies in the world awarded CRTS an offshore project in
the Gulf of Arabia near Qatar in 2012. This pipeline crosses the
Hasbah and Arabiyah gas fields and CRTS completed its corrosion
prevention services in January 2015. The operation was based at
the company’s facility in Abqaiq, Kingdom of Saudi Arabia, and
at that time was the largest project ever awarded to CRTS. Why
was IFJ coating chosen over other corrosion prevention methods?
Corroded, leaking pipelines on the ocean floor are not a viable
option for owners or the environment. Coating the IFJs provides
the most mitigation for the money.
Preventing corrosion from the inside out
Designing a pipeline to endure a lifetime means employing
corrosion prevention techniques that do more than meet the
minimum standards; the pipeline should have built-in measures,
such as corrosion prevention coatings, that prevent corrosion or
greatly mitigate it. Built-in prevention does not exclude future
inspection and monitoring; corrosion prevention coatings do
however add many benefits such as:
)
Maintain product purity.
)
Increase pipeline longevity.
)
Reduce internal corrosion.
)
Reduce pipeline flow friction, which minimises pressure drop.
)
Reduce pipe wall thickness requirements.
)
Diminish or eliminate pipeline leaks.
)
Protect the environment from leaks, ruptures or spills.
These benefits are inherent to the parent coating of
pipelines, but when also applied to the internal field joint, they
create seamless, defect-free protection from internal corrosion.
These benefits also address the gravity of internal corrosion
consequences: deepwater pipelines need defect-free, continuous
internal coatings to complement the expensive and complicated
methods of monitoring and inspection.
Customised equipment for best practice
The sheer number of welds and impact on the marine
environment with a project of this size is enough to warrant
specialised equipment and testing. The complexity of keeping
equipment running efficiently while performing also warranted
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