50 Offshore December 2017 • www.offshore-mag.com
Several factors make the full-cure composite
sleeve installation process more desirable than
the wet-wrap process. The full-cure application
process eliminates the wet-wrap variables of
wrap tension, glass alignment, resin saturation,
composite length and the installation variables
caused by field conditions. The mechanical prop-
erties of the full-cure wrap are more consistent
and better defined than those of the wet-wrap.
Composites in action
Composites have been applied to a range
of offshore repairs. In one case, ultrasonic
tests revealed several severe internal defects
in a 16-in. (406-mm) pipeline running into the
main high-pressure separator on a production
facility offshore West Africa. The erosion was
significant, affecting multiple places along the
pipe and growing at such a rate that imminent
failure was likely. If the damage were to reach
a critical point, the platform would have to be
shut in, resulting in a huge loss of production.
In addition to the financial impact, there was po-
tential for considerable environmental impact in
the event that the eroded pipe developed a leak.
The operator needed a way to reinforce the
pipe without halting production. The goal was
to find a safe and reliable repair that would
allow the line to function safely until the next
planned shutdown, nearly a year away.
A Clock Spring Contour repair was designed
for the offshore asset in accordance with ISO
24817 2015 guidelines, which provide requirements and recommendations for qualifying,
designing, installing, testing, and inspecting the
external application of composite repair systems
to corroded or damaged pipework, pipelines,
tanks, and vessels used in the petroleum, petrochemical, and natural gas industries.
A team of trained technicians cleaned the
section of damaged line using power tools to
remove the external coating and then bristle
blasted it to create a surface profile equivalent
to SA2.5 (which requires cleaning to remove
all rust, coating, and mill scale to produce a
near-white surface) before applying the adhesive, placing the repair unit and putting it
under compression, and allowing it to cure to
permanency. With the repair completed, the
platform continued to operate without incident
until the planned shutdown 12 months later,
when the damaged section was scheduled to
In another instance, an operator offshore
Malaysia discovered extensive pitting in a 12-in.
(305-mm) riser with back-to-back bends while
conducting a riser inspection on an offshore
production facility. In some portions of the pipe,
pitting had resulted in 60% wall loss. It was
imperative to repair the line quickly without
disrupting production, so the company chose
to address the problem with a composite repair.
A team of specially trained local experts
cleaned the riser, grit-blasting it to an SA 2. 5
surface prior to applying the composite repair.
Once the area was thoroughly cleaned, repair
technicians identified the defects and marked
them so they could be appropriately treated. The
defects, which were concentrated at the bends,
were first repaired with 3-in. (76-mm) wide Snap
Wrap strips along a 6-ft ( 1.8-m) length of pipe.
In cases like this, where Snap Wrap applied
around pipe bends is placed with spacing that
exceeds 0.5 in. ( 13 mm), the repair is overlaid
by a Clock Spring Contour system. In this
application, Contour overwrapped the entire
16.4-ft (5-m) length of the repair to create a solid
covering. This hybrid system of prefabricated
sleeves and in-the-field cured composite repair
merges a robust structural laminate with a
flexible protective outer composite jacket. The
repair is designed to last for two decades.
This was a rapidly executed repair, performed in a day and a half of on-site work. A
small team carried out the repair with minimal
disruption to daily activities and without taking
the riser out of service.
On another asset in the Middle East, corro-
sion was identified on the riser support clamps
that secured the production risers to the hull.
The 14-in. (610-mm) heavy wall structural cross
member was damaged across a length of 26. 25
ft ( 8 m). Severe external corrosion, which in
some cases amounted to 80% metal loss on the
structural member designed to hold the riser
support clamps, was jeopardizing the safety of
hydrocarbon production. The company needed
a solution that could be carried out offshore
in a short time frame with little disruption to
Performing the repair required the con-
struction of an engineered heavy-wall com-
posite sleeve, manufactured in 24-in. (600
mm) widths using bi-axial glass architecture.
The specialized solution produced extended
sleeves that would cover a longer length of
pipe than a traditional repair.
A trained and certified team of installers applied extensive filler and molding to rebuild the
pipe surface to the original outer diameter and
installed the sleeves cut to length in a brick wall
fashion. When the repairs were completed, the
riser holding clamps were put back into service.
This repair averted an incident and allowed
the production platform to safely continue operations both during and following the repair.
Composite repairs have become more common on offshore oil and gas assets because
they are safe, effective, and relatively simple
to execute. While they are newly being consid-
ered on a larger scale for offshore applications,
they have a long track record of successful
application in other industries. Today’s com-
posites are the result of a years of engineering
efforts and extensive testing that have resulted
in a cost-effective and expedient alternative
that eliminates heavy lifting and hot work,
delivering effective and long-lasting repairs.
The successful execution of a range of
composite repairs illustrates the viability of
composite solutions for offshore oil and gas
assets. The ease, speed, and effectiveness
of composite repairs have the potential to
dramatically change the way owners and op-
erators contend with corrosion and extend
production life on offshore assets. •
Composites compete under water
Composites are suitable for a broad range of applications, but there are some conditions in which they are not an appropriate repair solution. Composites are unsuitable for situations where the surface cannot be properly prepared, which would lead
to issues with bonding or sealing, and they cannot be applied on concrete.
They can, however, be used on condensing pipes and in a range of conditions,
including under water to depths of 30 ft, which makes them appropriate for installations that heretofore have been carried out by underwater welders.
Traditionally, welding below the water line is either dry, also called hyperbaric
welding, or wet. Dry welding requires a structure to be built around the weld area
so water can be pumped out to create a dry environment. The area can be small
(confined to the damaged area) or large enough for the welder to physically enter.
For large areas, oxygen is pumped out of the enclosure, and helium is pumped in.
Wet welding, because it is done in the water, introduces the need for a diver properly
outfitted with diving equipment, which means it introduces the risks associated with
diving. Electric shock is another risk, as is the possibility of explosion if the welding
process is not well controlled.
Because hyperbaric welding is better controlled, it produces a more reliable weld
than underwater welding. The problem is that environmental conditions are not always conducive to dry welding. And many owners are not comfortable with the risks
– both personal and structural – inherent to wet welding.
A repair sleeve can be placed using a special underwater adhesive. The repair,
which can be carried out by a trained diver, is relatively straightforward, following
the same approach as a repair in dry conditions. Because this approach requires no
construction or complex installations to create a dry environment, a composite repair
can produce a lasting repair without any hot work. This capability introduces a new
alternative for underwater line repair.