to detail each step of the repair process and
showcase the planned operations to mitigate
any risks at an early stage.
Once on location, the system was deployed
over a one-month timeframe during favourable
weather windows, leading to the successful
repair of both risers in April 2017.
Once the repairs were completed, a bespoke restraining system was installed to
support the tie-in location and to avoid any
potential fatigue related issues over the remaining lifetime of the risers. A buoyancy
removal tool was developed to mill away the
buoyancy around a nearby 12-in. riser to cre-
ate a space envelope sufficient for subsequent
coating removal and the remote installation
of the structural restraint clamp.
Pipeline fracture repair
In tandem with the deepwater project
offshore Angola, Hydratight and Connector
Subsea Solutions developed a structural deep-
water pipeline repair clamp for a major NOC,
offshore Western Australia.
A fracture was detected on a 4-in. MEG line
in 830 m ( 2,723 ft) water depth, pressure-rated
up to 400 bar ( 5,801 psi) which required urgent
repair. The operator required a permanent, field-
proven repair, again on a short lead-time.
Due to the location and environment, the
entire project had to be carried out remotely
using ROV compatible tooling. Fur thermore,
the weight of the repair had to be minimal so
as to not overstress the pipe.
The need for a high-pressure repair conflicts with the requirement for a low-weight
solution. Typically, in order to achieve a high
seal pressure the seal needs to be put under
a very high load stress. The load is then nor-
mally transferred through bolting: the higher
the load, the larger the bolting and the surrounding material to react from.
To overcome this challenge, the contractors
designed, manufactured, and installed an inno-
vative diverless structural deepwater pipeline
repair clamp especially for use in high-pressure
environments. The clamp was designed to op-
erate without the need for bolt tensioning. All
activation system technologies and hydraulics
were housed within a separate retrievable tool
to reduce weight, fatigue and cost and was
removed on completion. This would ensure
that the fracture was repaired rapidly and with
minimal impact on the under water environment.
Prior to deployment, the clamp under went
extensive pressure-testing to exceed the 400
Before the clamp was installed, the pipe
was prepared using a new, high performance
ROV-based coating removal tool to ensure the
interface between the pipe and clamp was as
required, and that all sea-growth, debris and
the original protective coating was removed to
provide a clean surface for the repair.
All equipment and tooling was shipped to
the location and once lowered from the deck
of the support vessel, the coating removal tool
was locked onto the pipe. With the pipework’s
protective coating removed, the installation
tool and clamp were slotted onto the pipe and
the clamp installed.
After final pressure testing and verification
of the seal, the installation tool was successfully removed with the repair clamp left as a
permanent repair on the pipe. It is designed
to last 25 years in service. Deployment of the
structural deepwater pipeline repair clamp
makes it possible to repair pipeline fractures
in previously hard-to-reach areas faster and
with lower risks than was previously the case.
Repair and recommissioning
The root cause of the repair, location and
extent of the damage will vary widely from project to project. In any case, early engagement
with the OEMs or third-party design houses
to assess potential solutions on the market are
essential at an early stage to ensure all potential
repair options are available to be considered.
Once the operator has a preference for the
repair solution, consideration for the installa-
tion requirements can then be addressed. To
mitigate operational risk, the key interface points
between the repair products and the original
assets must also be considered. These include
the straightness of the pipe, coating removal and
the pipe cut and end preparation (bevelling).
To ensure successful recommissioning following pipeline repair, it is vitally important
that the foundations of the repair strategy are
sound. This means that no aspect of the repair
should be assumed until the prior step/assess-ment is complete. With all pipeline repairs,
this should encompass root cause analysis
of the damage, understanding of the location,
geography and environment, and assessing
the technical requirements of the pipeline
system predicting future field life. •
James Rowley is Global Subsea Market Development
Manager with Hydratight.
Above: Vertical riser repair solution ready for factory acceptance testing. Below: 4-in. clamp in
preparation for deployment from vessel offshore Australia.