           
| |
Hydra-Lok® Caisson Repair System
|
| Corrosion Damage |
| Many seawater caissons suffer corrosion damage at the pump intake
housing, in the splash zone region or around an uncoated weld. In time, the corrosion can
weaken the caisson significantly, thereby requiring some kind of remedial action
to be carried out in order to prevent further damage from occurring. It
has been known for caissons to separate and fall onto pipelines and other seabed equipment or
they partially come away causing them to swing into structural members,
damaging those members and/or the caisson pump. Installing an
external, bolt-on clamp costs less than replacing the caisson, but requires
diver support and calm weather conditions.
A better alternative is a Hydra-Lok swaged in
place liner, which can be installed in as little as 24 hours and can cost only
20 to 30 percent as much as installing an external clamp using diver support. |
|
| Swaged In Place Liner |
|
The Hydra-Lok
repair installs a steel reinforcing liner – made from compatible
material – inside the caisson to bridge the corrosion damage. After
installation, the liner transfers axial and bending loads across the
weakened section, allowing the caisson to be returned to service
immediately.
The liner is swaged
against the inside of the caisson using proven Hydra-Lok technology. The
Hydra-Lok swaging system has been used to make hundreds of structural
connections on subsea templates and platform jackets around the world
since 1984. The liner is fabricated to a length determined after the
cleaned caisson has been ultrasonically surveyed for thickness. The liner
diameter is controlled such that it occupies minimal annular space. This
permits the pump to be returned to its original location in the caisson.
|
|
Replaces Missing Caisson
Sections
The Hydra-Lok swaged liner
method can also be used to replace caisson sections lost as a result of
corrosion (see illustration
right).
A Weather Independent
Procedure
The Hydra-Lok swaging
operation is conducted from the cellar deck of the platform itself. No
diver or ROV support is required, because the Hydra-Lok tool, which
applies the necessary hydraulic pressure to swage the liner, is remotely
operated and no equipment is deployed external to the caisson. The repair
can be scheduled to the convenience of the platform operator and can be
completed in all but the most severe weather conditions. |
|
|
Reinforcing Corroded Section
|
Replacing Missing
Section
|
Extending Broken Caisson
|
|
No Disruption of Platform
Operations
The Hydra-Lok method is simple
and straightforward and does not disrupt other operations on the platform. Only
the liner, the Hydra-Lok tool and a compact control/power unit are mobilised to
the platform. The crane normally used for pump removal, a water supply (15
litres/minute) and an air supply (7 bar @ 4m3/minute) are the only
onsite requirements for liner installation. Two Oil States
MCS employees are needed to carry out the repair with assistance from the
installations personnel.
Short Lead Time
Hydra-Lok tools are available for various caisson sizes
(12" outside diameter and larger), liner fabrication are straightforward,
therefore the lead time for a repair is typically 4 weeks or less.
Custom tools can be designed and built for special applications.
The Swaging Process
Two swaged connections are made,
one above and one below the corrosion damaged zone (see sequence, below).
Each connection is made when water pressure, captured between the Hydra-Lok tool’s
high pressure seals, expands a section of the liner outward against the caisson.
The swaging process, which takes only about 30 minutes, is accurately monitored
and controlled in real time by measuring and plotting pressure against the
volume of water pumped (see graph below).
|
|
|
| The
Liner is secured to the tool using the hydraulic centralising rams and
then lowered to span the corrosion damaged zone. |
Once
the liner is in position, the seals are extended and hydraulic pressure
is applied to the isolated section, forming the upper connection. Seals
and centralisers are then retracted and the tool is moved below the
damaged zone. |
With
centralisers and seals again extended, pressure is applied to form the
lower connection. At this point, axial and bending load are transferred
across the corroded section. |
After
the Hydra-Lok tool is removed, the repair is complete. The pump or
other equipment can be reinstalled at its original location and the
caisson returned to service. |
|
Controlled
Expansion
Oil
States MCS technicians monitor a real-time pressure/volume plot to control
and verify each stage of the swaging process |
|
|
Caisson Repair PowerPoint Presentation
If you would like to
view a PowerPoint presentation of the
Hydra-Lok®
swaging system,
right click on the link to download HL Caissons
now, or request the
file using the form on the Contact Us page.
Click on the link to view the
Caisson Repair Brochure.
Click on the link to view the
a list of Caisson Repair
Operations.
Further Information
For further details, a
consultation or quotation please go to the Contact Us
page where you can E-mail OSMCS Ltd using the online form. If you prefer to
speak to an engineer in person our telephone number is also available on the
contact page.
|
|
OIL STATES MCS LIMITED