WELCOME SEA INSTALLER - A2SEA

JACKING SYSTEM
The four legs help giving SEA INSTALLER her characteristic appearance.
When SEA INSTALLER is in the harbour, her legs are completely retracted,
and when the vessel reaches its destination, the legs are lowered so they
rest on the seabed. All this is controlled from the bridge.
Raising or lowering the legs is called jacking up, which comes from the word
jack. SEA INSTALLER thus operates by raising or lowering the four legs using
a large number of jacks. During operation, the entire vessel is jacked up
to the desired height with the deck typically around 15–25 metres above the
surface of the sea. Once the task has been completed, the vessel is jacked
down so it can sail normally.
An effective jacking system is essential to enable a vessel like SEA INSTALLER
to operate and function effectively. SEA INSTALLER cannot sail during jacking
and to avoid wasting too much time waiting, it is important to be able to
raise and lower the legs as quickly as possible.
• SEA INSTALLER has six
3020 kilowatt engines
• SEA INSTALLER has
three Voight Schneider
propellers for propulsion
and three Bov propellers
for satellite-based
positioning
• The vessel can
manoeuvre with a precision
of 25 cm under optimum
weather conditions.
The jacking system can raise a fully loaded SEA INSTALLER at a speed of
approximately 1 metre per minute, which is twice as fast as standard jacking
systems in the wind turbine industry.
A single day is normally set aside for each offshore wind turbine, so
it is important that the jacking system functions effectively and impeccably.
SEA INSTALLER is fully functional even with two jacking cylinders
out of operation at each leg, and, as with other constructions on
SEA INSTALLER, much has been done to ensure optimum safety and
durability.
To make sure the legs rest firmly on the seabed, each leg has a so-called
spudcan – like the sole of a shoe. The spudcan on the legs measures 108
square metres per leg, so SEA INSTALLER has a solid 432 square metres
footprint once the legs have been lowered.
A special jetting system at the bottom of the legs can flush the legs free of the
seabed when they have to be raised. Depending on the soil conditions, the
legs may have penetrated up to 21 metres into the seabed, and without a jetting
system, lifting the legs would be like pulling a gum boot out of a mud hole.
• The jacking system on SEA INSTALLER is a double hydraulic
system
• There are eight jacking cylinders at each leg, i.e. 32 in total
• The legs on SEA INSTALLER can be raised and lowered at a
speed of 1 m/min
• The legs on SEA INSTALLER are 84 metres long
• The spudcan on the legs measures 108 square metres per leg, i.e.
432 square metres in total.
ENGINE ROOM
No vessel is without an engine room. A huge amount of raw power is
required on board SEA INSTALLER, so the engine room consists of three
separate rooms, each equipped with two 3020 kilowatt diesel-electric engines.
This gives a total of six engines with a combined capacity of more than
18,000 kilowatt, generating high voltage power to propel the vessel, and
for the jack-up system, the cranes and the many cooling, heating and
ventilation systems on board. This is equivalent to the power required for
2,5 million low energy light bulbs – if one should need that.
Like the rest of SEA INSTALLER, the engine room is designed to optimise
vessel operation. Even with two of the six engines out of operation, the
vessel remains fully operational. In a worst case scenario, the vessel can
sail with only one engine.
The result is a large amount of raw power, not to mention a high degree
of reliability of supply, which is essential when A2SEA counts on installing
at least one wind turbine per day. While vessels in the oil and gas industry
typically sail to a specific position, where they are jacked up and remain
for shorter or longer periods of time, wind turbine installation vessels are
constantly on the move, either to transport the turbines to their destination
or in connection with installation.
In addition to the engine power required to sail SEA INSTALLER, the engine
room supplies power to a special satellite-based navigation system
also called DP (Dynamic Positioning), which can maintain a given position
during operation with a tolerance of only 25 cm.