Underwater Crane
The study of
marine environment, specifically the deep sea requires precise placement of
considerably large and delicate instruments, for instance hydrophone or
pressure pickup array on the sea bed in a particular geometric pattern. Such
operations usually involve the usage of a surface craft which is equipped with
a crane, working in conjunction with divers facilitating the operations on the
sea bottom. Challenges such as high current condition or high sea state pose
serious problems to such operations, specifically when it involves the
shackling or hook-and-release of the payload. The hooks must also be bright
colour or fluorescent so that the operator can identify the component to be
shackled correctly under the poor artificial lighting condition underwater.
Another problem arises from the
usage of hook is the need to into consideration of external effects such as
wind and choppy waters besides the crane’s movement in order to maintain the
correct alignment. To maintain an upright alignment all the time during lifting
operations requires sophisticated tools, for instance Cargotec uses the ARC
tool which consists of an electrically driven power swivel fitted with a
frequency control system coupling with a motion reference sensor. The utilization
of ARC tool is claimed to cut down handling times up to 30% during operations
while undoubtedly shoot up the capital cost.
Figure 1: Underwater crane with a
rubber flotation bladder in a protective clothing, controlled bleed-off valve
and compressed-air supply.
References:
Application Inspired by Suction Mouth of Plescostomus.
By drawing inspiration from the operating mechanism of
the suction disc of a Cling fish, a flexible suction cup is conceived and
designed, which is superior to conventional suction cup in its ability to
maintain the suction, even at wet and slimy surfaces. Besides, the suction cup performs
well in different types of surface, be it uniform or uneven. The bio-inspired
suction cup come forth as a prospective replacement for the shackle or hook of underwater
crane. The ability to maintain suction force on a wet surface in the presence
of considerably high current ensures a tight grip on the underwater load. By
identifying several spots as the lifting points of the load prior to the
lifting operations, the load located underwater can thus be lifted steadily
with ease, rule out the need of cutting-edge motion-sensor tools.
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