What is a Liftboat? |
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A liftboat, not to
be confused with a conventional jackup drilling rig, is defined as a
self-elevating, self-propelled vessel equipped with at least one
crane and with open deck
space that can be
used for multiple purposes. Liftboats are the trucks of the offshore
fleet. They carry any kind of equipment necessary to do whatever the
job requires.
Liftboat jobs
include wireline, crane operations, pipe-laying, diver support
platforms, workover and coiled tubing rigs, temporary housing for
construction and service crews, and so on. The list of uses will be
limited only by the vision of the operators and demands of the
market. Worldwide, the fleet consists of some 235 vessels of various
sizes and capabilities.
Liftboats are
classed by leg length that, with allowances for penetration, air gap
and leg reserve, translates as water-depth capability. Some of the
smaller boats, dating back from the earliest days of the industry,
were designed to operate in water depths of only 1½ feet. At the
other extreme, Global Industries Class 229 boats can work as deep as
180 feet. The Searex Class 260 and Power 250 Class vessels, when
completed, will extend water depth capabilities to over 200 feet.
Crane capacity and
deck loads vary as much as water-depth ratings. For example, the
Cajun II Class 28 wireline boat has a four-ton crane and carries up
to 12.5 tons on deck. The giant Prisa 110 and its sister vessels
accommodate one million pounds of deckload and deploy 175-ton cranes,
mounted concentrically with forward legs to give a full 360º of reach.
For specifications
on liftboats, check the database within
this site.
Most liftboats are
built on barge hulls for maximum deck load. One or two directly
coupled diesel engines provide propulsion. Legs are tubular and
operated by a simple hydraulic system. But this is changing. Some of
the newer vessels employ truss legs and thrusters for enhanced
maneuverability. New, high-speed jacking systems include
instrumentation to monitor the loading on each pinion, jacking speed
and overall system function. Dynamics Marine has a V-hulled boat on
the drawing boards. This vessel will have a 175-ton crane and a 1.5
million pound deckload capacity.
Click here
for links to liftboat operator sites on the web.
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