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and in areas where soils and foundations may be challenging or
even unstable.
There are three main components of a Jack Up Unit: the
Hull, the Legs & Footings, and the Equipment. Each of the
component are described below :-
HULL
The Hull of a Jack Up Unit is a watertight structure that
supports or houses the equipment, systems, and personnel, thus
enabling the Jack Up Unit to perform its tasks. When the Jack Up
Unit is afloat, the hull provides buoyancy and supports the weight
of the legs and footings (spud cans), equipment, and variable load.
Different parameters of the hull affect different modes of operation
of the Unit. In general, the larger the length and breadth of the
hull, the more variable deck load and equipment the Unit will be
able to carry, especially in the Afloat mode (due to increased deck
space and increased buoyancy).
Also, larger hulls generally result in roomier machinery
spaces and more clear space on the main deck to store pipe, 3rd
Party Equipment, and provide for clear work areas. The
larger hull may have larger preload capacity that may permit
increased flexibility in preloading operations. Larger hulls
generally have the negative effects of attracting higher wind, wave
and current loads. Since Jack Ups with larger hulls weigh more,
they will require more elevating jacks of larger capacity to elevate
and hold the Unit.
The large weight also affects the natural period of the Jack
Up Unit in the elevated mode. The draft of the hull, or the distance
from the afloat waterline to the baseline of the hull, has a direct
effect on the amount of variable deck load that can be carried and
the stability when afloat. The draft of the hull has an opposing
relationship with the hull’s freeboard, or the distance from the
afloat waterline to the main deck of the hull. Every incremental
increase in the draft of a Jack Up decreases the freeboard by the
same increment.
LEGS AND FOOTINGS
The legs and footings of a Jack Up are steel structures that
support the hull when the Unit is in the Elevated mode and provide
stability to resist lateral loads. Footings are needed to increase the
soil bearing area thereby reducing required soil strength. The legs
and footings have certain characteristics which affect how the Unit
reacts in the Elevated and Afloat Modes, while going on location

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