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there are no particular cautionary measures to take other than to
operate the Unit and its equipment within design limits. For Units
with large cantilever reach and high cantilever loads, extra care
must be taken to ensure that the maximum footing reaction does
not exceed a specified percentage of the reaction achieved during
preload.
ELEVATED STORM SURVIVAL CONDITION
When the Unit is performing operations, the weather is to
be monitored. If non-cyclonic storms which exceed design
operating condition environment are predicted, Operations should
be stopped and the Unit placed in Storm Survival mode. In this
mode, Operations are stopped, equipment and stores secured, and
the weather and watertight enclosures closed. If cyclonic storms
are predicted, the same precautions are taken and personnel
evacuated from the Unit.
This is how a jack up rig is bought from the shore to the
required location for drilling.
ELEVATING SYSTEM
All Jack Ups have mechanisms for lifting and lowering the
hull. The most basic type of elevating system is the pin and hole
system (fig. 1.5), which allows for hull positioning only at discrete
leg positions. However, the majority of Jack Ups in use today are
equipped with a Rack and Pinion system for continuous jacking
operations (fig. 1.6). There are two basic jacking systems: Floating
and Fixed. The Floating system uses relatively soft pads to try to
equalize chord loads, whereas the Fixed system allows for unequal
chord loading while holding. There are two types of power sources
for Fixed Jacking Systems, electric and hydraulic.Both systems
have the ability to equalize chord loads within each leg. A
hydraulic-powered jacking system achieves this by maintaining the
same pressure to each elevating unit within a leg. Care must be
taken, however, to ensure that losses due to piping lengths, bends,
etc., are either equalized for all pinions or such differences are
insignificant in magnitude. For an electric powered jacking
system, the speed/load characteristics of the electric induction
motors cause jacking motor speed changes resulting from pinion
loads, such that if jacking for a sufficiently long time, the loads on
any one leg tend to equalize for all chords of that leg.
The legs are restrained in horizontal movement and in
rotation by the leg guides. Leg guides may also maintain the
allowable position of the elevating pinions with respect to the leg

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