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In a slot-type jack-up, the platform has a slot through the
floor of the hull. A drilling derrick is positioned over it during
operations. When the platform moves to another location, the
derrick is lifted above it.
 Drilling Systems
Drilling system is the heart of the jack up rig. Drilling is
carried out at the drill floor which is at certain elevation from the
main deck. There is a mouse hole and rat hole in which the drill
stems are assembled. Once the stem is assembled it is placed
concentric with the rotary table which is either driven from the top
or from the bottom. Kelly bushing is provided to support the drill
stem and prevent it from buckling.
The top drive (fig. 1.10) rotates the drill string end bit
without the use of a kelly and rotary table. The top drive is
operated from a control console on the rig floor.

Figure 1.10 -- Top Drive
 Mud Systems
These are of two types – high pressure mud system and low
pressure mud system.
Mud is a mixture of raw water, clay, bainite and some
other minerals. Working of the jack up rig depends upon the power
of the mud system. It is a cyclic procedure which is used to convey
the crushes from the bottom of drill bits to the top of mud tanks
(fig. 1.11). This is called high pressure mud system. when we

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