Jacking Control Systems

Jacking Control Systems are used to control the jacking system. This interface allows the operator to raise and lower the rig’s legs, so it could be positioned at the desired height above the water level.

Control system consists of:

• Human-machine interface (HMI) – a screen that shows system parameters to the operator
• Joystics – allows the operator to control the movement of the pinions / legs.
• Programmable Logic Controllers (PLC) – Tiny computer designed to monitor input and output information from connected devices (sensors, motors, pumps, joysticks). They are a combination of software and hardware and act as the brain of the machine.

This is an (oversimplified) example of control system on a jackup barge with hydraulic jacking system:

The operator givs input to the control system via the joysticks (e.g. leg down). This input signal is then relayed to the PLC, which ensures the system is ready to accept the command. After confirmation, PLC forwards the command to the hydraulic pump.

The pump then gets to work, pumping the hydraulic oil through the pipes to the hydraulic motors. The motors spring into action, turning the gearbox which amplifies the torque and sets the pinions in motion. As a result, the leg moves in the desired direction.

Control systems are different and offer various features, but some of the basic functions are:

• One joystick for each leg, to allow independant operation
• Synchro joystick, to move all legs together
• Leg speed selector, for jacking systems with variable speed motors
• Leg position indicators, for jackups equipped with leg position sensors
• Monitoring of all jacking system parameters (power, pressure, load, etc.)
• Alarm indicators
• Emergency stop