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Key factors for offshore jack-up systems include safety, system availability, speed of relocations, wear reduction, and automation. Rack and pinion systems are the preferred solution for units with truss legs.
Based on GustoMSC’s years of experience and a patented variable Speed Drive (VSD) version of the Rack and Pinion Jacking System was introduced in 2006. With over 70 units in service, the system has proven itself in different markets including the wind turbine installation market where daily relocations are the norm.
The GustoMSC electric VSD driven rack and pinion systems offer the following characteristics:
- Steeples speed control from 0-100%
- High leg handling speed
- Easy automatic re-torqueing
- Control from central- and local control consoles
- Automatic platform leveling during lifting and lowering
- Failsafe brakes with sensorless on/off/wear indication
- Leg position indication and rack phase difference (RPD)
- Load measuring
- through the VSD drives
- optionally in shock pads (floating units)
- Easy maintenance
- Use of standard, offshore type electric motors, without special high-slip requirements
- Easy removal of a drive unit
- Optional remote access of the control system via secured internet connection
High speed low wear and tear
Safe, smooth, and quick relocations depend on the leg jacking speed, effective automation, and high system availability. The unique selling point of the GustoMSC rack & pinion system is based on the patented VSD system. By ensuring that the torque is equally shared by all motors and pinions on the entire platform, the operation is smoother with less stress and less wear & tear. The optimized hardening process for the pinions and high-quality gearboxes further add to a long, reliable life.
The electric motors of the rack and pinion systems are driven by Siemens individual variable speed drives. This arrangement allows for step-less speed control between zero and maximum speed. The GustoMSC Rack & Pinion system offers jacking speed up to 0.8 m/min and leg handling speed up to 1.2 m/min, therefore the jacking operation is no longer the decisive factor during a rig move. Re-torqueing can be performed automatically by the VSD control.
The VSD controlled jacking units are grouped in layers that offer redundancy and thus increase safety. The continuously variable speed drive also means that the power demand can be lowered should the rig power supply be limited. Careful design and fault-tree analysis results in a 99.9% availability of the drives and control system during its operational life. The highly automated control system provides the jacking operator with full information on the central control panel about the motor temperatures, loads, and status of numerous system parameters.
The loads on the legs and pinions during jacking can be accurately monitored by measuring the motor currents. To supplement these dynamic measurements two static load measurement systems were recently introduced enabling operators to monitor the ballast preloading process and heavy loads during severe storms.
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