The controlling of motion, forces and masses is the specialty of Bosch Rexroth. On shore, on the surface of the sea and at depths of two thousand meters. There are a multitude of impressive examples: Electric ship lifts, wave generators, heavy lift installations, active swell compensation for the most varied applications. This is now supplemented with the order for the drive units and controls of the skidding and fixation systems of the four platforms that have been developed by the Dutch engineering firm GustoMSC at the order of the Danish offshore contractor Maersk.
Increase the working range
The offshore industry is developing apace. A question that occupied the minds of the engineers at GustoMSC was 'How can we increase the working range of derricks on offshore platforms and simultaneously optimize the drilling installation?' In the second half of the nineteen nineties they developed the X-Y cantilever, which has a multitude of advantages in comparison with conventional designs. The engineering firm invited Rexroth to the consultations at an early stage in order to provide answers on questions relating to drive units and control. This resulted in deliveries for this type of skidding systems, which have since proven themselves on jackups that were built previously: the Maersk Innovator (2002) and the Maersk Inspirer (2004). Both drilling rigs were built in the Hyundai Heavy Industries shipyard in South Korea.
Stringent demands and standards
There is now an order for four new rigs that are being constructed by a shipyard in Singapore according to the GustoMSC CJ50-X100-MC design.
Over the three years, Rexroth will be supplying four drive units for the rigs, including the controls for these skidding installations - the first in September 2006, the last in February 2008.
Each system includes the supply of sixteen hydraulic skidding cylinders, sixteen pin control cylinders and a hydraulic generator.
The skidding cylinders have a diameter of 400 millimeters, a travel of 755 millimeters and deliver a compressive force of 300 tons. The total installed capacity of the hydraulics is 320 kW. The installation produces a maximum working pressure of 335 bar.
A control system is also part of the delivery. This includes a central control console, a Motor Control Console and a Power Unit Control Console with PLC and the required software. Vital components are installed with redundant backups in order to guarantee optimum operating reliability and safety. Both the generator and the control units were built into a specially designed container in order to meet the stringent noise regulations for the offshore sector. A precondition that sorely tested the creativity of the engineers, as did the requirements in the field of ergonomics, ease of operation, maintenance-friendliness, accessibility and safety.
Besides skidding, Rexroth also performs another function: fixation. Fixation systems anchor the rigs at the desired height and position. The fixation system presses a blockage into the gear rack as soon as the rigs have reached the desired height. The drive with adjustable frequency accurately controls the electric motors. Varying the electrical frequency makes continuously variable and completely controlled force and speed build-up possible. With the following result: Optimum control at a low level of usability and less wear.
For each rig Rexroth supplies seventy two motors with brakes, three motor control centers and three consoles for local controls. Here again, the most stringent safety requirements have been met - the motors function flawlessly under water. The fixation systems will be delivered between April 2006 and September 2007.
At that time, Rexroth will be able to add another significant reference to its track record of prestigious projects.
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