the model tests and do the DP design verification by simulation using DP software. I disagree. I think it is not a question of one or the other.


“One does need model tests to determine the environmental loads a DP system must overcome. However, it is not possible to capture the full physics of the real life DP operations just by the computational tools.”


A better approach is to do a preliminary simulation to determine the best setting for the DP model tests, carry out the DP model tests under fully automatic DP control and then extend the matrix of model test cases by carrying out time domain simulation by using a model optimised from the DP model tests, he says.


DP system onboard the Glomar Challenger in 1968. The first DP drillship for drilling a well, as opposed to coring, was the Sedco (now Transocean) Drillship Sedco 445 (now Deepwater Navigator) in 1971.


Industry-leader Transocean The rest is history! he quips. Now, Transocean leads the industry in high specification deepwater DP drillships.


Gurbachan looks back at the staggering developments that have occurred over the decades, saying that he was extremely proud to have had a chance to work on the design of the Glomar Pacific Class of DP drillships in 1973. “These drillships incorpo- rated the latest station-keeping technology at that time. But compared to the present latest DP technology, I would characterise the Glomar Pacific DP system as analogous to the Ford model-T car!”


Certainly, the list of innovations since the first DP systems were invented is long. But a few developments come to mind, says Gurbachan. Position reference systems, Heading reference systems, Motion Refer- ence Units, Improved sensors and Control systems are just a few. Improved hydrody- namic models of the ship based on model tests, Time domain simulations by using an optimised ship model, Improved thrusters & their drives, Vessel Management Systems & Power Management Systems, are others. Wave feed forward may be the next innova- tion in improving performance of DP control


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systems and is the subject of current research, he adds.


Art of DP Model Testing But one thing that has developed beyond recognition is the art of DP Model Testing, he stresses. “Nobody did these kinds of tests when I first got into the design of offshore drilling units. MARIN pioneered the techniques of DP model tests in order to verify if the DP system design can meet its intended per- formance targets for station-keeping. There are those who believe that one should only determine the environmental forces from


Full DP model tests on a drill ship in the Offshore Basin


“Recently, MARIN has developed a new class of model thrusters that allow a very accurate assessment of the thruster per- formance in model tests such as DP station- keeping, calm water tests and sustained speed tests in waves.”


Commenting on when he first came in contact with MARIN, Gurbachan says that actually a drillship, named after the Global Marine founder Robert F Bauer, was model tested at MARIN back in 1981. The resist- ance and propulsions tests were carried


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