The Jacking System and Simulator for Mating the Hutton TLP

ABSTRACT The Hutton TLP Deck/ Hull mating and weldout operation required the use of a sophisticated and unique hydraulic jacking system. The system was designed to accommodate the relative vertical and horizontal motions and the dynamic forces between the Deck and Hull during mating. Obtaining the correct load distribution between each of the 96 jack locations during mating and weldout was a fundamental requirement on which the Deck and Hull structural designs were based and represented an operation beyond the current level of experience. To train the Jacking System operators, a Simulator was custom-built. The simulator modeled the interaction of the ballast systems, the Deck and Hull structures, the impact dampers and the Jacking System. Procedures were developed using this facility prior to its use for hands-on training of the Jacking Teams and full mating operation rehearsals with the Ballast Supervisors. The installation, setting-to-work and commissioning of the Jacking System is described. The paper concludes with the mating and weld out operation at the offshore site. INTRODUCTION The Tension Leg Platform for the Hutton Field was designed for separate fabrication of the Deck and Hull and their subsequent mating at an offshore site. To ensure correct load distribution during the mating and permanent connection of the two structures, special equipment would be required, the most important being the Jacking System (reference 1). The operation of the Jacking System, in concert with the impact dampers and the Hull and Barge ballast systems, would require comprehensive training and rehearsal. A Simulator was considered the most effective means of achieving this. The major phases of the work are described in the following sequence:PHASE I - The Jacking SystemPHASE II - The SimulatorPHASE III - Engineering Review and Procedure DevelopmentPHASE IV - TrainingPHASE V - Installation, Setting-to-Work, Commissioning and Final CheckoutPHASE VI - Operation PHASE I - THE JACKING SYSTEM The Jacking System contract was awarded in November 81. Delivery was made 10 months later in September 82. SPECIFICATION Deck and Hull Structural Design The TLP Deck is supported at four locations on each of the six Hull columns (ref. Figure 1). This configuration results in a light design, while providing a joint with adequate shear and bending moment strength. For each joint, target were calculated, which for the full Deck weight distribution would produce the lowest stress levels overall. The TLP structural design assumed that these target loads would be achievable to within ±10% at mating and during weldout. During load transfer, the tolerances would be wider. (reference 2.) The change of relative vertical deflection between the Deck and Hull at the jack locations during load transfer could be as much as 70 mm. The relative horizontal movements between Deck and Hull during load transfer could be as much as 102 mm.