• N-Line Tensioner

    The N-line riser tension system compensates for the heave, pitch, and roll of the vessel by using cylinders to apply a vertical force to the top of the marine drilling riser. This provides stability to the riser and controls its stresses, displacements, and angles. Located on the drilling vessel near the periphery of the drill floor, tensioners provide tension to the riser while the floating drilling vessel moves in response to the wind, waves, and current.

    Description

    The N-line tensioner systems consist of multiple cylinders that are suspended from the drill floor substructure and connected to the tension ring by shackles or ball joints. The cylinders may be arranged in configurations to fit the specific layout of the substructure and the layout of pipe/BOP running equipment. The cylinders may be suspended in a trip save, which allows quick, sideways removal of the riser string from the wellcenter or riser operation on both wellcenters on a dual derrick rig. The tensioner systems limit tensioner rod speed in the event of a sudden loss of load in hydraulic flow shut-off, such as a parted wire rope or parted tensioner shackle. An anti-recoil control system limits riser and tensioner speeds during emergency disconnect.