Patent Number: 
Section: claims

1. An apparatus for putting risers under tension, characterized in that it comprises vertical guides ( 7 ) in a derrick; toothed racks ( 4 ) in the vertical guides ( 7 );  a gripper means ( 5 ,  12 ) designed for selectable interaction with a riser, connected ( 6 ) to the racks ( 4 ), and drive units ( 9 ) arranged in the derrick for drive-actuation of the racks ( 4 ) in the vertical guides ( 7 ), the gripper means maintaining the riser under tension when the gripper means interacts with the riser. 2. An apparatus according to  claim 1 , characterised in that the gripper means includes a platform ( 5 ) having gripper members ( 12 ) for interaction with the riser. claim 1 3. An apparatus for putting risers under tension, characterized in that it comprises vertical guides ( 7 ) in a derrick; toothed racks ( 4 ) in the vertical guides ( 7 );  a gripper means ( 5 ,  12 ) designed for interaction with a riser, connected ( 6 ) to the racks ( 4 ), and drive units ( 9 ) arranged in the derrick for drive-actuation of the racks ( 4 ) in the vertical guides ( 7 );  wherein the gripper means includes a platform ( 5 ) having gripper members ( 12 ) for interaction with the riser;  the gripper members being in the form of flaps ( 12 ) supported in the platform so as to be capable of being swung towards one another, each flap having a recess ( 26 ) adapted to the half circumference of the riser. 4. An apparatus according to  claim 1 , characterized in that the drive units ( 9 ) include hydraulic drive motors. claim 1 5. An apparatus according to  claim 2 , characterized in that a rig floor ( 13 ) is capable of being connected to the racks ( 4 ). claim 2 6. An apparatus according to  claim 1 , characterized in that the rig floor is connected to the toothed racks ( 4 ) by means of hydraulically actuated keys ( 14 ). claim 1 7. An apparatus according to  claim 6 , characterised in that the rig floor ( 13 ) is connected to the hydraulically actuated keys ( 14 ) by means of hydraulic working cylinders ( 15 ) so that the drilling floor can be height-adjusted relative to the keys. claim 6 8. An apparatus for putting risers under tension, comprising: vertical guides in a derrick;  toothed racks in the vertical guides;  a gripper connected to the racks and adapted to selectably interact with a riser, the gripper maintaining the riser under tension when selectably interacting with the riser and for not maintaining the riser under tension when not selectably interacting with the riser; and  drive units arranged in the derrick for drive-actuation of the racks in the vertical guides. 9. The apparatus according to  claim 8 , wherein the gripper includes a plurality of flaps adapted to swing toward each other. claim 8 10. The apparatus according to  claim 9 , wherein each of the flaps includes a recess adapted to a half circumference of the riser. claim 9 11. The apparatus according to  claim 8 , wherein the gripper includes first and second flaps, each of the flaps adapted to move between horizontal and vertical positions, the gripper maintaining the riser under tension when each of the first and second flaps is in the horizontal position. claim 8