| 摘要 |
System and method for replacing an insert unit included in an assembly located at a remote distance below a location from where the assembly can be serviced and controlled by manpower, for example an insert valve assembly (22) belonging to a subsea production system for oil and gas. In carrying out the method with said system at a subsea production site, a manipulator (1) is brought by means of a sheave (2), a hoisting cable (3), and guide wires (4, 5) down to a predetermined location on the bottom of the sea. The manipulator comprises a telescopic arm (15, 16) which is then moved towards and fixed by means of a hook (20) and a lug (21) to a valve tree (17) which supports a valve (22), the insert unit 26, of which is to be unscrewed from the respective valve housing and be replaced. A carriage (18) located in the manipulator and comprising retrac tion, aligning and fixing devices (32, 33, 34) is brought with the aid of the telescopic arm and a rail (19), located on the top side of the carriage, towards the valve tree and is fixed to retraction cones (35, 36, 37) mounted on the valve tree. This allows a moment producing tool (31), mounted in the carriage, to grapple a castellated nut (24) which fixes the insert unit to the valve housing of the valve. Thereafter, a releasing moment is applied on the castellated nut, whereby the castellated nut with the insert unit is unscrewed from the valve housing and the valve tree. The carriage with the insert unit is separated from the valve tree and is brought back via the telescopic arm to the manipulator. The insert unit of the valve is replaced by a new insert unit, either by a new insert unit stored in the manipulator and with the aid of gripping arms present in the manipulator, or by raising the manipulator to the surface where the replacement is carried out, whereafter the manipulator is again lowered and the carriage is again moved towards and fixed to the valve tree. This also allows the moment producing tool to move the new insert unit with its castellated nut towards the valve housing, whereupon a tightening moment can be applied. |
