| 摘要 |
A heave compensation and tensioning apparatus for use on a floating vessel during "locked-to-bottom" operations is provided. Said apparatus includes a frame having an upper section adapted for attachment to an top drive system and a lower section adapted to interface with a flowhead assembly, and a pair of hydraulic cylinders that are fixed to the lower section of the frame. Respective free ends of the piston rods of the hydraulic cylinders are operatively associated with the upper section of the frame. The apparatus is also provided with a pair of accumulators which are in communication with pressure vessels and the cylinders by means of a pneumatic fluid line and a primary hydraulic fluid line, respectively. A control valve assembly is arranged to control fluid flow through the primary hydraulic fluid line, allowing the piston rods to retract or extend in response to, and to compensate for, heave of the floating vessel. An isolation valve is operatively disposed on the primary hydraulic fluid line to hydraulically lock the piston rods. In this way, the heave compensation and tensioning apparatus forms a rigid link and can be employed as a secondary or back-up heave compensator for a primary heave compensator. In the event of failure of the primary heave compensator, the apparatus may be automatically rapidly activated to provide ongoing heave compensation for the floating vessel during locked-to-bottom operations. Automatic activation may be achieved via control valves on bypass lines, bypassing the primary isolation valve. Each bypass line is configured to bypass the isolation valve, whereby the control valve assembly is configured to redirect fluid flow through the first bypass line when pressure in the cylinder(s) exceeds an upper pressure threshold and through the second bypass line when pressure in the cylinder(s) falls below a lower pressure threshold, thereby allowing the apparatus to automatically activate and continue to compensate for heave of the floating vessel. |
