In-line mooring connector and tensioner
A mooring system for offshore vessels uses a chain stopper within a preset mooring line. The chain stopper has means for attaching a removable hydraulic chain jack actuator which may be used to stroke the chain through the stopper assembly while both the stopper and the mooring line remain under load.
1. An in-line mooring chain tensioner comprising:
a chassis having a first, upper end and an opposing, second, lower end;
a connector on the second end of the chassis configured to engage an anchor line;
a first opening in the first end of the chassis sized and configured to permit the passage of a mooring chain;
a second opening in the chassis proximate the second end; and,
a chain jack removably mounted within the chassis.
2. The in-line mooring chain tensioner recited in claim 1 wherein the second opening in the chassis is configured to direct a mooring chain exiting the chassis in a generally downward direction, off-axis the chassis.
3. The in-line mooring chain tensioner recited in claim 1 further comprising:
a first chain stopper within the chassis moveable from a first position that engages a mooring chain passing from the first opening through the second opening to a second position that permits movement of the chain through the chassis.
4. The in-line mooring chain tensioner recited in claim 1 wherein the chain jack comprises:
a base plate having a central opening;
at least one hydraulic cylinder attached to the base plate and a hydraulic actuator extending from the cylinder; and,
a moveable plate having a central opening said plate connected to the hydraulic actuator and parallel to the base plate.
5. The in-line mooring chain tensioner recited in claim 4 further comprising:
a second chain stopper mounted on the moveable plate and moveable from a first position that engages a mooring chain passing through the central opening to a second position that permits movement of the chain through the central opening.
6. The in-line mooring chain tensioner recited in claim 1 wherein the chassis is open on at least one side so as to permit removal of the chain jack.
7. The in-line mooring chain tensioner recited in claim 5 wherein the first and second chain stoppers are hydraulically actuated.
8. The in-line mooring chain tensioner recited in claim 7 wherein the first and second chain stoppers are configured for hydraulic actuation by a subsea remotely operated vehicle.
9. The in-line mooring chain tensioner recited in claim 5 wherein the first and second chain stoppers are configured for hydraulic actuation via an umbilical line from a surface vessel.
10. The in-line mooring chain tensioner recited in claim 4 wherein the hydraulic cylinder of the chain tensioner is configured for hydraulic actuation by a subsea, remotely operated vehicle.
11. The in-line mooring chain tensioner recited in claim 4 wherein the hydraulic cylinder of the chain tensioner is configured for hydraulic actuation via an umbilical line from a surface vessel.
12. The in-line mooring chain tensioner recited in claim 1 further comprising a chain cruciform proximate the first opening in the first end of the chassis.
13. The in-line mooring chain tensioner recited in claim 1 further comprising a chain cruciform proximate the second opening in the chassis.
14. The in-line mooring chain tensioner recited in claim 1 further comprising a sensor responsive to the tension load on the chassis.
15. The in-line mooring chain tensioner recited in claim 4 further comprising a sensor responsive to the position of the hydraulic actuator.
16. The in-line mooring chain tensioner recited in claim 5 further comprising a first sensor responsive to the position of the first chain stopper and a second sensor responsive to the position of the second chain stopper.
17. The in-line mooring chain tensioner recited in claim 3 further comprising a housing within the chassis surrounding the first chain stopper on at least two sides.
18. The in-line mooring chain tensioner recited in claim 4 wherein the base plate of the removable chain jack bears against the housing when the chain jack moves a chain passing through the in-line chain tensioner.
19. The in-line mooring chain tensioner recited in claim 4 further comprising a gate configured to close the central opening in the base plate around a chain passing through the chain tensioner.
20. The in-line mooring chain tensioner recited in claim 4 further comprising a gate configured to close the opening in the moveable plate around a chain passing through the chain tensioner.
21. A method for tensioning a subsea anchor line comprising:
providing a mooring connector in an anchor line between a first lower portion and a second upper portion comprised of chain, said mooring connecter configured to receive a removable chain jack; and,
attaching a removable chain jack to the mooring connector using a remotely operated vehicle (ROV) controlled by a first umbilical from a surface vessel.
22. The method recited in claim 21 wherein attaching a removable chain jack to the mooring connector is performed while the anchor line is under tension.
23. The method recited in claim 21 further comprising:
moving the upper portion of the anchor line relative to the lower portion of the anchor line and the mooring connector by actuating the chain jack via a second umbilical from the surface vessel.
24. The method recited in claim 23 wherein power to the chain jack is provided via the second umbilical.
25. The method recited in claim 23 further comprising:
locking the upper portion of the anchor line to the mooring connector.
26. The method recited in claim 25 further comprising:
detaching the removable chain jack from the mooring connector using the remotely operated vehicle (ROV) controlled by the first umbilical; and,
recovering the removable chain jack at the surface vessel.