Method for assembling tendons
A tendon is assembled in a horizontal orientation using connectors or by welding at a weld station on a barge or other vessel located at or near the installation site of a tension leg platform. During assembly, the tendon is pulled away from the assembly vessel and tensioned by a tug or offshore work vessel. When fully assembled, the tendon may be up-ended in a manner similar to a wet-towed tendon, and then either pre-installed using floats or passed over to a TLP which is on-site and ready to receive tendons.
1. A method for assembling a tendon for a tension leg platform comprising:
joining tendon segments together in a horizontal orientation on a first floating vessel to produce a tendon assembly;
floating a first portion of the tendon assembly horizontally on the surface of the sea; and,
simultaneously applying a sufficient tension load to the tendon assembly with a second vessel connected to the first portion of the tendon assembly at a point that is remote from the first vessel such that the tendon assembly lies in a substantially straight line between the first vessel and the second vessel.
2. The method as recited in claim 1 wherein the first end of the tendon assembly is floating in the sea.
3. The method as recited in claim 2 wherein the first end of the tendon assembly has one or more floatation devices attached thereto.
4. The method as recited in claim 1 wherein the tension load is applied to the first portion of the tendon assembly using a winch mounted on the second vessel and a winch cable attached to the first end of the tendon assembly.
5. The method as recited in claim 4 wherein the winch is a constant-tension winch.
6. The method as recited in claim 1 wherein the first vessel comprises a stinger configured to progressively lower the tendon assembly from the deck of the first vessel to the water surface.
7. The method as recited in claim 1 wherein the first vessel comprises a plurality of deck-mounted tendon segment supports.
8. The method as recited in claim 1 wherein the first vessel comprises a tendon segment welding station.
9. The method as recited in claim 8 wherein the first vessel comprises a plurality of deck-mounted tendon segment supports aligned with the tendon segment welding station.
10. The method as recited in claim 1 wherein the first vessel comprises means for securing the tendon assembly to the first vessel to accommodate a tensile load applied to the tendon assembly.
11. The method as recited in claim 1 wherein the first vessel comprises a clamping station on the first vessel configured for installing a clamp on a tendon connector.
12. The method as recited in claim 1 wherein the first vessel comprises a weld inspection station.
13. A method for installing a tendon for a tension leg platform comprising:
joining tendon segments together in a horizontal orientation on a first floating vessel to produce a tendon assembly;
floating a first portion of the tendon assembly horizontally on the surface of the sea;
simultaneously applying a sufficient tension load to the tendon assembly during assembly with a second vessel connected to the first portion of the tendon assembly at a point that is remote from the first vessel such that the tendon assembly lies in a substantially straight line between the first vessel and the second vessel;
upending the completed tendon assembly in the sea such that the tendon is substantially vertical; and,
lowering the tendon into a bottom tendon connector pre-installed on the seafloor.
14. A method for installing a tendon for a tension leg platform comprising:
joining tendon segments together in a horizontal orientation on a first floating vessel to produce a tendon assembly;
floating a first portion of the tendon assembly horizontally on the surface of the sea;
simultaneously applying a sufficient tension load to the tendon assembly during assembly with a second vessel connected to the first portion of the tendon assembly that is remote from the first vessel such that the tendon assembly lies in a substantially straight line between the first vessel and the second vessel;
upending the completed tendon assembly in the sea such that the tendon is substantially vertical; and,
passing the upended tendon to a tension leg platform.