Method of Motion Compensation with Synthetic Rope

Inactive Publication Date: 2015-07-09
REEL POWER LICENSING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides a way to lift heavy loads in deep sea without the need for a smaller capacity at deeper depths.

Problems solved by technology

Especially when one package is to be landed on the top of another package, the surge of the vessel on the surface can cause damage to the subsea equipment being landed and the equipment being landed on as they impact one another.
Running heavy subsea packages to depths such as 10,000 feet have the problem that when that much steel cable is deployed, the majority of the cable's strength is consumed in simply holding its own weight as steel cable is relatively heavy.
In either case the wire rope or synthetic rope is flexed once in lowering, but is repeatedly flexed during motion compensation times. This is of little consequence in wire cable, but the sliding friction (internal and on the sheaves) of the synthetic rope will generate high heat, potentially to the point of destroying the synthetic rope due to melting.
The capability to lower subsea packages to the seafloor with a synthetic rope under motion compensation control would allow substantially expanded deep sea lifting and lowering capabilities as contemporary winching methods for synthetic rope has the potential for damaging the critical synthetic rope during motion compensation operations.

Method used

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  • Method of Motion Compensation with Synthetic Rope
  • Method of Motion Compensation with Synthetic Rope
  • Method of Motion Compensation with Synthetic Rope

Examples

Experimental program
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Embodiment Construction

[0016]Referring now to FIG. 1, a pictorial view of a motion compensation system 10 is shown being landed on a boat 12 having a storage area 14 for storing a length of synthetic rope 16. The synthetic rope 16 can also be stored on a reel if desired. The synthetic rope 16 is shown coming out of the storage bin at 18, going over a sheave 20 which is supported in a mast 22, continues downwardly at 24 and 26, and connects to subsea package 28 at connection 30.

[0017]An upper winch 40 is provided with a wire rope 42 going over sheave 44, with the wire rope continuing downwardly at 46 and connects to gripper 48 at connection 50.

[0018]A lower winch 60 is provided with a wire rope 62 going over sheave 64, with the wire rope continuing downwardly at 66 and connects to gripper 68 at connection 70.

[0019]As is illustrated, the synthetic rope 16 passes over the sheave 20 with no significant loading, but rather the load of the synthetic rope 16 and the subsea package 28 is carried by either gripper...

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Abstract

A method of providing motion compensation of a subsea package with a synthetic rope comprising attaching the synthetic rope to the subsea package, supporting a first gripper with a wire rope from a winch capable of motion compensation control characteristics and gripping the synthetic rope with the first gripper, supporting a second gripper with a second wire rope, and repeating the following sequence: lowering the first gripper, the synthetic rope, and the subsea package a first distance, gripping the synthetic rope with the second gripper, releasing the first gripper from the synthetic rope, raising the first gripper the first distance, gripping the synthetic rope with the first gripper, releasing the second gripper from the synthetic rope, such that when the subsea package is lowered proximate the subsea landing location the winch capable of operating with motion compensation characteristics can operate to compensate for the vessel motion and smoothly lower the subsea package to the subsea landing location.

Description

TECHNICAL FIELD[0001]This invention relates to the method of providing motion compensation operations for synthetic rope especially as relates to deep water lifting and lowering operations.BACKGROUND OF THE INVENTION[0002]Offshore equipment packages are often placed on the ocean floor by lowering on a cable to the desired location. Especially when one package is to be landed on the top of another package, the surge of the vessel on the surface can cause damage to the subsea equipment being landed and the equipment being landed on as they impact one another. Often times the packages must be landed securely before hydraulic connectors can join them together.[0003]Motion compensation is used to detect the motion of the vessel and pay the supporting line in and pull it back by operating the winch as the vessel heaves so that the package near the seafloor can remain vertically stationary and then slowly be lowered to engagement. The default material for the lifting line is a high strengt...

Claims

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Application Information

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IPC IPC(8): B63B27/16B66C23/53
CPCB63B27/16B63B2734/00B66C23/53B63B27/08B66C13/02B66D1/52F16L1/19
InventorBAUGH, BENTON FREDERICK
OwnerREEL POWER LICENSING