Methods and Apparatus for Installation of a Device about a Marine Structure

Abstract

Methods and apparatus for the installation of VIV suppression during the S-Lay installation of a subsea pipeline. A locking member will be interposed between a pipe and a fairing rotatably mounted on the pipe, sufficient to bias the fairing against rotating. Upon marine application, the locking member will degrade, thereby releasing the fairing.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This Application claims priority to U.S. Non-Provisional application having Ser. No. 10 / 848,547, filed on May 17, 2004, having attorney docket number TH 2463.FIELD OF THE INVENTION [0002] In one aspect, the invention relates to apparatus, systems and methods for reducing vortex-induced-vibrations (“VIV”), current drag, low frequency drift oscillations due to random waves, and low frequency wind induced resonant oscillations. In another aspect, the invention relates to apparatus, systems and methods comprising enhancement of VIV suppression devices for control of vortex-induced-vibrations, current drag, low frequency drift oscillations due to random waves, and low frequency wind induced resonant oscillations. In another aspect, the invention relates to apparatus, systems and methods comprising modified and improved performance fairings for reducing VIV, current drag, low frequency drift oscillations due to random waves, and low frequency...

AI Technical Summary

Benefits of technology

The invention provides apparatus, systems, and methods for suppressing VIV and reducing drag of marine elements, such as pipes and subsea pipelines. The invention includes a fairing that can be rotatably mounted on the pipe and a locking member that can be positioned between the pipe and fairing to bias the fairing against rotating and position the fairing radially away from the pipe section. The fairing can also be used to modify a pipe by positioning a temporary locking member to bias the fairing against rotating. The invention also includes a collar for securing the fairing to the pipe and a method of passing the pipe with the fairing over a roller. The technical effects of the invention include reducing drag and VIV, improving the stability of subsea pipelines, and improving the installation process of VIV suppression or drag reduction devices.

Problems solved by technology

The vibrations may be largest in the direction transverse to flow, however, in-line vibrations can also cause stresses which may be larger than those in the transverse direction.

If the frequency of this harmonic load is near the resonant frequency of the structure, large vibrations transverse to the current can occur.

These vibrations can, depending on the stiffness and the strength of the structure and / or any welds, lead to unacceptably short fatigue lives.

Stresses caused by high current conditions have been known to cause structures such as risers to break apart and fall to the ocean floor.

For instance, a riser pipe which is vibrating due to vortex shedding may disrupt the flow of water around it more so than a stationary riser.

This results in greater energy transfer from the current to the riser, and hence more drag.

VIV may also be a problem for subsea pipelines, especially the positions of the pipe line that span canyons or trenches on the ocean floor.

Installation of VIV suppression after the laying of the pipeline can be very expensive, laborious, and / or dangerous.

The problem with installing VIV during an S-Lay, is that the stinger may tend to shear off anything that extends radially from the pipe at those places where it engages the pipe.

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