STEVADJUSTER®

LIFETIME MOORING ADJUSTMENT

The STEVADJUSTER^® is an innovative, cost-effective and time-saving solution for chain adjustment, pre-tensioning of moorings and easy connection or disconnection of anchor lines. The entire operation takes place subsea and does not require the use of winches or other heavy equipment on the platform being moored. Therefore, the bollard pull of the vessels involved in the operation does not need to be prohibitively high. Modest installation or maintenance vessels have sufficient capacity to get the job done. The use of this subsea chain adjuster offers significant safety benefits, as the tensioning operation is performed away from the floater.

Simplicity and through-life flexibility

The STEVADJUSTER^® makes it possible to use winchless platforms, which significantly reduces the CAPEX of the floater. The platform side is simplified to a plain connection point such as a padeye, and no power is needed. Typically, fewer modest vessels are required during the hook-up and operation, further reducing cost.

The unit is designed for the lifetime of the project and requires no specific maintenance. The STEVADJUSTER^® can be used for a wide range of different mooring systems and it is particularly efficient when used in a 3-leg mooring system where adjusting a single leg allows tensioning of all three at the same time. Additionally, the chain does not have to be cut, which makes it possible to lengthen the lines at a later date.

The STEVADJUSTER^® stays in place for the entire lifetime, enabling easy re-tensioning or slackening of the system for disconnection and reconnection.

Minimising risks

The system uses the winch capacity from the installation or maintenance vessel. The platform stays lean, and the tensioning process is performed away from the floater, minimising the risks associated with this marine operation.

The anchors are pre-laid and the non-adjustable lines connected to the floater. With the adjustable line connected last under minimal tension, the chain can then be pulled through and locked in the STEVADJUSTER^® at the required tension, and all at a safe distance from the floating asset.

Benefits

Lower CAPEX - no need for expensive winches, cutting materials, or power at platform.
Lower OPEX – fewer modest vessels for operations; minimal maintenance over lifetime.
Safe - mooring length can be adjusted away from the platform; no hot work.
Built to order - any size is possible, to suit any specific chain diameter and project application.
Robust design – proven offshore materials and construction.
Superior fatigue life - long-term use for line connection, disconnection, length adjustments and line pre-tensioning.
Excess chain retained - remains on the seabed to be recovered for future shortening or lengthening.

For
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info

Eirini Papapanagiotou

For
more
info

Peter Foxton

Features & specifications of the STEVADJUSTER®

The STEVADJUSTER^®makes it possible to use winchless platforms, which significantly reduces the CAPEX of the floater. The platform side is simplified to a plain connection point such as a padeye, and no power is needed. Typically, fewer modest vessels are required during the hook-up and operation, further reducing cost.

Working principle

Once the anchor is positioned at the desired location, the anchor line is slackened and laid in the right direction. The STEVADJUSTER^® is connected into this mooring line, either anchor or platform side can be adjustable. At this stage the adjustable chain is locked in the STEVADJUSTER^®.

The assembly is lowered and the active line buoyed off when it reaches the sea floor. The chain is now securely hooked up to the platform.

The active chain is now released by disengaging the cam mechanism using a secondary line (or ROV). Chain is pulled through the unit until reaching the required length and therefore pre-tension. At this point, the cam is re-activated to secure the chain in the STEVADJUSTER^® jaws. The cam provides a secondary locking means to maintain engagement of the chain, and it has a further tertiary security system in the form of a locking pin. The excess chain generated by the adjustment process can be abandoned on the sea bed near the STEVADJUSTER^®, remaining available for future adjustment operations.
Certification

STEVADJUSTER^® is certified by classification societies for permanent long term mooring applications.
Construction

The STEVADJUSTER^® is a steel fabrication (welded construction) using high strength offshore grade steel materials and is purposely made as a very robust device to handle the rough-and-tumble of offshore installation with large diameter chain.
Superior fatigue life

The design is at least as strong as the chain on which it will be operating, both at beginning of life (new) and at end of life (corroded condition), and has superior fatigue life compared to the chain.
Size matched

The STEVADJUSTER^® is designed to suit a specific chain diameter and grade. It is custom-made for the lifetime of the system within which it is to be fitted. The STEVADJUSTER^® is effectively a permanent connector, that also acts as a length adjuster.
Unit weight

The unit weight is adjustable. Weight (ballast) can be added if required to act as a clump weight in the mooring leg. It depends on the seabed as to how large the base (mud mat) needs to be to prevent the unit from sinking too far into the seafloor.
Chain length/material

Chain length is not a dictating parameter. Sufficient length must be available to make the necessary adjustments to satisfy the mooring system’s pretension requirements. However, this is a project-specific consideration. Chain is required as part of the mooring leg on which to operate, but the rest of the line can be chain, steel wire rope or synthetic fibre rope or any combination of these elements.