GB2443618A

GB2443618A - Pivotable mooring chain connector assembly

Info

Publication number: GB2443618A
Application number: GB0622370A
Authority: GB
Inventors: Erik Paul Ter Brake
Original assignee: Bluewater Energy Services BV
Current assignee: Bluewater Energy Services BV
Priority date: 2006-11-09
Filing date: 2006-11-09
Publication date: 2008-05-14
Anticipated expiration: 2026-11-09
Also published as: GB2443618B; NO337644B1; GB0622370D0; NO20075554L

Abstract

A mooring chain connector assembly for a floating device comprises a (in a non-loaded situation) substantially vertically extending channel means (1, Fig 1) attached to the floating device for the passage of a mooring chain. The channel means near its upper end is provided with mooring chain locking means (3, Fig 1) and a substantially horizontally extending first pivot axis (2, Fig 1) around which the channel means can pivot relative to the floating device. The assembly further comprises an elongate member 4 which is insertable through the channel means, said elongate member (4) having an upper end shaped for lockingly cooperating with the locking means. The elongate member has a lower end connected to an upper end of a lever arm 7 through a second substantially horizontally extending pivot axis 6 including an angle with the first pivot axis. A lower end of said lever arm is provided with coupling means 8 for coupling the mooring chain 10 to the lever arm. The second pivot axis may extend perpendicularly to said first pivot axis.

Description

Mooring chain connector assembly and elongate member for ap-plication

therein The invention firstly relates to a mooring chain connector assembly for a floating device, such as for exam-ple a vessel or a floating offshore platform.

As is known generally, floating devices such as vessels or floating offshore platform, for example in the oil and gas industry, are moored to the seabed with one or more mooring lines, often mooring chains. The floating de-vice is kept on location because of the catenary effect of the mooring line(s). A shift of the floating device leads to a lifting or lowering of the mooring line(s), which leads to a counter effect striving to re-establish the original posi-tion of the floating device.

When (at least the upper part of) such a mooring line comprises a mooring chain, the floating devices often are provided with a mooring chain connector (or so-called chainstopper) for each mooring chain, comprising a (in a non-loaded situation) substantially vertically extending channel means attached to the floating device for the pas-sage of the mooring chain. The channel means near its upper end is provided with mooring chain locking means and a sub-stantially horizontally extending first pivot axis around which the channel means can pivot relative to the floating device. The mooring chain locking means can be of the type allowing an adjustable position of the mooring chain (for example for tensioning the mooring chain after the initial locking to the channel means). Further, often, the lower end of the channel means is flared.

The first pivot axis helps in accommodating mo-tions of the mooring chain in its catenary plane ("in-plane motions") and thus minimising fatigue related to such mo-tions.

Recently it has been discovered, however, that also motions of the mooring chains in a transverse direction (out-of-p1ane motions") can cause fatigue problems which may lead to a collapse of the mooring chain.

In view of the above it is an object of the pre- sent invention to provide an improved mooring chain connec-tor assembly.

Thus, in accordance with the present invention, a mooring chain connector assembly for a floating device, such as for example a vessel or a floating offshore platform, is provided comprising a (in a non-loaded situation) substan-tially vertically extending channel means attached to the floating device for the passage of a mooring chain, which channel means near its upper end is provided with mooring chain locking means and a substantially horizontally extend-ing first pivot axis around which the channel means can pivot relative to the floating device, the assembly further comprising an elongate member which is insertable through the channel means, said elongate member having an upper end shaped for lockingly cooperating with the locking means, and a lower end connected to an upper end of a lever arm through a second substantially horizontally extending pivot axis in-cluding an angle with the first pivot axis, wherein a lower end of said lever arm is provided with coupling means for coupling the mooring chain to the lever arm.

The second pivot axis provided by the interface between the elongate member and lever arm allows transverse motions ("out-of-plane motions") of the mooring chain with-out the creation of undesired fatigue effects. The elongate member can be used as an aftermarket part for upgrading an already existing mooring chain connector from having one pivot axis to having two pivot axes. No extensive (dis)assembling is required.

Preferably the second pivot axis extends perpen- dicularly to said first pivot axis. This offers the most ef-fective configuration of the assembly. It is noted, that small deviations from such a situation are intended to sub-stantially correspond with the indication "perpendicularly".

In a special embodiment of the mooring chain con-nector assembly according to the present invention the lever arm is provided with a third pivot axis extending substan-tially in parallel to the first pivot axis. This makes it even easier for the mooring chain to move in all directions without any adverse effects. The location of such third pivot axis may be anywhere (above, near to or below the sec-ond pivot axis).

When at least the upper end of the elongate member is shaped in correspondence with the shape of the mooring chain (for example comprising at least one chain shackle), it can easily cooperate with the original mooring chain locking means provided at the upper end of the channel means.

For a good operation, and for minimising any wear, it may be desirable that the elongate member assumes a sta-ble position within the channel means, such that no relative movements therebetween occur. For example, this can be real- ised when the elongate member at least locally has a cross-section closely matching the internal cross-section of the channel means. As a result an interference fit may be ob-tained.

It is noted that the cross-section of the channel means may have different shapes, and does not need to be circular. For example, said cross-section may have a square shape with rounded corners, in correspondence with the shape of a shackled chain when seen in a frontal view.

To achieve the above, in a preferred embodiment the elongate member at least at one lengthwise position has a shape for clampingly engaging the channel means. Said lengthwise position may be in its lower part, near the sec-ond pivot axis.

For the connection of the mooring chain to the lever arm many possibilities exist. For example the coupling means at the lower end of the lever arm may comprise a pin insertable through a shackle of the mooring chain. However, when it is desirable that the mooring chain position rela- tive to the lever arm is adjustable after the initial cou-pling has occurred, it is preferred that the coupling means at the lower end of the lever arm are of the type allowing an adjustable coupling with the mooring chain. Such coupling means may resemble the mooring chain locking means provided at the upper end of the channel means.

The invention secondly relates to an elongate mem-ber for application in a mooring chain connector assembly in accordance with the present invention.

Hereinafter the invention will be elucidated while referring to the drawing, in which: Figure 1 shows, partly in a longitudinal section and partly in a side elevational view, part of an embodiment of the assembly according to the present invention; Figure 2 shows in a side elevational view the elongate member of the assembly illustrated in figure 1; Figure 3 shows another side elevational view, or-thogonally to figure 2, and Figure 4 shows a cross-section according to IV-IV in figure 2.

Firstly referring to figure 1, a mooring chain connector assembly for a floating device, such as for exam-ple a vessel or a floating offshore platform is illustrated.

It comprises a (in a non-loaded situation) substantially vertically extending channel means or tube 1 with a flared lower end and with an upper end provided with means for de- fining a first pivot axis 2 through which the tube 1 is at-tached to the floating device (not illustrated) The tube 1 originally is shaped for the passage of a mooring chain (not illustrated in figure 1, but partly shown in figures 2 and 3) and at its upper end is provided with mooring chain locking means 3. For example said locking means 3 comprise locking levers cooperating with chain shackles and biased to the illustrated position which, against the bias, may pivot upwardly such as to allow an up-ward shift of the mooring chain (but preventing a reverse downward shift).

The first pivot axis 2 extends substantially hori-zontally, such that the tube 1 can pivot relative to the floating device in a substantially vertically extending plane to accommodate in-plane motions of the mooring chain.

The assembly further comprises an elongate member 4 which is insertable through the tube 1. Said elongate mem-ber 4 has an upper end shaped for lockirigly cooperating with the locking means 3. For example, the upper end of the elon-gate member 4 is provided with shackle-like parts 5.

The lower end of the elongate member 4 defines a second pivot axis 6 for connection to an upper end of a lever arm 7 (illustrated in figures 2 and 3 only). The sec-ond pivot axis 6 extends substantially horizontally and per-.

pendicularly to the first pivot axis 2 and will accommodate motions of the mooring chain out-of--plane.

A lower end of said lever arm 7 is provided with coupling means 8 (illustrated here as a pin 9) for coupling a mooring chain 10 (only an upper shackle of which has been illustrated) to the lever arm 7.

It has not been illustrated that the lever arm 7 can be provided with a third pivot axis extending substan-tially in parallel to the first pivot axis 2, for example at a location between the second pivot axis 6 and the coupling means 8 (such that the lever arm 7 itself will be a two-part linkage).

The elongate member 4 at least locally has a cross-section closely matching the internal cross-section of the tube or channel means 1. This has been indicated by a collar 11 which is provided at at least one lengthwise posi-tion and which has a shape for clampingly engaging the inner wall of the tube or channel means]..

The coupling means 8 at the lower end of the lever arm 7 also could be devised in a manner to allow an adjust-able coupling with the mooring chain 10, and thus could be constructed similar to the locking means 3.

The length of the lever arm 7 must be sufficient to enable a moment overcoming the friction at the pivot axis 6, which friction will be substantial due to the large di-mensions of a bearing defining the pivot axis 6 and due to the immense weight of the mooring chain 10.

As illustrated in figure 4, the tube 1 has a sub-stantially square cross-section with rounded corners, closely matching the shape of the shackles 5 of the elongate member 4 (or of a mooring chain 10). The body of the elon-gate member 4 preferably will have a corresponding shape.

The invention is not limited to the embodiments decribed above, which may be varied widely within the scope of the invention as defined by the appending claims.

Claims

1. Mooring chain connector assembly for a floating device, such as for example a vessel or a floating offshore platform, comprising a (in a non-loaded situation) substan-tially vertically extending channel means attached to the floating device for the passage of a mooring chain, which channel means near its upper end is provided with mooring chain locking means and a substantially horizontally extend-ing first pivot axis around which the channel means can pivot relative to the floating device, the assembly further comprising an elongate member which is insertable through the channel means, said elongate member having an upper end shaped for lockingly cooperating with the locking means, and a lower end connected to an upper end of a lever arm through a second substantially horizontally extending pivot axis in-cluding an angle with the first pivot axis, wherein a lower end of said lever arm is provided with coupling means for coupling the mooring chain to the lever arm.

2. Mooring chain connector assembly according to claim 1, wherein the second pivot axis extends perpendicu-larly to said first pivot axis.

3. Mooring chain connector assembly according to claim 1 or 2, wherein the lever arm is provided with a third pivot axis extending substantially in parallel to the first pivot axis.

4. Mooring chain connector assembly according to one of the previous claims, wherein at least the upper end of the elongate member is shaped in correspondence with the shape of the mooring chain.

5. Mooring chain connector assembly according to any of the previous claims, wherein the elongate member at least locally has a cross-section closely matching the in-ternal cross-section of the channel means.

6. Mooring chain connector assembly according to claim 5, wherein the elongate member at least at one length- wise position has a shape for clampingly engaging the chan-nel means.

7. Mooring chain connector assembly according to any of the previous claims, wherein the coupling means at the lower end of the lever arm comprise a pin insertable through a shackle of the mooring chain.

8. Mooring chain connector assembly according to any of the claims 1-6, wherein the coupling means at the lower end of the lever arm are of the type allowing an ad-ustable coupling with the mooring chain.

9. Elongate member for application in a mooring chain connector assembly in accordance with any of the pre-vious claims, which elongate member is insertable through the channel means, said elongate member having an upper end shaped for lockingly cooperating with the locking means, and a lower end connected to an upper end of a lever arm through a second substantially horizontally extending pivot axis in-cluding an angle with the first pivot axis, wherein a lower end of said lever arm is provided with coupling means for coupling the mooring chain to the lever arm.

10. Elongate member according to claim 9, wherein the second pivot axis extends perpendicularly to said first pivot axis.

11. Elongate member according to claim 9 or 10, wherein the lever arm is provided with a third pivot axis extending substantially in parallel to the first pivot axis.

12. Elongate member according to one of the claims 9-11, wherein at least the upper end of the elongate member is shaped in correspondence with the shape of the mooring chain.

13. Elongate member according to any of the claims 9-12, wherein the elongate member at least locally has a cross-section closely matching the internal cross-section of the channel means.

14. Elongate member according to claim 13, wherein the elongate member at least at one lengthwise position has a shape for clampingly engaging the channel means.

15. Elongate member according to any of the claims 9-14, wherein the coupling means at the lower end of the lever arm comprise a pin insertable through a shackle of the mooring chain.

16. Elongate member according to any of the claims 9-14, wherein the coupling means at the lower end of the lever arm are of the type allowing an adjustable coupling with the mooring chain.

17. Mooring chain member assembly for a floating device substantially as hereinbefore described and with reference to the accompanying drawings.

18. Elongate member substantially as hereinbefore described and with reference to the accompanying drawings.