NO20160477A1

NO20160477A1 - A tool for operating a chain stopper

Info

Publication number: NO20160477A1
Application number: NO20160477A
Authority: NO
Inventors: Torkjell Lisland; Bjørn Møller; Henrik Strand
Original assignee: Scana Offshore Vestby As
Priority date: 2016-03-21
Filing date: 2016-03-21
Publication date: 2017-09-22

Description

FIELD OF THE INVENTION

The following invention relates to a tool for operating a chain stopper in a mooring arrangement for floating vessels or buoys and a chain stopper configured to cooperate with said tool.

The present invention is in particular suitable for use with a type of fairlead arrangement shown and described in NO20150515 by the same applicant, which is incorporated herein by reference, provided that the chain stopper is modified as will be described below.

It is also suitable for use with other types of fairlead arrangements, such as those shown in GB 2351058 and US 2010175604, also provided that the chain stopper is modified as described below.

BACKGROUND OF THE INVENTION AND PRIOR ART

When a vessel or a buoy is moored for a prolonged time, the mooring chains will slacken due to stretching and wear of the chain and possible shifting of anchors. Hence, the chains must be tightened regularly. This necessitates operation of the chain stoppers, which holds the chain back and ensures that the mooring forces are transferred from the chain to the fairlead arrangements and hence to the vessel.

The standard solution is to equip the chain lock with remotely operated actuators, e.g., hydraulic actuators. However, the actuators will be idle for most of the time and they are exposed to seawater or at least sea spray. Therefore, the actuators and related parts will be subject to a high degree of wear and risk of damage. Hence, they will have to be checked and maintained regularly to ensure that they will work when needed. A faulty actuator may lead to great delays of the mooring adjustment operation and hence increased costs. Both maintenance and repair will be risky for the persons that have to perform the

demounting and mounting of the actuator.

An alternative solution is to remove the actuators when not in use. This is very complicated, it involves the use of tools to unscrew the actuators, and pose great risks for the persons who perform the task.

In a further alternative, if the chain stoppers are accessible from the deck, they may be operated directly by a person on the deck. This may be risky as the person could fall into the water. Often the chain stopper is either close to the water surface or even below the water surface, which makes it too difficult to access from the ship. Then the chain stopper may be operated by a diver or an ROV. Using a diver is also very risky, and an ROV is expensive and must be operated by personnel specially trained for this.

SUMMARY OF THE INVENTION

The present invention has as a main objective to reduce risks for personnel involved in the mooring adjustment.

An additional objective of the present invention is to reduce the need for maintenance and the risk of failure.

The above objectives are achieved by a tool for operating a chain stopper in a mooring arrangement, comprising a support basis to which is coupled at least one actuator; said tool also håving a lock means to hold the tool in a fixed position relative to the chain stopper, and that in said fixed position the actuator is capable of pushing directly or indirectly on a lever arm of said chain stopper to operate said chain stopper.

In an improved tool the at least one actuator is coupled to swing a push arm about a hinge, said push arm being configured to act on said lever arm of said chain stopper.

In an alternative embodiment said actuator is coupled between a first and a

second push arm, each said push arm acting on a respective lever arm.

In a preferred embodiment, said lock means comprises at least one lock actuator that is coupled to a lock pin, said lock pin being in line with a recess or hole in the mooring arrangement when the tool is in the position to be fixed relative to the chain stopper.

In a further improved embodiment, the at least one push arm has a first part that is hinged to the support basis and a second part that is set at a right angle to the first part, said second part håving a recess that is adapted to receive a distal end of said lever arm.

Preferably, said support basis has guides set at a right angle at opposite sides of said guide basis and that each said guide is equipped with a lock actuator.

Further preferably, said support basis and said guides form a general U-shape that is corresponding with an outer shape of said mooring arrangement close to said chain stopper.

A preferred way of guiding the tool to the fixed position would be to equip it with attachment features for one or more guide lines.

The invention also concerns a chain stopper adapted to be operated by the tool of the invention. The chain stopper comprises at least one lever arm that is coupled to a stopper arm, said lever arm being hinged for angular displacement from a position where the stopper arm is within the path of the chain and a position where the stopper arm is out of the path of the chain, said lever arm håving a distal end positioned to cooperate directly or indirectly with an actuator of the tool, when the tool is in the fixed position.

In a preferred embodiment, a spring is arranged to return the lever arm to the position where the stopper arm is within the path of the chain. Thereby, it is not

necessary for the actuator to draw the lever arm back.

In a preferred embodiment the chain stopper comprises a receptacle to receive said tool in said fixed position. This aids in defining the fixed position of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a fairlead arrangement that is equipped with a chain stopper according to the invention in longitudinal section, Figure 2 shows the lower part of the fairlead arrangement with the chain stopper in perspective view, Figure 3 shows a tool according to the present invention in perspective view from a first side, Figure 4 shows the tool of figure 3 in a perspective view from a second opposite side, Figure 5 shows the tool of figures 3 and 4 in a side elevation view from a first side, Figure 6 shows the of figures 3, 4 and 5 in a side elevation view from a second side, Figure 7 shows the of figures 3, 4, 5 and 6 in a side elevation view from a third side,

Figure 8 shows the of figures 3, 4, 5, 6 and 7 in a planar view,

Figure 9 shows the lower part of the fairlead arrangement with a tool according to the present invention mounted for operation of the chain lock, Figure 10 shows the fairlead arrangement with the tool in a partly longitudinal

section seen from a first side,

Figure 11 shows the fairlead arrangement with the tool in a partly longitudinal section seen from a second opposite side, and Figure 12 shows an alternative embodiment of the tool of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 shows a fairlead arrangement or mooring unit 1. It comprises a mooring unit arm 1a, which has a distal end 2 and a proximal end 3. In mounted and operational state, the distal end 2 faces the seabed and is directed in the same direction as a mooring chain 4 that is coupled to the mooring unit 1 and extends towards a seabed anchor (not shown).

At the proximal end 3 is a dual axis hinge 5. The hinge 5 is coupled to the vessel or buoy (not shown) through per se known means. The chain 4 extends through the mooring unit 1 from the distal end 2 to the proximal end 3 and through the hinge 5. A detailed description of this fairlead arrangement 1 may be found in the above-mentioned NO20150515.

At the distal end 2 is a chain stopper 6. Whereas figure 1 shows the distal end 2 in longitudinal section, figure 2 shows the distal end 2 in perspective view.

The chain stopper 6 comprises a pair of stopper arms 7, which are hingedly attached to the mooring unit arm 1a at a hinge 8. The free end of the chain stopper arms 7 is adapted to abut a chain link 4a of the chain 4.

A lever arm 9 is coupled to each stopper arm 7. Next to the hinge 8 is an abutment 10, which limits the angle of movement of the stopper arms 7.

A spring 11 is coupled between the lever arm 9 and a fixed point at the mooring unit arm 1a.

By pulling the lever arms 9 towards the distal end 2 (i.e. downwards in figures 1 and 2), the stopper arms 7 will be swung towards the abutments 10 and out of the way of the chain ling 4a, and hence the chain 4 will be allowed to move unrestricted along the mooring unit 1.

Referring to figure 2, is shown a receptacle in the form of a pair of hooks 12, the function of which will be explained below, which are attached to the outer surface of the mooring unit arm 1a.

Figures 3 and 4 show a tool according to the invention in perspective view from two opposite sides. Figures 5, 6, 7 and 8 show the tool on different planar

views. The tool comprises a support basis in the form of a support plate 13. The support plate 13 has a pair of push arms 14 that are hinged to the support plate 13 at opposite side by hinges 15. The push arms 14 have a first part 14a that is in the same plane as the support plate 13 and a second part 14b, which extends at right angle from the distal end of the first part 14a. The second part 14b is shaped with a recess 14c, the purpose of which will be explained below.

At the distal end of the second part 14b is a bracket 16 that hingedly received a first end of an actuator 17.

The second opposite end of the actuator 17 is hinged to a pedestal 18, which is attached to the support plate 13.

The support plate 13 also has a pair of guides in the form of guide plates 19, which are set at right angles to the plane of the support plate 13. The guide plates 19 have each a lock actuator 20, which actuate a lock pin 21.

The support plate 13 has a plurality of ears 22 on a first face and on a second opposite face, it has a set of glide strips 23.

The guide plates are also equipped with glide strips 24.

As shown in figures 6 and 7, the actuator 17 can extend to swing the push arms 14 about the hinges 15, from a retracted position, shown in solid lines to

an extended position 14', shown in dotted lines.

Figure 9 shows the tool attached to the distal end 2 of the mooring unit arm 1a. Figures 10 and 11 show the tool attached to the mooring unit arm 1a in the same view as in figure 1.

To bring the tool to the attachment on the mooring unit arm 1a, lines, such as wires, (not shown) are coupled to the ears 22. The lines may be controlled by lifting equipment, such as a crane, or be controlled by hand. The tool is lowered by the use of the lines until the tool lies with the face of the support plate 13 håving the glide strips 23, against the mooring unit arm 1a. The tool is then lowered towards the distal end 2 until it meets the hooks 12. In this position, the lock actuators 20 are remotely activated to bring the lock pins 21 into recesses or holes (not shown in the mooring unit arm 1a. The tool is now locked in place and cannot move. In this position, the outer end of the lever arms 9 will be situated within the above-mentioned recess 14c in the push arms 14. This situation is shown in figure 10.

Now the actuators 17 are remotely activated. This will bring the push arms 14 downwards (as seen in the figures) and push the lever arms 9 towards the distal end of the mooring unit arm 1a. This will in turn bring the stopper arms 7 out of the path of the chain 4 and hence the chain stopper 6 will be open, as shown in figure 11.

When the adjustment of the chain 4 has been completed, the actuators 17 are retracted. The springs 11 will pull the lever arms 9 and hence the stopper arms 7 back to the locked position. The lock actuators will be activated to bring the lock pins out of their holes in the mooring unit arm 1a. The tool can now easily be lifted back up.

As the tool as only been exposed to seawater for a relatively short time, it can be rinsed with fresh water, dried and put away in a dry and safe place awaiting

the next use.

Figure 12 shows another embodiment of the tool. It differs from the above embodiment mainly in the fact that a single actuator 17' is coupled between a respective distal end of the first part 14a of the push arms 14. This allows for a smaller and simpler tool, as the pedestals 18 can be removed and hence the support plate 13 can be made somewhat smaller.

Extension of the single actuator 17' will push both the push arms 14 downwards.

Although the above embodiments show a chain stopper with two stopper arms and a tool with two push arms, it is conceivable that only one stopper arm and hence one push arm is necessary to retain the chain relative to the mooring unit arm.

A further alternative embodiment would be to omit the push arm of the embodiment in figures 3-11 and mount the cylinder of the actuator at a fixed angle on the support base. Then the piston rod of the actuator can act as a push rod and push directly on the lever arm. By equipping the distal end of the piston rod with a large head, the head would push against the lever arm even though the distal end of the lever arm moves through a semi-circle during the operation. Alternatively, the distal end of the lever arm may be equipped with a large head.

Claims

1. A tool for operating a chain stopper in a mooring arrangement,characterised in thatit comprises a support basis to which is coupled at least one actuator; said tool also håving a lock means to hold the tool in a fixed position relative to the chain stopper, and that in said fixed position the actuator is capable of pushing directly or indirectly on a lever arm of said chain stopper to operate said chain stopper.

2. The tool of claim 1,characterised in thatit further comprises at least one push arm, said at least one actuator being coupled to swing the push arm about a hinge, said push arm being configured to act on said lever arm of said chain stopper.

3. The tool of claim 1,characterised in thatsaid actuator is coupled between a first and a second push arm, each said push arm acting on a respective lever arm.

4. The tool of any of the preceding claims,characterised in thatsaid lock means comprises at least one lock actuator that is coupled to a lock pin, said lock pin being in line with a recess or hole in the mooring arrangement when the tool is in the position to be fixed relative to the chain stopper.

5. The tool of any of the preceding claims,characterised in thatthe at least one push arm has a first part that is hinged to the support basis and a second part that is set at a right angle to the first part, said second part håving a recess that is adapted to receive a distal end of said lever arm.

6. The tool of any of the preceding claims,characterised in thatsaid support basis has guides set at a right angle at opposite sides of said guide basis and that each said guide is equipped with a lock actuator.

7. The tool of any of claim 6,characterised in thatsaid support basis and said guides form a general U-shape that is corresponding with an outer shape of said mooring arrangement close to said chain stopper.

8. The tool of any of the preceding claims,characterised in thatit is equipped with attachment features for one or more guide lines.

9. A chain stopper adapted to be operated by the tool of any of the claims 1 - 8,characterised in thatis comprises at least one lever arm that is coupled to a stopper arm, said lever arm being hinged for angular displacement from a position where the stopper arm is within the path of the chain and a position where the stopper arm is out of the path of the chain, said lever arm håving a distal end positioned to cooperate directly or indirectly with an actuator of the tool, when the tool is in the fixed position.

10. The chain stopper of claim 9,characterised in thata spring is arranged to return the lever arm to the position where the stopper arm is within the path of the chain.

11. The chain stopper of claim 9 or 10,characterised in thatit comprises a receptacle to receive said tool in said fixed position.