NO346876B1

NO346876B1 - Mooring system for enabling quick release of a vessel

Info

Publication number: NO346876B1
Application number: NO20210035A
Authority: NO
Inventors: Klepsvik Øystein
Original assignee: Oeystein Klepsvik
Priority date: 2021-01-12
Filing date: 2021-01-12
Publication date: 2023-02-06
Also published as: NO20210035A1; WO2022154670A1

Description

Mooring system for enabling quick release of a vessel

Field of the invention

The invention relates to a mooring system for enabling quick release of a vessel. The invention also relates to a method.

Background of the invention

Standby vessels are commonly deployed out on the offshore oil field to perform various tasks and to be a safety standby in case of emergencies. These vessels are standby a considerable part of the time they spend out at sea. Some of them spend their time moored to a suction anchor at the seabed to conserve fuel and to maintain its position in between operations.

Hybrid propulsion systems is getting more and more common for many types of vessels. In a hybrid propulsion system, the propulsion motors are electrical motors. Diesel engines typically drives generators that generates electricity for supplying the electrical motors and for charging batteries as a buffer. The diesel engines can then be run with stable load and speed which is an advantage with respect to reducing maintenance and fuel consumption. When the generators generate more power than needed the power can be stored in batteries, and when the generators generate less power than needed power can be supplemented from the batteries or the electrical motors can run only on power from the batteries for a limited time, before the diesel engines need to be started again.

Standby vessels can be equipped with a hybrid propulsion system, and if the batteries in the hybrid propulsion system could be charged between operations, when the vessel is moored out in the field, the vessel could operate most of the time without burning fossil fuel due to the relatively short operating radius from the mooring location. It is therefore need for a system for generating renewable energy at the site to supply power to standby vessels, but also for other types of vessels with similar mode of operation.

Disclosure of the state of art

US4033277A describes a mooring line or cable system for a drillship including a hull adapted to float in water at a water-line. The mooring line being in the general form of a catenary chain line. The mooring line includes a drillship portion secured to a winch on the drillship and entraining a sheave, and a first spar buoy and an anchor portion including an anchor chain and an anchor and a second spar buoy. A two-part, remote controlled quick disconnect element is provided, one part being connected to the drillship portion and another part being connected to the anchor portion. The two parts being adapted to connect the first spar buoy and the second spar buoy together, to provide an anchored mooring line.

US4509448A describes a disconnect/connect mooring system for a turret moored drillship. The system includes an anchor, a first mooring line connected at one end to the anchor, including a length of wire rope and a mooring line chain, a submersible buoy connected to the mooring line chain and a second mooring line connected to the buoy chain and extending to the turret moored drillship.

Objects of the present invention

The invention has one or more of the following objects:

- providing a quick release mooring system

- providing a mooring system that can harvest energy from the movement of a vessel - providing a single point mooring system that can harvest energy from the movement of a vessel

- providing a mooring system for mooring a vessel to an anchor where the mooring can be dropped into the water and immediately being ready to be picked up and used for mooring a vessel again

- providing a mooring system where the vessel to be moored can do so without assistance from other vessels

Summary of the invention

The invention relates in one aspect to a mooring system for enabling quick release of a vessel. The system comprises:

- an anchor at the seabed,

- a mooring winch, mounted on the vessel, the mooring winch comprises a mooring line drum,

- a mooring line is arranged to be spooled up on to the mooring line drum, the mooring line is connected to the anchor in a first end and releasable connected to the mooring line drum in a second end,

- a pick-up line drum, the pick-up line drum is floatable in water, configured to be releasable connected to the mooring winch as an axial extension to the mooring line drum and arranged to rotate with the mooring line drum, and - a pick-up line arranged to be spooled up on to the pick-up line drum, the pick-up line is connected to the mooring line in a first end and connected to the pick-up line drum in a second end.

The system is arranged so that the vessel can be released by spooling the mooring line off the mooring line drum, disconnecting the mooring line and the pick-up line drum and dropping the mooring line with the connected pick up line and pick-up line drum into the water.

The mooring winch can be arranged to maintain a predefined tension in the mooring line by spooling in and out mooring line as the vessel moves relative to the anchor.

The mooring line can comprise a mooring connector attached to the second end of the mooring line and the mooring line drum comprises a mooring connector receiver, wherein the mooring connector is connectable to and releasable from the mooring connector receiver.

The mooring system can further comprise a pick-up winch mounted on the vessel, wherein the pick-up line drum is connectable to the pick-up winch for spooling in the pick-up line to bring the mooring line onboard the vessel when mooring.

The pick-up winch can be mounted above the mooring winch so that when spooling in the pick-up line the pick-up line and the connected mooring line passes over the mooring line drum for enabling easy connection of the mooring line to the mooring line drum.

The mooring system can further comprise a second pick-up line attached to a second pick-up line drum for replacing the pick-up line and pick-up line drum after the mooring line is pulled onboard the vessel and connected to the mooring winch.

The mooring winch can further comprise a release mechanism for disconnecting the mooring line from the mooring line drum and a release mechanism for disconnecting the pick-up line drum from the mooring winch so that the mooring line will drop into the water together with the connected pick-up line and pick-up line drum.

The mooring winch can further comprise a tension sensor, a motor and controls arranged to maintain a predefined tension in the mooring line when the mooring line is connected to the mooring winch, the tension is maintained by spooling in and out mooring line as the vessel moves due to external forces such as wind and waves.

The mooring winch can comprise a generator for utilizing the rotational movement on the mooring line drum to harvest energy.

The generator can be a combined electric generator and motor equipped with controls for maintaining a predefined tension in the mooring line and for generating power when mooring line is pulled out due to increased tension in the mooring line.

In another aspect the invention relates to a method for mooring a vessel, and for quickly releasing said vessel from the mooring. The method comprises the steps of:

a) mooring the vessel using a mooring system comprising:

- an anchor at the seabed,

- a mooring line with a first end and a second end, where the first end is connected to the anchor and the second end is releasable connected to the mooring line drum,

- a pick-up line drum, which is floatable in water and releasable connected to the mooring winch as an axial extension to the mooring line drum, and

- a pick-up line connected to the mooring line in a first end and connected to the pick-up line drum in a second end,

b) spooling out any mooring line left on the mooring line drum,

c) releasing the mooring line from the mooring line drum,

d) releasing the pick-up line drum from the mooring winch, and

e) dropping the mooring line and the pick-up line drum with the spooled up pick-up line attached to the mooring line into the water.

The method can further comprise to connect the vessel to the mooring line that is in the water by preforming the following steps:

f) maneuvering the vessel in position for mooring the vessel to the anchor, g) picking up from the water the pick-up line drum,

h) connecting the pick-up line drum to the mooring winch,

i) spooling the pick-up line onto the pick-up line drum using the mooring winch, thus lifting the mooring line onboard the vessel,

j) connecting the second end of the mooring line to the mooring line drum, k) spooling in mooring line until a predefined tension in the mooring line is reached, and

l) maintaining the predefined tension in the mooring line by spooling in and out mooring line as the vessel moves relative to the anchor due to external forces such as waves, tide and wind.

f) connecting a second pick-up line drum with a spooled up second pick-up line to the mooring winch as an axial extension to the mooring line drum, g) maneuvering the vessel in position for mooring the vessel to the anchor, h) picking up from the water the pick-up line drum,

i) connecting the pick-up line drum to a pick-up winch,

j) spooling the pick-up line onto the pick-up line drum) using the pick-up winch, thus lifting the mooring line onboard the vessel,

k) connecting the second end of the mooring line to the mooring line drum, l) disconnecting the pick-up line from the mooring line,

m) connecting the second pick-up line to the mooring line,

n) spooling in mooring line until a predefined tension in the mooring line is reached, and

o) maintaining the predefined tension in the mooring line by spooling in and out mooring line as the vessel moves relative to the anchor due to external.

External forces can be forces such as waves, tide and wind.

The method can further comprise the steps of harvesting energy from the rotation of the mooring line drum as the mooring line drum) rotates due to the vessels movement resulting from external forces such as wind, tide and waves.

In another aspect the invention relates to a floatable pick-up line drum for spooling up a pick-up line, wherein the pick-up line drum is arranged to be releasable connected to a winch onboard a vessel.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Fig. 1 shows the winches of the mooring system from an angel in front of the vessel. Fig. 2 shows the winches of the mooring system from the starboard side of the vessel.

Fig. 3 shows the vessel arriving at the location of the anchor

Fig. 4 shows the vessel and the mooring system after the mooring line is taken onboard the vessel

Fig. 5 shows vessel moored

Description of preferred embodiments of the invention

The invention relates to a mooring system 10. In one embodiment the mooring system 10 comprises an anchor 11, a mooring line 22 and a mooring winch 20. The mooring winch 20 further comprises a mooring line drum 21 that the mooring line 22 can be spooled onto. The mooring line 22 is attached to the anchor 11 in a first end while a second end is equipped with a mooring connector 23. The mooring connector 23 is shaped to fit with a mooring connector receiver 24 on the mooring line drum 21 for connecting the mooring line 22 to the mooring line drum 21.

The mooring connector receiver 24 can be a recess or milled profile in the drum or drum shaft or similar and the mooring connector 23 is shaped to hook in the mooring connector receiver. Preferably, the mooring connector 23 is flush with the mooring line drum 21 so that the mooring line 22 can be spooled onto the mooring line drum 21 on top of the mooring connector 23. When there is no mooring line 22 spooled onto the mooring line drum 21 the mooring connector 23 can be released from the mooring connector receiver 24 manually or remotely by a remotely operated releasing mechanism in the mooring line drum 21.

The anchor 11 can be a suction anchor on the seabed 3. The anchor can be equipped with a swivel or turret for connecting the mooring line to the anchor 11. The swivel or turret can have unrestricted rotation around the vertical axis on top of the anchor 11, which then allows the vessel 1 to weather vane around the anchor 11.

For the crew of the vessel 1 to be able to get hold of the mooring line 22 when the vessel 1 arrives at the location of the anchor 11 the mooring system 10 further comprises a pick-up line 32 and a pick-up winch 30 for spooling in the pick-up line 32. The pick-up line 32 is releasable connected to the mooring line 22 in a first end and connected to a pick-up line drum 31 in a second end. Preferably the pick-up line 32 is connected to the mooring line 22 close to the second end of the mooring line 22. The pick-up line 22 can also be connected to the mooring connector or at the second end of the mooring line 22 if there is no mooring connector 23. The pick-up line drum 31 is arranged to float on the water surface 4 so it can be used as a buoyancy buoy for the pick-up line 22. The pick-up line drum 31 is arranged to be connected to the pick-up winch 30 so the pick-up line 32 can be spooled onto the pick-up line drum 31.

The pick-up lines are commonly used when mooring as a mean for lifting a mooring line onboard a vessel. Mooring lines are strong and heavy and can be in the form of chains, steel rope or other types of rope. Pick-up lines are lighter and less bulky but need to strong enough to handle the weight of the mooring line, but not necessarily strong enough to handle the forces of a moored vessel. When mooring to a suction anchor or any other subsurface anchoring point pick-up lines are used to get hold of the mooring line which might not float. The pick-up line together with a floating buoy is therefore desirable to get hold of the mooring line and bring in onboard the vessel.

When the vessel 1 arrives at the mooring location the crew will capture the pick-up line drum 31 or the pick-up line 32 that floats in the water 2. The pick-up line drum 31 will be brought onboard and connected to the pick-up winch 30 so that the pick-up line 32 can be spooled onto the pick-up line drum 31 to lift the mooring line 22 out of the water and onboard the vessel 1. The mooring connector 23 is then connected to the mooring winch 20. The pick-up line 32 is disconnected from the mooring connector 23 and a second pick-up line 32`, spooled up on a second pick-up line drum 31`, is connected to the mooring connector 23. The second pick-up line drum 31` is connected to the mooring winch 20 as an axial extension to the mooring line drum 21 (as seen in Fig.1). The second pick-up line drum 31` rotates with the mooring line drum 21.

The mooring winch 20 is arranged to spool in mooring line until a predefined tension is reached in the mooring line 22.

The mooring winch 20 can be driven by a hydraulic motor or an electric motor.

When the mooring line is pulled out, for example when the vessel 1 is lifted by a wave, a hydraulic motor/pump coupled to the mooring line drum 21 displaces hydraulic oil into a hydraulic pressure accumulator, where pressure is built up. This pressure will reverse the hydraulic motor/pump when the wave is going down again. The mooring winch 20 will then take in the slack and restore the predefined tension in the mooring line 22.

When the wave is lifting the bow of the vessel 1 up, thus rotating the mooring line drum and the hydraulic motor/pump sends hydraulic oil to the hydraulic pressure accumulator it goes through a second hydraulic motor, which takes out power for electricity generation. The electricity generated is then stored in batteries onboard the vessel. The stored electricity can then be used by various electric consumers onboard the vessel.

Alternatively, the mooring winch 20 can be powered by an electric motor. Then the electrical motor can both power the winch and work as a generator and as a brake for keeping the tension in the mooring line. All this can be achieved by controlling the electrical motor.

When the vessel 1 needs to disconnect from the anchor 11 the mooring winch 20 spools out the mooring line 22 until only the mooring connector 23 is left on the mooring line drum 21. The mooring connector 23 is released and the second pick-up line drum 31` is also released and dropped into the water 2.

As mentioned before the mooring connector 23 can be remotely released. To avoid the need for personnel and to avoid the HSE risk associated with having personnel in the area of the winches and mooring line the releasing and dropping of the second pick-up line drum 31`can be done remotely. This can for instance be achieved with an electromechanical releasing mechanism that disconnects the second pick-up line drum 31` from the mooring winch 20, at the same time as the mooring connector 23 is released. The mooring winch 20 and the area around the mooring winch 20 will need to be designed so that the mooring connector and the second pick-up line drum 31` can fall into the water unrestricted after being released. The pick-up line 32 can be secured to the second pick-up line drum 31` by a weak link to avoid that pick-up line is unintentionally spooled of the second pick-up line drum 31` before it leaves the vessel 1.

When the mooring line 22 and the attached second pick-up line 32` and second pickup line drum 31` falls into the water 2. The mooring line 22 will sink to the seabed 3, pulling on the second pick-up line 32` and spooling it of the second pick-up line drum 31`, leaving the second pick-up line drum 31` floating on the water surface 4 ready to be taken onboard the vessel 1 the next time it is going to moor to the anchor 11.

While the second pick-up line drum 31` and attached second pick-up line 32` is in the water 2 the pick-up line 32 and pick-up line drum 31 can be maintained and made ready to replace the second set 31`, 32` next time the vessel 1 is going to moor to the anchor 11. So that there is always a set of drums 31, 32 or 31` 32` ready for a quick release from the anchor.

In an alternative embodiment the system has only the mooring winch 20 and not the pick-up winch 30. The pick-up line drum 31 is connected to the mooring winch 20 as an axial extension to the mooring line drum 21 to pull onboard the mooring line 22. The pick-up line 32 is connected to the mooring line 22 at a distance from the end of the mooring line 22. Said distance on the mooring line 22 should be sufficient for the end of the mooring line 22, with or without the mooring connector, to connect to the mooring line drum 21 when there is tension on the pick-up line 32. When the mooring line then is connected the mooring line drum 21 the mooring winch 20 can rotate the two drums 21, 31 until tension is transferred to the mooring line 22. The pick-up line 32 can then preferably be disconnected and replaced, or alternatively used again.

Claims

1. A mooring system (10) for enabling quick release of a vessel (1), the system (10) comprises:

- an anchor (11) at the seabed (3),

- a mooring winch (20), mounted on the vessel (1), the mooring winch (20) comprises a mooring line drum (21), and

- a mooring line (22) is arranged to be spooled up on to the mooring line drum (21), the mooring line (22) is connected to the anchor (11) in a first end, the system (10) is characterized in that the mooring line (22) is releasable connected to the mooring line drum (21) in a second end, and in that the system (10) further comprises:

- a pick-up line drum (31), the pick-up line drum (31) is floatable in water, configured to be releasable connected to the mooring winch (20) as an axial extension to the mooring line drum (21) and arranged to rotate with the mooring line drum (21), and

- a pick-up line (32) arranged to be spooled up on to the pick-up line drum (31), the pick-up line (32) is connected to the mooring line (22) in a first end and connected to the pick-up line drum (31) in a second end,

wherein the system (10) is arranged so that the vessel (1) is releasable from the mooring by spooling the mooring line (22) off the mooring line drum (21), disconnecting the mooring line (22) and the pick-up line drum (31) and dropping the mooring line (22) with the connected pick up line (32) and pick-up line drum (31) into the water (2).

2.The mooring system (10) according to claim 1, wherein the mooring winch (20) is arranged to maintain a predefined tension in the mooring line (22) by spooling in and out mooring line (22) as the vessel (1) moves relative to the anchor (11).

3. The mooring system (10) according to claim 1 or 2, wherein the mooring line (22) comprises a mooring connector (23) attached to the second end of the mooring line (22) and the mooring line drum (21) comprises a mooring connector receiver (24), wherein the mooring connector (23) is connectable to and releasable from the mooring connector receiver (24).

4. The mooring system (10) according to any of the preceding claims, wherein the mooring system (10) further comprises a pick-up winch (30) mounted on the vessel (1), wherein the pick-up line drum (31) is connectable to the pick-up winch (30) for spooling in the pick-up line (32) to bring the mooring line (22) onboard the vessel (1) when mooring.

5. The mooring system (10) according to claim 4, wherein the pick-up winch (30) is mounted above the mooring winch (20) so that when spooling in the pick-up line (32) the pick-up line (32) and the connected mooring line (22) passes over the mooring line drum (21) for enabling easy connection of the mooring line (22) to the mooring line drum (21).

6. The mooring system (10) according to any of the preceding claims, wherein the mooring system (10) further comprises a second pick-up line (32`) attached to a second pick-up line drum (31`) for replacing the pick-up line (32) and pick-up line drum (31) after the mooring line (22) is pulled onboard the vessel (1) and connected to the mooring winch (20).

7. The mooring system (10) according to any preceding claims, wherein the mooring winch (20) further comprises a release mechanism for disconnecting the mooring line (22) from the mooring line drum (21) and a release mechanism for disconnecting the pick-up line drum (31) from the mooring winch (20) so that the mooring line (22) will drop into the water together with the connected pick-up line (32) and pick-up line drum (31).

8. The mooring system (10) according to any of the preceding claims, wherein the mooring winch (20) further comprises a tension sensor, a motor and controls arranged to maintain a predefined tension in the mooring line (22) when the mooring line (22) is connected to the mooring winch (20), the tension is maintained by spooling in and out mooring line (22) as the vessel (1) moves due to external forces.

9. The mooring system (10) according to any of the preceding claims, wherein the mooring winch (20) comprises a generator for utilizing the rotational movement on the mooring line drum (21) to harvest energy.

10. The mooring system according to claim 8, wherein the generator is a combined electric generator and motor equipped with controls for maintaining a predefined tension in the mooring line (22) and for generating power when mooring line (22) is pulled out due to increased tension in the mooring line (22).

11. A method for mooring a vessel (1) and for quickly releasing said vessel (1) from the mooring, wherein the method comprises the steps of:

a) mooring the vessel (1) using a mooring system (10) comprising:

- an anchor (11) at the seabed (3),

- a mooring winch (20), mounted on the vessel (1), the mooring winch (20) comprises a mooring line drum (21),

- a mooring line (22) with a first end and a second end, where the first end is connected to the anchor (11) and the second end is releasable connected to the mooring line drum (21),

- a pick-up line drum (31), which is floatable in water and releasable connected to the mooring winch (20) as an axial extension to the mooring line drum (21), and

- a pick-up line (32) connected to the mooring line (22) in a first end and connected to the pick-up line drum (31) in a second end, b) spooling out any mooring line (22) left on the mooring line drum (21), c) releasing the mooring line (22) from the mooring line drum (21),

d) releasing the pick-up line drum (31) from the mooring winch (20), and e) dropping the mooring line (22) and the pick-up line drum (31) with the spooled up pick-up line (32) attached to the mooring line (22) into the water.

12. The method according to claim 11, wherein the method further comprises to connect the vessel to the mooring line (22) that is in the water (2) by preforming the following steps:

f) maneuvering the vessel (1) in position for mooring the vessel (1) to the anchor (11),

g) picking up from the water (2) the pick-up line drum (31),

h) connecting the pick-up line drum (31) to the mooring winch (20),

i) spooling the pick-up line (32) onto the pick-up line drum (31) using the mooring winch (20), thus lifting the mooring line (22) onboard the vessel (1), j) connecting the second end of the mooring line (22) to the mooring line drum (21),

k) spooling in mooring line (22) until a predefined tension in the mooring line (22) is reached, and

l) maintaining the predefined tension in the mooring line by spooling in and out mooring line (22) as the vessel (1) moves relative to the anchor (11) due to external forces.

13. The method according to claim 11, wherein the method further comprises to connect the vessel to the mooring line (22) that is in the water (2) by preforming the following steps:

f) connecting a second pick-up line drum (31`) with a spooled up second pickup line (32`) to the mooring winch (20) as an axial extension to the mooring line drum (21),

g) maneuvering the vessel (1) in position for mooring the vessel (1) to the anchor (11),

h) picking up from the water (2) the pick-up line drum (31),

i) connecting the pick-up line drum (31) to a pick-up winch (30),

j) spooling the pick-up line (32) onto the pick-up line drum (31) using the pickup winch (30), thus lifting the mooring line (22) onboard the vessel (1), k) connecting the second end of the mooring line (22) to the mooring line drum (21),

l) disconnecting the pick-up line (32) from the mooring line (22),

m) connecting the second pick-up line (32`) to the mooring line (22), n) spooling in mooring line (22) until a predefined tension in the mooring line (22) is reached, and

o) maintaining the predefined tension in the mooring line by spooling in and out mooring line (22) as the vessel (1) moves relative to the anchor (11) due to external forces.

14. The method according to any of the claims 11-13, wherein the method further comprises the steps of harvesting energy from the rotation of the mooring line drum (21) as the mooring line drum (21) rotates due to the vessels (1) movement resulting from external forces.