Patent Grant
7976246
The present embodiments relate to a method for deploying a deepwater mooring spread from a heavy lift vessel using a staged neutral buoyancy polymer line deployment system.
A need exists for a system for deploying moorings in very deep water using a system of polymer lines and buoys for faster deployment than current techniques.
A deepwater deployment system is described in Applicant's U.S. Pat. No. 6,964,552 and is incorporated herein by reference.
A further need exists for a system for deploying suction piles in deep water using two heavy lift cranes that is systematic and does not cause any chafing on the edge of a floating vessel.
The present embodiments meet these needs.
The detailed description will be better understood in conjunction with the accompanying drawings as follows:
The present embodiments are detailed below with reference to the listed Figures.
Before explaining the present system in detail, it is to be understood that the system is not limited to the particular embodiments and that it can be practiced or carried out in various ways.
The present embodiments generally relate to a system for deploying a deepwater mooring spread from a floating vessel with a deck, using an aft crane secured to a port side or a starboard side of the floating vessel, and a fore crane secured to the port side or starboard side of the floating vessel. The floating vessel can be a heavy lift vessel.
One of the benefits of this system is the ability to deploy heavy structures to almost unlimited water depths by using a polymer line as a temporary lift pennant, the lift pennant can be a mooring line as well.
Turning now to the Figures,
A floating vessel 8, is shown with a hold 9 which can accommodate a suction pile 26. Additional suction piles and anchors can be accommodated in the hold 9. In addition, the suction piles can be oriented horizontally or vertically.
In an embodiment the suction piles or anchors can be on the deck 10 of the floating vessel 8, which can be a heavy lift ship with bow and stern, a barge with cranes with or without propulsion, or another types of movable vessels.
In this embodiment, the suction piles can be vertically arranged in the hold for ease of lifting by cranes secured to the starboard side or port side of the hull of the floating vessel 8. For example, between 1 suction pile to 18 suction piles can be used to create the deepwater mooring spread of this novel system. Any number can be deployed as long as all the suction piles or anchors fit on or in the floating vessel.
The floating vessel can have a length between about 60 meters to about 400 meters, and a weight of between about 3000 tons to about 50,000 tons when empty
Each suction pile anchor chain 27 can be connected with a pad eye at the lower side of the suction pile 26, or anchor. At the other side of the suction pile anchor chain 27 can be a remote operated connector 29, which can connect the suction pile anchor chain 27 to the polymer line, which is shown in
Returning to
The floating vessel can have two cranes, a fore crane not shown in this Figure, and an aft crane 18. The order of use of the cranes can be reversed in another embodiment of this system.
These cranes can be pedestal cranes or mast cranes such as those made by Huisman-Itrec located near Rotterdam, the Netherlands or any other manufacturer. The cranes notably have the features of being able to lower loads to water depths of at least 800 meters by use of a deepwater deployment system, comprised of a winch in the lower hold with the lifting wire of between about 2000 meters to about 25000 meters guided via sheaves to the jib head of the crane and lift tackle.
A load bearing structure 15 can be connected to an outboard starboard side 14 in
Secured to the load bearing structure 15 can be a hang-off 20 for securing, removably, one or more polymer lines deployed with this system. The load bearing structure 15 can be a steel plate that can be reinforced with steel brackets. For example, the load bearing structure 15 can be a perforated steel plate that can be powder coated having a length of between about 6 meters to about 20 meters, a width of between about 2 meters to about 10 meters and a thickness of between about 0.5 meters to about 1.5 meters, such as a tweendeck hatch cover or any other load bearing structure.
A reel drive 16 can be fixedly secured to the load bearing structure 15. The reel drive 16 can be used for deploying at least one, and up to 6 polymer lines for a single mooring line.
In this
The aft crane main block 19 is shown supporting the suction pile 26 at the first remote operated shackle 25.
The first polymer line 30 is shown connected while the suction pile top is out of the water, to remote operated connector 29 while the suction pile anchor chain 27 is shown connected to the first lift sling 33, the second lift sling 35 and third lift sling 37.
A remote operated vehicle 44 is shown for disengaging the aft crane main block 19 from the suction pile's first remote operated shackle 25. In this figure, the three pad eyes 28a, 28b and 28c shown connected a first lift sling 33, a second lift sling 35 and a third lift sling 37, for supporting the suction pile 26 is depicted as well as the first remote operated connector 29 for use with the suction pile anchor chain 27.
It should be noted that the end of the first polymer line 30 is secured to the hang-off 20 prior to allowing the aft crane main block 19 going slack so that the hang-off can support the load from the first polymer line.
When the required depth has been reached, the end socket of the second polymer line 32 is taken from the reel drive 16. With an auxiliary hoist, the end socket of the second polymer line is placed in the hang-off 20 on the structure. Gradually the suction anchor is lowered with the aft crane main block and the load is transferred to the second polymer mooring line 32 and placed in the hang-off 20.
The first and second polymer lines connected in series can then be lowered with the suction pile and the load can then be transferred to the buoy which is supported by the fore crane. The first remote operated shackle of the aft crane can then be released and the aft crane main block can be retrieved to the deck of the floating vessel. A suction pile can then be supported by the polymer lines and the fore crane can lower the suction pile to into the sea floor.
In an embodiment, the suction pile 26 can also be lowered to the sea floor with the aft crane 18 by placing the heave compensator 45 in the lift rigging. The first polymer line 30 and the second polymer line 32 must suit the water depth for the suction pile to be lowered to the sea floor.
In an additional embodiment, the suction pile 26 with the first polymer line 30 and second polymer line 32 already connected to the buoy 41 can be supported by the fore crane 17 with the heave compensator 45. The polymer lines, buoy, chains and heave compensator must suite the water depth so that the fore crane can sufficiently lower the suction pile 26 into the sea floor for full penetration.
The suction pile 26 and suction pile anchor chain can be lowered with the fore crane into the sea floor until at least about 0.5 meters to about 1.5 meters of penetration occurs. The remote operated vehicle 44 can include a suction pump, not shown, which can connect to the suction pile 26. The remote operated vehicle can start its suction pump and the suction pile can be pushed into the sea floor using hydrostatic pressure. In this Figure, the three lift slings are depicted holding the suction pile 26 in a vertical position. This Figure further shows the remote operated connector 29 holding the suction pile anchor chain 27 in an almost vertical position.
In additional embodiments, a ballgrab or an alternative connector can be used to connect the suction pile anchor chain to the polymer lines. An example of a ballgrab can be one made by Balltec Ltd. However, any remote operated connector can be used with the system.
In addition, more than two buoys can be in the hold or on the deck of the floating vessel.
It should be noted that more than one deepwater deployment system can be secured in the hold enabling both cranes to lower each crane's main block to water depths of at least about 1500 meters. Each deepwater deployment system can have a winch outfitted with a lifting wire of between about 2000 meters to about 25000 meters which can be guided by sheaves to the crane jib head and lift tackle.
The polymer lines can be made of polyester, Aramide, Kevlar, or a possible composite line, such as a graphite composite material or Dyneema. Any polymer line with neutral buoyancy can be used.
Additionally in an embodiment, when the suction pile is first lowered to the sea floor and allowed to penetrate to a first depth under its own weight, this initial penetration can be between about 0.5 meters to about 1.5 meters. Once the remote operated vehicle pumps out entrapped water from the suction pile, the suction pile has penetrated into the sea floor up to about 80 percent of its body. Any remote operated vehicle can be used to pump out the entrapped water.
While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3640400 | Becraft | Feb 1972 | A |
| 3716154 | Berg et al. | Feb 1973 | A |
| 6457908 | Bergeron | Oct 2002 | B1 |
| 6964552 | Krabbendam | Nov 2005 | B1 |
| Number | Date | Country |
|---|---|---|
| 59648 | Sep 1982 | EP |
