Fast jack hybrid liftboat hull

Abstract

A liftboat with an improved hybrid hull which increases the speed and efficiency of the vessel and reduces the changes of damage should an accidental grounding occur with box beam construction, starboard and port catamaran hulls, a center barge hull, multiple legs, a jacking system for moving each upward and downward, and a retractable local bearing pad for each leg that engaged the seabed when in use. In addition, it proves a more streamlined housing for the retracted pads and a stronger integrated structure for the leg towers which guide and support the legs.

Description

This application claims priority from U.S. Provisional application Ser. No. 61/201,958 (“the '958 application”) filed Dec., 16, 2008. The '958 application is incorporated herein by reference.

FIELD OF THE INVENTION

This application relates to self-elevating boats known as Jack Up Boats/Jack Up Barges/Self Elevating Work Platforms or SEWOPS, used primarily in the oil and gas industry. More specifically, the present invention relates to a liftboat with an improved hull which increases the speed and efficiency of the vessel and reduces the changes of damage should an accidental grounding occur. In addition, it proves a more streamlined housing for the retracted pads and a stronger integrated structure for the leg towers which guide and support the legs.

BACKGROUND AND FIELD OF INVENTION

In the shallow coastal waters of the Gulf of Mexico, the oil industry has numerous small platforms and require maintenance and repair but have no space or facilities to accommodate the men and equipment to do the work. Trying to run a job from the deck of a floating supply boat or utility boat limited operations to the calmest of days. The need for a stable work platform that was not affected by rough seas was the catalyst for the development of the first liftboat. It was basically a barge that had three or four long legs made of large diameter heavy pipe with a hydraulic rack and pinion drive and large pads attached to their bottom. The legs were stuck onto the sides and stern of the barge and a pair of engines were added to travel and maneuver with as well as power the hydraulic jacking system. It worked. It worked well, and the concept has spread to other parts of the world. There is a need for these vessels in other countries.

Most things that have evolved in the sea become streamlined forms that slip through the water with little resistance. There are a few notable exceptions such as jellyfish and Liftboats. But like the jellyfish before them the liftboat has not developed into a sleek form that can choose a direction and cross an ocean at will. Crossing an ocean involves a “piggy back” ride on another ship that currently costs about $2 to $5 million dollars. That is why 97% of the liftboats in the world are still in the Gulf of Mexico. If a boat was fast enough it could be made seaworthy by having its legs cut off and lowered. That would bring the center of gravity down to make the boat sufficiently stable for a crossing. But what do you do about the speed? As can be seen in FIG. 1, which is a profile of typical prior art, there is not much in this hull form that is firth for moving smoothly through the water. The basic barge design has never been fast except for such lightweight sailing barges that could skim across the water if it was not too rough. Liftboats have never “skimmed.” It is still hard to get away from the barge form though, for this type of design. Barges are wide and stable and can carry a heavy load with their large volume of displacement. This gives them a good load carrying hull which can handle the high center of gravity that the legs cause and also provides a perfect deck shape with lots of space for carrying the equipment necessary for the job and room to work. A catamaran would give you the speed, space and deck form needed buy a cat's long relatively narrow hulls do not have the displacement needed for carrying the heavy deck loads of equipment these vessels have to haul to the jobsite. What to do?

SUMMARY OF THE INVENTION

The direction of this design effort has been to develop a second generation of liftboat hull design that eliminates most of the problems inherent in typical prior art. The result is a hybrid hull design that is a significantly radical and improved departure from prior art. The inventive hull changes modes as the vessel's mission changes. When running in an unloaded light boat condition such as in the initial deployment of the vessel to get to the dock where it will load the equipment and crew to perform a job, or if it was mobilized for an open water crossing the boat would run in the catamaran mode with its midsection 1′ to 2′ free of the water. When the boat is loaded the weight increased the draft which brings the midsection hull in contact with the water and the extra volume increased the displacement and load carrying capacity exponentially. With the increased weight of a full deckload the catamaran becomes a barge. It will move slower as a barge but at least now it is getting paid, and it got to the job twice as fast as any other competing vessel and it will still run faster than any conventional barge. FIGS. 2 and 3 respectively show a plan and profile of a liftboat using the new hull configuration. When compared to FIG. 1 several advantages can be readily seen. In typical prior art the propellers, skegs and rudders are hanging below the keel and the thrust line is pointed downward in a compromise of draft, displacement and hull form. In this configuration the most delicate and essential parts of the vessel's hull are the most exposed to damage when transiting or operating in shallow waters, and the downward pointing propellers can cost you 10% or more in the efficiency of your applied power. The hybrid hull of FIGS. 2 and 3 makes no compromise with its straight thrust line, simple but sleek double ended hull design and in its optimum configuration it also has a flat plate extension of the hull bottom which runs under the propellers and protests them from any debris which might extend from the shallow bottom. It also functions as a pitch dampener plate when underway and a handy work platform when it is time to pull the wheels and shafts for inspection or repair. It does all of this without increasing the overall draft of the vessel. When fully loaded its draft is comparable to a conventional barge design with low hanging props and rudders. If you do run it aground the vessel's “pads” or footing which are made to be bounded off the bottom extend slightly below the hull and are the most likely part of the boat to take the impact. It is a feature that can save a lot of expensive hull damage.

The extension of the catamaran hulls below the barge hull functions as a SOLAS required double bottom without adding building costs or extra maintenance problems. Its relatively narrow bows are simply to equip with a conventional bow thruster which adds to the maneuverability and safety of the vessel. Equipping a standard barge hull with a functional bow thruster is awkward at best. Also, in the hybrid design the engines are positioned at the extreme width of the hull as can be seen in FIG. 2. This gives the boat the maximum turning torque possible to help turn and maneuver. The important of this cannot be exaggerated when you have the drag of three or four legs a hundred feet down in the water and the current is carrying you sideways into a platform or drilling rig. This is a very credible scenario as the vessel's purpose requires it to maneuver and position itself often within a few feet of pipelines and platforms to complete its work.

There are some prior designs that have the leg towers and supports partially integrated into the hull but most have the legs attached to the sides and stern. Then using sponsons and bracing as in FIG. 1, give it the strength it needs. Structural problems are common in the sponsons and hulls using this “add on” type of approach. Especially in the larger more highly stressed designs. The inventive hybrid hull fully integrates the leg towers into its basic structure. This is a continuous box beam which forms a square that runs between the four legs (see FIG. 4). Very simple, very strong, very easy to build. The integrated leg tower also means that your precious jacking machinery and hoses can be below deck, safe from exposure to the effects of sun and saltwater, without having to build additional space robbing, heavy and expensive structures around the leg.

At first glance the inventive hybrid hull might seem more complicated and expensive to construct. But if you look again at FIG. 1 notice the sponsons and the overhangs with their bracing and the compound curve of the stern rake around the propellers. All the joints, supports and braces that have to be cut and fitted. Then imagine having to construct AND maintain a SOLAS compliant inner bottom. The simple barge is not so simple. When you look at the hybrid hull in FIGS. 2 and 3 think of the catamaran hulls below the barge as the inner bottom, but because of the 8′ overhead they are as easy to maintain as normal tanks.

The inventive hybrid hull design has no compound curves, overhangs or sponsons to complicate construction and maintenance. Not only is it easy to build with its simple curves, slab sides and 90 degree chines, its high freeboard offers greater protection for equipment riding on deck without sacrificing shallow water capacity.

In most previous designs the shape of the pads are restricted to a flat surface that will fit against the bottom of the sponson. These flat pads are not an optimum shape for pulling free of the bottom and have a tendency to hook under pipelines and also lift any debris and/or mud from the bottom up to be crushed against the hull which can cause expensive and time consuming repairs. A pyramid shaped pad which will shed debris and pipelines as it raises can be easily utilized and fits neatly into the catamaran hull. Space can be left around the upper pad just in case something manages to cling to the sloping sides so that there is no crushing damage. This can be done without causing any drag, or slop in the movement of the vessel's legs.

It is an object of this invention to provide a unique hybrid liftboat hull that functions as a catamaran when light and as a high capacity load carrying barge when fully loaded, that is faster and more efficient than prior art.

It is a further object of this invention to provide a liftboat hull design that is less susceptible to damage from grounding or underwater debris than prior art because of prop position, and in the invention's optimum configuration a pitch dampening plate that extends under and protects the propellers. Also, the pads are positioned on the bottom of the hulls and are likely to absorb any impact without damage to the hull.

It is a further object of the invention to provide a liftboat hull with the leg towers incorporated directly into an integral box beam structure that forms the hull. The box beam construction is inherently stronger, simpler and safer than the “attached” legs typical of prior art. This design also allows for most of the length of the leg towers and all the jacking equipment to be below the deck where it is sheltered from saltwater corrosion and weathering.

It is a further object of this invention to provide a liftboat hull design that is capable of making relatively fast ocean passages on its own when the legs are cut and shortened to a length which lowers the vessels center of gravity sufficiently to bring its stability within accepted standards for passage making. It is further intended to provide a liftboat hull design that can easily utilize a conventional bow thruster, which is difficult and awkward to adopt to the standard barge sign of prior art. This and the wide spacing/leverage of the propellers on the invention's hybrid hull make the liftboat more maneuverable and safer to operate.

A further object of this invention is to provide a liftboat hull design that has the ability to leave space around the fully retracted pads to prevent compression damage to the hull from debris on the pad when it is pulled hard against the hull for travel, without creating unnecessary drag or leaving the pad loose and unsupported. The sloping sides of the pads the hybrid design is capable of utilizing also aid in the prevention of this type of damage by allowing debris to fall from the tops of the pads more readily than the flat top pads typically utilized by prior art, whose “attached” leg towers and sponsons cannot easily accept the more efficient (when pulling free from the bottom), stronger (leg to pad attachment) pyramid shaped pads.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outboard profile of a typical liftboat as known in the prior art.

FIG. 2 is a bottom plan view of the inventive hybrid hull with pads retracted.

FIG. 2A is a perspective view of the inventive hybrid hull looking forward to aft with legs and pads extended.

FIG. 2B is a stern view of the starboard hull, shown without propellers or rudders.

FIG. 2C is a stern view of the port hull, shown with propellers but not rudders.

FIG. 3 is an outboard profile of a liftboat with the inventive hybrid hull with legs and pads extended.

FIG. 4 is an upper plan view of the box beam structure of the inventive hybrid hull.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts an outboard profile of a typical liftboat as currently known in the art. Shown is the hull 1, the legs 2, the pads 3, the jacking towers 4, sponsons 5, while the actual jacking system is not shown.

Referring to FIG. 1, the disadvantages of current liftboat design and construction are apparent. Construction of sponsons and overhangs is unnecessarily complicated and inherently weaker than an integrated design. Compound curve of stern rake is difficult to construct/repair. Having the keel coolers on inside of hull creates several problems including corrosion of piping and electrical wiring inside wet tanks and voids. Catch water in pockets can cause localized corrosion, creating the need to repair or cut out and replace sections in hard to reach places. This means down time and repair expenses compounded by damage done to the inside of the engine room trying to replace cooler under a generator set or engine. Internal coolers make it hard to clean and rinse the engine room deck. It also creates the necessity of building and maintaining a grating or walkway above the uneven surface (trip hazard). Jacking gear (planetaries, motors and hoses) are mounted on open deck and subject to damaging effects of saltwater and sun exposure. Leg support (leg tower/sponson) are “attached” to the hull instead of being a strong, integral part of the hull. Because of this basic design, liftboats have a long history of stress related damage and failures.

The stern of the liftboat depicted in FIG. 1 has a hydrodynamically “dirty” exit which causes drag by creating turbulence and pulling water behind the boat as the vessel makes way. Furthermore, the downward pointing propeller has an inefficient thrust line that can waste 10% or more of the vessel's applied power. In addition, the propeller, strut and rudder hang below keel and are more susceptible to damage than any other part of the hull from shallow water hazards and semi submerged debris. This is the most important and delicate part of hull. There is drag from sponson and water being pushed under the bow rake lifts the bow. Lift=drag (driving uphill all the time). Broad horizontally flat barge bow does not “split” the water and slide through it. The water is pushed under or ahead of the vessel. In addition, the retracted pad causes drag while underway. Flat top of pad is hard to extract from soil and picks up debris which causes damage to the hull as the pad is retracted and pulled against the bottom of the sponson.

All these detrimental features have been eliminated in the inventive hybrid hull. FIG. 2 shows a bottom plan view of the inventive hybrid hull 13 with pads 11 retracted into the starboard catamaran hull 6 and the port catamaran hull 9. The starboard catamaran hull 6 and the port catamaran hull 9 are joined by the center barge hull. At the stern 15 are shown a starboard stern bottom extension 8 and a port stern bottom extension 9. Also shown is the bow 6a and stern 6b of the starboard catamaran hull 6, as well as the bow 7a and stern 7b of the port catamaran hull 7.

FIG. 2A is a perspective view of the inventive hybrid hull 13 looking from bow 14 to stern 15 with legs 2 and pyramid pads 11 extended. The pad recesses 12 are shown on the bottom of the starboard catamaran hull 6 and the port catamaran hull 9. The raked bow portion 16 of the center barge hull 10 is also shown.

FIG. 2B shows a stern view of the stern 6b of the starboard catamaran hull 6, shown without propellers or rudders. Shown is the starboard bottom extension 8, and a portion of the center barge hull 10. FIG. 2C shows a stern view of the stern 7b of the port catamaran hull 7, shown with propellers 17 but without rudders. Also shown is the port bottom extension 9, and a portion of the center barge hull 10.

FIG. 3 is a starboard outboard profile of a liftboat with the inventive hybrid hull 13 with legs 2 and pyramid pads 11 extended. In FIG. 3, the pad recesses 12 are shown in phantom in the starboard catamaran hull 6. Also shown is a starboard engine 18 driving propellers 17 at the stern 6b of the starboard catamaran hull 6. It is understood that more than one set of propellers 17 and engines 18 may be used in the starboard catamaran hull 6 and port catamaran hull 7. Also shown is a thruster 19 in the bow 6a of the starboard catamaran hull 6. It is understood that a similar thruster 19 would be installed in the port catamaran hull 7.

FIG. 4 is an upper plan view of the inventive hybrid hull 13 with the main deck removed to show the box beam structure of the inventive hybrid hull 13 with openings 20 for the legs 2. As can be seen, the starboard catamaran hull 6 and the port catamaran hull 9 each form a box beam structure with a longitudinal inboard panel 21 and a longitudinal outboard panel 22, with cross panels 23. The bottom 24 of the center barge hull 10, and the bottoms 25 of the starboard catamaran hull 6 and the port catamaran hull 9 are also shown. It is understood that, while not shown, the main deck would form the top panel of the box beam structure.

Claims

1. A hybrid hull form for a liftboat vessel with jacking system, a plurality of jacking legs and pads, said hull form comprising a starboard catamaran hull with a bow, stern and stern bottom extension, a port catamaran hull with bow, stern and stern bottom extension, a center barge hull with a bow rake connecting said starboard catamaran hull and port catamaran hull.

2. The hybrid hull form of claim 1 wherein the starboard catamaran hull and the port catamaran hull each further comprise leg openings for the jacking legs and pad recesses for fully receiving the pads when the jacking legs are fully raised.

3. The hybrid hull form of claim 2 wherein the pads are configured in a pyramid shape with essentially flat bottoms.

4. The hybrid hull form of claim 3 wherein the starboard catamaran hull and the port catamaran hull are each fitted at the stern above the stern bottom extensions with at least one propeller driven by an engine.

5. The hybrid hull form of claim 4 wherein the starboard catamaran hull and the port catamaran hull are each fitted at the bow with at least one thruster.

6. The hybrid hull form of claim 1 wherein the starboard catamaran hull, the port catamaran hull and the center barge hull are of box beam construction.

7. The hybrid hull form of claim 6 wherein the starboard catamaran hull and the port catamaran hull each further comprise longitudinal inboard and outboard panels with cross panels.