Fast jack liftboat jacking system

Abstract

An improved jacking system for a liftboat with a high speed manifold system with high speed motors and high speed planetary gear drives, a heavy lift manifold system with heavy lift motors and heavy lift planetary gear drives, and bypass valves for diverting hydraulic pressure between the high speed manifold system and the heavy lift manifold system. The improved jacking system makes the boat easier to position precisely and expands the weather and sea condition envelope the liftboat can operate in by reducing its exposure to multiple impact stresses while jacking up in rough sea conditions. The improved jacking system also serves as a safety device which can quickly “tag” the bottom to stop and stabilize the liftboat's motion in a close situation.

Description

This application claims priority from U. S. Provisional application Ser. No. 61/201,115 (“the '115 application”) filed Dec. 06, 2008. The '115 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 jacking system which allows the liftboat to operate more safely and reduces the multiple impact stresses the vessel absorbs while operating in rough conditions.

BACKGROUND

In the shallow coastal waters of the Gulf of Mexico the oil industry has numerous small platforms that 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 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 stem 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. FIG. 1 depicts an example of a current liftboat.

However, while the liftboat can operate in rough conditions once it is jacked up and has effectively become a platform, getting on location and jacking the vessel up in rough conditions is a different story. The liftboat's limitations are well known in the industry. Most operations manuals for the boats call for a limit of 4 to 5 foot seas to be able to change modes from floating operations to being jacked up out of the water. Part of the problem is the stress endured as the slow moving legs are lowered to the bottom and the wave action lifts and lowers the vessel in relation to the seabed while the legs start to come in contact with the seabed. If a vessels' legs operate at a typical 6 to 8 feet per minute and the wave period is between 6 to 10 seconds, the vessel is going to be lifted and dropped into the bottom several times before you can get your hull free of the water. You can imagine the stresses caused by hundreds of tons of steel being lifted and dropped. How serious this is largely depends on the consistency of the bottom and of course the wave height. If the bottom is soft mud it will cushion your impact but if it is hard clay or sand there are tremendous stresses imparted to the vessel and jacking system.

SUMMARY OF THE INVENTION

The design objective of this invention is to increase the legs' speed of descent to reduce the number and severity of impacts the vessel has to absorb between the moment of first contact with the seabed by the pads at the bottom of the legs and when the hull is jacking free of the effective action of the waves, whenever the vessel is being positioned on a work location. Most jacking systems are run by hydraulic motors through a planetary gear system that turns a pinion gear that drives a rack attached to the leg. The jacking speed of the vessel's legs is low because of the large gear reduction necessary for the planetary drives to lift the huge load of the vessel and all its cargo out of the water. This kind of force is not necessary when lowering the legs. In fact, up to the point where the legs' displacement equals the legs' weight and it becomes buoyant the pinions, planetary drives and motors are acting more as brakes than drives. A trade can occur here and motors are acting more as brakes than drives. A trade can occur here between force and speed. It is possible to use valves and clutches to disconnect and block the hydraulic flow to one or more of the multiple motor/planetary sets (typically six or more) which drive each leg. This would channel the entire flow of hydraulic fluid through fewer motor/planetary sets which would increase the velocity of the flow and the speed of the motors. See FIG. 2 for a diagram of its operation. The valves and clutches could be operated remotely and/or by a pressure switch which would automatically re-engage the disconnected motor/planetary sets when the pressure in the jacking system increases as the vessel is starting to lift free of the water an become heavier as it loses its buoyancy. But, you can only force so much fluid into and speed out of a hydraulic motor before reaching its capacity.

This invention involves using one or more extra motor/planetary sets per leg that have a high speed gear ratio. These extra motor/planetaries would have their own separate manifold system which would be tied into the main system with bypass valves. This would form two separate system that would switch between lowing the leg at high speed until the vessel starts to rise from the water and the pressure in the jacking system increases, then the heavy lifting system would take over to raise the vessel free of the water and allow it to jack up to its working level. Each system would use clutches between the motor and planetary. This would allow the planetary to spin freely when the alternate system was driving the leg, i.e., the manifold of the high speed system would be blocked and hydraulic fluid flow redirected to the heavy lift manifold using two separate valves or a single three way diverter valve and the planetary gear of the high speed system would be disconnected from its motor with a clutch that would allow it to turn freely and not bind the leg when the heavy lift system was operating. The heavy lift system would do the same to allow the operation of the high speed system. See FIG. 2 for a diagram of its operation.

Not only would the invention minimize the vessels exposure to damage while jacking in rough seas, it would also make it easier to “tag” the seabed with the pads and stop the vessel in a precise position in conditions such as waves and current that make the vessel hard to hold in place while waiting for the legs to lower.

Liftboats are very susceptible to the effects of wind and current due to their large signature, both above and below the water caused by their long legs. The invention could double as a safety devise by serving as “emergency brakes.” In a situation where the vessel was being swept by a side current or swell into a platform or rig while positioning or trying to pull away from a location it would be possible to “tag” the seabed and stop quickly. This is a familiar and credible scenario to those involved in liftboat operations. This invention could be retrofitted to an existing jacking system to enhance its operational capabilities without compromising its strength. A liftboat which incorporated this system would have fewer stress related structural problems and could operate in higher sea states without damaging the vessel. This invention would be a welcome addition to an industry that predictably suffers from stress related maintenance problems and accidents, especially as the vessels get larger. In addition, the invention could help expand the narrow liftboat operational limitations which adversely affect the industry.

It is an object of this invention to provide an improved jacking system that expands the weather and sea condition envelope the liftboat can operate in by reducing its exposure to multiple impact stresses while jacking up in rough sea conditions.

It is a further object of this invention to provide an improved jacking system that makes the liftboat easier to position precisely.

It is a further object of this invention to provide an improved jacking system that is a safety device which can quickly “tag” the bottom to stop and stabilize the liftboat's motion in a close situation.

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 schematic drawing of the inventive jacking system.

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, while the actual jacking system is not shown.

FIG. 2 shows a schematic for the inventive jacking system 5 for mounting on each leg 2 of the liftboat, with a high speed manifold system 6 hydraulically connected by high speed hydraulic hoses 6a to one or more high speed motors 7 each connected by a clutch to high speed planetary gear drives 8, a heavy lift manifold system 9 hydraulically connected by heavy lift hydraulic hoses 9a to a plurality of heavy lift motors 10 each connected by a clutch to heavy lift planetary gear drives 11. Also shown are bypass valves 12 to divert high pressure hydraulic fluid from the high pressure hydraulic pump system 13 from the heavy lift manifold 9 to the high speed manifold 6 and vice-versa.

While not depicted, it is understood that the inventive jacking system 5 is mounted on each leg 2 of the liftboat, each of which legs 2 are fitted with a rack engaged by pinions driven by the high speed planetary gear drives 8 and the heavy lift planetary gear drives 11.

The high speed planetary gear drives 8 would have a high speed gear ratio, with their own separate manifold system 6 which would be tied into the main system 13 with bypass valves 12. This would form two separate systems that would switch between lowing the leg 2 at high speed until the vessel starts to rise from the water and the pressure in the jacking system increases, then the heavy lifting system 9 would take over to raise the vessel free of the water and allow it to jack up to its working level. Each system would use clutches between the motor and planetary gear drives. This would allow the planetary gear drives to spin freely when the alternate system was driving the leg, i.e., the manifold of the high speed system 6 would be blocked and hydraulic fluid flow redirected to the heavy lift manifold system 9 using two separate valves or a single three way diverter valve 12 and the planetary gear drives 8 of the high speed system would be disconnected from its motor 7 with a clutch that would allow it to turn freely and not bind the leg when the heavy lift system was operating. The heavy lift system would do the same to allow the operation of the high speed system.

It also intended that the valves 12 and clutches connecting the high speed motors 7 and the high speed planetary gear drives 8, as well as the heavy lift motors 10 to the heavy lift planetary gear drives 11 could be operated remotely. Likewise, the valves and clutches can be operated by pressure switch set to automatically engage or disengage. For example, a pressure switch would automatically re-engage the disconnected motor/planetary sets when the pressure in the jacking system increases as the vessel is starting to lift free of the water and become heavier as it loses its buoyancy.

Claims

1. An improved jacking system for a liftboat comprising a high speed manifold system with high speed motors and high speed planetary gear drives, a heavy lift manifold system with heavy lift motors and heavy lift planetary gear drives, and bypass valves for diverting hydraulic pressure between the high speed manifold system and the heavy lift manifold system.

2. The jacking system of claim 1 further comprising clutches between the high speed motors and high speed planetary gear drives and between the heavy lift motors and heavy lift planetary gear drives.

3. The jacking system of claim 2 further comprising remote controls for the high speed manifold system and heavy lift manifold system.

4. The jacking system of claim 3 wherein the remote controls further comprise remote controls for the high speed motors, the high speed planetary gear drives and clutches, the heavy lift motors and heavy lift planetary gear drives and clutches, and the bypass valves.

5. The jacking system of claim 3 further comprising pressure switch controls.