Maritime transfer system

The maritime transfer system is for crewmember safety when transferring to and from a vessel to a small oil or gas production platform that otherwise has only a swing rope for transfer. The system includes a platform extension permanently affixed to the platform, and a motor and winch installed on the extension. The motor and winch operate a cable that extends to a davit, the davit and cable suspending a car or gondola therefrom. Control is provided by a remote control switch installed on the distal end of a freely suspended control cable. In this manner, the car may be raised to the platform when not in use, the control hanging from the control cable for access from the crew vessel when needed. The crewmember may then carry the control with him or her in the car as it is raised and lowered to and from the platform.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to hoists, lifts, and the like, and particularly to a maritime transfer system for transferring personnel and/or equipment to and from a crew boat or vessel and an offshore gas or oil production platform.

2. Description of the Related Art

Offshore or maritime oil and gas drilling and production platforms have expanded nearly worldwide, as oil and gas deposits have been discovered beneath the sea floor in most areas of the world. The construction and maintenance of these platforms have necessitated the transfer of crews and equipment back and forth from land bases to the offshore platforms. This transfer process can be relatively complex, since travel must be accomplished from a stable land base to a platform at sea, and the platform is generally elevated at some distance above the water level.

Larger platforms used for drilling are generally sufficiently large as to require a full time crew and are usually equipped with a helicopter landing pad for the transfer of crews and certain equipment. These large platforms may have some means of accommodating supply boats and ships as well, and additional accommodations to facilitate the physical transfer of personnel to and from the supply boat or ship.

However, there are many quite small offshore platforms that are equipped only for oil or gas production. Many of these platforms have little more than a wellhead and a small surrounding platform, as they are completely automated and require only periodic visits by a crewman for maintenance or inspection, etc. These “normally unmanned installations” (NUT) are not typically of sufficient size to accommodate a helicopter, so that crew members are delivered to and from the site only by a relatively small crew supply boat. As a result, the means for transferring from the boat to the platform and back to the boat is generally primitive, at best. The general means of transfer is by a single rope. The crewman grabs a rope suspended from the platform and swings from the boat to the platform. Clearly, this is potentially hazardous due to motion of the boat relative to the fixed platform from wave action, wind, and/or other forces. There have been instances of serious injury to crewmembers when the crew boat was pushed against the platform structure, where no more than a swing rope was provided for transfer.

Thus, a maritime transfer system solving the aforementioned problems is desired.

SUMMARY OF THE INVENTION

The maritime transfer system provides an economical and easily retrofitted assembly to facilitate the safe transfer of personnel and/or equipment to a small oil or gas production platform from a supply or crew boat, or other vessel. The transfer system includes a platform extension that is added (e.g., welded, bolted, etc.) to the existing platform. Nearly all necessary transfer equipment is located on the extension. The extension serves to position all electrical equipment at a predetermined distance (e.g., ten feet) from the wellhead on the platform in order to comply with regulations.

A prime mover, preferably an electric motor and winch, are installed on the extension. The winch controls a cable used to lift and lower a car or gondola. An overhead davit extends outward from the platform and beyond the extension. The cable runs up to the davit to support the car therefrom. Preferably, the cable passes through a double pulley and sheave assembly above the car, the lateral spacing of the pulleys providing additional stability for the car. Solar cells are provided to charge an electrical storage battery or batteries during periods of non-use of the system.

Control of the motor is provided by a remote switch that is connected to the free end of a flexible cable extending from the motor assembly. The control switch is not physically secured to any of the structure, other than to the distal or free end of the control cable. This permits the control switch to be positioned within or outside of the car, as required. Normally, the car is raised to the level of the platform when the platform is unattended in order to lift it clear of wave action and potential damage. However, the control switch is left hanging from its cable, only a short distance above the water level.

When personnel need to transfer to the platform, the crewmember may easily reach the hanging control switch from the boat or vessel to lower the car. When the car has been lowered to the boat, the crewmember can climb into the car while carrying the control with him or her into the car. The crewmember then uses the control to lift the car to the level of the platform, or more particularly, to the platform extension. The operation is reversed when the crewmember departs the platform. In this manner only a single switch box is required to carry out all control operations, rather than requiring multiple interrelated switches in parallel and installed in various locations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The maritime transfer system provides a quickly installed and economical means for greatly increasing the safety of workers visiting smaller offshore oil and gas production platforms that are otherwise ordinarily equipped with only a swing rope for access. Such smaller production platforms generally have only a wellhead installed thereon, and do not have the size or facilities for a helicopter landing pad or for conveniently mooring a boat or other vessel thereto. The maritime transfer system greatly reduces, if not eliminates, the chance of injury to a crewmember during the process of transferring from a crew boat or supply vessel to the platform, and from the platform back to the boat or vessel.

FIG. 1of the drawings provides an environmental perspective view of an exemplary transfer system10, wherein a crew boat or supply vessel V is stationed at the production platform P.FIG. 2is a side elevation view of the production platform P with the maritime transfer system10extending therefrom. It should be noted that the safety rail about the perimeter of the platform P and transfer system is not shown inFIG. 2for clarity in the drawing. The maritime transfer system10includes a platform extension12that is permanently affixed (e.g., welded, bolted, etc.) to the periphery or outer edge E of the platform P, preferably coplanar therewith.

A motorized winch and electrical storage battery assembly14is installed on the platform extension12to provide power for cable actuation, as explained further below. The winch may be powered by any suitable prime mover, but is preferably powered by an electric motor in combination therewith. The battery may be a conventional electrical storage battery (e.g., gel cell, or other suitable type), which receives power for recharging from one or more photovoltaic panels16installed at some suitable location with the transfer system10that communicate electrically with the battery in a conventional manner.

The motor, winch, and battery assembly14is preferably positioned near the outer edge of the platform extension12, as shown inFIGS. 1 and 2, in order to separate them from the wellhead W by some distance D, as shown inFIG. 2of the drawings. The platform extension12and the installation of the motorized winch and battery assembly14thereon place the maritime transfer system10in compliance with certain regulations for such equipment, which may require the equipment to be a certain minimum distance (e.g., ten feet) from the wellhead W.

A davit18is installed on the production platform P. The davit18has an elevated horizontal boom or arm20having a medial portion22extending over the platform extension12and a distal end24extending beyond the platform extension. The photovoltaic panels16may be installed along the boom20of the davit18, or to some other suitable structure. A car suspension cable26extends from the winch assembly14up to and over a first or davit pulley28suspended beneath the medial portion22of the boom or arm20. The distal end of the cable26is anchored or affixed to an attachment point30at the distal end24of the boom20.

A crew and/or equipment transfer car or gondola32is suspended from the cable26. The car32preferably comprises a rigid structure for protection of personnel therein while in use. At least the lower portion34of the car32is enclosed, although other car configurations may be used. The superstructure of the car32includes a double pulley bracket or housing36having laterally spaced first and second pulleys38aand38b(shown in broken lines inFIG. 2) installed therein. The double pulley housing36provides additional stability for the car32, reducing swaying of the car as it is suspended from the cable26. The car suspension cable26extends downward from the davit pulley28to pass beneath the two pulleys38aand38bat the top of the car32. Thus, as the winch assembly14draws the cable26in, the portion of the cable26extending from the davit boom20between the cable anchor point30and the davit pulley28is shortened, thereby lifting the car32upward. Paying out the cable26from the winch assembly14allows the portion of the cable26between the anchor point30and the davit pulley28to lengthen, thereby allowing the car32to descend.

Control of the lifting and lowering of the car32is accomplished by a control switch40, which is housed in a weatherproof switch box. The control switch40is a conventional double-throw switch, enabling the motor of the winch assembly14to operate in one direction to draw the cable26in and raise the car32, and to operate in the opposite direction to pay out the cable26to allow the car32to descend. Alternatively, other electrical switch arrangements may be used, e.g., two separate switches to operate the motor in opposite directions, etc. A conventional safety brake mechanism may be provided with the winch assembly14. Additional safety may be provided by an emergency ladder42for deployment by personnel in the car32in the event of loss of power, e.g., a rope ladder or other suitably compact ladder or the like when folded. The emergency ladder42is shown in its stowed and folded configuration in broken lines in the floor of the car32of the upper position inFIG. 2, the ladder42being shown deployed in broken lines from the lower car position inFIG. 2. A freely suspended, flexible control switch cable44extends from the motorized winch assembly14, the switch box and switch40being installed upon the free distal end46of the cable44.

The platform P is normally unattended, as noted further above. In this situation, the car32is raised to a normally stowed position adjacent the platform extension12, as shown inFIG. 1and in solid lines inFIG. 2. However, the control switch40in its switch box is left suspended by the control switch cable44, where it is accessible from a vessel V on the surface of the water, generally as shown inFIG. 1of the drawings. When a vessel V delivers a crewmember to the production platform P, the crewmember takes the switch box and actuates the switch40to lower the car32to the level of the vessel V. The crewman then enters the car32and carries the switch box with him or her, enabling the crewmember to control the position of the car32at all times. The car32is raised to the level of the platform extension12, allowing the crewmember to exit the car onto the extension and platform P to accomplish the desired inspection, maintenance, or other duties.

When the crewmember wishes to leave the platform P, he or she enters the car23from the platform extension12and uses the control switch40to lower the car32back to the level of the crew or supply vessel V. The crewmember exits the car32onto the vessel V, and retains the switch40on the end of its control cable44to raise the car32back to its normally stowed position at the level of the platform P and extension12, where it is clear of the water surface and potentially damaging wave action or other effects.