Apparatus for providing access to equipment or structures that require maintenance

The present invention relates to an apparatus for providing access to equipment or structures that require maintenance. More particularly, the present invention is suitable to provide access to equipment or structures located offshore, such as wind turbines or structures for oil and gas production. The apparatus comprises a deck, an apparatus structure for supporting the deck, a platform and a platform support mechanism. The platform is movable with respect to the deck from a stowed position to an extended position. In the extended position the platform forms an extension to the deck. The platform support mechanism comprises at least one cable and at least one compression post. The/each cable has a cable first end attached to the platform at or adjacent to a platform leading edge and a cable second end attached to the platform at or adjacent to a platform trailing edge. The/each compression post supports the cable between the cable first end and the cable second end and is adapted to maintain a substantially constant tension in one of said cables as the platform moves from the stowed position to the extended position.

FIELD OF THE INVENTION

The present invention relates to an apparatus for providing access to an object to be maintained. Particularly, but not exclusively, the present invention relates to an apparatus for providing access to an object to be maintained in an offshore environment.

BACKGROUND TO THE INVENTION

Obtaining access to offshore structures such as wind turbines and oil and gas installations, to undertake, for example, servicing, maintenance or abandonment operations can be extremely hazardous. Often the vessel front which the servicing, maintenance or abandonment operation is to be performed, draws up alongside the offshore structure and the engineer steps or jumps onto the structure or man rides off the vessel to work on the structure. In the case of maintenance of a wind turbine, for example, the maintenance engineer steps or jumps onto a vertical ladder on the wind turbine base. However, if a repair is required to, for example, the wind turbine blades, this often requires a vessel with cranes to be brought into position to lift replacement blades to the required height and for the maintenance engineers to be suspended in harnesses to perform functions for removal of the defective blades and installation the new blades.

Furthermore, the equipment necessary for providing the servicing, maintenance or abandonment operations may require to be lifted onto the offshore structure. The transfer of the equipment represents a risk to the structure, personnel and environment.

This problem is further exacerbated when it comes to older offshore structures, particularly oil and gas structures which due to a prolonged spell in the maritime environment can no longer support the weight of the servicing or maintenance equipment that has been traditionally lifted onto, landed and supported by the structure.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an apparatus for providing access to an object to be maintained, the apparatus comprising:

a deck:

an apparatus structure for supporting the deck;

a platform, the platform being movable with respect to the deck from a stowed position to an extended position, in the extended position the platform forming an extension to the deck;

a platform support mechanism comprising at least one cable and at least one compression post; the/each cable having a cable first end attach to the platform at or adjacent to a platform leading edge and a cable second end attached to the platform at or adjacent to a platform trailing edge, the/each compression post supporting the cable between the cable first end and the cable second end, the/each compression post being adapted to maintain substantially constant tension in one of said cables as the platform moves from the stowed position to the extended position.

In at least one embodiment of the present invention, providing an apparatus which incorporates a platform support mechanism as described above, permits the at least part of the weight of the platform to be transferred to the apparatus structure independently of the deck, creating an apparatus which can be extended into the proximity of an object to be maintained permitting safe working and an effective means of transferring components to the required location adjacent to the object being maintained. The apparatus described provides access and permits operations to be conducted on offshore structures without landing weights on the structure. An apparatus in accordance with the least one embodiment of the present invention provides an independently supported platform around and/or over the offshore structure, providing safe access for personnel and equipment without exerting any weight on the structure.

The/each compression post may be adapted to at least partially transfer the weight of the platform to the apparatus structure.

The deck and the platform may be integral.

The deck may be adapted to at least partially support the platform. The deck and the platform support mechanism may cooperate to transfer the whole weight of the platform to the support structure.

The deck may define a recess adapted to receive part of the platform.

The deck recess may comprise a first deck recess and a second deck recess, the first and second deck recesses adapted to receive a first platform side edge and a second platform side edge respectively.

In moving from the stowed position to the extended position, the platform may be adapted to slide within the first and second deck recesses.

The apparatus may further comprise a sliding mechanism adapted to facilitate movement of the platform with respect to the deck.

The sliding mechanism may comprise first and second low friction slides, one said low friction slides being located in or adjacent to each deck recess.

The sliding mechanism may comprise at least one Hillman roller.

The platform may be movable with respect to the compression post.

The/each compression post may be adapted to vary in length to maintain a substantially constant tension in the cable as the platform moves from the stowed position to the extended position.

The/each cable may be fixed in length. That is, the cable does not lengthen or shorten as the platform moves from the stowed position to the extended position.

The/each compression post may comprise a body and a cable support. The cable support may be adapted to engage and support the cable and maximise distribution of load in the cable.

The cable support may be movable with respect to the body to maintain and distribute a substantially constant tension in the cable.

The cable support may comprise a low friction interface for engaging the cable such that the cable can move with respect to the compression post with friction minimised.

The cable support may comprise a sheave for engaging the cable.

The sheave may be a rolling sheave.

The/each compression post may comprise a jack, the jack being adapted to move the cable support with respect to the post body.

The jack may be a hydraulic jack.

The/each compression post may extend or contract by movement of the cable support with respect to the compression post body to maintain a constant tension within the/each cable as the platform moves between the stowed and extended configurations.

The/each compression post may extend or contract automatically.

The jack may be adapted to extend or contract the compression post automatically to maintain the tension in the cable as the compression post moves with respect to the cable.

The/each compression post may be mounted to the deck.

The/each compression post may be movable with respect to the deck. In particular embodiments, the compression post may be movable to a position in which transfer of the weight of the platform to the apparatus structure is best facilitated.

The/each compression post may be adapted to tilt with respect to the deck.

The/each compression post and the deck may define an angle therebetween.

The/each compression post may be movable with respect to the deck such that the angle is variable. As the platform moves to the extended configuration, the compression post may tilt away from the platform leading edge to maintain a direct compression of the post by the cable.

The deck may be adapted to move with respect to the apparatus structure.

The apparatus structure may comprise one or more legs.

The/each compression post may be adapted to transfer the weight of the platform to at least one of said legs.

The/each compression post may further comprise a guide, the guide being adapted to engage with the apparatus structure.

The guide may be adapted to transfer the weight experienced by the compression post to which it is attached to the apparatus structure

The cable first end may be attached to the platform at a first distance from the platform leading edge and the cable second end may be attached to the platform at a second distance from the platform trailing edge, the first distance and the second distance being the same.

In this embodiment, when the compression post is equally spaced from the cable first end and the cable second end, and the compression post is vertical, the platform is in balance.

The apparatus may be adapted to be used at sea.

The apparatus structure may be adapted to float.

The apparatus structure may comprise a hull.

The deck may be releasably attachable to the hull.

The deck may be adapted to move with respect to the hull.

The deck may be adapted to be elevated with respect to the hull to a working height.

The deck may be jacked up the legs, away from the hull. Such a arrangement permits the deck to be elevated with respect the hull to the working height to permit maintenance or servicing operations to be performed.

In alternative embodiments, the apparatus may be adapted to be used on land.

According to a second aspect of the present invention there is provided apparatus for providing access to an object to be maintained, the apparatus comprising:

a deck;

an apparatus structure for supporting the deck;

a platform, the platform being movable with respect to the deck from stowed position to an extended position, in the extended position the platform forming an extension to the deck;

a platform support mechanism adapted to at least partially transfer the weight of the platform in the extended position to the apparatus structure.

According to a third aspect of the present invention there is provided an apparatus for providing access to an object to be maintained, the apparatus comprising:

a platform;

an apparatus structure for supporting the platform, the platform being movable with respect to the apparatus structure from a stowed position to an extended position, in the extended position the platform forming an extension to the apparatus structure;

a platform support mechanism comprising at least one cable and at least one compression post; the cable having a cable first end attached to the platform at or adjacent a platform leading edge and a cable second end attached to the platform at or adjacent to a platform trailing edge, the compression post supporting the cable between the cable first end and the cable second end, the compression post being adapted to maintain substantially constant tension in the cable as the platform moves from the stowed position to the extended position.

According to a fourth aspect of the present invention there is provided an apparatus for providing access to an object to be maintained, the apparatus comprising:

a deck;

an apparatus structure for supporting the deck;

a platform, the platform being movable with respect to the deck from a stowed position to an extended position, in the extended position the platform forming an extension to the deck;

wherein the weight of the platform is transferred to the apparatus structure through the deck and through a platform support mechanism attached to the apparatus structure.

It will be understood that features listed as preferred respect to the first embodiment may be equally applicable to subsequent embodiments and are not repeated for brevity.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made toFIG. 1, a schematic side view of an apparatus, generally indicated by reference numeral10, for providing access to an object to be serviced, maintained or abandoned, in this case an offshore structure12incorporating a wellhead24, in accordance with an embodiment of the present invention.

The apparatus10is a jack-up vessel14comprising a deck22(shown in broken outline) and an apparatus structure30, the apparatus structure30comprising a hull16and four legs18. In operation, the legs18are generally resting on the sea bed.

The deck22is normally attached to the hull16, however in order to perform maintenance operations at elevated heights, the deck22can be detached from the hull16and moved to an elevated position adjacent to the wellhead24, shown inFIG. 2. The deck22is elevated by travelling up the legs18from the level of the hull16(shown inFIG. 1) to the elevated position adjacent the wellhead24(shown inFIG. 2). The provision of an elevated deck22allows the operators to be raised to the level of the wellhead24and permits machinery and replacement parts, for example, to be positioned adjacent the wellhead. Reference is made to International Patent Publication WO 2012/163635, the contents of which are incorporated by reference.

As can be seen fromFIG. 2, however, there is still a substantial gap between the elevated deck22and the wellhead24. To bridge this gap, the vessel14is provided with a platform26, the platform26being movable in a plane parallel to the plane of the deck22using hydraulic rams (not shown) from a stowed position, shown inFIG. 2to a partially extended position, shown inFIG. 3; a schematic side view of the apparatus10ofFIG. 2with the platform26in a partially extended position and, ultimately, to a fully extended position shown and discussed in due course in connection withFIG. 5.

As can be seen fromFIG. 3, the platform26is extended into the proximity of the wellhead24allowing safe access to the wellhead24for servicing, maintenance or abandonment. Once the wellhead24is accessible from the platform26machinery, tools and equipment resting on the platform26can be moved, located or erected on or over the offshore structure12or wellhead24, facilitating the maintenance, servicing or abandonment task without the need for placing weight on the offshore structure or with a reduced need of operations such as manriding.

Referring toFIG. 2andFIG. 3, the apparatus10further includes a first platform support mechanism28and a second platform support mechanism32(shown and discussed in connection withFIG. 5) for transferring the weight of the platform26to the apparatus structure30. The first and second platform support mechanisms28,32are located on either side of the platform26.

Taking the first platform support mechanism28as exemplary of both mechanisms28,32, the mechanism28comprises a cable34and a compression post36. The cable34has a first end38attached to a platform leading edge42and a second end40attached to a platform trailing edge44. This arrangement means that the cable34travels with the platform26as it moves between the stowed and extended positions.

During this travel, tension is maintained in the cable34by a compression post36. The compression post36at least partially transfers the weight of the platform26, via the cable34to the front left leg18A of the apparatus structure30.

The compression post36can be more clearly seen inFIG. 4; a schematic side view of the first platform support mechanism28of the apparatus10ofFIG. 1. The compression post36comprises a running sheave46connected to a post body48by a hydraulic jack50. The running sheave46is adapted to provide a substantially frictionless retainer for the cable34to run through. The hydraulic jack50is provided to increase and decrease the length oaf the compression post36as the platform26moves between the stowed and extended positions. The change in length of the compression post36is required to maintain a constant tension in the cable34by taking up any “slack” or releasing over tension caused by “stretching” of the cable34as the platform26moves.

Reference is now made toFIG. 5; a schematic end view of the deck22, platform26and the first and second platform support mechanisms28,32of the apparatus10ofFIG. 1.

The second platform support mechanism32is visible in this Figure, the second platform support mechanism32comprising a second compression post52and a second cable54.

Also visible on this Figure are the attachment mechanisms56,58which the first and second compression posts36,52use to transfer the weight of the platform26to the apparatus structure30and the first and second apparatus structure legs18A,18B in particular.

The support mechanisms28,32are not the sole method of supporting the weight of the platform26. As can also be seen fromFIG. 5, the platform26is located within recesses60,62defined by the deck22. These recesses incorporate low friction slides (not shown) which assist in supporting the weight of the platform26. In particular, the low friction slides are Hillman rollers, mounted above and below the platform26to sandwich each edge of the platform26.

In the partially extended state shown inFIG. 4, the weight of the platform26is mostly taken by the deck22. In this position, the compression post36is midway between the platform leading edge42and the platform trailing edge44and compression post26bisects the cable34. The compression post36acts as a fulcrum and transfers the unsupported weight of the platform26to the vessel leg18A. As the compression post36bisects the cable34, the platform26is balanced about the compression post36when the compression post36is in a vertical position and the hydraulic jack takes up any slack in the cable34to ensure direct compression of the post36by the cable34.

Reference is now made toFIG. 6, a schematic side view of the first platform support mechanism28of the apparatus10ofFIG. 1in the fully extended position.

In some embodiments, it may be necessary to extend the platform26to its maximum extent, shown inFIG. 6. In this position, much more of the weight of the platform26is taken by the platform support mechanism28. As can be seen fromFIG. 6, the compression post36does not move with the platform to keep the platform26in balance about the compression post36and to ensure direct compression of the post36by the cable34, the post36is adapted to tilt with respect to the deck22and the platform26such that the platform is balanced between them. During this process, the change in angle with respect to the deck22of the cable34means that the compression post36must be shortened by retracting the hydraulic jack50.

Finally, reference is made toFIG. 7, a schematic top view of part of the apparatus ofFIG. 1. In this Figure, the deck22is shown along with the four supporting legs18A-18D. Also visible as the platform26shown in dashed outline in the partially extended position26A and in dotted outline in the fully extended position26B. The deck22defines and aperture60which the platform26fully occupies in the stowed configuration. As the platform26moves from the stowed to the fully extended configuration, the aperture60opens up revealing a void66. This void66is filled with panels62, of which two are shown, the panels62unfolding automatically to fill the void66. This assist in overcoming the safety hazard of an opening on the deck22.

However, in certain circumstances, an opening on the deck would be useful for lowering or raising equipment, tools or parts for a servicing or maintenance operation from the hull16up to the deck22for subsequent positioning on the platform26to allow the equipment, tools or parts to be positioned adjacent the worksite.

In this embodiment, an opening64in the deck22, known as a moonpool is provided for this purpose. A crane (not shown) mounted to the deck22can be utilised to raise and lower tools and equipment through the moonpool64between the deck22or platform26and the hull16below.

Various modifications and improvements may be made to the above described embodiment without departing from the scope of the invention. For example, although the offshore structure12is described as an oil and gas platform, will be understood that the apparatus10can be used to perform maintenance, servicing or abandonment operations on any offshore structure including but not limited to renewable energy generation equipment such as wind turbines.

Additionally, the provision of the void66and the moonpool64allows for operations to be performed beneath the surface of the water adjacent or below the apparatus, such as repairs or maintenance of subsea wellheads or subsea manifolds in water depths at which the legs18can engage the seabed.