GB2492582A

GB2492582A - Modular elongate superstructure

Info

Publication number: GB2492582A
Application number: GB1111588.8A
Authority: GB
Inventors: Ben Alexander Ramsay; Ian Anthony Gowens
Original assignee: Aker Offshore Partner Ltd
Current assignee: Aker Offshore Partner Ltd
Priority date: 2011-07-07
Filing date: 2011-07-07
Publication date: 2013-01-09
Anticipated expiration: 2031-07-07
Also published as: GB2492582B; GB201111588D0; GB2492582B8; GB2492582A8

Abstract

An elongate superstructure is installed on a boom by lowering from a helicopter a multiplicity of segments in succession and locating a segment as it is lowered by its engagement with a previously installed segment. Each segment may include at least one slotted part (14) for engagement over a cross-member (7) of the boom, a front end adapted to be located longitudinally by a preceding segment and a rear end adapted to locate longitudinally a succeeding segment.

Description

MODULAR PLATFORMS AND ASSEMBLY THEREOF

This invention relates to the installation and assembly of an elongate superstructure such as a platform or stairway on a boom which extends from an offshore installation S such as a drilling rig.

One example of such a boom is a flare boom which carries at its far end a flare tip at which gaseous hydrocarbons are burned. A flare boom generally extends for a substantial distance upwards and away from the rig so that the flare is located as far away as reasonably practical from workers on the rig. The boom is normally composed of a regular lattice work of steel pipes.

The construction of such a superstructure on a boom normally requires the presence of personnel on the boom for a substantial period. Usually the superstructure has to be assembled on site by those personnel and typically requires substantial scaffolding on the boom.

It is therefore the object of the invention to alleviate these disadvantages and possible dangers and in particular to allow the placement of modular prefabricated segments of the superstructure by helicopter.

Summary of the invention

In one aspect the invention provides a method of installing an elongate superstructure on 3 boom that extends from an offshore structure comprising lowering from a helicopter a multiplicity of prefabricated segments in succession and locating a segment as it is lowered by its engagement with a previously installed segment.

Preferably an installed segment provides at a rear end a datum for the location of a succeeding segment and the said succeeding segment rotates with respect to the datum into engagement with the boom.

In a specific example, each segment has a slotted part and the method includes engaging the slotted part over a respective cross-member of the boom.

The invention also provides a modular segment of a superstructure for installation on a boom, the segment being in elongate form and capable of forming a continuous structure with longitudinally adjacent segments, the segment including at least one slotted part for engagement over a cross-member of the boom, a front end adapted to be located longitudinally by a preceding segment and a rear end adapted to locate longitudinally a succeeding segment.

The segment may have a pair of jaws for securing the segment to the cross-member io Preferably the front end carries a transverse member and the rear end has at least one hook shaped for capturing and locating the corresponding transverse member of a succeeding segment. The segment may carry steps forming a stairway along the segment.

Introduction to the drawings

Figure 1 illustrates a flare boom on which a superstructure according to the invention has been assembled Figure 2 illustrates partly the method of installation according to the invention Figures 3 to 5 illustrate various parts of segment of a superstructure according to the invention in different phases of installation.

Figures illustrate part of a segment to a larger scale in different phases of assembly Figure 9 illustrates the attachment of one segment to another in greater detail.

In Figure 1 is shown a boom 1 which in this example is a flare boom comprising a repetitive lattice structure 2 that extends from a base frame 3 located on an offshore installation such as a drilling rig. Offshore' is not intended *to connote proximity to a shore; the installation may be a fixed or floating structure.

The boom 1 extends upwardly and away from the installation and has at its outer end a flare tip 4.

The latticework of the boom comprises side longitudinal members such as the member 5, uprights such as the upright 6, horizontal members 7 and various cross-ties. In this example these is a multiplicity of horizontal members 7 which are regularly spaced along the upper part of the boom 1.

In this example of the invention, as shown in Figure 1, a superstructure 8 extending along and on top of the boom has been installed. The superstructure 8 is in the form of a continuous stairway extending from the base frame 3 to a location close to the flare tip 4.

As will be discussed with reference to Figure 3 to 5, the superstructure 8 is composed of a multiplicity of similar prefabricated modular segments which a successively placed in position with the aid of a helicopter. Figure 2 shows the helicopter lowering by means of a winched line 10 a carrying frame which temporarily supports a segment 12 of the is superstructure 8.The segment 12 is lowered into position with its front end downwards until that front end engages the rear end of the immediately previously installed segment.

Figures 3 to 5 illustrate the construction of the segments and also the method of installation.

Figure 3 shows part of a segment 12 in position on the boom 1. Included in Figure 3 are a longitudinal side member 5 and a cross-beam 7 of the boom, one of the uprights 6 and a cross-tie 13. The segment carries a lug 14 which has a slot 15 which can fit over and around the cross-beam 7. The segment also has two clamping jaws 16 and 17 which are pivoted to the body of the segment 12 and can be held in an inactive or cocked state until the segment is properly located flat on the boom and then activated to clasp the cross-beam 7.

Figure 4 shows a subsequent segment 12a being lowered towards the boom on which the segment 12 is already in place. The segment 12a is similar to the segment 12. At the front end of the segment 12a is a pair of forwardly extending brackets 20 (only one being shown in the side view), which support a transverse bar 21.

The rear end of the segment 12 has at least one hook 22 (and possibly two laterally spaced hooks). In this example the hook extends from the underside of the segment rearwardly, and has a reception slot 23 in its upper edge. The bar 21 engages the slot 23 and is eventually arrested by the slot's inner end 24, which provides a datum for the placement of the segment I 2a. As the segment 1 2a is lowered further, it will rotate about the bar 21 until a slot in a lug corresponding to the lug 14 of the segment 12 engages a respective crossbeam (not shown) of the boom 1.

After the segment 1 2a is in position a clamping jaw 25 at the rear end of the segment 12 can be closed over the bar 21 to secure the segments 12 and 1 2a together.

Figure 6 illustrates part of a segment while the segment is being transported. The lug 14 of Figures 4 -6 is shown as being in two parts 14a and 14b, separated by a spreader beam 26, but embracing a cross-beam 7 as previously described. The jaws 16 and 17 are pivoted to the part 14a and 14b. The jaws each have a respective receiver in the form of a respective bush 27, 28.

While the segment is transported the clamping jaws may be held apart as shown in Figure 6 by cable ties 29 and 30 extending from the jaws around the body of the segment 12.

Figure 7 shows the securing of the segment 12 in position. An operating rod may be inserted into the bush 27 and rotated in the direction indicted by the arrow A to close the jaw 16 over the beam 7. Likewise an operating rod (not shown) may be inserted into the bush 28 and rotated in the opposite direction as shown by arrow B to close the jaw 17 onto the beam 7.

Figure 8 shows the segment 12 secured in position, both jaws 16 and 17 being closed onto the beam 7.

Figure 9 shows a modification of the device at the rear end of the segment 12 for receiving and locating the next segment 12a. The end part of the segment 12 has at least one side hook 32 (and preferable one on each side). The hook has an inlet ramp 33 on which the transverse bar 21 of the next segment lands. This is indicated by the quartered circle 21a. As the segment 12a is lowered the bar 21 will travel down the ramp 33 and the segment will rotate about the bar 21. The bar reaches a bend between the ramp 33 and a reverse ramp 34 and will come to rest and be located in a socket 35 at the end of the ramp 34. The datum position of the bar (21) in the socket 35 is shown by the reference number 21 b.

Claims

<claim-text>Claims 1. A method of installing an elongate superstructure on a boom that extends from an offshore structure comprising lowering from a helicopter a multiplicity of prefabricated segments in succession and locating a segment as it is lowered by its engagement with a previously installed segment.</claim-text> <claim-text>2. A method according to claim 1 in which an installed segment (12) provides at a rear end a datum (24) for the location of a succeeding segment and the said succeeding segment rotates with respect to the datum into engagement with the boom.</claim-text> <claim-text>3. A method according to claim I or 2 in which each segment has a slotted part (14) and the method includes engaging the slotted part over a respective cross-member (7) of the boom.</claim-text> <claim-text>4. A modular segment of a superstructure for installation on a boom, the segment (12) being in elongate form and capable of forming a continuous structure with longitudinally adjacent segments; the segment including at least one slotted part (14) for engagement over a cross-member (7) of the boom, a front end adapted to be located longitudinally by a preceding segment and a rear end adapted to locate longitudinally a succeeding segment.</claim-text> <claim-text>5. A modular segment according to claim 4 in which the segment has a pair of jaws (16, 17) for securing the segment to the cross-member (7).</claim-text> <claim-text>6. A modular segment according to claim 4 or claim 5 in which the front end carries a transverse member and the rear end has at least one hook shaped for capturing and locating the corresponding transverse member of a succeeding segment (12a).</claim-text> <claim-text>7. A modular segment according to any of claims 4 to 6 in which the segment (12) carries steps (18) forming a stairway along the segment.</claim-text>