GB2261007A - Marine structure repair caisson - Google Patents
Marine structure repair caisson Download PDFInfo
- Publication number
- GB2261007A GB2261007A GB9123158A GB9123158A GB2261007A GB 2261007 A GB2261007 A GB 2261007A GB 9123158 A GB9123158 A GB 9123158A GB 9123158 A GB9123158 A GB 9123158A GB 2261007 A GB2261007 A GB 2261007A
- Authority
- GB
- United Kingdom
- Prior art keywords
- caisson
- marine structure
- structure repair
- vessel
- panels
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 241000239290 Araneae Species 0.000 claims description 20
- 238000012423 maintenance Methods 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000013011 mating Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63C—LAUNCHING, HAULING-OUT, OR DRY-DOCKING OF VESSELS; LIFE-SAVING IN WATER; EQUIPMENT FOR DWELLING OR WORKING UNDER WATER; MEANS FOR SALVAGING OR SEARCHING FOR UNDERWATER OBJECTS
- B63C11/00—Equipment for dwelling or working underwater; Means for searching for underwater objects
- B63C11/34—Diving chambers with mechanical link, e.g. cable, to a base
- B63C11/36—Diving chambers with mechanical link, e.g. cable, to a base of closed type
- B63C11/40—Diving chambers with mechanical link, e.g. cable, to a base of closed type adapted to specific work
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Earth Drilling (AREA)
Abstract
A marine structure repair caisson 3 is characterised in that it is adapted to be mountable to a multi-planar node region of a marine structure support member or conduit eg an oil rig leg or struts 1, 2, the caisson vessel comprising a plurality (three or more) of longitudinal segments. The marine structure repair caisson suitably comprises a plurality of longitudinal segments, each of which is formed as a planar panel folded about the longitudinal axis. <IMAGE>
Description
MARINE STRUCTURE REPAIR CAISSON
Field of the Invention
The present invention relates to caissons for enabling maintenance work on those parts of marine structures, such as oil and gas rig legs and risers, within the splash zone.
Field of the Invention
The vulnerability of the structures exposed within the splash zone, which extends approximately five metres above and below sea water level, is a weTh known foh7em in the off-shore oil and gas industries.
This zone of a leg or riser is not only subject to heavy weathering but is extremely difficult to access for maintenance. The swell is such as to deter boats and divers from approaching. To overcome this problem specialised caissons have been developed to encase that zone of the leg or riser to be repaired or cleaned, providing a chamber within which maintenance crew may operate un-affected by the surrounding swell.
Prior art maine structure repair caissons, which may alternatively be desclibed as marine structure repair habitats, are exemp7ified by
PCT W086/06121 which describes a cylindlical chamber having a watertight floor and an open access top assemhled from two longitudinal portions camped together and camped to the oil rig leg or riser. This apparatus, in common with other known caissons for this purpose, is, however, awkward to transport and essentially unsuitable for use on the many nodal reBImS of the legs or risers of an oil or gas rig, and pacarty so where the nodes branch in several panes.
Sum mary of the Invention According to a first aspect of the present invention there is provided a marine structure repair caisson, characterised in that it is adapted to be mountatZe to a multi-planer node zion of a marine structure support member or conduit, the caisson vessel comprising a plurality (three or more) of longitudinal segments.
According to a second aspect of the present invention there is provided a marine structure repair caisson which comprises a plurality of longitudinal segments, each of which is formed as a pZanar panel folded about the longitudinal a7as. These panels replace the conventional pair of semi-cylindrical segments of the conventional caisson vessel and provide for a number of advantages as will be detailed later.
Preferably each panel is folded midway between its longitudinal edges and is further provided with a perpendicularly outwardly, in use extending flange along each longitudinal edge.
Preferably each panel has an internal fold angle of 120 or 135, as is appropriate when six or eight panels, respectively, are used to form the vessel.
The caisson prefeSily further comprises an upper spider and a lower spider to rigidly support the assembled vessel respectively at the top and bottom thereof, in use.
Preferably said lower spider has an integral annular platform setting as a water-tight floor to the caisson in use.
Preferably the caisson yet further comprises upper and lower adjustable location collars to adjust the position of the upper and lower Spiders respectively, enabling the position of each spider mounted to the marine structure member, in use, to be adjusted independently of the other.
Brief Descwtion of the Drawings
A preferred embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings, wheres:
Figure 1 is an elevation of a typical oil rig leg jacket node;
Figure 2 is a plan view of the node of Figure 1;
Figure 3 is an elevation of the node of Figure 1 turned clockwise through 90 0and illustrating the caisson of the invention in place;
Figure 4 is a plan view of the node and caisson of Figure 3;
Figure 5 is a longitudinal sectional view of the node and caissons of
Figure 3;
Figure 6 is transverse sectional view taken along the line VI-VI in
Figure 5;;
Figures 7 and 8 are elevation views of upper and lower spiders, respectively, fieted to the oil rig leg;
Figure 9 is a vertical sectional view of one of the longitudinal panels of the caisson of Figure 4;
Figure 10 is a longitudinal sectional view taken along the line X-X in
Figure 4;
Figure 11 is vertical sectional view taken along the line XI-XI in
Figure 10;
Figure 12 is a detailled view of an anti-buoyancy collar; and
Figure 13 is a plan view of the antibucyancy collar of Figure 12.
Description of the preferred Embodiment
Referring to Figure 1 there is shown an oil rig leg jacket node comprising an oil rig leg 1 extending vertically downwardly into the sea (high tide level indicated by initial L. A. T), with five struts 2a-e branching from the leg 1 below the high tide level and within the sash zone. Three of the struts 2a - c project from the leg 1 substantially horizontally and in three different vertical planes, while the other two struts 2d, 2e each hisect the ninety degree angle between respective ones of the outer two horizontal struts 2a, 2b.To enable maintenance of the splash zone of the leg 1 a caisson needs b be constructed which will accommodate all five struts.
Referring now to Figures 3 and 4, a caissons 3 is illustrated mounted to the leg 1 and encompassing the joints of the struts 2 to the leg 1.
The caisson 3 comprises a chamber of octagonal vertical section. The chamber is formed of eight longitudinally extending folded planar panels' 4 each panel having been longitudinally folded about its mid- line to glove an internal fold angle of 135. A single such panel 4 is iLZustz:ated in Figure 9. Adjacent ones of the panels 4 are secured together by bolts 6 projecting through flanges 5 which protrude perpendicularly outwardly in use, from the longitudinal edges of each panel 4.A water-tight seal between adjacent panels 4 is provided by a layer 7 of ribbed azastomeric sealing materel, which may suitiuty comprise neoprene for example.
It has been found that by using folded plate panels * as described above, the segments of the vessel can be manufactured with comparatively high cost efficiency, providing an assembled caisson vessel with high structural integnty. Whereas the bated seams of the assembled vessel are "pinned" pints and theoretically form a structure under asymmetiiical loading, this apparent structural instebiZity is resisted by the provision of upper and lower supports which the panels 4 longitudinally span.The octagonal transverse section of the assembled vessel serves to induce in-plane forces that increase sealing preseune at the seams, reduce lateral disNacement of the individual panels 4 and enhance the folded plate action.
Referring to Figures 3 - 8, the upper and lower supports which space the octagonal tube of panels 4 concentrically about the leg and support it thereto, comprise an upper 8 and lower 9 spider, respectively. Each of the upper and lower spiders 8, 9 comprises a pair of semi-cylinorizal segments 30 which ciamp together at seams 31 about the leg 1.
Each spider 8, 9 further comprises a plurality of bracing fins 10, 11 extending radially outwardly from the semi-cyindrical segments 30.
The upper spider 8, shown in Figure 7, has a rim 32 pining the radial extremities of the fins 10 and dimensioned to seat closely within the internal boar of the octagonal tube of panels 4. The lower spider 9, shown in Figures 6 and 8, further comprises an annular platform 12 supported by the fins 11 to provide a water-tight floor to the caisson 3.
Positioning of the upper and lower spiders 8, 9 longitudinally of the leg 1 is dictated by upper 13 and lower 14 location collars, respectively. These collars 13, 14 adjustable camp to the leg 1 and prevent the caisson 3 sliding downwardly.
Upward movement of the caisson 3 is suppressed by an anti-buoyancy collar 15 which, as can seem in Figures 12 and 13, is again composed of two semi-cylindrical segments which are cramped together at respective flanges 16a, 16b by bolts 17. These callers may be formed of led or iron or a similar suitable heavy weight material Turning now to the purposely adapted panels 4 which accom modate vazious ones of the five branching struts 2a, e, the construction of one of these 'SiLZustrated in Figures 10 and 11.One longitudinally edge of a modified panel 4 has a semi-circular aperture cut therefrom and has a short semi-cyIindiical sleeve 18 mounted securely thereto and extending from the aperture at an angle corresponding to the pre calculated path of projection of the strut 2e, in use.
A corresponding semi-apsture and sleeve 19 are provided on the mating edge of the panel 4 intended to be placed adjacent this one.
The mating panels 4 are secured together by bolts 6' projecting through flanges 5' in similar fashion to the unmodied panels 4. An extension flange 19 is provided on the sleeve 18.
The water-tight integrity of the caisson 3 is maintained by provision of a sealing collar, suitably of G.R.P, formed of two semi-cyindrical portions which are welded together at 22 about the strut 2e and serving to hold a G.R.P annular plate 23 against an annular lim 24 provided at the extremity of the sleeve 18. If necessary, elastomeric sealing members may be placed between the plate 23 and rim 24.
The form and shape of the components of the caisson of the present invention am contribute to ease of transportation and instaL7ation. The folded planar shape of the panels 4 enables them to be stacked in a comparatively smarm vuhime container for transportation. The modular nature of the vessel, composed of several smaller components, makes on-site handing of the vessel more versatile and less cumbersome.
The panels 4 of the vessel can be manufactured in a standarised format with a number of the panels 4 being modified to accommodate one or more struts 2, or other branching members. Given prior geometrical information, individual panels can have their longitudinal edges factory-pierced to adapt them to accommodate the horizontal or raking branching members.
Panel size is preferably standardzsed to provide approximately one metre working clearance around the average diameter jacket leg ar nser. The operational length of panels is dictated by available bending equipment, minimum weight and the oost implications of increased fabrication for panels over five metres long. For full coverage of the splash zone the length of panel is most suitably up to twelve metres long.
When assembling and installing the caisson 3 the first stage of procedure is to dear marine growth from around the jacket leg or riser at the level at which the lower location caller and spider of the caisson 3 are to mounted. The two halves of the upper location caller 13 are then fitted around the jacket leg or riser 1 at a pre- selected point above sea level and the upper spider 8 is then assembZed around the leg 1 and lowered to rest on the upper collar 13.The lower location caller 14 is then secured to the leg ar riser 1 at a position determined with respect to the upper location caller 13 to give the correct degree of separation to allow fitment of the panels 4.
The largest practical proportion of the vessel formed by the panels 4 is assembled on the main deck of the marine structure. The number of panels 4 pieced together on the platform is dictated by the available lifting equipment to lower the structure in place and to omit sufficient number of panels 4 to enable the structure to be fitted around the leg or riser 1. To counter instaSy of the partembZed structure, temporary stays are fitted thereto.
On an ail or gas rig the conventional platform crane or under caller deck lifting lugs may be used to lower the part-assembled vessel onto the platform 12 of the lower spider 9. This is then bolted or damped in position.
The individual spedally pierced panels are then lowered and bolted into place.
Measures are taken b ensure that the vessel is water-tight and the bracing seals 21 are fitted to the struts 2 accent the parts for those struts 2 provided in the specially modified panels of the vessel Water within the vessel is then bailed out and the anti-buoyancy thrust caller 15 is installed. All necessary faciitties may then also be insalZed. Iiightweight access ladders and landings and necessary lighting, ventilation and other services may be provided.
Although the present invention has been described above with respect to one preferred embodiment thereof, various alternative embodiments may be conceived of without exercise of further inventive thought and falZ within the scope of the present invention. Whereas the illustrated caisson 3 comprises an assembly of eight panels 4 giving an octagonal structure, a range of other geometzical structuresare poseible. The more panels 4 used in the structure the greater the internal space in the vessel and the more versatile the modular system becomes. These factors need to be balanced against other manufacturing cost and convenience consideretions in judging the most appropriate number of panels 4 to complete the vesseL Between five and ten panels 4 is thought to be reasonable. Six or eight panels are believed to be particulaty effective.
Claims (7)
1. A marine structure repair caisson, characterised in that it is adapted to be mountable to a multi-planar node region of a marine structure support member or conduit, the caisson vessel comprising a plurality (three or more) of longitudinal segments.
2. A marine structure repair caisson which comprises a plurality of longitudinal segments, each of which is formed as a planar panel folded about the longitudinal axis.
3. A marine structure repair caisson as claimed in Claim 2 wherein each panel is folded mid-way between its longitudinal edges and is further provided with a perpendicularly outwardly, in use extending flange along each longitudinal edge.
4. A marine structure repair caisson as claimed in Claim 2 or Claim 3 in which each panel has an internal fold angle of 120oor 135, as is appropriate when six or eight panels, respectively, are used to form the vessel.
5. A marine structure repair caisson as claimed in Claim 1, 2, 3 or 4 further comprises an upper spider and a lower spider to rigidly support the assembled vessel respectively at the top and bottom thereof, in use.
6. A marine structure repair caisson as claimed in Claim 5 wherein said lower spider has an integral annular platform serving as a water-tight floor to the caisson in use.
7. A marine structure repair caisson as claimed in Claims 5 and 6, wherein the caisson further comprises upper and lower adjustable location collars to adjust the position of the upper and lower spiders respectively, enabling the position of each spider mounted to the marine structure member, in use, to be adjusted independently of the other.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9123158A GB2261007A (en) | 1991-10-31 | 1991-10-31 | Marine structure repair caisson |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9123158A GB2261007A (en) | 1991-10-31 | 1991-10-31 | Marine structure repair caisson |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9123158D0 GB9123158D0 (en) | 1991-12-18 |
| GB2261007A true GB2261007A (en) | 1993-05-05 |
Family
ID=10703876
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9123158A Withdrawn GB2261007A (en) | 1991-10-31 | 1991-10-31 | Marine structure repair caisson |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2261007A (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3386254A (en) * | 1966-04-26 | 1968-06-04 | Reading & Bates Offshore Drill | Underwater work vessel |
| US3837171A (en) * | 1971-02-05 | 1974-09-24 | J Scurlock | Inflatable underwater structure |
| GB2114636A (en) * | 1980-09-19 | 1983-08-24 | Harald Andersen Wallevik | Working chamber |
| WO1985003485A1 (en) * | 1984-02-02 | 1985-08-15 | Protec A/S | Process and apparatus for maintaining and cleaning the outer surfaces of construction members in a rig construction |
| WO1987002323A1 (en) * | 1985-10-17 | 1987-04-23 | Ove Dam | Diving bell to be used when working in the wave affecting zone at one in water standing cylindrical element like a leg of a drilling platform or a bridge pillar |
-
1991
- 1991-10-31 GB GB9123158A patent/GB2261007A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3386254A (en) * | 1966-04-26 | 1968-06-04 | Reading & Bates Offshore Drill | Underwater work vessel |
| US3837171A (en) * | 1971-02-05 | 1974-09-24 | J Scurlock | Inflatable underwater structure |
| GB2114636A (en) * | 1980-09-19 | 1983-08-24 | Harald Andersen Wallevik | Working chamber |
| WO1985003485A1 (en) * | 1984-02-02 | 1985-08-15 | Protec A/S | Process and apparatus for maintaining and cleaning the outer surfaces of construction members in a rig construction |
| WO1987002323A1 (en) * | 1985-10-17 | 1987-04-23 | Ove Dam | Diving bell to be used when working in the wave affecting zone at one in water standing cylindrical element like a leg of a drilling platform or a bridge pillar |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9123158D0 (en) | 1991-12-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |