EP0241525A1

EP0241525A1 - 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

Info

Publication number: EP0241525A1
Application number: EP19860906299
Authority: EP
Inventors: Ove Dam; Einar Dyhr; Jens Lauritzen
Original assignee: DAM Ove; Dyhr Einar
Current assignee: DAM Ove; Dyhr Einar
Priority date: 1985-10-17
Filing date: 1986-10-17
Publication date: 1987-10-21
Also published as: AU6592186A; DK475085A; DK475085D0; WO1987002323A1

Abstract

Cloche de plongée destinée à être utilisée pour effectuer des travaux dans une zone exposée aux vagues sur un élément cylindrique situé dans l'eau tel qu'une jambe (2) d'une plate-forme de forage ou un pilier de pont, consistant en deux ou plusieurs parties reliées ou séparées (1, 3) pouvant être réunies en une position étanche à l'eau et verrouillées autour de l'élément cylindrique. Une découpe (6) dans la cloche permet d'adapter cette dernière de manière étanche et verrouillable sur la surface de l'élément cylindrique (2). Le fond de la cloche est complètement ou partiellement ouvert, et un organe pneumatique alimente l'intérieur de la cloche en air comprimé pour provoquer l'expulsion de l'eau contenue dans la cloche. Grâce à cet agencement les déchets produits ne s'accumulent pas à l'intérieur de la cloche, où l'espace est limité, du fait qu'ils peuvent tomber à l'extérieur de la cloche.Diving bell intended to be used for carrying out work in an area exposed to waves on a cylindrical element located in the water such as a leg (2) of a drilling platform or a bridge pillar, consisting of two or more connected or separate parts (1, 3) which can be joined together in a watertight position and locked around the cylindrical element. A cutout (6) in the bell makes it possible to adapt the latter in a sealed and lockable manner on the surface of the cylindrical element (2). The bottom of the bell is completely or partially open, and a pneumatic member supplies the interior of the bell with compressed air to cause the expulsion of the water contained in the bell. Thanks to this arrangement, the waste produced does not accumulate inside the bell, where the space is limited, because it can fall outside the bell.

Description

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 .

SPECIFICATION

The present invention refers to a diving bell used when working in the swell zone around a cylindrical element standing in water such as the legs of a drilling platform or a bridge pillar and comprises two parts which can be closely locked together around the cylindrical object and with a recess suitable for making tight contact with the outside of the cylindrical object.

Offshore constructions such as drilling platforms and bridge pillars are very exposed to corrosion in what is known as the swell area, i.e. at the surface of the water where the construction has ample access to the oxygen in the air while water is present. Irrespective of whether the construction is of steel or concrete, it is more exposed to corrosion and degradation in the swell zone than any other part of the construction which is either continuously below or above the water. R egular inspection and maintenance of the construction in the swell zone are therefore necessary. The surface is cleaned by sand blasting and is given a water-resistant coating whose durability shall be regularly maintained.

Norwegian Application No. 146 053 illustrates an completely closed working chamber comprising two or more parts which can be locked together in position with an opening at the bottom and top of the chamber for the cylindrical object. When the chamber is positioned, it is drained of water with a standard drain pump. The working chamber has however been shown to be unsuitable for the intended purpose since sand from the sand blasting machine and the layer of material removed from the cylindrical object accumulates at the bottom of the chamber. On legs which are normally found on drilling platforms with a diameter of approximately 1.75 m and a chamber height of approximately 5.0 m, which corresponds to the swell zone, the quantity of sand used can amount to 500-600 kg which is a considerable increase in the load on the working chamber. There have been instances of such working chambers falling from the leg of a drilling platform.

The purpose of the present invention is to provide the diving bell with a design described in the introduction where the waste products are dispersed at the same rate as they are produced. According to the present invention, this is achieved by having the bottom of the diving bell partly or fully open and having a compressed air unit to supply compressed air to the interior of the diving bell to displace water. In this manner, the sand from the sand blasting and the coatings removed fall to the bottom of the diving bell and into the water. The pressure required to keep out the water from within an approximately 5.0 m high diving bell is approximately 0.5 bar, in other words it is sufficiently low to permit work to be carried out at this pressure without any special measures needing to be taken. It is recommended that the compressed air unit and the sand blasting equipment be located outside the diving bell and a bit above it and that they are connected to the diving bell via hoses which have watertight connections.

The design of the diving bell is individual insomuch as it comprises a top section designed for attachment and fastening around the object and a number of wall units designed for attache ent to the top section once this has been attached to the object to be cleaned. The upper edges of the wall elements have attachment devices designed to fit the attachment devices around the periphery of the top section, and the wall elements' side edges are designed with connection devices for linking together. Furthermore there is a support device at the lower end of the elements designed for attachment to the body and to the connection and control devices for interacting with the corresponding connection and control devices on the wall elements. In this manner, the diving bell is constructed of a small number of easily-handled simple parts which can be relatively simply and easily put together, a fact that is important bearing in mind the weather conditions which are experienced around offshore constructions. By designing the diving bell in this manner so that the bottom section and possibly the intermediate deck can be lowered and raised in relation to the top section with the aid of a lowering and raising device, for example in the form of a wire hoist, the parts can be attached around the leg of a drilling platform as a whole after which the intermediate deck and the bottom can be lowered into position.

The special design of the top section uses a divided top deck with an opening for the object to be cleaned and a framework on the top side whose side is attached to a divided top. When assembling in moderate weather or in more exposed waters, assembly can take place by individual parts being grouped around the platform's leg after the bottom section has been fitted in position. The method of procedure will become clearer to the reader in the following account of a concrete example.

The design of the jointing of the top section and the wall elements is individual insomuch as the wall elements and their upper end and outside have a horizontal T rail fitted with rollers which runs on the underside of a section on the top deck and where the other edge of the T rail runs on rollers in a suspension device attached to the frames, and where the upper part of the wall element enters the section that is open downwards and which on three inner faces has inflatable sealing strips. Through this design, the wall elements can be lowered vertically into the water and then displaced sideways into position. The construction forms a good guide for the elements and the sealing strips are inflated to provide a seal once the elements are in position.

The design of the connection and sealing devices along the side edges of the wall elements is produced by bending the elements' side edges so that two adjacent side edges can engage each other, and so that at the bottom of one of the recessed edges has a sealing strip. This is a simple design without additional separate attachment devices. Such robust and simple constructions without many small loose parts are necessary for work on offshore structures. The guide and connection devices on the wall elements' lower edge comprise a horizontal T section attached to the element above a hollow section, and with the devices on the bottom support comprising two verticals positioned so that the T piece's flanges slide against the inside of the verticals and the inside of the hollow section towards the outside of the verticals, and where the verticals are flexibly mounted so that they can be radially displaced. By moving the wall elements in a radial direction, the wall elements' jointing and sealing devices lock together and seal.

Using a design where the wall elements can also be laterally displaced, the verticals are attached to a plate whose edges grip the guide strip, and where for sideways displacement of the frames there is at least one air or hydraulic cylinder fixed to the structure and the plate, and that for radial displacement there is a cylinder similarly attached to the structure and the plate.

Since the frames are cut at an angle within the bell and in towards the gap between them, the wall elements attachments are easily engaged.

A further configuration of the diving bell is that it comprises a number of vertical rods from the periphery of the top section with two links designed either for snapping into fixed contact with the object to be cleaned, and at least two horizontal support rings which can glide down over the verticals and be fastened to them, so that the wall elements are positioned inside the verticals and support rings and that there are coupling devices for attaching the elements to the support rings. The design is characterised in that individual parts are relatively small and thus easier to handle while at the same time installation is simple.

A design example of the diving bell according to the present invention is described- in more detail while referring to the attached drawings which illustrate the diving bell in a purely schematic manner. Fig. 1 shows a schematic perspective of the diving bell while being attached to the leg of a drilling platform.

Figs. 2,3,4 show one half section of the top of the diving bell seen from the side and from above.

Fig. 5 shows the top of the diving bell seen in perspective, mounted on the drilling platform's leg.

Fig. 6 shows a section through one side of the diving bell and when mounted on the drilling platform's leg.

Fig. 7 shows one of the support fittings seen from above.

Fig. 8 shows one of the support fittings seen from the side.

Fig. 9 shows a vertical section through a different configuration of the diving bell.

Fig. 10 shows a wall element with integral ladders.

Fig. 11 shows a section through the diving bell at Section A-A in Fig. 9.

Fig. 12 shows a section through the diving bell at Section B-B in Fig. 9.

Fig. 13 shows the interacting joint between elements on an enlarged scale, c.f. Detail E in Fig. 12.

Fig. 14 shows the detail of a joint between the top section and wall elements on an enlarged scale according to Detail C in Fig. 12.

Fig. 15 shows a general view from Fig. 14 along line D-D. Fig. 16 shows an enlargement of the connection and guide devices between the support and the wall elements seen from inside the diving bell.

Fig. 17 shows the devices in Fig. 16 seen from the side, and

Fig. 18 shows the devices from above.

Figs. 19-27 illustrate schematically the assembly of a further configuration of the diving bell according to the present invention.

Fig. 28 shows, purely schematically, the diving bell attached to the leg of the drilling platform.

Fig. 29 shows a section in the top of the diving bell.

Fig. 30 shows a section in the wall of the diving bell.

Fig. 31 shows the general detail of the assembly of the wall elements for the support rings.

Fig. 32 shows a general view of the joints between the wall elements.

Fig. 33 shows a wall element purely schematically.

Fig. 34 shows one of the uprights being moved into position during installation.

The diving bell comprises a top section 1 which is clamped to the drilling platform's leg 2, wall element 3, which is hooked on top section 1, and which is supported and attached below by radial support 4.

The top section comprises two identical parts la shown in figures 2-4 which can be clamped together around the leg with clamps 5, and in the clamped state there is a recess for leg 2. At the top of top part 1 there is a peripheral collar 7 for installations with the leg over a rubber liner 8. It is necessary for all assemblies and installations to have a rubber seal to produce the necessary tightness and, for installations with legs, the necessary function for fixing the diving bell to the leg.

There are four wall elements 3, where each constitutes a quarter circle, and which are suspended by hook 9 on the top section 1. Wall elements 3 are supported on radial support 4 whieh comprises four parts as shown in figures 7 and 8. The four sections are clamped together around the leg together with the rubber liner, and each section has a bracket 10 upon which the wall element is supported and fixed.

The design of the diving bell shown in drawings 9-18 comprises a top section 1 which is made up of a top cover 12, to which a number of frames 13 can be attached on the top side, and which is also attached to a top 14. The top deck, frames and top are made of segments which can be clamped around the drilling platform's leg 2.

Frames 13 are fitted with what are called "slips" 15, a device where the top section can move freely up and down on the leg to the required position. The movement is achieved with aid of wedges 16 and hydraulic cylinders 17.

On frames 13 there are wire winches 18 with twin drums for lowering and raising intermediate deck 19 and a radial support 4. Wire 21 is attached to the intermediate deck 19 and wire 22 is attached to the radial support 4.

To fix the intermediate deck 19 and radial support 4 in the required positions, there are stops 20', 20"; 21', 21" above and below these to prevent them moving as a result of wave action and work in progress. The stops are attached to the wall elements. To support intermediate deck 19 there are braces 22 which can be swung up from the wall.

The radial support 4 is equipped with horizontal _,-- cylinders 23 which can be made to apply pressure against the drilling platform's leg 2 and which thus pushes the lower part of the wall elements according to the principle explained in the following. Radial support 4 is fitted with buoyancy bodies 26 whose buoyancy can be regulated so that top deck 1, intermediate deck and the device can be made to float on water or so that the intermediate deck and device 4 can sink into position in the water.

Top deck 12 is a watertight deck sealed against the drilling platform's leg 2 with an inflatable seal 24, for example a rubber tube.

A wall element 3 equipped with ladders 25 and buoyancy bodies 26 for manoeuvering the ^"element into position is shown in drawing 9.

Drawing 11 shows a section along line A-A in figure 9 where it is possible to see frames 13 which can be attached to two semicircular rings 27', 27" and which can be locked around leg 2.

The section shown in figure 12 illustrates intermediate deck 19 comprising two semicircular frame constructions 28', 28" which can be joined around leg 2. Gratings are laid across the frame to form a floor. The inner section up to the leg can be covered with loose arc-shaped floor segments 29 so that allowances can be made for various leg thicknesses. 30 indicates a cut in the grid 28 for ladder 25.

The jointing of the wall panels along the sides is achieved with a bend 31, 32 along the side edges so that two adjacent edges grip each other. At the bottom of one bend there is a sealing strip 33, preferably of rubber, so that the edge of one element forms a seal with it. The shape of the sealing strip is such that the bent part of one element seals the side and with the end of the edge. The principle is explained in more detail in the following.

Figures 14 and 15 show how the wall elements are attached to top section 1. At a distance below the upper edge the outside of the wall elements are fitted with a horizontal T rail 34, where the wall element can be suspended on mounting 35 attached to frames 13. The mounting comprises two rollers 36 upon which the wall element's T rail can run. The wall element above the wall rail penetrates section 37 which is open at the bottom. To control the wall element, the upper side of the T section is fitted with roller 38 at each end of the element, which supports and runs on a bent section of section 37. Three inflatable seals 39', 39" and 39"' are fitted in section 37 to seal the wall element against the top section. These seals are fitted to the end of the wall element and on both sides.

Figures 16 and 17 shows coupling and control devices for controlling and coupling the wall elements with the bottom support device. On the inside of the wall elements, the lower ends are fitted with a T rail 39 over a hollow section 40. Radial support 4 is fitted with a plate 41 which supports a guide 42 in the form of two sections 42' and 42" fitted at a distance from each other and designed so that one side of the wall element's hollow section slides against the other side. The upper end of the two uprights are bevelled in towards the bell and in towards the slot so that the wall element's guides 39, 40 can just be gripped during times of difficult working conditions.

Base plate 41 is steered by the three edges of guide strip 43. There are three pneumatic or hydraulic cylinders 44', 44" and 44"' to move the plate and thus the guide and the wall element from side to side and ih and out.

The mounting of the diving bell to the leg of a drilling platform is described in more detail in the following.

1. When installing in reasonably good weather and in sheltered waters, the installation can be carried out as follows:

a) Intermediate deck 19 and bottom 4 are moved up and lie against top deck 12. Frames 13 are mounted on top deck 12.

b) The two halves are moved in and joined at the top and the bottom around the drilling platform's leg.

c) I.:÷3rmediate deck 19 and the bottom .4 are then lowered with winch 18 to the correct depth and bottom 4 is locked to the leg.

d) The wall elements 3 are moved in horizontally, one by one. Some of the temporary buoyancy bodies are released and the elements are lowered until they contact guide 42 fitted to intermediate deck 19 and bottom 4.

e) Wall element 3 is pushed up to the rollers and held in position.

f) Wall element 3 is moved horizontally with the aid of the longitudinal pistons 44' and 44" so that the wall elements grip each other completely.

g) When all the wall elements are in position, radial piston 44" is operated.

h) Bellows 2 is pumped up followed by bellows 3.

i) The slip is activated and the seal at the top deck is activated.

j) The bell is now pressure-tight and the water is expelled.

k) Stop 1 and then stop 2 are applied and the lower support for the intermediate deck is swung up and engaged.

1) The diving bell is now ready for use.

2. When installing in marginal weather or in more exposed waters, the diving bell can be assembled as follows:

a) Bottom 4, which may comprise two or more parts is lifted in position and assembled free from the action of waves with the aid of a platform crane or stiffleg mounted on the drilling platform's leg. Bottom 4 is locked to the column.

b) The necessary number of parts of intermediate deck 19 are lifted onto bottom 4 and assembled.

c) Top deck 12 is lifted in and assembled d the connection wires fitted. d) Frames 13 are lifted in and mounted on top deck 12, the connection wires are fitted to winches 18, "slips" and top locks are fitted.

f ) Wall elements 18 are lifted in and fitted.

9) Seal 24 on the top deck is partially inflated, i.e. until a seal is just made and so that the water can be forced out as required. By balancing the amount of air in the bell, it can be brought to any depth that may be required.

h ) The necessary connections for air, water, electricity, chemicals etc can be taken through the top deck 12. Similarly, a dry exit can be established via an airlock in top deck 12.

Figures 19-34 show an additional configuration of diving bell according to the present invention.

As before, the bell comprises a top section 1 designed to be clamped around the drilling platform's leg 2. In this case, the top section comprises an inner ring 45 with the "slip" referred to earlier, and an outer ring 46, which constitute the top deck. Verticals 47 can be attached to the upper section, which below have links 47' and 47" designed for snapping onto the drilling platform's legs for support. To engage and hold the horizontal support rings 48 and 49 there are hooks 50 in verticals 47.

For assembling the wall elements, the underside has a longitudinal dovetail groove 51, which can interact with bolts or pins on the support rings since these have a head which fits groove 51.

For intereonnection of wall elements 3, their longitudinal edges have an angular bend 53 so that two opposing support edges can engage each other. The angular bends can be provided with a scarf and sealing strip 54.

Figure 29 shows the assembly between the wall elements' upper edge and the top section. The periphery of the top section has a groove with a bevelled edge facing the middle of the bell. Correspondingly, the upper edge of the wall element is bevelled 56, so that the edge can engage the groove. On the underside of the element is a support flap 57, which supports against the edge of the upper section's groove.

The actual mounting of the diving bell on a leg of a drilling platform is illustrated schematically in figures 19-27 since a crane 58 is previously mounted on the platform's leg 1 and can take individual parts from a supply ship 59 and lift them into position.

a) The inner ring 45 is assembled on the leg, see figure 20.

b) The outer ring 46 , which makes up the top deck , is fitted.

c) The vertically suspended members 47 are attached to the periphery of the top deck.

d) The upper and lower support rings 48 and 49 are assembled on the leg and are moved down onto members 47 and engaged with hooks 50 designed for the purpose.

e) The two links 47' and 47" for the ends of members 47 have so far been bent downwards in a V. They are now pushed up to suspension link 60 and tension the members along the support rings for final and secure attachment.

f) The wall elements are slid in position from above since with groove 51 they slide over the bolt and pin heads.

g) The wall elements are then pushed up so that the bevel cut edge

56 engages the groove 55 on the top section.

h) The assembly is then completed. The supply lines can then be attached, tests carried out and the working platform outside the bell fitted.

Top section 1 and wall elements 3 can be designed as a sandwich construction of glass fibre and fitted with steps, lighting and other equipment that may be necessary. Similarly, working gratings can be fitted at different levels. The top section is fitted with a manhole 11 and the necessary services penetrations for compressed air and sand blasting.

The diving bell is easy to assemble and dismantle. It is also made of imperishable materials. Furthermore, sand from the sandblasting and the coatings removed disappear through the bottom of the bell.

Claims

PATENT CLAIMS

1. A diving bell for use when working in the swell zone on a cylindrical object standing in the water, such as legs (2) on a drilling platform or bridge pillars, and comprises two or more linked or separate parts (1, 3), which can assembled as a sealed installation with each other around a cylindrical object with a groove (6) suitable for a sealing lockable installation with the outside of the cylindrical object (2) c h a r a c t e r i s e d i n t h a t the bottom of the bell is fully or partially open open and that there is a compressed air unit for supplying compressed air to the interior of the bell to expel water from it.

2. The diving bell according to Claim 1 is c h a r a c t e r i s e d i n t h a t it comprises a top section (1) designed for mounting and clamping around the body (2) and a number of wall elements (3) which are designed for attachment to the top section when this has been mounted on the body (2) since the upper edges of the wall elements (3) have coupling devices to engage the coupling devices at the outer periphery of the top section, and where the wall elements' (3) side edges are designed with assembly devices for interconnection, which comprise a support device (4) at the lower ends of the elements designed for clamping around the body (1) and with coupling and control devices for interacting with the corresponding coupling and control devices on the wall elements.

3. The diving bell according to Claim 2, c h a r a c t e r i s e d i n t h a t the radial support (4) and an intermediate deck if fitted (19) being such that they can be lowered and raised in relation to the top section with the aid of a raising and lowering device, for example in the form of a wire winch (18).

4. The diving bell according to Claim 3, c h a r a c t e r i s e d i n t h a t the top section comprising a divided top deck (12) with a groove for the body (1) and frames (13) attached to the upper side which in turn are attached to a divided top (14).

The diving bell according to Claim 2, c h a r a c t e r i s e d i n t h a t wall elements (3) have a horizontal T rail (34) at the upper edges and the outside fitted with rollers (38) which run on the underside of a section (37) on the top deck (12) and where the other edge of the T section (34) runs on rollers (16) in a hanger (35) attached to the frames (13), and where the upper section of the wall element (13) engages the section (37) which is open downwards and which has inflatable sealing strips (39) on the three inner sides.

6. The diving bell according to Claim 2, c h a r a c t e r i s e d i n t h a t the connection and sealing devices along the edges of the wall elements (3) comprise bends (32, 33) in the side edges so that the two opposing side edges can engage each other and that the bottom of one of the bent edges has a sealing strip

(33).

7. The diving bell according to Claim 2, c h a r a c t e r i s e d i n t h a t the control and coupling devices at the lower ends of the wall elements comprise a horizontal T section (39) attached to the element over a hollow profile (40) and that the devices on the bottom support (4) comprise two members (42) applied with a spacing and such thet the T section's flanges slide against the bodies' (42) inner face and the inside of the hollow section against the underside of the bodies, and where the bodies are flexibly mounted so that they can be moved in a radial direction.

8. The diving bell according to Claim 7, c h a r a c t e r i s e d i n t h a t the bodies are attached to a plate (41) whose edges engage the guide strips (43), and where the lateral displacement of the bodies is made by at least one pneumatic or hydraulic cylinder (44' and 44"') connecting to and attached to the plate, and where the radial displacement is carried out by a cylinder (44") which is similarly connecting to and attached to the plate.

9. The diving bell according to Claim 7, c h a r a c t e r i s e d i n t h a t the bodies (42) are bevel cut in towards the bell and the gap between them.

10. The diving bell according to Claim 2, c h a r a c t e r i s e d i n t h a t it comprises a number of verticals (47) from the periphery of the top (1) with two links (47' and 47") for either slotting into fixed contact with the body (2), and at least two horizontal support rings (48 and 49) which can slide over the verticals (47) and the support rings (48, 49) and that there are coupling devices (51 and 52) for attaching the elements (3) to the support rings (48 and 49).