GB2114636A

GB2114636A - Working chamber

Info

Publication number: GB2114636A
Application number: GB08203949A
Authority: GB
Inventors: Harald Andersen Wallevik
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-09-19
Filing date: 1982-02-11
Publication date: 1983-08-24
Also published as: NO802780L; FR2521095A1; NL8200329A; GB2114636B; NO146053B; AU8011882A

Abstract

A working chamber for use in underwater work on a pipe, pipe node, platform leg or the like has a chamber which consists of two chamber halves (7, 8) which are hinged together (at 12) at one longitudinal edge thereof. The two halves (7, 8) of the chamber can be locked together in contact against each other, and at the bottom and top of the chamber an opening (31) is provided, adapted for the introduction of the member, e.g. a platform leg (3), in connection with which the chamber is to be used. In the upper part of the chamber (1), a sealable manhole (36) is provided. <IMAGE>

Description

SPECIFICATION Working chamber The present invention relates to a working chamber for enabling repairs, corrosion protection, inspection, maintenance and other work operations to be carried out, from the splash zone and downwards to a maximum practical depth, on offshore structures, quays and harbour installations, pipelines and other structures made of wood, steel, concrete, plastic, etc.

Underwater structures, especially in salt water, are extremely subject to corrosion and other damage. This is particularly true in the so-called splash zone, where there is an abundant supply of oxygen. Such submerged or submersible structures are being utilized to an ever increasing extent, especially since the development of the offshore oil industry in recent years. In this technical field, one finds numerous structures such as drilling platforms, production platforms, hotel platforms, oil and gas pipelines and other installations. Very high safety standards are set for such structures, and constant inspection and maintenance work are therefore required. It is obvious that it is very difficult to perform such work on submerged or submersible structures.In the case of semi-submersible platforms, these can of course be raised so that at least a portion of the legs will be above the surface of the water, and they can also be towed or sailed under their own power into the nearest dock. Such a procedure, however, is very costly since the platform must then be taken out of operation. In the case of production platforms, such a procedure probably cannot be followed at all. On pipeline installations, because they are permanent, it is not possible to carry out inspection and maintenance in the manner described above, either.

The object of the present invention, therefore, is to provide an apparatus, more specifically a working chamber, by means of which the above work can be performed in a simple and inexpensive manner, and wherein personnel can perform the work using ordinary equipment and at at least approximately normal air pressure.

This is obtained in accordance with the invention with a working chamber which is characterized in that it consists of two or more chamber sections, that the sections of the chamber can be locked together in contact against each other, that at the bottom and the top of the chamber an opening is provided adapted for the introduction of the member, for example a platform leg, in connection with which the chamber is to be used, and that at the upper part of the chamber a sealable manhole is provided.

In a preferred embodiment of the invention, the chamber has a cylindrical configuration and consists of two halves which are hinged together at the coincident longitudinal edges thereof.

In accordance with the invention, sealing gaskets are provided at the adjoining edges of the chamber halves and at the margin of the opening for receiving the member in connection with which the chamber is to be utilized.

A further feature of the invention is that an upwardly directed, watertight passageway or tunnel is provided in connection with the manhole, intended for personnel access.

Still another feature is that a power-driven closure mechanism is provided for pivoting the halves of the chamber about the hinges toward and optionally away from each other.

Other features will be apparent from the following description of the invention in connection with the accompanying drawings, which illustrate embodiments of the invention as well as some detail features thereof.

Figure 1 shows one embodiment of a working chamber in accordance with the invention, mounted at two different locations on the legs of an oil rig.

Figure 2 shows an embodiment of the working chamber of the invention mounted on a tubular leg in the splash zone.

Figure 3 is a schematic cross-section through the working chamber of Figure 2.

Figure 4 shows the working chamber of the invention as seen from above, in position during mounting.

Figure 5 shows a detail of the sealing means around the member in connection with which the working chamber is to be utilized, intended for relatively modest depths.

Figure 6 shows various other possible embodiments of the working chamber of the invention, utilized on different structures.

Figure 1 shows how an embodiment of a working chamber in accordance with the invention may be utilized in connection with inspection and repair work on an oil rig 2. The legs 3 and 4 of the rig are in this case cylindrical, and it is therefore practical that the working chamber also has a cylindrical configuration. On the leg 3, the working chamber 1 is positioned in the splash zone, so that personnel can enter the chamber from the open air. On the leg 4, the chamber is attached to the leg beneath the surface of the sea 5, and personnel must then enter the chamber through an access shaft 6 which will be explained in greater detail later on.

Figure 2 shows the exterior of the working chamber in somewhat greater detail. The working chamber 1 consists of two almost identical halves 7 and 8. In the illustrated example, the chamber is mounted on a tubular leg 3. Each half 7 and 8 thus constitutes a half-cylinder. The working chamber is sealed against the leg by means of heavy-duty gaskets 9 and 10. For safety, the top end of the chamber is provided with a railing 11.

The two chamber halves 7 and 8 are hingedly connected to each other by a hinge connection 1 2 at one longitudinal edge thereof. The two halves thus can be moved toward and away from each other about the hinged edge, and are mounted on the tubular leg 3 in the open state, as shown in Figure 4.

A tubular leg on a platform may have a diameter of 8-10 meters or more, and the working chamber of the invention will thus be of quite large dimensions. It is therefore necessary to provide auxiliary means for closing the halves of the chamber from the position shown in Figure 4 into the position shown in Figure 2, for example. In the embodiment example illustrated in Figures 2, 3 and 4, the closure device consists of a winch 1 3 which in this case is placed at the upper end 1 4 of the chamber. In this example, the working chamber is positioned with its upper end above the surface of the water, so that such placement of the winch is possible.If the working chamber 1 is to be positioned entirely underwater, as shown on the right leg 4 in Figure 1, it may be necessary to rig up an auxiliary deck 1 5 (Figure 1) on which the winch is placed. In the example illustrated, three cables 16, 17, 1 8 travel from the winch and pass over directional sheaves 19, 20, 21 to the edge of the opposing chamber half 8. Here, the cables are secured over a conical guide member which engages with apertures in the longitudinal edge of the chamber half 7, thus ensuring correct abutment of the two halves of the chamber.

At the upper end 14, the working chamber has two hatches for the introduction of air hoses, personnel and equipment.

As described above, the working chamber is mounted in an open state, as shown in Figure 4.

The working chamber will thus be partially or completely filled with water when it has been mounted in position. To evacuate the water, bilge pumps 22 and 23 are provided.

Inside the chamber, scaffolds 24 as indicated by the dashed lines in Figure 3 are provided. As shown in the drawing, these ought to be mounted so as to lie as nearly horizontal as possible when the chamber is in the mounted position.

As shown in Figure 2, an underwater escape hatch 25 is also provided, and there is also a ladder 26 on the exterior of the chamber. The escape hatch can be opened from both the outside and the inside. In case of emergency, it can be jerked free entirely with the aid of, for example, a supply ship.

In Figure 3, stiffening struts 27 are provided at about the middle of the working chamber. These may consist of solid wooden planks placed in a circle around the leg 3 and supported against the walls of the chamber at an angle of about 50 relative to the leg. Under the impact of waves and vibrations, the wooden beams in this position will form a very effective supporting ring inside the working chamber, as the planks will then be caused to flex somewhat and thus provide an effective reinforcement of the chamber wall.

As mentioned above, the two halves of the working chamber are connected to each other by means of a hinge connection. This hinge connection must be made to be slidable in relation to the two abutting edges of the chamber halves to allow the chamber to be mounted on the leg 3.

On the hinge side, in addition to the hinges, a bolt connection is also provided which can be tightened so that gaskets along the abutting edges of the chamber become firmly ciamped and sealed together. During this clamping and sealing operation, the gaskets 9 and 10 around the platform leg must be completely loose. These gaskets 9 and 10 therefore have to be of a special construction, and Figure 5 shows an embodiment of a such gasket. The seal consists of a solid, broadly-profiled, continuous band of rubber 28 which is intended to lie around the platform leg.

On the side of the band intended to be in contact against the leg, two hollow, annular gaskets 29 are arranged, constituted by soft rubber hoses which can be inflated with air or pressure fluid.

Outside the ring 28 there is a clamping shoe which is divided into a plurality of sections 30 and which presses the strip of rubber tightly against the leg 3. Each annular section 30 is movably attached at the margin of the opening 31 at the top and bottom of the chamber. When the chamber, in the position shown in Figure 4, is to be placed around the leg 3, the bolts 32 are loosened until the chamber is in place. Thereafter the sections 30 are tightened firmly against the gasket 28 so that the iatter is pressed firmly and sealingly against the leg 3. At the upper edge of the band or rubber 28 a metal strip 33 is fastened which can be split crosswise at regular intervals.

Two strong steel bands 34 surround the entire gasket 28 at one end thereof, and these can be drawn together mechanically or hydraulically. At the opposite edge of the gasket 28 a steel cable 35 is wound around the gasket in two turns, and this cable can be twisted together, e.g., with the aid of mechanical means.

In Figure 6, four examples of other possible configurations of a working chamber, other than the cylindrical configuration discussed above, are shown. Figure 6a shows a chamber of triangular shape, adapted for use on a pipe node. Figure 6b shows a chamber whose shape is adapted to, e.g., a platform leg having a diagonal, upwardlydirected strut member Figure 6c shows a working chamber whose configuration is adapted to a straight, vertical leg having a horizontal strut member, and Figure 6d is a cylindrical working chamber adapted for use on a horizontal submerged pipe.

As mentioned above, the chamber is accessible from the top end thereof. For this purpose at least one manhole 36 is arranged in the top side (deck) of the chamber. When the upper part of the chamber 1 is lying above the surface of the water, personnel can enter the chamber directly through the manhole, which is subsequently sealed watertight by means of a cover. If, however, the chamber is completely submerged as shown on the right-hand side of Figure 1 and in Figure 6d, it will be necessary to provide a shaft or passageway 6 down to the manhole. This shaft must naturally be secured watertight to the manhole opening. In addition to said manhole, there may be one or more additional openings in the upper part of the chamber, for the introduction of air hoses, hydraulic lines, electrical cables and the like.

Claims

1. A working chamber for use in underwater work on an underwater member, the chamber consisting of two or more chamber sections which can be locked together in contact with each other; an opening being provided at the bottom and the top of the chamber and adapted for the introduction of the member in connection with which the chamber is to be used; a sealable manhole being provided in the upper part of the chamber.

2. A working chamber according to claim 2, wherein the chamber has a cylindrical configuration and consists of two halves which are hinged together at the coincident longitudinal edges thereof.

3. A working chamber according to claim 2 wherein a power-driven closure mechanism is provided for pivoting the chamber sections about the hinges toward and optionally away from each other.

4. A working chamber according to claim 3 wherein the power-driven closure mechanism comprises a winch and at least one cable passing over a respective sheave at the edge of one half of the chamber opposite from its hinged edge to the corresponding edge of the other half where the cable is secured.

5. A working chamber according to claim 2, claim 3 or claim 4 wherein the hinges are slidably disposed on at least one of the chamber sections, transversely of the abutting longitudinal edges thereof, and at the hinge side of the chamber section means are provided for drawing the abutting edges of the chamber sections toward each other on the hinge side.

6. A working chamber according to any preceding claim, wherein the chamber sections at their adjoining edges and at the margin of the opening for the introduction of the member with which the chamber is to be utilized, are provided with gaskets.

7. A working chamber according to claim 6 wherein the gaskets at the margin of the opening for the said member comprise a band of rubber adjustably clamped to the chamber and provided with means for drawing the upper and lower edges of the band into contact with the member.

8. A working chamber according to claim 7 wherein the said gaskets include inflatable annular gasket members intermediate their ends.

9. A working chamber according to any preceding claim wherein an upwardly directed, watertight passageway or tunnel is provided in connection with the manhole.

1 0. A working chamber according to any preceding claim, wherein one or more bilge pumps are provided inside the chamber.

11. A working chamber as claimed in any preceding claim including resilient struts for supporting walis of the chamber, the struts extending between the walls of the chamber and the member with which the chamber is to be utilized.

12. A working chamber substantially as hereinbefore described with reference to Figures 1 to 5 or Figure 6 of the accompanying drawings.