GB1600291A

GB1600291A - Vessels

Info

Publication number: GB1600291A
Application number: GB4767/77A
Authority: GB
Original assignee: BRITISH OCEANICS Ltd
Current assignee: BRITISH OCEANICS Ltd
Priority date: 1977-02-04
Filing date: 1977-02-04
Publication date: 1981-10-14
Also published as: CA1112952A; IT7820020A0; NL7801196A; SE7801287L; NO780394L; JPS53119587A; FR2379428A1; BR7800743A

Description

(54) IMPROVEMENTS IN OR RELATING TO VESSELS (71) We, BRITISH OCEANICS LI MITED, a British Company, of 12-18.

Grosvenor Gardens, London SW1L ODW, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to submersibles or like vessels such as submarines.

According to the present invention there is provided a submersible or like vessel comprising propulsion means to enable the vessel to be positioned in a desired location, a tank to receive water, a compartment having water tight external walls including an opening and a water tight closure for the opening, and a means facilitating personnel and/or equipment transfer between said compartment and a sub-surface chamber having a hatch, said means comprising: (i) an open ended skirt depending from the walls so as to surround said opening, and (ii) a conduit system connecting the tank and the volume defined by the skirt whereby said volume can be depressurised by allowing water to pass from said volume to said tank.

In use, the vessel is manoeuvred by its propulsion means until the skirt is in alignment with the hatch in the sub-surface chamber. Then, the skirt volume is depressurised, by means of said conduit system so that the ambient water pressure causes the vessel to be urged towards the chamber so that the mating surface of the skirt is sealingly engaged with a mating seat located around the sub-surface chamber hatch. The water in the skirt volume will then be at a pressure equivalent to the hydrostatic head in the skirt volume and thus personnel working in or passing through that water will not be subjected to full ambient pressure. Alternatively, the water within the skirt volume may be removed so that personnel may work, or transfer, in dry conditions.In this case the water may be pumped to the surrounding water or, in a particularly preferred embodiment, drained into the subsurface chamber in accordance with out copending patent application No. 4768/77.

(Serial No. 1600292).

In a particularly preferred embodiment, the skirt is detachably secured to the vessel wall. In this way the skirt can be removed when it is desired to use the vessel for, for example, survey work and quickly and easily attached to the vessel when it is desired to transfer personnel and/or equipment to a sub-surface chamber.

When the transfer of personnel and/or equipment has been completed and it is desired to separate the submersible from the sub-surface chamber, the skirt volume has to be pressurised. This can be effected by allowing water to enter the skirt volume from the surrounding body of water via the aforementioned conduit system. Alternatively the water used for pressurisation may be the aforementioned water drained into the sub-sea chamber in accordance without copending patent application No. 4768/77 (Serial No. 1600292). In this case, after the water has been pumped into the skirt volume from the sub-sea chamber, the skirt volume should be opened up to the surrounding body of water so as to raise the pressure in the skirt volume to the ambient pressure.

In order to assist in separating the submersible from the sub-sea chamber, a means is preferably provided to pump water into the skirt via said conduit system so as to overpressurise the skirt volume.

In a further embodiment it is particularly preferred to provide an emergency means for pressurising the skirt volume. In this case, a second conduit system may be provided linking the gas storage tanks or the compressed air supply of the submersible with the skirt volume.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a partly sectioned side elevation of a submersible in accordance with the present invention.

Figure 2 is a schematic section of a part of the submersible of Figure 1. and Figure 3 shows a portion of the part of Figure 2 on a greatly increased scale.

Referring to the drawings, there is shown a submersible including a water-tight hull 1, enclosing forwird and aft water-tight compartments 2 and 3 respectively. The forward compartment 2 is occupied by the pilot of the vessel and thus includes all the necessary controls for the ordinary functions of the vessel. The aft compartment 3 is a diver lock out compartment and includes in its bottom wall an opening closable in a water-tight manner by a hatch cover 4.

The submersible has a propulsion means comprising a main propeller 31 powered by a motor 32. The propulsion means also includes fore and aft thrusters (33 and 34 respectively) to provide the submerisble with the ability to move laterally and twin thrusters (only one of which is shown and denoted by reference numeral 35) to provide the submersible with the ability to move vertically.

A skirt 5 of substantially part-sphencal shape and formed of glass fibre reinforced plastics material is removably secured to the hull 1 around the periphery of the opening in a water-tight manner. The skirt 5 has an open end defined by a rim including a resilient sealing arrangement having a sealing surface Sb. The sealing arrangement may be in accordance with out copending patent application No. 4769/77 (Serial No.

1600293).

The arrangement whereby the skirt 5 is secured to the hull 1 is shown in more detail in Figure 3. It can be seen that the skirt 5 is effectively secured to trunking flange 6 surrounding the hatch opening by means of a plurality of individual stainless steel dogs 7 arranged around the periphery of the flange 6 and by metal rings 8, 9 and 1(). Ring 8 is formed of stainless steel and rings 9 and 10 are aluminium. Each dog 7 has a lip which fits over the flange 6 of the hatch opening and is secured to the skirt clamping ring 8 by means of stainless steel bolts. That end of the skirt 5 nearest the hatch opening is bifurcated so that it includes a branched portion 5a which is bolted to the skirt clamping ring 8 via the segmented clamping rings 9 and 10.The skirt clamping ring includes two O-rings 11 and 12, ring 11 sealing the skirt clamping ring 8 to the end of the skirt 5 and ring 12 sealing the skirt clamping ring 8 to the flange 6.

Provided in the diver lock out compartment 3 are the aft trim tanks 13. The location of the trim tanks 13 with respect to the hatch opening is such that the centre of gravity of the water in the trim tanks passes through the centre of the opening and is approximately on the same vertical line as the centre of gravity of the submersible itself.

A pipe is provided to link the skirt volume with the interior of the compartment 3 and is in the form of a penetration through the hatch and fitted with vent valves VJ on the inside.

A first conduit system is provided to link the volume defined by the skirt 5 with the trim tanks 13. This system comprises a pipe 14 extending from the trim tanks 13 and out through the hull 1 via a penetrator (not shown) to communicate with a further pipe 15 having one end venting externally of the submersible via a ball valve VA and another end extending via a penetrator (not shown) through the wall of the skirt 5 and terminating in two hull stops in the form of ball valves VB and VC. Pipe 14 carries a first branch including decompression valve V63 and communicating with the atmosphere in the diver lock-out compartment 3 and a second branch incorporating a valve V58 communicating via a pump P, with the forward trim tank 16 (partly shown in dotted line only in Figure 2) contained in the pilot compartment 2.A ball valve VF is provided between the first and second branches in pipe 14 to isolate the aft trim tanks 13 and the second branch passes through the watertight partition between compartments 2 and 3 by way of a penetrator (not shown).

Further, pipe 14 includes a hull stop valve V61 and an aft trim fill valve V62 internally of the hull.

The valve VA is mounted externally of the hull and is operated by a double acting hydraylic ram 17 linked to the manifold of the emergency hydraulic system 20 illustrated diagrammatically in dotted line only of the submersible via hydraulic pipes 18 and 19 passing through the hull via penetrators (not shown) and incorporating hull stops in the form of ball valves VM and VN respectively. Control valves VK and VL are incorporated in the pipes 18 and 19 respectively. A hand pump 21 for the hydraulic system is also provided.

The submersible includes and emergency pressurisation system in the form of a second conduit system extending from a storage sphere of mixed gas (not shown) or from a source of compressed air (not shown) to the skirt volume.

This second conduit system comprises an external pipe 22. At one end this pipe passes through the skirt 5 via a penetrator (not shown) and terminates in hull stops in the form of ball valves VD and VE in the interior of the skirt volume. At its other end, pipe 22 passes through the hull via a penetrator (not shown) and a hull stop in the form of a ball valve VH and then terminates in branches 23 and 24. Located between the hull stop ball valve VH and the pipe branches are a check valve NR1 and a control valve VG. Branch 23 is connected to the storage sphere for mixed gas and branch 24 is connected to the compressed air system of the submersible.

The submersible is normally launched with valves VA. VB, VC, VD and VE in the open position. Air will generally be trapped in the skirt volume upon launching and this should be vented since its presence will reduce the stability of the submersible. This venting is effected via valves VA, VB and VC so that the air may pass from the skirt volume 5 along pipe 15 and out of valve VA (valves V61 and V62 being closed at this time). In this way. water will enter the skirt volume up until the level of valve VC. The residual air trapped in the upper portion of the skirt volume between valve VC and the hatch 4 is vented into compartment 3 by means of valves VJ.

In use of the submersible to transfer personnel to or from a sub-sea chamber, the submersible is submerged in conventional manner and manoeuvred by the pilot using the thrusters 33, 34, and 35 and propeller 31 of the submersible until the skirt is in its mating position with respect to the sub-sea chamber i.e. the open end of the skirt 5 is in alignment with a hatch within a mating seat provided in the outer wall of the sub-sea chamber and the sealing surface Sb is coplanar with the mating seat of the sub-sea chamber. At this stage, as a safety precaution, the second conduit system should be pressurised up to the hull stop VH by opening valve VG. With the valve VA closed, the hull stop V61 and the aft trim fill valve V62 are opened.Because of the pressure difference between the atmospheric pressure in the compartment 3 and the ambient pressure in the skirt volume, water will flow from the skirt volume through the pipes 15 and 14 and into the aft trim tanks 13. Thus the downward force of the submersible is increased and the submersible is urged towards the sub-sea chamber. Because of the symmetrical distribution of the aft trim tanks 13 about the centre of gravity.

the increased downward force occurs without significantly upsetting the trim of the submersible. Once the sealing surface Sb of the skirt is sealing engaged with the mating seat of the sub-sea chamber, there will be a rapid decrease in pressure in the skirt volume as the water flows into the aft trim tanks 13. When the seal has been obtained, and the pressure in the skirt volume has become substantially equal to the pressure in compartment 3 i.e. substantially equal to atmospheric pressure, the valves V61 and V62 are closed. The pressure difference between the skirt volume 5 and the ambient pressure serves to clamp the submersible tightly against the sub-sea chamber.In the event that, after depressurising, the pressure in the compartment 3 is slightly lower than that in the skirt volume 5 due to the water remaining in the external pipework 15, this can be eliminated by opening valve VJ. The hatch 4 can then be opened and personnel can transfer into the skirt volume 5. At this stage, the skirt will still contain water and this can be drained down into the sub-sea chamber as described in out copending patent application No. 4768/77 (Serial No. 1600292) or alternatively be pumped out into the surrounding body of water. It is then possible to make a dry transfer from the compartment 3 into the sub-sea chamber or vice versa.

After the transfer has been completed and it is desired to separate the submersible and the sub-sea chamber, then it is necessary to re-pressurise the skirt volume after the hatch 4 has been closed so that the pressure in the skirt volume is substantially equal to the ambient pressure. Ordinarily, this is done by filling the skirt volume with water. In a particularly preferred embodiment, this is effected by pumping back into the skirt volume the water which was drained down into the sub-sea chamber as described in our copending patent application No. 4768/77 (Serial No. 1600292) followed by opening valve VA (whilst valves V61 and V62 are closed) in order to open the skirt volume to the surrounding body of water and thereby increase the pressure in the skirt to ambient pressure.In this case, there may be provided, within the skirt, an electrical connector (not shown) to connect the electric power supply of the submersible to the electric pump in the sub-sea chamber.

The skirt volume may however be flooded directly from the sea by opening valve VA whilst valves V61 and V62 are closed. In this case the air in the skirt volume is displaced into compartment 3 via valves VJ by the incoming water and compartment 3 is subsequently depressurised when the submersible is at the surface by opening valve V63 and valves V61 and V62 are open.

After pressurisation has been completed, it may be necessary to provide an overpressure in the skirt volume in order to break the seal. This can be achieved by closing valves VA and VF, opening valves V61, V62 and V58, and pumping water into the skirt volume from the forward trim tank 16 via pump P. Thereafter valves V61, V62 and V58 should be closed and valves VA and VF should be opened. Once the seal has been broken, control valve VG can be closed since the emergency pressurisation system will not then be needed.

In the event that a rapid separation is desired in an emergency this can be effected by ensuring that valves V61, V62, and VA are closed and then opening valve VH (valves VD and VE already being open). In this way, either mixed gas from the storage sphere or compressed air can be rapidly introduced into the skirt volume to rapidly pressurise the same. Once the seal has been broken, valve VA should then be opened.

In the event that valve VA should fail in the closed position, the skirt volume can be pressurised with valve VF closed and valves V58, V61, V62 and V59 open to allow seawater to enter the skirt volume Via pipes 14 and 15.

WHAT WE CLAIM IS: 1. A submersible or like vessel comprising propulsion means to enable the vessel to be positioned in a desired location, a tank to receive water, a compartment having water tight external walls including an opening and a water tight closure for the opening, and a means facilitating personnel and/or equipment transfer between said compartment and a sub-surface chamber having a hatch, said means comprising: (i) an open ended skirt depending from the walls so as to surround said opening, and (ii) a conduit system connecting the tank and the volume defined by the skirt whereby said volume can be depressurised by allowing water to pass from said volume to said tank.

2. A submersible or like vessel as claimed in Clam 1. wherein said tank is a trim tank of the vessel.

3. A submersible or like vessel as claimed in Claim 1 or 2, and including a means to pump water from the skirt volume into the surrounding body of water when. in use, the open end of the skirt is sealingly engaged against the outer wall of the chamber so that the transfer may take place in dry conditions.

4. A submersible or like vessel as claimed in any one of Claims 1, 2 and 3 and including a means to allow water to enter the skirt volume from the surrounding body of water once transfer has been completed.

5. A submersible or like vessel as claimed in Claim 4 wherein the means to allow water to enter the skirt volume comprises a valve permitting water to flow from the surrounding body of water into said conduit system and thence into the skirt volume.

6. A submersible or like vessel as claimed in any one of Claims 1 to 5 and including a means to increase the pressure in the skirt volume once transfer has been effected so as to break the seal between the open end of the skirt and the outer wall of the chamber.

7. A submersible or like vessel as claimed in Claim 6 wherein said means to increase the pressure comprises a pump for transferring water from a tank in the vessel into said conduit system and thence into the skirt volume.

8. A submersible or like vessel as claimed in Claim 6 or 7 wherein said means to increase the pressure comprises a source of compressed air and/or other gas and a further conduit system for conveying the same from the source to the skirt volume.

9. A submersible or like vessel as claimed in any one of the preceding claims wherein the skirt is detachably secured to the vessel.

10. A submersible substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. V58 should be closed and valves VA and VF should be opened. Once the seal has been broken, control valve VG can be closed since the emergency pressurisation system will not then be needed. In the event that a rapid separation is desired in an emergency this can be effected by ensuring that valves V61, V62, and VA are closed and then opening valve VH (valves VD and VE already being open). In this way, either mixed gas from the storage sphere or compressed air can be rapidly introduced into the skirt volume to rapidly pressurise the same. Once the seal has been broken, valve VA should then be opened. In the event that valve VA should fail in the closed position, the skirt volume can be pressurised with valve VF closed and valves V58, V61, V62 and V59 open to allow seawater to enter the skirt volume Via pipes 14 and 15. WHAT WE CLAIM IS:

1. A submersible or like vessel comprising propulsion means to enable the vessel to be positioned in a desired location, a tank to receive water, a compartment having water tight external walls including an opening and a water tight closure for the opening, and a means facilitating personnel and/or equipment transfer between said compartment and a sub-surface chamber having a hatch, said means comprising: (i) an open ended skirt depending from the walls so as to surround said opening, and (ii) a conduit system connecting the tank and the volume defined by the skirt whereby said volume can be depressurised by allowing water to pass from said volume to said tank.