GB2258853A

GB2258853A - Improvements in lifting apparatus and methods

Info

Publication number: GB2258853A
Application number: GB9116465A
Authority: GB
Inventors: Stephen Forbes Pearson; Anthony Cuthbert
Original assignee: BEATTIE MARGARET SHAN; CONRAN OLIVER FELIX; GROUND TO AIR AND AEROSPACE DR; Star Refrigeration Ltd
Current assignee: BEATTIE MARGARET SHAN; CONRAN OLIVER FELIX; GROUND TO AIR AND AEROSPACE DR; Star Refrigeration Ltd
Priority date: 1991-07-30
Filing date: 1991-07-30
Publication date: 1993-02-24
Anticipated expiration: 2011-07-30
Also published as: GB9116465D0; GB2258853B

Abstract

An apparatus (10) for lifting objects (14) from the bed (12) of the sea, lake, river etc. comprises a housing (20) having side walls (24) provided with passages (30) for cooling medium which may derive from a mechanical refrigeration unit or from a source of pressurised liquified gas (38) e.g. carbon dioxide. The open base of the housing is placed over the object, and the surrounding water frozen so as to secure the object to the housing. The housing is then lifted so as to raise the object. Water jets or other excavating means may be provided at the lower ends of the walls 24 to form troughs 42 around the object. <IMAGE>

Description

IMPROVEMENTS IN LIFTING APPARATUS AND METHODS FIELD OF THE INVENTION This invention relates to apparatus and methods for use in lifting objects from water, and in particular to the retrieval of objects from the sea-bed.

BACKGROUND OF THE INVENTION Recovery of objects located underwater presents many problems, and is particularly difficult if the object is fragile, contains hazardous material or is difficult to grip.

SUMMARY OF THE INVENTION It is an object of the present invention to facilitate the lifting of objects from water.

In one aspect of the present invention there is provided apparatus for use in lifting objects from water comprising a housing having an open base for location over an object, cooling means extending into the interior of the housing for freezing water between the cooling means and the object to form an ice connection therebetween to secure the object in the housing, and means for lifting the housing together with the object held by the ice.

Preferably, the cooling means is located in the walls of the housing, such that when the cooling means is operated the ice will advance from the walls to encompass the object to a point below the major dimension of the object. The interior surfaces of the walls of the housing may be corrugated or otherwise formed to securely locate the ice on the walls.

The housing may be insulated to minimise ice formation on the exterior surfaces of the housing.

Preferably also, the cooling means includes passages for passing a cooling medium through the walls of the container. Most preferably, the cooling medium is a gas which has been expanded from the liquid state.

Carbon dioxide provides a suitable cooling medium as'it can be contained at ambient temperature and moderate pressure without need for continuous venting.

Alternatively, liquid nitrogen, liquefied natural gas or any other suitable liquefied gas may be used. Means for storing the liquefied gas may be mounted on the housing together with suitable expansion means.

Alternatively the cooling medium may be provided by means of a mechanical refrigeration unit mounted on the housing, or the cooling medium may be supplied from a support craft on the surface of the water.

The lower ends of the walls of the housing may include means for excavating the sea-bed below the walls to permit the lower ends of the walls to extend into the sea-bed. The excavating means may take the form of water jets. Where delicate objects are to be lifted this feature allows the freezing of a portion of the sea-bed below the object, which part of the sea-bed may be lifted with the housing.

According to a further aspect of the presentinvention there is provided a method of lifting objects from water comprising: providing a housing having cooling means extending into the interior thereof; positioning the housing over an object; operating the cooling means to freeze the water adjacent the cooling means until the ice so formed advances from the cooling means to engage the object; and lifting the housing to the surface with the object held in the ice.

BRIEF DESCRIPTION OF THE DRAWING These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawing which illustrates, somewhat diagrammatically, a sectional view of lifting apparatus in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWING The drawing shows lifting apparatus 10 located on the sea-bed 12 being used to lift an object 14 from the sea-bed 12. The apparatus 10 is connected to a support ship (not shown) on the surface by lifting means in the form of a wire rope 16. Various control wires 18 also extend between the apparatus and the ship.

The apparatus 10 includes a housing 20 with an upper wall 22, side walls 24, and an open base 26. The side walls 24 are provided with cooling means including passages 30 containing a cooling medium in the form ofexpanded carbon dioxide gas. As will be described, the gas cools the inner wall surfaces 32 to form ice 34 on the wall. With continued cooling, the ice advances to engage the object 14 allowing the object 14 to be lifted from the sea-bed 12, secured within the housing 20.

The exterior wall surfaces 36 and the upper wall 22 are insulated to minimise ice formation on the exterior of the housing 20.

The carbon dioxide gas is supplied from pressurised storage cylinders 38 mounted on the exterior of the housing 20. The cylinders 38 contain liquefied carbon dioxide which is passed through a suitable expansion device 40 and into the passages 30. After passing through the passages 30 the carbon dioxide may be vented into the surrounding water, used to inflate flotation bags or may be passed through suitable conduits for collection on the support ship.

The cooling of the inner wall surfaces 32 results in cooling of the water in the housing 20 and the formation of ice on the wall surfaces 32. As cooling of the wall surfaces continues, the ice 34 advances and will eventually surround the object 14. However, it is normally only necessary, at least with robust objects, that the ice extends beyond the major dimension of the object, as is shown in the drawing. The inner wall surfaces 32 may be corrugated to provide a larger cooling area and also to more securely locate the ice to the walls.

The housing 20 is then lifted from the sea-bed to the support ship where the ice 34 is melted to release the object 14. In the drawing, the lower ends of the side walls 24 are shown located in shallow troughs 42.

This may occur simply due to the weight of the housing 20 as it is lowered into position around the object 14 and sinks into the soft sediment on the sea-bed.

Alternatively, water jets or other excavating means (not shown) may be provided at the lower ends of the walls to form deeper troughs. In this situation, the ice formed on the inner walls surfaces 32 will extend into a portion of the sea-bed which will be lifted with the housing 20 when the ice forming operation is completed.

This is useful when the apparatus is being used to lift delicate objects such as portions of shipwrecks or parts of aircraft.

The position and operation of the apparatus 10 may be monitored by divers or, more preferably, is monitored remotely from the support ship. For this purpose, suitable cameras and sensors (not shown) may be provided on the housing 20.

Carbon dioxide is the preferred cooling medium as liquefied carbon dioxide may be contained at ambient temperature and moderate pressure without need for continuous venting. However, in certain circumstances other cooling mediums such as liquid nitrogen, liquefied natural gas or any other suitable liquefied gas may be used. It is also possible to supply the cooling mediumfrom a mechanical refrigeration unit mounted on the housing or to supply the cooling medium from the support ship.

As will be evident from the above description, the present invention provides a method and apparatus which is effective in lifting objects of many different forms from water. Although reference is made above to the sea-bed the present invention is of course equally suitable for use in lakes and rivers.

It will be clear to those of skill in the art that the above described embodiment is merely exemplary of the present invention and that various modifications and improvements may be made without departing from the scope of the present invention; in certain circumstances it may be desirable to provide the housing with movable walls to facilitate receiving objects of different shapes, and also means may be provided for closing or partially closing the base of the housing.

Claims

1. An apparatus for use in lifting objects immersed in water, which comprises a housing having an open base for location over an object, cooling means extending into the interior of the housing for freezing water between the cooling means and the object to form an ice connection therebetween to secure the object in the housing, and means for lifting the housing together with the object held by the ice.

2. An apparatus according to claim 1 wherein the housing includes means for physically locating the ice on walls of the housing.

3. An apparatus according to any preceding claim wherein the housing includes passages for passage of cooling medium.

4. An apparatus according to any preceding claim wherein the cooling means is a mechanical refrigeration unit.

5. An apparatus according to any of claims 1 to 3 wherein the cooling means comprises a storage vessel containing a pressurised liquified gas, and connected to refrigeration expansion means.

6. An apparatus according to claim 5 which further comprises flotation means attached to the housing and adapted to receive expanded gas which has passed through the expansion means.

7. An apparatus according to any preceding claim, which further comprises excavating means for excavating a bed on which the object may be lying.

8. An apparatus according to any preceding claim, which further comprises closure means for closing the open base of the housing to prevent the lifted object falling out.

9. An apparatus for use in lifting objects immersed in water substantially as described in conjunction with the drawings.

10. A method of lifting objects immersed in water which comprises: providing a housing having cooling means extending into the interior thereof; positioning the housing over an object; operating the cooling means to freeze the water adjacent the cooling means so that the ice so formed advances from the cooling means to engage the object; and lifting the housing with the object held in the ice.