GB1604978A - Container for holding electrical equipment underwater - Google Patents

Description

(54) CONTAINER FOR HOLDING ELECTRICAL EQUIPMENT UNDERWATER (71) We, THE BRITISH PETROLEUM COMPANY LIMITED, of Britannic House, Moor Lane, London EC2Y 9BU, a British Company, 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 a container suitable for holding electrical equipment underwater.

In the development of oil and gas fields at offshore locations it is often necessary to use certain electrical equipment, for example, pumps and valve actuators and to locate this equipment underwater. The electrical power for this equipment is often supplied from the surface and it is desirable, when operations are in deep water, for example several hundred feet or more, to supply the power at relatively high voltage and transform the power to a lower voltage in the region of the electrical equipment. There is therefore a need for an electrical transformer capable of working submerged in water several hundred feet in depth and a container has now been devised for holding a transformer or other electrical equipment and which enables same to be used in water of this depth.

According to the present invention a container suitable for holding electrical equipment underwater comprises: a housing providing a first chamber for holding the electrical equipment and a water immiscible electrically non-conducting liquid (referred to as the liquid) so that the equipment is immersed in the liquid, the first chamber having a closable opening for the entry of the liquid, the housing having means for making electrical connection between the interior of the first chamber and the exterior of the housing, the first chamber being divided from a second chamber by a flexible partition to accommodate thermal expansion of the liquid, the second chamber being beneath the first chamber when the container is in its normal working position and having a closable opening to the exterior which is openable to provide means for substantially equalising the pressure between the interior of the first chamber and the exterior of the housing when the container is located underwater, and wherein means are provided for substantially equalising pressure on both sides of the flexible partition when the first and second chambers contain liquid and the container is in air in its normal working position.

The means for making electrical connection between the interior and exterior of the housing can conveniently be one or more conventional cable sealing terminal box assemblies which are well known to those skilled in the electrical art.

The means for equalising pressure on both sides of the flexible partition can comprise a pipe communicating with the second chamber, the pipe extending to a level in the region of the top of the housing.

The electrically non-conducting water immiscible liquid is conveniently a hydrocarbon bil hereafter referred to as oil.

The opening of the second chamber can be located at the bottom thereof to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

References to the bottom and top refer to the container in its normal working position.

The closable opening of the first chamber for the entry of the liquid can be located at or near the bottom of the first chamber to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

The invention is illustrated by reference to the accompanying drawing which is a vertical section of the container.

The container indicated generally by numeral 2 comprises a housing 4 made of a glass reinforced polyester resin which provides a first chamber filled with a hydrocarbon oil in which is located electrical equipment in the form of transformer 14 supported on struts 16. The first chamber has openings for the entry of the oil communicating with pipes 26 and 28 and is divided from a second chamber 8 by a flexible partition 6 to accommodate thermal expansion of the oil.

The second chamber 8 has a closable opening 12 for substantially equalising the pres sure between the interior of the first chamber and the exterior of the housing when the container is underwater. The opening 12 is located at the lowermost point of the container and communicates with pipe 30 whereby the second chamber 8 is in fluid communication with the exterior of the housing. The location of the opening 12 is to prevent entry of water. The electrical imput to the transformer 14 is by means of an exterior electric cable 18 connected to a lead 20 inside the housing 4 via a conventional cable sealing box assembly 22. The exterior cable 18 is held securely by flange 24. A second cable (not shown) is connected in like manner whereby the output from transformer 14 is taken.

To prevent damage to the partition 6 by the weight of oil above the diaphragm when the container 2 is in the air above water, the pressure on both sides of the partition 6 is equalised by means of an oil filled pipe 10 running from the second chamber 8 up the exterior of the housing 4 to a level at least as high as the oil in the housing 4. The pipe communicates with opening 12.

To fill the container 2 it is first inverted from the position shown in the drawing and the housing filled with oil through filling holes 26 and 28 so that all air is expelled and the partition 6 is in a relaxed state. Then the second chamber 8 and pipe 10 are filled with oil via pipe 30 and valves 32 and 34 closed.

The container is then righted and installed at its underwater location where valve 32 is opened.

In the event of thermal expansion of the oil in the housing 4 the partition 6 is compressed reducing the volume of second chamber 8 and oil is discharged therefrom via pipe 30.

The apparatus described in the above drawing has the following advantage: in use underwater the pressure inside the housing is the same as that outside with the result that the housing need not be able to withstand high pressures and can be made of a lightweight material.

WHAT WE CLAIM IS: 1. A container suitable for holding electrical equipment underwater comprising: a housing providing a first chamber for holding the electrical equipment and a water immiscible electrically non-conducting liquid (referred to as the liquid) so that the equipment is immersed in the liquid, the first chamber having a closable opening for the entry of the liquid, the housing having means for making electrical connection between the interior of the first chamber and the exterior of the housing, the first chamber being divided from a second chamber by a flexible partition to accommodate thermal expansion of the liquid, the second chamber being beneath the first chamber when the container is in its normal working position and having a closable opening to the exterior which is operable to provide means for substantially equalising the pressure between the interior of the first chamber and the exterior of the housing when the container is located underwater, and wherein means are provided for substantially equalising pressure on both sides of the flexible partition when the first and second chambers contain liquid and the container is in air in its normal working position.

2. A container as claimed in claim 1 wherein the means for equalising pressure on both sides of the flexible partition comprises a pipe communicating with the second chamber, the pipe extending to a level in the region of the top of the housing.

3. A container as claimed in claim 1 or 2 wherein the opening of the second chamber is located at the bottom thereof to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

4. A container as claimed in any one of the preceding claims wherein the closable opening of the first chamber for the entry of the liquid is located at or near the bottom of the first chamber to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

5. A container as claimed in any one of the preceding claims the housing thereof containing electrical equipment immersed in an electrically non-conducting water immiscible oil of specific gravity less than 1.0.

6. A container substantially as hereinbefore described with reference to the accompanying drawing.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. sure between the interior of the first chamber and the exterior of the housing when the container is underwater. The opening 12 is located at the lowermost point of the container and communicates with pipe 30 whereby the second chamber 8 is in fluid communication with the exterior of the housing. The location of the opening 12 is to prevent entry of water. The electrical imput to the transformer 14 is by means of an exterior electric cable 18 connected to a lead 20 inside the housing 4 via a conventional cable sealing box assembly 22. The exterior cable 18 is held securely by flange 24. A second cable (not shown) is connected in like manner whereby the output from transformer 14 is taken. To prevent damage to the partition 6 by the weight of oil above the diaphragm when the container 2 is in the air above water, the pressure on both sides of the partition 6 is equalised by means of an oil filled pipe 10 running from the second chamber 8 up the exterior of the housing 4 to a level at least as high as the oil in the housing 4. The pipe communicates with opening 12. To fill the container 2 it is first inverted from the position shown in the drawing and the housing filled with oil through filling holes 26 and 28 so that all air is expelled and the partition 6 is in a relaxed state. Then the second chamber 8 and pipe 10 are filled with oil via pipe 30 and valves 32 and 34 closed. The container is then righted and installed at its underwater location where valve 32 is opened. In the event of thermal expansion of the oil in the housing 4 the partition 6 is compressed reducing the volume of second chamber 8 and oil is discharged therefrom via pipe 30. The apparatus described in the above drawing has the following advantage: in use underwater the pressure inside the housing is the same as that outside with the result that the housing need not be able to withstand high pressures and can be made of a lightweight material. WHAT WE CLAIM IS:

1. A container suitable for holding electrical equipment underwater comprising: a housing providing a first chamber for holding the electrical equipment and a water immiscible electrically non-conducting liquid (referred to as the liquid) so that the equipment is immersed in the liquid, the first chamber having a closable opening for the entry of the liquid, the housing having means for making electrical connection between the interior of the first chamber and the exterior of the housing, the first chamber being divided from a second chamber by a flexible partition to accommodate thermal expansion of the liquid, the second chamber being beneath the first chamber when the container is in its normal working position and having a closable opening to the exterior which is operable to provide means for substantially equalising the pressure between the interior of the first chamber and the exterior of the housing when the container is located underwater, and wherein means are provided for substantially equalising pressure on both sides of the flexible partition when the first and second chambers contain liquid and the container is in air in its normal working position.

2. A container as claimed in claim 1 wherein the means for equalising pressure on both sides of the flexible partition comprises a pipe communicating with the second chamber, the pipe extending to a level in the region of the top of the housing.

3. A container as claimed in claim 1 or 2 wherein the opening of the second chamber is located at the bottom thereof to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

4. A container as claimed in any one of the preceding claims wherein the closable opening of the first chamber for the entry of the liquid is located at or near the bottom of the first chamber to assist in preventing entry of water when the liquid is one having a specific gravity of less than 1.0.

5. A container as claimed in any one of the preceding claims the housing thereof containing electrical equipment immersed in an electrically non-conducting water immiscible oil of specific gravity less than 1.0.

6. A container substantially as hereinbefore described with reference to the accompanying drawing.