US3921558A

US3921558A - Floatable vessel

Info

Publication number: US3921558A
Application number: US506407A
Authority: US
Inventors: Leonard Redshaw
Original assignee: Vickers Ltd
Current assignee: Vickers Ltd
Priority date: 1974-09-16
Filing date: 1974-09-16
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25

Abstract

A floatable vessel comprising a single upright buoyant column of relatively small cross-section which carries, at the lower column end, a floatable ballast chamber of relatively large crosssection. The vessel further comprises a buoyant superstructure also of relatively large cross-section slidably mounted on the column and securable thereto. Arranged within the column is a duct which extends over the height of the vessel and is open at the lower end of the vessel. The ballast chamber has a conical base which provides an inverted funnel leading to the duct opening at the lower end of the vessel. By virtue of the slidable mounting of the superstructure on the column, the vessel is either in a towing condition for towing the vessel to the intended site or it is in an operating condition in which the ballast chamber and a relatively large proportion of the column are submerged. In this condition, the vessel may be used for recovering oil escaping from the sea bed.

Description

Unlted States Patent 11 1 1111 3,921,558

Redshaw Nov. 25, 1975 FLOATABLE VESSEL [57] ABSTRACT lnvemori Leonard Redshaw, Lancashire, A floatable vessel comprising a single upright buoyant England column of relatively small cross-section which carries, [73] Assigneez Vickers Limited, London, England at the lower column end, a floatable ballast chamber of relatively large cross-sect1on. The vessel further 1 Flled? p 1974 comprises a buoyant superstructure also of relatively [21] AppL No: 506,407 large cross-section slidably mounted on the column and securable thereto. Arranged w1th1n the column 15 a duct which extends over the height of the vessel and U-S- Cl. is pen at the lower end of the vesseL The ballast [51] Int. Cl. B63B 35/44 chamber has a Conical base which provides an [58] Fleld of Search 114/5 T, D; 9/8 P; verted funnel leading to the duct opening at the lower 61/46-5, 1 1 F end of the vessel. By virtue of the slidable mounting of the superstructure on the column, the vessel is either References Cited in a towing condition for towing the vessel to the in- UNITED STATES PATENTS tended site or it is in an operating condition in which 3,165,898 1/1965 Elliott 114/.5 D x the ballast Chamber and a relatively large Proportion 3,408,821 11/1968 Redshaw 114 .5 D X of h column r g I this condition, the 3,470,838 10/1969 Daniell 114/.5 D vessel may be used for recovering oil escaping from 3,664,136 5/1972 Laval et a1. 61/1 F the sea bed. 3,667,605 6/1972 Zielinski 61/1 R X 3,738,113 6/1973 Madary et a1. 114/.5 T X 3,745,773 7/1973 Cunningham 61/1 F X Primary Examiner-Trygve M. Blix Assistant ExaminerSherman D. Basinger 10 5 Drawmg Fgures Attorney, Agent, or Firm-Thomas C. Wettach; Arland T. Stein 8 24 7 H 23 LE LL-3 1 f1 [f1 f2. i 17/1 xjs US. Patent Nov. 25, 1975 Sheet10f3 3,921,558

Nov. 25, 1975 Sheet2of3 3,921,558

I I Patent Patent Nov. 25, 1975 Sheet30f3 3,921,558

FLOATABLE VESSEL This invention relates to a floatable vessel and is more particularly, though not exclusively, concerned with such a vessel for employment as an oil recovery vessel.

In British Pat. Specification No.. 1,106,258 in the name of the present Applicants, Vickers Limited, there is disclosed a floatable vessel having an upright column of relatively small cross-section which carries a ballast chamber of relatively large cross-section positioned at or near the lower end of the column, a buoyant superstructure also of relatively large cross-sectionw'hich is slidably mounted on the column for movement between a lower position adjacent the ballastchamber and an upper position at or near the upper end, of the column, and means for securing the superstructure in said upper position. H

Although intended primarily for stationary use, the. vessel is towable to the intended site, and it is to this end that the superstructure is slidably mounted on the column. In this way, the vessel can be towed through the water with the ballast chamber relatively unballasted so that the chamber itself floats in the water, and with the superstructure positioned adjacent the ballast chamber. In this towing condition, the vessel has a relatively shallow draft as is highly desirable for towing pur-. poses, the draft of the vessel being reduced by virtue of the slidable mounting of the superstructure.

On reaching the site, the ballast chamber can be sunk and the superstructure raised to a position at or near the upper end of the column to convert the vessel into its operative condition. The vessel then has good stability by virtue of its deep draft. a

The present invention aims to employ a vessel essentially of the construction referred to, so that it has the advantage of being well suited both to towing and operative conditions at sea, and to adapt the vessel for the recovery from the sea of liquid (such as oil), having a lower specific gravity than sea water, before the liquid arrives at the surface of the sea.

According to the invention there is provided a floatable vessel comprising a single upright buoyantcolumn of relatively small cross-section whichcarries, at the lower column end, a floatable ballast chamber of relatively large cross-section, a buoyant superstructure also of relatively large cross-section slidably mounted on the column, and means for securing the superstructure to the column, wherein the improvement comprises a duct which is defined by the column and ballast chamber and which is open at the lower end of the vessel, and means for admitting liquid into the duct over a relatively large area.

Then, the vessel may be so positioned that "escaping liquid such as oil which tends to rise to the surface of the sea in the form of a reasonably coherent column gradually widening out as it ascends may be collected in the means for admitting liquid into the duct.

Preferably, the ballast chamber has a conical base which provides an inverted funnel leading to the duct opening at the lower end of the vessel and constitutes said means for admitting liquid into the duct. With such a construction, the vessel is able adequately to deal with escaping oil under most conditions.

In a preferred construction, the vessel incorporates one or more tanks and means for admitting liquid from the duct into the tank or tanks. The tank orat least some of the tanks, as the case may be, may then be flooded tobring the vessel into its operating condition. If required, oil from the ascending column of escaping oil may be stored in the tank (where only one tank is present) or in at least some of the tanks, valves located at the top of the ballast chamber being opened and the water ballast pumped overboard to allow the oil to flow into the space previously occupied by the ballast. It is desirable for the vessel. to incorporate more than one such tank and for these tanks to be housed partly in the ballast chamber and partly in the column at the lower end thereof. Then, all the tanks may be ballasted in order to submerge the vessel sufficiently to locate the superstructure at the top of the column, the superstructure being secured there. At this point, the ballast may be pumped out of each tank in the column to restore the vessel to its operating draft. Ideally, the means for admitting liquid from the duct into the tank or tanks comprise pumps.

As mentioned above, escaping oil may be stored in the tank min at least some of the tanks as the case may be. However, it is possible for the vessel further to comprise means for pumping liquid in the duct to a position above the waterline of the vessel. Then, instead of storing the oilas mentioned above, the oil may be pumped directly into an attendant tanker (or Dracone).

The vessel may be provided with venting means comprising an upward duct extension, horizontal trunking to which the duct extension leads and which is cantilevered at its outboard end well clear of the superstructure, and appropriate gas-tight connections to permit sliding of the superstructure relative to the column whilst maintaining the duct gas-tight. This arrangement is suitable for the purpose of venting unwanted gas in the duct .to the atmosphere.

In order that the invention may be more fully understood, one embodiment thereof will now be described, by wayof example, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic elevation of the vessel,

FIGS. 2A and 2B show a fragmentary elevation and a plan view of the column and the ballast chamber of the vessel, and

FIGS. 3A and 3B show similar views of the upper end of the column.

Referring to the drawings in general but FIG. 1 in particular, the. vessel consists of three essential parts, a ballast chamber 1, a vertical centre column 2 and a light alloy superstructure 3. The overall height from the bottom of the ballast chamber to the top of the superstructure may, for example, be of the order of 250 feet.

The ballast chamber 1 consists of a cylindrical shell 4 of relatively large cross-section and may, for example, be feet in diameter and 32 ft. 6 inches in height, and of all-welded mild steel construction employing conventional shipbuilding practice. The cylinder defines a duct section 5 which is open to the sea and the bottom of the ballast chamber is formed by a watertight cone 4a providing an inverted funnel leading to the duct opening at the lower end of the vessel. The interior of the ballast chamberis divided by radial bulkheads into eight separate radial tanks 6 arranged around the centre duct section 5 although, alternatively, only a single tank or a number of tanks other than eight may be accommodated in the vessel.

The column 2 is attached to, and extends upwards from, the ballast chamber and it consists of two sections of different diameters, the lower, larger, section 7 3 extending upwards as far as the operating water line, above which a tapered section 8 connects it to the upper, smaller, section 9. The column is also of all-welded mild steel construction, ring-stiffened in a manner similar to that of a submarine pressure hull.

The column 2 is divided into a number of watertight compartments 11 by means of equally spaced horizontal bulkheads and defines a duct section 12 which extends at its upper end to the upper column section 9 and which opens at its lower end into the duct section so that the two duct sections constitute a single duct. A lift trunk 13 is disposed in the duct section 12 and extends between the upper end of the column 2 and the duct section 5. Immediately above the ballast chamber, the lowest watertight compartment of the centre column comprises a water ballast tank 14 for use during the operation of ballasting the vessel down to its deepest draught to locate the superstructure at the top of the column as will be described and ballast pumps 15 for pumping liquid from the duct into the tanks 6 occupy the compartment above.

The watertight compartment at the top of the section 7 houses cargo pumps 16, which are required to transfer recovered oil from the duct to an attendant tanker or. Dracone. Around the tapered column section 8, a non-watertight extension 17 of the lower column is provided to protect manifolding to which transfer hoses are attached and, at the same time, provide a supporting structure for a sliding collar 18 which surrounds the upper column section 9 for a purpose to be described.

The superstructure 3, which is of relatively large cross-section, is constructed of aluminium alloy and is slidable on the column between the position shown in full line in FIG. 1 and a position against the ballast chamber as shown in broken line. In the upper operating condition, the superstructure is attached to the column 2 by means of the collar 18, which is also of aluminium. The collar is in the form of an annulus which accomodates the difference in diameters of the lower and

upper column sections

7 and 9 traversed by the superstructure. Suitable precautions will be taken to obviate the possibility of galvanic action occurring at the bimetallic connection between the aluminium collar and the steel centre column.

There are three decks in the superstructure, being an upper, helicopter, flight deck, an intermediate deck having a deckhouse enclosing living accommodation and a lower deck reserved for machinery and workshops. The base of the superstructure is of double walled construction to form containers for storing fuel and water. At the upper end of the column, three flats or decks are located to coincide with the three decks of the superstructure when the latter is situated at the top of the column.

The above described vessel is convertable between a transit or towing condition in which the ballast chamber is unballasted and the superstructure positioned against the ballast chamber as indicated in broken line in FIG. 1, when the draft of the vessel will be as indicated at 19, and an operating condition in which the ballast chamber is submerged and the superstructure raised clear of the water surface when the draft of the vessel will be as indicated at 21, which in the construction indicated is I80 ft., leaving the aforementioned cargo transfer hoses 20 ft. above the water line. Means are provided for securing the superstructure in either of the positions shown. In the transit condition, stability is derived from the waterplane inertia of the relatively large cross-section ballast chamber and in the operat-' ing condition stability is derived from a positive separation of the centres of gravity and buoyancy of the vessel, i.e. submarine stability. The procedure to convert from the transit to the operating condition is to admit water into the ballast tanks 6 usually in opposing pairs in order to maintain the vessel at the correct attitude, with the superstructure securing means released. Each tank 6 is provided with a sea water valve for this purpose. Thereby, the ballast chamber is sunk and the column drawn down through the superstructure which is floating until the superstructure reaches its upper position at which it is secured.

During the superstructure elevating process all eight radial tanks will be filled and in order to submerge the vessel sufficiently to locate the superstructure at the top of the column, additional ballast will be introduced to the tank 14. This will then be expelled to restore the vessel to its operating draught. The vessels draught, trim and heel may be constantly maintained by appropriate adjustments to the remaining water ballast.

In use, when an oil spill is to be dealt with, for example from a damaged well head installation, a faulty bore-hole or a leaking pipe or fitting on the sea floor, the vessel will be towed, in the towing condition, to the area of operations and positioned, as far as can be ascertained, over the centre of the source of the oil spill. The vessel will then be converted to its operating condition as described above.

The sea water in the centre column is then evacuated by extraction by the pump 16 from the upper end of the centre column and discharged overboard. While this is being done, the escaping oil will replace the displaced water in the base cone 4a and pumping operations will continue until all the sea water has been expelled. At this point, pumping will cease and hoses connected to a tanker (or Dracone) alongside, after which pumping can recommence to extract the recovered oil. If it is desired to store more oil in the vessel, valves located at the top of the ballast chamber are opened and the water ballast pumped overboard, allowing the oil to flow into the space previously occupied by ballast. This operation may be performed selectively and compensating water admitted to the centre ballast tank 14 as required to maintain draught. The total oil capacity of a vessel of the dimensions specified above would be apv proximately 6,000 tons.

Preferably and as shown in FIGS. 1 and 3A, the central duct section 12 has an upward extension to the top of the upper column section 9 for the purpose of venting unwanted gas in the duct to the atmosphere. The upward extension comprises a suitable central gas duct 22 surrounding the upper section of the lift trunk 13 and connecting with horizontal trunking 23 which is below the helicopter deck 18 and cantilevered overboard and upwards at its outboard end to a point well clear of the superstructure as indicated at 24. The trunking will require gas-tight connections where it passes through the collar 18 and will incorporate flame arrestors as required. The gas tight connections permit sliding of the superstructure 3 relative to the column 2 whilst maintaining the central duct gas-tight.

In deep water, and it should be mentioned that a vessel of the above dimensions is capable of dealing with an oil leak from the sea floor in depths down to 250 ft., the escaping oil is likely to rise to the surface in the form of a reasonably coherent column gradually widening out as it ascends, in a similar manner to the formation of smoke plumes in air. (The specific gravity of North Sea oil may be as low as 0.81 The degree of turbulence transmitted to the column of oil will obviously depend on the prevailing current and eddy conditions. However, even in moderately adverse locations it is clearly an advantage to intercept the oil before it reaches the surface than to collect it afterwards when it has commenced to spread horizontally over the surface.

I claim:

1. A floatable vessel comprising:

A. an upright buoyant column of relatively small cross-section;

B. a floatable ballast chamber of relatively large cross-section secured to the lower end of said column, said ballast chamber having a substantially vertical outer peripheral wall, a central portion, and a base, said base defining below substantially the entire ballast chamber means in communication with said central portion for admitting liquid into a duct over substantially the entire base area of the vessel;

C. a buoyant superstructure of relatively large crosssection slidably mounted on said column;

D. means for securing said superstructure to said column;

E. a duct positioned within said column having one end thereof extending over said vessel and the other end in communication with said central portion of said ballast chamber;

F. liquid storage means in said ballast chamber; and

G. means for admitting liquid from said duct into said liquid storage means.

2. A vessel set forth in. claim 1, wherein said base of said ballast chamber is conical and which in combination with said central portion defines an inverted funnel leading to the duct opening at the lower end of the vessel to comprise said means for admitting liquid into the duct.

3. A vessel as set forth in claim 2 wherein said liquid storage means comprises more than one liquid storage tank and ballast tank positioned at the lower end of said buoyant column.

4. A vessel as set forth in claim 2 including means for pumping liquid into said duct to a position above the waterline of said vessel.

5. A vessel as set forth in claim 1 wherein said liquid storage means comprises more than one liquid storage tank and ballast tank positioned at the lower end of said buoyant column.

6. A vessel as set forth in claim 1 including means for pumping liquid into said duct to a position above the waterline of said vessel.

7. A vessel as set forth in claim 1, including means for venting unwanted gas in said duct to the atmosphere, said venting means comprising an upward duct extension, horizontal trunking in sections carried by the super-structure and cantilevered at its outboard end well clear of said superstructure; and releasable connections for connecting in a gas-tight manner the trunking sections together and to the duct extension when the superstructure is secured in its upper most position to said buoyant column, said connections permitting sliding of the superstructure relative to the column.

8. A vessel as set forth in claim 7 wherein said ballast I chamber has a conical base which in combination with said central portion defines an inverted funnel leading to the duct opening at the lower end of said buoyant column to comprise said means for admitting liquid into the duct.

9. A vessel as set forth in claim 8 wherein said liquid storage means comprises more than one liquid storage tank and ballast tank positioned at the lower end of said buoyant column.

10. A vessel as set forth in claim 7 including means for pumping liquid into said duct to a position above

Claims

1. A floatable vessel comprising: A. an upright buoyant column of relatively small cross-section; B. a floatable ballast chamber of relatively large cross-section secured to the lower end of said column, said ballast chamber having a substantially vertical outer peripheral wall, a central portion, and a base, said base defining below substantially the entire ballast chamber means in communication with said central portion for admitting liquid into a duct over substantially the entire base area of the vessel; C. a buoyant superstructure of relatively large cross-section slidably mounted on said column; D. means for securing said superstructure to said column; E. a duct positioned within said column having one end thereof extending over said vessel and the other end in communication with said central portion of said ballast chamber; F. liquid storage means in said ballast chamber; and G. means for admitting liquid from said duct into said liquid storage means.

2. A vessel set forth in claim 1, wherein said base of said ballast chamber is conical and which in combination with said central portion defines an inverted funnel leading to the duct opening at the lower end of the vessel to comprise said means for admitting liquid into the duct.

8. A vessel as set forth in claim 7 wherein said ballast chamber has a conical base which in combination with said central portion defines an inverted funnel leading to the duct opening at the lower end of said buoyant column to comprise said means for admitting liquid into the duct.

10. A vessel as set forth in claim 7 including means for pumping liquid into said duct to a position above the waterline of said vessel.