WO1994018066A1

WO1994018066A1 - Tanker

Info

Publication number: WO1994018066A1
Application number: PCT/NL1994/000036
Authority: WO
Inventors: Markus Van Der Laan
Original assignee: Laan Markus V D
Priority date: 1993-02-15
Filing date: 1994-02-15
Publication date: 1994-08-18
Also published as: AU6157294A

Abstract

Carrier for transporting (crude) oil comprising a centre cargo tank (1) a bottom tank (6a) and wing tanks (4a, 5a) located on both sides of the centre cargo tank (1) wherein an additional bulkhead (7) is fitted in each wing tank forming an upper ballast tank (8) with a lower double side (8a) and a lower inboard cargo tank (9).

Description

TANKER

The present invention relates to a tanker for carrying a bulk cargo, such as (crude) oil, or for carrying different bulk cargoes on combination trades such as the so-called Oil Bulk Ore ( OBO) carriers.

OBO carriers are well known and have been built in large numbers and are used for the transport of oil. bulk and ore.

In general, this construction performs properly.

However, due to disasters with crude oil carriers and their large pollutional effect, a world-wide effort is made to improve the safety of tankers and nowadays there is an increasing need to construct tankers in such a way that in case of wreck or other marine catastrophe leakage of cargo and thus environmental pollution is avoided or minimized.

A solution for this problem is requiring a complete double hull for oil tankers and for that purpose tankers have been built in the past with double bottoms and double sides, which, however, brought about substantial increases in the prices of tankers.

Further, double bottom constructions have the drawback that buoyancy loss in groundings may occur and in case the bottom of a cargo tank is penetrated due to corrosion and/or erosion, oil may leak into the double bottom and generate a hazardous mixture of air and hydrocarbonaceous vapours, in case for instance oil is the cargo. Apart from the potential danger for explosion, there would be the requirement for gas detection and thorough ventilation of the double bottom before entry for routine structural inspections. Moreover, access to a double bottom also causes a problem. It must be through a vertical shaft or double side which is led right up to the deck. Other concerns include the maintenance of the steel structure in double bottoms, in particular preservation of the large coating area which is required for the prevention of corrosion

Therefore mam organizations question the double hull as the best solution for oil pollution prevention and there is a need for alternatives provided that they offer the same level of protection against oil outflow as the double hull tanker

It is an object of the invention to provide a tanker for carrying a bulk cargo of such a construction that environmental pollution is avoided or mimimized in case of wreck or other marine catastrophe with a minimum increase of cost and wherein the level of protection against oil outflow m case of damage has been improved

The present irvention therefore provides a tanker for carrying a bulk cargo such as (crude) oil or for carrying different bulk cargoes or combination trade comprising at least a longitudinally extending centre cargo tank at least a bottom tank below the centre cargo tank and wing tanks located on either side of the centre cargo tank and separated from the centre cargo tank by a longitudinal structure characterized in that an additional longitudinal structure is fitted m each wing tank forming an upper ballast tank witn a lower double side and a lower inboard cargo tank.

In this manner the following improvements are obtained:

- small oil outflow in case of collisions and groundings

- good salvage and clean up features

- well-known sound construction at lower costs

- reduced ballast coating area which leads to lower costs - proper accessibility and maintenance

- safety against explosions and suffocation hazards

- less sediments in ballast tanks.

The invention will now be described by way of example in more detail with reference to the accompanying drawings m which:

fig 1 represents schematically a cross-sectional view of a known standard Oil Bulk Ore (OBO) carrier; figure 2 represents schematically a cross-sectional view of the basic idea of a carrier design according to the invention;

figure 3 represents schematically a cross-sectional view of an advantageous embodiment of a carrier design according to the invention; and

figure 4 shows schematically a cross-sectional view of a further embodiment of a carrier design according to the invention.

Referring to fig. 1, a known standard OBO-carrier,

schematically shown in cross-sectional view, comprises a centre cargo tank 1 extending longitudinally over any convenient distance.

The said cargo tank 1 has a top wall 2 and a bottom 3.

Wing cargo tanks (4,5) are located on either sides of the centre cargo tank 1 and are separated from the centre cargo tank 1 by

longitudinal structures 10 such as bulk heads which may be straight or may comprise at least one "knuckle" 11 (as shown in the figure).

Further, a bottom tank 6 for ballast (e.g. water) is shown located below the centre cargo tank 6. The sea-level is represented by S-S.

In fig. 2 the basic idea of the carrier design of the

invention has been shown. The same reference numerals as applied in fig. 1 are used to represent the same parts of the carrier. The centre cargo tank 1 provided with the top wall 2 and the bottom 3 has been shown. Further, the sea-level S-S has been shown.

Wing tanks (4a, 5a) are located on either sides of the centre cargo tank 1 and a bottom centre cargo tank 6a is located below the centre cargo tank 1.

Additional longitudinal structures 7 are fitted in each wing tank (4a, 5a) in any way suitable for the purpose thus forming in each wing tank an upper ballast tank 8 with a lower double side 8a and a lower inboard cargo tank 9.

Advantageously, the additional longitudinal structures 7 are bulk heads, and, more advantageously, a horizontal barrier e.g.

near half height and a vertical barrier e.g near the side shell.

Optionally, the tanker of the invention can be provided with a cargo transfer system (not shown for reasons of clarity), which leads to additional safety. In case of a penetrated cargo tank the cargo outflow can be limited by reducing the pressure inside the damaged tank. This can be achieved by transferring cargo to an (empty) ballast tank or storage tank, using a pumping system or the available hydrostatic (over)pressure.

For example, the lower inboard cargo wing tank may be connected in any suitable manner to the lower double side 8a of the upper ballast tank 8 located at the other side of the tanker.

For example, a connecting tube can be installed running from one cargo wing tank 9 through the bottom centre cargo tank 6a and the other cargo wing tank 9 to the lower double side 8a of the said upper ballast tank at the other side of the tanker.

In fig. 3 the same reference numerals have been used as in fig. 2.

In fig. 3 the "knuckle" 11 is slightly shifted upwards in comparison with the embodiment of fig. 2, i.e. located slightly above half height in order to reduce the amount of ballast (e.g. water) and to increase the amount of wing cargo volume 9. Further, in comparison with fig. 2, the bottom 3 is slightly shifted upwards, which improves the total performance, in particular with respect to tank cleaning, accessibility and construction

optimization.

In fig. 4 a further embodiment of the carrier design according to the invention is shown. In this figure the same references have been used as in the previous figures to indicate both the tanks and separation walls. In this embodiment the requirements of simple construction and reduced use of material have been met. As is clear from the figure most separation walls are straight and vertical or horizontal.

Although the tanker of the invention is intended to carry

(crude) oil, it will be appreciated by those skilled in the art that the possibility of carrying different bulk cargoes on combination trades is not eliminated at all by the tanker design of the present invention and that, if desirable, hatches can be fitted on deck in any way suitable for the purpose (not shown for reasons of clarity). Further, it will be appreciated by those skilled in the art, that, in contrast to the known double hull carrier designs, the tanker of the invention has no small enclosed spaces where hydrocarbon vapours can accumulate and that both the ballast and cargo tanks can be easily inerted and ventilated which will prevent explosion and suffocation hazards.

It will also be appreciated by those skilled in the art that in case of penetration of the lower inboard cargo wing tank or penetration of the bottom cargo tank, the higher pressure of the sea water will first cause a water inflow, which in case of bottom damage provides a safe layer in the tank and prevents any oil outflow. (The oil head is less than the water head.)

In case of side damage of the lower inboard cargo wing tank, a slow oil outflow may occur. In the latter case it has appeared that the application of a cargo transfer system as described in the foregoing is effective.

It will alsυ be appreciated by those skilled in the art that the bottom cargo tank can be connected in any suitable manner to at least one lower inboard cargo wing tank. In this manner, operational and structural improvements are achieved.

Various modifications of the invention will become apparent to those skilled in the art from the foregoing description and

accompanying drawings.

Such modifications are intended to fall within the scope of the appended claims.

Claims

C L A I M S

1. A tanker for carrying a bulk cargo such as (crude) oil or for carrying different bulk cargoes on combination trade, comprising at least a longitudinally extending centre cargo tank, at least a bottom tank below the centre cargo tank and wing tanks located on either side of the centre cargo tank and separated from the centre cargo tank by a longitudinal structure, characterized in that an additional longitudinal structure is fitted in each wing tank forming an upper ballast tank with a lower double side and a lower inboard cargo tank.

2. The tanker as claimed in claim 1, characterized in that the additional longitudinal structure is a bulk head.

3. The tanker as claimed in claims 1 or 2 characterized in that the additional longitudinal structure comprises a horizontal barrier and a vertical barrier.

4. The tanker as claimed in claim 3, characterized in that the additional longitudinal structure is a horizontal barrier near half height and a vertical barrier near the side shell.

5. The tanker as claimed in any one of claims 1-4, characterized in that the longitudinal structure is straight.

6. The tanker as claimed in any one of claims 1-4, characterized in that the longitudinal structure comprises at least one

"knuckle".

7. The tanker as claimed in claim 6, characterized in that the

"knuckle" is located near half height.

8. The tanker as claimed in any one of claims 1-7, characterized in that the bottom cargo tank is connected to at least one lower inboard cargo wing tank.

9. The tanker as claimed in any one of claims 1-8, characterized in that a cargo transfer system is installed which in case of tank penetration transfers cargo from a cargo tank to a ballast tank or a storage tank.