GB2053809A - Inflatable buoyancy collars for ships - Google Patents

Abstract

A ship, especially a vessel of the Ro-Ro type, is provided around its hull, at about the level of the freeboard deck, with an inflatable collar (19) to improve stability in the event of hull damage. The collar can be stowed, when uninflated, in a recess (20) in the hull side shell with a hinged cover plate (22) to protect it, the cover plate being arranged to abut the hull and transfer heeling loads on the collar to the hull when the collar is inflated. The collar is made in sections, each section being arranged for inflation independently of the other sections. <IMAGE>

Description

SPECIFICATION Improvement of the stability of ships in a damaged condition and in particular roll-on/roll-off type ships having continuous open freeboard decks This invention relates to improvements of the stability of ships in a damaged condition and in particular Roll-on/Roll-off type ships having continuous open freeboard decks.

Due to the nature of the Roll-on/Roll-off operation it is not practical to sub-dividethe main Roll-on/ Roll-offfreeboard deck by means of bulkheads. If water gains access to the freeboard deck either through side damage, damage to the bow or stern doors, or by other means, it is very difficult to shed water from this deck overboard. This in particular applies to the condition of side damage wherein the sea gains access to the Ro-Ro freeboard deck and usually creates an unstable situation where the vessel heels with the result that water progressively collects on one side of the vessel causing progressively increasing heel leading to capsize and loss of the ship.

In the case of this type of vessel carrying passengers, there are international regulations governing the spacing of bulkheads below the freeboard deck and requiring a minimum standard of stability in the damaged condition. Aiso the margin line (which is 3 inches below the freeboard deck) should not be immersed at any point. This regulation applies to smooth water conditions but in actual operating conditions even though the margin line is not immersed it is very probable that through the side damage opening water will gain access. The vulnerability of this type of vessel to water gaining access to the freeboard deck is well known and it is generally accepted that in the absence of continuous bulkheads on the freeboard deck little can be done to the internal ship structure to improve the stability with water on the freeboard deck.

According to the present invention, there is provided around the hull at about freeboard deck level an inflatable stability collar in sections made of reinforced rubber or other suitable material, which can be inflated either automatically or manually in the event of the ship becoming unstable due to flooding of the freeboard deck as a result of side damage or for any other reason. The stability collar has the effect of increasing the waterplane area of the vessel and thereby improving the metacentric height, and it also provides buoyancy at the sides of the ship to improve static stability.

Arrangements according to the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a diagram of a typical section through a Ro-Ro type ship, Figure 2 shows diagrammatically the possible effect of side damage under operating conditions, Figure 3 is a diagram showing the provision of a stability collar according to the invention, and Figure 4 shows the collar inflated.

In Figure 1, the freeboard deck level of a Ro-Ro ship 11 is indicated at 12 and 3 inches below is the margin line 13. The operating waterline in still water is at 14 and the higher waterline that may result from damage to the hull shell is shown at 15. The chain line 16 represents the kind of waterline that may be experienced under operating conditions at sea.

In Figure 2, the vessel is assumed to have suffered side damage to the hull shell as at 17. Water gaining access through the damaged area collects on the freeboard deck 12 at 18 causing a permanent and increasing heel.

In Figure 3, the hull 11 is provided with a stability collar 19 which is shown in the uninflated stowed condition. The inflatable collar 19ean be attached to the vessel in a number of ways. In Figure 3, it is stowed in a recess 20 in the side of the ship just above the ship's fendering 21, at a vertical position appropriate to the layout of the vessel and the calculated position of the damaged waterline 15. A steel 'L'-shaped sectional cover plate 22 to protect the stowed collar is hinged on the hull at its inboard edge 23 and the stability collar, which adopts an inverted U configuration when stowed, is attached to it and also to the sidewall of the recess in the ship's hull.

Figure 4 shows the stability collar 19 in the inflated condition. The action of inflating the device automatically raises the vertical leg of the 'L'-shaped cover plate 22 into a horizontal position in which position it abuts the top horizontal wall 24 of the hull recess 20.

This provides the necessary support for the stability collar to transfer the wave and heeling forces to the ship's hull thus preventing the inflated stability collar from being detached from the ship.

The collar is made of e.g. reinforced rubber, in sections of a length to suit the dimensions of the vessel. Each section of the stability collar has independent means of inflation and can be inflated manually, or by compressors at a central damage control station. Side damage to one or more of the individual lengths of the stability collar will not affect the efficient operation of the other parts of it.

1. A ship, especially a Ro-Ro type vessel, wherein there is provided around the hull at about freeboard deck level an inflatable collar in sections made of reinforced rubber or other suitable material.

2. A ship according to claim 1, wherein the collar is stowed in the uninflated condition in a recess in the hull side shell.

3. A ship according to claim 2, wherein the collar is protected when stowed by a hinged sectional cover plate.

4. A ship according to claim 3, wherein when the collar is inflated the cover plate swings up to abut the hull in such manner as to transfer wave and heeling loads from the collar to the hull, the material of the collar being attached to both the hull and the cover plate.

5. A ship according to any one of the preceding claims, wherein each section of the collar is inflatable independently by manual means or from a centrol damage control station.

6. A ship provided with a stability collar substan

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvement of the stability of ships in a damaged condition and in particular roll-on/roll-off type ships having continuous open freeboard decks This invention relates to improvements of the stability of ships in a damaged condition and in particular Roll-on/Roll-off type ships having continuous open freeboard decks. Due to the nature of the Roll-on/Roll-off operation it is not practical to sub-dividethe main Roll-on/ Roll-offfreeboard deck by means of bulkheads. If water gains access to the freeboard deck either through side damage, damage to the bow or stern doors, or by other means, it is very difficult to shed water from this deck overboard. This in particular applies to the condition of side damage wherein the sea gains access to the Ro-Ro freeboard deck and usually creates an unstable situation where the vessel heels with the result that water progressively collects on one side of the vessel causing progressively increasing heel leading to capsize and loss of the ship. In the case of this type of vessel carrying passengers, there are international regulations governing the spacing of bulkheads below the freeboard deck and requiring a minimum standard of stability in the damaged condition. Aiso the margin line (which is 3 inches below the freeboard deck) should not be immersed at any point. This regulation applies to smooth water conditions but in actual operating conditions even though the margin line is not immersed it is very probable that through the side damage opening water will gain access. The vulnerability of this type of vessel to water gaining access to the freeboard deck is well known and it is generally accepted that in the absence of continuous bulkheads on the freeboard deck little can be done to the internal ship structure to improve the stability with water on the freeboard deck. According to the present invention, there is provided around the hull at about freeboard deck level an inflatable stability collar in sections made of reinforced rubber or other suitable material, which can be inflated either automatically or manually in the event of the ship becoming unstable due to flooding of the freeboard deck as a result of side damage or for any other reason. The stability collar has the effect of increasing the waterplane area of the vessel and thereby improving the metacentric height, and it also provides buoyancy at the sides of the ship to improve static stability. Arrangements according to the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a diagram of a typical section through a Ro-Ro type ship, Figure 2 shows diagrammatically the possible effect of side damage under operating conditions, Figure 3 is a diagram showing the provision of a stability collar according to the invention, and Figure 4 shows the collar inflated. In Figure 1, the freeboard deck level of a Ro-Ro ship 11 is indicated at 12 and 3 inches below is the margin line 13. The operating waterline in still water is at 14 and the higher waterline that may result from damage to the hull shell is shown at 15. The chain line 16 represents the kind of waterline that may be experienced under operating conditions at sea. In Figure 2, the vessel is assumed to have suffered side damage to the hull shell as at 17. Water gaining access through the damaged area collects on the freeboard deck 12 at 18 causing a permanent and increasing heel. In Figure 3, the hull 11 is provided with a stability collar 19 which is shown in the uninflated stowed condition. The inflatable collar 19ean be attached to the vessel in a number of ways. In Figure 3, it is stowed in a recess 20 in the side of the ship just above the ship's fendering 21, at a vertical position appropriate to the layout of the vessel and the calculated position of the damaged waterline 15. A steel 'L'-shaped sectional cover plate 22 to protect the stowed collar is hinged on the hull at its inboard edge 23 and the stability collar, which adopts an inverted U configuration when stowed, is attached to it and also to the sidewall of the recess in the ship's hull. Figure 4 shows the stability collar 19 in the inflated condition. The action of inflating the device automatically raises the vertical leg of the 'L'-shaped cover plate 22 into a horizontal position in which position it abuts the top horizontal wall 24 of the hull recess 20. This provides the necessary support for the stability collar to transfer the wave and heeling forces to the ship's hull thus preventing the inflated stability collar from being detached from the ship. The collar is made of e.g. reinforced rubber, in sections of a length to suit the dimensions of the vessel. Each section of the stability collar has independent means of inflation and can be inflated manually, or by compressors at a central damage control station. Side damage to one or more of the individual lengths of the stability collar will not affect the efficient operation of the other parts of it. CLAIMS

1. A ship, especially a Ro-Ro type vessel, wherein there is provided around the hull at about freeboard deck level an inflatable collar in sections made of reinforced rubber or other suitable material.

2. A ship according to claim 1, wherein the collar is stowed in the uninflated condition in a recess in the hull side shell.

3. A ship according to claim 2, wherein the collar is protected when stowed by a hinged sectional cover plate.

4. A ship according to claim 3, wherein when the collar is inflated the cover plate swings up to abut the hull in such manner as to transfer wave and heeling loads from the collar to the hull, the material of the collar being attached to both the hull and the cover plate.

5. A ship according to any one of the preceding claims, wherein each section of the collar is inflatable independently by manual means or from a centrol damage control station.

6. A ship provided with a stability collar substan tially as described with reference to Figures 3 and 4 of the accompanying drawings.