METHOD AND SYSTEMS FOR IMPROVING DAMAGE STABILITY OF A SHIP

Abstract

A foamable composition for injecting in a region of a ship, for example to prevent and/or reduce water ingress and/or progressive flooding in the ship so as to improve damage stability of the ship, is foamable to form a foam and is dissolvable in a removal composition. The provision of a foam, which can be dissolved by application of a removal composition, e.g., a solvent, may improve ease of removal of the foam, and therefore may reduce the cost and/or speed of reinstatement of the ship. The present invention also relates to a method of improving damage stability of a ship, the method comprising identifying one or more regions of the ship where injection of a material may lead to increase in ship stability, the material being impermeable to water and/or being capable of preventing migration of water.

Claims

1-54. (canceled)

55. A method of preventing and/or reducing water ingress and/or progressive flooding in a ship, comprising injecting in a region of a ship a foamable composition, the composition being foamable to form a foam, the foam being dissolvable in a removal composition.

56. The method of claim 55, comprising displacing water and/or improving buoyancy and/or stability of a ship.

57. The method according to claim 55, wherein the removal composition comprises an aqueous acid solution.

58. The method according to claim 55, wherein the foamable composition comprises a formaldehyde resin.

59. The method according to claim 55, wherein the foamable composition comprises a resin represented by Formula (I): ##STR00006## wherein X is selected from the group consisting of: (i) a urea derivative; (ii) an optionally substituted aromatic ring, optionally containing one or more heteroatoms; or (iii) an optionally substituted melamine derivative.

60. The method according to claim 55, wherein the foamable composition comprises one or more selected from the group of a urea-formaldehyde resin, a phenol-formaldehyde resin, a resorcinol-formaldehyde resin, and a melamine-formaldehyde resin.

61. The method according to claim 55, wherein the foamable composition is provided as two or more separate components configured to be mixed and reacted in the region of the ship in which foam is to be injected.

62. The method according to claim 61, wherein a first composition is provided in a first container, wherein the first composition comprises or consists essentially of a polymer or prepolymer.

63. The method according to claim 61, wherein a second composition is provided in a second container, wherein the second composition comprises or consists of a crosslinking composition.

64. The method according to claim 63, wherein the cross-linking composition comprises or consists essentially of an aqueous acid solution.

65. A method of improving stability of a ship, the method comprising identifying one or more regions of the ship where injection of a material may lead to an increase in ship stability, the material being impermeable to water and/or being capable of preventing migration of water.

66. A method according to claim 65, wherein the material comprises a foamable composition.

67. A method according to claim 65, comprising providing a first composition comprising or consisting of a polymer or prepolymer.

68. A method according to claim 67, comprising providing a second composition comprising or consisting of a crosslinking composition.

69. A method according to claim 68, comprising mixing and/or reacting the first composition and the second composition in a region of the ship where the foamable composition is to be injected.

70. A method according to claim 65, comprising the preliminary step of determining a location suitable for injection of the material following damage to a region of the ship.

71. A method according to claim 65, comprising performing a vulnerability analysis.

72. A method according to claim 71, comprising mapping and/or modelling an internal geometry and/or space of a ship, further comprising dividing the internal geometry and/or space of the ship into a plurality of compartments, further comprising mapping and/or modelling one or more spaces and/or elements within each of the compartments, wherein the spaces and/or elements comprise non-buoyant volumes, and openings.

73. A method according to claim 65, comprising determining the likelihood of the ship surviving damage to one or more compartments.

74. A method according to claim 65, comprising identifying and/or ranking compartments where injection of the material leads to maximum stability recovery.

75. A method according to claim 65, comprising determining an amount and/or volume of the material to be injected for which buoyancy restoration per volume of material will lead to maximum increase in stability.

76. A system for improving stability of a ship, the system comprising: a computer system configured to determine a location suitable for injection of a material following an emergency event; and a user interface configured to allow a user to inject a material in a region of a ship, the material being impermeable to water and/or being capable of preventing migration of water.

77. A system according to claim 76, wherein the material comprises a foamable composition.

78. A system according to claim 76, wherein the computer system is configured to determine the likelihood of the ship surviving damage to one or more compartments of the ship.

79. A system according to claim 76, wherein the computer system is configured to identify and/or rank regions and/or compartments of the ship where injection of the material leads to maximum stability recovery.

80. A system according to claim 76, wherein the computer system is configured to determine an amount and/or volume of the material to be injected for which buoyancy restoration per volume of material will lead to maximum increase in stability.

81. A system according to claim 76, wherein the user interface is configured to allow a user to select one or more compartments where foam is to be injected.

82. A method of removing a foam from a region of a ship, the method comprising contacting the foam with a removal composition.

83. A method according to claim 82, wherein the method comprises at least one of the step selected from: (i) applying the removal composition to the foam; (ii) spraying the removal composition onto the foam; and (iii) injecting the removal composition into one or more portions of the foam.

84. A method according to claim 82, wherein the removal composition comprises an aqueous acid solution.

85. A foamable composition, the composition being foamable to form a foam, the foam being dissolvable in a removal composition, the foamable composition comprising a formaldehyde resin.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0193] Embodiments of the invention will now be given by way of example only, and with reference to the accompanying drawing, which are:

[0194] FIG. 1 a schematic representation of an example of a vulnerability assessment;

[0195] FIGS. 2 and 3 an illustration of design vulnerability with reference to MV Estonia;

[0196] FIG. 4 a schematic representation of a method for improving stability of a ship according to an embodiment of the present invention;

[0197] FIG. 5 a schematic representation of a system for improving stability of a ship according to an embodiment of the present invention;

[0198] FIGS. 6 and 7 a perspective view of an embodiment of the injection system of FIG. 5;

[0199] FIGS. 8-12 a first embodiment of a sensitivity analysis and implementation of a system and method according to the present invention, for a first type of vessel;

[0200] FIGS. 13-19 a second embodiment of a sensitivity analysis and implementation of a system and method according to the present invention, for a second type of vessel; and

[0201] FIGS. 20-25 a third embodiment of a sensitivity analysis and implementation of a system and method according to the present invention, for a third type of vessel.

DETAILED DESCRIPTION OF DRAWINGS

[0202] As used herein, the term “vulnerability” is understood to refer to the probability that a ship may capsize within a certain time when subjected to any feasible flooding case.

[0203] Referring to FIG. 1, there is shown a schematic representation an example of a vulnerability assessment.

[0204] The basic example shown in FIG. 1 illustrates a ship 10, and depicts 3 possible flooding cases C1 (rear), C2 (front) and C12 (front and rear) following damage to the ship 10.

[0205] Each event is associated with a known frequency of occurrence, which is available through statistics. In the example shown in FIG. 1, the probability p.sub.1 of C1 (damage to rear) is 50%, the probability p.sub.2 of C2 (damage to front) is 35%, and the probability p.sub.3 of C12 (damage to front and rear) is 15%.

[0206] Each event is also associated with a known probability that the event will cause loss of the ship 10, e.g., within a predetermined time period (in this example 3 hours). In the example shown in FIG. 1, the probability c.sub.1 of loss following C1 (damage to rear) is 72%, the probability c.sub.2 of loss following C2 (damage to front) is 1%, and the probability c.sub.3 of loss following C12 (damage to front and rear) is 99%.

[0207] As shown in FIG. 1, the probability of loss in each scenario is represented by a corresponding triangle c.sub.1, c.sub.2 and c.sub.3. Each triangle relates to the probability of loss following damage to a specific ship compartment or specific compartments. The location and base of each triangle relate to the size and location of the damage.

[0208] A red (R) triangle indicates that the damage depicted by the base of the triangle will likely result in loss of the ship. A yellow (Y) triangle indicates that the damage depicted by the base of the triangle may or may not result in loss of the ship. A green (G) triangle indicates that the damage depicted by the base of the triangle will likely not result in loss of the ship.

[0209] Based on this information, the vulnerability to collision flooding of the example of FIG. 1 is:

V=0.5×0.72+0.35×0.01+0.15×0.99=51.2%

[0210] FIGS. 2 and 3 illustrate design vulnerability of a concrete example, the MV Estonia, denoted 100, which sank in 1994.

[0211] FIG. 2 illustrates design vulnerability of MV Estonia 100 operated under normal conditions, that is, following the normal guidelines for operation. As can be seen in the plan view 110 of FIG. 2, under normal conditions, a number of watertight (WT) doors represented by squares are closed (WTC).

[0212] FIG. 3 illustrates design vulnerability of MV Estonia 100 as operated at the time of her loss. As can be seen in the plan views 110a and 110b of FIG. 3, as operated at the time of her loss, watertight doors comprise a number of doors that are closed (WTC) and a number of doors that are open (WTO). These open doors can cause “progressive flooding” in an emergency event, allowing water to flow from one compartment to another compartment.

[0213] In the configuration of FIG. 3, the vulnerability of the vessel was at 68%, i.e., 3.5 times higher than her design vulnerability of 19% depicted in FIG. 2.

[0214] Referring to FIG. 4, there is shown a schematic representation of a method 200 for improving stability of a ship according to an embodiment of the present invention.

[0215] The method 200 comprises mapping and/or modelling 210 an internal geometry and space of the ship. It will be understood that the mapping and/or modelling of the ship will be specific to the ship under study.

[0216] Typically, step 210 comprises dividing the ship into a plurality of compartments, and mapping and/or modelling the plurality of compartments.

[0217] Step 210 typically comprises mapping and/or modelling the space(s) and/or element(s) within each of the compartments. The space(s) and/or element(s) may comprise equipment including non-buoyant volumes such as tanks, machinery, pipes, and/or other equipment. By such provision an accurate model of the volume available for potential flooding can be created and/or designed. Step 210 typically comprises mapping and/or modelling openings between compartments, such as doors, windows, stairwells, or the like, may cause progressive flooding to a critical region of the ship. By such provision, an accurate model of the potential for progressive flooding can be created and/or designed.

[0218] The method 200 comprises performing a vulnerability analysis 220. Typically, step 220 comprises calculating the probability that a ship may capsize within a certain time, based on the map and/or model created in step 210, and on a number of conceivable scenarios involving damage and/or flooding to one or more compartments.

[0219] The method 200 comprises performing a sensitivity analysis 230. Typically step 230 comprises identifying and/or ranking compartments where injection of foam may lead to an increase in ship stability.

[0220] In this embodiment, the method comprises determining 240 an optimum amount and/or volume of foam to be injected to achieve a predetermined level of increase in ship stability. In this embodiment, step 240 comprises determination of an amount and/or volume of foam to be injected for which buoyancy restoration per volume of foam will lead to maximum increase in stability.

[0221] The method 200 comprises detecting 250 damage to a region of a ship, e.g., to one or more compartments.

[0222] Following detection 250 of damage to one or more compartments, the method 200 comprises taking an action 260. In this embodiment, step 250 involves a user, such as a crew member, taking an action. The action is typically based on the vulnerability analysis and sensitivity analysis performed in steps 230 and 240.

[0223] If the vulnerability analysis and sensitivity analysis reveal a high risk that the ship may be lost following damage, the action taken by the user in step 260 will typically be to inject foam as shown in step 270 in one or more compartments which are most likely to result in the ship being saved.

[0224] In one embodiment, step 270 comprises injecting foam in the damaged compartment or compartments. This may be adequate if damage occurs in a critical compartment or critical compartments in order to displace water therefrom and improve stability, or if damage occurs in a compartment or compartments in fluid communication with a critical compartment in order to prevent water from entering the critical compartment.

[0225] In another embodiment, step 270 comprises injecting foam in one or more compartments adjacent to and/or in fluid communication with the damaged compartment or compartments. This may be adequate if damage occurs in a non-critical compartment or non-critical compartments in fluid communication with a critical compartment or critical compartments. In such instance, while injection of foam in the non-critical compartment or non-critical compartments may not be required to maintain the overall stability of the ship, injection of foam in the one or more compartments adjacent to and/or in fluid communication with the damaged compartment or compartments prevents water ingress into and/or displaces water from the critical compartment or critical compartments. This may ensure survival of the ship, while minimising the amount of foam injected in the ship, thereby reducing costs and increasing the rapidity of subsequent reinstatement of the ship.

[0226] In an alternative embodiment, the action taken by the user in step 260 will typically be not to inject foam 280 in any compartment, e.g., either in a damaged compartment or compartments, or in any compartment or compartments in fluid communication with the damaged compartment or compartments. This may be adequate if damage occurs in a non-critical compartment or non-critical compartments. Since such a scenario would not compromise the overall stability of the ship and would not lead to the loss of the ship, injection of foam is not required. Therefore, avoiding systematic injection of foam following damage to a region of the ship may reduce costs, and substantially quicker subsequent reinstatement of the ship.

[0227] Referring to FIG. 5, there is shown a schematic representation of a system 300 for improving stability of a ship according to an embodiment of the present invention.

[0228] The system 300 comprises a computer system 310 configured to determine a location suitable for injection of a foaming composition following an emergency event.

[0229] The computer system 310 comprises and/or is equipped with a map and/or model 311 of the ship, e.g. a map and/or model of an internal geometry and/or space of the ship.

[0230] The computer system 310 comprises and/or is equipped with data 312 representing one of more ship characteristics. The one or more ship characteristics may comprise overall length, length between perpendiculars, breadth, subdivision draught, lightweight, deadweight, total passengers, and/or total crew.

[0231] The computer system 310 is configured to determine the likelihood of the ship surviving damage to one or more compartments, and/or to identify and/or rank compartments where injection of foam may lead to maximum stability recovery.

[0232] The computer system 310 is configured to determine a desired and/or minimum amount and/or volume of foam to be injected to achieve a predetermined increase in ship stability. In an embodiment, the computer system is configured to determine an amount and/or volume of foam to be injected for which buoyancy restoration per volume of foam will lead to maximum increase in stability.

[0233] The system 300 comprises a detection system 340 which may comprise or consist of one or more sensors 341 configured to detect damage to a region of a ship, e.g., to one or more compartments. In this embodiment, each critical compartment is equipped with a sensor 341.

[0234] The system 300 comprises a user interface 320 configured to allow a user to inject a foamable composition in a selected region of a ship. The user interface 320 is configured to allow a user to select one or more compartments where foam is to be injected.

[0235] The system 300 comprises an injection system 330 for injecting foam in one or more compartments.

[0236] In this embodiment, the user interface 320 is in connected to and/or is in communication with the computer system 310, the detection system 340 and the injection system 330. However, in other embodiments, the user system may be connected to and/or may be in communication with the injection system, while the computer system 310 and/or the detection system 340 may be distinct from the user interface 320. In such instance, a user may use the computer system 310 to obtain access information and data regarding the vulnerability and sensitivity analysis in order to take an action 260.

[0237] In an embodiment, the computer system 310 is connected to and/or is in communication with the detection system 340. In such instance, the computer system may be configured to recommend and/or propose an action to be taken by a user, based on the damage detected by the detection system 340, and the vulnerability and sensitivity analysis provided in the computer system 310.

[0238] An embodiment of the injection system 330 is best shown in FIGS. 6 and 7.

[0239] The injection system 330 comprises containers 331 and 332. Container 331 is configured to store a first composition comprising a polymer or prepolymer, such as a formaldehyde resin. Container 332 is configured to store a second composition comprising a crosslinking composition such as a solution of an acid, e.g. a weak acid, in water.

[0240] The injection system 330 system comprises first pump 333 associated with first container 331, and second pump 334 associated with second container 332.

[0241] The injection system 330 comprises a network of pipes 370 configured to deliver first and second compositions to a number of compartments 351,352,353,354. In this embodiment, the network of pipes 370 is configured to deliver first and second compositions to a number of compartments 351,352,353,354 from first container 331 and second container 332. However, it will be appreciated that in other embodiments, each compartment may be provided a dedicated first and second containers 331,332 and corresponding network of pipes 370. Any suitable arrangement regarding the number of containers and associated conduits for delivering foam to the various compartments may be envisaged, depending on the size of the vessel, size of the compartments, spatial restrictions, etc.

[0242] The injection system 330 comprises discharge devices 361-367, in this embodiment in the form of nozzles, for discharging the foaming composition.

[0243] The injection system 330 comprises a gas injection mechanism XXX for providing and/or injecting a gas, e.g., air, carbon dioxide, nitrogen, or the like, to foam and/or to help foam of the composition. In this embodiment, the system 330 comprises a compressor (not shown), configured to supply a gas, e.g. air, in the stream of the first composition and/or second composition.

[0244] Referring to FIGS. 8-12, there is shown a first embodiment of a sensitivity analysis and implementation of a system and method according to the present invention for a first type of vessel, namely a small RoPax ferry operating within European coastal waters. This vessel can accommodate up to 550 passengers and is operated by a total of 30 crew members. Lifesaving appliances are provided for all 550 persons onboard for domestic voyage, as a Class B vessel according the EU passenger ship directive 2009/45/EC. The vessel has a large hold that spans the length of the vessel in order to accommodate storage and drive through operations of up to a total of 85 cars. Accommodation for passengers is located within the vessel's superstructure although no cabins are provided due to short turnaround times.

[0245] The main characteristics of the vessel are as given in table 1.

TABLE-US-00001 TABLE 1 Small ROPAX Properties Main Particulars Length Overall 89.48 m Length Between Perpendiculars 81.8 m Breadth 16.4 m Design Draught 3.4 m Number of Passengers 550 Number of Crew 30 Cars 85 Displacement 3434.8 t Deadweight 740 DWT Service Speed 16.3 Kn

[0246] A computational model 410 of the vessel design, as shown in FIG. 8, was generated in order to conduct damage stability calculations using relevant stability software. The vessel's internal arrangements including rooms, compartments and tanks were also modelled and all relevant openings liable to affect the vessel's range were defined.

[0247] The vessel has been divided into a total of 12 independent watertight compartments as shown in the model 420 of FIG. 9.

[0248] Damage stability calculations according to SOLAS2009 (MSC.216(82)) were conducted in order to ascertain the safety level of the vessel and also identify potential safety critical areas within the design. The required safety level, as represented by the required subdivision index R, was calculated in accordance to regulation 6 and as outlined below in Equation (1):

[00001]$\begin{array}{cc}R=1-\frac{5000}{Ls+2.5N+15225}& \mathrm{Eq}\left(1\right)\end{array}$

[0249] Where

[0250] L.sub.S=Subdivision Length=89.1 m;

[0251] N=N.sub.1+N.sub.2=580;

[0252] N.sub.1=Persons in lifeboats=580;

[0253] N.sub.2=Persons in excess of N.sub.1=0.

[0254] Based on these parameters the required subdivision index R for this vessel was found to be R=0.71.

[0255] The vessel's attained subdivision index A was calculated in accordance with SOLAS 2009 regulation 7. As required by this process the vessel was assessed over three loading conditions as outlined in Table 2 below:

TABLE-US-00002 TABLE 2 Displacement Draught GM KG Loading Condition (tonne) (m) (m) (m) Light Service Draught 2728 2.845 2.374 7.584 Partial Subdivision 3196 3.235 1.863 7.443 Draught Deepest Subdivision 3348.79 3.43 1.704 7.338 Draught

[0256] The results of this process are summarised in Table 3 below:

TABLE-US-00003 TABLE 3 Partial & Final Attained Indices - Acc. SOLAS 2009 Ballast (dl) 0.99 Partial Load (dp) 0.957 Scantling (ds) 0.933 Attained Subdivision Index (A) 0.955 Required Subdivision Index (R) 0.71

[0257] In order to ascertain where and when it would be best to implement the system of the present invention, it was first necessary to identify high risk areas within the vessels design. The results of the damage stability assessment provide this information and this can be viewed rather transparently using the diagram presented in FIG. 10. Here the survivability factors for varying damage extents are displayed in a colour coded manner where green (G) represents a survivability factor S=1, yellow (Y) a survivability factor 0<S<1, and red (R) a survivability factor S=0.

[0258] The results presented in FIG. 10 are those that were found considering maximum penetration damages. In this case safety critical design spots have been identified in damages involving compartments 6, 9 & 10. As such the application of foam injection would be best suited to these compartments as this will yield the highest risk reduction. In order to enhance the efficiency of the expanding foam system it was necessary to consider the volume of foam required to sufficiently reduce the level of risk. It was therefore necessary to establish the nature of the relationship between volume and risk. In order to establish this relationship, firstly, the level of risk inherent to each compartment space needed to be found. This was done through the calculation of the local attained index values of each of the primary 56 spaces. With these values known the effect of implementing the expanding foam system in each space could be found. This was achieved through consideration of the remaining level of risk after having “saved” the respective volumes of each space. This remaining level was risk was calculated as highlighted in equation 2.

R=1−Ai.sub.n  Eq (2)

[0259] Where Ai is the local attained index; [0260] n is the space under consideration; and [0261] R is the remaining level of risk.

[0262] The reduction in risk was then calculated for increasingly larger volumes as to establish how the rate of change in risk varied with increasing volume. This then enable a graph depicting the relationship between risk and volume to be plotted as shown in FIG. 11.

[0263] On the basis of the risk/volume function shown in FIG. 11, a total volume of 250 m.sup.3 of foam was identified as the optimum quantity for this vessel, as this corresponds to the point of inflexion of the curve.

[0264] Having identified vulnerabilities within the vessel's design and having established the necessary parameters for the application of the present method and system, the vessel was re-evaluated in order to ascertain the level of risk reduction offered by the system. This process involved re-simulating the high risk damage cases taking into account the effects of the system of the present invention through altering the permeability of the selected safety critical compartments according to the volume of foam applied. The results of this process are summarised in Table 4.

TABLE-US-00004 TABLE 4 Partial Attained Indices - Acc. SOLAS 2009 (DSRD Active) Ballast (dl) 0.999 Partial Load (dp) 0.99 Scantling (ds) 0.98 Attained Subdivision Index (A) 0.992

[0265] The results in this case show a total risk reduction of 350%. This is reflected in FIG. 12 where the local survival indices can be compared with the initial condition shown in FIG. 10.

[0266] Referring to FIGS. 13-18, there is shown a second embodiment of a sensitivity analysis and implementation of a system and method according to the present invention for a second type of vessel, namely a medium size RoPax ferry operating within European coastal waters. This vessel can accommodate up to 700 passengers and is operated by a total of 43 crew members. Lifesaving appliances are provided for all 743 persons onboard for domestic voyage, as a Class B vessel according the EU passenger ship directive 2009/45/EC. The vessel's main cargo hold is designed for both easy and fast cargo handling with loading and unloading taking place at both the bow and stern (drive through operations). Accommodation for passengers is located within the vessel's superstructure although no cabins are provided due to short turnaround times.

[0267] The main characteristics of the vessel are as given in table 5.

TABLE-US-00005 TABLE 5 Main Particulars Length Overall 117.9 m Length Between Perpendiculars 111.45 m Subdivision Length 115.5 m Breadth 19.2 m Design Draught 4.8 m Number of Passengers 700 Number of Crew 45 Gross Tonnage 9058 Deadweight 1434 Service Speed 19.2 Kn Main Engine 8000 kW

[0268] A computational model 510 of the vessel design, as shown in FIG. 13, was generated in order to conduct damage stability calculations using relevant stability software.

[0269] The vessel's internal arrangements including rooms, compartments and tanks were also modelled as shown in model 520 of FIG. 14 and all relevant openings liable to affect the vessel's range were defined.

[0270] The vessel has been divided in to a total of 14 watertight compartments below the bulkhead deck as shown in the model 530 of FIG. 15.

[0271] Damage stability calculations were conducted as per Equation (1) above, in which, in this embodiment:

[0272] L.sub.S=Subdivision Length=115.5 m;

[0273] N=N.sub.1+N.sub.2=745;

[0274] N.sub.1=Persons in lifeboats=745;

[0275] N.sub.2=Persons in excess of N.sub.1=0.

[0276] Based on these parameters the required subdivision index R for this vessel was found to be R=0.71.

[0277] The Vessel's attained subdivision index A was calculated in accordance with SOLAS 2009 regulation 7. As required by this process the vessel was assessed over three loading conditions as outlined in Table 6 below:

TABLE-US-00006 TABLE 6 Displacement Draught GM KG Loading condition (Tonne) (m) (m) (m) Light Service Draught 5,226.50 4.33 1.95 8.94 Partial Subdivision 5,758.80 4.64 2.13 8.84 Draught Deepest Subdivision 6,127.60 4.85 2.27 8.61 Draught

[0278] The subdivision of the vessel was divided into a total of 14 damage zones, as shown in FIG. 16, and a total 1200 damage scenarios were assessed.

[0279] The results of this process are summarised in Table 7 below:

TABLE-US-00007 TABLE 7 Partial & Final Attained Indices - Acc. SOLAS 2009 Ballast (dl) 0.95 Partial Load (dp) 0.92 Scantling (ds) 0.91 Attained Subdivision Index (A) 0.92 Required Subdivision Index (R) 0.73

[0280] The results presented in Table 7 show a large deviation between the required index and the vessel's attained index value.

[0281] Despite the vessel's high attained index value several safety critical cases were identified. The vessel's risk profile along with the local indices calculated, as shown in FIG. 17, shows a concentration of loss scenarios in damages located towards the aft end of the vessel.

[0282] FIG. 17 highlights that the vessel has particular vulnerabilities in respect of damage cases involving compartments 2, 3 & 4.

[0283] Having identified appropriate spaces for application of the system and method of the present invention, the most efficient volume of foam to be utilised was calculated. This was achieved through plotting volume as a function of risk, as shown in FIG. 18, and by taking the point of inflection of the function as the optimum quantity.

[0284] On the basis of the function shown in FIG. 18, a total volume of 300 m.sup.3 was utilised in the case of this vessel. Table 8 below provides a summary of each space subject to the application of the system along with the volume of expanded foam applied in each case and the remaining volume post application.

TABLE-US-00008 TABLE 8 Expanded Volume of Compartment ID Volume (m{circumflex over ( )}3) Foam Applied (m{circumflex over ( )}3) Steering Gear Room 317 300 Void Space 15 350 300 Auxiliary Engine Room 805 300 Cooling Systems Room 387 300 Void Space Number 8 353 300 Fin Stabilizer Room 51 48

[0285] Having applied the present system to the loss scenarios identified from the initial assessment the vessel was re-assessed in order to produce a new attained index value. The results of this process are summarised in Table 9.

TABLE-US-00009 TABLE 9 Partial Attained Indices - Acc. SOLAS 2009 (DSRD Active) Ballast (dl) 0.97 Partial Load (dp) 0.95 Scantling (ds) 0.94 Attained Subdivision Index (A) 0.95

[0286] FIG. 19 illustrates the improvements made by highlighting the change in survival factors. In particular, it can be seen by comparing FIG. 17 and FIG. 18 that the survivability factor was greatly increased by the system of the present invention.

[0287] Referring to FIGS. 20-25, there is shown a third embodiment of a sensitivity analysis and implementation of a system and method according to the present invention for a third type of vessel, namely a large RoPax ferry operating within European coastal waters. The vessel is designed to operate on short European international voyages and is operated by a total 200 crew and has a passenger capacity of 2000 persons. The vessel has open holds to accommodate the easy on load and offload of cars, trailers and coaches located on decks 3, 5 and 6. Below the bulkhead deck the vessel is subdivided into a total of 17 watertight compartments.

[0288] The main characteristics of the vessel are as (liven in table 10.

TABLE-US-00010 TABLE 10 Main Particulars Length over all 179.7 m Length Between Perpendiculars 170 m Breadth Moulded 27.8 m Subdivision Draught 6.419 m Lightweight 12500 t Deadweight 5394 t Total Passengers 2000 Total Crew 2200

[0289] A computational model of the vessel's hull form and internal arrangement was generated for subsequent analysis using relevant stability software. This included the definition of all internal of compartmentation located within the vessel's subdivision and cargo holds and also the definition of all tanks within the vessel. Such computational model 610 is shown in FIG. 20.

[0290] The vessel has been divided in to a total of 17 watertight compartments below the bulkhead deck as shown in the model 620 of FIG. 21.

[0291] Damage stability calculations were conducted as per Equation (1) above, in which, in this embodiment:

[0292] L.sub.S=Subdivision Length=178.1 m;

[0293] N=N.sub.1+N.sub.2=2200;

[0294] N.sub.1=Persons in lifeboats=1000;

[0295] N.sub.2=Persons in excess of N.sub.1=1200.

[0296] Based on these parameters the required subdivision index R for this vessel was found to be R=0.81.

[0297] The Vessel's attained subdivision index A was calculated in accordance with SOLAS 2009 regulation 7. As required by this process the vessel was assessed over three loading conditions as outlined in Table 11 below:

TABLE-US-00011 TABLE 11 Displacement Draught GM KG Loading Condition (tonne) (m) (m) (m) Light Service Draught 13,983.00 5.39 4.15 12.02 Partial Subdivision 16,304.00 5.99 2.84 12.91 Draught Deepest Subdivision 17,971.00 6.42 2.91 12.57 Draught

[0298] The subdivision of the vessel was divided into a total of 17 damage zones, as shown in FIG. 22, and a total 3000 damage scenarios were assessed.

[0299] The results of the damage stability assessment are provided in Table 12 below:

TABLE-US-00012 TABLE 12 Partial & Final Attained Indices - Acc. SOLAS 2009 Ballast (dl) 0.98 Partial Load (dp) 0.877 Scantling (ds) 0.815 Attained Subdivision Index (A) 0.875 Required Subdivision Index (R) 0.81

[0300] As illustrated by the survival factors shown in FIG. 23, the vessel in question was designed to a two compartment standard. Loss scenarios can be identified for almost all damages comprising three compartments, and two compartment damages also carry risk in most cases. As such, this vessel calls for application of the system and method of the present invention.

[0301] As in the previous embodiments, the optimum volume of foam to be used in the present system was determined by the inflection point of the risk/volume function plotted for this vessel, as shown in FIG. 24. In this instance, the optimum volume was found to be 1600 m.sup.3.

[0302] Having applied the present system to the loss scenarios identified from the initial assessment the vessel was re-assessed in order to produce a new attained index value. The results of this process are summarised in Table 13.

TABLE-US-00013 TABLE 13 Partial Attained Indices - Acc. SOLAS 2009 (DSRS Active) Ballast (dl) 0.989 Partial Load (dp) 0.9286 Scantling (ds) 0.89 Attained Subdivision Index (A) 0.93

[0303] In this case the implementation of the present system led to a 52% risk reduction over the initial ship design.

[0304] FIG. 25 illustrates the improvements made by highlighting the change in survival factors. In particular, it can be seen by comparing FIG. 24 and FIG. 25 that the survivability factor was greatly increased by the system of the present invention.

[0305] Various modifications may be made to the embodiment described without departing from the scope of the invention.