New Technologies for Fire Suppression on Board Naval Craft (FiST) Final Report Tommy Hertzberg, SP Boras, Sweden John A. Hiltz, DRDC – Atlantic Research Centre Rogier van der Wal, TNO, The Netherlands Michael Rahm, SP Boras, Sweden

Defence Research and Development Canada Scientific Report DRDC-RDDC-2015-R224 September 2015

IMPORTANT INFORMATIVE STATEMENTS This work was carried out under the Canada/Netherlands/Sweden Cooperative Science and Technology Memorandum of Understanding (dated May 2003) as Project Arrangement Number 2010-06.

Template in use: SR Advanced_Oct_Release_EN_2015-08-14.dotm © Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2015 © Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2015

Abstract This report summarizes the results of a Project Arrangement entitled “New Fire Suppression Technologies on Board Naval Ships (FiST)” carried out under the Canada/Netherlands/Sweden Memorandum of Understanding on Cooperative Science and Technology. The FiST project had three main areas of focus; 1) fixed fire suppression systems, 2) portable, manually operated fire suppression systems, and 3) firefighting on submarines. For fixed fire suppression systems, large scale fire suppression testing was carried out to determine the effectiveness of low pressure water mist systems under well ventilated conditions, the effectiveness of high pressure water mist systems in a damaged condition, and the effectiveness of using water mist in conjunction with deluge systems for the protection of ammunition storage spaces. For the damaged high pressure system, damage was simulated by reducing the number of operational nozzles, by reducing system pressure and by introducing damaged water delivery pipe segments. The results of large scale fire suppression testing of a dual agent (water mist / Novec™ 1230) system are reported. The use of water mist in conjunction with Novec™ 1230 was found to significantly reduce the levels of acid gas in the test space. The effectiveness of gaseous fire suppression agents, including Novec™ 1230 (a perfluorinated ketone), carbon dioxide and nitrogen, in suppressing or extinguishing electrical cabinet fires was investigated. This study included analysis of acid gases produced by Novec™ 1230. For portable, manually operated systems, testing focused on the evaluation of the effectiveness, toxicity and corrosiveness of hand-held aerosol fire suppression agents. Other technologies, including compressed air foam systems, the use of additives in water mist systems and cool gas generator technology for use in fire suppression systems, are also reviewed and discussed.

Significance to Defence and Security The full scale fire suppression testing results for low and high pressure water mist systems provide Royal Canadian Navy and engineering support personnel with information relevant to the selection and design of water-based fire suppression systems for new build naval vessels. The results are discussed with respect to the strengths and weaknesses of the systems and how, if they are installed on ships, they can be used to ensure optimum fire protection. The testing of damaged systems provides knowledge of the residual capacity of these systems and how this can be optimized. The evaluation of Novec™ 1230 provides information on, in addition to its effectiveness, the potential problems arising from the thermal degradation products (especially hydrogen fluoride (HF)) of this gaseous agent and approaches to reducing hazards associated with its use. The dual water mist / Novec™ 1230 fire suppression system testing indicated that HF levels can be significantly reduced if used in conjunction with a water-based suppression system. The electrical cabinet fire suppression testing showed that ventilation can be used to reduce HF levels in a space where the agent have been used. This work also indicates that re-entry procedures to spaces where ‘new’ fire suppression agents, such as Novec™ 1230, are used should be reviewed and changed to minimize hazards to the ship’s crew. The results of the testing of hand-held aerosol fire suppression units provides new information on the effectiveness of these agents as a first responder device and hazards associated with their use. These include toxicity and the corrosivity of the aerosols when in contact with metal surfaces and computer circuit boards. DRDC-RDDC-2015-R224

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Résumé Le présent rapport résume les résultats d’une entente de projet intitulée « Nouvelles technologies d’extinction d’incendie à bord des navires militaires (FiST) » s’inscrivant dans le protocole d’entente Canada/Pays Bas/Suède sur la recherche coopérative en matière de science et technologie. Le projet FiST comporte trois domaines d’intérêt particulier : 1) systèmes fixes d’extinction d’incendie, 2) systèmes d’extinction d’incendie manuels portatifs et 3) systèmes de lutte contre l’incendie à bord des sous-marins. Pour ce qui est des systèmes fixes d’extinction d’incendie, des essais à grande échelle ont été réalisés afin de déterminer l’efficacité des systèmes à brouillard d’eau à basse pression dans un endroit bien aéré, celle des systèmes à brouillard d’eau à haute pression en mauvais état et celle de l’utilisation d’un brouillard d’eau combiné à des systèmes de type déluge pour protéger les aires de stockage des munitions. Dans le cas d’un système à haute pression en mauvais état, on a simulé les dommages en réduisant le nombre de lances d’incendie opérationnelles, en réduisant la pression du système et en ajoutant des segments de conduites d’eau endommagées. On présente les résultats des essais d’extinction d’incendie à grande échelle sur un système utilisant deux agents (brouillard d’eau / NovecMC 1230). L’utilisation d’un brouillard d’eau conjuguée à du NovecMC 1230 permet de réduire considérablement le niveau des gaz acides dans l’espace d’essai. L’efficacité des agents d’extinction d’incendie gazeux, incluant le NovecMC 1230 (cétone perfluorée), le dioxyde de carbone et l’azote, pour la suppression ou l’extinction d’incendie dans une armoire électrique, a été étudiée. L’étude comportait une analyse des gaz acides produits par le Novec MC 1230. Dans le cas des systèmes manuels portatifs, les essais ont porté essentiellement sur l’évaluation de l’efficacité, de la toxicité et de la corrosivité des agents d’extinction d’incendie en aérosol. D’autres technologies, notamment les systèmes à mousse à air comprimé, les additifs utilisés dans les systèmes à brouillard d’eau et les générateurs de gaz à froid employés dans les systèmes d’extinction d’incendie, sont également examinées.

Importance pour la défense et la sécurité Les résultats de l’essai des systèmes à brouillard d’eau à basse pression et à haute pression pour l’extinction d’incendie à grande échelle a fourni à la Marine royale du Canada et au personnel de soutien en ingénierie l’information pertinente sur le choix et la conception des systèmes d’extinction d’incendie à base d’eau pour les navires militaires nouvellement construits. On a examiné les résultats en tenant compte des points forts et des faiblesses des systèmes et de la manière dont on peut les utiliser pour assurer une protection optimale contre les incendies, lorsqu’ils sont installés à bord des navires. L’essai des systèmes endommagés permet de comprendre la capacité résiduelle de ces systèmes et la façon dont on peut l’optimiser. L’évaluation du NovecMC 1230 nous renseigne non seulement sur son efficacité, mais également sur les problèmes potentiels découlant des produits de dégradation thermique [particulièrement le fluorure d’hydrogène (HF)] de cet agent gazeux et des démarches visant à réduire les risques associés à son utilisation. L’essai du système d’extinction d’incendie utilisant deux agents (brouillard d’eau et NovecMC 1230) a indiqué que l’utilisation d’un brouillard d’eau combiné à du NovecMC 1230 permet de réduire considérablement le niveau de HF. L’essai portant sur l’extinction d’incendie dans une armoire électrique a montré que la ventilation permet de réduire ii

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le niveau de HF là où l’agent a été utilisé. Les travaux montrent également que les procédures de réintégration là où on a utilisé de « nouveaux » agents d’extinction d’incendie, comme le NovecMC 1230, devraient être examinées et modifiées afin de minimiser les risques pour l’équipage du navire. Les résultats des essais sur les appareils portatifs contenant des agents d’extinction d’incendie en aérosol nous informent sur l’efficacité de ces agents comme outils pour les premiers intervenants et sur les risques associés à leur utilisation. Ceux-ci comprennent la toxicité et la corrosivité des aérosols, lorsqu’ils sont en contact avec des surfaces métalliques et des cartes de circuits imprimés d’ordinateur.

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Table of Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i Significance to Defence and Security . . . . . . . . . . . . . . . . . . . . . . i Résumé . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Importance pour la défense et la sécurité . . . . . . . . . . . . . . . . . . . .

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Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . Fixed Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Water Mist and Influence on Fire . . . . . . . . . . . . . . . . . . . 3.2 Water Mist Suppression Effectiveness in Battle-Damaged Conditions . . . . . 3.2.1 Threat Definition . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Effectiveness of Low Pressure Water Mist Systems . . . . . . . . . 3.2.3 Effectiveness of Damaged High Pressure Water Mist Systems . . . . . 3.2.4 Effectiveness in Breached Compartments . . . . . . . . . . . . . 3.2.5 Ruggedizing Methods . . . . . . . . . . . . . . . . . . . . 3.2.6 Design: High Pressure Systems Versus Low Pressure Water Mist Systems . 3.2.6.1 Differences Between High and Low Pressure Systems . . . . . 3.2.7 Survivability Aspects . . . . . . . . . . . . . . . . . . . . 3.2.7.1 System Integration . . . . . . . . . . . . . . . . . . 3.2.7.2 Mass . . . . . . . . . . . . . . . . . . . . . . . 3.2.7.3 Vulnerable Area . . . . . . . . . . . . . . . . . . . 3.2.7.4 Material Use . . . . . . . . . . . . . . . . . . . . 3.2.8 Pressure and Pressure Drop . . . . . . . . . . . . . . . . . . 3.2.9 Experimental Blast Resistance . . . . . . . . . . . . . . . . . 3.2.10 Finnish Testing on Damaged Water Mist System . . . . . . . . . . 3.2.11 High Versus Low Pressure Systems . . . . . . . . . . . . . . . 3.3 Special Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Compressed Air Foam Systems (CAFS) . . . . . . . . . . . . . . . . 3.5 Water Spray Systems in Ammunition Stores. . . . . . . . . . . . . . . 3.6 Models for Traditional Low Pressure Sprinkler Systems . . . . . . . . . . 3.7 Dual Agent Systems . . . . . . . . . . . . . . . . . . . . . . . 3.8 Water Mist Additives . . . . . . . . . . . . . . . . . . . . . . . 3.9 Cool Gas Generator for Use in CAFS . . . . . . . . . . . . . . . . . 3.9.1 Compressor System . . . . . . . . . . . . . . . . . . . . .

4 4 6 6 6 6 7 10 14 15 15 15 17 17 17 17 17 18 18 19 20 20 21 22 26 28 32 33 34

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3.9.2 Cool Gas Generator System . . . . . . . . . . . . . . . . . . 3.9.3 Pressurized Bottle System. . . . . . . . . . . . . . . . . . . 3.9.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 4

Portable, Manually-Operated Systems . . . . . . . . 4.1 Portable Water Mist Fire Extinguishers . . . . . 4.2 Validation of Models for Current Fire Extinguishers . 4.3 Compressed Air Foam Systems (CAFS) . . . . . 4.3.1 Portable Independent Systems . . . . . . 4.3.2 Portable Dependent Systems . . . . . . . 4.4 Aerosols . . . . . . . . . . . . . . . . .

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New Fire Attack Strategies and Doctrines . . . . . . . . . . . Firefighting on Board Submarines . . . . . . . . . . . . . . 6.1 Extinguishing Systems on Board Submarines . . . . . . . 6.1.1 Water Spray Systems . . . . . . . . . . . . . 6.1.2 Foam and Foam-Water Spray Systems . . . . . . . 6.1.3 Compressed Air Foam Systems (CAFS) . . . . . . 6.1.4 Conventional Water Mist (or Fine Water Spray) Systems 6.1.5 Water Mist Systems Combining Water and Inert Gas. . 6.1.6 NanoMist® . . . . . . . . . . . . . . . . . 6.1.7 High Expansion Foam Systems (Inside Air Systems) . . 6.2 Electrical Cabinet Fire Suppression Systems. . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . .

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46 47 47 47 48 48 48 48 48 49 49 52

FiST Reports, Memos and Conference Proceedings 8.1 Reports and Memos . . . . . . . . . . 8.2 Conference Presentations and Proceedings . 8.3 Journal Paper . . . . . . . . . . . .

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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List of Figures Figure 1:

Figure 2:

Plots of Average Compartment Temperature Versus Time for Fire Suppression Tests Using the Low Pressure Water Spray System (10 bar and 5 bar) on 50% Obstructed Fires. The Results for a Free-burning Test with No Suppression System (Aborted 3 min After Ignition) are Also Shown. Extinguishment is Marked with a Thick Dot.. . . . . . . . . . . . . . . . . . . . . .

9

Plots of Average Compartment Temperature Versus Time for Fire Suppression Tests Using the Low Pressure Water Spray System (10 bar) and 4 or 9 Operational Nozzles on 50% Obstructed Fires. The results for a Free-burning Test with No Suppression System (Aborted 3 min after Ignition) are Also Shown. Extinguishment is Marked with a Thick Dot. . . . . . . . . . . .

9

Figure 3:

Section of Damaged Pipe (Left) and Spray Pattern from Pipe when Installed in Water Mist System (Right) for Damage Scenario 1. Damage Scenarios are Described in Appendix 1 of Reference 6. . . . . . . . . . . . . . . . 10

Figure 4:

Plots of Average Compartment Temperatures as a Function of Time for Fire Suppression Tests Run at Full System Pressure (100 bar), 75% System Pressure, 50% System Pressure, 25% System Pressure and 5 bar System Pressure. The Fire was 50% Obstructed. Extinguishment is Marked with a Thick Dot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 5:

Plots of Average Compartment Temperatures as a Function of Time for Fire Suppression Tests Using the High Pressure Water Mist System with 4 Nozzles and 2 Nozzles Operational. The Fire was Not Obstructed. Extinguishment is Marked with a Thick Dot.. . . . . . . . . . . . . . . . . . . . . . 12

Figure 6:

Compartment Temperatures Versus Time in Tests with Damaged Pipes and Pressures Between 25% and 50% of Normal Operating Pressure. Damage Scenarios (Tests 19, 20, 24 and 27) are Compared with Intact System with Reduced Pressure (Tests 3 and 4). Damage Scenarios are Described in Appendix 1 of Reference 6. . . . . . . . . . . . . . . . . . . . . . 14

Figure 7:

Overview of the Bunker with Spray Head Arrays Left and Right Against the Walls and Explosive Charge Hanging from Ropes [9]. . . . . . . . . . . 19

Figure 8:

Schematic Showing the Main Components of a Compressed Air Foam System (CAFS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 9:

Dummy Torpedo Positioned Above the Fuel Pan. Thermocouple Positions are Shown as White X-es. . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 10:

Torpedo Dummy (Left) Above the Fire and (Right) Next to the Obstructed Fire Prior to Activation of Water Spray System. . . . . . . . . . . . . . 23

Figure 11:

Plots of Peak Surface Temperatures Versus Time During Fire Testing of Dummy Torpedo in Position 1 (Above the Fire). Comparison of Results for the Free-burning Test (Aborted 3 Min after Ignition) and Different Water Spray Systems. Extinguishment is Marked with a Dot. . . . . . . . . . . . . . 25

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Figure 12:

Plots of Peak Surface Temperatures Versus Time During Fire Testing of Dummy Torpedo in Position 2 (to the Side of the Fire). Comparison of Results for the Free-Burning Test (Aborted 3 Min after Ignition) and Different Water Spray Systems. Extinguishment is Marked with a Thick Dot. . . . . . . . 25

Figure 13:

Schematic of the Test Compartment Used in the Novec™ 1230 / Water Mist Fire Suppression Testing. . . . . . . . . . . . . . . . . . . . . . . 29

Figure 14:

Mass of a Dependent CAF Back Pack System (with Different Gas Supplies) Necessary to Supply CAF for a Given Time. Dark Blue for Compressor, Light Blue for Pressurized Tank and Green for Cool Gas Generators.. . . . . . . 35

Figure 15:

Volume of a Dependent CAF Back Pack System (with Different Gas Supplies) Necessary to Supply CAF for the Time Shown. Dark Red for Compressor, Orange for Pressurized Tank and Purple for Cool Gas Generators. . . . . . 35

Figure 16:

From Left to Right, the Intelagard Macaw, Trimax Mini-CAF and NAFFCO CAF BP10l Portable CAFS Systems. . . . . . . . . . . . . . . . . . 41

Figure 17:

Left: StatX First Responder, and Right: DSPA 5-4 Manual Firefighter. . . . 43

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List of Tables Table 1:

Summary of Results for Damaged Low Pressure Water Spray Systems. . . .

Table 2:

Summary of Results for High Pressure Water Mist System Tests. . . . . . . 11

Table 3:

Summary of Results for Water Mist Fire Suppression Tests Using Damaged Pipe Segments. Damage Scenarios are Described in Appendix 1 of Reference 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 4:

Comparisons of Parameters for High and Low Pressure Water Mist Systems. . 16

Table 5:

Criterion Analysis of Low and High Pressure Water Mist Systems from a Survivability Viewpoint. . . . . . . . . . . . . . . . . . . . . . . 20

Table 6:

Summary of Results for Fire Testing of Sand Filled Dummy Torpedo. . . . . 24

Table 7:

Results of the Novec™ 1230 / Water Spray Fire Suppression Tests. . . . . . 31

Table 8:

Criteria Analysis of CGG System Versus Compressor and Pressurised Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 9:

Properties of Portable CAF Systems. . . . . . . . . . . . . . . . . . 41

Table 10:

Characteristics and Specifications of the StatX FR and DSPA 5-4 Aerosol Extinguishers. . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Table 11:

Summary of Results for Unobstructed Diesel Fires. . . . . . . . . . . . 44

Table 12:

Summary of Results for Obstructed Diesel Fires. Burn Room Door Closed after the Activated Aerosol Unit was Placed in the Space. . . . . . . . . . 45

Table 13:

Summary of Test 3a and 3b Results for Obstructed Diesel Bilge Fires. . . . . 45

Table 14:

Extinguishment and Reignition Times for Electrical Cabinet Tests. . . . . . 50

Table 15:

Measured HF Concentrations for Electrical Cabinet Fires Tests. . . . . . . 50

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1

Summary

The design of fire suppression systems for naval vessels can either be based on prescriptive regulations or be performance-based. Prescriptive regulations arise from experience as they are created from established practices and knowledge from disastrous incidents. Many prescriptive regulations are based on either non-validated assumptions or on validations that have been lost. Frequently the origin and rationale for the regulation is not traceable and may have become obsolete due to the development of new methods, equipment and materials. Therefore it is often not possible to assure the applicability of the regulation. This can lead to installation of costly, poorly dimensioned and ineffective systems. Prescriptive regulations have advantages. They are relatively simple to use, incorporate common experiences into standard protocols and are agreed upon as providing an adequate level of safety. From a liability point of view, prescriptive regulations free the design authority from responsibility, to some extent. A disadvantage of prescriptive regulations is that they have a tendency to favor existing technologies, making innovation and technological development more challenging. The need and desire for innovation is an important reason behind the philosophy of ‘goal-based ship constructions’ that has been introduced in the International Maritime Organization (IMO) Safety of Life at Sea (SOLAS) code in 2002. As naval vessels are likely to have specific requirements for operability and threat management, performance based safety design is generally the only approach available. A performance based design approach involves the establishment of agreed upon fire safety goals and objectives, deterministic and/or probabilistic analysis of fire scenarios and quantitative assessment of how alternative designs/systems meet the fire safety goals and objectives. To do so, accepted engineering tools, experimental methods and performance criteria are used. Performance based design of firefighting systems may require more work than would be required if prescriptive regulations were used. However, performance-based design has the potential to provide a more cost effective system that is tailored to a particular vessel or to a space on that vessel. From the perspective of naval firefighting applications, there is also the potential for enhanced operability, effectiveness and survivability of the vessel. Performance based fire regulations have been adopted in SOLAS and the Naval Ship Code (NSC). Research organisations from Canada, The Netherlands and Sweden have applied the performance based approach to a number of firefighting issues for naval vessels in the joint project New Fire Suppression Technologies on Board Naval Ships (FiST). Parties involved are DRDC in Canada, TNO and Royal Netherlands Navy in The Netherlands and SP Fire Technology and FOI in Sweden. There are no prescriptive requirements regulating residual capacity of fixed fire-fighting systems after weapon induced damage. Such a requirement is an example of where a performance based approach is desirable. The results of our research illustrate what residual capacity might be achieved from a damaged system and can be used to select redundancy approaches to reach the required performance. DRDC-RDDC-2015-R224

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Test results indicate that a damaged low pressure water spray system (reduced number of nozzles and pressure reduced to 5 bar) still meets the performance criteria: the fire is quickly suppressed and the compartment temperature is reduced to below 60°C within seconds. Performance criteria are met when redundant water feed pipes each supply 50% of the nozzles in a compartment and the system is fed by the ship’s fire main. Tests on a high pressure water mist system indicate that after reducing the number of nozzles and operational pressure to 25 bar the system is still compliant with the performance criteria. The compartment temperature did not rise above 150°C and was reduced to below 60°C within a few minutes. In such conditions, flashover did not occur and the ship divisions did not lose integrity. Even at fire main pressure, the system kept the compartment temperature below 350°C. This could prevent flashover and postpone or prevent fire breakthrough to adjacent spaces. When pump capacity is such that the operational pressure can be maintained at 25 bar, even in case of damage to the fire suppression system, the fire can be controlled and prevented from spreading. There are prescriptive requirements regarding water discharge densities to be applied in weapon storage spaces ranging up to 32 L/m2min. It would be beneficial to reduce discharge densities as the installation of systems for handling and storing large volumes of water can be challenging. A performance-based approach was again used to identify suitable protection systems for a defined design fire scenario. The performance criteria were based on the assumption that 200°C is the critical temperature for a fast heating phase and 150°C for a slow but prolonged heating of a weapon. The criteria were based on weapon cook-off tests performed at TNO. The testing showed that a system with a flow rate of 10 L/m2min met the performance criteria for our specific scenario. Prescriptive requirements in this case lead to an over-dimensioned and costly system. At their best, prescriptive regulations can provide good quality fire safety design. At their worst, prescriptive regulations can result in expensive and poorly adapted systems for managing fire threats on naval vessels. Designers, researchers and regulatory bodies must challenge the prescriptive requirements and try to find better, safer solutions when this is financially and technically feasible. In the FiST project we investigated performance criteria for cases where no regulations were prescribed, for example on damaged water mist systems. There have been suggestions for technical innovations, such as the use of bulkhead nozzles (rather than ceiling nozzles), more robust layout and local protection, residual capacity in the pump and the ability to connect water mist systems to the fire main. These innovations might have been inhibited by prescriptive regulations. Furthermore, testing of prescriptive regulations for water spray systems for ammunition storage spaces indicated that these can lead to poorly designed systems. Poor design not only affects the system, but also influences ship construction. In the past designers have had to cope with the free surface effects of enormous water flows into magazine spaces during discharge of the system. Canada was able to verify specific design options with respect to the use of Novec™ 1230. Knowledge on combining Novec™ 1230 with water mist or other water-based suppression systems may be implemented in future ship designs or mid-life upgrades. In Sweden the 2

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knowledge has been applied in design of firefighting systems for submarine engine compartments. In the Netherlands the work from FiST will be input for selection and layout of water mist systems on new shipbuilding programs with high degree of automation. We are currently investigating opportunities to develop practical methods, rules of thumb and tools for ship designers to employ performance based approaches to fire suppression themselves.

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2

Introduction

Over the past decades, naval damage control philosophies have changed significantly. There are a number of important reasons for this:  Recent changes in ship design are, among other things, driven by the fact that western navies are seeking to reduce manning. Manpower is expensive, so reduction in crew numbers may reduce the through-life costs of ships. There is also the concern that the interest in navy careers is declining. Reduced manning puts a strain on damage control (DC) effectiveness since DC is traditionally a manpower-intensive activity [1].  New legislation in the countries of all the Participants, aimed at preserving the environment, prohibits the use of ozone-depleting substances for fire-fighting agents. Therefore, DC in general, and fire-fighting in particular, must be achieved through solutions that require fewer crew members utilising healthy and environmentally-sound products.  Furthermore, new construction materials for naval craft, such as polymer composites, drive the need for new, effective fire safety measures to compensate for the combustibility of these construction materials.  Submarines have specific limitations with respect to fire-fighting agents due to their limited and confined living atmosphere. Solutions for these issues can be found, e.g., in damage-tolerant automated and autonomous fixed fire-fighting systems, innovative extinguishing equipment and the development of doctrines, procedures, and methods dedicated to these new technologies. These solutions and developments must be suitable for the naval environment and fulfil naval requirements, including those for adequate performance when a fire suppression system is damaged.

2.1

Objectives

This project had several objectives. One was to improve the collective understanding of fire-related phenomena. A second was to more effectively fight fire on board naval craft in hostile environments using technologies and methodologies that are new to naval craft. Another was to develop practical guidelines and tools for the design and specification of new fire extinguishing technologies on naval craft. This project produced new information on damage-tolerant systems, and design guidelines and tools for their use on naval craft. The early phase of the Project focussed on the assessment of the knowledge of the participants on the topics of interest. This was achieved by reviewing literature on the topics, discussions with international contacts and interaction with manufacturers. Industry was explicitly involved in the project, although the main focus of the participants was on consolidation and development of knowledge for design or modification of systems to perform adequately when damaged.

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Technologies were identified and work packages were established to address existing knowledge gaps, which were identified by national knowledge surveys of the participants. These work packages were focused on three basic areas: 1. Fixed Systems (Chapter 3) 2. Portable, Manually Operated Systems (Chapter 4) 3. Fire-fighting on board submarines (Chapter 6) Technologies within the first two areas were further developed within the third to suit the specific conditions on board submarines. The structure of this Scientific Report follows the work breakdown elements delineated in Project Arrangement Number 2010-06 under the Canada/Netherlands/Sweden Cooperative Science and Technology Memorandum of Understanding (dated May 2003).

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3

Fixed Systems

3.1

Water Mist and Influence on Fire

Water mist refers to fine water sprays in which 99% of the droplets are less than 1000 microns in diameter. The water mist droplet size distributions are defined in the National Fire Protection Association (NFPA) Standard 750 as Class1 (90% of the volume of spray with diameters of 200 microns or less), Class 2 (90% of the volume of spray with diameters of 400 microns or less), and Class 3 (90% of the volume of spray with diameters greater than 400 microns). Water mist suppresses a fire through cooling, oxygen displacement, radiant heat attenuation, and the kinetic effect of water mist on flames. Water mist can be generated in using different nozzles and pressures. Impingement nozzles have a large diameter orifice and a deflector and operate at low (12.0 bar or less) and intermediate (12.0 to 43.0 bar) pressures. Pressure jet nozzles have small diameter orifices (0.2 mm to 0.3 mm) or swirl chambers. Their operating pressures can range between low (5.1 bar) and high (272 bar). Twin fluid nozzles operate with a compressed gas (usually air) and water and consist of a water inlet, a compressed gas inlet and an internal mixing chamber. The pressures of the gas and water inlets are controlled separately and are in the low pressure region (between 3 bar and 12 bar). Physical and theoretical descriptions of water droplet dynamics in a fire environment have been studied and reported. Droplet size distribution was analyzed. It was shown that droplet size distribution depends on nozzle type, water pressure and collisions between droplets. Further, the dynamics of water droplets were analyzed considering initial droplet velocity, retardation due to drag and estimation of terminal falling velocities when drag and gravity are in equilibrium. Heat transfer to water droplets with emphasis on vaporization of water droplets was discussed and applied to show fire extinguishing effects. Finally the absorption of heat radiation in water mist was analyzed [2].

3.2 3.2.1

Water Mist Suppression Effectiveness in Battle-Damaged Conditions Threat Definition

Primary objective of the FiST project is to assess the residual performance of firefighting systems and equipment in case of damage from weapon effects following a weapon hit. In order to determine the damage to the systems and infrastructure typical threats to warships must be identified and engineering parameters must be quantified [3]. Using the engineering parameters, damage to the systems and post detonation fire loads (e.g., from residual weapon propellants) can be predicted. Typical expected damage scenarios are:  Perforations from bullets, shaped charge jets, direct fragments, spall.  Deformation up to rupture (of piping) from direct blast or from deformed structure.

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 Malfunction or loss of function by blast induced shock motions from blast loaded structure.  Burning of combustible parts exposed to heat load from blast and fire. Ambition levels for post incident capabilities are commonly quantified in three categories: fight, move and float. One could argue that for the fight and move ambition levels a water mist system should have adequate residual capacity after a hit. If the ship is only required to float after a specific incident, the water mist system may not be required if evacuation is arranged properly. How this relates to actual weapons is dependent on ship size and operational theater and such information supersedes the classification level of this report.

3.2.2

Effectiveness of Low Pressure Water Mist Systems

A number of full scale tests were run at SP Technical Research Institute of Sweden during late December 2011 and January–February 2012 [4], [5]. The main goals of the tests were to investigate possible redundancy solutions for active firefighting on board navy ships and to evaluate the effectiveness / residual capacity of a low pressure water mist system following damage. The tests were conducted in a 55 m³ compartment with a 1.6 m² door opening. The walls of the test compartment consisted of wood studs with calcium silica panels. The water spray system consisted of nine open full cone nozzles with a K-factor of 5.93, mounted in a 3 x 3 pattern with a spacing of 1.75 m and operating at 10 bar. The performance criteria for the low pressure system were:  fast extinguishment (≤ 1 min) of a non-obstructed diesel pool fire in a well-ventilated environment; and  fast suppression (≤ 1 min) of an obstructed diesel pool fire in a well-ventilated environment where suppression is defined as:  reduction of incident radiation to 20% of that in the free burning condition; and  reduction of the difference in plate thermometer (PT) temperature and ambient temperature to 20% of that for free burning condition. To comply with the performance criteria the water flow was adjusted to suppress and extinguish a fire in an open space, i.e., a space imitating a situation where decks and bulkheads were gone due to an explosion. This meant that no enclosure effects existed, e.g., suppression due to lowered oxygen content and the presence of combustion gases that play a significant role in closed spaces were not involved or were minimized in the tests. The amount of water used therefore was somewhat higher than the IMO standard (6 L/m2min). A 1.08 m² steel pan filled with 16 litres of diesel fuel was used for the pool fire testing. The diesel was normally allowed to burn for 30 seconds prior to activation of the suppression system. The maximum heat release rate of a diesel pool fire this size is 1.3 MW. During the tests the fuel surface was either fully exposed to the water spray or obstructed by pipes or calcium silica boards. Two damage scenarios were tested, one where the number of operational nozzles was reduced and the other where the water pressure in the fire suppression system was reduced.

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Reduced number of nozzles: These tests were performed based on the assumption that the water mist system in a compartment was fed by two pipes and that one of the pipes was damaged. Therefore only half of the nozzles were operational and they had a larger spacing than in the undamaged system. For these tests, 4 nozzles (instead of 9) with a spacing of 3.5 m (instead of 1.75 m) were used. Reduced pressure: These tests were performed based on the assumption that 1) the piping delivering water to the nozzles was damaged or 2) the fire main was used to supply water to the system. Both of these scenarios result in reduced system water pressure. A system pressure of 5 bar (instead of 10 bar) was used for these tests. Compartment temperatures presented in Figure 1 and Figure 2 are an average of the temperatures from two thermocouple trees. The time to extinguishment and the time until the temperature was reduced below 60°C are shown in Table 1 and the compartment temperatures as a function of time are plotted in Figure 1 and Figure 2. Table 1: Summary of Results for Damaged Low Pressure Water Spray Systems. Description of setup 9 nozzles, 50% obstruction Full pressure (10 bar) 4 nozzles, 50% obstruction, Full pressure (10 bar) 9 nozzles, 50% obstruction, Reduced pressure (5 bar)

Water discharge into the space [l/min]

Time (after activation) to extinguishment [s]

Time (after activation) to temp