4
Navy-Specific Issues

Halons are recognized as ideal fire extinguishing agents, particularly for fighting fires caused by flammable liquids and explosive gases. They are highly effective in extinguishing fires in minimal time. They are non-corrosive and, when deployed at the recommended volume densities, they are non-toxic. Because of these characteristics, halon 1301 (a total flooding agent) and halon 1211 (a streaming agent) are widely used on board Navy ships, in aircraft, and at shore facilities, as they arc throughout the civil sector.

Unfortunately halons do contribute to depletion of Earth's ozone layer, a peril recognized by the 1987 Montreal Protocol. Even though lower in emissions than their refrigerant cousins, the greater ozone-depleting characteristics of halons per pound have resulted in a mandated cessation of production in the United States, some 25 years after halons were introduced in the Navy as fire extinguishing agents.

Under an executive order effective in January 1994, halons can no longer be manufactured in the United States. But because of the difficulty of finding a suitable fire extinguishing substitute for halons 1301 and 1211, the military services are permitted to use these chemicals for mission-critical purposes, such as fire fighting, in existing platforms (ships, aircraft, weapons, vehicles) until the current halon supply or "bank" is exhausted. Each service is expected to live within its own halon budget, and transfers between service accounts are permitted only with approval of the Secretary of Defense. The hope, then, is that (1) the Navy's halon supply is sufficient to protect existing platforms until they are retired from service or scrapped, and (2) there is sufficient time to develop and test suitable replacement fire extinguishing agents and dispensing systems for next-generation platforms.

In its deliberations, the committee recognized the importance of assessing the potential and need for finding a drop-in halon replacement, given the challenge faced by the Navy to reduce the risk, or perception of risk, to combat readiness and peacetime safety that might flow from either early rescission of authority to use halon—a possible result of increasing international pressure to stop any use of halon—or the exhaustion of halon supplies that could result from now unforeseen demands of a prolonged, major war on the scale of World War II, Korea, or Vietnam.

In assessing the potential for finding a suitable drop-in, the committee began with the postulate that any replacement agent or system must possess at least five attributes: (1) performance that meets the fire extinguishing requirement, (2) low toxicity, (3) acceptable environmental properties, (4) size and weight that can be accommodated on existing platforms, and (5) procurement and installation that are not prohibitively expensive. The committee accepted the premise that such a replacement, if identified, would very likely not match the exceptional fire extinguishing performance of halon on a space and weight basis, but also that it need not do so. What matters more is adequacy of performance, feasibility of installation, and affordability.

Determining the need for a drop-in agent involved assessing (1) the probability that halon systems now installed may have to be replaced and (2) the effectiveness of non-halon systems the Navy has selected for its next-generation ships and aircraft as well as the feasibility of installing them in current platforms. In addressing these issues, the committee sought answers to the following key questions: Is the Navy's supply of halon sufficient to last until the current classes of ships and aircraft are retired from service? Are the halon replacement systems selected by the Navy for new-design ships and aircraft (HFC-227ea, water mist, HFC-125, gas generator) adequate in performance and environmentally satisfactory? Is retrofit of HFC-227ea/water mist (ships) and HFC-125/gas generators (aircraft) into existing platforms technically feasible? What is the estimated cost of retrofit? Is a drop-in replacement for halon very near at hand, a scientific possibility in some reasonable time if sufficient resources are applied, or an illusory target unworthy of investing R&D funds?



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--> 4 Navy-Specific Issues Halons are recognized as ideal fire extinguishing agents, particularly for fighting fires caused by flammable liquids and explosive gases. They are highly effective in extinguishing fires in minimal time. They are non-corrosive and, when deployed at the recommended volume densities, they are non-toxic. Because of these characteristics, halon 1301 (a total flooding agent) and halon 1211 (a streaming agent) are widely used on board Navy ships, in aircraft, and at shore facilities, as they arc throughout the civil sector. Unfortunately halons do contribute to depletion of Earth's ozone layer, a peril recognized by the 1987 Montreal Protocol. Even though lower in emissions than their refrigerant cousins, the greater ozone-depleting characteristics of halons per pound have resulted in a mandated cessation of production in the United States, some 25 years after halons were introduced in the Navy as fire extinguishing agents. Under an executive order effective in January 1994, halons can no longer be manufactured in the United States. But because of the difficulty of finding a suitable fire extinguishing substitute for halons 1301 and 1211, the military services are permitted to use these chemicals for mission-critical purposes, such as fire fighting, in existing platforms (ships, aircraft, weapons, vehicles) until the current halon supply or "bank" is exhausted. Each service is expected to live within its own halon budget, and transfers between service accounts are permitted only with approval of the Secretary of Defense. The hope, then, is that (1) the Navy's halon supply is sufficient to protect existing platforms until they are retired from service or scrapped, and (2) there is sufficient time to develop and test suitable replacement fire extinguishing agents and dispensing systems for next-generation platforms. In its deliberations, the committee recognized the importance of assessing the potential and need for finding a drop-in halon replacement, given the challenge faced by the Navy to reduce the risk, or perception of risk, to combat readiness and peacetime safety that might flow from either early rescission of authority to use halon—a possible result of increasing international pressure to stop any use of halon—or the exhaustion of halon supplies that could result from now unforeseen demands of a prolonged, major war on the scale of World War II, Korea, or Vietnam. In assessing the potential for finding a suitable drop-in, the committee began with the postulate that any replacement agent or system must possess at least five attributes: (1) performance that meets the fire extinguishing requirement, (2) low toxicity, (3) acceptable environmental properties, (4) size and weight that can be accommodated on existing platforms, and (5) procurement and installation that are not prohibitively expensive. The committee accepted the premise that such a replacement, if identified, would very likely not match the exceptional fire extinguishing performance of halon on a space and weight basis, but also that it need not do so. What matters more is adequacy of performance, feasibility of installation, and affordability. Determining the need for a drop-in agent involved assessing (1) the probability that halon systems now installed may have to be replaced and (2) the effectiveness of non-halon systems the Navy has selected for its next-generation ships and aircraft as well as the feasibility of installing them in current platforms. In addressing these issues, the committee sought answers to the following key questions: Is the Navy's supply of halon sufficient to last until the current classes of ships and aircraft are retired from service? Are the halon replacement systems selected by the Navy for new-design ships and aircraft (HFC-227ea, water mist, HFC-125, gas generator) adequate in performance and environmentally satisfactory? Is retrofit of HFC-227ea/water mist (ships) and HFC-125/gas generators (aircraft) into existing platforms technically feasible? What is the estimated cost of retrofit? Is a drop-in replacement for halon very near at hand, a scientific possibility in some reasonable time if sufficient resources are applied, or an illusory target unworthy of investing R&D funds?

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--> This chapter summarizes current halon 1301 ship and aircraft installations and the Navy's investment in halon systems, discusses systems planned for new-design ships and aircraft, assesses the current and projected status of the Navy's halon inventory, and finally, examines the potential for retrofit of non-halon systems into existing platform designs. The chapter closes with the committee's findings and recommendation on Navy-specific management issues. Halon systems in shore facilities were not considered by the committee since these do not fall into the mission-critical category and are to be replaced by the year 2000. Appendix A takes a brief historical look at the introduction of halon fire extinguishing systems in the Navy and discusses in some detail the Navy's need for and use of extinguishing systems currently installed aboard ships and aircraft. Ship Systems Summary of Halon 1301 Ship Installations Table 4.1 lists all halon 1301-equipped ships in commission today as well as those current designs with units yet to be built. It can be seen that some 1.4 million pounds of halon are now installed, with 441,000 pounds scheduled for commitment to new-construction vessels in the future. A review of the decommissioning schedule shows that few ships will be removed from active service for the next 15 to 20 years. Beginning in 2015, however, the pace of decommissioning picks up and, by 2025, over 50% of the currently installed halon systems will have been taken out of service, with the largest contributors to this halon reduction being LPD-4 class amphibious ships, FFG-7 class frigates, DD-963 destroyers, and the remaining fossil-fueled aircraft carriers. Looking at the halon 1301-equipped ships yet to be built, the DDG-51 class Aegis destroyers appear to warrant special attention. Thirty-seven of these vessels are scheduled to be built in the future, with construction phased by blocks or "flights" in which accumulated design changes are incorporated. The 37 ships will each require 8995 pounds of agent for a total of 332,815 pounds of installed halon 1301. Not shown in Table 4.1 are. ships of the Military Sealift Command (MSC). As of August 1996, MSC operated 46 ships incorporating 331 halon 1301 systems containing 509,000 pounds of agent. The committee understands that MSC vessels fall outside the normal purview of the Office of Naval Research and the Naval Sea Systems Command, and therefore, details of installations and MSC's plans for the future were not considered during the course of the study. Investment in Ship Halon Systems The committee inquired into the investment the Navy has made to date in halon 1301 installations in the current fleet. Taking the mix of ship sizes in the various classes, NavSea engineers calculated that the average cost for an individual system in today's dollars is about $300,000. Installation of piping, bottles, and control equipment accounts for $275,000, with the remaining $25,000 being the cost of hardware and agent. Multiplying this average cost by the total number of systems listed in Table 4.1 yields an investment of $665 million. And if new-construction plans are executed as now planned and shown in the table, this figure will grow by another $166 million to an investment totaling $831 million. To make the investment picture complete, the cost of RDT&E would have to be added, but this information was not available to the committee. Fire Extinguishing Systems for New-Design Ships The Navy is shifting to non-halon systems in its next-generation, new-design ships. These include the LPD-17 amphibious ship class, the next aircraft carrier (CVN-76), and a proposed new surface combatant class (SC-21) that will follow the DDG-51 production run.

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--> Table 4.1 U.S. Navy Shipboard Halon 1301 Systems Ship Class Current Number of Ships per Class No. of Ships in Class Under Construction or Planned Number of Systems per Ship Amount of Halon per Ship (lb) If Banked, Quantity of Two-Shot Systems per Ship Systems per Class Amount of Halon per Class (lb) No. of Systems in Construction Amount of Halon in Construction (lb) Banked (B) or Modular (M) Systems Estimated Decom. Year for Last Ship of Class Assumed Service Life of Ship Class (years) AO-177 5   13 13630 3 65 68150     B 2023 40 AOE-1 4   5 10125   20 40500     M 2010 40 AOE-6 3 1 13 24820 10 39 74460 13 24,820 B 2038 40 ARS-50 4   6 2375 2 24 9500     B 2026 40 AS-39 1   3 8360   3 8360     M 2021 40 CG-47 27   8 4905 1 216 132435     B 2034 40 CV-59/63 4   14 20500   56 82000     M 2018 50 CVN-65 1   7 4245   7 4245     M 2013 N/A CVN-68 5   7 3500   35 17500     M 2039 50 CVN-73 2 1 14 4340 0 28 8680 14 4,340 B 2048 50 DD-963 31   13 6275   403 194525     M 2023 50 DDG-993 4   6 5000   24 20000     M 2022 40 DDG-51 16 37 12 8995 9 192 143920 444 332,815 B 2047 40 FFG-7 45   15 5410 12 675 243450     B 2018 40 LCC-19 2   6 6625   12 13250     M 2010 N/A LHA-1 5   8 11375   40 56875     M 2020 40 LHD-1 4 3 14 18220 3 56 72880 42 54,660 B 2040 40 LPD-4 13   5 2975   65 38675     M 2011 40 LSD-36 5   5 4005   25 20025     M 2012 40 LSD-41 11 1 10 10285 4 110 113135 10 10,285 B 2038 40 LST-1179 2   10 4525   20 9050     M 2011 40 MCM-1 14   3 1810 2 42 25340     B 2029 40 MCS-12 1   5 6540   5 6540     M 2010 40 MHC-51 6 6 5 2375 4 30 14250 30 14,250 B 2034 35 PC-1 13   2 1000 2 26 13000     B 2024 30 TOTALS 228 49       2218 1430745 553 441,170      

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--> In choosing a fire extinguishing approach for these new ship designs, the Navy evaluated a wide range of new technologies to replace halon 1301. After extensive testing, heptafluoropropane (HFC-227ea), a commercially available gaseous agent, and a Navy-designed high-pressure water mist system were chosen. Either system has fire extinguishing performance at least equivalent to that of halon 1301. In the LPD-17, water mist will be used in the machinery spaces and HFC-227ea elsewhere, with the former chosen because of lower cost. The CVN will employ HFC-227ea solely, since no requirement exists for main machinery space systems. The SC-21 ship design is still in the concept stage, and decisions about fire extinguishing systems have yet to be made. HFC-227ea The HFC-227ea total flooding gas system, largely using existing 600-psi halon 1301 hardware, is to be installed in flammable liquid storage and issue rooms as well as other small segregated compartments in both the LPD-17 and CVN-76. These systems are relatively small in size (<< 100 lb of agent) and function identically to today's halon 1301 systems. Water Mist Water mist technology has recently been the subject of considerable interest because it offers lower water demand (than standard water sprinkler systems) and the promise of the ability to extinguish fires in obstructed spaces (a key feature of halons and other gaseous agents). Advantages include low agent cost, absence of toxicity and environmental problems, effectiveness in suppressing flammable liquid pool and spray fires, and potential for explosion suppression. Details of developments in the field are presented in Appendix D. Water mist systems employ high pressures (circa 1000 psi) and nozzles designed to produce drops distributed about the 100-micron size range. Drops smaller than 50 microns in diameter begin to exhibit characteristics of a gas, resulting in lower fallout losses and to some extent, the ability to diffuse around obstructions. The Navy has subjected commercial and Navy-designed water mist systems to extensive testing in the ex-USS Shadwell facility. As a result, the Navy-designed system has been chosen for use in all machinery spaces in the LPD-17, an amphibious ship class of new design. The system is driven by two independent 250-hp pumps, supplying water at 1000 psi to nozzles in each space. The arrangement of the machinery spaces in LPD-17 makes for a particularly efficient system. Redundant pumps are provided, forward and aft, and valving arrangements direct water to any space using either of the two pumps. Nozzles are installed with approximately 100-sq.-ft spacing, with water flow in the range of 2- to 3-gpm per nozzle. Nozzles are positioned in a uniform grid pattern in the overhead of each space and at the intermediate deck level. The high water flow demand of the system, that is a disadvantage of the Navy design, precluded the use of pressurized water cylinders because of the significant space, cost, and weight impact. Hence, pumps were the only feasible option. Each pump motor is in the range of 200 hp, supplying 225 gpm at 1000 psi. Modem electrical power distribution systems in these new ships incorporate improved survivability features, and the Navy feels confident that a reliable power source will be available for the pumps even under battle damage conditions. While the water mist system is effective, has no adverse environmental impact, and makes economic sense in the large space application, it is at present less suited for use in small spaces spread about a ship. In such instances, a water mist system may be more expensive and heavier than an HFC-227ea system because of the need for piping and pump redundancy, just the reverse of the large, concentrated machinery space application. To address this shortcoming, the Navy has funded an R&D program to evaluate a water mist system for small spaces which employs pressurized water containers rather than a pump system.

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--> Table 4.2 Naval Aircraft Fire Extinguishing Systems—Current Status of Halon Applications AIRCRAFT TYPE YEAR OUT OF SERVICEa NUMBER OF AIRCRAFTb APPLICATION  WEIGHT (lb)  HALON Total Pounds for Aircraft Type REMARKS     Current 2028 Engine Dry Bay Portablec Other Halond Bottlee Plumbingf System Platform   Fixed Wing                           P-3 >2028 351 42 X   X X-APU 46 53 13 111 15,970   F/A- 18 >2028 826 6 X       6 9 10 23 4,045   A-6E 1997 85   X     X-FUEL 9 69 — — 7,225 Retired 1997 F-14 2028 422 1 X     X-OWAC 16 26 14 55 6,465   E-2C 2022 123   X   X   13 17 4 34 1,600   EA-6B >2028 56 5 X       30 30 4 64 1,680   C-2A 2020 38   X   X X-APU 16 25 4 44 590   S-3 >2028 134 6     X X-APU 1 9 1 11 153   E-6A >2028 16 16 X   X X-APU 35 72 3 109 550   C-130 2019 109   X   X   54 46 28 128 5,890   T-44A 2000 45   X   X   5 15 3 23 225   F/A-18E/F 2010 7   X       6 12 9 27 395 EMD only C-9 >2028 29 26 X   Xg   17 32 5 53 490   C-12 >2028 80 22 X   X   5 15 3 23 840   C-20 >2028 7 7 X     X-APU 14 27 2 42 96   T-39 >2028 14 4 X       13 17 3 33 180   Rotary Wing                           H-53E >2028 199 30 X   X X-APU 18 50 6 74 3.580   SH-60 >2028 369 66 X   X   5 20 3 28 1,240   H-53A/D 2024 128   X   X X-APU 14 37 5 55 1,730   CH-46 >2028 253 12 X   X   6 19 5 30 1,520   SH-2 >2028 89 10 X   X   5 20 3 28 445   H-3 2012 100   X   X   5 20 3 28 500   AH-1 >2028 213 47 X   X   4 21 3 28 640 Current upgrade UH-1 >2028 150 28 X   X   4 21 3 28 600 Current upgrade V-22 2007 2   X   X   5 20 3 28 10 FSD only                       Grand Total 56,659   a Estimated based on life extension programs. b Rough estimates, not exact figures. c Except for E-2C aircraft, it is planned that in 1997 all platforms using halon portables are to be retrofitted with CO2 portables. d Excludes portable halon weight (2.75 lbs per extinguisher). e Empty bottle weights derived from MIL-C-22284. Excludes empty portable bottle weight. f Estimated based on weight per foot of 0.5-inch diameter stainless-steel tubing. Excludes valves, fittings, switches, gauges, and mounting hardware. g Each C-9 has two halon 1211 portables.

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--> Aircraft Systems Summary of Halon 1301 Aircraft Installations Table 4.2 lists all naval aircraft that have halon 1301 fire extinguishing systems installed, indicating the type and number of aircraft, the year the model goes out of service, halon application, and system weight. With the exception of the S-3, all multiengine planes are equipped with engine bay/nacelle extinguishers and all cabin aircraft carry portable bottles for hand-held use. Planes with auxiliary power units are protected, and the F- 14 also has a system covering an area above the wing, aft of the cockpit, which has proven to be vulnerable to hydraulic fluid fires. The retirement of the A-6E attack plane in 1997 will remove the only halon inerting system in the naval aviation inventory. No existing naval aircraft employs halon for dry bay fire extinguishing purposes. Significantly, the total quantity of halon installed in naval aircraft is a small fraction (5%) of that in ships—65,000 lb versus 1.4 million lb. Proportionally, however, the aircraft contribution to annual halon releases is far greater than that of ships, constituting some 40% of the total. The Navy is working actively to reduce these releases of halon from aircraft and has succeeded in lowering the annual release rate by over one-half in the last 4 years. Investment in Aircraft Halon 1301 Systems As with ships, the committee was interested in determining the investment the Navy has made in halon 1301 aircraft systems. Upon request, engineers oft he Naval Air Systems Command analyzed one aircraft type in each of four size categories—very small, small, medium, and large, similar to the SH-60, F-18C/D, P-3, and C-130, respectively. As in the ship case, the halon 1301 system cost for an individual aircraft was determined by adding installation, hardware, and agent cost elements. This figure was, in turn, multiplied by the number of aircraft in the respective size category to obtain a category subtotal. Combining the four categories resulted in a total amount, in 1996 dollars, of $140 million. While this figure is based on a somewhat cursory analysis, it nevertheless gave the committee a rough approximation of the halon 1301 investment in the Navy' s current fleet of aircraft. To get a complete investment picture, the cost of installing halon systems in aircraft still being manufactured (e.g., F-18C/D) would, of course, have to be added as well the cost of initial system RDT&E; however, this information was not available to the committee. Fire Extinguishing Systems for New-Design Aircraft The Navy is shifting to non-halon fire extinguishing systems for its next-generation, new-design aircraft, and the proposed Joint Strike Fighter (JSF) will use an alternative system as well. Two approaches have been selected and tested for use in the next naval aircraft, the F-18E/F and V-22. The JSF will not enter engineering and manufacturing development until the turn of the century; hence, the fire extinguishing needs and technical approach for this joint services aircraft have not yet been selected. HFC-125 The V-22 will employ both new approaches—an HFC-125 compressed gas system and one based on new inert gas generator technology. HFC-125 liquefied gas, the 1301 replacement selected by the three military services, will be used in the engine bays. These HFC-125 systems are identical in architecture and function to current halon 1301 systems, except that three times the weight of agent is required to meet the fire extinguishing requirement. Gas generators will be employed elsewhere in the V-22 and in both engine bays and dry bay areas of the F-18E/F. Gas generator technology and its specific application in these two new aircraft are discussed below.

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--> Inert Gas Generator Technology Inert gas generator technology for aviation fire extinguishing applications has been developed almost entirely by the Naval Air Systems Command. While the underlying propellant technology is well understood, extension to fire suppression applications has posed significant development and engineering challenges. The technical basis for the suppression of diffusion or premixed hydrocarbon/air flames with inert gases is well established. Extinction of flames will occur at a specific concentration of an inert gas in air. There are differences in extinguishing concentration with fuel type, atmospheric pressure, and oxygen concentration, but the basic principle has been well established. However, design of a propellant system that will produce adequate quantities of inert gas quickly enough and distribute the gas to all locations in a high-air-flow environment is a substantial challenge. An analogous technology, combustion-generated aerosols or pyrotechnically generated aerosols, has been used as a halon replacement. In these devices, a combination of solid propellant and binder produces a mixture of inert gases and fine solid particulate. The solid particulate is, in principle, a more efficient fire suppressant than are inert gases only. These technologies have been pursued overseas following initial development in the USSR. The inert gas generator system developed and tested by the Navy is designed to retain most of the solids inside the generator and to minimize the discharge of particulate into the engine or dry bay. This helps to resolve the issue of collateral damage associated with combustion-generated aerosols and simplifies agent mixing and the distribution problem. The performance requirements for the two aviation uses (engine bay and dry bay) of inert gas generators are substantially different. The engine bay threat is a liquid fuel diffusion flame in a complex flow geometry with high air flow rates. The system must discharge within a few seconds and produce sufficient agent to extinguish the diffusion flame at any location in the engine nacelle. Challenges include a widely variable air flow, numerous flame stabilization points, and a highly obstructed flow geometry. Protection of aviation dry bays requires suppression of an incipient premixed liquid/fuel aerosol in the presence of a hot ignition source. This is in effect an explosion or deflagration suppression problem. Here, the requirement is for detection and suppression of the explosion kernel within of tens of milliseconds. The agent must be produced and distributed throughout the protected volume or directed locally around the explosion kernel. Sufficient duration of agent flow must be provided to prevent reignition of the fuel or flashback from a remote unextinguished flame. Inert gas generators rely on the production of CO2 or nitrogen at high rates through the combustion of solid propellants. As shown in Figure 4.1, the hardware and process are analogous to sodium azide air bag inflators in automobiles. F/A-18E/F Engine Nacelle/Dry Bay The inert gas generator system developed for the F/A-18E/F engine bay and tested in real-scale live fire testing demonstrated equivalent or lower space and weight requirements relative to one using halon 1301. Although a thin film of particulate is developed within the engine bay, its impact has been determined to be inconsequential. Inert gas generator systems were also developed for F/A-18E/F dry bay deflagration suppression. These systems use multiple (6 to 10) gas generators, actuated by 1 of 14 optical (flame) fire detectors. The gas generators are fired in either a fixed sequence or in a sequence determined by which of the 14 optical detectors is first triggered. A typical system employing gas generators is similar to a halon 1301 installation for extinguishing engine fires (see Figure A.3, Appendix A) except that the generator replaces the halon bottle. The configuration currently being tested consists of six 157-gram gas generators, 14 optical fire detectors, and a fixed generator firing sequence. These tests are being performed on an F-18C test platform.

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--> Figure 4.1 Typical azide inflator used in automotive industry; not for use in aircraft. V-22 Midwing Protection Inert gas generators are also being used to protect the midwing and wing bay volume of the V-22. This area of the aircraft must be protected as one single volume due to the multiple flow paths for both fire suppression agent and fuel/flame. The design of inert gas systems for the midwing required optimization of propellant loading for fire extinguishment with simultaneous minimization of the threat of overpressurization due to excessive gas production. In addition, a generator firing controller and associated logic were developed to actuate the needed generators in the proper sequence to locally extinguish the fire and to maintain an inert atmosphere long enough to prevent reignition or flashback. The final design consists of 17 gas generators of five different sizes and 16 optical detectors with the requisite generator sequencing and detection logic. This design has been subjected to actual-scale live fire testing and was successfully qualified. Inert Gas Generator Development Summary Inert gas generators for naval aviation applications have been shown to be an effective replacement for halon 1301. They have demonstrated performance similar to that of halon 1301 in high-challenge engine nacelle fires, with space and weight requirements lower than those for halon 1301. The rapid development, qualification, and deployment of this technology into the F/A-18E/F and V-22 is a remarkable achievement, accomplished almost wholly within the naval aviation community, and is certainly worthy of special note. Given the flexibility of the design and the low space and weight requirements, the gas generator may be a suitable candidate for retrofit replacement of halon 1301 systems in selected existing aircraft should that become necessary in the future. However, an impediment to arriving at a decision to retrofit such a system or to incorporate gas generators into new designs is the insufficiency of engineering tools for evaluating gas generator performance, notably in the flow, mixing, and flame extinction processes, thereby causing undue reliance on expensive and time-consuming full-scale tests. Adaptation of existing fluid flow and combustion models to inert gas generator systems would greatly facilitate future design efforts, with potential significant cost and time savings resulting from a reduction in requirements for full-scale testing.

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--> Navy Halon Inventory The committee inquired into the amount of halon installed in ships and aircraft, its predicted usage over the various platform life spans, and the status of non-installed halon reserves available to the Navy, sometimes referred to as the ''bank'' or "stockpile." By direction of the Office of the Secretary of Defense, halon reserves are under the central control of the Defense Logistics Agency. However, each military service has been allocated a portion of this reserve in accordance with its predicted needs at the time the Executive Order was issued banning halon production in the United States. The Navy manages its halon usage, recycling programs from ships and aircraft going out of service, and withdrawals from the reserve. Like the other services, the Navy is expected to meet future needs for halon 1301 by recycling, reducing releases caused by human error, and emphasizing a lower-release approach in training. Shortfalls are made up by drawing from the reserve allocation, within which the Navy is expected to remain unless authorized to exceed the limit. Table 4.3 contains projections of halon use, anticipated recovery of halon from retiring ships and aircraft, and the resultant impact on the Navy halon reserve out to the end of the service lives of the various halon-equipped platforms. While ship and aircraft counts can be expected to change somewhat from year to year, and usage and recovery data revised as recovery experience is gained and data collection methods improved, the presentation nevertheless highlights several points of note. First, aircraft account for only a minute portion of the installed base of halon while contributing 40% of the releases. Second, as Figure 4.2 shows graphically, the reserve is projected to be depleted gradually over the years through releases and new installations until reaching a low point in the 2030 time period. After this, the reserve gradually builds due to recycling and lower annual releases occasioned, in turn, by there being fewer halon-equipped ships in service. Figure 4.2 Navy total halon 1301 reserve bottom shaded portion of bars) including Military Sealift  Command (MSC) reserve quantities and net usage. Note, however, that number of  MSC ships (46 ships currently) and installed charges (approximately 0.5 million lb currently)  are not included. The installed base on ships is indicated in the middle portion of each bar,  and the installed base on aircraft at the top of each bar.

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--> Table 4.3 FY 96 Navy Halon 1301 Projections and Navy Reserve  

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--> NOTES FOR TABLE 4.3: 1. NAVAIR inventory, installed charge, and requirements data are from the beginning of FY 1995 through the end of FY 2028. 2. The hull and aircraft numbers are the average numbers in service throughout the respective fiscal years. This applies to the installed charge values as well. 3. Analysis includes projected net usage of 136 lb per year for MSC from FY 1995 through FY 2005. 4. Stockpile balances on September 30, 1995, and July 1, 1996, are the starting balance on January 1, 1995, net of the total Defense Supply Center and Cheatham Annex issues and returns to DSC, to date. Beyond July 1, 1996, the stockpile balance is estimated using the projected usage and recovery for each fiscal year. 5. The NAVSEA recovery rate is assumed to be 70%. 6. NAVSEA hulls and installed charges do not include any landing craft air cushions. Finally, the Navy has about $29 million invested in the halon 1301 reserve based on a recent large-purchase price of $12/lb. At the current market price for small lots, the value of this reserve could be as high as $85 million. It is anticipated that the price will rise as time passes and as the impact of manufacturing cessation is felt worldwide. Assuming that the predictions are accurate, it appears that the Navy has sufficient agent in hand to support halon-equipped ships and aircraft until they go out of service. This conclusion is valid so long as the United States is not involved in a major war, there is no rescission of the current authorization to use halon for military-critical purposes, and the Navy's inventory is well managed. Given the minimal reserve forecast at the 2030 stockpile nadir, however, the Navy may wish to consider adding modestly to its reserve in the near term as a hedge against uncertainty or, alternatively, electing to install non-halon fire extinguishing systems in selected new-construction vessels such as the DDG-51. Retrofitting Non-Halon Systems in Existing Ships and Aircraft When it came to a consensus that a "no-penalty" drop-in substitute for halon 1301 was not anywhere near at hand, the committee thought it prudent to explore the technical feasibility and cost of retrofitting, in existing platforms, the fire extinguishing system approaches already selected for new-design ships and aircraft. The committee thought it important to make such a determination as a hedge against the possibility, however unlikely, that use of halon might be proscribed before existing ships and aircraft were retired or that the reserves might prove to be insufficient because of mismanagement or future unanticipated high usage. The systems considered were HFC-227ea and water mist for ships, and HFC-125 and inert gas generators for aircraft, all of which have been described previously. Ship Retrofit HFC-227ea Systems Since more than twice the weight and storage volume of HFC-227ea, relative to halon 1301, is required to achieve adequate extinguishing performance, it is not possible to replace halon 1301 with HFC-227ea without making hardware changes to the system. In retrofitting either modular or manifold (or banked, distributed) systems, changes to nozzle design and location may be required in addition to modifications to piping. Replacement of modular systems with higher-capacity and/or additional cylinders poses no particular technical problems. Space could likely be found for larger or additional cylinders in the machinery spaces requiring protection.

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--> Retrofitting manifold (banked) systems would pose a more difficult challenge. This is related partially to the need to markedly increase the quantity of stored agent in bottles located in what may be a confined manifold area rather than being able to place them more easily throughout the protected space proximate to the nozzles, as in the case of modular installations. Further, there would an attendant need for long runs of larger-diameter piping connecting the manifold with the nozzles in order to meet the requisite 10-second discharge time. For this reason, a hybrid approach has been developed as a way to meet the special retrofit needs of certain manifold ships. This concept involves replacing halon 1301 with HFC-227ea directly in the existing manifold cylinders and also adding modular units with their own nozzles to make up the additional HFC-227ea required. Questions of nozzle location, nozzle design, and the ability of these two systems to function efficiently, particularly with respect to agent distribution and mixing, are as yet unresolved. A second alternative approach for manifold ships would involve acceptance of some operational risk. Here, if a particular ship class has limited space to accommodate additional HFC-227ea bottles, eliminating the "second shot" capability in those manifold ships now so equipped would make space available for the additional required HFC-227ea. Water Mist Systems Retrofitting water mist systems using the current Navy design concept would entail substantial ship modifications. Two pump rooms, for which space may not be available, and the addition of hundreds of feet of pipe would be required. While this might be technically feasible if sufficient space for pump and motor sets were available, the cost associated with the necessary ship modifications, particularly the addition of high-pressure piping, would make ship retrofit with the current generation of water mist systems not feasible overall. Thus, the cost-effective approach to ship retrofit would be to install HFC-227ea-based gaseous flooding systems that would make maximum use of existing halon 1301 hardware. Technical Feasibility and Cost Based on discussions with naval personnel and NAVSEA engineers, the committee believes that retrofitting with HFC-227ea is technically feasible subject to the constraints cited above. This view is corroborated by results of a recent study of four ship classes by the Navy wherein it was determined that retrofit with HFC-227ea was indeed feasible. The cost and the impact on weight and space are shown in Table 4.4. While the water mist system shows considerable promise for new ship designs, the belief is that HFC-227ea would be the less costly retrofit approach. Further, the Navy technical community feels it is premature to make a judgment as to the retrofitability of a water mist system given its state of relative immaturity, a position with which the committee agrees. The committee thought a rough estimate of the cost of converting the Navy' s current fleet from halon 1301 to HFC-227ea would be informative. In reviewing the results of the detailed ship studies (see Table 4.4), it was noted that the total cost for hardware, agent, and installation for each ship, arrived at quite independently, was about $82 per pound of currently installed halon 1301, a minimum estimate. Applying this factor to the amount of halon aboard today's ships yields a figure of about $120 million as the cost of conversion from halon 1301 to HFC-227ea. To this must be added the cost of ships not yet built (principally DDG-51s), necessary engineering support and testing, and an estimation reserve. Thus, for $200 million to $300 million the Navy could equip all its ships with non-halon fire extinguishing systems. This figure would of course decrease over time as ships retire from active service.

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--> Table 4.4 Estimated Impacts and Cost for Backfit of HFC-227ea in Selected Ships SPACE 125-LB HALON HFC-227 ea PER SHOT TOT CYL DELTA CYL WT DELTA PIPE WT DELTA SQ FT DELTA MATL COST ($) INSTL COST ($) SHIP: LHA-1a                 MMR1 19 48 29 12,760 3,154 45 135,822 118,320 MMR2 23 58 35 15,400 3,806 55 164,072 142,800 AMR 8 20 12 5,280 1,305 19 56,500 48,960 EDGR1 5 13 8 3,520 870 13 36,947 32,640 EDGR2 3 8 5 2,200 544 8 22,822 20,400 JP5 FWD 2 5 3 1,320 326 5 14,125 12,240 JP5 AFT 1 3 2 880 218 3 8,697 8,160 FPR FWD 4 10 6 2,640 853 9 28,250 24,480 TOTAL       44,000 10,875 156 $467,235 $408,000 TOTAL WT CHANGE (LB)     54,875       TOTAL EST COST           $875,235 SHIP: LHD-1b                 MMR1 38 48 58 25,520 3,154 91 168,012 236,640 MMR2 46 58 70 30,800 3,806 109 202,922 285,600 AMR 20 25 30 13,200 1,631 47 87,275 122,400 EDGR1 5 13 8 3,520 870 13 36,947 32 640 EDGR2 3 8 5 2,200 544 8 22,822 20 400 JP5 FWD 4 10 6 2,640 653 9 28,250 24,480 JP5 AFT 3 × 60 4 4 852 435 6 12,212 16,320 LCAC PR 3 × 60 4 4 852 435 6 12,212 16,320 HOLD #10 6 15 9 3,960 979 14 42,375 36,720 AVN 2 × 95 4 4 928 435 6 12,644 16,320 1-103-1-A 1 × 15 1 × 60 1 68 109   2,147 4,000 2-H-0-K 4 × 60 5 5 996 544 8 15,913 20,400 2-13-1-K 2 × 10 1 × 60 1 0 109 2 2,147 4,000 2-13-7-Q 1 × 95 2 2 464 218 3 6,322 8,160 TOTAL       86,000 13,920 322 $652,201 $844,400 TOTAL WT CHANGE (LB)     99,920       TOTAL EST COST           $1,496,601 SHIP: CVN-68a                 EDGR1 5 13 8 2,560 870 13 36,947 32,640 EDGR2 4 10 6 1,920 653 9 28,250 24,480 JP5 #2 4 10 6 1,920 653 9 28,250 24,480 JP5 #3 3 8 5 1,600 544 8 22,822 20,400 STRM 2 × 15 LB 1 × 95 LB 1 80 0 -2 2,759 4,080 STRM 2 × 15 LB 1 × 95 LB 1 80 0 -2 2,759 4,080 HAZMAT 1 3 2 640 218 3 8,697 8,160 TOTAL       8,800 2,936 39 $130,484 $118,320 TOTAL WT CHANGE (LB)     11,896       TOTAL EST COST           $248,804

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--> SPACE 125-LB HALON HFC-227 ea PER SHOT TOT CYL DELTA CYL WT DELTA PIPE WT DELTA SQ FT DELTA MATL COST ($) INSTL COST ($) SHIP: DDG-51b                 ER1 20 25 30 13,200 3,263 47 87,275 122,400 ER2 22 28 34 14,960 3,98 53 98,192 138,720 AMR1 10 13 16 7,040 1,740 25 45,827 65,280 GEN RM 6 15 9 3,960 979 14 42,375 36,720 GTM 1A/B 2 × 95 2 × 125 2 88 0 3 4,379 8,160 GTM 2A/B 2 × 95 2 × 125 2 88 0 3 4,379 8,160 SSGTG1 2 × 95 2 × 125 2 88 0 3 4,379 8,160 SSGTG2 2 × 95 2 × 125 2 88 0 3 4,379 8,160 SSGTG3 2 × 95 2 × 125 2 88 0 3 4,379 8,160 FLSR 1 × 60 2 × 95 2 496 109 2 3,869 8,160 FL ISSUE 2 × 15 1 × 95 1 60 0 -2 2,759 4,080 TACTAS 2 × 125 (Deleted-sprinkling) -880 0 -3 3,000 15,000 TOTAL       39,276 9,788 152 $305,192 $431,160 TOTAL WT CHANGE (LB)     49,064       TOTAL EST COST           $736,352 a Technical feasibility and cost confirmed by detailed engineering study. b Technical feasibility and cost estimate based on preliminary study. SOURCE: Naval Sea Systems Command. Aircraft Retrofit HFC-125 is the gaseous agent selected by the military services as an acceptable replacement for halon 1301 in aircraft. As with HFC-227ea in the ship case, a greater weight of agent will be required to achieve the required extinguishing performance—two and one-half to three times the weight of halon 1301 required. Since inert gas generator technology has not yet reached operational status and such a system must be specifically tailored for each aircraft design, the gas generator is not considered a retrofit candidate at this time by either the committee or the NAVAIR engineers. NAVAIR provided Table 4.5, which depicts the retrofit potential of HFC-125 into the Navy's current fleet of aircraft. Note that the Navy considers retrofit technically feasible for all planes with the exception of the P-3, and even it could be accommodated if absolutely essential. Based on the information given in Table 4.5, discussions with naval personnel, and inspection of typical aircraft installations, the committee concurs that HFC-125 can be satisfactorily retrofitted into current aircraft at some penalty in weight. Using a methodology similar to that employed in determining the investment in current halon 1301 systems, NAVAIR estimates that it would cost about $620 million to convert the current fleet, a figure that includes hardware, agent, engineering design, installation, and testing.

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--> Table 4.5 Naval Aircraft Fire Extinguishing Systems—HFC-125 Retrofit Potential Aircraft Type Number of Aircrafta Applicationb   Weight (lbs)c  Remarks     Engine Other Agent Bottle Plumbing System   Fixed Wing                 P-3d 351 N Y-APU 50 73 13 135   F/A-18 826 Y     36 9 62   A-6E 85 N N-FUEL         Retires 1997 F-14 422 Y Y-OWAC 47 76 14 137   E-2C 123 Y   39 51 4 94   EA-6B 56 Y   90 90 4 184   C-2A 38 Y Y-APU 47 74 4 124   S-3 134   Y-APU 3 27 0.9 31   E-6Ad 16 N Y-APU 40 87 3 129   C-130 109 Y   162 138 28 328   T-44A 45 Y   15 45 6 66   F/A-18E/F 7 Y   17 36 9 62 EMD only C-12 80 Y   15 45 6 66   C-20 7 Y Y-APU 46 79 3 123   T-39 14 Y   39 51 6 96   Rotary Wing                 H-53E 199 Y Y-APU 54 149 6 209   SH-60 369 Y   15 60 3 78   H-53A/D 128 Y Y-APU 41 110 5 155   CH-46 253 Y   18 57 5 80   SH-2 89 Y   15 60 3 78   H-3 100 Y   15 60 3 78   AH- 1 213 Y   12 63 3 78 Current upgrade UH- 1 150 Y   12 63 3 78 Current upgrade V-22 2 Y Y-MW 14 61 3 78 FSD only NOTE: Estimates of platform retrofit weight impact assume a 300% increase in agent and bottle weights and exclude portable fire extinguishers. a The number of aircraft reflect rough estimates, not exact figures. b These columns represent a very rough technical estimate regarding whether a non-ODS system could be volumetrically accommodated. The baseline is a system 300% larger than a halon 1301 system. It does not consider cost or weight factors. There is no HFC-125 retrofit potential in the dry bay application. c Dashes indicate that no retrofit assessment data were available for this analysis. d P-3 and E-6A agent weights include halon 1301 for engine application and HFC-125 for auxiliary power unit application.

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--> Summary, Findings, and Recommendation Halons 1301 and 1211 have served the Navy well as fire extinguishing agents for ships and aircraft since their operational introduction in 1978. Some $1 billion are invested in halon-based fire extinguishing systems hardware, engineering support, testing, installation, and the agent itself, both in platforms or in reserve. Effective alternative chemical agents have been identified by the Navy and are being incorporated into the design of new ships and aircraft. There is a weight and volume penalty associated with these agents relative to halons, but the impact can be minimized if use of these agents is incorporated into the initial platform design. In addition to these chemical replacement agents, there are promising alternative fire extinguishing systems. The Navy is currently studying and testing water mist and inert gas generator systems and is incorporating these systems into its new-design platforms. It is technically feasible to retrofit, into existing platforms, non-halon fire extinguishing systems equipped with the replacement chemical agents selected by the Navy for its new-design ships and aircraft. Such a program would cost about $1 billion if executed in the near term, with the amount diminishing over time as ships and aircraft retire from service. The Navy has sufficient halon 1301 agent in hand to support halon-equipped ships and aircraft until they go out of service. However, inventory projections point to a marginal reserve in the 2030 time period. To hedge against uncertainty, miscalculation, or unanticipated high future usage, the Navy could consider increasing its safety margin by buying recycled halon 1301 in the near term while prices are at a reasonable level. Alternatively, the Navy could consider installing non-halon fire suppression systems in selected new-construction vessels, such as the DDG-51, thereby increasing the halon 1301 reserve by some 400,000 pounds. FINDING: Effective alternative chemical agents have been identified by the Navy and are currently being incorporated into the design of new ships and aircraft. There is a weight and volume penalty associated with these agents relative to halons, but the impact can be minimized if use of these agents is incorporated into the initial platform design. Further, retrofit of these agents into existing naval platforms is technically feasible in most cases. FINDING: In addition to the chemical replacement agents, promising alternative fire extinguishing systems such as water mist systems and inert gas generators are under consideration by the Navy for some applications. These systems are being incorporated into new-design naval platforms. Options The committee sees several options available to the Navy for meeting its requirements for ongoing, environmentally acceptable effective fire suppression in its ships and aircraft: Continue on present course. Continue to implement selected alternative fire protection approaches in new-design platforms. This option is based on the assumption that the current supply of halon 1301 set aside for Navy use will be sufficient for the remaining life of existing ships and aircraft. To hedge against a potential shortfall in the halon 1301 inventory, the Navy could consider buying additional recycled halon to augment the Navy bank and/or adopt alternative agents and technologies in current-design ships not yet constructed, such as the DDG-51. Further, the Navy should maintain, at the present level, its scientific and engineering research effort devoted to developing alternative fire suppression agents and technologies.

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--> Plan for retrofit. Draft retrofit engineering plans for contingency use to meet the possible need for retrofit of existing ships and aircraft. This option would involve detailed study of retrofit potential and preparation of engineering plans for installing alternative halocarbon agents, water mist systems, and inert gas generators. Given this preparation, the Navy would be in a position to respond quickly if the use of halon were restricted. Seek the ultimate fire suppression agent. Fund a major research program directed toward finding a drop-in replacement for halon. Recommendation The committee supports continuation of the present course and does not recommend that the Navy underwrite a major new program to seek the ultimate halon 1301 replacement agent.