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Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
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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?

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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

 

 

 

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

Table 4.3 FY 96 Navy Halon 1301 Projections and Navy Reserve

 

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

 

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×

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:

  1. 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.
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
  1. 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.
  2. Seek the ultimate fire suppression agent. Fund a major research program directed toward finding a drop-in replacement for halon.
  3. 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.

Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 45
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
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Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 47
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
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Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 49
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 50
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 51
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 52
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 53
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 54
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 55
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 56
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 57
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 58
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
Page 59
Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
×
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Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
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Suggested Citation:"NAVY-SPECIFIC ISSUES." National Research Council. 1997. Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications. Washington, DC: The National Academies Press. doi: 10.17226/5744.
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