Document 85EMQ6eoR34RkE5e7agRb0wMy

MILITARY SPECIFICATION MIL-F-24385F FIRE EXTINGUISHING AGENT, AQUEOUS FILM FORMING FORM (AFFF) LIQUID CONCENTRATE, FOR FRESH AND SEAWATER Patricia A. Tatem and Clarence Whitehurst Navy Technology Center for Safety and Survivability Naval Research Laboratory Washington, DC 20375 (202) 767-6965 (202) 767-1716 FAX tatem@ccs.nrl.navv.mil Ralph Ouellette and Robert L.Darwin Hughes Associates, Inc 3610 Commerce Drive, Suite 817 Baltimore, MD 21227 (410) 737-8677 (410) 737-8688 Douglas Barylski Naval Sea Systems Command Washington, DC 20376 Summary of Current Military Specification Military Specification MIL-F-24385F (SH) is approved for use by all departments and agencies of the Department of Defense. This specification covers the requirements for aqueous film-forming foam (AFFF) liquid concentrate fire extinguishing agents consisting of fluorocarbon surfactants and other compounds, as required, to conform to this specification. There are other specifications, standards, and publications (government and non-government) that form a part of this military specification to the extent specified in the MILSPEC. MIL-F-24385F (SH) has specific chemical and physical requirements to which AFFF concentrates and solutions must conform for inclusion on the Qualified Products List QPL-24385-31 (30 October 1998 superseding QPL-24385-30, 30 September 1998). These requirements include conformance to concentration as determined by refractive index and fluorine content: corrosivity (pH, total halides, general and localized corrosion); storage issues related to compatibility with other QPL agents and stability based on aging of the agent (measured by stratification and precipitation); environmental impact as determined by biodegradability factors, specifically, chemical oxygen demand (COD) and biological oxygen demand (BOD) and toxicity (short term measurement for salt water Killifish); performance as a film forming agent (dry chemical compatibility, film formation and sealability, viscosity, spreading coefficient, and foamability), and, US00000001 finally, fire performance on a 28 and 50 sq ft unleaded gasoline pool fire. Tables 1 through 6 gives the Specification requirements for Type 3 and Type 6 concentrates and also results for a recent 6% candidate submitted for conformance to the Specification. Table 1. Chemical and Physical Requirements for Concentrates or Solutions R e q u irem en t R efractive index, m inim um V iscosity (C entistoke) M axim um @ 5C M inim um @ 25C H ydrogen Ion C oncentration (pH ) P ass / F ail C riteria* 1 .3 58(1.3630) 6 % C a n d id a te R esu lts 1.3595 10 (20) 2 7 .0 to 8.5 9 .0 8 6.3 7.6 Spreading C oefficient, dynes/cm , m inim um 3 5.4 F ilm F orm ation and Sealability Foam ability: F oam E xpansion R atio, m inim um F re sh A g en t Test: F re sh W a te r / S e a W a te r Stability T est, concentrate: F resh W ater / Sea W ater Stability T est, solution: F resh W ater / S e a W a te r C o m p atib ility T ests: F re sh W a te r / S e a W a te r N o sustained ig n itio n 5.0 N o sustained ig n itio n 9 .0 / 8.2 9 .1 / 8.8 9 .6 /9 .1 5 .1 /7 .9 F o am 25% D rainage T im e, m inutes, m inim um F re sh A g en t Test: F re sh W a te r / S e a W a te r Stability T est, concentrate: F resh W ater / Sea W ater Stability T est, solution: F resh W ater / S e a W a te r C o m p atib ility T ests: F re sh W a te r / S e a W a te r 2 .5 4.2 5 /4 .2 0 3 .5 /4 .2 5 4 .0 /4 .0 3 .1 5 /4 .0 C o rro sio n R ate: G eneral C old rolled. L o w carb o n steel (U N S G 10100) m ili in/yr, m axim um C opper-N ickel (90-10) (U S C 70600) m ili in/yr, m axim um N ickel-C opper (70-30) (U S N 04400 m ili in/yr, m axim um B ronze (U N S C 90500), m illigram s m axim um L ocalized, corrosion-resistant (C R E S) steel, U N S S30400) 1.5 1.0 1.0 100 N o pits 0 .6 9 0 .0 2 0 .0 3 0 .0 3 N o pits T otal H alid es, pp m m axim um D ry chem ical com patibility, burn -back resistance tim e 360 seconds m inim um E n v iro n m en tal im pact: T o x ic ity , L C 50 m g /L , m in im u m C O D , m g/L , m axim um BODTM COD m inim um F luorine content, m g/L 250 (500) 360 1,000 (500) 5 x l 0 5 ( 1 X 1 0 6) 0 .6 5 186 427 >1000 2 7 9 ,0 0 0 0 .8 0 5,250 m g/L S tratification : Stability T est C om patibility T est N one N one N one N one US00000002 P recip itatio n , % by V olum e: Stability Test C o m p a tib ility T est, 1:1 R a tio M ix e s C om patibility T est, A ll A g en t M ix C ontainer cap opening torque (average) < 0 .0 5 < 0 .0 5 < 0 .0 5 50 in-lbs m ax < 0 .0 5 < 0 .0 5 < 0 .0 5 <50 in-lbs m ax *Numbers in parentheses are for Type 3 if different from Type 6. The refractive index is determined at 25C j^0.1C, using sodium vapor source lamp illumination. The viscosity is determined at temperatures of 5C+0.1C and 25C+ 0 .1C in accordance with ASTM D445-74, using capillary viscometers in the appropriate size. The viscosity requirement is based on the mechanics of the current Navy piping system and relates to the pressure loss in pipes as a function of factors such as pipe length and pipe diameter. Viscosity and refractive index requirements, not its fire performance, drive the presence of other compounds in candidate formulation (i.e., diethylene glycol monobutyl ether, ethylene glycol and detergents). Methodology for determining the fluorine content is not specified in the MILSPEC. The requirement is that the test procedure used for the determination and the total fluorine content be furnished as part of the qualification inspection report. Fluorine content is more of a quality control issue rather than pass/fail criteria. If using an optical absorption technique, it is more amenable to laboratory rather than shipboard use. The pH value is determined potentiometrically, using a pH meter with a glass electrode and a reference electrode, at 25C+1.0C. This corrosivity requirement is intended to minimize corrosion of metallic plumbing and storage containers. For general and localized corrosion, test coupons are evaluated for weight loss or visible pitting. As seen in Table 1, various types of coupons, in accordance with UNS designations, are evaluated according to ASTM E527 for weight loss (general corrosion) and for visible pitting (localized corrosion). The total halides measurement to evaluate for potential metallic corrosion is determined in accordance with ASTM D1821, with minor modifications. The terminology "total" is misleading because the method is more applicable to determining "free" (inorganic salt) chloride and bromide. Fluoride is not likely determined by this method. The environmental impact of the candidate agent is measured, firstly, in terms of its effect on the Killiefish (Fundulus herteroclitus) in accordance with ASTM E729, using dynamic procedures. The minimum acceptable dissolved oxygen content of water used in this procedure shall be 5p/m (ppm?). Killifish toxicity is a measure of short-term toxicity for salt water fish. There is a limited season on Killiefish, which presents a problem occasionally when attempting to qualify agents. AFFFs are historically considered relatively non-toxic by this short-term measure. COD is determined in accordance with procedures in Standard Method for the Examination of Water and Waste Water (latest applicable edition). Biodegradability is determined by dividing the value expressed in mg/L for the 20-day BOD2o determined from 5-day BOD test in accordance with the procedure specified in Standard Methods for the Examination of Water and Waste Water (latest applicable edition) by the value expressed in mg/L for COD as US00000003 expressed previously. This quotient is more applicable where waste runs to small bodies of water in Waste Water Treatment Plants and Sewage Treatment Plants. Storage issues as related to compatibility with other QPL agents and stability based on aging of the agent, as measured by stratification and precipitation, are measured as chemical and physical requirements as well as in fire performance requirements. Samples of concentrate and type 3 AFFF (if evaluated) and type 6 AFFF (if evaluated) fresh water and sea water solutions are subjected to the following evaluations after exposure to 65C + 2.0C for 10 days (stability): a. Spreading coefficient b. Foamability c. Film formation and sealability d. Fire performance (28 sq ft) e. Stratification f. Precipitation In addition, samples of products on the QPL are mixed with the candidate fresh water and sea water solutions (compatibility) and stored at elevated temperatures as above (stability) before being subjected to the following tests: a. Foamability b. Film formation and sealability c. Fire Performance (28 sq ft) d. Stratification e. Precipitation The spreading coefficient is determined with reference to cyclohexane in accordance with the following relationship: a/b= b - a - 8i, where: 8a/b = Spreading coefficient 8b = Surface tension of cyclohexane as determined under Section "Surface Tension" below, 8a = Surface tension of AFFF solution as determined under Section "Surface Tension" below, 8i = Interfacial tension between liquids as determined under Section "Interfacial Tension" below. Surface Tension - The surface tension of 3 + 0.05 percent of type 3 or 6 + 0.1 percent of type 6 by volume in distilled water, as appropriate, and of reagent grade cyclohexane is determined with a DuNoy tensiometer, or equal, at 23C j^2.0C in accordance with ASTM D1331 Interfacial tension - The interfacial tension between 3 + 0.05 percent of type 3 or 6 + 0.1 percent of type 6 by volume in distilled water, as appropriate, and reagent grade US00000004 cyclohexane is determined with a DuNoy tensiometer, or equal, at 23 + 2.0C until the readings come to equilibrium and in accordance with ASTM D1331. Stratification and precipitation measurements are done on all the compatibility solutions and stability solutions. The presence of stratification is determined by visual examination of the candidate sample contained in glass cylinders. The amount of precipitation is determined by centrifuging 100 mL samples after thorough agitation in accordance with the primary method of ASTM D96. Foamability of the candidate samples is checked by means of a special 2 gal/min test nozzle. The basic nozzle, as made by National Foam System, Inc., Lionville, PA (or equal) is modified and the nozzle inlet pressure and solution temperature maintained as quoted in the MILSPEC. The method and procedure followed are is accordance with NFPA 412. Foamability is run on both fresh and sea water solutions of the candidate concentrate (type 3 and/or type 6). Film formation and sealability are usually conducted on the candidate samples once they have passed the 28 sq ft fire tests. This measurement assures that the films formed over the fuel by the candidate samples are capable of maintaining an effective vapor seal to prevent further vaporization of the fuel during fire fighting. The test is performed on the film-forming liquid without most of the residual foam that can be generating when delivering the agent. There is a container cap opening torque requirement of 50 in.-lbs max. This requirement assures that a sailor under the duress of fire fighting is able to open an AFFF container with relative ease. The 28-sq ft fire tests are conducted in a level, circular pan 6 feet in diameter, fabricated from 0.25-in. thick steel with a 4-in. high side. A shallow water layer is used to protect the pan bottom and to ensure complete coverage of the area with fuel. The nozzle used for foam application is the 2 gal/min device used for the foamability measurements. The foam from the candidate agent is generated at 23C + 5.0C from AFFF solutions made with fresh or sea water, as required, at various concentration values given in Tables 2 through 4. Table 2 gives requirements and results for fresh concentrate at full, half and quintuple (sea water only) strengths. Table 3 gives requirements and results for aged concentrates at full and half strengths. Table 4 gives requirements and results for aged solutions at full strength only. Table 5 gives the requirements and results for concentrate compatibility tests for a candidate agent with AFFF agents currently on the QPL. To perform the compatibility fire tests, the candidate agent is mixed individually with each of the QPL products in a 1:1 volume ratio, and with all the QPL products in a 1:1:1 :etc volume ratio. These concentrate mixtures are aged in accordance with the previous "Stability" section and then used to prepare the solutions used for fire performance testing. There are certain procedures that must be followed. Ten gallons of unleaded gasoline fuel are used that conform to ASTM D439. The fuel shall be dumped within a US00000005 30-sec period, ignited within 30 sec of fueling, and allowed to bum freely for 10 sec. After the preburn period, the fire is attacked and extinguished as expeditiously as possible, continuing foam application for a total of 90 sec even if the fire has extinguished. The actual fire extinguishing time cannot exceed the extinguishment requirement criteria in the Tables. Within 60 sec of the completion of foam application, burning pan (1-foot in diameter with 2-in. side) containing one gallon of unleaded gasoline is placed in the center of the 28 sq ft pan and a timer started. When it appears that the fire has spread outside the pan so that burning will continue after pan removal, the pan shall be removed. The burnback time is that time at which it is estimated that 7 sq ft (25 percent) of the total area is involved in flames. Table 2. 28 ft2 Fire Performance Test Results: 6% Candidate Fresh Concentrate. PROPERTY EXTINGUISH ACTUAL BURNBACK ACTUAL MEASURED TIME CRITERIA* TIMES TIME CRITERIA TIMES Fresh Water 30 Sec (Max) 25 360 Sec (Mm) 551 Full Strength Fresh Water 45 Sec (Max) 43 300 Sec (Mm) 436 Flalf Strength Sea Water 30 Sec (Max) 30 360 Sec (Mm) 555 Full Strength Sea Water 45 Sec (Max) 41 300 Sec (Mm) 491 Flalf Strength Quintuple Strength 55 Sec (Max) (15%) SeaWater 40 *Criteria are the same for Type 3 200 Sec (Mm) 325 Table 3. 28 ft2 Fire Performance Stability Test Results: __________ 6% Candidate Aged Concentrate.__________ PROPERTY EXTINGUISHMENT ACTUAL BURNBACK ACTUAL MEASURED TIME CRITERIA* TIMES TIME CRITERIA TIMES Fresh Water Full Strength 30 Sec (Max) 25 360 Sec (Mm) 438 Fresh Water Half Strength 45 Sec (Max) 43 300 Sec (Mm) 345 Sea Water Full Strength 30 Sec (Max) 29 360 Sec (Mm) 472 Sea Water Half Strength 45 Sec (Max) 37 *Criteria are the same for Type 3 300 Sec (Mm) 485 Table 4. 28 ft2 Fire Performance Stability Test Results: 6% Candidate Aged Solution PROPERTY EXTINGUISHMENT ACTUAL BURNBACK ACTUAL MEASURED TIME CRITERIA* TIMES TIME CRITERIA TIMES Fresh Water Full Strength 30 Sec (Max) 27 360 Sec (Mm) 428 Sea Water Full Strength 30 Sec (Max) 23 *Criteria are the same for Type 3 360 Sec (Mm) 472 Table 5. 28 ft2Fire Performance Concentrate Compatibility Test Results: 6% Aged Concentrates. (Solutions for fire performance tests were mixed at full strength) QUALIFIED AGENT PROPERTY MEASURED EXTINGUISH ACTUAL BURNBACK ACTUAL TIME CRITERIA* TIMES TIME CRITERIA* TIMES QPL#1 Fresh Water 30 Sec (Max) 24 360 Sec (Mm) 426 QPL#1 Sea Water 30 Sec (Max) 28 360 Sec (Mm) 428 QPL#2 Fresh Water 30 Sec (Max) 26 360 Sec (Mm) 399 QPL#2 Sea Water 30 Sec (Max) 30 360 Sec (Mm) 370 QPL#3 Fresh Water 30 Sec (Max) 26 360 Sec (Mm) 368 QPL#3 Sea Water 30 Sec (Max) 27 360 Sec (Mm) 438 QPL#4 Fresh Water 30 Sec (Max) 24 360 Sec (Mm) 442 QPL#4 Sea Water 30 Sec (Max) 26 360 Sec (Mm) 457 All of the Above Fresh Water 30 Sec (Max) 24 360 Sec (Mm) 489 All of the Above Sea Water 30 Sec (Max) *Criteria are the same for Type 3 25 360 Sec (Mm) 427 US00000007 The 50 sq ft fire test (Table 6) is performed after all the other performance criteria have been satisfied. The fire test is conducted on a level, circular area 8 feet in diameter. The base and surrounding wall shall be suitable for containment of the fuel on a substrate of water. The water depth is the minimum required to ensure complete coverage of the area with the fuel. The nozzle used for foam application is the 2 gal/min device specified previously and operated at a gage pressure of 100 lb/sq in. Table 6. 50 ft2 Fire Performance Test Results: 6% Candidate Fresh Concentrate PROPERTY EXTINGUISHMENT ACTUAL BURNBACK ACTUAL 40 SECOND ACTUAL MEASURED TIME CRITERIA* TIMES TIME TIMES SUMMATION TOTAL Sea Water Full Strength 50 Sec (Max) *Criteria are the same for Type 3 36 360 Sec (Mm) 406 320 (Mm) 325 The foam is generated at 23C + 5.0C from full strength, sea water type 3 and/or type 6 fresh concentrate. Fifteen gallons of unleaded gasoline fuel is used conforming to ASTMD439. The fuel is dumped into the area in less than 60 sec, ignited in less than 30 sec after fuel dumping, and allowed a prebum of 10 sec. The fire is attacked and extinguished in an expeditious manner. At 10-sec intervals after the start of foam application, observers estimate the percentage of fire area extinguished. The percentages at 10, 20, 30, and 40 sec are totaled to give the "40-sec summation" value. The exact extinguishing time is recorded at the cessation of all flame, but foam application continues for a total of 90 sec. Within 60 sec of the completion of foam application, a bumback test shall be conducted as in the 28 sq ft fire tests, except that the burnback area shall be 12.5 sq ft (25%). History and Evolution of the AFFF Military Specification In 1961, researchers at the Naval Research Laboratory began an in-depth assessment of the potential fire fighting capabilities of a new family of chemicals known as fluorocarbon surfactants. Initial studies showed that foams made from these surfactants rapidly spread over the surface of a hydrocarbon fuel fire, providing much quicker extinguishment times relative to the protein-based foams then in use. The superiority of these new foam agents was attributed to their tendency to form an aqueous film on the fuel surface; which resulted in the adoption of the term "Light Water" or "Aqueous Film US00000008 Forming Foam (AFFF)" . A patent application for this technology was filed in September of 1963 and an initial military specification (Mil-F-23905) was issued two months later. The final patent was awarded in June of 1966, with rights assigned to the Secretary of the Navy. The AFFF described in the initial specification had limited practical application because it was only compatible with fresh water and required a 25 % by volume mixture ratio with water to form an effective foam solution. Within a year, a formulation was developed that reduced the mixture ratio to 6 %, which was the same as for conventional foams then in use by the US military. Large-scale tests at NAS Miramar, CA, confirmed a margin of superiority over protein-based foams of approximately 3 to 1. In early 1968, a joint effort by NRL and the 3M Company produced a formulation that was believed to be compatible with sea water. Testing at NAS Jacksonville, FL, in December of 1968 confirmed the compatibility with sea water and demonstrated the efficacy of deploying the new agent on Navy ships as well as at Naval Air Stations. The report of the Jacksonville tests contained the initial draft of a proposed specification for sea water compatible AFFF, which was formally issued as Mil-F-24385 a year later. As indicated in Table 7, numerous revisions and amendments to the original specifications have occurred over the years. Table 8 summarizes the significant changes to AFFF physical and chemical limits that were incorporated in revisions to Mil-F-23905. Similarly, Table 9 summarizes changes in the required physical and chemical properties that have been made to Mil-F-24385 from 1969 to the present version dated January 7, 1992. The most important changes are as follows: The conversion from a 25 % mixture ratio to a 6 % mixture ratio in 1967 The incorporation of corrosion limits in 1969 The establishment of maximum chloride limits and the incorporation of a dry chemical compatibility test in 1971 The 1972 adoption of a minimum pH value o f " 7 " The incorporation of a "spreading coefficient" as well as environmental limits in 1977 The inclusion of a Type 3 concentrate (allowing a 3 % mixture ratio) in 1981 The tightening of the BOD20/COD ratio in 1992 US00000009 Table 7. Evolution of the AFFF Military Specification Mil-F-23905 23905A Amendment 1 Amendment 2 8/13/65 9/1/66 23905B Mil-F-24385 (replaced Mil-F-23905) Amendment 1 5/11/70 Amendment 2 6/25/70 Amendment 3 7/7/71 Amendment 4 1/14/72 Amendment 5 2/17/72 Amendment 6 6/29/73 Amendment 7 7/24/73 Amendment 8 6/20/74 24385A 24385B Amendment 1 5/16/79 24385C Amendment 1 Amendment 2 Amendment 3 Amendment 4 6/5/81 12/4/81 4/26/82 3/3/83 24385D 24385E 24385F 11/1/63 3/26/65 4/25/67 11/21/69 5/2/77 5/25/78 3/12/81 10/26/89 11/30/90 1/7/92 US00000010 Table 8. Significant Changes to Physical and Chemical Limits Mil-F-23905 (WEP) Fire Extinguishing Agent, "Light Water" Liquid Concentrate Original SpecVersion (11/1/63) Mixture Ratio: 25 % (fresh water only) Ri. 1.335 to 1.337 Viscosity: 22-36 centistokes @ 20 C 57-59 centi stokes @ 0 C pH: 6.7-7.3 Surface Tension: 25-30 dynes/cm2 (1/370 solution) "A" Revision (3/26/65) Mixture Ratio: 25 % (fresh water) pH: 5-6.5 Viscosity: 14-28 cs @ 25 C Surface Tension: 14-22 dynes/cm2 (1/370) Requirement for "fuel vapor sealability" "B" Revision (4/25/67) Mixture Ratio: 6 % (fresh water) pH: 4.2 min Viscosity: 50-150 cs @ 25 C Surface Tension: 20 dynes/cm2 max (1/370) 300 cs @ 4.4 C Requirement for "film formation and sealability" Requirement for "foamability" (Expansion Ratio =7:1 minimum) (1/4 Drainage Time = 2.5 minutes) US00000011 Table 9. Significant Changes to Physical and Chemical limits Mil-F-24385 (Navy) "Fire Extinguishing Agent, Aqueous Film-Forming Foam (AFFF) Liquid Concentrate, for Fresh and Sea Water" Original Spec Version (11/21/69) Mixture Ratio: 6 % (fresh and sea water) pH: 4-8 Surface Tension: 18 dynes/cm2 max Interfacial Surface Tension: 5 dynes/cm2 Corrosion Limits (for steel, aluminum alloy, CRES, 90/10 copper/nickel) Inter-Agent Compatibility Requirements Stability of Aged Agent 1/4 Drainage Time Raised to 3 Minutes Amendment 1 (5/11/70) Increased the "pour opening" to 1 V2 inch Amendment 3 (7/7/71) Lowered 1/4 Drainage Time to 2.5 min Added "no visible pitting" of CRES 304 Limit of 100 ppm max for chlorides Dry Chemical Compatibility test Precipitate < 1 % by volume for aged concentrate Amendment 5 (2/17/72) Changed pH to 7-8.5 US00000012 Table 9 (con't). Significant Changes to Physical and Chemical Limits Mil-F-24385 "A" Revision (5/2/77) Spreading Coefficient limit of 3 minimum Expansion ratio reduced to 6:1 Bronze and 70/30 copper nickel added to corrosion requirements Corrosion expanded to "general" and "localized" limits Environmental limits (TL50 > 1500 ppm, BOD2o and COD < 500,000 mg/1) Cans must be "stackable" and "self supporting" "B" Revision (5/25/78) Environmental limits modified (COD < 500,00 mg/1, BOD2o/COD>.85) Fluorine content shall not deviate more than 15 % Cap opening torque max of 50 in-lbs "C" Revision (3/12/81) Type 3 concentrate added to spec (unique Type 3 limits added to spec) Total halides limit (250 ppm for type 6, 500 ppm for type 3) Current viscosity and toxicity limits established Color coding for containers (blue-type 6, green-type 3) "D" Revision (10/26/89) Revision issued but never implemented ("E" re-invoked "C" version) "F" Revision (1/7/92) Environmental limits changed (BOD2o/COD > .65) Expansion Ratio reduced to 5:1 US00000013 Changes in Fire Performance Requirements In addition to changes in specific physical and chemical limits, there have been considerable enhancements to the required level of fire performance. The evolution of stricter fire performance criteria is shown in Table 10. The incorporation of everincreasing fire performance can be illustrated by the reduction over time in the "maximum allowable extinguishment application density", which is defined as the maximum gallons of AFFF solution required per unit area of fuel surface to achieve total extinguishment. The maximum allowable density dropped from .1 gal/ft2 in 1963 to .08 in 1971, to .054 in 1977, and finally to the current limit of .036 for the 28 ft2 fire and .033 for the 50 ft2 fire. Similarly, the "minimum 40 second summation" has increased from 285 to its current level of 320. The 40second summation imposes a requirement for very rapid fire knockdown. Finally, there has been a corresponding tightening of the allowable "burnback" (the time required for the fire to spread from the burnback pan to involve 25 % of the original fire area). The minimum burnback time has been increased from 240 seconds in 1969 to the current limit of 360 seconds for both the 28 and 50 ft2 fires. Table 10. Evolution of Fire Performance Requirements Spec Version 23905 Spec Date 11/1/63 Fire Flow Area Rate (ft2) (gpm) NR* NR Max Control Time (secs) NR Max Ext Time (secs) NR Max Control Appl Dens (gal/ft2) NR Max Ext Appl Dens (gal/ft2) NR Min Min 40 BB Sec Time Sum (secs) NR NR 24385 11/21/69 28 400 1260 2 16 50 NR 30 30 84 NR NR NR .02 .02 .1 NR 240 NR 285 NR NR 285 NR Amend 7/7/71 3 28 2 NR 65 NR .08 NR 240 Amend 6/20/74 50 8 2 40 NR .027 NR 225 240 24385 A 5/2/77 28 2 1260 60 NR 30 45 NR NR .024 .054 NR 320 NR 285 NR 24385 B 5/25/78 28 50 1260 2 2 60 NR NR 30 30 50 NR NR NR .024 .036 NR 320 .033 300 300 NR 300 NR 24385 C (To Present) 3/12/81 28 50 2 2 NR NR 30 50 NR NR .036 NR 360 .033 320 360 *Not Required US00000014 Fire testing is also required to demonstrate adequate performance of "aged" AFFF concentrate and "aged" AFFF solution ("aging"is simulated by storage at 65 0 C for 10 days), and also to show that concentrate from one manufacturer can be safely mixed with any other concentrate previously qualified. Dry chemical compatibility must also be demonstrated by successfully passing a burnback test in the presence of potassium bicarbonate powder. An additional fire test requirement was incorporated in the "A" revision to the current specification in 1977 to assure adequate performance for "misproportioned" foam solution. At the time, Navy shipboard foam proportioned were very inaccurate and it was considered necessary to assure some level of fire fighting capability for both "lean" and "rich" solutions. Tables 11 and 12 summarize the performance required by revision "A" and the change incorporated in revision "C", which still applies in the current version of the specification. Table 11. Test of Mis-Proportioned Foam Solution __________ MU-F-24385A (28 ft2 fire)__________ 6 % 3 % 50 % (SW) Max Ext Time 45 secs 65 secs 55 secs Burnback Time 320 secs min 240 secs min 100 secs min Table 12. Test of Mis-Proportioned Foam Solution M-F-24385C to Present (28 ft2 fire) Full Strength V2 Strength 5 x Strength (SW) Max Ext Time 30 secs 45 secs 55 secs Burnback Time 360 secs min 300 secs min 200 secs min As indicated in Table 12, foam solution at "half strength" (3 % of type 6, or 1.5 % of type 3) must achieve total extinguishments in 45 seconds as opposed to only 30 seconds for a full strength foam solution. A solution of 5 times full strength (30 % of a type 6, or 15 % of a type 3), made with sea water, must achieve total extinguishments of the same size fire within 55 seconds. Maximum allowable burnback times are also shown. Rationale for Specification Requirements The establishment of specific limits on AFFF physical and chemical characteristics, as well as the imposition of minimum levels of fire performance, has evolved in an attempt to provide the best flammable liquid fire fighting agent for military applications. While some requirements have resulted from the unique nature of Navy shipboard foam systems, most changes that have resulted over the years are beneficial improvements to common shore applications as well. Table 13 provides the underlying rationale for various requirements in the current AFFF specification. US00000015 Table 13. Rationale for M il-Spec requirements Spec Requirement Refractive index Viscosity PH Corrosivity Total halides Environmental limits Accelerated aging test Sea water compatibility Inter-agent compatibility Half and 5 x strength Rationale for Requirement Enables use of refractometer to measure solution concentrations in field (method recommended in NFPA 412) Assures accurate performance through pumps and orifices Assures concentrate is not acidic or excessively basic Limits corrosion of and deposit build-up on metallic components Limits corrosion Reduces environmental impact Assures a long shelf life Assures satisfactory performance with brackish or sea water Allows storage tanks to be topped off with concentrates of different manufacturers Assures adequate performance for mis-proportioned foam Dry Chem Compatibility Torque to remove cap Packaging Qualification testing Quality assurance tests Spreading coefficient Film formation/sealability Fire extinguishments tests Bumback tests Allows "twin agent" application Able to remove cap by hand in field Assures uniformity of containers and ease of handling (strength, stackable, color, size, pour opening, tamper proof seal) Establish conformance with requirements Assure continued conformance of future lots Provides film formation capability Assures film formation on fuel Ultimate measure of effectiveness Assures foam stability and firefighter safety US00000016 References Military Specification, Mil-F-23905 (WEP), "Fire Extinguishing Agent, "Light Water" Liquid Concentrate," 1 November 1963 (and all revisions and amendments thereto). Military Specification, Mil-F-24385 (Navy), " Fire Extinguishing Agent, Aqueous Film Forming Foam (AFFF) Liquid Concentrate, For Fresh and Sea Water," 21 November, 1969 (and all revision and amendments thereto). United States Patent # 3,258,423," Method O f Extinguishing Liquid Hydrocarbon Fires," Richard L. Tuve and Edwin J. Jablonski, assignors to the United States of America as represented by the Secretary of the Navy, June 28, 1996. Peterson,H.G., Jablonski, E.J., Neil, R.R., Gipe, R.L., and Tuve, R.L.," Full Scale Fire Modeling Test Studies of Light Water and Protein Type Foams," NRL Report 6573, August 15, 1967. Peterson, H.B., "A Brief Summary of Fire Tests with "Light Water" Concentrates for Use with Sea Water," NRL Letter Report, October 15, 1968. Darwin R. L., and Jablonski, E. J., "Full Scale Fire Test Studies of Sea Water-Compatible "Light Water" as Related to Shipboard Fire Protection," Naval Ship Engineering Center, August 25, 1969. Scheffey, J.L., Darwin, R.L., Leonard, J.T., Fulper, C.R., Ouellette, R.J., and Siegmann, C.W., " A Comparative Analysis of Film Forming Fluoroprotein Foam (FFFP) and Aqueous Film Forming Foam (AFFF) for Aircraft Rescue and Firefighting Services," Hughes Associates, Inc. Report 2108-A01-90 for the NFPA Aviation Committee, June 1990. US00000017