ENCLOSURE (3)

EVALUATION OF VARIOUS FIRE SHIELDING TECHNIQUES

EXECUTIVE SUMMARY

The objective of this effort was to identify fire shielding/insulation materials which are capable of protecting KEVLAR armor, as installed inside FFG-7 vital compartments, for a minimum of thirty minutes from a raging or smoldering fire. A fire box was fabricated which held the candidate fire shield materials, Figure 1. To simulate the shipboard installation, a KEVLAR-reinforced plastic (KRP) armor panel was located directly above the insulation; a 1/4" aluminum plate on top represented the superstructure. An 8" diameter propane burner placed on fire bricks in the bottom of the fire box was used as the heat source. A temperaturetime profile representative of ASTM E-119 conditions was used. This presented a temperature of about 800°C to the front surface of the insulation. Thermocouples were located at each material interface. The most important temperature was that of the front surface of the KRP; this was not to exceed 200°C, so as to prevent outgassing of any toxic products. In addition to keeping the front surface temperature of the KRP low, the fire shielding material was not to lose its physical integrity, melt, add any significant weight penalty, or cause problems in installation.

Table 1 summarizes the temperature data for twenty tests performed. Initial tests were based on use of the existing 2" thick fiberglass thermal insulation (Hullboard) and the addition of other materials to provide added fire protection. Refractory type materials were subsequently evaluated as felts, papers and boards. Six insulation systems met the above criteria. Five of the systems required multiple layers. A refractory felt material provided the best fire shielding, in that after 30 minutes exposure it kept the KRP armor front surface to a lower temperature than any other system. This material could be used to directly replace Hullboard and would provide the same thermal insulation for temperature control of the vital compartments. Although both 1-1/2" and 2" of the refractory felt met the criteria, the 1-1/2" thickness was selected based on the lower weight. The refractory felt insulation recommended is 4 lbs/cu.ft. Fiberfrax Lo-Con blanket manufactured by the Carborundum Co., Niagara Falls, New York.

ENCLOSURE (4)

FFG-7 QUARTER SCALE FIRE TEST FOR THE TORPEDO MAGAZINE

SEQUENCE No. 1E

EXECUTIVE SUMMARY

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The objective of the twenty quarter scale fire tests was to establish the ability of the KEVLAR armor (1/2 inch thickness)/refractory felt insulation (1-1/2 inches thickness) system to withstand fires of varying intensity and to relate these fire conditions to what one might expect in real life situations. Both KRP (Derakane 510A40) and KEVLAR blanket armors were evaluated in a quarter scale model of the FFG-7 Torpedo Magazine. Figure 1 gives the dimensions of the quarter scale, fire test chamber. Table 1 summarizes the test conditions for the twenty tests conducted. two tests, Nos. 19 and 20, the candidate armors and their protective refractory felt insulation were penetrated by fragment simulators. During the test program, the severity of the fire was gradually increased. Initially one propane burner was placed in the corner, a one hour burn time was used and both doors were open. These conditions caused no damage to either armor system. The final test condition used two eight inch diameter propane burners for two hours with the burners centered and against the two large weather bulkheads having the KEVLAR armor/refractory felt insulation and one door closed. Fire test 18 subjected the undamaged KRP armor to the most severe fire stress; i.e., 2.47 BTU/S/ft2. Table 2 summarizes the equivalent quantity of other fuels which would be required to generate an equivalent heat load; i.e., 220,000 BTU/hr.

During the 17 tests conducted to simulate a raging fire, the temperatures on the face of the refractory felt insulation ranged from 700° to 800°C. In the ceiling above the burners, the range was 550° to 890°C. The temperature range for the entire ceiling was 500° to 700°C. These fire conditions were sufficient to ignite any combustible materials in the ceiling as well as inside of the compartment. However, no paint, cables, nor hotel furnishings were present. The two propane burners were the only heat source.

Table 3 summarizes the gas analysis data for fire test 18. The data indicate that the fire was clean burning and that the KRP armor did not increase the fire hazard nor act as a source of combustible materials. Gas analyses conducted during the twenty fire tests showed that the carbon dioxide (CO2) concentrations ranged from 5 to 11% (vol.). The carbon monoxide (CO) concentrations ranged from 10 to 800 ppm. The maximum CO concentrations were observed within the first twenty minutes of the test when the sizing and adhesive, which is used to hold the glass mat facing

on the refractory felt and hullboard insulation, pyrolyzed. The total hydrocarbons, reported as methane equivalence, ranged from 0.04 to 7.5 ppm. The low concentrations of carbon monoxide and hydrocarbons observed indicates that the fire conditions were consuming the combustible materials to give the complete combustion products carbon dioxide and water. The concentration of hydrogen cyanide (HCN) ranged from 0.1 to 10 ppm. The hydrochloric acid Drager tubes indicated that the combusion products were acidic with apparent concentration from 5 to 10 ppm being observed. Styrene was not detected while propane was being burned. After the burners were extinguished, the styrene concentration was less than 50 ppm. The concentration of acrolein for the fire tests with undamaged armor/ insulation system ranged from <0.05 to <0.01 ppm. A maximum acrolein concentration of 0.04 ppm was observed during fire tests using the KRP (Derakane 510A40)/refractory felt system that had been penetrated by fragment simulators so that the flames impinged on the holes.

The following conclusions are based on the data obtained in the quarter scale fire tests.

(a) Neither KEVLAR blanket nor KRP (Derakane 510A40) when protected by the refractory felt insulation will burn. These KEVLAR armors will not increase the fire hazards caused by either a low intensity, smoldering or an intense, raging fire. They will not act as a source of combustible materials.

(b) If the protection of the insulation is lost due to enemy action (hole caused by a fragment), the damage, charring, to the KEVLAR armor will be localized and confined to the immediate area of the fragment hole. Charring will only occur when flames impinge on the fragment hole.

(c) When protected by the refractory felt insulation, neither the KEVLAR blankets nor the KRP (Derakane 510A40) will generate toxic combustion products in a concentration sufficient to increase the hazards of either a low intensity, smoldering or an intense, raging shipboard fire.