US2897151A - Vaporizing fire extinguisher fluid - Google Patents

Description

United States Patent 9 Keith H. Birkett, Hickman Mills, Mo., assignor to Superior Products Company, Kansas City, Mo., a corporation of Missouri No Drawing. Application September 7, 1956 Serial No. 608,431

2 Claims. (Cl. 252-8) This invention relates to fire extinguisher fluids and refers more particularly to fire extinguisher fluids particularly adapted to be employed in glass bulb vaporizing fire extinguishers.

It is generally'assumed thatthe effect of fire extinguishing agents can be explainedon the basis of the following actions:

(1) Cooling action, which lowers the temperature of the combustible material below its ignition temperature.

(2) Blanketing action, which prevents air from reach ing the fire and results in the dilution of the oxygen content of the surroundings.

(3) Mechanical action, which results from directing the agent across the fire with sufiicient force to cut the flame away from the combustible material.

Studies in the recently developed field'of chemical kinetics also indicate that certain substances are capable of exerting an inhibiting effect in the combustion reactions. This chemical action is not completely understood and has not yet been extensively utilized in the search for better fire extinguishing agents.

Cooling action is a function of the physical properties of the agent, that is, heat capacity, thermal conductively, and the heat of vaporization will be of different magnitude for different agents. The cooling action obviously is also a function of the amount of agent em- 2,897,151 Patented July 28, 1959 fire extinguishing fluids not containing carbon tetrachloride for use in glass bulb vaporizing fire extinguishers.

Another object of the invention is to provide fire extinguishing fluids not containing carbon tertrachloride for use in glass bulb vaporizing fire extinguishers, which fluids have greater efiiciency as extinguishing agents than carbon tetrachloride.

Another object of the invention is to provide fire extinguishing fluids not containing carbon tetrachloride for use in glass bulb vaporizing fire extinguishers, which fluids have far less toxicity than carbon tetrachloride when pyrolyzed in quenching a fire.

Another object of the invention is to provide such fire extinguishing fluids which have very high blanketing action whereby to prevent air fromreaching the fire and diluting the oxygen content of the surrounding area i of the fire..

ployed. With most extinguishing agents, except water and highly compressed carbon dioxide, the amounts are small and the cooling action is of only secondary importance.

Since the glass bulb type of fire extinguisher does not give the mechanical action, it therefore must depend solely upon the blanketing action of the fluid.

Previous studies have indicated that some halogenated hydrocarbons are suitable materials for use in the glass bulb type fire extinguisher. In commercial and industrial as the agent of choice in glass bulb type fire extinguishers. Carbon tetrachloride, while possessing a certain amount of usefulness as a fire extinguisher fluid, has less efliciency than is desired as an extinguishing agent in its blanketing action and also is undesirably toxic in use. Carbon tetrachloride produces much larger quantities of phosgene and decomposes at lower temperatures than other chlorinated hydrocarbons. In the inventive extinguisher fluids to be herein disclosed certain compounds employed therein produce hydrogen chloride when pyrolyzed which acts as an olfactory warning agent long before enough phosgene forms to become dangerous. Carbon tetrachloride does not form hydrogen chloride on heating before the phosgene reaches the dangerous level. When pyrolyzed, carbon tetrachloride was at a minimum six'times more toxic than any of the compounds employed in the inventive extinguisher fluids. This condition would occur during a fire since the liquid would often fall on a hot surface and be pyrolyzed, giving off toxic fumes.

, use, previously, carbon tetrachloride has been employed Therefore, an object of the invention is .to provide Another object of the invention is to provide fire extinguishing fluids as described which will produce hydrogen chloride in quantities to provide an olfactory warning agent before enough phosgene has formed to become dangerous. 7

Another object of the invention is to provide fire extinguishing fluids as described having a relatively low cost compared to conventional extinguishing fluids including carbon tetrachloride.

Another object of the invention is to provide fire extinguisher fluids as described which have a relatively high Maximum allowable concentration (the upper limit of concentration of a compound in the air which will not cause injury to an individual exposed continuously during a working day and for indefinite periods of time) relative carbon tetrachloride.

Another object of the invention is to provide a fire extinguishing fluid as described having a relatively high protected volume" (the vapor volume generated at 200 F. divided by the inflammability peak percentage expressed as a decimal fraction-carbon tetrachloride having a protected volume of 392 cubic feet per gallon and a higher value being desired in an improved extinguishing fluid).

Another object of the invention is to provide fire extinguishing fluids as described having extremely low freezing points (below 30 F.).

Other and further objects of the invention will appear in the course of the following description thereof.

Maximum allowable concentration of vapors A useful concept in evaluating fire extinguishing fluids is the maximum allowable concentration? (M.A.C.). This is defined as the upper limit of concentration of a compound in the air which will not cause injury to an individual exposed continuously during a working day and for indefinite periods of time. In setting the M.A.C. from field studies and animal experiments, certain criteria are usually followed:

(1) Illness due to intoxication should not result from continued exposure to the M.A.C.

(2) Marked discomfort to a majority of workers should not result from continuous exposure to the M.A.C.

(3) The M.A.C. should not exceed one tenth the concentration dangerous for a single exposure of one hour.

(4) Where only animal experimental data is available, the M.A.C. should not exceed one fifth the concentration found to effect animals seriously on continued exposure.

A concentration of 2.5 times the M.A.C. should fail maximum allowable concentrations are useful guides in assessing the relative toxic hazards of various materials on a quantitative basis.

Liquid volume Liquid volume in ml.

(M.A.C. in D.P.M.) Xmoleeular weight (.86 cu. ft./g. mol specific gravityX 1,000) The liquid volume calculation for carbon tetrachloride is 2.8. Once again, a much greater value is desired in a fire extinguisher fluid.

Protected volume The protected volume term is calculated from the inflammability peak and the vapor volume generated at 200 F. It is computed by dividing the vapor volume generated at 200 F. by the inflammability peak percentage (expressed as a decimal fraction). Carbon tetrachloride has a calculated protected volume of 392 cubic feet per gallon. A higher value is desired in an improved extinguishing fluid.

Empirical extinguishing number A 2.8 cubic foot (22.4 liters) steel kettle fitted with a Lucite top was used in experiments to compare extinguisher fluids. The material to be tested was dropped in through a thistle tube into a dish in the container. A circulating fan which had been placed in such a position as to blow onto the dish was then turned on to evaporate the liquid. An inflated vinyl plastic bag within the kettle was allowed to deflate through a tube to the atmosphere which compensated for the expansion of the liquid when vaporized and mixed. The vinyl bag was then slowly inflated again and the displaced vapor in the kettle was passed out through a one inch hole into a 3" x 14" cylinder. In the center of the cylinder was placed a burning cigarette lighter. If the fire extinguisher fluid concentration was too high, the flame of the lighter would be extinguished. The quantities of each fire extinguisher fluid added to the tank were varied until there was only a dilference of one ml. between the point of burning and the point of extinguishing. The volume of liquid required to extinguish the flame varied for each extinguishing agent. This volume was termed the empirical extinguishing number. This figure is useful since it shows the relationship between extinguishing agents and the relative amounts required to put out a fire.

Olfactory warning agents Carbon tetrachloride produces larger quantities of phosgene and decomposes at lower temperatures than other chlorinated hydrocarbons. Since chlorinated ethanes, having at least one hydrogen atom, form hydrogen chloride more readily than chlorinated methanes, which acts as an olfactory warning agent long before phosgene has formed in sutficient quantity to become dangerous, it was desirable to include at least one chlorinated ethane which would not increase the toxicity or cost or lower the extinguishing ability of the fluids.

Practical extinguishing tests The most positive method for obtaining information on the fire extinguishing eflectiveness of different substances is obviously by direct application to test fires.

4 Consequently, a 512 cubic foot shed was built to evaluate the extinguisher fluids.

Paper towels soaked in kerosene and placed in trays were used as the test fires in the shed. A tray 3 x 3' was selected for use from several sizes studied. The amount of kerosene was varied to determine the amount necessary to maintain the flame throughout the test. After many trials, two quarts of kerosene were found to be the most suitable for the standard fire.

In a test of this nature, it is diflicult to compare the extinguishing ability of several difierent fluids. In order to compare carbon tetrachloride with other fluids it was necessary to adjust conditions in the shed so that carbon tetrachloride would not function properly all the time. This should mean that some of the time it would take a long time to put out the fire and other times it would not put it out. The optimum would be for it to function 50 percent of the time. By doing this fluids which were assumed to be more efiicient could be tested. The efficiency could be shown by less time required to put out the fire and by a greater percentage of trials that put out the fire.

To establish these conditions, various means were used which dealt primarily with varying the ventilation in the shed. At first this was done by cutting various sized holes in the shed wall, some opened directly and some covered with baffles, but since the wind velocity was not constant, reliable data could not be obtained. Ultimately, a blower system was established which allowed a constant amount of air into the room. Two 4 x 4" exhaust portals were cut in the opposite walls.

In order to arrive at a true value it was necessary to run numerous experiments on the fluids and statistically evaluate their ability to put out a fire.

In the testing procedure, the extinguisher was hung from the ceiling directly over the tray. The kerosene and paper towels in the tray were lighted, the doors Closed and the blower turned on. The time at which the plunger was released and broke the bulb could be heard. This usually took about 40 seconds. The condition of the fire on the test shed was determined by the use of four thermo couples placed over the fire and connected to a pyrometer on the outside of the building. The temperature of the fire could then easily be followed and the point at which the temperature suddenly dropped showed when the fire was out. The results of the final practical test showed that carbon tetrachloride extinguished 52 percent of the fires and the inventive compounds extinguished from 72 to percent of the fires.

It is evident from careful studies that rarely is it a single ingredient that puts out a given fire. Usually the action is a combination of synergistic effects provided by the various materials in the fluid. Flame studies have indicated that parts of a given fire have different intensities of flame therein. Each chlorinated or halogenated material reacts in a diflerent manner to each type of flame.

A fire extinguishing compound composed of trichloroethylene, perchloroethylene and either chlorobromo methane or ethylene dibromide was formulated which had a greater maximum allowable concentration, a greater liquid volume, a greater protective volume, a lesser empirical extinguishing number and a greater percentage of extinction in the practical extinguishing tests than carbon tetrachloride. A specific example of such a compound including chlorobromo methane consisted of, by volume, 40 percent perchloroethylene, 40 percent trichloroethylene and 20 percent chlorobromo methane. This example has an empirical extinguishing number of 8.0, a liquid volume of 19.5, a protected volume of 564 cubic feet, and a relatively low cost at present prices. A specific example of such a compound employing ethylene dibromide consisted of, by volume, 41) percent trichloroethylene, 40 percent perchloroethylene and 20 percent ethylene dibromide. This specific ethylene dibromide also cent trichloroethylene, 25

protected volume of example has an empirical extinguishing number of 9.0, a liquid volume of 18.4, a protected volume of 538 cubic feet, and, again, a relatively low cost at present prices. In such a fire extinguishing compound composed of trichloroethylene, perchloroethylene, and either chlorobrorno methane or ethylene dibromide, the percentage by volume of ethylene dibromide or chlorobromo methane should not be less than percent. The percentage by volume of chlorobromo methane or preferably should not exceed 30 percent. The percentages by volume of perchloroethylene and trichloroethylene are preferably substantially equal.

The addition of methylene dichloride to a fire extin'guishing compound composed of trichloroethylene, perchloroethylene and a member of the group consisting of chlorobrorno methane and ethylene dibromide gave a substantially greater toxicity margin over carbon tetrachloride than the compound without methylene dichloride. It should be understood, however, that the toxicity of the inventive fluid without methylene dichloride is far less than carbon tetrachloride itself. A specific example of the inventive fire extinguisher fluid employing methylene dichloride and chlorobrorno methane consists in, by volume, 25 percent trichloroethylene, 25 percent perchloroethylene, 25 percent methylene dichloride and 25 percent chlorobrorno methane. This compound has an empirical extinguishing number of 8.0, a liquid volume of 21.5, a protected volume of 553, and relatively low cost at present prices. A specific example of the inventive fire extinguisher fluid employing ethylene dichloride and ethylene dibromide consists, by volume, of 25 perpercent perchloroethylene, 25 percent methylene dichloride and 25 percent ethylene dibromide. This compound has an empirical extinguishing number of 7, a liquid volume of 21.1, a protected volume of 500 and, again, relatively low cost at present prices. It is feasible to vary the percentages of the components of the fluid somewhat in the fluid containing methylene dichloride. Preferably, the percentage by volume of perchloroethylene, methylene dichloride and trichloroethylene in combination does not exceed 90 percent. Preferably, also, the percentage by volume of value as to the relative eificiency as extinguishing agents. The empirical extinction numbers of the fluids vary from approximately 8 to 50 percent below carbon tetrachloride. This would indicate that it would take 8 to 50 percent more carbon tetrachloride to put out an equivalent fire. Somewhat in line with these figures are the protected volume value relationship for the fluids. The estimated protected volume for was slightly over 40 percent greater than the protected volume of carbon tetrachloride. The protected volume of the fluids containing methylene dichloride was slightly over 30 percent higher than carbon tetrachloride. In the practical tests, carbon tetrachloride extinguished the fires 50 percent of the time whereas the inventive fluids, which differed very little from one another in this characteristic extinguished the fires from 72 to 100 percent of the time.

Thus it is seen that a fire extinguisher fluid has been provided which far surpasses the conventional fire extinguisher fluids, particularly carbon tetrachloride, in use.

From the foregoing it will also be seen that this invention isrone well adapted to attain all of the ends and objects hereinabove set forth together with other chlorobrorno methane or ethylene dibromide does not exceed 30 percent. An example of such a percentage varied compound, again employing methylene dichloride and ethylene dibromide, consists of, by volume, 10 percent ethylene dibromide, 15, percent methylene dichloride, 40 percent perchloroethylene and 35 percent trichloroethylene. This compound has an empirical extinguishing numberv of 11, a liquid volume of 22.6, a i 514, and a relatively low cost at present prices. I

From the liquid volume values for the fire extinguisher fluids, it was established that carbon tetrachloride is six to seven times more toxic than the new formulations. From the practical test data, it was shown that the new fluids are up to 50 percent better asextingu'ishing agents than carbon tetrachloride. The empirical extinction number data also indicates essentially the same advantages which are obvious and which are inherent to the compounds.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A composition adapted for use in extinguishing fires composed of, by volume, perchloroethylene in a ratio of not less than 30% nor greater than 40%, trichloroethylene in a percentage not less than 35 nor greater than 40, and chlorobromomethane in a percentage not less than 20 nor greater than 35.

2. A composition adapted for use in extinguishing fires composed of 40% trichloroethylene by volume, 40% perchloroethylene by volume, and 20% by volume chlorobromomethane.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Industrial Solvents-Mel1an; Reinhold Pub. Co., N.Y., 1939; chapter 9.

fluids without methylene dichloride.

Claims (1)

1. 2. A COMPOSITION ADAPTED FOR USE IN EXTINGUISHING FIRES COMPOSED OF 40% TRICHLOROETHYLENE BY VOLUME, 40% PERCHLOROETHYLENE BY VOLUME, AND 20% BY VOLUME CHLOROBROMOMETHANE.