Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D1/00—Fire-extinguishing compositions; Use of chemical substances in extinguishing fires
  • A62D1/0007—Solid extinguishing substances
  • A62D1/0014—Powders; Granules
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62C—FIRE-FIGHTING
  • A62C13/00—Portable extinguishers which are permanently pressurised or pressurised immediately before use
  • A62C13/003—Extinguishers with spraying and projection of extinguishing agents by pressurised gas

Definitions

• This invention relates to charges for dry chemical fire extinguishers and more particularly to stored pressuretype extinguishers.
• the charge usually consists of an extinguishing agent and an expellant gas and these should be present in an appropriate weight ratio for satisfactory operation. If the extinguisher cavity is filled full with dry chemical powder, for example, addition of the necessary amount of expellant gas will result in a high pressure and consequently, a heavy and expensive shell is needed to contain it.
• the amount of dry chemical can be reduced to allow a greater volume for the expellant gas, thereby reducing its pressure.
• this obviously reduces the amount of extinguishing agent available for discharge from a given size extinguisher. It is also desirable that there be some convenient and reliable method of determining the state of readiness for use of the extinguisher.
• one of the objects of this invention is to provide an extinguisher in which a maximum proportion of the gross weight of the extinguisher consists of the dry chemical extinguishing agent.
• Example 1 An extinguisher shell of 72 cu. in. capacity was filled with 1135 g. standard dry chemical fire-extinguishing powder and pressurized with carbon dioxide. Dry chemical fire-extinguishing powder consists essentiallly of powdered sodium bicarbonate and additives to maintain the powder in dry freeaflowing condition as disclosed in US.
• Patents 1,793,420 and 2,631,977 For proper operation of this extinguisher, 30 to 35 grams of CO are required by fire-extinguisher approval agencies. When 19 grams of CO had been admitted, the pressure was 200 psi, 30 grams of CO raised the pressure to 300 p.s.i. and 35 grams to 350 p.s.i. Thus, a pressure between 300 and 350 psi. would be required, and the extinguisher to withstand these pressures would necessarily be expensive and heavy. When the extinguisher was filled with dry chemical powder modified by the addition of 10 percent silica gel, 20 grams of CO were present at only p.s.i. and by the time the pressure stood at 200 psi, 38 grams had been admitted.
• the effectiveness of the adsorptive agent is further evident when it is realized that the extinguisher with no powder in it at all contained only 33 grams of CO at 200 p.s.i.
• the presence of the adsorptive agent may also enhance the discharge characteristics of the dry chemical powder. In the extinguisher mentioned above 95 percent of the powder was expelled, percent being considered an acceptable value.
• expellant gases suitable for use in the present invention include carbon dioxide, nitrous oxide, ethane, halogenated hydrocarbons, nitrogen, and air, including mixtures of the foregoing.
• Example 2 The extinguisher of Example 1 was filled with a charge comprising 85 percent dry chemical fire-extinguishing powder and 15 percent of an adsorbing agent, silicaalumina micro spheres of the type used as a catalyst in fluid bed petroleum cracking operations having 75 percent silica and 25 percent alumina.
• the extinguisher was pressurized with CO to 200 p.s.i., 38 grams being admitted.
• gases may also be used but some discretion should be exercised to make sure the adsorbing agent will adsorb the chosen expellant.
• Our invention is equally effective when the expellant gas comprises more than one chemical compound.
• Example 4 A two-component expellant gas consisted of approximat-ely equal quantities of dichlorodlfluoromethane and carbon dioxide. In charging the extinguisher, the procedure was to first fill with extinguishing agent, charge the dichlorodifiuoromethane to 38 p.s.i. and then add CO to 190 p.s.i. (all at 70 F.).
• Example 5 The procedure for Example 4 was repeated except that monochlorodifluoromethane was substituted for the halogenated hydrocarbon.
• a powdered dry chemical extinguishing agent composed of 90 percent sodium bicarbonate and percent attapulgus clay and then pressurized to 40 p.s.i. with the monochlorodifluoromethane, and then to 190 p.s.i. with carbon dixiode, 17 grams of monochlorodifluoromethane and 18 grams of CO were admitted making a total of 35 grams of expellant gas. On discharge tests, 94 percent of the dry chemical was effectively expelled.
• Example 6 The test extinguisher was filled with dry chemical composed of 90 percent sodium bicarbonate and 10 percent silica gel and pressurized to 50 p.s.i. with monochlorodifluoromethane and then to 200 p.s.i. with nitrogen. This procedure gave 36 grams of expellant, 27 grams of monochlorodifluoromethane plus 9 grams of nitrogen.
• Example 7 A dry chemical fire-extinguishing powder was prepared which consisted of .10 percent finely divided attapulgus clay and 90 percent finely divided sodium bicarbonate. 1135 grams of this powder were placed in a 72 cu. in. fire extinguisher shell and 1-chlorodifluoro-2-chlorodifluoroethane was admitted to a pressure of 10 p.s.i. and then CO was added to a pressure of 200 p.s.i. This procedure gave a total expellant charge of 32 grams, 7 grams of which were the said halogenated hydrocarbon. On discharge tests, 96 percent of the extinguished agent was expelled from the extinguisher.
• the nature of the expellant gas can vary widely.
• the expellant gas should be non-reactive with the ingredients in the dry chemical fire-extinguisher charge; for example a highly acidic gas could not be used with a sodium bicarbonate based fire-extinguishing agent.
• a combustible gas such as ethane, as an expellant, since the quantity of fuel added to the fire in this manner is infinitesimal when compared to the quantity of fuel already being consumed by the fire.
• the adsorbent may be present in suitable amount depending upon the nature of the adsorbent, the amount of expellant gas to be stored in the charge and the storage pressures desired.
• the proportions of the dry chemical, adsorbent and expellant gas thus may be varied considerably, depending upon the capacity of the extinguisher used and the permissible loss of expellant gas which can be determined by weighing the extinguisher unit.
• the following are illustrative examples of charges suitable for use in a 2 /2 1b. capacity dry chemical extinguisher which can be stored prior to use and that can be weighed within A ounce loss of weight to determine whether any expellant gas has been lost during storage. The parts are given by weight.
• Example 8 Charges :were made for a fire extinguisher containing by weight -90 percent of an alkali metal bicarbonate, 5-15 percent high surface silica magnesia adsorbent, 0.5 to 1.5 percent halogenated hydrocarbon and 1.25 to 1.75 percent expellant gas such as nitrogen or carbon dioxide.
• Example 9 Charges were made for a fire extinguisher having 50 to 98 percent dry chemical fire-extinguishing powder, 2 to 50 percent high surface-area silica gel and 2.5 to 10 percent carbon dioxide.
• Example 10 Charges were made for a fire extinguisher comprising 50 to 98 percent dry chemical fire extinguishing powder, 2 to 35 percent high surface-area silica gel and 2.5 to 10 percent nitrous oxide.
• Example 11 Charges were made for a fire extinguisher comprising 60 to percent dry chemical fire-extinguishing powder, 5 to 35 percent high surface-area silica gel and 2.5 to 10 percent ethane.
• Example 12 Charges were made for a fire extinguisher comprising 60 to 95 percent dry chemical fire-extinguishing powder, 5 to 40 percent attapulugus clay and 2.5 to 10 percent of an expellant gas such as carbon dioxide. Nitrous oxide or ethane may replace the carbon dioxide in this example.
• Example 13 Charges were made for a fire extinguisher comprising 50 to 95 percent dry chemical fire-extinguishing powder, 5 to 40 percent activated carbon and 2.5 to 10 percent carbon dioxide. Synthetic zeolite or activated alumina may replace the activated carbon.
• the particle size of the adsorbent is not critical as long as it is of a size that will not obstruct the discharge orifice or otherwise interfere with the discharge of the extinguisher. Usually particles between 100 and 200 mesh were used, but successful adsorption characteristics were even obtained with A; inch chunks.
• a sealed container having therein a charge, said charge consisting essentially of, by weight, 10 to 50 percent of a high surface area adsorbent selected from the group consisting of silica gel, activated carbon, attapulgus clay, synthetic zeolite, activated alumina, silica-a1umina and silica magnesia, 1.75 to 10% of non-reactive expellant gas, said gas being a member selected from the group consisting of carbon dioxide, nitrous oxide, ethane, halogenated hydrocarbon, nitrogen, air, and mixtures thereof, and, the remainder, a freefiowing comminuted fire extinguishing agent, at least 10 percent of said expellant gas being adsorbed on said adsorbent.
• a high surface area adsorbent selected from the group consisting of silica gel, activated carbon, attapulgus clay, synthetic zeolite, activated alumina, silica-a1umina and silica magnesi
• halogenated hydrocarbons are selected from the group consisting of dichlorodifluoromethane, monochlorodifiuoromethane, and 1-chlorodifiuoro-2-chlorodifiuoroethane.
• a sealed container having therein a charge, said charge consisting essentially of, by weight, 10 to percent of a high surface area adsorbent selected from the group consisting of silica gel, activated carbon, attapulgus clay, synthetic zeolite, activated alumina, silica alumina, and silica magnesia, 2.5 to 10 percent of non-reactive expellant gas, said gas being a member selected from the group consisting of carbon dioxide, nitrous oxide, ethane, halogenated hydrocarbons, nitrogen, air, and mixtures thereof, and, the remainder, a free flowing comminuted fire extinguishing agent, at least 10 percent of said expellant gas being adsorbed on said adsorbent.
• a high surface area adsorbent selected from the group consisting of silica gel, activated carbon, attapulgus clay, synthetic zeolite, activated alumina, silica alumina, and silica magnesia

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• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Public Health (AREA)
• Fire-Extinguishing Compositions (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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Cited By (18)

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Citations (5)

• 1959
  • 1959-02-06 US US791522A patent/US3055435A/en not_active Expired - Lifetime
  • 1959-04-10 GB GB12169/59A patent/GB904560A/en not_active Expired
  • 1959-04-21 BE BE577951A patent/BE577951A/fr unknown

Patent Citations (5)

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