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
  • A62D1/0071—Foams
• • 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

Definitions

• the present invention relates to compositions based on alkali metal bicarbonates, used in fire extinguishers of the dry powder type.
• Refined sodium bicarbonate in the state of very fine particles, is very suitable for filling extinguishing apparatus using powder. It has been known for a long time to improve its suitability for projection by coating it with a metallic salt of a long chain fatty acid.
• alkali metal bicarbonate powders of certain inert fillers in the finely divided state has permitted the improvement of their mobility to a degree varying with the characteristics of the filler.
• the fillers used there may be mentioned talc, calcium and magnesium carbonates, silica, certain silicates, fly-ash, etc.
• the best method of putting out a hydrocarbon fire consists in combining the advantages of powder and foam extinguishers, in putting out the fire by means of an extinguishing powder, then covering the zone where the fire extinguishing has been effected, with a layer of protective foam.
• the present invention provides extinguishing powder compositions compatible with the foams and presenting at the same time a very good suitability for projection.
• compositions according to the invention comprise -98% of a finely divided alkali metal bicarbonate, advantageously sodium bicarbonate, potassium bicarbonate or mixtures thereof, 1-l9% of talc and l8% of very fine grain silica.
• Talc and silica used as additive must have a particle size as fine as possible.
• the silica it is essential that it shall be made up of extremely fine grains, much more fine than the bicarbonate particles.
• the average size of the silica particles should be advantageously less than 1 micron, and preferably equal to a few hundredths of a micron at the most.
• the properties of the powders according to the invention are particularly unexpected in view of the fact that each of the two additives, talc and very fine grain silica, employed alone, confer on extinguishing powders based on alkali metal bicarbonates, only mediocre properties.
• such powders offer a capacity for projection at least equal to and often superior to the best coated powders.
• the powders corresponding to compositions according to the inevntion are perfectly compatible with extinguishing foams.
• the latter can subsist at high temperature in the presence of the powders for a long time, practically as long as in the absence of the powder.
• the bicarbonate usable in these compositions is an uncoated powder, composed of particles of a size as small as possible.
• a bicarbonate having an average particle size in the neighbourhood of ten microns is particularly suitable for carrying out the invention.
• finely divided sodium bicarbonate is coated with at most 0.5% silicone oil, preferably 0.050.2%, calculated on the weight of bicarbonate to be coated.
• This coating can be carried out advantageously according to the process of projection and whirling, in a mixer consisting of a horizontal drum in which an axial shaft, carrying paddles in the form of plough shears, rotates at the rate of 300 revolutions per minute.
• Talc and very fine grain silica are then added to the coated powder, for the purpose of conferring thereon the properties of mobility and compatibility.
• a powder of this type may have the following composition:
• potassium bicarbonate offers extinguishing properties similar to those of sodium bicarbonate, all or part of the sodium bicarbonate may be replaced, if desired, by potassium bicarbonate.
• a particularly well suited mixer consists of a horizontal drum in which an axial shaft carrying large paddles rotates at the rate of 300 revolutions per minute.
• the invention is in no way limited to the compositions given by way of example.
• the capacity for projection of the extinguishing powders was tested in an apparatus for projecting powders, especially designed for the evaluation of the mobility and the aptitude for projection of extinguishing powders and which is a reduced model of the commercial apparatus.
• the degree of compatibility of the extinguishing powders with the foams is given by the measure of time required for the liquefaction, at elevated temperature, of a determined volume of foam recovered from a given quantity of the powder to be examined.
• a powder is considered compatible when the time necessary for liquefying the foam in the presence of the powder, is greater than half the time measured for the foam alone.
• Extinguishing powder compatible with fire extinguishing foams consisting of -98% of an alkali metal bicarbonate having an average particle size of the order of 10 microns selected from the group which consists of potassium bicarbonate, sodium bicarbonate and mixtures thereof, 119% talc having an average particle size of less than 1 micron, and 18% silica having an average particle size less than 1 micron, of the order of 0.05 micron.
• Extinguishing powder compatible with fire extinguishing foams consisting of 80-98% of sodium bicarbonate having an average particle size of the order of 10 microns, 119% of talc having an average particle size of less than 1 micron and 18% of silica having an average particle size of less than 1 micron and of the order of 0.05 micron.
• Extinguishing powder compatible with fire extinguishing foams consisting of 80-98% of an alkali metal bicarbonate having an average particle size of the order of 10 microns selected from the group which consists of sodium bicarbonate, potassium bicarbonate, and mixtable permit to 5 6 ture thereof, 149% of talc, and 18% of very fine grain References Cited by the Examiner silica, having an average particle size of less than 1 micron.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Detergent Compositions (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (8)

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Citations (3)

• 0
  • NL NL129165D patent/NL129165C/xx active
  • NL NL292142D patent/NL292142A/xx unknown
• 1963
  • 1963-04-18 CH CH484763A patent/CH410644A/fr unknown
  • 1963-05-03 FR FR933569A patent/FR1361606A/fr not_active Expired
  • 1963-05-07 FI FI0941/63A patent/FI42273B/fi active
  • 1963-05-07 US US278742A patent/US3267030A/en not_active Expired - Lifetime
  • 1963-05-08 DK DK218063AA patent/DK114598B/da unknown

Patent Citations (3)

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