US3055435A

US3055435A - Dry chemical fire extinguishers

Info

Publication number: US3055435A
Application number: US791522A
Authority: US
Inventors: William R Warnock; James A Lindlof; Rodney L Hemminger
Original assignee: Ansul Chemical Co
Current assignee: Ansul Chemical Co
Priority date: 1959-02-06
Filing date: 1959-02-06
Publication date: 1962-09-25
Anticipated expiration: 1979-09-25
Also published as: BE577951A; GB904560A

Description

United States Patent DRY CHEMICAL FIRE EXTINGUISHERS William R. Warnock and James A. Lindlof, Menominee,

M1ch., and Rodney L. Hemminger, Marinette, Wis,

assignors to Ansul Chemical Company, Marinette, Wis., a corporation of Wisconsin N Drawing. Filed Feb. 6, 1959, Ser. No. 791,522

4 Claims. (Cl. 169-31) This invention relates to charges for dry chemical fire extinguishers and more particularly to stored pressuretype extinguishers.

In stored pressure 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.

If it is desired to use a lighter weight and less expensive shell, the amount of dry chemical can be reduced to allow a greater volume for the expellant gas, thereby reducing its pressure. However, 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.

Extinguishers currently available will usually discharge satisfactorily if they are handled properly. Frequently a pressure gauge is relied upon to indicate the presence of sutlicient gas for effective discharge of the extinguishing agent. Gauges have been known to give inaccurate readings by virtue of damage to the mechanism, plugging, etc. However, if the quantity of expellant gas is large in proportion to the gross weight of the extinguisher, readiness for use can be ascertained by determining the weight of the extinguisher.

Therefore, 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.

It is also an object of this invention to provide a dry chemical fire extinguisher which will, without excessive pressures or reduction in the amount of dry chemical powder, contain such a large amount of expellant gas that a weighable amount of said gas can escape or leak from the extinguisher without impairment of the fire fighting capabilities of the extinguisher.

It is another object of this invention to provide an extinguisher whose suitability for use can be reliably 5 ascertained by determining its weight within reasonable limits.

=We have found that these objects can be accomplished by the addition of a highly adsorptive material to the dry chemical extinguishing agent. This adsorptive material should have a high surface area per unit of volume which enables small amounts of it to adsorb enough of the expellant gas so that when the extinguisher is fully charged, the pressure will be considerably below that usually expected; or stated another way, a large quantity of gas can be charged without exceeding a preselected pressure, all

pressures referred to being gauge pressure measured at 70 F. The invention is illustrated by the following examples.

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.

Because of ICC regulations, inspection codes, and so forth, it is desirable to limit the pressure at 70 F. to 200 p.s.i. The presence of the adsorptive agent enables maximum amounts of .both extinguishing agent and expellant gas to be charged to the extinguisher without exceeding this limit.

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.

Other adsorbing agents are also suitable. In general, they should have a high surface area as determined by nitrogen adsorption or some equivalent method. It is preferred that the particle size of the adsorbing agent should be of the same order of magnitude as the dry chemical agent, but wide variations are Permissible in this respect. Examples of other suitable adsorbents are activated charcoal, attapulgus clay, synthetic zeolites (molecular sieves), activated alumina, cracking catalysts of the type used in petroleum refining containing silica and various proportions of alumina. We may also use the porous materials disclosed in Patent 2,866,760.

The 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.

We have found that for best results the adsorbent should be as free as possible of adsorbed water before addition to the dry chemical powder and should be protected from the atmosphere until charged to the extinguisher. In general, heating the adsorbent to 300400 F. for a few hours accomplished adequate drying. It is preferred that the adsorbent be mixed with the dry chemical powder but this is not essential for the successful practice of this invention. Materials which do not have a high surface area are not satisfactory as adsorbents. For example, very small glass beads or talc cannot be used.

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.

Other gases may also be used but some discretion should be exercised to make sure the adsorbing agent will adsorb the chosen expellant.

Example 3 The fire extinguisher of Example 1 was filled with a charge comprising percent standard dry chemical fireextinguishing agent and 10 percent silica gel having a fine particle size. Nitrous oxide was charged to 200 p.s.i., 37

3 grams being required. When the extinguisher was discharged, less than 10 percent of the solids remained in the extinguisher.

When this empty extinguisher was filled to 200 p.s.i. with nitrous oxide, 31 grams were required. When it was filled with standard fire-extinguishing powder containing no adsorptive agent, only 19 grams of nitrous oxide could be admitted at 200 p.s.i.

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.).

When the extinguisher was charged with gas as above and no dry chemical powder, it held about 39 gram of expellant gas, but when filled first with sodium bicarbonate powder, the gas weight was reduced to only 23 grams, much less than the desired 30-35 grams, although charging pressures were the same.

When the extinguisher =was filled with a dry chemical extinguishing agent composed of 90 percent NaHCO and 10 percent attapulgus clay, we were able to introduce 39 grams of expellant gas On fire tests with the latter dry chemical, composition, well over 85 percent of the dry chemical was effectively discharged.

Example 5 The procedure for Example 4 was repeated except that monochlorodifluoromethane was substituted for the halogenated hydrocarbon. When the extinguisher was filled with 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.

As indicated in the above examples, the nature of the expellant gas can vary widely. However, 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. It is possible to use 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.

'Ihe extinguishers in the above examples will discharge satisfactorily so long as the pressure of the expelling gas at the start of the discharge is above -140 p.s.i. We have found that a loss of 20 percent (about seven grams) of the expellant can be detected by weighing the extinguisher on an ordinary scale or balance. We have further found that after the loss of 20 percent of the expellant, the pressure remaining in the extinguisher is still sufficient to provide satisfactory discharge characteristics.

For a 2 /2 lb. extinguisher capacity, we have found charges are satisfactory containing by weight about 50 to about 98 percent dry chemical fire-extinguishing powder, about 2 to about 50 percent of a high surface-area adsorbent, and from about 2.5 percent to about 10 percent of expellant gas. The operations of these components obviously can be greatly varied depending upon the capacity of extinguisher in which the charge is stored, the proportions being predetermined so that the total amount of the gaseous expellant in the container is capable of expelling substantially most of the dry chemical stored in the container and at the same time the stored charge is weighable in the extinguisher so that a weighable amount of the expellant gas, for example, A ounce loss of weight, can permissibly escape or leak from the extinguisher without impairment of the fire extinguishing usefulness of the extinguisher. Thus, by the use of a suitable adsorptive agent which can adsorb at least percent by weight of the expellant gas in association with the dry chemical in our charge we can, while not raising the maximum pressure above 200 p.s.i. at 70 F., add such a large weight of expellant gas that the loss of an easily weighable quantity still leaves the extinguisher in a state of readiness for use and this is accomplished while maintaining the dry chemical charge at the maximum amount which can be poured into the extinguisher cavity We claim:

1. In a fire extinguisher, 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.

2. In a fire extinguisher, a sealed container having therein the charge of claim 1 wherein said halogenated hydrocarbons are selected from the group consisting of dichlorodifluoromethane, monochlorodifiuoromethane, and 1-chlorodifiuoro-2-chlorodifiuoroethane.

3. The fire extinguisher of claim 1, wherein the pressure in said sealed container is below about 200 p.s.i. at 70 F.

4. In a fire extinguisher, 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.

References Cited in the file of this patent UNITED STATES PATENTS 2,605,848 Carter Aug. 5, 1952 2,785,838 Mayer Mar. 19, 1957 2,819,763 Boal Jan. 14, 1958 2,881,138 Reiss Apr. 7, 1959 2,901,427 Steppe Aug. 25, 1959 UNITED STATES PATENT OFFICE Patent No. 3,055,435

September 25, 1962 William R. Warnock et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 41, for "attapulugus" read attapulgus column 4, line 71, for "operations" read proportions Signed and sealed this 19th day of March 1963.,

(SEAL) Attest:

ESTON G. JOHNSON Attesting Officer DAVID L. LADD Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,055,435 September 25, 1962 William R. Warnock et a1.

I Column 4 line 41, for "attapulugus" read attapulgus column 4 line 71, for "operations" read proportions Signed and sealed this 19th day of March 1963.,

(SEAL) Attest:

ESTON G, JOHNSON DAVID L. LADD Attesting Officer a 7 Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3,055,435 September 25, 1962 William R. Warnock et a1.

Column 4, line 41, for "attapulugus" read attapulgus column 4 line 71 for "operations" read proportions Signed and sealed this 19th day of March 1963..

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD t sting Officer Commissioner of Patents

Claims

1. IN A FIRE EXTINGUISHER, A SEALED CONTAINER HAVING THEREIN A CHANGE, SAID CHARGE CONSISTING ESSENTIALLY OF, BY WEIGHT, 10 TO 50 PERCENT OF A HIGH SURFACE AREA ADSORBENT SELECTED FROM THE GROUP CONSITING OF SILICA GEL, ACTIVATED CARBON, ATTAPULGUS CLAY, SYNTHETIC ZOELITE, ACTIVATED ALUMINA, SILICA-ALUMINA 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 FREEFLOWING COMMINUTED FIRE EXTINGUISHING AGENT, AT LEAST 10 PERCENT OF SAID EXPELLANT GAS BEING ADSORBED ON SAID ADSORBENT.