US3434336A - Explosion barrier - Google Patents

Description

March 25, 1969 G. B. HARR EXPLOSION BARRIER Filed Aug. 11, 1965 FIG! United States Patent 3,434,336 EXPLOSION BARRIER George B. Harr, Pasadena, Calif., assiguor to The Firestone Tire & Rubber Company, Akron, Ohio, 21 corporation of Ohio Filed Aug. 11, 1965, Ser. No. 478,945 Int. Cl. G01u 25/20, 33/22 US. Cl. 73-35 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a test apparatus used to test the use of plastic foams as explosion barriers, and its operation. The apparatus and its operation simulate commercial installations and processes, and commercial apparatus and its use are included in the claims appended hereto.

It has been found that plastic foams serve as a barrier to the propagation of explosions in explosive gaseous mixtures and, according to this invention, can be used to confine such explosions and to prevent the propagation of such explosions through explosive gaseous mixtures. (The term explosive gaseous mixtures is used herein to refer to any explosive composition in the gaseous or vapor phase, the precursor of which may be a solid, a liquid or a gas.) Thus, in oil-distilling plants, in chambers in which explosive gaseous mixtures from lacquer drying operations are collected, in the handling of explosive gaseous vapors, in internal-combustion engine systems, etc., plastic foams are valuable barriers to confine explosive gaseous mixtures and limit the propagation of explosions.

The foam must be open-celled. Polyurethane foams have been very satisfactory, but the invention is not limited thereto, as foam rubbers, foams of rubber derivatives, even cellulosic foams, and foams of other plastic compositions, whether flexible or rigid, can be used. The foams may be treated with flame retardants as required. The depth of the foam necessary to bar the passage of an explosive wave depends upon the explosive force which, in turn, is dependent upon the volume of the explosive mixture, the area of the foam surface exposed to the explosion, the shape of the space in which the explosion occurs, the composition of the explosive mixture, etc.

In the test apparatus, hot wires are used to set off an explosion, but other means may be employed, and in the comparable equimpment in a commercial installation or the like, means for igniting an explosive mixture will ordinarily not be used but the foam barriers will be used where an explosion may be ignited unintentionally, as by lightning, a spark from impact, spontaneous combustion, static, etc.

The invention is further illustrated by the accompanying drawings which in a more or less diagrammatic manner illustrate different uses of the foam. In the drawings- FIGURE 1 is an elevation, largely in section, of equip- 3,434,336 Patented Mar. 25, 1969 ment in which two foam barriers are employed to confine an explosive gaseous mixture; and

FIGURE 2 is an elevation, also largely in section, showing the use of one foam barrier to prevent the propagation of an explosion in one direction only.

In FIGURE 1, the test chamber 5 is connected by a pipe 6 with a cylinder 7 of the same volume as the chamber 5. The cylinder is equipped with a plunger 8 which may be reciprocated manually or mechanically. The volume of chamber 5 and cylinder 7 is determined. Valve 10 is opened, valve 12 is closed and a programmed amount of volatile, inflammable liquid, suflicient to produce a desired explosion in the chamber 5, is introduced through pipe 13 into cavity 15 within cylinder 7, with the piston in the inserted position. The piston is then retracted, sucking air in through valve 10, producing an explosive gaseous mixture.

Valve 10 is now closed and valve 12 is opened. The piston is then pushed in, transferring the explosive mixture through tube 6 to chamber 5. The chamber 5 is divided into three compartments by the open-cell, polyurethane foam barriers 17 and 18 which form the compartment 20 and which, with the end enclosures 22 and 23 form the compartments 25 and 26. In each end closure is a small port 28. The barriers 17 and 18 are open-celled and permit the passage of gasses therethrough. When the plunger is pushed in, air within the chamber 5 is forced out through the ports 28 in the end closures 22 and 23. The piston cycle is repeated several times with introduction of additional precursor and air, and transfer of the resulting explosive mixture to the chamber 5 until all unwanted air has been displaced from this chamber. Although particular reference has been made to the use of an inflammable liquid (which might be a petroleum distillate, hexane, benzene, etc.), a gas such as methane, etc., or a solid such as finely divided coal, etc. may be used.

For experimental purposes the chamber 5 was made of transparent acrylate (Plexiglas) so that the movement of the flame produced by each explosion could be watched. It was found that the flame entered but did not pass through a flame barrier. In a commercial installation this cylinder will be replaced by a chamber of any required shape with walls of any required composition. It may be a conduit for transfer of an explosive mixture.

FIGURE 1 illustrates the confinement of an explosive gaseous mixture in the compartment 20 between the blocks of polyurethane foam 17 and 18. To illustrate the invention, we refer to the chamber 5 as being 3 inches in diameter and 2 feet long, and each of the blocks 17 and 18 as being one inch thick. The chamber 20 is about 1 inch long, and may be enlarged and the blocks 17 and 18 may be made correspondingly thicker to resist the greater explosive force from a larger volume of the explosive mixture. The blocks 17 and 18 need not be fastened to the wall of the chamber. These blocks are each composed of open-cell polyurethane foam, with 10 to 20 or more up to 50 or more pores per inch.

To complete the description of FIGURE 1, the end pieces 22 and 23 in the experimental unit may be impervious discs which are lightly held in place by friction. They serve as blow-out discs. The wires 30, 31 and 32 are heated by current supplied through the connections shown.

To demonstrate the barrier effect of foam, the explosive mixture in the various compartments may be exploded individually or in any sequence. For example, the mixtures in compartments 20, 25 and 26 may be exploded in that order, demonstrating that an explosive mixture indeed exists in each of the chambers and that the initial explosion in chamber 20 is effectively isolated by foam barriers 17 and 18. The explosions in chambers 25 and 26 usually blow out the discs 22 and 23.

Referring now to FIGURE 2, for this experiment chamber 5 is divided into two compartments by the foam barrier 40, compartment 41 being much larger than compartment 42. The chamber 5 is filled with an explosive gaseous mixture in the manner described. The mixture in chamber 41 is ignited by either of the wires 30 or 31, creating a sizable explosion. Wire 32 is then heated causing an explosion in compartment 42, demonstrating that an explosive mixture has been present in this compartment and that barrier 40 has prevented the sizable explosion in compartment 41 from being propagated through the barrier. Blow-out discs 22 and 23 are ejected during these demonstrations.

Further demonstrations have included attempts to initiate explosions directly within foam blocks by placing the blocks in contact with one another at the entrance of the pipe 6 into the chamber 5, encapsulating the wire 31 between them. In this case explosions did not occur in the foam.

The foregoing demonstrate clearly that the explosive gases can be passed through the foam barriers, but even with the barriers saturated with the explosive mixture, they prevent the explosion of the gaseous mixture entrained therein, as well as demonstrating that the propagation of an explosion of a gaseous mixture can be barred by a foam barrier. The mixture before explosion may be at atmospheric pressure or under a higher pressure, and its temperature is unimportant.

Thus it is seen that open-cell foam may be used as a wall to confine an explosive mixture and, as illustrated in FIGURE 1, opposed walls may be used as in a conduit or other passage or chamber through which an explosion is passing, or for confinement of a stationary explosive gaseous mixture. The cells are of an open structure and do not prevent the gaseous mixture from traveling through them. If the gaseous mixture is accidentally exploded, as by lightning or from any other unexpected cause, the confined mixture may explode, but a foam barrier prevents propagation of the explosion into the explosive gaseous mixture located on the other side of the barrier.

What I claim is:

1. Test apparatus with means for introducing an explosive gaseous fuel thereto, which apparatus includes a cavity and a plastic, open-cell foam which divides the cavity, and electrical igniting means in each division of the cavity.

2. A test chamber with means for introducing an explosive gaseous fuel thereto, an intermediate portion of which chamber is divided from each of two end portions by two plastic, open-cell foam partitions, electrical igniting means in each portion of the chamber and a safety blow-out in the wall of each of said end portions.

3. The chamber of claim 2 in which the largest dimension of either of the partitions is relatively small compared with the distance between them.

4. Test apparatus with means for introducing an explosive gaseous fuel thereto, which apparatus includes two chambers separated by a partition of plastic, open-cell foam, electrical igniting means in each chamber and a safety blow-out in the wall of each chamber.

5. An elongated chamber with means for introducing an explosive gaseous fuel to one portion thereof which portion is separated from each of the two adjacent portions by a plastic, open-cell foam, electrical ignition means in each of said portions and a safety blow-out in the wall of each of said portions.

6. An elongated chamber with means for introducing an explosive gaseous fuel thereto, with a plastic, opencell foam between said means and the end of the chamber, electrical ignition means for exploding the fuel on each side of the foam and a safety blow-out in the wall on each side of the foam.

7. A chamber with means for introducing an explosive gaseous fuel thereto, which chamber includes a safety blow-out, spaced therefrom a partition of a plastic, opencell foam, and electrical ignition means in the chamber.

8. Test apparatus with means for introducing an explosive gaseous fuel thereto, which apparatus includes a cavity with opposed walls of a plastic, open-cell foam separated by a rigid wall structure, and a safety blow-out in said rigid wall.

9. A fuel system which includes a cavity divided into two parts by a plastic, open-cell foam, with a conduit connected into each of said parts for the introduction of a fuel gas into and away from the cavity, and a safety blow-out in the wall of the cavity.

10. A system which includes means for generating an explosive gaseous mixture, a chamber with a wall of plastic, open-cell foam therein which divides the space within the chamber into at least two parts, and a safety blow-out in at least one part, and a connection for the passage of gas from said means to the chamber.

11. A system which includes a conduit for the passage of an explosive gaseous mixture from one chamber to another chamber, a safety blow-out in each chamber and at least one plastic, open-cell foam barrier in the conduit.

12. A system which includes a cavity adapted for containing an explosive gaseous mixture, a safety blowout in the cavity and a plastic, open-cell foam barrier dividing the cavity.

13. A system which includes a cavity adapted for containing an explosive gaseous mixture and spaced plastic open-cell foam barriers dividing the cavity, with a conduit connected with the cavity for the introduction of the gaseous mixture thereto and another conduit for the removal of the gaseous mixture therefrom.

References Cited UNITED STATES PATENTS 1,731,406 10/1929 Bernard.

2,766,837 10/1956 McCollum.

2,770,241 11/1956 Winkler.

3,048,537 8/1962 Pall et a1 222 189 XR 3,189,223 6/1965 Mackal 222-189 XR 3,268,107 8/1966 Sperling 73-35 XR 3,285,296 11/1966 Ishimaru 61; al. 222 189 XR 3,293,174 12/1966 Robjohns 210 510 XR 3,322,294 5/1967 Nemeth 220-88 XR JAMES J. GILL, Primary Examiner.

US. Cl. X.R. 22088

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