Explosion suppression system

Abstract: An explosion protection system includes a container 12,13 having a primary storage volume 16 for an explosion suppressant 17 retained under pressure, and defining a discharge outlet 27. An auxiliary storage volume 22 is disposed between the discharge outlet 27 and the primary storage volume 16 and provides communication between. A closure member 28 covers the discharge outlet 27, an explosive charge being disposed in the container adjacent the closure member 28 and adapted to create explosive forces that rupture the closure member 28. An explosive force transmitting agent filling the auxiliary storage volume 22 has a degree of compressibility less than that of the explosion suppressant 17.

Description: This invention relates generally to an explosion suppression or protection system and, more particularly, to an explosion suppression system as set out in WO-A-8 803 824 in which a dry powder suppressant is discharged in response to detection of an explosive condition. High rate discharge (HRD) extinguishing systems are extensively used to suppress potentially destructive dust and vapor explosions occurring in inherently hazardous process and applications. A typical HRD suppression system is disclosed in U.S. Patent No. 2,766,832. Most commonly employed in HRD systems were halogenated liquid suppressants which are currently being replaced by environmentally friendly dry powder suppressants such as sodium bicarbonate and mono-ammonium phosphate. It has been found, however, that when dry powder suppressants are used in conventional HRD containers, the reliability of suppressant discharge is reduced. The reduced reliability result from an increased difficulty in rupturing with explosive charges the closure members typically used on the HRD containers. Since the dry powder suppressant is pressurized with a compressible gas such as nitrogen, the gas tends to absorb the shock wave created by firing of the explosive initiator to thereby attenuate the strength of the shock wave transmitted to the frangible closure member. An object of this invention, therefore, is to provide an improved HRD explosion suppression system employing a dry powder suppressant. The invention consists in an explosion protection system comprising a container for containing an explosion suppressant under pressure and having a discharge outlet; a closure member covering said discharge outlet; and an explosive charge disposed in said container adjacent to said closure member for producing an explosive force that ruptures said closure member, characterised by a primary storage volume in the container, and an auxiliary storage volume disposed between said discharge outlet and said primary storage volume and communicating therewith; a dispersible explosion suppressant retained under pressure in said primary storage volume and having a given degree of compressibility; and an explosive force transmitting agent filling said auxiliary storage volume and having a degree of compressibility less than said given degree, said agent being adapted to transmit said explosive force to said closure member. Hence, by transmitting the explosive force produced by the explosive charge to the closure member, the agent ensures rupturing of the latter. According to certain features of the invention, the explosive charge is immersed in the agent, and the agent isolates the suppressant from the discharge outlet. This arrangement ensures transmission by the agent of the explosive force. According to other features of the invention, the suppressant comprises a particulate matter and compressible gas mixture, and the agent comprises a substantially non-compressible gel substance. These materials improve the reliability of the suppression system. According to another feature of the invention, the auxiliary storage volume is substantially smaller than the primary storage volume. Thisfeature enhances the efficiency of the suppressor system. According to yet another feature of the invention, the system includes a removable cartridge retaining the agent. The cartridge facilitates placement of the agent within the auxiliary volume. According to still other features of the invention, the container has a discharge channel forming the auxiliary storage volume; and the cartridge comprises side walls conforming substantially to the channel, a first easily ruptured end wall separating the primary volume from the auxiliary volume, and a second easily ruptured end wall conforming substantially to the closure member. These features enhance the performance of the force transmitting agent. In order that the invention may be more readily understood, reference will now be made by way of example, to the accompanying drawings, in which: Fig. 1 is a perspective view of an HRD suppression system according to the invention; and Fig. 2 is a partially cut away and sectioned view of the suppression system shown in Fig. 1. An explosion suppression system 11 according to the invention is illustrated in Figs. 1 and 2. The extinguishing system 11 includes a spherical container 12 supported on a base 13 having a bottom adapted for mounting in an explosive environment. Fixed to an upper end of the spherical container 12 is a ring 15 for use in transporting and positioning of the extinguisher 11. The spherical container 12 defines a primary volume 16 that is filled with a mixture 17 consisting preferably of a dry powder suppressant such as sodium bicarbonate or mono-ammonium phosphate and a non-flammable, non-oxidizing pressurizing gas such as nitrogen. Formed in the extinguisher base 13 is a discharge channel 21 projecting downwardly from an opening in the bottom of the spherical container 12. The discharge channel 21 defines a cylindrical, auxiliary volume 22 that communicates with the primary volume 16 within the spherical container 12. Retained within the auxiliary volume 22 is a cylindrical cartridge 23 having sidewalls that conform to the inner walls of the discharge channel 21. The cartridge 23 and therefore the auxiliary volume 22 are filled with a substantially non-compressible gel 24, for example, petroleum jelly exhibiting a degree of compressibility substantially less than a given degree of compressibility exhibited by the suppressant mixture 17. An easily ruptured top wall 25 of the cartridge 23 isolates the gel 24 from the suppressant mixture 17 in the spherical container 12. Covering a discharge outlet 27 formed at an outer end of the discharge channel 21 is a frangible disc member 28 conforming to an easily ruptured bottom wall 30 of the cartridge 23. An outer periphery of the frangible disc 28 is retained between a pair of annular flanges 31, 32 by bolts 33. Extending into the discharge channel 21 through an opening 35 in the cartridge 23 is a cylindrical initiator well 36. A threaded coupling 37 provides a hermetical seal between the initiator well 36 and the base 13. Retained by the initiator well 36 is an explosive initiator charge (not shown) connected to a pair of initiator leads 39. The explosive charge retained in initiator well 36 is conventional and well known in the prior art. Prior to use, the primary volume 16 defined by the spherical container 12 is filled through the discharge channel 21 with a dry powder suppressant. The gel filled cartridge 23 then is inserted into the discharge channel 21 and the discharge outlet 27 sealed by the frangible disc 28. After insertion of the initiator well 36, the primary volume 16 within the spherical container 12 is charged through a fill port (not shown) with nitrogen to a predetermined pressure of, for example, 345 x 10⁴Pa.N.m² (500 PSIG). In response to detection of an incipient explosion by a conventional detection system, (not shown) electrical current is conducted by the initiator leads 39 to the explosive charge in the initiator well 36. The shock wave produced by a resultant explosion is readily transmitted by the incompressible gel to the frangible disc 28 causing rupture thereof and opening of the discharge outlet 27. The pressurized suppressant mixture 17 therefore is rapidly expelled from the primary volume 16, through the discharge channel 21 and out of the opened discharged outlet 27 into the explosion protected region. Whilst a particular embodiment has been described, it will be understood that modifications can be made without departing from the scope of the present invention, as defined by the appended claims. For example, shock wave force transmitting agents 24 and suppressant mixtures 17 other than those specifically described can be advantageously employed with the disclosed suppressor system 11.

Claims: An explosion protection system comprising: a container (12,13) for containing an explosion suppressant (17) under pressure and having a discharge outlet (27); a closure member (28) covering said discharge outlet; and an explosive charge disposed in said container (12,13) adjacent to said closure member (28) for producing an explosive force that ruptures said closure member characterised by a primary storage volume (16) in the container, and an auxiliary storage volume (22) disposed between said discharge outlet (27) and said primary storage volume (16) and communicating therewith; a dispersible explosion suppressant (17) retained under pressure in said primary storage volume (16) and having a given degree of compressibility; and an explosive force transmitting agent (24) filling said auxiliary storage volume (22) and having a degree of compressibility less than said given degree, said agent being adapted to transmit said explosive force to said closure member (28). A system according to claim 1 wherein said explosive charge is immersed in said agent (24). A system according to claim 1 or 2 wherein said agent isolates said suppressant (17) from said discharge outlet (27). A system according to claim 1,2 or 3 wherein said suppressant (17) comprises a particulate matter and compressible gas mixture. A system according to any preceding claim wherein said agent comprises a substantially non-compressible substance. A system according to claim 5 wherein said substance comprises a gel. A system according to claim 6 wherein said gel comprises a petroleum jelly.

Inventors: GILLIS JOSEPH P, JACOBS JORDAN N, GILLIS, JOSEPH P., JACOBS, JORDAN N.
Applicants: FENWAL SAFETY SYSTEMS INC, FENWAL SAFETY SYSTEMS, INC.
Application year: 1991
Main classification: A62C35
IPC codes: A62C35, A62C37