FIRE PROTECTIVE POWDER PUFF OUT PANEL

Abstract: A fire protective panel comprising: a flexible resilient plastics three dimensionally reticu­ lated structure (10), a flexible plastics film envelope (11) closely and im­ permeably encasing the structure, and a fire extinguishant powder (12) substantially filling the envelope and structure interstices, the structure being compressed within the envelope whereby upon rupture of the envelope the structure expands and imparts a dispersive momentum to at least some of the powder.

Description: FIRE PROTECTIVE POWDER eu"F OUT PANEL The present invention relates to means for resisting, preventing, damping or quelling, or resisting or preventing the spread, of fire. Such means are hereinafter called fire protection means. The invention is particularly concerned with fire protection in certain bays adjacent fuel tanks or tanks of other flammable substances found in vehicles and craft, especially aircraft. If a bay is penetrated by a projectile, even if not incendiary or if the tank is ruptured in an accident, fuel may leak into the bay and ignite. UK Patent Specification 1454493 describes fire protection means and provides adjacent a flammable substance or a container therefore fire protection means comprising an encased and sealed reticulated structure containing an extinguishant. The present invention provides an improvement in one form of these fire protection means which has been discovered to be particularly effective and advantageous. According to the present invention a fire protection panel comprises: a flexible resilient plastics three dimensionally reticulated structure, a flexible plastics film envelope closely and impermeably encasing the structure, and a fire extinguishant powder substantially filling the envelope and structure interstices, and characterised in that the structure is compressed within the envelope, whereby upon rupture of the envelope the structure expands and imparts-a dispersive momentum to at least some of the powder. Compression of the structure may be obtained by quilting the panel at discreet locations, by outgassing (evacuating) the contents of the envelope prior to sealing, or a combination of both, inter alia. In addition to attenuating the moisture content of the envelope and compressing the structure, outgassing may be employed to preform the panel to fit, for example, around a pipe or duct. It also has the effect of compensating for the expansion of the panel, at lov pressures or elevated temperatures, such as might be met in an aircraft. SuitÅable reticulated structures include open pored polyurethane polyether and polyester foams, with the cefl walls not necessarily fully blown, so that there is enhanced resistance to powder compaction, and so-called melded fibre structures formed by adhering carded masses of polyester or polyamide fibres at contact points thereof. Such welded fibres are manufactured and sold by ICI Fibres Ltd under the trade names Atomel and Promel. Preferably the structure has 70-100 pores per linear inch in the uncompressed state. Suitable extinguishant powders include potassium cryolite, potassium and sodium bicarbonates, aluminium phosphates, potassium bicarbonates with urrea reaction products, potassium dawsonite with potassium iodide and aluminium oxide. The latter is particularly attractive since the powder is non-corrosive and has been shown to be an effective extinguishant when used to suppress explosive fire development. Dispersion of the powder is assisted if it is in finely ground form, eg calcined alumina, with a particle size of 1-3 microns, and fluidised with 1-2$ by volume micronised hydropbilic silica as a dispersion and drying agent. Candidate envelope films include polyvinylidene chloride, polyethersulphone and polyester. Any of the plastics membranes 'Saran' (TM) and 'Saranex' (TM) sold by Dow Chemical Ltd, 'Melinex' (TM) sold by ICI and 'Mylar' sold by Dupont may be suitable. Preferably the film is transparent so that the contents of the panel can be inspected, eg for a colour change indicating moisture content and for an unacceptable degree of powder compaction. The membrane need not for most applications, be attached to the reticulated structure. Where the panel is intended for attachment to a structure the designated outer skin may be more frangible or readily openable than the inner, as is described in UK Patent Specification 1603085 for example. It will be appreciated that, the powders indicated above being highly effective, and the powder, the structure and the envelope being of minimal density, very efficient, self generating fire protection of a dry bay can be obtained for an extremely small weight penalty. The panel may be under 3 cm thick, in an aircraft bay context typically 3-10 mm, and arranged to be coextensive with at least one bay wall. The panel may be quilted or compartmentalised, especially if somewhat extensive, as an insurance against powder migration. Panels which are flexible and comprise discreet compartments 7-15 cm square are indeed particularly useful, since they can be cut to size along the seams and particularly readily attached as a retrofit, with adhesive or touch-and-close fastening means, to the wall of a typical aircraft bay adjacent a fuel tank. Considerable fire protection is then available even if only one compartment is opened, and the panel thereby provides a degree of multi-shot protection. If an adhesive patch is used it can be arranged preferably to tear the compartment open in shock conditions but to be removable from whatever the panel is attached to, without opening the panel, by peeling or solvent action. Panels may thus be made flexible and carry discreet adhesive patches with removable covers, one per compartment if the panel is compartmentalised, on one face thereof. The fire protective panel in accordance with the invention will now be described with reference to the accompanying drawing, of which: Figure 1 shows a panel in section, and Figure 2 shows panels in situ in bays in an aircraft wing. The panel shown in figure 1 comprises structures 10 of flexible resilient 'Atomel' melded polyester fibres encased in an envelope 11 of transparent impermeable plastics film, in compartments. The structures are reticulated with 70-100 pores per linear inch in all three dimensions. The structures are substantially filled with extinguishant powder 12 comprising calcined alumina of 1-3 microns particle size fluidised with 2% by volume micronised hydrophilic silica. The powder is introduced by evacuating and back-filling each compartment prior to final seam welding at for example 13 in figure 1, whilst retaining a vacuum therein of the order of 10 Torr. The vacuum causes the structure to be compressed and increases resistance to powder migration and assits upon rupture of the envelope, in propelling powder out of the compartment. Figure 2 shows a bay in the leading edge of an aircraft wing, formed by a skin 20 and an LE spar 21. To the rear of the spar is a fuel tank 22, while the bay contains a fuel pipe 23. A panel 24 of the type described above with reference to figure 1 but spot weld quilted instead of seam weld compartmentalised is attached to the front face of the spar 21 with an adhesive. Panels 25, formed to the shape of the pipe 23 during the evacuation process, are mounted on and surround the pipe. In a specific embodiment of the panel illustrated in figure 1, it is divided into discreet compartments 10 cm square by seams permitting the panel to be cut to a desired shape, and supplied with an adhesive patch on each compartment, the patch having a temporary backing strip which can be peeled off to expose the adhesive just prior to panel emplacement. The panel is 10 mm thick. In an alternative embodiment to that shown in figure 2, the panel 24 in attached to the leading edge skin 20 interior rather than to the spar 21.

Claims: CLAIMS 1 A fire protection panel comprising: a flexible resilient plastics three dimensionally reticulated structure, a flexible plastics film envelope closely and impermeably encasing the structure, and a fire extinguishant powder substantially filling the envelope and structure interstices, and and characterised in that the structure is compressed within the envelope whereby upon rupture of the envelope the structure expands and imparts a dispersive momentum to at least some of the powder. 2 A panel as claimed in claim 1 and wherein compression of the structure is obtained by quilting the panel at discreet locations. 3 A panel as claimed in claim 1 or claim 2 and wherein compression of the structure is obtained by outgassing the contents of the envelope prior to sealing. 4 A panel as claimed in any one of claims 1 to 3 and wherein the reticulated structure comprises an open pored polyurethane polyether or polyester foam, with the cell walls not necessarily fully blown, so that there is enhanced resistance to powder compaction. 5 A panel as claimed in any one of claims 1 to 3 and wherein the reticulated structure comprises a melded fibre structure formed by adhering carded masses of polyester or polyamide fibres at contact points thereof. 6 A panel as claimed in any one of the preceding claims and wherein the structure has 70-100 pores per linear inch in the uncompressed state. 7 A panel as claimed in any one of the preceding claims and wherein the extinguishant powder is any one or more of potassium cryolite, potassium and sodium bicarbonates, aluminium phosphates, potassium bicarbonates with urea reaction products, potassium dawsonite with potassium iodide and aluminium oxide. 8 A panel as claimed in any one of the preceding claims and wherein the powder has a particle size of 1-3 microns. 9 A panel as claimed in any one of the preceding claims and wherein the powder is fluidised with 1-2% by volume micronised hydrophilic silica as a dispersion and drying agent. 10 A panel as claimed in any one of the preceding claims and wherein the envelope film is any one or more of polyvinylidene chloride polyethersulphone and polyester. 11 A panel as claimed in any one of the preceding claims and wherein the film is transparent. 12 A panel as claimed in any one of the preceding claims and divided by compartments by seams along which it is possible to cut to conform the panel to a desired area. 13 A panel as claimed in claim 12 and wherein the compartments are 7 -10 cms square. 14 A panel as claimed in any one of the preceding claims and carrying on one exterior face at least one adhesive patch protected by a removable cover. 15 A panel as claimed in claim 14 and wherein the adhesive patch is arranged so that the panel will rather open upon shock penetration than the panel being removed from its mounting. 16 A panel as claimed in any one of the preceding claims and substantially as herein before described with reference to the accompanying drawings.

Inventors: HENSON, COLIN, WYETH, HAROLD WILLIAM GERALD
Applicants: THE SECRETARY OF STATE FOR DEFENCE IN HER BRITANNIC MAJESTY'S GOVERNMENT OF THE UNITED KINGDOM OF GREAT BRITAIN AND
Application year: 1982
Main classification: A62C3
IPC codes: B64D37, A62C3, E04B1