Patent Publication Number: US-8122656-B1

Title: Fire suppression surface system

Description:
RELATED APPLICATIONS 
     This application claims benefit of prior-filed provisional App. No. 60/504,350 entitled “Fire suppression surface system” filed Sep. 18, 2003 in the name of Peter D. Poulsen, said provisional application being hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND 
     The field of the present invention relates to fire suppression. In particular, apparatus and methods are described herein for passive suppression of combustion of flammable liquids on surfaces. 
     Surfaces where fluid spills can occur and where ignition and combustion of the fluids are particularly dangerous must have fire suppression systems in place. Examples may include, but are not limited to: an aircraft carrier flight deck or hangar deck; a helipad; the floor of an engine compartment; the ground near a refueling facility; the floor of a vehicle repair facility; the floor of a fuel, solvent, or chemical storage area; the floor of a fuel, solvent, or chemical processing facility; the ground near a fuel, solvent, or chemical loading or unloading zone or shipping terminal; the floor of a semiconductor processing facility; the ground of a racetrack pit area; an oil drilling platform; an aircraft hangar; or the floor of a mill or manufacturing facility. Even without the violence of an aircraft or vehicle crash, leaked or spilled fuel on a surface is a fire threat. In the case of a crash or accident, structural damage may be minor but there may nevertheless be a great risk of fire due to potential ignition of fuel spilled from fuel tanks. Burning fuel flows onto the ground, a floor, a deck, or other surface and spreads rapidly to surrounding areas. Any fire that is not suppressed or extinguished immediately may kill or injure vehicle occupants, firefighters, other rescue or emergency personnel, or bystanders. A fire may also result in damage to the spill surface or structure that supports, houses, or otherwise attends the spill surface. For these and other reasons, it is desirable to provide fire suppression for such surfaces where spills of flammable fluids may occur. 
     SUMMARY 
     A passive fire suppression surface system comprises a substantially flat sheet and a plurality of support members. The sheet has a plurality of fluid channels therethrough, with each fluid channel having an upper opening at an upper surface of the sheet and a corresponding lower opening at a lower surface of the sheet. Fluid spilled on the upper surface of the sheet may flow therethrough by flowing through at least one of the fluid channels. The support members lie on a support surface in a spaced-apart arrangement, and the sheet rests on the support members and is thereby positioned substantially parallel to and offset vertically above the support surface. The support surface and the sheet thereby define a containment space for receiving fluid spilled on the upper surface of the sheet that flows through the fluid channels of the sheet. The area of each upper opening is larger than about twice the area of each corresponding lower opening so as to restrict flow of air into the containment space or restrict escape of combustion products from the containment space, thereby suppressing combustion of a flammable fluid spilled on the upper surface of the sheet. A method for passively suppressing combustion of flammable fluid spilled on the support surface comprises covering at least a portion of the support surface with the sheet supported by the support members. 
     Objects and advantages pertaining to passive fire suppression on surfaces may become apparent upon referring to the disclosed embodiments as illustrated in the drawings and disclosed in the following written description or claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  are top perspective and cross-sectional views of a sheet of a fire suppression surface system. 
         FIGS. 2A and 2B  are top and bottom views, respectively, of a sheet of a fire suppression surface system. 
         FIGS. 3A and 3B  are bottom perspective views of a sheet of a fire suppression surface system. 
         FIG. 4  is a top perspective view of a fire suppression surface system. 
         FIGS. 5A and 5B  are top perspective and cross-sectional views, respectively, of a fire suppression surface system. 
         FIGS. 6A and 6B  are top perspective and cross-sectional views, respectively, of a fire suppression surface system. 
         FIG. 7  is a cross-sectional view of a fire suppression surface system. 
     
    
    
     The embodiments shown in the Figures are exemplary, and should not be construed as limiting the scope of the present disclosure or appended claims. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIGS. 1A-1D ,  2 A- 2 B,  3 A- 3 B,  4 ,  5 A- 5 B,  6 A- 6 B, and  7  illustrate exemplary embodiments of a passive fire suppression surface system. A substantially flat sheet  100  has a plurality of fluid channels  106  therethrough. Each channel  106  has an upper opening  106 A at the upper surface of the sheet  100 , and a lower opening  106 B at the lower surface of the sheet  100 . Fluid spilled on the upper surface of the sheet may flow through the sheet  100  through at least one, and typically many, of the fluid channels  106 . The sheet  100  rests on a plurality of support members  120  that in turn lie on a support surface  10  in a spaced-apart arrangement. The support members  120  position the sheet  100  substantially parallel to and offset vertically above the support surface  10 . The sheet  100  and the surface  10  therefore define a containment space  20  therebetween ( FIGS. 4B ,  5 A- 5 B, and  6 A- 6 B), for receiving fluid spilled on the upper surface of the sheet  100  that flows through the fluid channels  106 . The area of each upper opening  106 A is larger than about twice the area of a corresponding lower opening  106 B, and may be larger than about 4 to 10 times the area of the corresponding lower opening  106 B. This difference in area restricts flow of air into the containment space or restricts escape of combustion products from the containment space. Either or both of these may suppress combustion of flammable liquid spilled on the upper surface of the sheet, whether already burning when spilled or ignited after being spilled (such fire suppression might be characterized as suffocation). The sheet  100  may comprise any sufficiently rigid, sufficiently non-flammable material, including but not limited to metallic material, ceramic material, or polymer material. Stainless steel and titanium are examples of metallic materials that may be employed for forming sheet  100 . The sheet may be formed in an suitable way, including but not limited to molding, casting, stamping, extrusion, or milling. 
     The fluid channels  106  may be formed so that the cross-sectional area of each fluid channel  106  decreases substantially monotonically from the upper opening  106 A to the lower opening  106 B. The exemplary embodiment shown in the Figures has frusto-conical fluid channels ( FIGS. 1B-1C  and  2 A). Channels in the shape of inverted, truncated square or rectangular pyramids could be employed. Any channel shape suitable for enabling adequate flow of spilled fluid and with sufficiently differing areas of the upper and lower openings shall fall within the scope of the present disclosure or appended claims. The channels may be arranged on sheet  100  in any suitable way. It may be convenient to arrange the fluid channels  106  in a two-dimensional lattice pattern (square, rectangular, trigonal, hexagonal, or some other regular pattern; a square lattice pattern is shown in the Figures). Exemplary dimensions for fluid channels may be: lower opening area less than about 10 mm 2 , or about 4-6 mm 2 ; sheet thickness between about 3 mm and about 10 mm, or about 5-7 mm; fluid channels arranged on a lattice pattern with a spacing between about 3 mm and about 10 mm, or about 5-7 mm. Other dimensions or arrangements, including dimensions outside these ranges, may nevertheless fall within the scope of the present disclosure or appended claims. 
     Arrangement of fluid channels  106  on a two-dimensional lattice pattern sufficiently close together results in an upper surface of sheet  100  comprising a plurality of elongated ridges  104  ( FIGS. 1A and 2A ; the ridges in these examples comprise alternating saddle segments and flat segments). The two-dimensional lattice pattern results in these ridges  104  extending along the sheet in at least two directions to form a grid. The ridges  104  may be made sufficiently narrow (by sufficiently close spacing of the fluid channels  106 ) so as to substantially eliminate accumulation of fluid on the upper surface of the sheet. For example, the flat segments of the ridges in the exemplary embodiments of  FIGS. 1A and 2A  become smaller with decreasing spacing of the fluid channels. Alternatively, any flat segments of the ridges  104  may be tilted, rounded, or otherwise adapted for eliminating fluid accumulation thereon. The grid also provides a non-slip or non-skid surface for foot traffic or vehicles. The arrangement of the fluid channels  106  or ridges  104  may be altered in any suitable way so as to achieve desired non-slip, non-skid, or other frictional properties for the upper surface of the sheet  100 . Such alterations or adaptations shall fall within the scope of the present disclosure or appended claims. 
     The plurality of support members  120  may comprise elongated support members lying on the support surface in a spaced-apart, side-by-side arrangement. The support members  120  position the sheet  100  substantially parallel to and offset vertically above the support surface  10 . The sheet  100  and the surface  10  therefore define a containment space  20  therebetween for receiving fluid spilled on the upper surface of the sheet  100  that flows through the fluid channels  106 . The elongated support members  120  may be secured to or formed on the lower surface of the sheet  100 . In this case deployment or installation of the fire suppression surface system comprises covering the desired area of the support surface  10  with sheet  100 , with support members  120  already on sheet  100 . Alternatively, the sheet  100  and support members  120  may comprise mechanically separate components. If comprising separate components, deployment or installation of the fire suppression surface system comprises first placing support members  120  on the desired area of support surface  10 , and then covering the desired area with sheet  100 . The support members  120  may be secured to or formed on the support surface  10 . Regardless of the method used therefor, after deployment or installation the sheet  100  rests on the support members  120 , which in turn lie on support surface  10  ( FIGS. 4B ,  5 A- 5 B, and  6 A- 6 B). 
     The support members may comprise any material or material combination sufficiently rigid for supporting sheet  100  and any loads thereon (vehicles, personnel, equipment, and so forth). The support members may be configured to support the sheet  100  at a height between about 3 mm and about 10 mm, or about 5-7 mm, above the support surface  10 . Other heights may be employed and may fall with the scope of the present disclosure or appended claims. The elongated support members  120  may be spaced-apart laterally by about 20-100 mm, or about 40-70 mm. Any spacing that provides sufficient support for the sheet  100  and any load thereon may be employed, and shall fall within the scope of the present disclosure or appended claims. Depending on the area to be covered, the sheet  100  may be provided as a single sheet, or in multiple pieces that are tiled together to cover the desired area of support surface  10  regardless of its size. 
     In some circumstances it may be desirable to support sheet  100  from above, rather than from below. In other words, the sheet  100  may be suspended by support members to hang above the surface  10 . Such suspension of sheet  100  above surface  10  shall fall within the scope of the present disclosure or appended claims. 
     It may be desirable to impede flow of air or fluid within the containment volume. Spaced-apart, side-by-side elongated support members  120  may serve to impede flow in one dimension. Baffle members  122  may be positioned between the support members  120  so as to further impede flow of air or spilled fluid within the containment space  20  ( FIGS. 5A-5B  and  6 A- 6 B). Elongated baffle members  122  may be oriented approximately transversely to the elongated support members ( FIGS. 6A-6B ), so as to impede flow of air or spilled fluid parallel to the support members  120 . Such impeded flow may reduce the amount of air that may reach burning fluid in the containment space from edges of the sheet  100 , or may reduce the amount of fluid upwelling through the fluid channels  106  if the support surface  10  is tilted (as might be the case on the deck of a ship). Space is left between baffle members  122  and support members  120  to allow some restricted flow of air or fluid, so that air trapped in the containment space does not impede flow of spilled fluid through the fluid channels  106 , or to allow spilled fluid to be recovered from the containment space by flow to an edge of the sheet  100 . The baffle members  122  may be secured to or formed on the lower surface of sheet  100 , or may be provided as mechanically separate components. If provided as separate components, baffle members  122  may be secured to or formed on the support surface  10 . Description of methods of deployment or installation of the fire suppression surface system with baffle members  122  is similar to the description of such methods pertaining to the support members  120 , as set forth hereinabove. 
     The lower surface of sheet  100  may be substantially flat except for the lower opening  106 B of the fluid channels  106 . Sheet  100  would therefore comprise a slab with fluid channels  106  therethrough ( FIG. 1B ). Alternatively, the lower surface of the sheet  100  may include recessed regions  108  between the fluid channels  106  ( FIGS. 1C ,  1 D,  2 A, and  3 A- 3 B). These recessed regions  108  may form a grid roughly corresponding to the grid of ridges  104  on the upper surface of sheet  100 . Such recessed regions  108  may serve to reduce the weight of sheet  100 . Such recessed areas also increase the surface area of the lower surface of sheet  100 , which may provide enhanced convective cooling of sheet  100 . This may be advantageous when the sheet  100  is deployed outdoors and may be subject to a significant solar load, for example, and heating of the sheet under a solar load my increase the risk of ignition of flammable fluids. The increased surface area of the lower surface of sheet  100  may also increase the rate at which heat may be dissipated during a fire by conduction or convection. 
     Fire retardant or fire suppressant material  113  may be applied to the lower surface of sheet  100 . Suitable materials may include, but are not limited to:
     a) Binary agents. For example, separately encapsulated acid and carbonate or bicarbonate salts would release carbon dioxide upon mixing, which would tend to smother a fire. The encapsulation means (an organic polymer coating, for example) might be soluble in the flammable liquid, or melted or decomposed by the heat of the fire.   b) Decomposing agents. Carbonate or bicarbonate salts may decompose at elevated temperatures (as in a fire) and release carbon dioxide, which would tend to smother the fire. Hydrated salts may release their water of hydration at elevated temperatures, which may serve to smother the fire or may serve to carry away heat of vaporization and cool the fire.   c) De-volatilizing agents. Organic or polymeric coatings (such as shellacs) may absorb volatile flammable fluids, thereby lowering the vapor pressure and suppressing the fire. Similarly, gelling or polymerizing agents may also serve to reduce vapor pressure of volatile flammable liquids, although they may make subsequent cleanup of the spilled liquid more difficult.
 
These, or any other suitable heat- or fluid-activated fire retardant or fire suppressant material may be employed, and shall fall within the scope of the present disclosure or appended claims. Suitable fire retardant or fire suppressant materials may be activated by contact with spilled fluid, by the heat of combustion, or both. The fire retardant or fire suppressant material may be applied to a substantially flat lower surface of sheet  100 . The presence of recessed regions  108  on the lower surface of sheet  100  results in an increased surface area where fire retardant or fire suppressant material may be applied, or still more fire retardant or fire suppressant material may be applied by completely or partially filling the recessed regions therewith (as in  FIGS. 1D and 3B ). Since the fire retardant or fire suppressant material is applied to the lower surface of the sheet  100 , it is not subject to wear or accidental removal by foot or vehicular traffic or other environmental influences.
   

     The fire suppression surface system may be deployed or installed in a variety of environments wherein flammable fluids are in use. Examples of surfaces where the system may be deployed or installed may include but are not limited to: an aircraft carrier flight deck or hangar deck; other warships; an oil tanker or other fuel-carrying vessel; freighters; other ships or vessels; a helipad; the floor of an engine compartment; the ground near a refueling facility; the floor of a vehicle repair facility; the floor of a fuel, solvent, or chemical storage area; the floor of a fuel, solvent, or chemical processing facility; the ground near a fuel, solvent, or chemical loading or unloading zone or shipping terminal; the floor of a semiconductor processing facility; the ground of a racetrack pit area; an oil drilling platform; an aircraft hangar; or the floor of a mill or manufacturing facility. 
     The effectiveness of the fire suppression surface system may be enhanced by stacking two sheets  100  over the support surface  10  ( FIG. 7 ). The first (lower) sheet  100  rests on its corresponding support members  120  on the support surface  10 . The second sheet  100  rests on its corresponding support members  120  on the lower sheet. If the supports members  120  are elongated, it may be desirable to orient them in differing directions, perhaps substantially perpendicular to one another, for structural strength or stability. If two or more sheets are stacked, the fluid channels of all but the uppermost sheet may be larger and more widely spaced, since their upper surfaces are not in direct contact with personnel, vehicles, or equipment. 
     Fluid channels  106  having frusto-conical, truncated pyramidal, or similar shapes may also serve to preferentially direct heat radiated from below the sheet  100 . If the surfaces of sheet  100  are sufficiently reflective (i.e., have sufficiently low emissivity) at the relevant wavelengths, then a portion of heat radiated from below the sheet will be directed preferentially in a direction substantially perpendicular to the sheet  100  (by direct radiation through lower openings  106 B, with or without reflecting from the inner surface of fluid channels  106 ). For example, calculations for closely-spaced frusto-conical fluid channels having an upper opening diameter about 2.5 times the lower opening diameter, and a length about 5 times the lower opening diameter, yield a radiated heat angular distribution having over 95% of the radiated heat emitted in directions more than 50° above horizontal. Such preferential upwardly-directed radiation of heat may allow firefighters or other emergency personnel to approach the fire more closely without being burned by heat radiating from the surface. Other shapes or arrangements of the fluid channels to achieve desired radiant heat angular distributions may be designed and implemented, and shall fall within the scope of the present disclosure or appended claims. 
     The emissivity of sheet  100  determines in part the effectiveness of the preferential direction of heat radiated from below the sheet. For relatively low emissivity (below about 70%), preferential upwardly-directed radiation of heat from below sheet  100 , as described hereinabove, is observed. For relatively high emissivity (above about 70%), preferential upwardly-directed radiation is diminished or absent. For a sheet with sufficiently low emissivity, a substantial portion of radiation incident on the sheet from below is reflected back toward the support surface  10  and may be reradiated therefrom, while a substantial portion of radiation passing through a lower opening  106 B and incident on the inner surface of a fluid channel  106  is reflected and redirected in a more upward direction. These result in preferential upwardly-directed radiation. For a sheet  100  with high emissivity (i.e., high absorptivity), however, a substantial portion of radiant heat incident on sheet  100  (from below or on the inner surfaces of fluid channels  106 ) is absorbed by sheet  100  and reradiated in a substantially isotropic fashion. Transition between these two exhibited behaviors has been observed to occur over a range of emissivity around 70%, although this limit may depend on the details of the dimensions and geometry of the sheet  100  and fluid channels  106 . 
     It may be desirable to employ a sheet  100  on any hot surface for preferential redirection of heat radiated therefrom, even in the absence of the possibility of flammable liquid spills or ignition. A sheet  100  with support members  120  may be positioned on a surface of any orientation when preferential redirection of heat radiated therefrom may be desired. Depending on the orientation of the covered surface, the support members  120  may or may not support the weight of the sheet  100 , and securing of support members to the sheet  100  or the covered surface may or may not be required. However, support members  120  still serve to provide space between the covered surface and sheet  100  so as to reduce or substantially eliminate direct conduction of heat therebetween (which would serve to diminish the preferentially directed radiation of heat). Many examples of hot surfaces may be imagined where such preferential direction of radiated heat may be desirable (such as outer surfaces of ovens, kilns, or furnaces, for example), and use of sheet  100  and support member  120  for thus preferentially directing radiated heat from any desired surface shall fall within the scope of the present disclosure or appended claims. 
     If the sheet  100  comprises metallic material, fluid channels  106  may be sized and arranged to yield desired electromagnetic properties. For example, it may be desirable to engineer the electromagnetic properties of sheet  100  so that it functions as a specular ground plane for radar or for radio frequency communications, thereby facilitating use of portable phones, cell phones, radios, microwave transmission, or other wireless telecommunications. Any suitable arrangement of sheet  100  and fluid channels  106  for yielding desirable electromagnetic properties may be designed and implemented, and shall fall within the scope of the present disclosure or appended claims. 
     For purposes of the present disclosure and appended claims, the conjunction “or” is to be construed inclusively (e.g., “a dog or a cat” would be interpreted as “a dog, or a cat, or both”), unless: i) it is explicitly stated otherwise, or ii) two or more of the listed alternatives are mutually exclusive within the particular context, in which case “or” would encompass only those combinations involving non-mutually-exclusive alternatives. It is intended that equivalents of the disclosed exemplary embodiments and methods shall fall within the scope of the present disclosure or appended claims. It is intended that the disclosed exemplary embodiments and methods, and equivalents thereof, may be modified while remaining within the scope of the present disclosure or appended claims.