Abstract:
A highly protective vented firewall ( 28 ) is supported between upstanding columns or beams ( 15 ). The firewall is made of an inorganic cementitious material which is preferably inorganic phosphate cement. Vent openings ( 35 ) are provided to enable flow of cooling air through the firewall during normal operating conditions. A heat-activatable means ( 35 ) automatically closes the vents should a fire occur.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application 60/724,587 filed Oct. 7, 2005. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an improved firewall for protection of high-value and essential equipment such as high-voltage transformers in an electrical utility station. Transformers of this type typically contain a flammable oil which can ignite into a dangerous fire in the event of a major short circuit or other equipment failure or environmental problems. Such fires can reach very high temperatures which can spread the fire to adjacent equipment such as other transformers, putting in jeopardy the ability of the utility service to provide electrical energy. 
         [0003]    The improved firewall is made of cementitious inorganic composite material which has good insulation and fire-resistant properties. In a presently preferred form the composite material is an inorganic phosphate cement as described in U.S. Pat. No. 6,103,007, the disclosure of which is incorporated herein by reference. The wall is preferably made in sections which are supported between spaced-apart vertically upstanding girders such as steel I beams. The beams are preferably protected by overlying sheets of glass-fiber fabric impregnated with the cementitious material. 
         [0004]    The new feature to which this application is directed relates to firewalls with cooling vents to encourage flow of cooling air over the transformer during normal operation. The life expectancy of power-station high-voltage transformers depends largely on the transformer temperature during operation. If the temperature rise exceeds certain limits, aging of insulting material in the transformer is accelerated, and the cooling function of oil in the transformer is deteriorated. 
         [0005]    Solid firewalls at the sides of a transformer significantly reduce cooling airflow, and the heat-generating transformer will in effect be operating in an oven. One solution is to de-rate the transformer, but this results in an undesirable decrease in performance. Nevertheless, the firewalls must present a solid flame barrier should a fire occur. The firewall of this invention has vents which remain open during normal operation, but the vents are automatically triggered to close in the event of a fire. The improvement of this invention is especially suitable for modification of an unvented firewall as described in my PCT application PCT/US2005/038674, published as WO 2006/047644 A2, the disclosure of which is incorporated herein by reference. Some of the drawings and text from this earlier application are included in the present application for convenience. 
       SUMMARY OF THE INVENTION 
       [0006]    A firewall system comprising an upright firewall of inorganic cementitious material, preferably inorganic phosphate cement. The firewall is supported between space-apart vertical beams. The firewall has a vented portion which is normally open to enable a flow of cooling air. A heat-activatable means is provided to close the vented portion should a fire occur. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of three spaced-apart firewalls positioned on opposite sides of equipment (such as power-station transformers) to be protected; 
           [0008]      FIG. 2  is a perspective view of a panel, partly broken away, the firewall having a plurality of vertically stacked such panels; 
           [0009]      FIG. 3  is a top perspective view of the firewall; 
           [0010]      FIG. 4  is a perspective view of a lower end of a firewall section as modified to include the cooling-vent panel of the present invention; 
           [0011]      FIG. 5  is similar to  FIG. 4 , but shows the cooling vent in a closed position; 
           [0012]      FIG. 6  is a perspective view of a modified lower firewall panel for positioning above the cooling-vent panel; 
           [0013]      FIG. 7  is a front elevation of a lower end of a firewall stack; and 
           [0014]      FIG. 8  is a top view of the assembly shown in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    Referring to  FIGS. 1-3 , showing my earlier unvented firewall system as disclosed in the aforementioned PCT application, three spaced-apart firewall systems  10  are shown on opposite sides of equipment such as transformers  11  and  12  (shown simply as blocks) to be protected. Each system has a firewall  13  which preferably comprises a vertically stacked plurality of firewall panels  14  made of inorganic cementitious material. Firewall  13  is supported between girders such as vertically upstanding and spaced-apart I beams  15  having lower ends embedded in a concrete base  16  on which the transformers are mounted. 
         [0016]    In a typical configuration, firewall panels  14  are about 5 feet high, 8½ feet wide, and 3½ inches thick. I beams  15  typically have flanges  18  which are spaced apart by 8 to 12 inches as shown in  FIG. 3 , and the panels are provided with hollow spacers  19  at opposite ends so the panels make a snug slip fit between the flanges when lowered between the I beams. The spacers are preferably made of the same fire-resistant cementitious material from which the panels are made. The firewall can be as tall as necessary to shelter the equipment being protected, and are typically 20 to 40 feet high, thus using four to eight stacked panels. 
         [0017]    In a presently preferred form each firewall panel  14  comprises a vertically stacked series of elongated members  21  which are hollow, and of rectangular cross section as shown in  FIG. 2 . Members  21  are made a glass-fiber fabric which is impregnated with inorganic cementitious material to provide a wall thickness of about ¼ inch. The outside dimensions of the member are typically about 3½ by 5 inches. 
         [0018]    While various inorganic cementitious materials can be used, a preferred material is an inorganic phosphate cement as described in the aforementioned U.S. Pat. No. 6,103,007. This material has a long pot life after mixing to provide ample time for impregnating the glass-fiber fabric, is highly resistant to fire, and has good insulating properties. Each member  21  can be formed by wrapping the impregnated fabric around a wood core or mandrel which is withdrawn after the cementitious material has hardened. 
         [0019]    A plurality (typically twelve) of members  21  are then vertically stacked together, and wrapped with an outside layer  22  of glass-fiber fabric impregnated with the cementitious material to form a panel  14 . To provide snug nesting of vertically stacked panels, a lower end  23  of each panel is slightly concave, and an upper end  24  is slightly convex as shown in  FIG. 2 . 
         [0020]    As shown in  FIG. 8 , I beams  15  are also covered with a skin  25  of the cementitious-material-impregnated glass-fiber fabric. The panels are vertically secured by threaded fasteners  27  extending through the I beam flanges and panels. Exposed portions of the fasteners are covered with a protective coating of the cementitious material. 
         [0021]    An improved vented firewall  28  is shown in  FIGS. 4-8 . Firewall  28  corresponds to the above-described  13  with the exception of the two lowermost panels  29  and  30 , and the addition of a sliding panel  31 . Panels  29 - 31  are made of the above-described inorganic cementitious material. 
         [0022]    Panel  29  generally corresponds to solid panels  14 , with the exception that spacers  32  at opposite ends of the panel are extended downwardly to rest on a firewall base  33 . As best seen in  FIG. 6 , each extended spacer defines a channel  34  extending to both ends of the spacer. 
         [0023]    Panel  30  is positioned immediately below panel  29 , and defines a multiplicity of venting openings  35 , typically of square or rectangular shape. It is through these openings that cooling air is enabled to flow during normal transformer operation. Both of panels  29  and  30  are fixed in position by the weight of the other stacked panels above them. 
         [0024]    Sliding vent-closure panel  31  is solid, and is supported at its opposite ends in spacer channels  34  to be movable vertically between an upper vent-open position ( FIG. 4 ) and a lower vent-closed position ( FIG. 5 ). In moving between these positions, panel  31  rides along a pair of bearing-like and spaced-apart vertical bars secured to the front faces of panels  29  and  30 . 
         [0025]    Sliding panel  31  is normally held in the upper vent-open position by a pair of heat-activated trigger bars  38  made of a meltable material such as aerospace tooling wax (a machinable wax with a softening temperature of about 226 F, as available from Flexbar Machine Corporation, is satisfactory), or a low-melting-point eutectic metal. The bars are vertically elongated, and of rectangular cross-section, to male a snug fit in channels  34 . The material of the trigger bars is selected to soften and melt at a temperature in the range of about 180°-200° F. which is quickly reached in the event of a fire. When this occurs, the weight of panel  31  causes it to slide downwardly automatically to the vent-closed position, thereby blocking spreading of the fire. 
         [0026]    If the bars  38  tend to slump (under the weight of the panel) at normal temperatures, they can be stiffened with slender metal rods which will collapse when the bar material melts. In another embodiment, heating coils can be cast into the material of the trigger bars. Upon receipt of a signal from a smoke alarm, the coils are electrically activated to melt the bars. 
         [0027]    There has been described a new vented firewall system for use with equipment such as heavy-duty power station electrical transformers. During normal operation, the firewall system is vented to enable flow of cooling air over the transformers. In the event of a fire, the cooling-air vents are automatically closed to prevent the fire from spreading.