Abstract:
A pressure relief valve and a mating fuel tank bung are installed directly on a fuel tank. In one embodiment a bung is welded directly to a fuel tank, and thereafter a pressure relief valve is attached directly to the bung by mating threads. This system and installation method provides a cost and time effective installation process that is expedient, does not require additional pipes or plumbing fixtures, and the resulting installed valve may provide improved safety features due to the exclusion of additional pipes and plumbing positioned between the valve and the fuel tank and a compactness of design.

Description:
[0001]    This application claims priority on U.S. provisional patent application Ser. No. 61/756,766, filed on Jan. 25, 2013, and claims priority on U.S. provisional patent application Ser. No. 61/734,765, filed on Dec. 7, 2012, both entitled PRESSURE RELIEF VALVE. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a high flow pressure relief valve and a process for installing the same, for use in commercial vehicles, for example, and more particularly, to a high flow pressure relief valve that may be installed directly on a fuel tank without additional plumbing positioned between the valve and the tank. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention is particularly intended for use on commercial vehicles, although it may be used with any internal combustion engine connected to a fuel tank. In one particular application, LNG (Liquefied Natural Gas) trucks have one tank for holding natural gas and one smaller tank for holding the diesel used on the LNG truck. LNG engine manufacturers may desire a safety relief valve on the diesel tank to protect the diesel tank if accidental transfer of high pressure from the LNG tank occurs. Such a transfer of high pressure could occur if a pressure seal inside the LNG engine fails. A flow specification of this relief valve might be a flow rate as high as 3,000 standard cubic feet per hour (SCFH) which would prevent rupture of the diesel tank upon occurrence of the accidental transfer of high pressure from the LNG tank. Prior art pressure relief valves are mounted separately from the fuel tank and then plumbed to the fuel tank with hoses and fittings positioned between the valve and the tank. This remote installation of a valve is time intensive and costly and requires more space on the vehicle on which the assembly is installed. There is a need therefore for a safety valve that provides for a high flow rate and which is less time intensive and less expensive to install and which includes a more compact design. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides a pressure relief valve and a mating fuel tank bung which are installed directly on a fuel tank, and a process of installing the same. One aspect of the present invention provides a pressure relief valve bung that is welded directly to the tank, and thereafter a pressure relief valve is attached directly to the bung by mating threads. This system and installation method provides a cost savings over prior art devices because the installation process is expedient, no additional plumbing is required, and the resulting installed valve may include additional safety features compared to prior art valves due to the exclusion of additional plumbing positioned between the valve and the fuel tank of the present invention. The present invention is compact and provides for safety release flow rates that meet desired specifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a top view of one example embodiment of a pressure relief valve. 
           [0006]      FIG. 2  is a side cross-sectional view of the valve of  FIG. 1  in an unpressurized condition. 
           [0007]      FIG. 3  is a side cross-sectional view of the valve of  FIG. 1  in a pressurized condition and mounted on a bung secured to a fuel tank. 
           [0008]      FIG. 4  is a side view of one example embodiment of a fuel tank bung shown in  FIG. 3 . 
           [0009]      FIG. 5  is a top view of the bung of  FIG. 4 . 
           [0010]      FIG. 6  is top view of another example embodiment of a pressure relief valve. 
           [0011]      FIG. 7  is a side cross-sectional view of the valve of  FIG. 6  in a non-roll over position and a non-thermal relief position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    The invention discloses a pressure relief valve that is intended for use on commercial vehicles, although it may be used with any internal combustion engine connected to a fuel tank. 
         [0013]      FIG. 1  is a top view of one example embodiment of a pressure relief valve  10 . 
         [0014]      FIG. 2  is a side cross-sectional view of the valve  10  of  FIG. 1  in an unpressurized condition. Valve  10 , in the embodiment shown, includes a valve body  1 , a full function vent  2 , such as a slidable shaft, a sealing member  3 , such as an O-ring,  a biasing member  4 , such as a coil spring, a thermal relief member  5 , such as a thermal relief ring manufactured of a temperature dependent deformable material, a spring capture structure  6 , such as a baffle, and a second spring capture structure  7 , such as a cup washer. Valve body  1 , in one example embodiment, may be a 1½ PTF. In other embodiments, other sizes of valve body  1  may be utilized. O-ring  3  is positioned within a groove  12  of slidable shaft  2  and in an unpressured condition of the valve  10 , as shown in  FIG. 1 , the O-ring  3  seals against an interior surface  14  of valve body  1  to seal a fuel tank  16  ( FIG. 3 ) from leakage or spillage of fuel there from. A first end  18  of coil spring  4  is seated within a groove  20  of valve body  1  and a second end  22  of coil spring  4  is secured within cup washer  7  of baffle  6  by thermal relief ring  5 . In an unpressured condition of fuel tank  16  ( FIG. 3 ), coil spring  4  will tend to bias baffle  6  away from valve body  1  in a direction  24  until spring  4  is positioned in a its nominal, unpressurized condition. In this unpressurized position, O-ring  3  will seal valve  10 , thereby sealing fuel tank  16  ( FIG. 3 ) from leakage or loss of fuel through the valve body  1 . 
         [0015]      FIG. 3  is a side cross-sectional view of the valve  10  of  FIG. 1  in a pressurized condition and mounted on a bung  26  secured to a fuel tank  16 , such as with a weld  28 . Other securement mechanisms may be utilized to secure bung  26  to fuel tank  16 . Bung  26  may include securement structure  30 , such as internal threads, that may mate with securement structure  32 , such as internal threads, to quickly and easily secure pressure relief valve  10  on bung  26 . A sealing tape, not shown, may be placed around threads  32  of valve  10  prior to securement on threads  30  so as to render the connection between threads  30  and  32  air tight and fluid tight. 
         [0016]    In a pressured condition of fuel tank  16 , such as at pressures in a range of approximately 6.8 to 8.5 pounds per square inch (psi), as one example, the pressure on slidable shaft  2  may force slidable shaft to begin to move in a direction  34  such that a top portion  36  of slidable shaft  2  is moved away from contact with interior surface  14  of valve body  1 , which may allow pressurized air to escape through valve  10  between top portion  36  of slidable shaft  2  and interior surface  14  of valve body  1 . At pressures in a range of 10.0 to 15.0 psi, for example, the slidable shaft  2  may be completely clear of interior surface  14  so that the valve  10  may be referred to as completely open, thereby allowing a relatively large flow of pressurized air and/or fluid to escape through valve  10  between top portion  36  of slidable shaft  2  and interior surface  14  of valve body  1 , such as allowing a flow rate of 3,000 SCFH, with a maximum back pressure of 13 psi, for example. Such a flow rate of 3,000 SCFH, for example, may prevent rupture of the diesel tank upon pressurization of the fuel tank in the case of an accidental transfer of high pressure from the LNG tank to the fuel tank  16 . 
         [0017]    In this pressurized condition, as slidable shaft  2  is moved in direction  34 , coil spring  4  is compressed thereby drawing baffle  6  and cup washer  7  closer toward valve body  1  in direction  34 . Even in a fully pressurized condition wherein coil spring  4  is completely compressed, the spring will normally space baffle  6  a sufficient distance from valve body  1  such that pressured air and/or fluid may still exit the fuel tank  16  through valve body  1  and around top portion  36  of slidable shaft  2 . 
         [0018]    Pressure relief valve  10  further includes thermal relief ring  5 , such as a lead or a silver ring that will deform, such as by melting, for example, at a temperature of approximately 225 degrees Fahrenheit or higher, for example. The deformation of ring  5  may allow bottom portion  38  of slidable shaft  2  to be released from baffle  6  and cup washer  7 , thereby allowing shaft  2  to slide freely from valve body  1  and release pressure from fuel tank  16  without compression of coil spring  4 . Once slidable shaft  2  is released from baffle  6  and cup washer  7  by activation of thermal relief ring  5 , spring  4 , baffle  6  and cup washer  7  may no longer be connected to valve body  1  and thereafter spring  4 , baffle  6  and cup washer  7  may fall downwardly into an interior the fuel tank  16 , further allowing a quick release of pressure through pressure relief valve  10 . 
         [0019]      FIG. 4  is a side view of one example embodiment of a fuel tank bung  26  shown in  FIG. 3 . Referring to  FIGS. 3 and 4 , bung  26  may be secured to an aperture  40  within a wall  42  of fuel tank  16  by any means for a particular application, such as with a weld  28 . Valve body  1  may then be secured within bung  26  by mating bung threads  30  and valve body threads  32 . 
         [0020]    In this manner valve body  1  is secured directly on fuel tank  16  such that a portion of coil spring  4  and an entirety of baffle  6  and cup washer  7  are positioned within an interior  44  of fuel tank  16 . Moreover, due to this direct installation of pressure relief valve  10  on fuel tank  16 , there are no pipes or other plumbing fixtures positioned between valve  10  and fuel tank  16 , thereby eliminating safety defects in the present invention that may have been related to such prior art pipes or plumbing fixtures. Moreover, due to this direct installation of pressure relief valve  10  on fuel tank  16 , installation costs and component costs are reduced because such prior art pipes and plumbing fixtures need not be purchased or installed in the present inventive installation method. Furthermore, the direct installation process of the present invention results in a more compact size pressure relief valve that requires less space than prior art valves, which included additional pipes and plumbing fixtures. 
         [0021]      FIG. 5  is a top view of the bung  26  of  FIG. 4 . 
         [0022]      FIG. 6  is top view of another example embodiment of a pressure relief valve  10 . In this embodiment, valve body  1  includes a barb  11  which includes a vent aperture  46  extending there through and communicating with an interior of slidable shaft  2 . 
         [0023]      FIG. 7  is a side cross-sectional view of the valve of  FIG. 6 , taken along line  7 - 7 , in a non-roll over position and in a non-thermal relief position. In this non-thermal relief position, thermal ring  5  is still intact, and has not been deformed by high temperatures within a fuel tank on which pressure relief valve  10  is installed. Accordingly, in this position thermal relief ring  5  secures slidable shaft  2  to baffle  6  and cup washer  7 . 
         [0024]    In this non-roll over position, valve body  1  is positioned vertically above baffle  6  and cup washer  7 , as measured in direction  34 , such that gravity forces a float  8 , such as a float manufactured of a plastic material, and a ball  9 , such as a stainless steel ball, downwardly and away from valve body  1  and aperture  46 , in downward direction  24 . Float  8  includes a seal  10  secured to a side surface  48  of float  8  by a projection  50  and extending over a top surface  52  of float  8 . In this non-roll position, seal  10  does not block fluid, air or other gases, from venting through vent aperture  46  in valve body  1  and outwardly to the atmosphere through barb  11 . 
         [0025]    In a roll over position, such as when a truck and/or a tank to which pressure relief valve  10  is secured, rolls over, such as during an accident, valve body  1  may be positioned other than vertically upright. In particular, in such a roll over position, an axis  54  of relief valve  10  may not be positioned vertically but may be positioned at an angle to vertical, such that baffle  6  and cup washer  7  may be positioned upwardly of or vertically above valve body  1 . In such a position, gravity may force float  8  downwardly in a direction  34  such that seal  10  seals against aperture  46 , thereby preventing leakage of fuel and/or gases through aperture  46  of relief valve  10 , and possibly preventing a fire due to fuel leakage. Float  8  and seal  10  may be held securely against aperture  46  in this position by the downward force of gravity on float  8  and on ball  9 , which will force float  8  against aperture  46 , wherein ball  9  may be made of a heavily weighted material, such as stainless steel. 
         [0026]    Accordingly, there is provided a high flow, pressure relief valve  10  that also allows thermal relief venting during high temperatures in a fuel tank, wherein ring  5  deforms, and also inhibits leakage of fuel during roll-over situations, such that fuel does not leak from a fuel tank during an accident, due to movement of float  8 . All of these functions are preformed by compact, sturdy, easily installed relief valve  10 . 
         [0027]    In the above description numerous details have been set forth in order to provide a more through understanding of the present invention. It will be obvious, however, to one skilled in the art that the present invention may be practiced using other equivalent designs.