Abstract:
A relief valve configured to allow content held within a vessel to be release under pressure is disclosed. The relief valve is configured to expose a release outlet when pressure within the vessel exceeds a release pressure, and the relief valve is further configured to maintain exposure of the release outlet after pressure within the vessel falls below the release pressure.

Description:
PRIORITY STATEMENT 
     This application claims benefit to U.S. Provisional Patent Application No. 61/979,095 filed Apr. 14, 2014, the entirety of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Relief valves are used to control or limit the pressure in a system or vessel which can build up by a process upset or fire in the vessel. In particular, relief valves are used on vessels such as tank cars carrying commodities like ethanol or crude oil to allow the pressurized contents to flow from the relief valve in the event of a fire or other system failure. Present relief valves used with railroad tank cars open when the pressure in the vessel rises above a predetermined amount, but such valves do not remain open after the initial quick release in pressure. In these valves, the poppet of the valve re-seats when the initial quick release in pressure is achieved, thus not allowing additional pressure or contents to be relieved from the vessel. The present relief valve solves the existing limitations. 
     SUMMARY 
     A pressure relief valve is disclosed for controlling or limiting the pressure in a vessel which can build up by a process upset or fire. More specifically, a pressure relief valve is disclosed for use with a railroad tank car carrying commodities such as ethanol or crude oil that will allow a full emptying of the vessel&#39;s contents when the vessel is involved in a fire, allowing all contents of the vessel to be emptied before failure of the container. The present disclosure provides a mechanism whereby once the relief valve opens at the preset pressure, it will remain held open at a predetermined height. The relief valve is a direct spring-loaded valve designed to open at a preset pressure. When the pressure in the system or vessel exceeds this preset pressure, the relief valve will open first to a full open position to allow the pressure in the system to be reduced, and then remain held open at a pre-determined height. The opening of the relief valve in the full open position using the momentum of the poppet allows the contents to flow out at a higher rate to allow maximum flow capacity through the relief valve. Then, as the pressure within the vessel decreases below the preset pressure, the relief valve returns to a locked but still open position at a predetermined height so that content can continue to flow out of the vessel. The spring-actuated mechanism locks a stem of the relief valve, and one or more locking pins are released into a recess in the stem so as not to allow the relief valve to close beyond the height of the recess. This allows the relief valve to remain open and continually release the contents of the vessel even though the pressure in the vessel drops below the preset pressure of the valve. By allowing the relief valve to remain open after the pressure within the vessel falls below the preset pressure, an added benefit of preventing, at least in part, the vessel from rupturing may also be realized. A further advantage of allowing remote or direct release of the relief valve in the event that it is determined the valve no longer needs to be held open in the locked position is also disclosed. 
     According to some embodiments, a relief valve for use with a vessel is disclosed. The relief valve may comprise an inlet portion capable of being coupled to the vessel; a stem; a poppet coupled to the stem and having a valve seat engaged to the inlet portion, the poppet configured to translate to a plurality of open positions where the valve seat is disengaged from the inlet portion to enable content to flow through the inlet portion into the relief valve, and translate to a closed position where the valve seat is engaged to the inlet portion to prevent flow into the relief valve; a bias member disposed configured to exert a bias force against the poppet to retain the poppet in the closed position and prevent the valve seat from disengaging from the inlet portion when the bias force is greater than a release pressure at the inlet portion; and a locking assembly configured to hold the poppet in at least a first open position of the plurality of open positions when the release pressure drops below the bias force. 
     According to some embodiments, a relief valve capable of being coupled to a vessel is disclosed. The relief valve may comprise an inlet portion; a stem; a poppet coupled to the stem and having a valve seat engaged to the inlet portion, the poppet movable between an open position where the valve seat is disengaged from the inlet portion to enable content to flow through the inlet portion, and a closed position where the valve seat is engaged to the inlet portion to restrict flow through the inlet portion; a spring disposed around the stem, the spring configured to exert a spring force against the poppet to prevent the poppet from translating to the open position when the spring force is greater than a release pressure within the vessel; and a locking assembly configured to retain the poppet in the open position once it has moved to the open position, even when the release pressure drops below the spring force; wherein the poppet is configured to translate to the open position when the release pressure is greater than the spring force. 
     Other objects, advantages, features, properties and relationships will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments that are indicative of the various ways in which the principles of the invention may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a relief valve. 
         FIG. 2  is top view of the relief valve of  FIG. 1 . 
         FIG. 3  is a cross-sectional view along Section  3 - 3  of  FIG. 2 . 
         FIG. 4  is a front elevational view of the relief valve of  FIG. 1 . 
         FIG. 5  is a cross-sectional view along Section  5 - 5  of  FIG. 4  depicting a locking assembly of the relief valve. 
         FIG. 6  is a cross-sectional view along Section  3 - 3  of  FIG. 2  and a top view of a locking assembly of the relief valve in a closed position, with the stem of the locking assembly in an unlocked position. 
         FIG. 7  is a view similar to  FIG. 6 , with the stem of the locking assembly in a locked position. 
         FIG. 8  is a cross-sectional view of a locking assembly of the relief valve in a fully open position with stem of locking assembly above the locked position. 
         FIG. 9  is a cross-sectional view of a locking assembly of the relief valve in an open position with stem of locking assembly in a locked position. 
         FIG. 10  illustrates a release feature of a relief valve in a first position. 
         FIG. 11  illustrates the release feature of  FIG. 10  in a second position. 
     
    
    
     DETAILED DESCRIPTION 
     The description that follows describes, illustrates and exemplifies one or more embodiments of the present invention in accordance with its principles. This description is not provided to limit the invention to the embodiments described herein, but rather to explain and teach the principles of the invention in order to enable one of ordinary skill in the art to understand these principles and, with that understanding, be able to apply them to practice not only the embodiments described herein, but also other embodiments that may come to mind in accordance with these principles. The scope of the present invention is intended to cover all such embodiments that may fall within the scope of the appended claims, either literally or under the doctrine of equivalents. 
       FIGS. 1-9  illustrates relief valve  10  in accordance with embodiments disclosed herein. The relief valve  10  is a spring-loaded poppet relief-type valve coupled to a vessel (not shown) such as a railroad tank car carrying commodities such as ethanol or crude oil. The relief valve  10  is designed to allow emptying of the vessel&#39;s contents when the vessel is involved in a situation (e.g., a fire) that may necessitate emptying most, if not all, contents of the vessel before failure of the container.  FIG. 1  illustrates relief valve  10  including a flange mount  15 , where relief valve  10  may be attached to an external portion of the vessel by inserting one or more bolts (not shown) through one or more bolt holes  15   a ,  15   b ,  15   c  in order to securely attach the flange mount  15  to the vessel. Additional bolt holes not specifically illustrated may be found around a circumference of flange mount  15 . 
     Valve bonnet  12  includes a top portion supporting a pin housing  50 , a plurality of leg portions, and a bottom portion securely attached to flange mount  15 . The bottom portion of valve bonnet  12  may be securely attached to flange mount  15  by one or more bolts  72   a ,  72   b  as illustrated in  FIG. 3 . Valve bonnet  12  provides support for relief valve  10  under pressure from, among other forces, a bias force from a bias member, and in this embodiment spring pressure from spring  30 , which is depicted as a nested spring assembly. 
     The relief valve  10  is designed to open at a preset pressure, such that when the pressure in the vessel exceeds the preset pressure of the relief valve  10 , the relief valve  10  will open to allow the pressure in the vessel to be reduced. The preset pressure can be adjusted using an adjusting screw  14  to adjust the spring retainer  16  enclosing the top of a spring  30  to translate up or down relative to a stem  40 . Adjusting the adjusting screw  14  causes the spring retainer  16  to translate up or down stem  40 , and a compression force of spring  30  may be controlled to achieve a specific compression force that corresponds to a desired preset pressure for the particular vessel and/or contents. For example, by turning adjusting screw  14  to translate spring retainer  16  further down stem  40 , spring  30  is further compressed resulting in an increased spring force of spring  30  which corresponds to a higher adjusted desired preset pressure. Conversely, by turning adjusting screw  14  to translate spring retainer  16  further up stem  40 , spring  30  is further decompressed resulting in a lower spring force of spring  30  which corresponds to a lowered adjusted desired preset pressure. When the pressure in the vessel exceeds the preset pressure, the force of the pressure in the vessel overcomes the spring force of spring  30 , allowing a poppet  24  coupled to a seat  26  to lift away from valve inlet  28 . Prior to the pressure within the vessel overcoming the spring force of spring  30 , seat  26  securely covers valve inlet  28  to prevent content inside the vessel from flowing out valve inlet  28 . With the movement of seat  26  lifting away from valve inlet  28 , an outlet opening is exposed thus allowing content from the vessel to flow out from valve inlet  28 . 
     Relief valve  10  provides an advantage of including a mechanism whereby when the pressure in the vessel exceeds the preset pressure, relief valve  10  opens to a full open position to allow pressure and/or content in the vessel to be release through valve inlet  28 . Relief valve  10  further remains held open at a pre-determined height using a locking assembly. As seen most clearly in  FIGS. 5-9 , stem  40  has a head portion  40   a  having an increased diameter and circumference compared to other portions of stem  40 , resulting in a pair of shoulders  43   a ,  43   b . A locking assembly comprises a pin housing  50  coupled to the top of the valve bonnet  12 . Pin housing  50  includes pin tracks  52   a ,  52   b , and pins  60   a ,  60   b  slidably coupled to pin housing  50 . Pin springs  62   a ,  62   b  are coupled to the pins  60   a ,  60   b  and to the pin housing  50  to bias pins  60   a ,  60   b  toward stem  40  and into a locked position. When relief valve  10  opens at the preset pressure, poppet  24  forces stem  40  upward. A poppet stem  29  engages poppet  24  to guide poppet  24  upwards. Support member  21  is included to provide guidance and support for poppet stem  29  as poppet stem  29  moves up and down. Substantial portions of poppet stem  29  and support member  21  reside within the vessel. 
       FIG. 6  depicts relief valve  10  including recesses  42   a ,  42   b  around portions of stem  40 , the head portion  40   a , and pin housing  50 . When stem  40  rises and recesses  42   a ,  42   b  align with pins  60   a ,  60   b , the bias of pin springs  62   a ,  62   b  forces pins  60   a ,  60   b  into recesses  42   a ,  42   b . An end portion of pins  60   a ,  60   b  will engage shoulders  43   a ,  43   b  through recesses  42   a ,  42   b  to lock stem  40  in place, thus preventing stem  40  from lowering to a position where seat  26  can reseal valve inlet  28 . 
     In an unlocked position ( FIG. 6 ), poppet  24  is in seat  26  and stem  40  is in the neutral position. Pins  60   a ,  60   b  cannot advance against impeding edges of stem  40  and pin springs  62   a ,  62   b  are in a compressed position when in the unlocked position. 
     In a locked position ( FIG. 7 ), the pressure of the system has overcome the spring force of spring  30 , and stem  40  is moved upward away from valve inlet  28  such that poppet  24  and seat  26  uncover valve inlet  28 . Recesses  42   a ,  42   b  align with pins  60   a ,  60   b , and a bias force from pin springs  62   a ,  62   b  push pins  60   a ,  60   b  into the recesses  42   a ,  42   b  to lock stem  40  in place. This locks relief valve  10  in an open position, with poppet  24  and seat  26  raised from the valve inlet  28  so as not to allow relief valve  10  to close beyond the height of recesses  42   a ,  42   b , thus allowing the contents to continue to flow out of the vessel. This means that relief valve  10  can continue to allow the contents of the vessel to be released from the vessel even though the pressure in the vessel has dropped below the preset pressure of relief valve  10 . The vessel may further be saved from rupturing due, at least in part, to the continued release of content from the vessel. This ability for relief valve  10  to continue releasing contents from the vessel below the preset pressure is especially important if the vessel has become comprised (e.g. on fire, or tipped on its side) so that the contents can be released before the vessel fails (e.g. metal fatigue) with contents remaining therein. 
     As seen in  FIG. 8 , relief valve  10  also provides a further advantage by allowing poppet  24  and seat  26  to rise up to a full open position height that is higher than a locked position height. The poppet  24  and seat  26  may rise to the full open position height when momentum from a pressure within the vessel overcoming the preset pressure forces poppet  24  and seat  26  to rise up to the full open position height. The full open position height is higher that the locked position height, where seat  26  is lifted higher off valve inlet  28  to create a larger outlet opening at the full open position height than compared to when seat  26  is lifted to the locked position height. This allows the contents of the vessel to flow out at a higher rate while the pressure within the vessel is able to maintain poppet  24  and seat  26  at a height above the locked position height for poppet  24  and seat  26 . This may allow for maximum flow capacity from the vessel upon the initial opening of relief valve  10 . In this case, locking pins  60   a ,  60   b  slip into recesses  42   a ,  42   b  but are below the restricting part of shoulders  43   a ,  43   b  created by head portion  40   a.    
     Then, as pressure decreases in the vessel, relief valve  10  returns to the locked open position ( FIG. 9 ) with shoulders  43   a ,  43   b  resting on locking pins  60   a ,  60   b  at the predetermined open height so that pressure can continue to flow out of the vessel and prevent rupturing of the vessel. 
     In some embodiments,  FIGS. 10 and 11  illustrate relief valve  10  including a release feature for releasing the locking mechanism of relief valve  10  in the event that it is determined relief valve  10  no longer needs to be held open because content from the vessel no longer needs, or is desired, to be emptied through relief valve  10  (e.g., the passing of a critical situation such as extinguishing a fire in the vessel). To reset relief valve  10  so that it can reseal valve inlet  28 , locking pins  60   a ,  60   b  are pulled back from the locked position ( FIG. 10 ). Linear force is applied to a reset plate  70  by a rod  72 . Once the force is applied to reset plate  70 , reset plate  70  contacts stops  74   a ,  74   b  that are coupled to locking pins  60   a ,  60   b . This results in pin springs  62   a ,  62   b  being compressed, and locking pins  60   a ,  60   b  are pulled back to the unlocked position to close relief valve  10  ( FIG. 11 ). Rod  72  may be pulled by any means of applying a liner force, for example a pneumatic piston or a brake cable-type assembly. This allows relief valve  10  to be reset from a remote location. Rod  72  could also have a manual pull to reset relief valve  10  locally. 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any equivalent thereof.