Abstract:
A shear protection device for use with a valve, the device comprising a poppet, the poppet including a bore. The poppet including first and second openings at distal ends of the poppet. A seat plug is disposed in the poppet bore, the seat plug is moveable within the poppet bore. A shear tube with first and second ends extending through the first opening of the poppet, the first end abutting the seat plug through the first opening of the poppet and the shear tube displacing the seat plug from the top of the poppet bore. The poppet is attachable to the valve and when attached a gas or liquid passes through the poppet into the valve. When the shear tube is removed, the seat plug forcibly engages the top of the poppet bore and the seat plug blocks the flow of the gas or liquid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the priority benefit of U.S. Provisional Applications for Patent Ser. No. ______, entitled “Poppet Shear Apparatus and System,” filed Apr. 24, 2003, by Steven K. Aderholt, Franklin B. Piehl and Dennis C. Hatfield which is hereby incorporated by reference for all purposes. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH/DEVELOPMENT  
         [0002]    Not Applicable  
         FIELD OF THE INVENTION  
         [0003]    The present invention relates generally to shear protection devices for tanks containing high-pressure gases. More specifically, the present invention relates to shear protection devices for truck-borne and stand-alone compressed gas cylinders.  
         BACKGROUND  
         [0004]    Various types of compressed gases are commonly transported in long, narrow cylinders, or “tubes,” mounted directly on a tractor trailer chassis or in a “module,” or a box frame containing the cylinders that is loaded onto a flat bed trailer. These truck-borne compressed gas cylinders are often required by law to be fitted with relief devices designed to relieve pressure from the compressed gas cylinders in the event of cylinder over-pressurization or fire. These relief devices are typically attached to each end of a cylinder and take two major forms: cluster-type relief devices (typically for hazardous gases) and angle-type relief devices (typically for non-hazardous gases). The relief devices typically protrude from the compressed gas cylinders and are subject to shearing forces. These relief devices provide protection for over pressurization, however, due to their physical structure, are prone to inadvertent damage such as having the relief device sheared off of the compressed gas cylinder. When such a shearing of a valve or relief device occurs, the compressed gas escapes through an uncontrolled opening in the compressed gas cylinder to the atmosphere.  
           [0005]    In U.S. Pat. No. 5,832,947, entitled “Gas Shut-Off and Pressure Relief Valve for a High Pressure Gas Vessel,” issued to Andrew Niemczyk, a pressure relief valve is disclosed. The disclosed pressure relief valve has a threaded body that engages the side port in fluid communication with the gas passage. The side port has a radially extending shoulder that seats an annular sealing ring. A rupture disc, made from brass, is pressed by the threaded body against the sealing ring. During operation, the gas shut-off and pressure relief valve extends away from the compressed gas cylinder. The relief valve provides protection from an unintentional over pressurization; however, the protrusion of the relief valve increases the probability of an inadvertent shear of the relief valve.  
           [0006]    In U.S. Pat. No. 4,269,214, entitled “Safety Pressure Relief Device,” issued to Calvin. C. Forsythe, et al., a safety pressure relief device is disclosed. The disclosed safety pressure relief device has a casing with a threaded connection and a concentric axial bore there through. The open end of the casing engages a concave-convex rupture disc which is ruptured with a knife means including a plurality of spaced cutting teeth. An annular outlet ring is connected to the casing by a continuous heli-arc weld. The weld also connects the rupture disc and the knife means to the casing. Again, protection is provided for an over pressurization. However, the probability of an inadvertent shear of the relief device is increased.  
           [0007]    [0007]FIG. 1 illustrates another prior art relief device and its attachment to a compressed gas cylinder. The relief device  20  does not attach directly to the cylinder  10 . Rather, the relief device  20  screws into a “bullplug”  30 , which itself screws into the cylinder  10 . Thus, the bullplug  30  has two sets of threads: a set of male straight threads  32  that engage a reciprocal female set  12  in the cylinder; and a set of female pipe threads  34  that engage a reciprocal set of male pipe threads  24  on the relief device  20 . Moreover, having the relief device  20  screw into the bullplug  30 , which in turn screws into the cylinder  10 , means that the relief device  20  protrudes farther from the cylinder  10  than it would if the relief device  20  screwed directly into the cylinder  10 . This greater protrusion presents a greater opportunity for a shear of the relief device  20  from the cylinder  10  in the event of an accident, resulting in uncontrolled compressed gas leakage.  
           [0008]    Therefore, a need exists for a shear protection device that couples directly to its associated compressed gas tank utilizing a valve or relief device, thereby lessening the likelihood of a valve or relief device shear—and the associated uncontrolled leakage—in the event of an accident.  
           [0009]    Accordingly, it is an object of the present invention to provide a shear protection device for compressed gas cylinders that attaches directly to its cylinder. It is a further object of this invention to provide a shear protection device that attaches directly to relief devices for compressed gas cylinders that reduces or eliminates the likelihood of the uncontrolled compressed gas leakage due to the valve or relief device shearing away from the main body in the event of an accident.  
         SUMMARY  
         [0010]    The present invention is a shear protection device including a poppet, a seat plug and a retainer plug. The poppet is substantially a tube with a bore and with downstream and upstream openings where the diameter of the upstream opening in larger than the diameter of the seat plug and the diameter of the downstream opening is smaller than the diameter of the seat plug. The poppet further includes ventilation openings around the circumference of the poppet. The ventilation openings allowing a gas or liquid to pass through the poppet into the bore for passage to a valve.  
           [0011]    A seat plug is inserted through the upstream end of the poppet and moves within the poppet bore. A retainer plug is attached at the upstream end of the poppet, substantially closing off the upstream opening and blocking the exit of the seat plug through the upstream opening. The retainer plug includes an opening to allow for the gas or liquid to forcibly abut the seat plug.  
           [0012]    A valve with a threaded attachment is also shown. The valve includes an inlet. A shear tube is attached within the inlet of the valve. The poppet is attached to the valve inlet so that the upstream opening is inserted into the inlet of the valve. When the poppet is attached, the shear tube forcibly engages the seat plug causing the seat plug to engage the retaining plug. When the seat plug is engaging the retaining plug, the liquid or gas can pass through the ventilation openings of the poppet and pass through the valve inlet.  
           [0013]    If the valve is sheared away, the internal force of the compressed gas or liquid forces the seat plug away from the retainer plug towards the downstream opening. The seat plug then engages the top of the bore of the poppet, blocking the passage of the gas or liquid through the ventilation openings through the valve inlet.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    For a more complete understanding of the present invention, and for further details and advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the following drawings, in which:  
         [0015]    [0015]FIG. 1 is an exploded view of a prior art angle-type relief device&#39;s interaction with its associated compressed gas cylinder;  
         [0016]    [0016]FIG. 2 a  is a side view of a valve and a shear protection device according to one embodiment of the present invention;  
         [0017]    [0017]FIG. 2 b  is an exploded side view of a valve and a shear protection device according to one embodiment of the present invention;  
         [0018]    [0018]FIG. 2 c  is a top view of a retainer plug of the shear protection device according to one embodiment of the present invention;  
         [0019]    [0019]FIG. 2 d  is a bottom view of a retainer plug of the shear protection device according to one embodiment of the present invention;  
         [0020]    [0020]FIG. 2 e  is a top view of a seat plug of the shear protection device according to one embodiment of the present invention;  
         [0021]    [0021]FIG. 2 f  is a bottom view of a seat plug of the shear protection device according to one embodiment of the present invention;  
         [0022]    [0022]FIG. 2 g  is a top view of a poppet of the shear protection device according to one embodiment of the present invention;  
         [0023]    [0023]FIG. 2 h  is a bottom view of a poppet of the shear protection device according to one embodiment of the present invention;  
         [0024]    [0024]FIG. 3 is an exploded view of a valve and a shear protection device&#39;s interaction with a compressed gas cylinder according to one embodiment of the present invention;  
         [0025]    [0025]FIG. 4 is an exploded view of a valve and two shear protection device&#39;s interaction with a compressed gas cylinder according to another embodiment of the present invention;  
         [0026]    [0026]FIG. 5 a  is a side view of an alternate valve and a shear protection device according to another embodiment of the present invention;  
         [0027]    [0027]FIG. 5 b  is an exploded side view of an alternate valve and a shear protection device according to another embodiment of the present invention;  
         [0028]    [0028]FIG. 6 a  is a side view of an alternate valve and a shear protection device according to another embodiment of the present invention;  
         [0029]    [0029]FIG. 6 b  is an exploded side view of an alternate valve and a shear protection device according to another embodiment of the present invention;  
         [0030]    [0030]FIG. 7 is an exploded view of a valve and a shear protection device&#39;s interaction with a compressed gas cylinder according to another embodiment of the present invention; and  
         [0031]    [0031]FIG. 8 is an exploded view of a valve and a shear protection device&#39;s interaction with a compressed gas cylinder after shearing according to another embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    In the descriptions which follow, like parts are marked throughout the specification and drawings with the same numerals, respectively. The drawing figures are not necessarily drawn to scale and certain figures may be shown in exaggerated or generalized form in the interest of clarity and conciseness.  
         [0033]    The present invention comprises generally a shear protection device, a valve, a threaded connection for coupling the shear protection device and valve to a compressed gas cylinder, and a seat plug that seals the cylinder outlet in the event of shearing of the valve. This disclosure describes numerous specific details that include specific structures, their arrangement, and functions in order to provide a thorough understanding of the present invention. One skilled in the art will appreciate that one may practice the present invention without these specific details.  
         [0034]    An improved valve and shear protection device for high pressure gas cylinders directly engage the cylinder. A bore within the poppet of the shear protection device is in fluid communication with the cylinder contents. When shearing of the valve occurs, a seat plug disposed in the poppet seals the bore preventing the uncontrolled escape and possible ignition of the cylinder contents.  
         [0035]    Referring now to the figures, FIGS. 2 a ,  2   b ,  2   c ,  2   d ,  2   e ,  2   f ,  2   g ,  2   h  and  3  are exploded, side, top and bottom views of a valve and shear protection device and the interaction of same with a compressed gas cylinder according to one embodiment of the present invention. As shown in FIGS. 2 a ,  2   b  and  3 , a bullplug  300  attaches to a cylinder  10 . In one disclosed embodiment, the bullplug  300  includes male straight threads  301  that screw directly into the reciprocal female straight threads  11  of a compressed gas cylinder  10 . An “O” ring (typically made of rubber) and a backup ring (typically made of a synthetic, fluorine-containing resin such as TEFLON) (neither shown) create a seal between the bullplug  300  and the cylinder  10 . The bullplug  300  includes a bore  302  which is in fluid communication with the contents of the cylinder  10 . A valve  103  and a shear protection device  101  attach to form a valve and shear protection device  100  which attaches onto the downstream side of bullplug  300 , allowing the operator to manually control gas or liquid flow from the cylinder  10 . In one disclosed embodiment, the bullplug  300  includes female straight threads  304  on the downstream side that screw directly onto reciprocal male straight threads  130  of the valve and shear protection device  100 . However, a variety of various attachment techniques are available without detracting from the spirit of the invention.  
         [0036]    As is shown in FIGS. 2 a ,  2   b ,  2   c ,  2   d ,  2   e ,  2   f ,  2   g  and  2   h , the valve and shear protection device  100  is formed from a valve  103  and a shear protection device  101 . The shear protection device  101  includes a shear tube  109 , a poppet  112 , a seat plug  118  and a retainer plug  124 . The valve  103  allows for the controlled escape of the contents of the cylinder  10 . The valve  103  includes a handle  102  for opening and closing of the valve  103 . When the valve  103  is in the open position, exit bore  104 , which is substantially perpendicular to the main axis of the valve  103 , is in fluid communication with inlet bore  106 , which is concentric with the main axis, allowing a gas or liquid to pass through the valve  103 . When the valve  103  is in the closed position, the fluid communication between the exit bore  104  and the inlet bore  106  is interrupted, preventing the gas or fluid from passing from the inlet bore  104  to the exit bore  106 . The valve  103  includes male straight threads  130  which mate the valve  103  to the bullplug  300 . In another disclosed embodiment, the valve  103  includes male tapered threads  130 . The valve  103  further includes female straight threads  160  tapped to the inlet bore  106 . The female straight threads  160  accept male straight threads  132  of the shear protection device  101 .  
         [0037]    The inlet bore  106  is bored to multiple different diameters: The first inner, smaller diameter portion of the inlet bore  106  is in fluid communication the second inner, larger diameter portion of the inlet bore  106 . The first inner diameter portion and the second inner diameter portion of the inlet bore  106  form a flat annular surface  111  at the transition between the first and second diameter bores. The second inner, larger diameter portion of the inlet bore  106  accepts the shear tube  109  and the shear tube  109  attaches to the flat annular surface  111 .  
         [0038]    The shear tube  109  includes a shear tube bore  108  which is in fluid communication with the inlet bore  106 . The shear tube  109  has a first outer diameter and a second outer diameter. The first outer diameter is substantial equal to the second inner, larger diameter of the inlet bore  106 . The second diameter of the shear tube  109  is smaller than the first diameter. The first diameter of the shear tube  109  forms a continuous flange  133  around the periphery of the shear tube  109 . When the shear tube  109  is installed in the inlet bore  106 , the continuous flange  133  abuts the flat annular surface  111  of the valve  103 . In one disclosed embodiment, the shear tube continuous flange  133  is press fit to the inlet bore  106 , abutting the flat annular surface  111 . When installed, the shear tube  109  extends beyond the body of the valve  103  into the poppet bore  114  providing fluid communication for poppet bore  114  with shear tube bore  108  which remains in fluid communication with inlet bore  106 . Shear tube bore  108  and inlet bore  106  have substantially equal inner diameters. In one disclosed embodiment, the shear tube  109  is formed from brass, however, a wide variety of materials may be used to form the shear tube without detracting from the spirit of the invention, including but not limited to stainless steel.  
         [0039]    The poppet  112  is substantially tubular and includes male straight threads  132  extended from the downstream end of the poppet  112 . The poppet  112  includes a poppet bore  114  through the main axis of the poppet  112 . The male straight threads  132  mate the poppet  112  to the female straight threads  160  of the valve  103 . When the poppet  112  and the valve  103  are mated, the shear tube  109  extends from the inlet bore  106  to within the downstream end of the poppet bore  114 . A seal gasket  110  is positioned between the valve  103  and the poppet  112  and seals the threaded connection to prevent leakage of the gas or liquid.  
         [0040]    The poppet bore  114  is bored to three different diameters. The first inner poppet diameter portion is bored to a diameter larger than the diameter of the shear tube  109  and forms a first inner poppet wall  154 . An intermediate inner poppet diameter portion is bored to a diameter larger than the first inner poppet diameter, but smaller than a third inner poppet diameter and forms an intermediate inner poppet wall  152 . The third inner poppet diameter portion is bored to a diameter substantially equal to the diameter of the retainer plug  124  and forms a third inner poppet wall  150 . The width of the shell of the first inner poppet diameter portion, including the male straight threads  132 , corresponds to the width of the female straight threads  160  of the valve  103 . The remaining outer poppet diameter portion is substantially equal to the outer diameter of the upstream end of the valve  103  where the valve  103  and poppet  112  mate.  
         [0041]    The first inner poppet diameter portion and the intermediate inner poppet diameter have a tapered connection. The intermediate inner poppet diameter portion and the third inner poppet diameter portion for an annular surface which is expanded radially to form a groove within the poppet bore  114  with a diameter greater than the third inner poppet diameter and the intermediate inner poppet diameter. The groove accepts an O-ring seal  116 , where the inner diameter of the O-ring seal is smaller than the third inner poppet diameter and the intermediate inner poppet diameter.  
         [0042]    The poppet  112  includes ventilation passages  128  which extend through the main body of the poppet  112  and form a substantial ring around the circumference. In one disclosed embodiment, the ventilation passages  128  exist in pairs on opposed sides of the poppet  112 . In another disclosed embodiment, multiple sets of ventilation passages  128  are provided in the poppet  112 . The ventilation passages  128  are in fluid communication with the poppet bore  114 . The poppet  112  further includes female straight threads  148  at the upstream end. The female straight threads  148  accept male straight threads  125  of the retainer plug  124 . In one disclosed embodiment, the poppet is formed from stainless steel, however, a wide variety of materials may be used to form the poppet without detracting from the spirit of the invention, including but not limited to brass.  
         [0043]    The retainer plug  124  includes a bore  126  and pressure cavities  134 . The bore  126  extends through the main axis of the retainer plug  124  while the pressure cavities  134  extend partially through the retainer plug. The pressure cavities  134  extend from the upstream end of the retainer plug  124 , the end closest to the cylinder  10 , but do not extend through to the downstream end. A tightening tool (not shown) may be inserted into the pressure cavities to assist in inserting the retainer plug  124  into the poppet  112 . The outer shell of the retainer plug  124  is formed by the male straight threads  125  which mate the retainer plug  124  to the poppet  112 . A flange  136  extends across the diameter of the downstream end of the retainer plug  124  and is perpendicular to the axis of the bore  126  which passes through the flange  136 . The flange  136  interacts with notch  138  of the seat plug  118 . In one disclosed embodiment, the retainer plug  124  is formed from brass, however, a wide variety of materials may be used to form the retainer plug  124  without detracting from the spirit of the invention, including but not limited to stainless steel.  
         [0044]    The seat plug  118  includes a base portion  137  and a tube portion  139 . The upstream end of the base portion  137  forms a notch  138  which interacts with the flange  136 . The base portion  137  diameter is smaller than the third inner poppet diameter and the retainer plug  124  diameter. The base portion  137  does not include a bore. The base portion  137  is fixedly attached to, or formed as a single unit with, the tube portion  139  forming a tapered connection.  
         [0045]    The tube portion  139  includes a seat plug bore  120  which is bored to a diameter substantially equal to the shear tube bore  108  diameter. The tube portion  139  includes two outer diameters  146 ,  142  respectively, with a tapered connection. At the downstream end of the seat plug  118 , the first outer diameter  146  is substantially equal to the diameter of the shear tube  109 , which is smaller than the first inner poppet diameter. The second outer diameter  142  has a tapered connection to the first outer diameter  146  and is smaller than the intermediate inner poppet diameter and is larger than the first inner poppet diameter. The tapered connection of the tube portion  109  is substantially equal to in length and pitch to the tapered connection between the first inner poppet diameter portion and the intermediate inner poppet diameter portion tapered connection.  
         [0046]    The tube portion  139  includes ventilation passages  122  which extend through the tube portion  139  of the seat plug  118  and form a substantial ring around the circumference. In one disclosed embodiment, the ventilation passages  122  exist in pairs on opposed sides of the seat plug  118 . In another disclosed embodiment, multiple sets of ventilation passages  122  are provided in the seat plug  118 . The ventilation passages  122  are in fluid communication with the seat plug bore  120 , the poppet bore  114  and the shear tube bore  108 . In one disclosed embodiment, the ventilation passages  122  and  128  are correlated such that equivalent pairs of ventilation passages  122  and  128  are aligned on the same axis. In one disclosed embodiment, the diameters of the ventilation passages  122  and  128  are substantially equal.  
         [0047]    When the valve  103  and the shear protection device  101  are attached to form the valve and shear protection device  100 , gas or liquid passes through the valve and shear protection device  100  through manual control. When the valve and shear protection device is assembled, the shear tube  109  is fixedly attached to the valve  103  at annular surface  111 . The shear tube  109  extends beyond the valve  103  into the poppet bore  114 . The seat plug  118  is loosely disposed in the poppet bore  114  and is enclosed at the upstream end by the threaded attachment of the retainer plug  124  to the poppet  112 . The poppet  112  is threadedly attached to the valve  103  at the poppet&#39;s  112  downstream end.  
         [0048]    In this configuration, the upstream end of the shear tube  109  abuts the downstream end of the seat plug  118 , forcing the seat plug  118  to abut the retainer plug  124  and inserts flange  136  into notch  138 . The ventilation passages  128  of the poppet  112  and the ventilation passages  122  of the seat plug  118  align and allow fluid communication of the gas or liquid in the cylinder  10  with the seat plug bore  120  and the shear tube bore  108 . In one disclosed embodiment, the ventilation passages of the poppet  112  and the ventilation passages  122  of the seat plug  118  do not align. Fluid communication of the gas or liquid in the cylinder  10  with the seat plug bore  120  and the shear tube bore  108  is accomplished as the poppet bore  114  is intermediate to the seat plug bore  120  and the shear tube bore  108  and is in fluid communication with both.  
         [0049]    The gas or liquid in the cylinder  10  places a force directed downstream on the upstream end of the seat plug  118 . The gas or liquid of the cylinder  10  passes through the retainer plug bore  126  and abuts the upstream end of the seat plug  118 . However, the seat plug  118  remains abutted to the retainer plug  124  as a result of the shear tube  109  abutting the downstream end of the seat plug  118 . The upstream force of the shear tube  109  is greater than the downstream force of the gas or liquid in the cylinder  10 .  
         [0050]    In the event of a shearing of the valve  103  of the valve and shear protection device  100 , the shear tube  109  is removed as an upstream force. The downstream force of the gas or liquid moves the seat plug  118  from abutting the retainer plug  124  to abutting the downstream end of the poppet bore  114 . The base portion  137  engages the O-ring  116  located in the poppet bore  114  and forms a barrier. The gas or liquid entering the poppet bore  114  either through the ventilation passages  128  or through the retainer plug bore  126  abuts the downstream end of the seat plug  118 . The ventilation passages  122  of the seat plug  118  are no longer in fluid communication with the gas or liquid. The internal pressure of the gas or liquid maintains pressure on the seat plug  118  thereby forming a seal between the seat plug  118  and the poppet  112  and the O-ring  116 .  
         [0051]    Referring now to FIGS. 4, 5 a  and  5   b , a valve with two shear protection devices is shown. A valve and shear protection device  100  attaches to a relief device  400 . The valve and shear protection device  100  is substantially the same as disclosed above. The male straight (or tapered) threads  130  mate with the female straight (or tapered) threads  402  of the relief device  400 . In one disclosed embodiment, the relief device is an angle-type relief device for truck-borne high pressure gas cylinders. Examples of such an angle-type relief device are shown in U.S. patent application Ser. No. 10/141,413 entitled “Method And Apparatus For Orbital And Seal Welded Relief Device On A Compressed Gas Cylinder,” filed on May 8, 2002 by Steven K. Aderholt, Franklin B. Piehl and Dennis C. Hatfield which is hereby incorporated by reference for all purposes. The valve and shear protection device  100  is inserted into bore  402  at the downstream end of the relief device  400 . A secondary bore  406  is in fluid communication with bore  402  and is perpendicular to bore  402  and the main axis of the relief device  400 . At the upstream end of the relief device, a shear protection device  101  is attached, providing fluid communication of the shear protection device  100  with the inlet bore  408 , the secondary bore  406  and the bore  402 . The relief device  400  and the attached shear protection device  101  are attached to the cylinder  10 . Male straight (or tapered) threads  401  mate with the female straight (or tapered) threads  304  of the bullplug  300  which is attached to the cylinder  10 .  
         [0052]    The relief device  400  includes a valve body  424  and a washer  422 , rupture disc  420 , shear ring  418 , adapter  416 , membrane  414 , and flare nut  412 . The valve body  424  includes a main body coaxial with the cylinder  10  and an integral riser portion  425  having an axis perpendicular to the main axis and the cylinder axis. The operation of the angle-type relief device  400  operate to relieve pressure if an over pressurization occurs.  
         [0053]    The riser portion  425  of the valve body  424  protrudes beyond the outer diameter of the main body  423 . This presents yet another opportunity for shear in the event of an accident, in this case the shear of the riser and the valve body  424  shear from the cylinder  10 . The relief device  400  and the shear protection device  101  function as previously described. If the relief device  400  shears, the shear protection device  101  attached to the upstream end of the relief device  400  blocks the flow of the gas or liquid. If the valve and shear protection device  100  shear, the downstream shear protection device  101  prevent the flow of the gas or liquid.  
         [0054]    Referring now to FIGS. 6 a ,  6   b  and  7  an alternate valve and shear protection device are shown. A valve  600  is shown attached to the shear protection device  101 . The valve  600  includes two outlet bores  604  and  606 . The outlet bores  604  and  606  are in fluid communication with inlet bore  608 . The shear protection device  101  attaches to the valve  600  through male straight threads  132  and female straight threads  611 . The shear protection device  101  includes the shear tube  109 , the seal gasket  110 , the poppet  112 , the O-ring  116 , the seat plug  118  and the retainer plug  124 . In this embodiment, the larger diameter of the valve  600  male straight (or tapered) threads  610  allow for direct mating with the cylinder  10  without the need of an intermediary bullplug (not shown). The male straight (or tapered) threads  610  mate with the female straight (or tapered) threads  700  located in cylinder bore  702 . The shear protection device&#39;s  101  diameter increase is proportional to the increase in the diameter of the valve  600  male straight (or tapered) threads  610 . However, the diameter of the shear protection device  101  may vary without detracting from the spirit of the invention. The shearing protection function occurs as disclosed above if the valve  600  is sheared from the cylinder  10 .  
         [0055]    Referring now to FIG. 8, an exploded view of a sheared valve and shear protection device is shown. The valve  600  is sheared  800  from the cylinder  10 . When the valve  600  is sheared, the upstream force on the seat plug  118  from the shear tube  109  is removed and the seat plug is forced downstream by the internal force of the gas or liquid in the cylinder  10 . The seat plug  118  engages the O-ring  116  and forms a barrier to stop the escape of the gas or liquid. Barrier space  802  is formed between the upstream end of the seat plug  118  and the retainer plug  124 . As the ventilation passages  122  are moved downstream, the cylinder  10  contents are no longer in fluid communication with the seat plug bore  120 .  
         [0056]    Other embodiments of the invention will be apparent to those skilled in the art after considering this specification or practicing the disclosed invention. The specification and examples above are exemplary only, with the true scope of the invention being indicated by the following claims.