Abstract:
A valve, such as a liquid level sight glass gage valve, has a valve unit and a passageway that extends through the valve unit. The passageway has a stem receiving area, a seal receiving area, and a bonnet receiving area that has a non-circular inner perimeter. A packing assembly is provided to isolate the bonnet receiving area from the fluid path. A bonnet is located within the bonnet receiving areas and has a non-circular outside surface for mating relationship with the non-circular inner perimeter of the valve unit. A valve stem is in sealing relationship with the packing assembly and selectively engages a valve seat. The stem threadably engages the bonnet. A bonnet nut is threadably received on the valve unit for securing the bonnet within the valve unit and allowing axial movement of the bonnet against the packing assembly, thereby effecting compression of the packing.

Description:
FIELD OF THE INVENTION 
   The present invention is directed toward a valve. More particularly, but not by way of limitation, the present invention is directed towards an improved valve that resists freeze up due to internal corrosion or fouling of the valve mechanism. 
   BACKGROUND OF THE INVENTION 
   Sight glass liquid level gages have a vertical window that allows the level of a liquid in a vessel to be determined. Level gages are selectively isolated from vessel contents by valves to enable removal of a level gage for cleaning or repair without dumping the contents of the vessel. Liquid level gage valves are used in pairs, one on each end of a level gage. Typically, liquid level gage valves have a safety ball check that functions to quickly seat and prevent the vessel from emptying in the event of a break of the gage glass. Gage glass breakage will result in a sudden drop in pressure across the gage valve, which seats the safety ball. The valve may then be manually closed and the gage repaired. In a typical gage valve, closing of the valve causes a small extension on the bottom end of the stem to dislodge the seated check ball from the seat, thereby reestablishing communication between the vessel and the gage. The valve may then be fully opened to its normal position. Another feature common to liquid level gage valves is an offset of the gage connection. The offset feature facilitates cleaning of the gage glass by allowing a brush or swab to pass through the valve body and into the gage glass chamber once the vent and drain plugs are removed. 
   A problem common to standard valves is the fact that internals of the valves are in constant contact with the liquid of the vessel. The liquid can be very corrosive and may contain suspended particles. Since the valves are normally open, swelling associated with corrosion and/or suspended particles tend to collect and pack in the stem thread area, which can cause the valve to “freeze up” and become impossible to close. 
   Attempts have been made to overcome stem thread area corrosion issues, such as locating valve packing at a place between the liquid and the threads so that the threads are located on the exterior of the valve. An example is an OS &amp; Y valve, the letter designation standing for outside screw and yoke. However, such solutions have created additional problems by exposing the stem threads to the surrounding environment, which can be problematic. For example, an inadvertent blow to the stem can cause bruising or bending of the stem, making the valve difficult or impossible to close. Additionally, dirt and other debris are attracted to lubricants that are used on the threads and this may result in difficulty operating the valve. Furthermore an OS &amp; Y valve usually employs a bolted bonnet that must attach and seal to the body. The bolted bonnet requires an additional seal, which adds to manufacturing and maintenance costs. 
   Some instrument needle valves use the stem packing to isolate the stem threads from the internal fluid with an inside screw (instead of an outside screw) whereby the stem threads are located internal to the valve body. These valves employ a dual acting bonnet, which is threaded internally to accept the valve stem. Also, the bonnet may be axially adjusted to compress a packing ring. A drawback associated with such needle valves is that the needle valves employ a bonnet that is threaded externally to fit internal threads in the valve body. A locking mechanism, usually a jam nut, must be used to lock the bonnet into a fixed position with respect to the valve body after an adjustment to the compression packing has been made. Therefore, to tighten the packing, an operator must first loosen the jam nut. The loosening of the jam nut may not be obvious to an operator who normally tightens the packing on a leaking valve by one action only, i.e., tightening a packing nut. The non-intuitive aspect of first being required to loosen part of the valve before compressing of the packing is a disadvantage associated with this valve. 
   Another design weakness associated with using a rotating bonnet on a needle valve is revealed when a jam nut is left in a loosened condition, e.g., after a tightening sequence on the packing is performed. If the jam nut is left loose, then the next time an operator begins to unscrew the valve into a fully open position, a major diameter or flange that creates the back seat of the stem will rotate backwards until it bears against the inboard end of the bonnet. At this point, further backward rotation of the stem will cause the bonnet to unscrew from the valve body, which results in a possibly dangerous scenario that should be avoided. For this reason it is common to use a staking device or a secondary locking device to restrain movement of the bonnet. Use of a staking device or a secondary locking device is inconvenient because the device must first be removed before the packing can be tightened. Once such a device is removed the manufacturer has no assurance that it will be replaced. 
   Finally, another way to accomplish an isolation of the stem threads from fluid is to provide an O-ring seal between the diameter of the stem and the seal receiving area of the body. By using an O-ring around the stem instead of compression packing, the design may be greatly simplified because it is not necessary to provide a means of compressing the packing below the stem threads. However, this valve design is only as good as the seal. In a dirty fluid environment, such as oil and gas production, it is likely that a soft seal such as an elastomeric O-ring may become damaged by sharp angled debris such as rust, scale and sand. Axial and rotational movement of the stem as it travels between an open and closed position may pick up contaminants and drag them across the seal, causing cuts to the O-ring and consequent leakage. 
   In operation a certain amount of torque is required to turn a valve stem. The required torque creates the “feel” that a user experiences when opening or closing the hand wheel of the valve. Resistance to turning is caused by friction between the seal and the stem, by friction of the mating threads, and by hydraulic force internal to the valve body that acts against the stem. 
   If the valve utilizes an O-ring seal, then frictional resistance caused by the seal is typically low. If the valve utilizes compression packing for the seal then the seal friction is much greater and varies in proportion to the load imposed by a packing or stuffingbox nut. Some packing materials, such as Teflon®, will seal against the valve stem with relatively low loads but other materials, such as flexible graphite, require more significant stuffingbox loads. 
   As the valve stem advances into the valve body from an open position to a closed position, the stem rotates and travels axially through the seal area. The axial movement of the valve stem is resisted by internal hydraulic forces inside of the valve body. The force required to advance the stem is equal to the cross sectional area of the stem in the region of the packing run multiplied by the pressure. Thus, it can be seen that the force required to advance the stem against pressure can be lowered by making the seal diameter of the stem smaller for a given pressure condition. Therefore, it is advantageous to make the seal diameter of the stem as small as practical. 
   The valve stem has a threaded portion. The screw threads on the stem form an inclined plane and offer a mechanical advantage to overcoming the hydraulic force internal to the valve. A larger screw thread diameter produces a lower helix angle and therefore confers more advantage than a smaller thread diameter. 
   In a conventional valve the area of the stem between the threads and the hand wheel contains the stem seal. The area of the stem between the threads and the handwheel usually extends some distance past the outside of the packing or stuffingbox nut before it terminates at the hand wheel. The portion of the stem extending past the outside of the packing nut allows the handwheel to be separated from the rest of the valve, which permits the operator to grasp the hand wheel and turn it without scraping his knuckles on the valve body or adjacent piping. In the case of a gage valve of the type typically used with a liquid level gage, the hand wheel might be positioned not only over the valve body but also over a portion of the level gage. The handwheel should be positioned far enough from the valve to avoid interference between the hand wheel and the level gage. Thus, there must be sufficient extension of the stem to allow adequate clearance between the hand wheel and the valve for manual operation of the hand wheel. A second reason for an extended stem is to allow for placement of thermal insulation directly over the valve and still allow for operation of the hand wheel. 
   Since the extended stem is subject to damage, a manufacturer typically makes the stem of sufficient diameter to resist bending if the valve is dropped during installation or bumped sideways on the hand wheel during shipping, installation or operation. Additionally, a valve will sometimes “freeze” into position after a period of inactivity. A frozen valve often requires turning with a valve wrench. The valve wrench can impose severe torque on the hand wheel. If the stem diameter is too small then it can be twisted apart. 
   SUMMARY OF THE INVENTION 
   It is desirable to provide a valve that protects the threads of the valve stem from the corrosive effects of vessel fluids and that protects the valve stem from potential damage. By locating the valve stem packing between the liquid in a valve unit and the stem operating threads, problems associated with corrosion swelling and the collection of suspended particles on the operating threads are eliminated. For purposes of this application, “valve unit” shall be used to refer to a valve assembly, which may be of a unitary body design or may be of multi-piece construction, e.g. a valve body and an attachment, or other variations, including in-line, straight pattern configuration, and angled valve configurations. 
   A seal located at the end of the bonnet prevents outside contamination from entering the operating thread area. The seal also may contain lubricant necessary for the operation of the close fitted thread. The valve of the invention has the operating threads and a large percentage of the stem confined in the valve unit, thereby eliminating the yoke. Additionally, the valve of the invention has a dual acting bonnet. The bonnet not only carries the stem but also provides a means of selectively compressing the packing by axial forces. 
   More particularly, the valve of the invention includes a valve unit having a first end and a second end. A passageway extends from the first end to the second end of the valve unit. The passageway has a stem receiving area, a seal receiving area, a first bonnet receiving area and a second bonnet receiving area. The second bonnet receiving area has a non-circular inner perimeter. One or more outlet passageways are in communication with the passageway. A packing member is located in the seal receiving area of the passageway. 
   A bonnet is located within the bonnet receiving area of the body. The bonnet has a first end and a second end and a non-circular external area proximate the first end of the bonnet for mating relationship with the second bonnet receiving area of the body. The mating non-circular areas of the bonnet and of the interior surface of the body facilitate a non-rotating connection. The bonnet is dual acting. The bonnet is threaded internally to accept a stem. The bonnet also slides axially in the valve body as the bonnet nut is tightened. The sliding movement allows the end face of the bonnet to bear against a packing member or a packing follower, thus accomplishing compression of the packing. As the stem is turned the bonnet is prevented from turning with it by the non-circular fit between the bonnet and the valve body. The bonnet may thus be described as non-rotating and dual acting. 
   A valve stem is located in the passageway in sealing relationship with the packing member. The valve stem is threadably engaged with the bonnet. A bonnet nut is threadably received on external threads on the second end of the body. The bonnet nut is for securing the bonnet in the body. 
   A valve stem having an optimal design has a relatively small sealing diameter while the thread diameter and the extension diameter adjacent to the hand wheel are relatively large. In the case of a conventional valve a packing run is located within the extension area, i.e., between the threads and the hand wheel. Therefore, a desire for a small sealing diameter and a large extension diameter are contradictory. 
   The present invention moves the packing run area of the stem to the opposite side of the threads, thus separating the stem into three different physical areas, i.e., an extension section, a threaded section and a sealing section. The present invention allows for the thread diameter and the extension diameter to be large while making the sealing diameter small. In the valve of the invention, the sealing diameter can be minimized to the point that it just exceeds the valve seat and maintains its function as a closing device. 
   One unexpected benefit associated with the new design is free turning action of the stem. As compared to conventional valves, the new valve turns much more freely, both at atmospheric condition and under pressure. The free turning action is believed to result from a relatively small diameter of the valve stem where the valve stem passes through the compression packing ring as compared to the diameter of the valve stem at this location in a conventional valve. 
   As the sealing diameter of a piston increases it takes a greater and greater force to drive it against pressure. In the present invention, the sealing diameter of the stem is in a section below the threads. Therefore, the sealing diameter of the stem may be minimized. A minimum sealing diameter of the stem is limited only by the need to seal against the seat. For example, a typical seat diameter for an instrument valve is ⅜″. As an example, the sealing diameter of the stem in the valve of the invention may be 7/16″, which is the minimum size required to seal over a ⅜″ orifice. In contrast, the sealing diameter of the stem of a conventional valve is ⅝″. The force required to drive a piston against pressure goes up in proportion to the cross sectional area of the piston, or by the diameter squared. Therefore, the valve of the invention requires a lower force to turn the stem against pressure by (0.437/0.625)^2 or about 50%. 
   The extension diameter of the stem, which is on the opposite side of the screw threads from the sealing portion of the stem, remains at  ⅝″ in the preferred embodiment. A   ⅝″ diameter is large enough to resist inadvertent twisting or bending of the stem. The screw thread diameter preferably remains relatively large to maintain a favorable helix angle.    
   One advantage of the valve of the present invention is that the packing area of the valve is moved from the outboard end of the stem to the inboard end of the stem. The unique placement of the packing area is accomplished by utilizing a dual acting, non-rotating bonnet. The use of a dual acting, non-rotating bonnet accomplishes a separation between possibly harmful fluids in the valve and the screw threads. Separation between the fluid and screw threads is desirable because the screw threads are susceptible to fouling and corrosion, which may render the valve inoperable. 
   While the invention is described primarily with respect to liquid level gage valves having an inlet passageway and an outlet passageway offset by 90°, and the like, it should be understood that the invention is equally applicable to other types of valves including, for example, in-line valves, and valves having parallel but axially offset inlet and outlet passageways. 
   Further objects, features, and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of the valve of the invention used as a liquid level sight glass gauge valve. 
       FIG. 2  is an end view of a first embodiment of the valve of the invention, showing the valve body only. 
       FIG. 3  is an assembly cross-sectional view of the first embodiment of an angle valve shown in  FIG. 2 , taken along line  3 — 3  of  FIG. 2 . 
       FIG. 4  is an end view of a second embodiment of an angle valve of the invention, showing the valve body only. 
       FIG. 5  is an assembly cross-sectional view of the valve shown in  FIG. 4 , taken along line  5 — 5  of  FIG. 4 . 
       FIG. 6   a  is a cross-sectional view taken along line  6 — 6  of  FIG. 5 . 
       FIG. 6   b  is a cross-sectional view of an alternate embodiment of the valve. 
       FIG. 7  is an assembly cross-sectional view of an straight pattern valve configuration of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIGS. 1–5 , shown is a valve designated generally  10 . Referring in particular to  FIGS. 2 and 3 , a first embodiment  11  of valve  10  is shown. Valve  11  has a body  12  having a first end  14  and a second end  16 . Body  12  comprises valve unit  13 . First end  14  has external threads  18  formed thereon. External threads  18  preferably receive a union nut  20  that secures the body  12  to a vessel, e.g. vessel  15  ( FIG. 1 ) by engaging a floating shank  22  ( FIG. 3 ). Second end  16  of body  12  preferably has external threads  24  for receiving a bonnet nut  26 . 
   Referring now primarily to  FIG. 3 , body  12  has a passageway  28  formed therein. Passageway  28  extends from first end  14  to second end  16  of body  12 . First end  14  of passageway  28  is preferably the valve inlet. Passageway  28  defines a check ball chamber  30  in having a first end  32  and a second end  34 . First end  32  of check ball chamber  30  communicates with first end  14  of body  12 . Check ball chamber  30  preferably has a tapered check ball seat  36  at the second end  34  of the check ball chamber  30 . 
   A restricted area  38  is located adjacent to check ball chamber  30 . Restricted area  38  has a first end in communication with the seat  36  of the check ball chamber  30 . Restricted area  38  additionally has a second end defining a sealing surface or seat  44 . A stem receiving bore  46  is located adjacent to restricted area  38 . A seal-receiving area  48  is located adjacent to the stem receiving bore  46 . 
   A first bonnet receiving area  50  is adjacent to the seal-receiving area  48 . A second bonnet receiving area  52  is located adjacent to the first bonnet receiving area  50 . The second bonnet receiving area  52  is defined by a non-circular inner perimeter  54 , which is preferably hexagonal although non-circular inner perimeter  54  may be octagonal, pentagonal, square, oval, splined or have another non-circular configuration. Additionally, the non-circular inner perimeter  54  may be substantially circular, but include recesses for receiving one or more keys. 
   An outlet passageway  56  ( FIGS. 2 ,  3 ) is in communication with the stem receiving bore  46 . Outlet passageway  56  is preferably offset from the passageway  28 . Outlet passageway  56  is preferably oriented at an angle of 90° to the passageway  28 , although other orientations of outlet passageway  56  with respect to passageway  28  are possible. 
   A check ball  58  is located in the check ball chamber  30 . The check ball  58  is provided to seal against the tapered check ball seat  36  in the event of a rapid pressure loss through the outlet passageway  56 . 
   A packing assembly  60  is located in the seal receiving area  48  of passageway  28 . The packing assembly  60  has a packing washer  62  located proximate the stem receiving bore  46 , packing member  64  and packing follower  65 , which extends into the first bonnet receiving area  50 . The packing follower  65  has a radial portion located in the first bonnet receiving area  50  of passageway  28 . 
   A packing bonnet  68  has a first end that preferably communicates with the packing follower  65 . Packing bonnet  68  defines a passageway  74  that is in axial alignment with passageway  28 . The passageway  74  has an unthreaded portion  76  that is in communication with the first end of the packing bonnet  68 . Unthreaded portion  76  of passageway  74  is located within the valve body  12  when valve  11  is assembled. A threaded portion  78  of the passageway  74  is adjacent to the unthreaded portion  76 . An outer portion  80  of the passageway  74  is located adjacent to the threaded portion  78  and is in communication with the second end of the packing bonnet  68 . The first end of the packing bonnet  68  is located in first bonnet receiving area  50  of passageway  28  when valve  11  is assembled. 
   The packing bonnet  68  has an external non-circular area  82  proximate the first end of the packing bonnet  68  for complementary engagement with the non-circular inner perimeter  54  of the second bonnet receiving area  52  of the valve body  12 . The external non-circular area  82  of the packing bonnet  68  is preferably hexagonal but may be of any shape having a complementary engagement with non-circular inner perimeter  54  of valve body  12 . The close mating relationship of the external non-circular area  82  of the packing bonnet  68  with the non-circular inner perimeter  54  of the valve body  12  prevents rotation of the packing bonnet  68  with respect to the valve body  12  since packing bonnet  68  preferably has an external flange member  84  provided for interfacing with an inside surface of bonnet nut  26 . Additionally, external non-circular area  82  of packing bonnet  68  and non-circular inner perimeter  54  of seal bonnet receiving area  52  may be shaped to receive one or more keys to prevent relative rotation of the packing bonnet  68  with respect to the valve body  12 . 
   Stem  86  is located within the passageway  28  of the valve body  12 . The stem  86  passes through the passageway  74  of the packing bonnet  68 . The stem  86  has a first end having a check ball displacement pin  90  extending therefrom. The check ball displacement pin  90  extends through the restricted area  38  of the valve body  12  for unseating the check ball  58  from the check ball seat  36  when the stem  86  is in a nearly fully closed position. 
   A tapered stem sealing surface  91  is provided for engaging the restricted area sealing surface or seat  44  of the valve body  12  when the stem  86  is in a fully closed position. An unthreaded portion  92  extends through the stem receiving bore  46  and also passes through the seal receiving area  48  of the valve body  12  for sealing engagement with packing member  64 . In one embodiment, as shown in  FIG. 3 , a minimal clearance is provided between stem  86  and stem receiving bore  46 . For example, stem  86  may have a diameter of 7/16″ and stem receiving bore  46  may have a diameter of 9/16″. A stem flange member  93  is adjacent to the unthreaded portion  92  and is located within the unthreaded portion  76  of the passageway  74  of the packing bonnet  68 . A threaded portion  94  of the stem  86  is adjacent to the stem flange member  93 . Threaded portion  94  of the stem  86  is provided for engaging the threaded portion  78  of the passageway  74  of the packing bonnet  68 . An end portion  95  of the stem  86  is located adjacent to the threaded portion  94  and communicates with an external end of the stem  86 . The external end of the stem  86  defines a threaded cavity therein for receiving a bolt to secure handwheel  98  to stem  86 . 
   Bonnet nut  26  is threaded on external threads  24  on the second end  16  of the valve body  12 . Bonnet nut  26  is provided to secure the packing bonnet  68  within the valve body  12 . Preferably, a weather seal  100  is provided in the packing bonnet  68  for wiping engagement with the stem member  86 . Seal  100  helps retain internal lubrication. 
   Referring now to  FIGS. 4 and 5 , shown is a second embodiment  111  of a valve designated generally  111 . Valve  110  has a body  112  having a first end  114  and a second end  116 . Body  112  comprises valve unit  113 . First end  114  has external threads  118  formed thereon. External threads  118  preferably receive a union nut (not shown) that secures the body  112  to a vessel, such as vessel  15  of  FIG. 1 . Second end  116  of body  112  preferably has external threads  124  for receiving a bonnet nut  126 . Body  112  has a passageway  128  formed therein. Passageway  128  extends from first end  114  to second end  116  of body  112 . The first end  114  of passageway  128  is preferably the valve inlet. Passageway  128  defines a check ball chamber  130  in having a first end  132  and a second end  134 . First end  132  of check ball chamber  130  communicates with first end  114  of body  112 . Check ball chamber  130  preferably has a tapered check ball seat  136  at the second end  134  of the check ball chamber  130 . 
   A restricted area  138  is located adjacent to check ball chamber  130 . Restricted area  138  has a first end in communication with the seat  136  of the check ball chamber  130 . Restricted area  138  additionally has a second end defining a renewable seat receiving area  139 . Seat  144  may be threadably secured within seat receiving area  139  or may be secured by other means. A large stem receiving bore  146  is located adjacent to seat receiving area  139  to accommodate installation and removal of screw-in renewable seat  144 . Renewable seat receiving area  139  is preferably threaded to threadably engage the screw-in renewable seat  144 . A seal-receiving area  148  is located adjacent to the large stem receiving bore  146 . 
   An unthreaded bonnet receiving area  152  is located adjacent to the seal-receiving area  148 . The unthreaded bonnet receiving area  152  is defined by a non-circular inner perimeter  154 , which is preferably hexagonal ( FIG. 6   a ) although non-circular inner perimeter  154  may be octagonal, pentagonal, square, oval or have another non-circular configuration. Additionally, the non-circular inner perimeter  154  may be substantially circular but include recesses  155   a , which may be positioned opposite corresponding recesses  155   b  formed in external non-circular area  182  of packing bonnet  168  ( FIG. 6   b ) for receiving keys  157 . Although the keyed feature is shown in use with the embodiment labeled valve  111 , it should be understood that the keyed feature may be used on the valve embodiment labeled  11  or on other embodiments within the scope of the invention. 
   An outlet passageway  156  is in communication with the large stem receiving bore  146 . Outlet passageway  156  is preferably offset from the passageway  128 . Outlet passageway  156  is preferably oriented at an angle of 90° to the passageway  128 , although other orientations of outlet passageway  156  with respect to passageway  128  are possible. 
   A check ball (not shown) may be located in the check ball chamber  130 . The check ball is provided to seal against the tapered check ball seat  136  in the event of a rapid pressure loss through the outlet passageway  156 . 
   A carrier ring  160  is located in the seal receiving area  148  of passageway  128 . Carrier ring  160  is preferably received within seal receiving area  148 . A seal  161 , such as an O-ring, may be provided between the wall of threaded seal receiving area  148  and the outside surface of carrier ring  160 . Seal  161  may also be positioned on the bottom face of the carrier ring, preferably adjacent a chamfered surface on a first end of the carrier ring  160 . A packing member  162  is preferably received within carrier ring  160 . A packing follower  163  is provided adjacent packing member  162 . Packing follower  163  has an axial portion  164  located proximate the packing member  162 . The packing follower  163  has a radial portion  166  located in the seal receiving area  148  of passageway  128 . The carrier ring  160 , packing member  162  and packing follower  163 , are referred to collectively as the packing assembly  167 . 
   A packing bonnet  168  has a first end that preferably bears against the packing follower  163 . Packing bonnet  168  defines a passageway  174  that is in axial alignment with passageway  128 . The passageway  174  has an unthreaded portion  176  that is in communication with the first end of the packing bonnet  168 . The unthreaded portion  176  of passageway  174  is located within the valve body  112  when valve  111  is assembled. A threaded portion  178  of the passageway  174  is adjacent to the unthreaded portion  176 . An outer portion  180  of the passageway  174  is located adjacent to the threaded portion  178  and is in communication with the second end of the packing bonnet  168 . The first end of the packing bonnet  168  is located in the seal-receiving area  148  of passageway  128  when valve  111  is assembled. 
   The packing bonnet  168  has an external non-circular area  182  proximate the first end of the packing bonnet  168  for complementary engagement with the non-circular inner perimeter  154  of the unthreaded bonnet receiving area  152  of the valve body  112 . The external non-circular area  182  of the packing bonnet  168  is preferably hexagonal but may be of any shape designed for complementary engagement with non-circular inner perimeter  154  of valve body  112 . Packing bonnet  168  may also be keyed to the valve body  112 . The close mating relationship of the external non-circular area  182  of the packing bonnet with the non-circular inner perimeter  154  of the valve body  112  prevents rotation of the packing bonnet  168  with respect to the valve body  112 . The packing bonnet  168  preferably has an external flange member  184  provided for interfacing with an inside surface of a bonnet nut ( FIG. 5 ). Additionally, non-circular inner perimeter  154  may include a configuration including recesses  155   a  for receiving one or more keys  157 . 
   Stem  186  is located within the passageway  128  of the valve body  112 . The stem  186  passes through the passageway  174  of the packing bonnet  168 . The stem  186  has a first end having a check ball displacement pin  190  extending therefrom. The check ball displacement pin  190  extends through the restricted area  138  of the valve body  112  for unseating the check ball (not shown) from the check ball seat  136  when the stem  186  is in a nearly fully closed position. 
   A tapered stem sealing surface  191  is provided for engaging the renewable seat  144  when the stem  186  is in fully closed position. An unthreaded portion  192  extends through the stem receiving bore  146  and also passes through the seal receiving area  148  of the valve body  112  where the stem is in sealing engagement with packing assembly  167 . In one embodiment, a substantial clearance is provided between stem  186  and stem receiving bore  146 . For example, stem  186  may have a diameter of 7/16″ and stem receiving bore  146  may have a diameter of 15/16″. A stem flange member  193  is adjacent to the unthreaded portion  192  and is located within the unthreaded portion  176  of the passageway  174  of the packing bonnet  168 . A threaded portion  194  of the stem  186  is adjacent to the stem flange member  193 . Threaded portion  194  of the stem  186  is provided for engaging the threaded portion  178  of the passageway  174  of the packing bonnet  168 . An end portion  195  of the stem  186  is located adjacent to the threaded portion  194  and communicates with an external end of the stem  186 . The external end of the stem  186  defines a threaded cavity  196  therein for receiving a bolt to secure a handwheel (not shown) to stem  186 . 
   Bonnet nut  126  is threaded on external threads  124  on the second end  116  of the valve body  112 . Bonnet nut  126  is provided to secure the packing bonnet  168  within the valve body  112 . Preferably, a weather seal or stem seal  200  is provided in the packing bonnet  168  for wiping engagement with the stem  186 . Seal  200  helps retain internal lubrication. 
   Referring now primarily to  FIG. 7 , a further embodiment  211  of the valve is shown. Embodiment  211  has a valve unit  212  comprising body  212   a  and attachment piece  212   b . Attachment piece  212   b  has a passageway  228  formed therein. Passageway  228  extends from first end  214  to second end  216  of attachment piece  212   b . Second end  216  is preferably provided with external threads  218 . 
   A chamber  238  is located adjacent to first end  214 . Chamber  238  defines a sealing surface or seat  244 . A stem receiving bore  246  communicates with first end  214 . A seal-receiving area  248  is located adjacent to the stem receiving bore  246 . 
   A first bonnet receiving area  250  is adjacent to the seal-receiving area  248 . A second bonnet receiving area  252  is located adjacent to the first bonnet receiving area  250 . The second bonnet receiving area  252  is defined by a non-circular inner perimeter  254 , which is preferably hexagonal although non-circular inner perimeter  254  may be octagonal, pentagonal, square, oval, splined or have another non-circular configuration. Additionally, the non-circular inner perimeter  254  may be substantially circular, but include recesses for receiving one or more keys. 
   An outlet passageway  256  communicates with the chamber  238  via chamber passageway  257 . Outlet passageway  256  may be offset from or in-line with inlet passageway  259 . Although inlet passageway  259  is shown oriented at a 90° angle with respect to passageway  228 , it should be understood that inlet passageway  259  may be in-line with passageway  228 , as shown in valve embodiments  11 ,  111 , above, or may be oriented at any suitable angle with respect to passageway  228 . Outlet passageway  256  is preferably oriented at an angle of 90° to passageway  228 , although other orientations of outlet passageway  256  with respect to passageway  228  are possible. 
   A packing assembly  260  is located in the seal receiving area  248  of passageway  228 . The packing assembly  260  has a packing washer  262  located proximate the stem receiving bore  246 , packing member  264  and packing follower  265 , which extends into the first bonnet receiving area  250 . The packing follower  265  has a radial portion located in the first bonnet receiving area  250  of passageway  228 . 
   A packing bonnet  268  has a first end that preferably communicates with the packing follower  265 . Packing bonnet  268  defines a passageway  274  that is in axial alignment with passageway  228 . The passageway  274  has an unthreaded portion  276  that is in communication with the first end of the packing bonnet  268 . Unthreaded portion  276  of passageway  274  is located within the valve body  212  when valve  211  is assembled. A threaded portion  278  of the passageway  274  is adjacent to the unthreaded portion  276 . An outer portion  280  of the passageway  274  is located adjacent to the threaded portion  278  and is in communication with the second end of the packing bonnet  268 . The first end of the packing bonnet  268  is located in first bonnet receiving area  250  of passageway  228  when valve  211  is assembled. 
   The packing bonnet  268  has an external non-circular area  282  proximate the first end of the packing bonnet  268  for complementary engagement with the non-circular inner perimeter  254  of the second bonnet receiving area  252  of the attachment piece  212   b  of valve unit  212 . The external non-circular area  282  of the packing bonnet  268  is preferably hexagonal but may be of any shape having a complementary engagement with non-circular inner perimeter  254  of attachment piece  212   b  of valve unit  212 . The close mating relationship of the external non-circular area  282  of the packing bonnet  268  with the non-circular inner perimeter  254  of the attachment piece  212   b  prevents rotation of the packing bonnet  268  with respect to the attachment piece  212   b  since packing bonnet  268  preferably has an external flange member  284  provided for interfacing with an inside surface of bonnet nut  226 . Additionally, external non-circular area  282  of packing bonnet  268  and non-circular inner perimeter  254  of seal bonnet receiving area  252  may be shaped to receive one or more keys to prevent relative rotation of the packing bonnet  268  with respect to the attachment piece  212   b.    
   Stem  286  is located within the passageway  228  of the attachment piece  212   b . The stem  286  passes through the passageway  274  of the packing bonnet  268 . The stem  286  has a first end having a sealing area  290  located thereon. 
   The sealing area  290  is provided for engaging seat  244  of the valve body  212   a  of valve unit  212  when the stem  286  is in a fully closed position. An unthreaded portion  292  extends through the stem receiving bore  246  and also passes through the seal receiving area  248  of the attachment piece  212   b  of valve unit  212  for sealing engagement with packing member  264 . A stem flange member  293  is adjacent to the unthreaded portion  292  and is located within the unthreaded portion  276  of the passageway  274  of the packing bonnet  268 . A threaded portion  294  of the stem  286  is adjacent to the stem flange member  293 . Threaded portion  294  of the stem  286  is provided for engaging the threaded portion  278  of the passageway  274  of the packing bonnet  268 . An end portion  295  of the stem  286  is located adjacent to the threaded portion  294  and communicates with an external end of the stem  286 . The external end of the stem  286  defines a threaded cavity therein for receiving a bolt to secure handwheel  298  to stem  286 . 
   Bonnet nut  226  is threaded on external threads  218  on the second end  216  of the valve unit  212 . Bonnet nut  226  is provided to secure the packing bonnet  268  within the attachment piece  212   b  valve unit  212 . Preferably, a weather seal  300  is provided in the packing bonnet  268  for wiping engagement with the stem member  286 . Seal  300  helps retain internal lubrication. 
   In use, valves  11 ,  111 ,  211  of the invention are used to selectively open or close a fluid path from first end or inlet  14 ,  114 ,  259  of the valve to outlet passageway  56 ,  156 ,  256 . By rotating handwheel  98 ,  298  ( FIGS. 3 and 7 ), stem  86 ,  186 ,  286  is axially displaced by interaction of threaded portion  94 ,  194 ,  294  of stem  86 ,  186 ,  286  with threaded portion  78 ,  178 ,  278  of passageway  74 ,  174 ,  274 . Depending on the direction of rotation of stem  86 ,  186 ,  286  tapered stem sealing surface or sealing area  91 ,  191 ,  290  moves towards or away from sealing surface  44 ,  244  ( FIGS. 3 and 7 ) or renewable seat  144  ( FIG. 5 ). When the tapered stem sealing surface or sealing area  91 ,  191 ,  290  is engaging sealing surface or seat area  44 ,  244  or renewable seat  144 , the valve is in a closed state. 
   When the tapered stem sealing surface or sealing area  91 ,  191 ,  290  is disengaged from the seat area  44 ,  144 ,  244  the valve is in an opened state. When valve  11 ,  111 ,  211  is in an opened state, fluid may migrate from first end or inlet  14 ,  144 ,  259  through check ball chamber or chamber  30 ,  130 ,  238  through restricted area  38 ,  138 , and into stem receiving bore  46 ,  146  before exiting out through outlet passageway  56 ,  156  of the valve. Alternatively, embodiment  211  ( FIG. 7 ) selectively allows fluid to pass from inlet  259  to outlet  256  by selectively engaging or disengaging sealing area  290  with sealing surface  244 . In all embodiments  11 ,  111 ,  211 , packing assembly  60 ,  167 ,  260  sealingly engages the stem  86 ,  186 ,  286  which prevents fluid migration from the stem receiving bore  46 ,  146 ,  246  into contact with threaded portion  94 ,  194 ,  294  of stem  86 ,  186 ,  286 . 
   To adjust compression on packing assembly  60 ,  167 ,  260  bonnet nut  26 ,  126 ,  226  ( FIGS. 3 ,  5  and  7 ) is rotatably adjusted. Bonnet nut  26 ,  126 ,  226  acts on external flange member  84 ,  184 ,  284  of packing bonnet  68 ,  168 ,  268  to press packing bonnet  68 ,  168 ,  268  into packing assembly  60 ,  167 ,  260  by a desired amount. 
   Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.