Abstract:
A valve having an outer housing defining a central bore with a fluid inlet and a fluid outlet. A check dart assembly, valve seat and piston assembly are retained within the central bore. The valve is moveable between open and closed positions in response to fluid flow into the fluid inlet of the valve.

Description:
[0001]    The present application claims priority to U.S. provisional patent application Ser. No. 61/533,323 filed Sep. 12, 2011. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to check valves. 
         [0004]    2. Description of the Related Art 
         [0005]    A common form of check valve is a ball member that is biased against a valve seat by a spring. Check valves are used to provide one way flow in a wide variety of applications, including chemical injection devices. Cavitation of fluid passing through the check valve can cause undesirable erosion of the check valve ball and seat. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides improved check valve designs that reduce fluid cavitation. In addition, the design of the valve reduces erosion around the valve seat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The advantages and other aspects of the invention will be readily appreciated by those of skill in the art and better understood with further reference to the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawings and wherein: 
           [0008]      FIG. 1  is a side, cross-sectional view of an exemplary valve constructed in accordance with the present invention, with the valve in a closed position. 
           [0009]      FIG. 2  is a side, cross-sectional view of the valve shown in  FIG. 1 , now in an open position. 
           [0010]      FIG. 3  is an enlarged, side cross-sectional view of portions of an exemplary piston assembly used in the valve of  FIGS. 1-2 . 
           [0011]      FIG. 4  is a side, cross-sectional view depicting two alternative piston assemblies. 
           [0012]      FIGS. 5A ,  5 B and  5 C are a side, cross-sectional view of an alternative embodiment for an exemplary valve constructed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]      FIGS. 1-2  illustrate an exemplary valve  10  which has been constructed in accordance with the present invention. The valve  10  includes an outer housing  12  that defines an inner axial bore  14  along its length. In the depicted embodiment, the housing  12  is made up of a primary housing member  16  and an affixed cap  18 . Axial ends of the housing  12  provide a fluid inlet  20  and a fluid outlet  22 . The housing  12  may be provided with suitable threaded end portions (not shown) for incorporation of the valve into a flow line or other fluid flow path. 
         [0014]    The axial bore  14  generally contains a piston assembly  24 , a valve seat  26 , and a check dart assembly  28 . The piston assembly  24  includes a piston housing  30  that defines an enlarged-diameter inner chamber  32  and a reduced-diameter inner chamber  34 . The piston housing  30  is fixedly secured within the bore  14 . Piston member  36  is moveably disposed within the inner chambers  32 ,  34 . The piston member  36  includes an enlarged base portion  38  and a reduced-diameter prong portion  40  that extends axially from the base portion  38 . The prong portion  40  presents a curved distal end face  43 . In the depicted embodiment, an axial flow passage  42  and a plurality of lateral flow passages  44  are formed within the enlarged base portion  38  of the piston member  36 . A generally cylindrical sleeve  39  is fixedly disposed within the bore  14  and radially surrounds the base portion  38  of the piston member  36 . When the valve  10  is in the closed position, the lateral flow passages  44  are closed off by the sleeve  39 . In a preferred embodiment, the base portion  38  of the piston member  36  presents an outer radial surface  41  that is roughened in order to provide increased frictional resistance against movement with respect to the sleeve  39 . In one embodiment, the radial surface  41  is roughened by threading, as depicted in  FIG. 3 . The threading permits some fluid to be transmitted across the piston member  36  via the threads. 
         [0015]    The downstream end of the piston housing  30  abuts the valve seat  26 . The valve seat  26  defines a reduced-diameter flow passage  46 . The prong portion  40  of the piston member  36  is shaped and sized to pass through the flow passage  46  loosely such that fluid may flow around the prong portion  40  (see  FIG. 2 ). 
         [0016]    The check dart assembly  28  includes a check dart  48  that has an elongated shaft portion  50  and a head portion  52 . An outwardly projecting flange  54  is located between the shaft and head portions  50 ,  52 . An axial bore  56  is defined along the length of the shaft portion  50 . The head portion  52  is preferably conically shaped and has lateral flow openings  58  disposed therein which are in communication with the bore  56 . 
         [0017]    The check dart assembly  28  also includes a compression spring  60  that radially surrounds the shaft portion  50  of the check dart  48 . The spring  60  axially abuts the flange  54  at one end and an adjustment member or adjustment nut  62 , which lies radially outside of the shaft portion  50 , at the other axial end. The adjustment nut  62  is engaged by loose threading with the shaft portion  50  and the nut  62  may be rotated with respect to the shaft portion  50  in order to adjust axial compression loading on the spring  60 . A locking nut  64  also radially surrounds the shaft portion  50  and is engaged by threading with the shaft portion  50 . The locking nut  64  may be rotated with respect to the shaft portion  50  in order to secure the adjustment nut  62  in place axially upon the shaft portion  50 . Due to the bias provided by the spring  60 , the head portion  52  of the check dart  48  is in continuous contact with the curved end face  43  of the prong portion  40  of the piston member  36 . 
         [0018]    The valve  10  may be moved from the closed position ( FIG. 1 ) to the open position ( FIG. 2 ) by fluid flow into the valve  10 . In the closed position, the head portion  52  of the check dart  48  is in contact with the valve seat  26 , thereby closing off the flow passage  46  against fluid flow therethrough. Fluid is flowed into the valve  10  via the fluid inlet  20 . Upon encountering the piston member  36 , the fluid exerts pressure against the upstream end of the piston member  36 . Movement of the piston member  36  will compress the spring  60  and push the head portion  52  of the check dart  48  off the valve seat  26 . Movement of the piston member  36  unblocks the lateral flow passages  44  by moving them out of the surrounding sleeve  39 . Fluid can flow through the flow passages  42 ,  44  and the flow passage  46  of the valve seat  26 . Fluid then flows into the lateral flow openings  58  and the axial bore  56  of the check dart  48 . The fluid can then flow out of the fluid outlet  22  of the valve  10 . 
         [0019]    In particular embodiments, the flow patterns provided by the valve  10  reduce cavitation of fluid passing through the valve  10 . The sleeve  39  is used to block flow through lateral passages  44  until the check dart  48  is lifted off of the valve seat  26 . Proper placement of the lateral passages  44  within the base portion  38  of the piston member  36  will allow the head portion  52  of the check dart  48  to have an increased clearance of the valve seat  26  as flow through the passage  46  of the valve seat  26  occurs. As a result, a wider gap ( 70  in  FIG. 2 ) is provided for the fluid to flow through, thereby reducing fluid cavitation proximate the passage  46 . As cavitation is reduced, damage from erosion around the valve seat  26  is reduced. 
         [0020]    Also, the design of the valve  10  allows selective adjustment of the force required to open the valve  10  by rotation of the adjustment nut  62  to increase or decrease a pre-compressive force to the spring  60 . As the spring  60  is compressed by rotation of the adjustment nut  62 , the force required to open the valve  10  is increased. Conversely, as the spring  60  is uncompressed by opposite rotation of the adjustment nut  62 , the force required to open the valve  10  is reduced. 
         [0021]    Where a roughened radial surface  41  is used for the valve  10 , the opening force for a particular valve  10  may be adjusted by altering the length of the base portion  38  of the piston member  36  or, at least, the length of the roughened radial surface  41  of the base portion  38 .  FIG. 4  is an enlarged detail drawing depicting an exemplary valve system  80  having two valves  10 ,  10 ′ which are interconnected in parallel with a single fluid source, shown schematically at  82 . There may be more than two such valves  10 ,  10 ′ in a given system  80 . The valve system  80  could be representative of a wellbore chemical injection system wherein the two valves  10 ,  10 ′ are chemical injectors at different locations within a wellbore for injection of chemicals into the formation surrounding the wellbore.  FIG. 4  presents enlarged cross-sectional views of the piston assemblies  24 ,  24 ′ of the two valves  10 ,  10 ′. The piston assembly  24  of valve  10  has a piston member  36  with a base portion  38  that presents a roughened outer surface  41 . The piston assembly  24 ′ of valve  10 ′ has a piston member  36 ′ with an elongated base portion  38 ′ that presents roughened radial surface  41 ′. The roughened radial surface  41 ′ has a greater axial length than the radial surface  41 . As a result, the piston assembly  24 ′ provides a greater frictional resistance to moving its piston member  36  than does the piston assembly  24  of valve  10 . It will require greater fluid pressure to move the piston member  38 ′ within valve  10 ′ than the piston member  38  of valve  10 . For this reason, the valve  10  can be opened at a first fluid pressure, and the valve  10 ′ can be opened only at a second fluid pressure that is greater than the first fluid pressure. By altering the axial length of the roughened radial surface, one can control the fluid pressure required to open a particular valve. It should be understood that, while only two valves  10 ,  10 ′ are shown, the system  80  might include third, fourth and additional valves, each having their own opening fluid pressure requirement. Such as system  80  would permit, for example, chemicals to be injected into one or more first well zones at a first fluid pressure, but not inject into a second group of well zones. At a higher fluid pressure, chemicals are injected into both the first and second groups of well zones. 
         [0022]      FIGS. 5A ,  5 B and  5 C depict an alternative valve  100  constructed in accordance with the present invention. Except where indicated otherwise, the valve  100  is constructed and operates in the same manner as the valve  10  previously described. The valve  100  includes an outer housing  102  that, in the depicted embodiment, is made up of an upper sub  104 , intermediate sub  106  and a lower sub  108 . A frangible burst disc  110  is secured within the inlet  112  of the upper sub  104  by a jam nut  114  that is threaded into the inlet  112 . The burst disc  110  is designed to rupture when it encounters a predetermined fluid pressure differential. The intermediate sub  106  houses sleeve  114  which is similar to sleeve  39  described previously. Piston  116  is similar to piston  36  and presents prong portion  118 . An axial flow passage  120  and lateral flow passages  122  are formed within the piston  116 . The prong portion  118  contacts the head portion  124  of check dart  126 . A valve seat is provided by an annular check pad  128 . The check pad  128  is preferably formed of a durable thermoplastic polymer material such as PEEK (polyether ether ketone). An annular metallic ring  130  is preferably disposed between the check pad  128  and the check dart  126 . 
         [0023]    The check dart  126  is similar to the check dart  48  described previously. Lateral flow openings  132  and bore  134  are defined within the check dart  126 . Spring  136  is similar to the spring  60  described previously. The adjustment nut  138  is similar to the adjustment nut  62  described earlier. The valve  100  is also provided with a pair of locking nuts  140 ,  142 . In the depicted embodiment, the locking nut  140  has a standard, right-handed thread. The locking nut  142  has a left-handed thread. A spacer ring  144  is located between the adjustment nut  138  and the locking nut  140  to help prevent the transmission of torque from the locking nut  142  to the adjustment nut  138 . A user can rotate the adjustment nut  138  to adjust axial compression loading on the spring  136 . Thereafter, the adjustment nut  138  is secured in place by tightening the first locking nut  140  and spacer ring  144  up against the adjustment nut  138 . Then, the second locking nut  142  is rotated and tightened up against the first locking nut  140 . The use of two, oppositely-threaded locking nuts  140 ,  142  helps prevent inadvertent loosening of the adjustment nut  138 . 
         [0024]    In operation, fluid is flowed toward the valve  100  along fluid conduit  148 . No fluid will enter the valve  100  due to the presence of burst disc  110 . After fluid pressure has been increased to create a sufficient pressure differential across the disc  110 , the disc  110  will rupture, allowing fluid to enter the valve  100 . The valve  100  will open and close in largely the same manner as the valve  10  described earlier. 
         [0025]    Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.