Abstract:
A tool for replacing a valve seat of a reciprocating pump has a puller shaft connected to a puller head having at least two spring-biased dogs. An operator inserts the puller head into a valve bore and through a valve seat, the dogs retracting as the puller head moves through the valve seat, then snapping back outward. A hydraulic cylinder engages the puller shaft to exert a force on the puller shaft causing the dogs to dislodge the seat. The operator then places a replacement valve seat on a shoulder in the valve bore. The operator attaches an installing head to an installing shaft and inserts the installing head into the valve bore into contact with the replacement valve seat. The hydraulic cylinder applies a force in an opposite direction on the installing shaft to push the replacement valve seat into installed engagement.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to provisional application 61/261,632, filed Nov. 16, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates in general to tools for retrieving and installing valve seats in a fluid end of a reciprocating pump. 
       BACKGROUND OF THE INVENTION 
       [0003]    One type of well service pump is particularly used for hydraulic fracturing operations, also called “frac” operations. Fluid at high pressure is pumped down the well to cause the producing formation to fracture. Beads may be mixed into fluid being pumped to prop the cracks open. The pressures may exceed 10,000 psi, and the fluids are abrasive. 
         [0004]    These pumps are commonly mounted to trucks that are dispensed almost daily for performing frac operations. Because of the severe operating conditions, the operators must change various components such as valves, valve seats and plunger seals frequently. It is important to be able to change out these components quickly. 
         [0005]    A frac pump has a suction valve and a discharge valve for each plunger, and pumps have typically three or five plungers. The suction and discharge valves are located within valve bores that normally intersect the plunger bore at 90 degrees. Each suction valve bore is co-axial with the discharge valve bore and usually located below the plunger bore. Normally, the plunger bore extends past the valve and suction bores to an end wall of the pump. This extension portion comprises an access passage that allows the operator to reach into and remove the suction valve. The discharge valve is typically removed from above. 
         [0006]    The valve seats are pressed into mating shoulders formed in the bore. If they are to be removed, the common practice is to employ bars and hammer to dislodge them. This can be difficult, particularly because it requires the operator to access the valve seats from below. Similarly, replacement valve seats are normally installed by a hammer and bar. Using a hammer and bar can lead to injury. Puller tools to remove valve seats have been built, but because of various problems, are not utilized extensively. 
       SUMMARY 
       [0007]    The method described herein includes providing a puller head having at least two dogs mounted thereto and securing the puller head to a puller shaft. The dogs are outwardly radially biased relative to an axis of the puller shaft. The operator inserts the puller head into a valve bore and through the valve seat in a first direction. The dogs retract as the puller head moves through the valve seat, then snap back outward. The operator then causes a force to be applied to the puller shaft in a second direction opposite to the first direction, which causes the dogs to dislodge the valve seat. 
         [0008]    After retrieving the puller head and the puller shaft, the operator places a replacement valve seat on a shoulder in the valve bore. He attaches an installing head to an installing shaft and inserts the installing head into the valve bore and into contact with the replacement valve seat. He then causes a force to be applied to the installing shaft in the first direction to push the replacement valve seat into installed engagement with the shoulder. 
         [0009]    Preferably the operator causes the forces to be applied to the shafts by extending the shaft through a hydraulic cylinder and actuating the hydraulic cylinder in either the second direction or first direction. The puller shaft and the installing shaft may be one and the same. 
         [0010]    In a preferred embodiment, the coupling between the shaft and the hydraulic cylinder is via a piston nut and a shaft nut. The piston nut is secured within a piston passage extending through the piston. The piston nut has a hole through which the shaft extends. The shaft nut has a larger periphery or diameter than the piston nut hole. Movement of the piston causes the piston nut to apply a force to the shaft nut and the shaft. 
         [0011]    Preferably, the shaft nut is secured to the shaft by a threaded engagement. This allows the operator to abut the shaft nut against the piston nut by rotating the shaft nut while the head is in contact with the valve seat. 
         [0012]    Preferably the fluid end body of the pump and the hydraulic cylinder have mating threads. Securing the hydraulic cylinder to the fluid end body causes the installing force to be reacted through the cylinder into the fluid end body. 
         [0013]    The fluid end body of the pump preferably has two valve seats, and an access passage intersects the valve bore between the two valve seats. After dislodging the lower valve seat with the puller tool, the operator can reach through the access passage and detaching the lower valve seat from the puller head. He then can lift the puller head up against the upper valve seat. Exerting an upward force on the puller shaft causing the dogs to dislodge the upper valve seat. The hydraulic cylinder can remain secured to the fluid end body for removing both of the valve seats by employing the access passage to retrieve the lower valve seat before retrieving the upper valve seat. The lower valve seat has too large of a diameter to allow it to be pulled upward through the upper valve seat. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a partially sectioned side view of a valve seat retrieval tool in accordance with this invention, shown being lowered into a valve passage of a pump fluid block. 
           [0015]      FIG. 2  is an enlarged sectional view of a portion of the valve retrieval tool of  FIG. 1 , shown located below the valve seat in preparation to exerting a pulling force on the valve seat. 
           [0016]      FIG. 3  is a sectional view illustrating a fluid cylinder installed on the pump fluid block and in engagement with the shaft of the retrieval tool for applying a pulling force on the shaft of the retrieval tool. 
           [0017]      FIG. 4  is a partially sectioned view of the valve retrieval tool of  FIG. 3 , shown employed to retrieve a lower valve seat before retrieving the upper valve seat. 
           [0018]      FIG. 5  is a side view of a valve installation tool that incorporates the shaft of the valve retrieval tool. 
           [0019]      FIG. 6  is a sectional view of the valve installation tool of  FIG. 5  and the fluid cylinder of  FIG. 3  shown applying a pushing force on a lower valve seat. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring to  FIG. 1 , a pump fluid block  11  is shown partially in section. Pump fluid block  11  is a fluid portion of a large reciprocating pump such as used for high pressure fluid injection into oil and gas wells during hydraulic fracturing operations. Pump fluid block  11  has a number of valve passages  13  (only one shown), each containing a valve seat  15 . Valve passage  13  is shown extending vertically, but it could be oriented horizontally or in other directions. The terms such as “upper” or “upward” and “lower” or “downward” are used only for convenience. Valve seat  15  is pressed with an interference fit onto an upward facing conical shoulder  16  in valve passage  13 . A valve member (not shown) would normally be mounted above valve seat  15 , the valve member having a mating surface for engaging valve seat  15  and a spring that urges the valve member against the seat. The valve member will be removed prior to removing valve seat  15 . 
         [0021]      FIG. 1  shows a retrieval or removal tool  17  for valve seat  15  in the process of being inserted into valve passage  13 . Removal tool  17  includes an enlarged head  18  secured to a shaft  19 , such as by threads. Head  18  has and two or more dogs  21  mounted thereto that are urged radially outward relative to an axis of shaft  19 . Referring to  FIG. 2 , dogs  21  slide between contracted and radially expanded positions relative to the axis of shaft  19 . Springs  23  in head  18  engage the inner ends of dogs  21  for urging dogs  21  outward. Dogs  21  may have chamfers  25  on the lower outer ends for facilitating sliding past valve seat bore  27 . Head  18  of retrieval tool  17  is generally cylindrical and has a smaller outer diameter than the inner diameter of valve seat bore  27 . The operator can manually push on shaft  19  to force head  18  downward through bore  27  of valve seat  15 , which causes dogs  25  to retract, and then expand outward again to an outer diameter that is greater than the inner diameter of seat bore  27 . 
         [0022]    Referring to  FIG. 3 , the operator may use a fluid cylinder  29  to exert an upward force on shaft  19  to dislodge valve seat  15  from valve passage  13 . Fluid cylinder  29  may be a variety of types and may be either hydraulically or pneumatically driven. In this embodiment, fluid cylinder  29  has a housing  31  that has a generally cylindrical exterior. Housing  31  may have an external set of threads formed on its lower end for engaging a threaded counterbore  33  located at the upper end of valve passage  13 . The external threads could alternately be located on a sleeve attached to housing  31 . Threaded counterbore  33  normally receives a threaded cap (not shown) to close valve passage  13  while fluid block  11  is in operation. Threaded counterbore  33  has a larger diameter than the diameter of valve passage  13  immediately below counterbore  33 . Other arrangements to quickly secure fluid cylinder  29  to fluid block  11  and release it from fluid block  11  may alternately be employed. 
         [0023]    Housing  31  has a bore extending completely through it for the insertion of shaft  19 . The passage includes a first or lowermost bore section  35   a ; a second bore section  35   b  joining first bore section  35   a ; a third bore section  35   c  joining second bore section  35   b ; and a fourth bore section  35   d  joining third bore section  35   c . In this embodiment, bore sections  35   a ,  35   b ,  35   c , and  35   d  have different diameters, with the smallest being first bore section  35   a  and the largest being fourth bore section  35   d . Third bore section  35   c  is greater in diameter than second bore section  35   b . A retainer sleeve  37  with external threads  39  may be secured into fourth bore section  35   d . Retainer sleeve  37  has a bore  41  that may be the same diameter as second bore section  35   b.    
         [0024]    Prior to securing retainer sleeve  37 , a piston  43  is installed within second and third bore sections  35   b  and  35   c . Piston  43  strokes between the lower position shown in  FIG. 3  and the upper position shown in  FIG. 6 . Piston  43  has a lower outer diameter portion  43   a  that fits closely and reciprocates within second bore section  35   b . Piston  43  has a central outer diameter portion  43   b  that fits closely and reciprocates within third bore section  35   c . Piston  43  has an upper outer diameter portion  43   c  that fits closely and reciprocates within retainer sleeve bore  41 . Piston  43  has an axial passage  44  extending from its upper end through its lower end. Piston passage  44  may have a uniform inner diameter that is greater than the outer diameter of shaft  19 . A lower seal  45  seals between piston lower outer diameter portion  43   a  and second bore section  35   b . A central seal  47  seals between piston central outer diameter portion  43   b  and third bore section  35   c . An upper seal  49  seals between piston upper outer diameter portion  43   c  and inner sleeve bore  41 . 
         [0025]    A lower chamber  51  is defined between lower seal  45  and central seal  47 . Lower chamber  51  changes in volume depending on the position of piston  43 . In the position shown in  FIG. 3 , lower chamber  51  has a minimum volume and in  FIG. 6 , it has a maximum volume. Similarly, an upper chamber  53  is defined by central seal  47  and upper seal  49 . In  FIG. 3 , upper chamber  53  is at its maximum volume and in  FIG. 6 , it is at its minimum volume. A lower port  55  extends through housing  31  laterally outward from lower chamber  51 . An upper port  57  extends laterally through housing  31  from upper chamber  53  to the exterior. Lower port  55  and upper port  57  are each connected to a separate line or tube  59  for supplying fluid under pressure to lower chamber  51  or upper chamber  53 . Supplying fluid pressure to lower port  55  will cause piston  43  to move upward. Supplying fluid pressure to upper port  57  will cause piston  43  to move downward. 
         [0026]    A variety of engaging devices may be employed to interconnect piston  43  with shaft  19  to cause it to move upward when piston  43  moves upward and downward when piston  43  moves downward. The engaging device in this example includes a piston nut  61  secured to piston  43  by threads  62  within piston passage  44  at its upper end. Piston nut  61  comprises a cylindrical sleeve with an inner diameter greater than the outer diameter of shaft  19 . The engaging device also includes a shaft nut  63  secured to a shaft thread  64  located on and extending along the exterior of shaft  19 . Shaft nut  63  is positioned above piston nut  61  when using to retrieve valve seat  15  and my also be a cylindrical sleeve. The outer diameter of shaft nut  63  is greater than the inner diameter of piston nut  61  so as to transfer an upward force being exerted by piston  43  to shaft nut  63 , which in turn causes shaft  19  to move upward. Preferably, the outer diameter of shaft nut  63  is smaller than the inner diameter of retainer sleeve bore  41  so as to allow one to manually grip and rotate shaft nut  63  while it is inside retainer sleeve  37 . 
         [0027]    In one mode of operation of the embodiment of  FIGS. 1-3 , the operator will remove the access cap (not shown) and valve element (not shown) from valve passage  13 . The operator inserts shaft  19  through fluid cylinder  29  and places fluid cylinder piston  43  in the lower position. The operator secures retrieval head  18  to the lower end of shaft  19  and shaft nut  63  to shaft threads  64  above piston nut  61 . The operator manually pushes retrieval tool  17  downward through valve seat  15  to the position in  FIG. 2 . The operator will manually rotate shaft nut  63  downward on shaft  19  until it rests on piston nut  61 . Dogs  21  should be located slightly below or touching the lower end of valve seat  15 . Shaft  19  will be constrained against axial movement by the engagement of dogs  21  with valve seat  15  at the lower end and with shaft nut  63  resting on piston nut  61  at an upper end of the assembly. 
         [0028]    The operator then applies fluid pressure, either pneumatic or hydraulic, to lower port  55 . This fluid pressure pressurizes lower chamber  51 , pushing piston  43  upward. Piston nut  61  will push upward on the lower end of shaft nut  63 , transferring an upward force to shaft  19 . Shaft  19  moves upward, transferring the upward force into retrieval head  18  and dogs  21 . The upward force passes from dogs  21  to valve seat  15 , causing it to dislodge from its position within valve passage  13  and move upward. Once dislodged, the operator can unscrew fluid cylinder  29  from threaded counterbore  33 , then lift the entire assembly to pull retrieval tool  17  and valve seat  15  upward and out of valve passage  13 . 
         [0029]      FIG. 4  illustrates more features of pump fluid block  11 . Normally, a lower valve seat  65  will be mounted within a lower valve passage  67  that is co-axial with the first mentioned valve passage  13 , which may be referred to as upper valve passage  13 . Lower valve passage  67  and upper valve passage  13  are intersected by a plunger bore  69  that has an axis perpendicular to the common axis of passages  13  and  67 . Normally, a piston type plunger (not shown) will stroke along plunger bore  69 , causing the valves (not shown) located within passages  13  and  67  to open and close with each plunger stroke. Normally the upper valve will open on the discharge stroke and the lower valve will open on the suction stroke. 
         [0030]      FIG. 4  also shows that typically pump fluid block  11  will have a flange  71  for bolting to a power section of the pump, which includes a crankshaft and gear mechanism. Pumps of this nature typically have three or more plungers and sets of suction and discharge valves located side-by-side. Fluid is normally drawn in through the lower valve passages  67  and discharged out the upper valve passages  13 . An intake manifold (not shown) may be attached to the lower ends of lower valve passages  67 . 
         [0031]    Lower valve seat  65  is press-fitted onto an upward-facing conical shoulder  66 , resulting in a larger diameter in lower valve passage  67  above shoulder  66  than below. Lower valve seat  65  thus cannot be removed by moving it downward in lower valve passage  67 . Also, lower valve seat  65  may have the same dimensions as upper valve seat  15  or otherwise not be small enough to be pulled upward through upper valve passage  13  even if upper valve seat  15  were retrieved first. However, plunger bore  69  has an access opening  70  that is closed during pump operation by a threaded access cap (not shown). The operator wishing to pull lower valve seat  65  may utilize opening  70  in plunger bore  69  to retrieve and install lower valve seat  65 . 
         [0032]    In one method, lower valve seat  65  is retrieved before upper valve seat  15 , although this could be reversed.  FIG. 4  illustrates that shaft  19  is long enough for the operator to insert retrieval tool  17  through upper valve passage  13 , upper valve seat  15  and into lower valve passage  67  to a position where dogs  21  are below lower valve seat  65 . The operator will adjust shaft nut  63  ( FIG. 3 ) downward to contact the upper end of piston nut  61  ( FIG. 3 ) while dogs  21  are just below lower valve seat  65 . The operator supplies fluid to lower port  55  of fluid cylinder  29  to exert an upward force on shaft  19 , causing lower seat  65  to dislodge. The operator may then grip shaft  19  and manually lift retrieval tool  17  until retrieval head  18  is located within plunger bore  69 . The operator may then reach through opening  70  and manually depress dogs  21  inward to allow lower seat ring  65  to drop downward over retrieval head  18 . The operator withdraws lower valve seat  65  through opening  70  and pulls shaft  19  upward until retrieval head dogs  21  abut upper valve seat  15 . The operator then repeats the process described above. 
         [0033]    After both valve seats  15  and  65  are retrieved, the operator may then install new valve seats  15  and  65 . An installing head  73 , illustrated in  FIG. 5 , may be employed to force lower seat  65  ( FIG. 4 ) and upper seat  15  ( FIG. 3 ) into their installed positions. Installing head  73  may have its own shaft  19  or it may be secured to the same shaft  19  that previously supported retrieving head  18 . Installing head  73  has a circular, slightly conical lip  75  on its lower end that is adapted to fit within the interior of valve seat  15  or valve seat  65 , as shown in  FIG. 6 . Referring still to  FIG. 5 , lip  75  depends from a conical flange  77  that will contact and bear against the conical upper surfaces of valve seats  15  and  65 . Preferably, hexagonal flats or drive surfaces  79  are formed on the upper end of installing head  73 . Similar drive surfaces are located on the lower end of shaft  19  for receiving wrenches to secure the mating threads of installing head  73  on shaft  19  after removing retrieving head  18  from shaft  19 . In the preferred embodiment, the maximum outer diameter of installing head  73  is less than the diameter of upper valve passage  13  below shoulder  16 . 
         [0034]    The same fluid cylinder  29  may be employed for press-fitting valve seats  15  and  65  that is used to retrieve the valve seats. However, in this example, fluid cylinder  29  is altered slightly when changing it from retrieving to installing and vice-versa. The operator adjusts shaft nut  63  on threads  64  so that it is below piston nut  61 , rather than above. This may be performed by removing piston nut  61 , inserting shaft  19  and shaft nut  63  into fluid cylinder  29 , then re-installing piston nut  61  above shaft nut  63 . It could also be done by inserting shaft  19  and shaft nut  63  into fluid cylinder  29  from the lower end. 
         [0035]    In this example, lower valve seat  65  is installed first, then upper seat  15 , but this process could be reversed.  FIG. 6  illustrates installing head  73  in the process of installing lower valve seat  15 . Using access port  70  and plunger bore  69  ( FIG. 4 ), the operator manually places lower valve seat  65  on shoulder  66 . Lower valve seat  65  will not yet be fully installed in shoulder  66  as this requires a substantial force. The operator attaches installing head  73  to shaft  19  and inserts shaft  19  and head  73  through upper valve passage  13  until its lower end is in plunger passage  69 . Installing head  73  passes below shoulder  16  ( FIG. 4 ) because of its smaller outer diameter and lands on the upper end of lower valve seat  65 . The operator adjust shaft nut  63  to the desired approximate distance from installing head  73 . The operator places piston  43  in the upper position shown in  FIG. 6 . The operator lowers fluid cylinder  29  over shaft  19  and secures its threads to threaded bore  33 . The operator then inserts piston nut  61  over shaft  19  and secures it to threads  62  with the lower end of piston nut  61  abutting the upper end of shaft nut  63 . 
         [0036]    The operator applies fluid pressure into upper port  57 , which pressurizes upper chamber  53 , forcing piston  43  downward. Piston nut  61  transfers the force to shaft nut  63 , which in turn transfers the force to shaft  19 . Shaft  19  moves downward and transfers the downward force through installing head  73  against valve sleeve  65 , forcing it downward into its proper position on shoulder  66 . 
         [0037]    The operator may then release the fluid pressure and remove fluid cylinder  29  from fluid block  11 , bringing along with it shaft  19  and installing head  73 . The operator inserts the upper valve seat  15  ( FIG. 4 ) through the open upper end of upper valve passage  13  and places it on shoulder  16 . The operator inserts installing head  73  onto upper valve seat  15  while attached to shaft  19 . The operator secures fluid cylinder  29  to counterbore threads  33  and repeats the process described above to push upper valve seat  15  into shoulder  16 . 
         [0038]    The tool described is used both to remove and install valve seats. The tool eliminates having to deliver blows to bars to release and install valve seats. 
         [0039]    While shown in only one of its fauns, it should be apparent to those skilled in the art that the method and apparatus described are susceptible to various changes and improvements.