Abstract:
A fluid end assembly comprising a fluid end housing with multiple discharge manifold ports. Embodiments of the disclosure provide a fluid end assembly that overcomes problems associated with prior art single port discharge manifold designs that result in non-symmetrical flow of discharged fluids through the fluid end discharge valves, resulting in premature failure of said valves. The multiple port manifolds of the present disclosure overcome problems associated with non-symmetrical flow of discharged fluids through a fluid end discharge valve, thereby improving valve life and performance.

Description:
PRIORITY DATA 
       [0001]    This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/656,718 filed on Jun. 7, 2012. By this reference, the aforementioned provisional patent application is incorporated herein for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention generally concerns high-pressure plunger-type pumps useful, for example, in oil well hydraulic fracturing. More specifically, the invention relates to fluid end discharge manifolds suitable pumping abrasive fluids, such as sand slurries at high pressures. 
       BACKGROUND OF THE INVENTION 
       [0003]    Engineers typically design high-pressure oil field plunger pumps in two sections; the (proximal) power section and the (distal) fluid section. The power section usually comprises a crankshaft, reduction gears, bearings, connecting rods, crossheads, crosshead extension rods, etc. The power section is commonly referred to as the power end by the users and hereafter in this application. The fluid section is commonly referred to as the fluid end by the users and hereafter in this application. Commonly used fluid sections usually comprise a plunger pump housing having a suction valve in a suction bore, a discharge valve in a discharge bore, an access bore, and a plunger in a plunger bore, plus high-pressure seals, retainers, etc.  FIG. 1  is a cross-sectional schematic view of a typical fluid end showing its connection to a power end by stay rods.  FIG. 1  also illustrates a fluid chamber which is one internal section of the housing containing the valves, seats, plungers, plunger packing, retainers, covers, and miscellaneous seals previously described. A plurality of fluid chambers similar to that illustrated in  FIG. 1  may be combined, as suggested in the Triplex fluid end housing schematically illustrated in  FIG. 2 . It is common practice for the centerline of the plunger bore and access bore to be collinear. Typically in the prior art, the centerlines of the plunger bore, discharge bore, suction bore, and access bore are all arranged in a common plane. The spacing of the plunger bores, plungers, plunger packing, and plunger gland nut within each fluid chamber is fixed by the spacing of the crank throws and crank bearings on the crankshaft in the power end of the pump. 
         [0004]    Engineers typically design high-pressure oil field plunger pumps with internal discharge manifolds as shown in  FIGS. 1 and 2 . As shown in  FIG. 2 , the internal discharge manifold penetrates both ends of the fluid end block, provisions are made for a pipe or line connection on both ends of the block. Typically with small plunger sizes, one end is fitted with a blind flange to seal off the end fitted with the blind flange, thus all fluid flow is directed through the opposite end of the manifold. For large plungers or fluid ends with more than three plungers, a connection is added at both ends of the manifold, thus fluid flow is in both directions. For pumps fitted with discharge lines from both ends of the manifold, the discharge fluid flow is then collected from both ends of the manifold along with discharge flow from additional pumps into a larger manifold downstream from the pump. This downstream manifold then combines all the incoming fluid flow into one outlet to direct the combined flow into the oil well. 
         [0005]    Valve terminology varies according to the industry (e.g., pipeline or oil field service) in which the valve is used. In some applications, the term “valve” means just the valve body, which reversibly seals against the valve seat. In other applications, the term “valve” includes components in addition to the valve body, such as the valve seat and the housing that contains the valve body and valve seat. A valve as described herein comprises a valve body and a corresponding valve seat, the valve body typically incorporating an elastomeric seal within a peripheral seal retention groove. 
         [0006]    Valves can be mounted in the fluid end of a high-pressure pump incorporating positive displacement pistons or plungers in multiple cylinders. Such valves typically experience high pressures and repetitive impact loading of the valve body and valve seat. These severe operating conditions have in the past often resulted in leakage and/or premature valve failure due to metal wear and fatigue. In overcoming such failure modes, special attention is focused on valve sealing surfaces (contact areas) where the valve body contacts the valve seat intermittently for reversibly blocking fluid flow through a valve. 
         [0007]    Valve sealing surfaces are subject to exceptionally harsh conditions in exploring and drilling for oil and gas, as well as in their production. For example, producers often must resort to “enhanced recovery” methods to insure that an oil well is producing at a rate that is profitable. And one of the most common methods of enhancing recovery from an oil well is known as fracturing. During fracturing, cracks are created in the rock of an oil bearing formation by application of high hydraulic pressure. Immediately following fracturing, a slurry comprising sand and/or other particulate material is pumped into the cracks under high pressure so they will remain propped open after hydraulic pressure is released from the well. With the cracks thus held open, the flow of oil through the rock formation toward the well is usually increased. 
         [0008]    The industry term for particulate material in the slurry used to prop open the cracks created by fracturing is the propend. And in cases of very high pressures within a rock formation, the propend may comprise extremely small aluminum oxide spheres instead of sand. Aluminum oxide spheres may be preferred because their spherical shape gives them higher compressive strength than angular sand grains. Such high compressive strength is needed to withstand pressures tending to close cracks that were opened by fracturing. Unfortunately, both sand and aluminum oxide slurries are very abrasive, typically causing rapid wear of many component parts in the positive displacement plunger pumps through which they flow. Accelerated wear is particularly noticeable in plunger seals and in the suction (i.e., intake) and discharge valves of these pumps. 
         [0009]    A valve (comprising a valve body and valve seat) that is representative of an example full open design valve and seat for a fracturing plunger pump is schematically illustrated in  FIG. 3 . The valve of  FIG. 3  is shown in the open position. For each valve, back pressure tends to close the valve when downstream pressure exceeds upstream pressure. For example, when valve is used as a suction valve, back pressure is present on the valve during the pump plunger&#39;s pressure stroke (i.e., when internal pump pressure becomes higher than the pressure of the intake slurry stream. During each pressure stroke, when the intake slurry stream is thus blocked by a closed suction valve, internal pump pressure rises and slurry is discharged from the pump through a discharge valve. For a discharge valve, back pressure tending to close the valve arises whenever downstream pressure in the slurry stream (which remains relatively high) becomes greater than internal pump pressure (which is briefly reduced each time the pump plunger is withdrawn as more slurry is sucked into the pump through the open suction valve). 
         [0010]    Typically the motion of the valve body is controlled by valve guide legs attached to the bottom or upstream side of the valve body as shown in  FIG. 3 . Unfortunately these guide legs are another source of accelerated valve and seat failure when pumping high sand slurry concentrations.  FIG. 4A  illustrates an old style valve design, circa 1970, in which the valve legs are forged into the upstream side of the valve body; typical of a Mission Service Master I design.  FIG. 4B  illustrates the slurry flow patterns around the leg; as can be seen in the figure, the downstream side of the legs generates considerable turbulence in the flow. The swirling turbulence in the sand slurry used in typical fracturing work results in sever abrasion of the metal valve body and the elastomeric insert seal, which quickly damages the seal, resulting in seal failure. Once the seal fails on the valve insert, the high pressure fluid on the downstream side of the valve escapes through the seal failure to the low pressure upstream side of the valve. Travelling from the very high pressure to the very low pressure side of the valve results in extreme velocities of the sand slurry, which rapidly erodes the metal valve body and the guide legs in the slurry&#39;s path; many times destroying the entire valve leg. Engineers typically recognize the beginning of this failure by four (4) erosion marks behind each leg on worn valves removed from the pump just prior to catastrophic failure in which one or more of the valve legs are completely destroyed by the high pressure erosion. The abraded seal and erosion of the metal valve body are also illustrated in  FIG. 4B . 
         [0011]    The development of the Roughneck valve design, circa 1983, and later the Mission Service Master II valve or the Novatech valve shown in  FIG. 5A  greatly improved the flow behind the legs. These designs featured streamlined legs which were achieved by inertia welding an investment guide leg casting to the valve body forging. The streamlined legs and the open area below the valve body and downstream of the guide legs eliminated much of the turbulence behind the guide legs. However in severe pumping environments with high pump rates and high slurry concentrations the problem described in the previous paragraph still existed as evidenced by the four (4) erosion marks and destroyed guide legs.  FIG. 5B  is a picture a valve of the prior art damaged by seal failure and severe erosion behind the guide legs. 
         [0012]    The most obvious solution to the problem described above is the removal of the guide legs and somehow guide the motion of the valve by other means. Historically many attempts have been made utilizing top stem valves, illustrated in  FIGS. 6A and 6B .  FIG. 6A  illustrates a cross section of a fluid end showing the fluid chamber, the suction fluid chamber and the discharge fluid chamber illustrated in  FIG. 6B . However top stem design valves are inherently unstable in the open position, particularly the discharge valve in the discharge fluid chamber. Once pushed off center by hydraulic flow as illustrated in  FIG. 7 , the forces on the discharge valve tend to push the valve further off center. As the valve continues its cyclic repeating opening and closing, the sliding forces cause rapid and accelerating wear on the top stem guide. 
         [0013]      FIG. 6B  is a partial cross-section schematically illustrating fluid chamber of  FIG. 6A  in its closed position (i.e., with peripheral elastomeric seal held in symmetrical contact with valve seat by discharge valve spring). Note that top guide stem of discharge valve body is aligned in close sliding contact with top valve stem guide. 
         [0014]      FIG. 8  schematically illustrates how misalignment of top guide stem is possible with excessive wear of top valve stem guide. Such excessive wear can occur because discharge valve body, including top guide stem, is typically made of steel that has been carburized to a hardness of about 60 Rockwell C. In contrast, the female guide for the top stem discharge valve, which is shown in  FIG. 6B , is usually integral within discharge cover, is typically made of mild alloy steel with a hardness of about 30 Rockwell C. Thus the softer wall of the stem guide is worn away by sliding contact with the harder guide stem. This wear is accelerated by side loads on valve body that result when fluid flowing past the valve body changes its direction of flow into the discharge manifold. Eventually, top valve stem guide can be worn sufficiently to allow discharge valve leakage due to significant asymmetric contact of elastomeric seal with valve seat as schematically illustrated in  FIG. 8 . 
         [0015]    The change of direction of the fluid and the generated side loads is most severe for the discharge valve where the fluid must make a 90 degree change of direction into the discharge manifold immediately after the fluid exits the seat as shown by the heavy dashed lines in  FIG. 7 . Because the fluid must take the most direct path and the path with least obstructions, most of the fluid flows through one side of the valve as shown in  FIG. 8 . 
         [0016]    The problem of stem guide wear is typically addressed in practice through use of a replaceable bushing having a modified top valve stem guide (see the schematic illustration in  FIG. 9 ). Bushing is commonly made of a plastic such as urethane, or a wear and corrosion-resistant metal such as bronze. Such bushings require periodic checking and replacement, but these steps may be overlooked by pump mechanics until a valve fails prematurely. 
         [0017]    When the open valve is badly misaligned and the valve guide is badly worn there are not aligning forces available to properly align the valve as it closes. Thus the valve will close against the seat in a miss-aligned or cocked position as shown in  FIG. 8 . In this position, the cocked valve leaves an extrusion gap that results in shorten valve insert seal life. The cocked valve also results in uneven loading of the metal valve body against the seating surface of the seat resulting in accelerated metal wear on the valve body and seat. 
       SUMMARY OF THE INVENTION 
       [0018]    The present invention addresses the problem of instability in top stem guided valves due to non-symmetrical flow around the discharge valve which shortens valve life. The present invention restores symmetrical flow around the discharge valve by utilizing a multiple port discharge manifold. 
         [0019]    In a representative embodiment of the disclosure, a positive displacement pump fluid end comprises at least one discharge fluid chamber, and the discharge fluid chamber further comprises a plunger bore, a discharge valve seat, a discharge valve; a suction fluid chamber and at least two discharge manifold ports on opposite sides of said fluid chamber. Fluid is discharged through the discharge seat by the forward stroke of a plunger in said plunger bore, and the flow of said discharged fluid is diverted around said discharge valve in a substantially uniform flow pattern to exit said fluid end through said at least two discharge manifold ports. At least one embodiment discloses the discharge fluid chamber being offset from the suction fluid chamber to increase the wall thickness around the discharge manifold connection on the side of the fluid end. 
         [0020]    A representative fluid end housing comprising a dual port discharge manifold in accordance with embodiments of the invention is illustrated in  FIGS. 10 ,  11 ,  12 A,  12 B,  12 C,  12 D and  13 . Said dual port manifold connects adjacent discharge fluid chambers to channel discharge flow from the fluid end to one or more connections on the side of the fluid end.  FIG. 11  illustrates how the dual port manifold restores symmetrical flow around the valve to increase valve performance. Symmetrical flow eliminates the forces that cause valve cocking and miss-alignment that shortens valve life. All plungers in the fluid end are arranged in a common plane defined by the crankshaft and crossheads in the power end of the pump. Various embodiments of the disclosure show different connections from the discharge manifold on each side of the fluid end housing. 
         [0021]    Because the fluid chamber around the suction valve, is basically cylindrical, there is no change of direction in fluid flow immediately above the suction valve; flow through the valve and seat remains symmetrical, thus there is very little cocking or miss-alignment of the suction valve. In the area well above the suction valve, the fluid changes direction to enter the plunger bore, however this area is of such distance from the suction valve that the change of direction in the fluid flow does not affect the flow through the suction valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a cross-sectional schematic view of a typical plunger pump fluid section showing its connection to a power section by stay rods. 
           [0023]      FIG. 2  schematically illustrates a conventional Triplex plunger pump fluid section housing. 
           [0024]      FIG. 3  schematically illustrates a cross-section of a typical high-pressure pump valve comprising a valve body and a corresponding valve seat. 
           [0025]      FIG. 4A  schematically illustrates a valve body design in which the legs are forged into the main valve body. 
           [0026]      FIG. 4B  schematically illustrates the valve of  FIG. 4A  and the flow turbulence around the guide legs. 
           [0027]      FIG. 5A  schematically illustrates a current state of the art valve design in which the guide legs are a streamlined investment casting to provide improved fluid flow. 
           [0028]      FIG. 5B  is a picture of an actual valve of a design schematically illustrated in  FIG. 5A  and the erosion damage due to turbulent fluid flow. 
           [0029]      FIG. 6A  schematically illustrates a cross-section of a right-angular plunger pump having a top stem guided suction valve and a top stem guided discharge valve. 
           [0030]      FIG. 6B  is a partial cross-section schematically illustrating detail “B-B” of  FIGS. 6A . 
           [0031]      FIG. 7  schematically illustrates the flow around the discharge valve body of  FIGS. 6A and 6B ; valve in the open position. 
           [0032]      FIG. 8  schematically illustrates improper closure of the discharge valve of  FIGS. 6A and 6B  due to misalignment of the top guide stem. 
           [0033]      FIG. 9  schematically illustrates a replaceable bushing in a modification of the top valve stem guide shown in  FIG. 7 . 
           [0034]      FIG. 10  schematically illustrates an embodiment of a fluid end assembly with top-stem-guided valves and a dual port discharge manifold made according to the present invention. 
           [0035]      FIG. 11  schematically illustrates the discharge valve in the open position and the symmetrical fluid flow around the discharge valve in the discharge fluid chamber of the fluid end of  FIG. 10 . 
           [0036]      FIG. 12A  schematically illustrates a cross-section of a right-angular fluid end housing of  FIG. 10 . 
           [0037]      FIG. 12B  schematically illustrates the sectional view labeled B-B in  FIG. 12A . 
           [0038]      FIG. 12C  schematically illustrates an alternate embodiment shown as the sectional view labeled C-C in  FIG. 12A . 
           [0039]      FIG. 12D  schematically illustrates an alternate embodiment shown as the sectional view labeled D-D in  FIG. 12A . 
           [0040]      FIG. 13  schematically illustrates an alternate embodiment in which the discharge fluid chamber is offset from the suction fluid chamber. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]      FIG. 10  schematically illustrates a cross-section of a right-angular plunger pump fluid end  10  of the present invention. Fluid end assembly composes a fluid end housing  15  with a central fluid chamber  1  which has a discharge fluid chamber  2  and a suction chamber  3 , wherein discharge fluid chamber  2  contains a discharge valve and seat assembly  20 . Said discharge valve and seat assembly includes discharge seat  21 , discharge valve  22 , discharge spring  23 , and discharge cover guide  25 . Similarly suction fluid chamber  3  contains a suction valve and seat assembly  30  composed of suction seat  31 , suction valve  32 , suction spring  33 , and suction spring retainer guide  35 . Discharge chamber  2  centerline  12  is collinear with suction chamber centerline  13  in the first embodiment. Central fluid chamber  1  also contains a plunger bore  40  and associated plunger  41 ; plunger bore  40  and plunger  41  are concentric to plunger centerline  14 . 
         [0042]    Additionally  FIG. 10  illustrates discharge fluid chamber  2  which is connected to adjacent discharge fluid chambers  102 ,  202  and any additional fluid chambers by dual port discharge manifolds  60  and  70  spaced on opposite sides of fluid chamber  2 . Discharge manifold  60  is proximal to the pump power end and discharge manifold  70  is distal to the pump power end. Adjacent discharge fluid chambers  102  and  202  are illustrated in  FIGS. 12B ,  12 C, and  12 D. Centerlines of dual port discharge manifolds  60  and  70  are perpendicular to the axis of the plunger bore  40  and parallel to the plane formed by the respective centerlines of all the plungers in fluid end  10 . 
         [0043]      FIG. 12A  schematically illustrates cross sectional view of fluid end housing  15  of fluid end assembly  10  of  FIG. 10 . Fluid end housing  15  comprises distal discharge manifold port  70 , proximal discharge manifold port  60 , central fluid chamber  1 , discharge fluid chamber  2 , suction fluid chamber  3 , and plunger bore  40 , defined by plunger bore centerline  14 . 
         [0044]      FIGS. 12B ,  12 C, and  12 D illustrate discharge fluid chambers  2 ,  102 , and  202  and adjacent plunger bores  40 ,  140 , and  240  respectfully of a multi-plunger pump arranged in a plane defined by plunger bore centerlines  14 ,  114 , and  214  respectfully. Said plane is collinear with the plane defined by the pump power end crankshaft and crossheads. Said adjacent plunger bores contain adjacent plungers  141  and  242  (not shown.) 
         [0045]      FIG. 12B  schematically illustrates top sectional view of first embodiment of this invention in which fluid end block  15  is fitted with a distal discharge manifold port  60  and a proximal discharge manifold port  70 . Each port being blind bored from opposite sides  18  and  19  of fluid end block  15 . Distal port  60  and proximal port  70  each have a connection  61  and  71  respectfully at the exit of the respective ports  60  and  70  to connect the discharge flow of the pump to external piping. Connections  61  and  71  can be a threaded type connection as shown or the connection maybe a bolt-on flange type connection, not shown. Flange connections typical have male or female WECO style union connections for connecting downstream piping. 
         [0046]      FIG. 12C  schematically illustrates top sectional view a second embodiment of this invention in which fluid end block  16  is fitted with a distal port  80  and a proximal port  90 . Each port being through bored into fluid end block  16 . Distal port  80  has dual connections  81  and  82  on opposite sides  18  and  19  of fluid end housing to connect the discharge flow to external piping. Similarly proximal port  90  has dual connections  91  and  92  on opposite sides  18  and  19  of fluid end housing to connect the discharge flow to external piping. 
         [0047]      FIG. 12D  schematically illustrates top sectional view of third embodiment of this invention in which fluid end block  17  is fitted with a distal port  60  and a proximal port  50 . Each port being blind bored from the same side of fluid end block  17 ; either side  18  or  19 . Illustrated in this figure, distal port  60  and proximal port  50  each have a connection  61  and  51  respectfully on side  18  of the fluid end housing  17  at the exit of the respective ports  60  and  50  to connect the discharge flow to external piping. 
         [0048]      FIG. 13  schematically illustrates an fourth embodiment of the cross-section of a right-angular plunger pump fluid end  10 ′ of the present invention. Fluid end assembly composes a fluid end housing  15 ′ with a central fluid chamber  1 ′ which has a discharge fluid chamber  2 ′ and a suction chamber  3 , wherein discharge fluid chamber  2 ′ contains a discharge valve and seat assembly  20 . Said discharge valve and seat assembly includes discharge seat  21 , discharge valve  22 , discharge spring  23 , and discharge cover guide  25 . Similarly suction fluid chamber  3  contains a suction valve and seat assembly  30  composed of suction seat  31 , suction valve  32 , suction spring  33 , and suction spring retainer guide  35 . Central fluid chamber  1  also contains a plunger bore  40  and associated plunger  41 ; plunger bore  40  and plunger  41  are concentric to plunger centerline  14 . 
         [0049]    Discharge fluid chamber  2 ′ illustrated in  FIG. 13  is connected to adjacent discharge fluid chambers  102 ′,  202 ′ (not shown) and any additional fluid chambers by dual port discharge manifolds  60 ′ and  70 ′ spaced on opposite sides of fluid chamber  2 ′. Discharge manifold  60 ′ is proximal to the pump power end and discharge manifold  70 ′ is distal to the pump power end. Centerlines of dual port discharge manifolds  60 ′ and  70 ′ are perpendicular to the axis of plunger bore  40  and parallel to the plane formed by the centerlines  14 ,  114 , and  214  of the plunger bores  40 ,  140 ,  240 , and any additional plunger bores respectfully in fluid end  10 ′. Discharge fluid chamber  2 ′, discharge valve and seat assembly  20 , and discharge chamber centerline  12 ′ is offset from suction chamber  3  and suction chamber centerline  13 ; said offset in a direction distal from the pump power end. Discharge chamber centerline  12 ′ is coplanar with suction chamber centerline  13  of the first embodiment, said plane being defined by suction chamber centerline  13  and plunger bore centerline  14 . 
         [0050]    Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.