Patent Publication Number: US-9903480-B2

Title: Poppet valve with integrated dampener

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/183,299 filed Jul. 14, 2011, and entitled “Poppet Valve with Integrated Dampener,” which is hereby incorporated herein by reference in its entirety for all purposes. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     The disclosure relates generally to systems and methods for reducing the creation of pulsations in a fluid passing through a valve. 
     To form an oil or gas well, a bottom hole assembly (BHA), including a drill bit, is coupled to a length of drill pipe to form a drill string. The drill string is then inserted downhole, where drilling commences. During drilling, drilling fluid, or “mud,” is circulated down through the drill string to lubricate and cool the drill bit as well as to provide a vehicle for removal of drill cuttings from the borehole. After exiting the bit, the drilling fluid returns to the surface through the annulus formed between the drill string and the surrounding borehole wall. 
     Instrumentation for taking various downhole measurements and communication devices are commonly mounted within the drill string. Many such instrumentation and communication devices operate by sending and receiving pressure pulses through the annular column of drilling fluid maintained in the borehole. 
     Mud pumps are commonly used to deliver the drilling fluid to the drill string during drilling operations. Many conventional mud pumps are reciprocating pumps, having one or more piston-cylinder assemblies driven by a crankshaft and hydraulically coupled between a suction manifold and a discharge manifold. Each piston-cylinder assembly has a piston housed within a cylinder. A suction valve positioned between the cylinder and the suction manifold is operable to control the flow of drilling fluid from the suction manifold into the cylinder. Likewise, a discharge valve positioned between the cylinder and the discharge manifold is operable to control the flow of drilling fluid from the cylinder to the discharge manifold. 
     During operation of the mud pump, the piston is driven to reciprocate within the cylinder. As the piston moves to expand the volume within the cylinder, the discharge valve is closed, and drilling fluid is drawn from the suction manifold through the suction valve into the cylinder. After the piston reverses direction, the volume within the cylinder decreases, the pressure of drilling fluid contained with the cylinder increases, the suction valve closes, and the now-pressurized drilling fluid is exhausted from the cylinder through the discharge valve into the discharge manifold. While the mud pump is operational, this cycle repeats, often at a high cyclic rate, and pressurized drilling fluid is continuously fed to the drill string at a substantially constant rate. 
     Many conventional suction and discharge valves are poppet valves, each such valve having a poppet that is movable relative to a valve seat between a seated position, wherein the poppet engages the valve seat to prevent fluid flow through the valve, and an unseated position, wherein the poppet is disengaged from the valve seat and fluid may pass through the valve. When moving between the seated and unseated positions, it is common for the poppet to shiver. As used herein, the expression “shiver” refers to the unstable movement of the poppet caused at least in part by forces exerted on the poppet from fluid passing around the poppet through the valve. 
     Shivering creates pulsations in the drilling fluid that may disturb the downhole communication devices and instrumentation by degrading the accuracy of measurements taken by the instrumentation and hampering communications between downhole devices and control systems at the surface. Over time, the pulsations may also cause fatigue damage to the drill string pipe and other downhole components. Moreover, when the poppet is proximate the valve seat, shivering results in repeated contact between the poppet and the valve seat. Over time, repeated impact of the poppet against the valve seat causes wear to each component that shortens their service life. 
     Accordingly, there is a need for a poppet valve that is configured to reduce, or eliminate, shivering. 
     SUMMARY 
     A poppet valve with an integrated dampener is disclosed. In some embodiments, the poppet valve, or valve assembly, includes a poppet guide and a hollow poppet. The poppet guide has a stem. The poppet guide stem is received within the poppet, thereby defining an internal cavity. The poppet is moveable relative to the poppet guide to adjust the volume of the internal cavity. 
     In some embodiments, the valve includes a poppet, a poppet guide, and a poppet guide pivot system. The poppet guide pivot system engages the poppet guide and has an axial centerline. The poppet guide pivot system enables pivoting to the poppet guide about the axial centerline. The poppet receives an end of the poppet guide therein and is pivotable with the poppet guide. 
     In some embodiments, the valve has a poppet for engagement with a valve seat. The poppet is moveable relative to the valve seat between a seated position, wherein the valve poppet engages the valve seat, and an unseated position, wherein the valve poppet is disengaged from the valve seat. The poppet includes a poppet body having an outer surface with a seal groove formed therein and an elastic seal disposed within the seal groove. The seal engages the valve seat prior to the poppet body when the poppet moves toward the seated position. 
     Thus, embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with conventional poppet valves. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, and by referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of the disclosed embodiments, reference will now be made to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a pump including a plurality of valves in accordance with the principles disclosed herein; 
         FIGS. 2A and 2B  are perspective views of the pump of  FIG. 1  in the absence of the piston-cylinder assemblies, illustrating the valve blocks; 
         FIG. 3  is a cross-sectional view of a valve block, illustrating the suction and discharge valve assemblies disposed therein; 
         FIG. 4  is an enlarged axial cross-sectional view of the suction valve assembly of  FIG. 3 ; and 
         FIG. 5  is a perspective axial cross-sectional view of the poppet and valve seat of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
     The following description is directed to exemplary embodiments of a poppet valve with an integrated dampener. The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. One skilled in the art will understand that the following description has broad application, and that the discussion is meant only to be exemplary of the described embodiments, and not intended to suggest that the scope of the disclosure, including the claims, is limited only to those embodiments. 
     Certain terms are used throughout the following description and the claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. Moreover, the drawing figures are not necessarily to scale. Certain features and components described herein may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in interest of clarity and conciseness. 
     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, the connection between the first device and the second device may be through a direct connection, or through an indirect connection via other intermediate devices and connections. Further, the terms “axial” and “axially” generally mean along or parallel to a central or longitudinal axis. The terms “radial” and “radially” generally mean perpendicular to the central or longitudinal axis, while the terms “azimuth” or “azimuthally” generally mean perpendicular to the central or longitudinal axis and a radial axis normal to the central or longitudinal axis. As used herein, the terms are consistent with their commonly understood meanings with regard to a cylindrical coordinate system. 
     Referring now to  FIG. 1 , there is shown a pump  100  including a plurality of valves in accordance with the principles disclosed herein. The pump  100  is operable to pressurize a working fluid, such as but not limited to drilling mud, to a desired pressure. The working fluid is drawn from a suction manifold (not shown) through a pump inlet  105  into the pump  100 , pressurized by the pump  100 , and discharged from the pump  100  through a pump outlet  110  into a discharge manifold (not shown). 
     In the illustrated embodiment, the pump  100  is a hex pump, having six piston-cylinder assemblies  115  driven by a common axial cam (not shown). Each piston-cylinder assembly  115  is coupled to a valve block  120 . Further, each piston-cylinder assembly  115  includes a piston movably disposed within a cylinder and coupled to the axial cam. During operation of the pump  100 , the axial cam rotates, causing the pistons to translate, or reciprocate, within their respective cylinders. 
     Turning to  FIGS. 2A and 2B , which depict the pump  100  in the absence of the piston-cylinder assemblies  115 , each valve block  120  has an internal cavity  122 . The valve block  120  also has a cylinder port  130  in fluid communication with the cylinder of the associated piston-cylinder assembly  115 , a suction port  135  in fluid communication with the pump inlet  105 , and a discharge port  140 , located on the base of the valve block  120 , in fluid communication with the pump outlet  110 . The cylinder port  130 , suction port  135 , and discharge port  140  are in fluid communication with the internal cavity  122 . 
     The pump  100  further includes a suction valve assembly  145  and a discharge valve assembly  150  disposed within the internal cavity  122  of each valve block  120 . The region of the internal cavity  122  disposed between the suction valve assembly  145 , the discharge valve assembly  150 , and the cylinder defines a pumping chamber  125  ( FIG. 3 ). The suction valve assembly  145  is operable to control the flow of working fluid from the pump inlet  105  into the pumping chamber  125 . The discharge valve assembly  150  is operable to control the flow of pressurized working fluid from the pumping chamber  125  to the pump outlet  110 . 
       FIG. 3  depicts a cross-section of one valve block  120 , bisecting the suction valve assembly  145  and the discharge valve assembly  150  disposed therein along their axial centerlines. As previously described, the suction valve assembly  145  is disposed within the valve block internal cavity  122  to control the flow of working fluid from the pump inlet  105  through the suction port  135  of the valve block  120  into the pumping chamber  125 . The discharge valve assembly  150  is disposed within valve block internal cavity  122  to control the flow of pressurized working fluid from the pumping chamber  125  through the discharge port  140  (located behind the discharge valve assembly  150  in this view) of the valve block  120  to the pump outlet  110 . In the illustrated embodiment, the suction valve assembly  145  and the discharge valve assembly  150  are substantially identical, both in structure and in operation. In the interest of brevity, only the suction valve assembly  145  will be described in detail. However, its description is also applicable to the discharge valve assembly  150 . 
     The suction valve assembly  145  includes a valve cover assembly  200 , a retainer  205 , a poppet guide pivot system  210 , a poppet guide  215 , a snap ring assembly  220 , a poppet spring  225 , a washer  227 , a tolerance ring  230 , a poppet  235 , and a valve seat  240 . As its name implies, the retainer  205  retains the remaining components of the suction valve assembly  145  except the valve cover assembly  200  within the valve block internal cavity  122 . The retainer  205  has an enlarged outer end  255 , defined relative to the outer surface of the valve block  120 , that shoulders against the outer surface of the valve block  120  to limit the position of the retainer  205  relative to the valve block  120 . The valve cover assembly  200  is coupled to the end  255  of the retainer  205 . 
     Referring next to  FIG. 4 , which is an enlarged view of the suction valve assembly  145 , the inner end  260  of the retainer  205  includes a telescoping recess  265  having a diameter that varies with its depth. The deepest portion  270  of the recess  265  has a diameter adapted to receive the poppet guide pivot system  210  with negligible radial clearance therebetween, as shown. The shallowest portion  275  of the recess  265  has a diameter adapted to receive the poppet guide  215 , leaving both radial clearance  280  and axial clearance  285  between the poppet guide  215  and the retainer  205 . As will be described below, clearances  280 ,  285  enable limited pivotal movement of the poppet guide  215  relative to the retainer  205 . The intermediate portion  277  of the recess  265  has a diameter adapted to provide radial clearance between the poppet guide pivot system  210 . 
     To prevent the loss of working fluid from the pumping chamber  125 , the retainer  205  further includes one or more annular grooves  290  formed in its outer surface and a sealing member  295  seated in each. In some embodiments, the sealing member  295  is an O-ring. The sealing members  295  sealingly engage the interior surface of the valve block  120  bounding the pumping chamber  125  to limit or prevent working fluid from passing between the suction valve assembly  145  and the valve block  120 . 
     The poppet guide pivot system  210  enables pivoting of the poppet guide  215  relative to the axial centerline of the retainer  205 . In the illustrated embodiment shown in  FIG. 4 , the poppet guide pivot system  210  is seated in the retainer recess  265 . The poppet guide pivot system  210  includes an outer ring  300 , an inner ring  305 , a threaded bolt  310 , and a wave spring  315 . The outer ring  300  is seated within the retainer recess portion  270 . The inner ring  305  is disposed within retainer recess portion  277  adjacent to and engaging the outer ring  300 . There is negligible radial clearance between the outer ring  300  and the retainer  205 . Hence, the outer ring  300  is prevented from appreciable radial movement relative to the retainer  205 . No portion of the inner ring  305  is received within retainer recess  270 . Thus, radial and/or azimuthal movement of the inner ring  305  is not limited by the retainer shoulder surrounding recess portion  270 . The outer ring  300  includes a concave surface  320  abutting the inner ring  305 . The inner ring  305  includes a convex surface  325  abutting the outer ring  300 . These surfaces  320 ,  325  have mirrored curvatures that enable the inner ring  305  to move relative to the outer ring  300 . Moreover, radial clearance between the retainer  205  and the inner ring  305  enables movement of the inner ring  305  relative to the outer ring  300 . 
     The wave spring  315  is disposed about the bolt  310  between the head of the bolt  310  and the inner ring  305 . The bolt  310  is threaded into a bore  335  in the retainer  205  to secure the poppet guide pivot system  210  to the retainer  205 . When installed as shown, the wave spring  315  expands to maintain the outer and inner rings  300 ,  305  in engagement. Consequently, the inner ring  305  is moveable or slideable against the outer ring  300 . 
     In an alternative embodiment, the poppet guide pivot system  210  may include an elastic ring (not shown) disposed between the retainer  205  and the poppet guide  215 . The elastic ring is compressible under load and expandable when the load is reduced or removed. Localized compression and expansion of the ring enables the poppet guide  215  to pivot about the axial centerline of the retainer  205 . 
     The snap ring assembly  220  is disposed between the poppet guide  215  and the retainer  205 , and maintains the poppet guide  215  in engagement with the poppet guide pivot system  210 . The snap ring assembly  220  includes an outer snap ring  340  connected to the poppet guide  215 , an inner snap ring  345  connected to the retainer  205 , and a spring  350  disposed therebetween. The spring  350  is axially compressible and expandable against the snap rings  340 ,  345 . Expansion of the spring  350  against the outer snap ring  340  causes the poppet guide  215  to remain engaged with the inner ring  305 . 
     As described above, the inner ring  305  of the poppet guide pivot system  210  is movable against the outer ring  300 , and the poppet guide  215  is seated against the inner ring  305 . The ability of the inner ring  305  to move relative to the outer ring  300  and clearances  280 ,  285  between the poppet guide  215  and the retainer  205  enable the poppet guide  215  to pivot about the retainer axial centerline. Depending on its direction of pivot, the spring  350  experiences localized compression in some regions between the snap rings  340 ,  345  and localized expansion in other regions between the snap rings  340 ,  345 . Subsequent movement of the poppet guide  215  again causes the spring  350  to experience localized compression and expansion to allow the poppet guide  215  to pivot as needed. Thus, the snap ring assembly  220  enables an elastic coupling between the poppet guide  215  and retainer  205 . 
     The poppet guide  215  includes a guide base  360  and a stem  365  extending axially therefrom. The guide base  360  is seated against the inner ring  305  of the poppet guide pivot system  210 . The stem  365  is received within the poppet  235  with negligible radial clearance therebetween and aligns the poppet  235  such that the axial centerline of the poppet  235  aligns with the axial centerline of the stem  365 . When the poppet  235  pivots relative to the axial centerline of the valve seat  240 , for instance in response to contact with the valve seat  240 , the poppet guide  215  pivots similarly due to engagement between the stem  365  and the poppet  235 . 
     The guide base  360  includes an annular recess  370  about the base of the stem  365  and a concave surface  375  extending therefrom. The curvature of the concave surface  375  enables working fluid bypassing the poppet  235  to be directed toward the discharge valve assembly  150  in a manner that minimizes the creation of turbulence within the fluid. (The corresponding surface  375  on the discharge valve assembly  150  directs pressurized working fluid toward the discharge outlet  140  of the valve block  120 .) 
     The annular recess  370  receives an end of the poppet spring  225 . A shoulder  380  of the guide base  360  bounding the annular recess  370  retains the end of the spring  225  proximate the stem  365 . The opposing end of the poppet spring  225  abuts an annular washer  227  seated against the poppet  235 . The poppet spring  225  is expandable and compressible between the guide base  360  and the washer  227  and therefore between the poppet guide  215  and the poppet  235 . Expansion and compression of the poppet spring  225  enables axial movement of the poppet  235  relative to the poppet guide  215 . Further, the poppet spring  225  biases the poppet  235  to the seated position against the valve seat  240 . When the force exerted on the poppet  235  by working fluid upstream of the suction valve assembly  145  exceeds the force exerted on the poppet  235  by the poppet spring  225  and working fluid in the pumping chamber  125 , the poppet  235  moves axially toward the poppet guide  215 , compressing the spring  225 . Conversely, when the force exerted on the poppet  235  by working fluid upstream of the suction valve assembly  145  is less than the force exerted on the poppet  235  by the poppet spring  225  and working fluid in the pumping chamber  125 , the poppet  235  moves axially away from the poppet guide  215 , allowing the spring  225  to expand. 
     The guide base  360  further includes an annular groove  385  in its outer surface, radially speaking. The tolerance ring  230  is seated within the groove  385 . The tolerance ring  230  is radially compressible under load and expandable in the absence of load. When the poppet guide  215  pivots, as previously described, the tolerance ring  230  experiences localized compression, depending on the direction of pivot, due to contact with the valve block  120 . When the poppet guide  215  pivots again and the localized compression loads to the tolerance ring  230  are removed, the tolerance ring  230  expands and returns to its unloaded shape. The elastic nature of the tolerance ring  230  reduces wear to the poppet guide  215  that may otherwise occur in the absence of the tolerance ring  230 . Moreover, the tolerance ring  230  enables centering of the poppet guide  215  and the poppet  235  coupled thereto within the internal cavity  122  of the valve block  120 . 
     The valve seat  240  is an annular member disposed within the valve block cavity  122  in abutment with a shoulder  450  of the valve block  120 . The valve seat  240  includes a converging inner surface  455  and a diverging inner surface  460 . The converging surface  455  directs working fluid from the suction port  135  of the valve block  120  toward the poppet  235 . The diverging surface  460  promotes the flow of the working fluid around the poppet  235  when the poppet  235  is unseated, meaning disengaged from the valve seat  240 . The diverging surface  460  is also that portion of the valve seat  240  that engages the poppet  235  when the poppet  235  is seated, or engaged with the valve seat  240 . Consequently, the diverging surface  460  is shaped to promote effective sealing with the poppet  235 . 
     As best viewed in  FIG. 5 , the poppet  235  includes a poppet body  245  with a seal  250  disposed thereabout. In some embodiments, the poppet body  245  comprises at least one of heat treated steel and heat treated stainless steel. The poppet body  245  has a hollow head  400  and a tubular stem  405  extending therefrom. The hollow head  400  enables a reduced wall thickness of the poppet body  245 . The reduced wall thickness, in turn, enables the poppet body  245  to be flexible and respond elastically to impacts with the valve seat  240 . This reduces wear to both the poppet  235  and the valve seat  240  that would otherwise occur if the poppet  235  were more rigid, as is the case for many conventional poppet valves. Consequently, the flexible nature of the poppet body  245  promotes increased services lives for the poppet  235  and the valve seat  240 . Further, the head  400  has a somewhat conically-shaped outer surface  410  and a seal groove  415  formed therein. The outer surface  410  is shaped to promote effective sealing with the valve seat  240  and to enable smooth fluid flow around the poppet  235  when unseated with minimal turbulence creation. In the exemplary embodiment shown in  FIG. 5 , the diverging surface  460  of valve seat  240 , as well as the portion of outer surface  410  of head  400  that comes into engagement with surface  460 , is substantially planar when viewed in cross-section. However, these surfaces  410 ,  460  may be curved in other embodiments. 
     The groove  415  receives the seal  250  therein. The surface of the poppet head  400  bounding the groove  415  forms a protrusion  435  that extends radially into the groove  415  and has a curved “bowl-shaped” or concave portion  437 . The groove  415  has an inner portion  422  and an outer portion  425  defined by a radial plane  430  that substantially bisects the protrusion  435 . For reasons described below, the groove  415  is sized such that the outer portion  425  has a volume exceeding that of the inner portion  422 . In some embodiments, the volume of the outer portion  425  is 4% greater than that of the inner portion  422 . 
     The seal  250  comprises a flexible resilient or elastic material, such as but not limited to polyurethane and/or rubber. The dimensions of the seal  250  are selected such that when the poppet  235  displaces toward the valve seat  240 , such as to close the suction valve assembly  145 , the seal  250  contacts the valve seat  240  before any portion of the poppet body  245 . In the exemplary embodiment, the seal  250  has a radially extending protrusion, or bulge,  252  adjacent a reduced diameter, or recessed, portion  254 . The bulge  252 , which extends radially beyond the poppet head  400 , is the portion of the seal  250  that makes the initial contact with the valve seat  240 , as shown. Initial contact by the seal  250  with the valve seat  240  enables the seal  250  to compress to a degree and movement of the poppet  235  to be slowed before the poppet head  400  engages the valve seat  240 , both of which comprise material that is more rigid than that of the seal  250 . Slowing the poppet  235  in this manner before the poppet head  400  engages the valve seat  240  reduces the impact force between the valve seat  240  and the poppet head  400 . This, in turn, reduces wear to these components  240 ,  400  and enables them to have longer service lives. 
     Continued movement of the poppet  235  against the valve seat  240  causes the seal  250  to further compress within the groove  415 . Compression of the seal  250  is promoted by the shape of the seal  250 , in particular the reduced diameter portion  254 , and the seal groove  415 . As previously described, the outer portion  425  of the groove  415  has a volume exceeding that of the inner portion  422 . As the poppet  235  moves against the valve seat  240 , localized compression of the seal  250  occurs proximate the valve seat  240 . The material of the seal  250  behaves like a very viscous fluid when exposed to high pressure. Consequently, when the seal  250  experiences localized compression due to contact with the valve seat  240 , some seal material in the inner portion  422  flows into the larger outer portion  425 . In contrast, conventional seal grooves cannot accommodate this shifting of seal material under compression. As a result, the seal material, with nowhere to move, stretches, rather than compresses, and overtime experiences fatigue damage. The “bowl-shaped” or concave curvature of the portion  437  of the poppet head surface bounding the seal groove  415  further promotes compression of the seal  250  by directing the seal material into the interior of the seal groove  415 . 
     During manufacturing of the poppet  235 , a lubricant may be applied to a portion of the surface of the poppet body  245  bounding the seal groove  415 , such as but not limited to the protrusion  435 . The elastic seal material is then poured into the seal groove  415 . After solidification of the seal material, the seal  250  adheres to the surface of the poppet body  245  except over the lubricated protrusion  435 . Thus, the seal  250  is unattached to the protrusion  435  of the poppet body  245 . When the seal  250  engages the valve seat  240  during operation of the suction valve assembly  145 , the seal  250  bends and compresses around the protrusion  435 , but does not pull and stretch due to attachment with the protrusion  435 . 
     The poppet stem  405  receives the poppet guide stem  365  therein, defining an internal cavity  420  between the poppet guide stem  365  and the inner surface of the poppet  235 . The poppet stem  405  has one or more radial ports  475  extending therethrough. Additionally, the poppet stem  405  has one or more axial channels  480  along its inner surface. The radial ports  475  and axial channels  480  enable fluid communication between the pumping chamber  125  ( FIG. 4 ) and the internal cavity  420 . When the poppet  235  moves axially toward the valve seat  240  relative to the poppet guide stem  365  ( FIG. 4 ), working fluid flows freely from the pumping chamber  125  through radial ports  475  and axial channels  480  into the internal cavity  420 . Conversely, when the poppet  235  moves axially in the opposite direction, some working fluid in the internal cavity  420  is displaced by the poppet guide stem  365 . The displaced working fluid flows freely from the internal cavity  420  through the axial channels  480  and radial ports  475  into the pumping chamber  125 . 
     The rate of fluid flow into or out of the internal cavity  420  of the poppet  235  is dependent upon the number and cross-sectional size of the radial ports  475  and axial channels  480 . The speed at which the poppet  235  responds to pressure difference, as previously described, and moves relative to the poppet guide  215  is, in turn, dependent upon the rate of fluid into or out of the internal cavity  420 . The greater the number and/or the larger the size of ports  475  and channels  480 , the quicker the poppet  235  responds and moves. Conversely, the fewer the number and/or the smaller then size of ports  475  and channels  480 , the slower the poppet  235  responds and moves. In other words, movement of the poppet  235  is dampened. For this reason, the suction valve assembly  145  may be described as having an integrated dampener. In preferred embodiments, the number and cross-sectional size of the ports  475  and channels  480  are selected to dampen movement of the poppet  235  sufficiently to minimize the creation of pulsations in the working fluid due to poppet movement. At the same time, the number and size of the ports  475  and channels  480  are selected such that the ports  475  and channels  480  do not impede or restrict fluid flow to a degree that causes the working fluid to flow toward the suction module. (In the discharge valve assembly  150 , the number and size of the ports  475  and channels  480  are selected such that the ports  475  and channels  480  do not impede or restrict fluid flow to a degree that causes the working fluid to flow toward the suction module.) 
     During operation of the pump  100 , the pistons reciprocate within their respective cylinders. As each piston strokes back, a vacuum is drawn on the pumping chamber  125  ( FIG. 3 ) of the valve block  120  to which the piston is coupled. Due to the pressure differential between the pumping chamber  125  and working fluid downstream of the discharge valve assembly  150 , the discharge poppet  235  moves axially along the guide poppet  215  toward the valve seat  240 . Movement of the discharge poppet  235  causes working fluid to be drawn through radial ports  475  and axial channels  480  of the discharge poppet  235  into its internal cavity  420 . Due to the size and number of ports  475  and channels  480 , the rate at which fluid flows into the internal cavity  420  is controlled, dampening movement of the poppet  235  in response to fluid passing over the poppet  235  and reducing the tendency for the poppet  235  to shiver as it approaches the valve seat  240 . When the discharge poppet  235  is proximate the valve seat  240 , the seal  250  engages the valve seat  240 , compressing and slowing movement of the poppet  235 . Continued movement of the poppet  235  toward the valve seat  240  further compresses the seal  250 , causing some seal material to flow from the inner portion  422  of the seal groove  415  into the outer portion  425 , until the discharge poppet  235  is seated against the valve seat  240 . The combination of the shape of the valve seat surface  460 , engagement between the discharge poppet stem  405  and the discharge poppet guide stem  365 , and the ability of the discharge poppet guide  215  to pivot, as previously described, enable centering of the discharge poppet  235  against the valve seat  240  to form a complete seal therebetween. In this manner, the discharge valve assembly  150  is closed. 
     Likewise, due to the pressure differential between the pumping chamber  125  ( FIG. 4 ) and fluid upstream of the suction valve assembly  145 , the suction poppet  235  moves axially along the poppet guide  215  away from the valve seat  240 . In response, some working fluid within the internal cavity  420  of the suction poppet  235  is displaced from the internal cavity  420  through the axial channels  480  and radial ports  480  into the pumping chamber  125 . Due to the size and number of ports  475  and channels  480 , the rate at which fluid flows out of the internal cavity  420  is controlled, dampening movement of the poppet  235  in response to fluid passing over the poppet  235  and reducing the tendency for the poppet  235  to shiver as it moves away from the valve seat  240 . Also, as the suction poppet  235  unseats, the seal  250  expands, returning to its uncompressed shape within the seal groove  415 . In this manner, the suction valve assembly  145  is opened. 
     With the discharge valve assembly  150  closed and the suction valve assembly  145  open, working fluid passes from the suction manifold through the pump inlet  105  and the suction port  135  of the valve block  120  around the unseated suction poppet  235  to fill the pumping chamber  125 , including the cylinder. Some of the working fluid passing around the poppet  235  contacts the poppet guide base  360 . Due to the curved shape of the poppet guide surface  375  ( FIG. 4 ), the working fluid is directed toward the discharge valve assembly  150  with minimal turbulence creation. 
     When the piston reaches the end of its stroke, the piston reverses direction and begins to stroke forward. As the piston strokes forward, fluid pressure in the cylinder and the pumping chamber increases. When the force exerted on the suction poppet  235  by fluid in the pumping chamber  125  and the suction poppet spring  225  exceeds the force exerted on the suction poppet  235  by fluid upstream of the poppet  235 , the suction valve assembly  145  closes in an identical manner as that described above in regards to closing of the discharge valve assembly  150 . After the suction valve assembly  145  is closed, the pumping chamber  125  ceases to receive working fluid from the suction manifold. 
     When the force exerted on the discharge poppet  235  by fluid in the pumping chamber  125  exceeds the force exerted on the discharge poppet  235  by fluid downstream of the poppet  235  and the discharge poppet spring  225 , the discharge valve assembly  150  opens in an identical manner as that described above in regards to opening of the suction valve assembly  145 . After the discharge valve assembly  150  is open, pressurized fluid in the pumping chamber  125  flows around the discharge poppet  235  through the discharge port  140  of the valve block  120  and the pump outlet  110  into the discharge manifold. Some of the working fluid passing around the discharge poppet  235  contacts the poppet guide base  360 . Due to the curved shape of the poppet guide surface  375 , the working fluid is directed toward the discharge port  140  with minimal turbulence creation. When the piston reaches the end of its stroke, it again reverses direction, and begins to stroke out, drawing a vacuum on the pumping chamber  125  and so on, as described above. While the pump  100  continues to operate, this process repeats, and pressurized working fluid is exhausted from the pump outlet  110 . 
     Valve assemblies  145 ,  150  with integrated dampeners have been described. In the exemplary embodiments, the valve assembly has the internal cavity  420  that receives and exhausts fluid. The rate at which the fluid enters or leaves the internal cavity  420  dampens movement of the poppet  235  in response to fluid passing over the poppet  235  and reduces the tendency for the poppet  235  to shiver. The poppet  235  has the seal  250  which, during closing of the valve assembly, contacts the valve seat  240  before any portion of the poppet head  400 . Subsequent compression of the seal  250  slows movement of the poppet  235  and reduces impact forces between the poppet head  400  and the valve seat  240 . This, in turn, reduces wear to these components  240 ,  400 , enabling them to have longer service lives. The poppet  235  also has the seal groove  415  which is shaped to enable compression, rather than stretching, of the seal  250  during contact with the valve seat  240 . This prevents fatigue damage to the seal  250 . The valve assembly poppet guide  215  is pivotable. This promotes centering of the poppet  235  against the valve seat  240 , which enables effective sealing between these components and complete closure of the valve assembly. The curved shape of the poppet guide base  360  directs the flow of working fluid through the valve assembly with minimal turbulence creation that would otherwise generate pulsations in the fluid. 
     While various embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings herein. The embodiments herein are exemplary only, and are not limiting. Many variations and modifications of the apparatus disclosed herein are possible and within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.