CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application Serial No. 62/812,518 filed March 1 , 2019, and entitled "Valve Seat Assembly For Well Service Pumps," and of U.S. provisional patent application Serial No. 62/874,324 filed July 15, 2019, and entitled "Valve Seat Assembly For Well Service Pumps," each of which is hereby incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND

[0003] Well service pumps are used in the oil and gas industry to pump fluids down a well for various purposes. One common use of well service pumps is in hydraulic fracturing of formations. The pump can be used to pump a high pressure fluid containing solids into the well, where the high pressure fluid will expand fractures in the formation or fracture the formation, leaving larger fluid passages through which formation fluids can flow into the well. The solids in the fluid will remain in the larger fluid passages to prop the fluid passages open, thereby increasing well production.

[0004] Well service pumps are commonly plunger pumps, which are a type of reciprocating positive displacement pumps. In these pumps, a plunger reciprocates axially in a fluid end, with a packing retained between the fluid end and plunger preventing leakage during the reciprocating motion of the plunger. A small annular gap is typically provided between the outer diameter of the plunger and the inner diameter of the packing to prevent galling or surface damage to the plunger as the plunger reciprocates. However, slight increases in gap clearance may have a detrimental effect on the life of the packing due primarily to accelerated packing material extrusion.

[0005] High plunger compressive strength is typically needed to help maximize packing life and the operational efficiencies of the pump. Many conventional high pressure well service plunger pumps use plungers of solid construction to achieve high plunger compressive strength. However, larger diameter and/or longer stroke plungers with solid construction are often unwieldy to handle during routine maintenance operations. Hollow plungers have been proposed, but these hollow plungers tend to deflect diametrically under loads.

[0006] Plunger pumps use a crank mechanism to provide the reciprocating motion of the plunger. The crank mechanism typically includes an extension rod that is rigidly attached to a crosshead that is constrained to move axially by the frame of the pump. The crosshead is coupled to an eccentric crankshaft via a wrist pin and connecting rod. As the crankshaft rotates, the connecting rod transfers this motion to the crosshead. Because the crosshead is constrained to move axially, the rotational motion will be converted into reciprocating motion, which is transferred to the plunger via the extension rod.

[0007] The wrist pin is retained to the crosshead and is supported using a bearing located internally within the connecting rod. An annular gap is typically provided between the outer diameter of the wrist pin and the inner diameter of the wrist pin bearing to allow distribution of a lubrication film and to prevent load transfer from the relatively large rod to the much smaller wrist pin. This annular gap allows deformation of the connecting rod bearing surface during high load conditions, which can create uneven loading and premature bearing failure, such as galling.

[0008] Many conventional fluid ends feature a valve over valve arrangement, where the suction and discharge valves are positioned vertically, one valve above the other, and perpendicular to the intersecting plunger bore. This provides a rather compact fluid end design, which is desirable for mobile applications. However, the intersection of these two bores creates a surface discontinuity, significantly increasing stresses within these highly localized areas. These surfaces normally fail due to fatigue as they are also exposed to cyclical loadings.

BRIEF SUMMARY OF THE DISCLOSURE

[0009] An embodiment of a valve seat assembly for a pump comprises a valve seat housing comprising a central passage defined by an inner surface and including an insert receptacle; and a valve seat insert that is insertable into the valve seat receptacle and comprising a contact surface configured to engage a valve of the pump; wherein at least one of the inner surface of the insert receptacle and an outer surface of the valve seat insert is coated with a non-metallic film. In some embodiments, the non-metallic film comprises a material configured to withstand temperatures of at least 600 Fahrenheit without cracking. In some embodiments, the non-metallic film comprises a polymer. In certain embodiments, the inner surface of the insert receptacle comprises a first inclined surface inclined at a first angle from a longitudinal axis of the valve seat housing and a second inclined surface inclined at a second angle from the longitudinal axis that is different from the first angle. In certain embodiments, a first diameter of the inner surface at a first end of the first inclined surface is greater than a second diameter of the inner surface at a second end of the first inclined surface. In some embodiments, a third diameter of the inner surface at an end of the second inclined surface that is spaced from the first inclined surface is greater than the second diameter of the inner surface. In some embodiments, an outer surface of the valve seat insert includes an inclined engagement surface configured to engage the first inclined surface of the insert receptacle; and an outer diameter of the valve seat insert at a first end of the inclined engagement surface is greater than an outer diameter of the valve seat insert at a second end of the inclined engagement surface. In certain embodiments, the valve seat insert comprises an annular shoulder and a cylindrical portion extending axially from the annular shoulder. In certain embodiments, the annular shoulder defines a maximum outer diameter of the valve seat assembly; and the valve seat insert has an axial length that is greater than half of a total axial length of the valve seat assembly.

[0010] An embodiment of a valve seat assembly for a pump comprises a valve seat housing comprising a central passage defined by an inner surface and including an insert receptacle; and an annular valve seat insert that is insertable into the valve seat receptacle and comprising a contact surface configured to engage a valve of the pump; wherein the inner surface of the insert receptacle comprises a first inclined surface inclined at a first angle from a longitudinal axis of the valve seat housing and a second inclined surface inclined at a second angle from the longitudinal axis that is different from the first angle. In some embodiments, a first diameter of the inner surface at a first end of the first inclined surface is greater than a second diameter of the inner surface at a second end of the first inclined surface. In some embodiments, the second inclined surface extends from the second end of the first inclined surface and the contact surface. In certain embodiments, the second angle is greater than the first angle. In certain embodiments, a third diameter of the inner surface at an end of the second inclined surface that is spaced from the first inclined surface is greater than the second diameter of the inner surface. In some embodiments, at least one of the inner surface of the insert receptacle and an outer surface of the valve seat insert is coated with a non-metallic film. In some embodiments, an outer surface of the valve seat insert includes an inclined engagement surface configured to engage the first inclined surface of the insert receptacle; and wherein an outer diameter of the valve seat insert at a first end of the inclined engagement surface is greater than an outer diameter of the valve seat insert at a second end of the inclined engagement surface. In certain embodiments, the valve seat housing comprises an inclined shoulder and the valve seat insert comprises an inclined shoulder configured to matingly engage the inclined shoulder of the valve seat housing. In certain embodiments, the valve seat insert has an axial length that is greater than half of a total axial length of the valve seat assembly.

[0011] An embodiment of a valve seat assembly for a pump comprises a valve seat housing comprising a central passage defined by an inner surface and including an insert receptacle; and an annular valve seat insert that is insertable into the valve seat receptacle and comprising a contact surface configured to engage a valve of the pump; wherein the inner surface of the insert receptacle comprises a first inclined surface, and wherein an outer surface of the valve seat insert includes an inclined engagement surface configured to engage the first inclined surface of the insert receptacle; wherein an outer diameter of the valve seat insert at a first end of the inclined engagement surface is greater than an outer diameter of the valve seat insert at a second end of the inclined engagement surface. In some embodiments, an interference fit is formed between the inclined engagement surface of the valve seat insert and the first inclined surface of the insert receptacle, and wherein a first interference of the interference fit located at the first end of the inclined engagement surface is the same as a second interference of the interference fit at a second end of the inclined engagement surface. In some embodiments, the first inclined surface is inclined at a first angle from a longitudinal axis of the valve seat; and the inner surface of the insert receptacle comprises a second inclined surface inclined at a second angle from the longitudinal axis that is different from the first angle. In certain embodiments, an interference fit is formed between the inclined engagement surface of the valve seat insert and the first inclined surface of the insert receptacle, and wherein an interference of the interference fit decreases between the first end of the inclined engagement surface and the second end of the inclined engagement surface. In certain embodiments, a first diameter of the inner surface at a first end of the first inclined surface is greater than a second diameter of the inner surface at a second end of the first inclined surface. In some embodiments, a third diameter of the inner surface at an end of the second inclined surface that is spaced from the first inclined surface is greater than the second diameter of the inner surface. In some embodiments, at least one of the inner surface of the insert receptacle and an outer surface of the valve seat insert is coated with a non-metallic film. In certain embodiments,

[0012] the valve seat insert has an axial length that is greater than half of a total axial length of the valve seat assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:

[0014] Figure 1 is a side cross-sectional view of an embodiment of a well service pump in accordance with principles disclosed herein;

[0015] Figure 2 is a side cross-sectional view of an embodiment of a valve seat assembly of the well service pump of Figure 1 in accordance with principles disclosed herein;

[0016] Figure 3 is a side cross-sectional view of an embodiment of a valve seat housing of the valve seat assembly of Figure 2 in accordance with principles disclosed herein;

[0017] Figure 4 is a zoomed-in, side cross-sectional view of the valve seat housing of Figure 3;

[0018] Figure 5 is a top view of an embodiment of a valve seat insert of the valve seat assembly of Figure 3 in accordance with principles disclosed herein;

[0019] Figure 6 is a cross-sectional view along line 6-6 of Figure 5 of the valve seat insert of Figure 5;

[0020] Figure 7 is a zoomed-in cross-sectional view along line 6-6 of Figure 5 of the valve seat insert of Figure 5;

[0021] Figure 8 is a side cross-sectional view of another embodiment of a valve seat assembly of the well service pump of Figure 1 in accordance with principles disclosed herein;

[0022] Figure 9 is a side cross-sectional view of an embodiment of a valve seat housing of the valve seat assembly of Figure 8 in accordance with principles disclosed herein; [0023] Figure 10 is a side view of an embodiment of a valve seat insert of the valve seat assembly of Figure 8 in accordance with principles disclosed herein; and

[0024] Figure 1 1 is a cross-sectional view along line 1 1-11 of Figure 10 of the valve seat insert of Figure 10.

DETAILED DESCRIPTION

[0025] The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0026] Certain terms are used throughout the following description and 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. The drawing figures are not necessarily to scale. Certain features and components 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.

[0027] Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

[0028] 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, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other intermediate devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and“axially” generally mean along or parallel to a particular axis (e.g., central axis of a body or a port), while the terms“radial” and “radially” generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Any reference to up or down in the description and the claims is made for purposes of clarity, with“up”,“upper”,“upwardly”,“uphole”, or“upstream” meaning toward the surface of the borehole and with“down”,“lower”, “downwardly”,“downhole”, or“downstream” meaning toward the terminal end of the borehole, regardless of the borehole orientation. As used herein, the terms “approximately,”“about,”“substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

[0029] Referring to Figure 1 , pump 10 is shown. In the embodiment of Figure 1 , pump 10 is well service pump having internal plungers 28, and thus is referred to as a plunger pump 10; however, in other embodiments, pump 10 may comprise other types of pumps known in the art. In this embodiment, well service pump 10 includes a fluid end 12 coupled to a power end 14 via a plurality of stray rods or fasteners 13.

[0030] The fluid end 12 of well service pump 10 includes a fluid end housing 15 which comprises a fluid chamber 16, a suction bore 18A, a discharge bore 18B, a plunger bore 20A, and an access bore 20B, each of which intersect fluid chamber 16. In this embodiment, suction bore 18A and discharge bore 18B of fluid end housing 15 are opposed and axially aligned along a common longitudinal axis. Suction bore 18A of fluid end housing 15 is in selective fluid communication with a suction manifold 21 via a suction valve 23A of fluid end 12. Similarly, the discharge bore 18B of fluid end housing 15 is in selective fluid communication with a discharge port 25 via a discharge valve 23B of fluid end 12. Fluid end 12 of well service pump 10 additionally includes a suction valve seat assembly 100A positioned in suction bore 18A of fluid end housing 15 and a discharge valve seat assembly 100B positioned in the discharge bore 18B of fluid end housing 15. In some embodiments, discharge valve seat assembly 100B may be coupled to fluid end housing 15 via frictional contact, an interference fit, a connector positioned on discharge valve seat assembly 100B, and/or via a separate retainer used to fasten discharge valve seat assembly 100B with fluid end housing 15. In some embodiments, suction valve seat assembly 100A may be coupled to fluid end housing 15 via frictional contact, an interference fit, a connector positioned on suction valve seat assembly 100A, and/or via a separate retainer used to fasten suction valve seat assembly 100A with fluid end housing 15. [0031] Suction valve 23A of fluid end 12 is biased into engagement or contact with suction valve seat assembly 100A via a suction biasing member 27A while discharge valve 23B is biased into engagement or contact with discharge seat assembly 100B via a discharge biasing member 27B. When suction valve 23A is in contact with suction valve seat assembly 100A, fluid communication is restricted between suction manifold 21 and the fluid chamber 16 of fluid end housing 15. Similarly, fluid communication is restricted between discharge port 25 and fluid chamber 16 when discharge valve 23B is contacts discharge valve assembly 100B.

[0032] In this embodiment, well service pump 10 additionally includes a plunger 28 slidably positioned in plunger bore 20A. Plunger 28 may reciprocate into and out of the fluid chamber 16 in response to the actuation of a crank mechanism 34 of the power end 14 of well service pump 10. During a suction stroke of plunger 28, plunger 28 is withdrawn from the fluid chamber 16 into the plunger bore 20A, thereby drawing fluid from the suction manifold 21 , through suction valve 23A, and into fluid chamber 16 of fluid end housing 15. During the suction stroke of plunger 28, the suction valve 23A is lifted off the suction valve seat assembly 100A when the force of the fluid from the fluid chamber 16 overcomes the force of suction biasing member27A. Fluid flows into fluid chamber 16 from suction manifold 21 in response to the suction valve 23A being lifted from the suction valve seat assembly 100A.

[0033] During a discharge stroke of plunger 28, plunger 28 displaces or extends from the plunger bore 20A into fluid chamber 16, whereby plunger 28 forces fluid in fluid chamber 16 through discharge valve 23B and into the discharge port 25 of fluid end housing 15. During the discharge stroke of plunger 28, the discharge valve 23B is lifted off the discharge valve seat assembly 100B when the force of the fluid from the fluid chamber 16 overcomes the force of discharge biasing member 27B. Fluid flows into discharge port 25 from fluid chamber 16 in response to the discharge valve 23B being lifted from the discharge valve seat assembly 100B.

[0034] Referring to Figures 2-7, an embodiment of a valve seat assembly 100 of the well service pump 10 of Figure 1 is shown in Figures 2-7. The valve seat assembly 100 shown in Figures 2-7 may comprise suction valve seat assembly 100A and/or discharge valve seat assembly 100B of the well service pump 10 of Figure 1. In the embodiment of Figures 2-7, valve seat assembly 100 has a central or longitudinal axis 105 and generally includes a cylindrical valve seat housing 102 and an annular valve seat insert 200 received in the valve seat housing 102. [0035] The valve seat housing 102 of valve seat assembly 100 has a first or upper end 104, a second or lower end 106 opposite upper end 104, a central bore or passage 108 defined by a generally cylindrical inner surface 110 extending between ends 104, 106, and a generally cylindrical outer surface 112 extending between ends 104, 106. In this embodiment, an annular seal assembly 1 14 is positioned on the outer surface 1 12 of valve seat housing 1 12. Seal assembly 1 14 is configured to seal against an inner surface of the suction bore 18A (when valve seat housing 102 positioned in suction bore 18A) and/or discharge bore 18B (when valve seat housing 102 is positioned in discharge bore 18B) of fluid end housing 15 of the fluid end 12 shown in Figure 1. Additionally, outer surface 1 12 of valve seat housing 102 includes a radially extending, annular shoulder 116 positioned axially between seal assembly 1 14 and upper end 104. Annular shoulder 1 16 is configured to matingly seat against a corresponding shoulder of the suction bore 18A (when valve seat housing 102 positioned in suction bore 18A) and/or discharge bore 18B (when valve seat housing 102 is positioned in discharge bore 18B) of fluid end housing 15 of the fluid end 12 shown in Figure 1.

[0036] In this embodiment, the central passage 108 of valve seat housing 102 includes an insert receptacle 1 18 positioned between upper end 104 and lower end 106. Insert receptacle 1 18 of valve seat housing 102 is configured to receive and house the valve seat insert 200 of valve seat assembly 100. As shown particularly in Figures 3, 4, the inner surface 1 10 of insert receptacle 118 includes a radially extending annular shoulder 120, an annular first or lower inclined surface 126, and an annular second or upper inclined surface 130. In this embodiment, an annular curved edge 124 is positioned between a first or lower end 127 of lower inclined surface 126 and a radially inner end of annular shoulder 120. In this embodiment, curved edge 124 has a radius of about 1/8 of an inch; however, in other embodiments, the radius of curved edge 124 may vary.

[0037] The lower inclined surface 126 of insert receptacle 118 extends from lower end 127 to an annular transition point positioned between lower inclined surface 126 and upper inclined surface 130 of insert receptacle 1 18. Upper inclined surface 130 extends from a first or lower end positioned at transition point 128 to a second or upper end 132 that defines an upper end of insert receptacle 118. In this embodiment, an axial length 131 between annular shoulder 120 and transition point 128 is between about 0.40 inches and 0.41 inches; however, in other embodiments, length 131 may vary. In this embodiment, an axial length 133 between annular shoulder 120 and the upper end 132 of upper inclined surface 130 is between about 0.51 inches and 0.52 inches; however, in other embodiments, length 133 may vary. The inner surface 1 10 of valve seat housing 102 includes an annular inclined shoulder 140 extending from the upper end 132 of upper inclined surface 130 towards the upper end 104 of valve seat housing 102. In this embodiment, an annular curved edge 142 is positioned at upper end 104 of valve seat housing 102, where inclined shoulder 140 extends to curved edge 142.

[0038] As shown particularly in Figure 4, in this embodiment, lower inclined surface 126 of insert receptacle 118 is inclined at a non-zero first angle 125 relative to the central axis 105 such that a first inner diameter 137 of central passage 108 located at the lower end 127 of lower inclined surface 126 is less than a second inner diameter 139 of central passage 108 located at the transition point 128. In this embodiment, first angle 125 of lower inclined surface 126 is between about 0.7° and 1.3°; however, in other embodiments, first angle 125 of lower inclined surface 126 may vary. Additionally, in this embodiment, the first inner diameter 137 of central passage 108 is between about 4.24 inches and 4.25 inches, the second inner diameter 139 of central passage 108 is between about 4.23 inches and 4.24 inches, and the difference between first inner diameter 137 and second inner diameter 139 is between about 0.08 inches and 0.12 inches; however, in other embodiments, the size of diameters 137, 139, and the difference between them, may vary.

[0039] In this embodiment, upper inclined surface 130 of insert receptacle 1 18 is inclined at a non-zero second angle 135 relative to the central axis 105 such that a third inner diameter 141 of central passage 108 located at the upper end 132 of upper inclined surface 130 is greater than the second inner diameter 139 of central passage 108 located at the transition point 128. In this embodiment, second angle 135 of upper inclined surface 130 is between about 2.7° and 3.3°; however, in other embodiments, second angle 135 of upper inclined surface 130 may vary. Additionally, in this embodiment, the third inner diameter 141 of central passage 108 is between about 4.24 inches and 4.25 inches, and the difference between third inner diameter 141 and second inner diameter 139 is between about 0.08 inches and 0.12 inches; however, in other embodiments, the size of third inner diameter 141 , and the difference between third inner diameter 141 and second inner diameter 139 them may vary. In some embodiments, the first diameter 127 of central passage 108 and the third inner diameter 141 of central passage 108 may be substantially equal. [0040] As described above, due to first angle 125 of lower inclined surface 126, central passage 108 of valve seat housing 102 decreases in diameter moving in the direction of upper end 104 from the lower end 127 of lower inclined surface 126 to transition point 128. Additionally, second angle 135 of upper inclined surface 130, central passage 108 of valve seat housing 102 increases in diameter moving in the direction of upper end 104 from transition point 128 to the upper end 132 of upper inclined surface 130. Thus, first angle 125 may be described as a negative angle 125 and lower inclined surface 126 may be described as a negatively inclined surface 126, whereas second angle 135 may be described as a positive angle 135 and upper inclined surface 130 may be described as a positively inclined surface 130. As will be described further herein, negatively inclined surface 126 is configured to lock valve seat insert 200 within insert receptacle 118 of valve seat housing 102, assisting to prevent the dislodging of valve seat insert 200 from insert receptacle 1 18 following forcible contact between one of valves 23A, 23B of the fluid end 12 shown in Figure 1 and valve seat insert 200.

[0041] As described above, suction valve 23A of fluid end 12 forcibly contacts suction valve seat assembly 100A and discharge valve 23B of fluid end 12 contacts forcibly contacts discharge valve 100B. In this embodiment, during operation of well service pump 10, valves 23A, 23B are configured to contact the valve seat insert 200, and not the valve seat housing 102, of valve seat assemblies 100A, 100B, respectively. Additionally, the valve seat housing 102 of valve seat assembly 100 comprises a first material having material properties that differ from material properties of a second material of which the valve seat insert 200 of valve seat assembly 100 is comprised.

[0042] Particularly, the second material of valve seat insert 200 comprises a harder, more wear resistant material than the first material of valve seat housing 102. In this embodiment, the second material of valve seat insert 200 comprises tungsten carbide; however, in other embodiments, the second material of valve seat insert 200 may comprise other types of wear resistant materials. The wear resistant material of valve seat insert 200 is configured to better withstand repeated contact from either suction valve 23A or discharge valve 23B of fluid end 12, and thereby increase the service life of valve seat assembly 100 while also minimizing the material cost of valve seat assembly 100 by forming only the portion of valve seat assembly 100 exposed to contact from valve 23A, 23B (valve seat insert 200) from the wear resistant second material. Thus, the first material of valve seat housing 102 may comprise a material that is less expensive and easier to machine or manufacture than the wear resistant material from which valve seat insert 200 is comprised.

[0043] As shown particularly in Figures 5-7, the valve seat insert 200 of valve seat assembly 100 has a first or upper end 202, a second or lower end 204 opposite upper end 202, a central bore or passage 206 defined by a generally cylindrical inner surface 208 extending between ends 202, 204, and a generally cylindrical outer surface 210 extending between ends 202, 204. In this embodiment, valve seat insert 200 has an axial length 207 between upper end 202 and lower end 204 that is about 0.49 inches to 0.51 inches; however, in other embodiments, axial length 207 of valve seat insert 200 may vary.

[0044] In this embodiment, the inner surface 208 of valve seat insert 200 includes an annular inclined shoulder 212 extending axially from upper end 202. Inclined shoulder 212 comprises an engagement surface configured to contact one of the valves 23A, 23B of fluid end 12 during the operation of well service pump 10. Inclined shoulder 212 is inclined by a third angle 213 relative to the central axis 105 of valve seat assembly 100. In this embodiment, third angle 213 is between about 25° and 35°; however, in other embodiments, third angle 213 may vary. Additionally, in this embodiment, an inner diameter 215 of inner surface 208 at the lower end of inclined shoulder 212 is between about 3.25 inches and 3.26 inches; however, in other embodiments, the inner diameter 215 of inner surface 208 at the lower end of inclined shoulder 212 may vary.

[0045] In this embodiment, the outer surface 210 of valve seat insert 200 comprises an annular inclined shoulder 220 extending from lower end 204 to an annular transition point 224, and an annular inclined engagement surface 228 extending from transition point 224 to the upper end 202 of valve seat insert 200. Additionally, in this embodiment, the upper end 202 of valve seat insert is defined by an annular upper shoulder 240 that extends radially between an upper end of inclined shoulder 212 and an upper end of inclined engagement surface 228. In other embodiments, inclined shoulder 212 may extend entirely to upper end 202 of valve seat insert 200 and thus intersect inclined engagement surface 228.

[0046] As shown particularly in Figure 7, in this embodiment, engagement surface 228 of valve seat insert 200 is inclined at a non-zero fourth angle 229 relative to the central axis 105 of valve seat assembly 100 such that a first outer diameter 231 of outer surface 210 located at transition point 224 is greater than a second outer diameter 233 of outer surface 210 located at upper end 202. In this embodiment, fourth angle 229 of engagement surface 228 is between about 0.7° and 1.3°; however, in other embodiments, fourth angle 229 of engagement surface 228 may vary. Additionally, in this embodiment, the first outer diameter 231 of outer surface 210 is between about 4.25 inches and 4.26 inches, the second outer diameter 233 of outer surface 210 is between about 4.24 inches and 4.25 inches, and the difference between first outer diameter 231 and second outer diameter 233 is between about 0.08 inches and 0.12 inches; however, in other embodiments, the size of diameters 231 , 233, and the difference between them, may vary.

[0047] Due to fourth angle 229 of engagement surface 228, the outer diameter of engagement surface 228 increases moving from lower end 204 towards upper end 202, with the first outer diameter 231 of engagement surface 228 at lower end 204 being less than the second outer diameter 233 of engagement surface 228 at upper end 202. Thus, fourth angle 229 may be described as a positive angle 229 and engagement surface 228 may be described as a positively inclined engagement surface 228. In this embodiment, fourth angle 229 is substantially similar to the first angle 125 of the lower inclined surface 126 of valve seat housing 102 in size or degree of deviation from central axis 105; however, in other embodiments, fourth angle 229 may differ from first angle 125. Additionally, as described above, first angle 125 is a negative angle whereas fourth angle 229 is a positive angle. In this configuration, an annular, first or lower inclined interface 250 is formed between engagement surface 228 of valve seat insert 200 and the lower inclined surface 126 of valve seat housing 102 when valve seat insert 200 is positioned in the insert receptacle 118 of valve seat housing 102. Engagement surface 228 and lower inclined surface 126 extend parallel along lower inclined interface 250.

[0048] In this embodiment, fourth angle 229 is less than the second angle 135 of the upper inclined surface 130 of valve seat housing 102 in size or degree of deviation from central axis 105. An annular, second or upper inclined interface 252 is formed between engagement surface 228 of valve seat insert 200 and the upper inclined surface 130 of valve seat housing 102 when valve seat insert 200 is positioned in the insert receptacle 1 18 of valve seat housing 102. Thus, in this embodiment, engagement surface 228 does not extend in parallel with upper engagement surface 230 along upper inclined interface 250. Instead, engagement surface 228 extends at an angle relative to upper engagement surface 230 along upper inclined interface 250. [0049] Still referring to Figures 2-7, having described the structural features of the embodiment of valve seat assembly 100 shown in Figures 2-7, an embodiment of assembling valve seat assembly 100 will now be described. In an embodiment, prior to insertion of valve seat insert 200 into the insert receptacle 118 of valve seat housing 102, the surfaces of insert receptacle 1 18 (annular shoulder 120, lower inclined surface 126, and upper inclined surface 130) are coated with a temperature-resistant non- metallic film or paste 260 (shown in Figure 2). Non-metallic film 260 is configured to dampen and/or absorb vibrational shock imparted to valve seat insert 200 from the valves 23A, 23B of fluid end 12 during the operation of well service pump 10, and thereby prevent valve seat insert 200 from being ejected from insert receptacle 1 18 of valve seat housing 102 in response to impact between valve seat insert 200 and valves 23A, 23B.

[0050] Thus, non-metallic film 260 prevents or at least mitigates “bouncing” or “chattering” of the lower end 204 of valve seat insert 200 against the annular shoulder 120 of insert receptacle 1 18 during the operation of well service pump 10 which may otherwise inadvertently eject or dislodge valve seat insert 200 from insert receptacle 1 18. Although in this embodiment the surfaces of insert receptacle 118 are coated with non-metallic film 260 prior to the insertion of valve seat insert 200 therein, in other embodiments, the inclined engagement surface 228 of valve seat insert 200 is coated with non-metallic film 260 prior to insertion into the insert receptacle 118 of valve seat housing 102. In some embodiments, non-metallic film 260 may have adhesive properties to assist with adhering valve seat insert 200 to insert receptacle 1 18 and thereby prevent the dislodging of valve seat insert 200 from insert receptacle 118.

[0051] In this embodiment, non-metallic film 260 comprises a temperature-resistant (e.g., capable of withstanding temperatures f about 500 Fahrenheit (F) to about 1 ,000 F without cracking, shrinkage, mass loss, and/or degradation of properties polymer based material, such as Seal-Lock® Fluid-Weld® provided by Silver Seal Products, Inc. of 19224 Allen Road, P.O. Box 1050 Trenton, Michigan; however, in other embodiments, non-metallic film 260 may comprise other temperature-resistant materials. In still further embodiments, instead of non-metallic film 260, a solid temperature-resistant, vibrational shock dampening material (e.g., soft metals, polymer gaskets, etc.) may be positioned on the surfaces of insert receptacle 118 to dampen and/or absorb vibrational energy imparted to valve seat insert 200 in response to contact between insert 200 and the valves 23A, 23B of fluid end 12. [0052] Once non-metallic film 260 has been applied to the surfaces of insert receptacle 1 18, valve seat housing 102 is heated to a predetermined heating temperature to expand the inner diameter of insert receptacle 1 18, permitting the insertion of valve seat insert 200 therein. In this embodiment, the predetermined heating temperature is between about 800 F and 1 ,000 F; however, in other embodiments, the predetermined heating temperature may vary. Once valve seat housing 102 is heated to the predetermined heating temperature, valve seat insert 200 is axially inserted through central passage 108 of valve seat housing 102 and into the insert receptacle 1 18 such that the lower end 204 of valve seat insert 200 contacts the non-metallic film 260 positioned on the annular shoulder 120 of valve seat housing 102.

[0053] Following the insertion of valve seat inset 200 into the insert receptacle 118 of valve seat housing 102, valve seat housing 102 may be permitted to cool from the predetermined heating temperature to an ambient temperature. As valve seat housing 102 cools, an interference fit is formed between inclined surfaces 126, 130 of insert receptacle 1 18 and the inclined engagement surface 228 of valve seat insert 200. Particularly a first or lower interference fit 251 is formed along the lower inclined interface 250 formed between engagement surface 228 of valve seat insert 200 and the lower inclined surface 126 of valve seat housing 102. Lower interference fit 251 is substantially constant moving axially along lower inclined interface 250 between transition point 224 of valve seat insert 200 to the transition point 128 of insert receptacle 118. In other words, the lower interference fit 251 formed between valve seat insert 200 and insert receptacle 118 of valve seat housing 102 at the axial location of the transition point 224 of valve seat insert 200 is substantially the same as the lower interference fit 251 formed between valve seat insert 200 and insert receptacle 1 18 at the axial location of the transition point 128 of insert receptacle 118. In this embodiment, lower interference fit 251 is between about 0.005 inches and 0.010 inches; however, in other embodiments, the size of lower interference fit 251 may vary.

[0054] Given that the inclined engagement surface 228 of valve seat insert 200 extends parallel with the lower inclined surface 126 of insert receptacle 118 and the first outer diameter 231 of valve seat insert 200 at transition point 224 is greater than the second outer diameter 233 of valve seat insert 200 at upper end 202, the amount of interference (e.g., difference in diameter) between first outer diameter 231 of valve seat insert 200 and the third inner diameter 131 of the central passage 108 of valve seat housing 102 is greater than the size of lower interference fit 251. The additional interference formed between the transition point 224 of valve seat insert 200 and the transition point 128 of insert receptacle 1 18 assists in preventing valve seat insert 200 from becoming dislodged or ejected from insert receptacle 1 18 in response to impact between valve seat insert 200 and valves 23A, 23B. In this embodiment, the interference formed between the transition point 224 of valve seat insert 200 and the transition point 128 of insert receptacle 118 is about twice as great as the interference provided by lower interference fit 251 ; however, in other embodiments, the additional interference formed between transition points 224, 128 may vary.

[0055] Additionally, as valve seat housing 102 cools, a second or upper interference fit 253 is formed along the upper inclined interface 252 formed between engagement surface 228 of valve seat insert 200 and the upper inclined surface 130 of valve seat housing 102. Upper interference fit 253 varies moving axially along upper inclined interface 252 such that a maximum interference of upper interference fit 253 is formed between valve seat insert 200 and insert receptacle 1 18 at the axial location of transition point 128. The interference of upper interference fit 253 gradually reduces from the maximum at transition point 128 moving axially upwards along upper inclined interface 252 to a minimum interference of upper interference fit 253 at the axial location of the upper end 202 of valve seat insert 200.

[0056] In this embodiment, the minimum interference of upper interference fit 253 at the axial location of upper end 202 is substantially zero; however, in other embodiments, the minimum interference of upper interference fit 253 may be greater than zero but still less than the maximum interference of upper interference fit 253. Given that the radial width of valve seat insert 200 (e.g., the radial width between inner surface 208 and outer surface 210) decreases moving axially upwards towards upper end 202 from transition point 224, the reduction in interference provided by upper interference fit 253 reduces the stress applied to the relatively thin upper end 202 of valve seat insert 200, serving to prevent or mitigate the possibility of cracking or other stress-related damage occurring to upper end 202 from excessive interference between valve seat insert 200 at upper end 202 and insert receptacle 1 18.

[0057] Referring to Figures 8-11 , an embodiment of a valve seat assembly 300 of the well service pump 10 of Figure 1 is shown in Figures 8-11. The valve seat assembly 300 shown in Figures 8-11 may comprise suction valve seat assembly 100A and/or discharge valve seat assembly 100B of the well service pump 10 of Figure 1. Valve seat assembly 300 includes features in common with the valve seat assembly 100 shown in Figures 2-7, and shared features are labeled similarly. In the embodiment of Figures 8-1 1 , valve seat assembly 300 has a central or longitudinal axis 305 and generally includes a cylindrical valve seat housing 302 and an annular valve seat insert 400 received in the valve seat housing 302.

[0058] The valve seat housing 302 of valve seat assembly 300 has a first or upper end

304, a second or lower end 306 opposite upper end 304, a central bore or passage 308 defined by a generally cylindrical inner surface 310 extending between ends 304, 306, and a generally cylindrical outer surface 312 extending between ends 304, 306. Outer surface 312 of valve seat housing 302 includes a radially extending, annular shoulder 314 positioned axially between seal assembly 1 14 and upper end 304. Annular shoulder 314 is configured to matingly seat against a corresponding shoulder of the suction bore 18A (when valve seat housing 302 positioned in suction bore 18A) and/or discharge bore 18B (when valve seat housing 302 is positioned in discharge bore 18B) of fluid end housing 15 of the fluid end 12 shown in Figure 1.

[0059] In this embodiment, the central passage 308 of valve seat housing 302 includes an insert receptacle 316 positioned between upper end 304 and lower end 306. Insert receptacle 316 of valve seat housing 302 is configured to receive and house the valve seat insert 400 of valve seat assembly 300. As shown particularly in Figure 9, the inner surface 310 of insert receptacle 316 includes a radially extending annular upper shoulder 318 and an annular inclined surface 320. Inclined surface 320 extends along central axis 305 between a first or lower end 319 and a second or upper end 321 opposite lower end 319.

[0060] In this embodiment, an annular first or upper curved edge 324 of inner surface 310 is positioned between the upper end 321 of inclined surface 320 and a lower end 323 of annular shoulder 318. In this embodiment, upper curved edge 324 has a radius of approximately 0.31 inches; however, in other embodiments, the radius of upper curved edge 324 may vary. Inner surface 310 of valve seat housing 302 additionally includes a lower annular shoulder 326 extending radially inwards towards central axis

305. Lower annular shoulder 326 is positioned axially between the lower end 319 of inclined surface 320 and the lower end 304 of valve seat housing 302. An annular second or lower curved edge 328 extends between the lower end 319 of inclined surface 320 and lower shoulder 326. In this embodiment, lower curved edge 328 has a radius of approximately 1/8 of an inch; however, in other embodiments, the radius of lower curved edge 328 may vary. In this embodiment, an annular curved edge 330 is positioned at upper end 304 of valve seat housing 302, where upper shoulder 318 extends to curved edge 330.

[0061] In this embodiment, inclined surface 320 of insert receptacle 316 is inclined at a non-zero first angle 325 relative to the central axis 305 such that a first inner diameter 332 of central passage 308 located at the lower end 319 of inclined surface 320 is greater than a second inner diameter 334 of central passage 308 located at the upper end 321 of inclined surface 320. Thus, the diameter of central passage 308 gradually decreases moving axially from the lower end 319 of inclined surface 320 towards the upper end 321 thereof. Thus, first angle 325 may be described as a negative first angle 325 and inclined surface 320 may be described as a negatively inclined surface 320. Similar to the functionality provided by negatively inclined surface 126 of the valve seat housing 102 shown in Figures 2-7, negatively inclined surface 320 assists in preventing the dislodging of valve seat insert 400 from insert receptacle 316 following forcible contact between one of valves 23A, 23B of the fluid end 12 shown in Figure 1 and valve seat insert 400.

[0062] In this embodiment, first angle 325 of inclined surface 320 is between about 0.7° and 1.3°; however, in other embodiments, first angle 325 of inclined surface 320 may vary. Additionally, in this embodiment, the first inner diameter 332 of central passage 308 is between about 3.75 inches and 3.76 inches, the second inner diameter 334 of central passage 308 is between about 3.74 inches and 3.75 inches, and the difference between first inner diameter 332 and second inner diameter 334 is between about 0.06 inches and 0.10 inches; however, in other embodiments, the size of diameters 332, 334, and the difference between them, may vary.

[0063] The central passage 308 of valve seat housing 302 includes a reduced diameter portion 309 extending between lower shoulder 326 and the lower end 306 of valve seat housing 302. In this embodiment, the reduced diameter portion 309 of central passage

308 has an axial length of approximately 12-15% of the total axial length (axial length extending between ends 304, 306) of valve seat housing 302; however, in other embodiments, the relationship between the axial length of reduced diameter portion

309 and the total axial length of valve seat housing 302 may vary. Additionally, in this embodiment, insert receptacle 316 has an axial length of approximately 75-90% of the total axial length of valve seat housing 302; however, in other embodiments, the relationship between the axial length of insert receptacle 316 and the total axial length of valve seat housing 302 may vary. Further, in this embodiment, inclined surface 320 of insert receptacle 316 has an axial length that is 50% or greater than the total axial length of valve seat housing 302; however, in other embodiments, the relationship between the axial length of inclined surface 320 and the total axial length of valve seat housing 302 may vary.

[0064] As shown particularly in Figures 10, 1 1 , the valve seat insert 400 of valve seat assembly 300 has a first or upper end 402, a second or lower end 404 opposite upper end 402, a central bore or passage 406 defined by a generally cylindrical inner surface 408 extending between ends 402, 404, and a generally cylindrical outer surface 410 extending between ends 402, 404. In this embodiment, the valve seat housing 302 of valve seat assembly 300 comprises a first material having material properties that differ from material properties of a second material of which the valve seat insert 400 of valve seat assembly 300 is comprised.

[0065] Particularly, the second material of valve seat insert 400 comprises a harder, more wear resistant material than the first material of valve seat housing 302. In this embodiment, the second material of valve seat insert 400 comprises tungsten carbide; however, in other embodiments, the second material of valve seat insert 400 may comprise other types of wear resistant materials. Similar to the functionality provided by the valve seat insert 200 of valve seat assembly 100, the wear resistant material of valve seat insert 400 of valve seat assembly 300 is configured to better withstand repeated contact from either suction valve 23A or discharge valve 23B of fluid end 12, and thereby increase the service life of valve seat assembly 400 while also minimizing the material cost of valve seat assembly 300.

[0066] In this embodiment, the inner surface 408 of valve seat insert 400 includes an annular inclined shoulder 412 extending axially towards an annular first or upper curved edge 414 positioned at the upper end 402 of valve seat insert 400. Inclined shoulder 412 comprises an engagement surface configured to contact one of the valves 23A, 23B of fluid end 12 during the operation of well service pump 10. The inner surface 408 of valve seat insert 400 additionally includes a substantially constant diameter or cylindrical portion 416 extending axially from lower end 404 and an annular second or lower curved edge 418 extending axially between an upper end of cylindrical portion 416 and a lower end of inclined shoulder 412. In this embodiment, an inner diameter 419 of the cylindrical portion 416 of inner surface 408 is less than an inner diameter of the reduced diameter portion 309 of valve seat housing 302. Thus, in this embodiment, inner diameter 419 defines a minimum internal or inner diameter 419 of valve seat assembly 300; however, in other embodiments, the relationship between the inner diameter 419 of valve seat insert 400 and the inner diameter of the reduced diameter portion 309 of valve seat housing 302 may vary.

[0067] In this embodiment, the outer surface 410 of valve seat insert 400 comprises an annular inclined engagement surface 420 extending from an annular first or lower curved edge 422 positioned at the lower end 404 of valve seat insert 400, and an annular inclined shoulder 424 extending axially to a substantially constant diameter or cylindrical portion 426 which extends to upper curved edge 414. Additionally, outer surface 410 includes an annular intermediate curved edge 428 extending axially between inclined engagement surface 420 and inclined shoulder 424.

[0068] In this embodiment, inclined engagement surface 420 has an axial length that is greater than 50% of the total axial length extending from upper end 402 to lower end 404 of valve seat inset 400; however, in other embodiments, the relationship between the axial length of inclined engagement surface 420 and the total axial length of valve seat insert 400 may vary. The cylindrical portion 426 of outer surface 410 has an outer diameter that defines a maximum outer diameter of valve seat insert 400. In this embodiment, the outer diameter of the cylindrical portion 426 of outer surface 410 is substantially equal to a maximum outer diameter of valve seat housing 302; however, in other embodiments, the relationship between the outer diameter of the cylindrical portion 426 of valve seat insert 400 and the maximum outer diameter of valve seat housing 302 may vary.

[0069] The inclined engagement surface 420 of outer surface 410 is inclined at a non zero second angle 425 relative to the central axis 305 such that a first outer diameter 430 of outer surface 410 located at a first or lower end 421 of inclined engagement surface 420 is greater than a second outer diameter 432 of outer surface 410 located at a second or upper end 432 of inclined engagement surface 420. Thus, the diameter of outer surface 410 gradually decreases moving axially from the lower end 421 of inclined engagement surface 420 towards the upper end 423 thereof. Thus, second dangle 425 may be described as a negative second angle 425 and inclined engagement surface 420 may be described as a negatively inclined engagement surface 420.

[0070] In this embodiment, second angle 425 of inclined engagement surface 420 is between about 0.7° and 1.3°; however, in other embodiments, second angle 425 of inclined engagement surface 420 may vary. Additionally, in this embodiment, the first inner diameter 430 of outer surface 410 is between about 3.76 inches and 3.77 inches, the second inner diameter 432 of outer surface 410 is between about 3.75 inches and 3.76 inches, and the difference between first inner diameter 430 and second inner diameter 432 is between about 0.06 inches and 0.10 inches; however, in other embodiments, the size of diameters 430, 432, and the difference between them, may vary.

[0071] The inclined shoulder 423 of valve seat insert 400 is configured to matingly engage the upper shoulder 318 when valve seat insert 400 is received in the insert receptacle 316 of valve seat housing 302. Additionally, the inclined engagement surface 420 of valve seat insert 400 is configured to matingly engage the inclined surface 320 of valve seat housing 302 when valve seat insert 400 is received in the insert receptacle 316 of valve seat housing 302. In this embodiment, second angle 425 of the inclined engagement surface 420 is substantially similar to the first angle 325 of the inclined surface 320 of valve seat housing 302 in size or degree of deviation from central axis 305; however, in other embodiments, second angle 425 may differ from first angle 325.

[0072] In this configuration, an annular inclined interface 427 (shown in Figure 8) is formed between inclined engagement surface 420 of valve seat insert 400 and the inclined surface 320 of valve seat housing 302 when valve seat insert 400 is positioned in the insert receptacle 316 of valve seat housing 302. Inclined engagement surface 420 and inclined surface 320 extend parallel along inclined interface 427. In this embodiment, non-metallic film 260 is positioned along at least a portion of inclined interface 427 to dampen and/or absorb vibrational shock imparted to valve seat insert 400 from the valves 23A, 23B of fluid end 12 during the operation of well service pump 10; however, in other embodiments, valve seat assembly 300 may not include non- metallic film 260.

[0073] In an embodiment, valve seat assembly 300 is assembled by heating valve seat housing 302 to a predetermined heating temperature to expand the inner diameter of insert receptacle 316, permitting the insertion of valve seat insert 400 therein. Once valve seat housing 302 is heated to the predetermined heating temperature, valve seat insert 400 is axially inserted through central passage 308 of valve seat housing 302 and into the insert receptacle 316 such that inclined shoulder 423 of valve seat insert 400 matingly engages the upper shoulder 318 of valve seat housing 302 with valve seat insert 400 received in insert receptacle 316. [0074] Following the insertion of valve seat inset 400 into the insert receptacle 316 of valve seat housing 302, valve seat housing 302 is permitted to cool from the predetermined heating temperature to an ambient temperature. As valve seat housing 302 cools, an interference fit 429 is formed between inclined surface 320 of valve seat housing 302 and the inclined engagement surface 420 of valve seat insert 400. Interference fit 429 is substantially constant moving axially along inclined interface 427. In this embodiment, interference fit 429 is between about 0.005 inches and 0.010 inches; however, in other embodiments, the size of interference fit 429 may vary. Given that the inclined engagement surface 420 of valve seat insert 400 extends parallel with the inclined surface 320 of insert receptacle 316 and the first outer diameter 430 of inclined engagement surface 420 is greater than the second outer diameter 432 thereof, the difference in diameter or interference formed between the first outer diameter 430 and the second inner diameter 334 of central passage 308 is greater than the difference in diameter or interference formed between first outer diameter 430 and the first inner diameter 332 of central passage 308. In other words, inclined interface 427 wedges valve seat insert 400 into the insert receptacle 316 of valve seat housing 302, assisting in preventing valve seat insert 400 from becoming dislodged from insert receptacle 316.

[0075] In this embodiment, when valve seat insert 400 is received in the insert receptacle 316 of valve seat housing 302, valve seat insert 400 covers a majority of an axial length of inner surface 310 of valve seat housing 302 such that only a minority of the axial length of inner surface 310 is exposed to tools or objects passing through the central passage 308 of valve seat housing 302. Given that valve seat insert 400 is formed of a harder material than valve seat housing 302, the inner surface 310 of valve seat housing 302 is protected from damage (e.g., resulting from contact between inner surface 310 and tools passing through central passage 308) by the extension of valve seat insert 400 through a majority of the axial length of inner surface 310. Additionally, given that in this embodiment valve seat insert 400 defines a maximum outer diameter of valve seat assembly 300, the inclined shoulder 424 of valve seat insert 400 covers an entirety of the upper shoulder 318 of valve seat housing 302, thereby protecting upper shoulder 318 from damage (e.g., resulting from contact between upper shoulder 318 and tools passing through central passage 308).

[0076] While exemplary embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1 ), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.