DURABLE VALVES FOR DISPLACEMENT PUMPS

A valve for a displacement pump includes a valve body having an annular strikeface and defining an annular receptacle, and an annular seal received in the receptacle of the valve body, the seal including an annular contact surface, wherein the seal defines a cumulative displacement ratio of (i) at least one of at most 0.20 at a location that is spaced 40% from an inner diameter (ID) of the contact surface of the seal moving towards an outer diameter (OD) of the contact surface, (ii) at most 0.35 at a location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and (iii) at most 0.45 at a location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

Not applicable.

BACKGROUND

Displacement pumps are utilized in a variety of applications for transporting fluid by enclosing a fixed volume of fluid and mechanically transporting the enclosed volume through the displacement pump. Well service pumps, but one type of displacement pump, are used in the oil and gas industry to pump fluids down a well for various purposes. For example, one common use of well service pumps is in hydraulic fracturing of subterranean earthen formations. Particularly, well service pumps may pump a high-pressure fluid containing solids into a wellbore extending through an earthen formation whereby the pumped high-pressure fluid may expand fractures formed in the earthen formation.

Well service pumps are commonly plunger pumps, which are a type of reciprocating positive displacement pump. In these pumps, a plunger reciprocates axially in a fluid end of the pump, with a packing retained between the fluid end and the plunger preventing leakage during the reciprocating motion of the plunger. Plunger pumps often 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. Additionally, the fluid end of well service pumps, including plunger pumps, include a valve-over-valve arrangement in which suction and discharge valves of the pump are positioned vertically, one valve above the other, and perpendicular to an intersecting plunger bore.

BRIEF SUMMARY OF THE DISCLOSURE

An embodiment of a valve for a displacement pump comprises a valve body having an annular strikeface and defining an annular receptacle, and an annular seal received in the receptacle of the valve body, the seal comprising an annular contact surface whereby the strikeface of the valve body and the contact surface of the seal define an annular contact shoulder of the valve configured to contact a valve seat of the displacement pump when the valve is in a closed position, wherein the seal defines a cumulative displacement ratio of (i) at least one of at most 0.20 at a location that is spaced 40% from an inner diameter (ID) of the contact surface of the seal moving towards an outer diameter (OD) of the contact surface, (ii) at most 0.35 at a location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and (iii) at most 0.45 at a location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In some embodiments, the seal defines the cumulative displacement ratio of at most 0.20 at the location that is spaced 40% from the ID of the contact surface moving towards the OD of the contact surface, at most 0.35 at the location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and at most 0.45 at the location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In some embodiments, wherein the seal defines a cumulative displacement ratio of at most 0.30 at a location that is spaced 50% from the ID of the contact surface moving towards the OD of the contact surface. In certain embodiments, the seal defines a cumulative displacement ratio of at most 0.35 at the location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface. In certain embodiments, the seal has an integrated cumulative displacement ratio of 0.31 or less. In some embodiments, the contact surface of the seal comprises an annular radially inner frustoconical surface extending radially outwards from the ID of the contact surface, a radially outer annular convex surface extending radially inwards from the OD of the contact surface, and an annular concave interface positioned between the frustoconical surface and the convex surface.

An embodiment of a valve for a displacement pump comprises a valve body having an annular strikeface and defining an annular receptacle, and an annular seal received in the receptacle of the valve body, the seal comprising an annular contact surface whereby the strikeface of the valve body and the contact surface of the seal define an annular contact shoulder of the valve configured to contact a valve seat of the displacement pump when the valve is in a closed position, wherein the seal has an integrated cumulative displacement ratio of 0.31 or less. In some embodiments, the seal has an integrated cumulative displacement ratio of 0.26 or less. In some embodiments, the seal has an integrated cumulative displacement ratio of 0.21 or less. In certain embodiments, the seal defines a cumulative displacement ratio of (i) at least one of at most 0.20 at a location that is spaced 40% from an inner diameter (ID) of the contact surface of the seal moving towards an outer diameter (OD) of the contact surface, (ii) at most 0.35 at a location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and (iii) at most 0.45 at a location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In certain embodiments, the seal defines the cumulative displacement ratio of at most 0.20 at the location that is spaced 40% from the ID of the contact surface moving towards the OD of the contact surface, at most 0.35 at the location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and at most 0.45 at the location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In some embodiments, the contact surface of the seal comprises an annular radially inner frustoconical surface extending radially outwards from an inner diameter (ID) of the contact surface, a radially outer annular convex surface extending radially inwards from an outer diameter (OD) of the contact surface, and an annular concave interface positioned between the frustoconical surface and the convex surface.

An embodiment of a valve for a displacement pump comprises a valve body having an annular strikeface and defining an annular receptacle, and an annular seal received in the receptacle of the valve body, the seal comprising an annular contact surface whereby the strikeface of the valve body and the contact surface of the seal define an annular contact shoulder of the valve configured to contact a valve seat of the displacement pump when the valve is in a closed position, wherein the contact surface of the seal extends between an inner diameter (ID) and an outer diameter (OD) and comprises an annular radially inner frustoconical surface extending radially outwards from the ID of the contact surface, a radially outer annular convex surface extending radially inwards from the OD of the contact surface, and an annular concave interface positioned between the frustoconical surface and the convex surface. In some embodiments, the strikeface of the valve body extends at a first angle to a horizontal that extends normally relative to a central axis of the valve, and the frustoconical surface extends at a second angle from the horizontal that is less than the first angle. In some embodiments, the seal defines a cumulative displacement ratio of (i) at least one of at most 0.20 at a location that is spaced 40% from the ID of the contact surface of the seal moving towards the OD of the contact surface, (ii) at most 0.35 at a location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and (iii) at most 0.45 at a location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In certain embodiments, the seal defines the cumulative displacement ratio of at most 0.20 at the location that is spaced 40% from the ID of the contact surface moving towards the OD of the contact surface, at most 0.35 at the location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface; and at most 0.45 at the location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface. In certain embodiments, the seal has an integrated cumulative displacement ratio of 0.31 or less.

DETAILED DESCRIPTION

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 (for example 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% (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.

As previously described, displacement pumps such as well service pumps include a fluid end having a suction valve and a discharge valve disposed in a valve-over-valve arrangement. The suction valve of the displacement pump may seat against a suction valve seat when in a closed position restricting fluid flow through a suction of the displacement pump. Similarly, the discharge valve of the displacement pump may seat against a discharge valve seat when in a closed position restricting flow through a discharge of the displacement pump. Each of the suction valve and the discharge valve may include a valve body having an annular strikeface and an annular elastomeric seal connected to the valve body, the elastomeric seal having a contact surface.

The strikeface of the valve body and the contact surface of a given valve of a displacement pump are each configured to land and seat against the corresponding valve seat of the pump when the valve is in a closed position. The seal, being of a pliable material, may cushion the impact between the strikeface of the valve body and the valve seat. Particularly, a portion of the volume of the seal is displaced in response to contact between the contact surface of the seal and the valve seat. Displacement of the seal may damage the seal gradually degrading the performance of the seal until the seal (or the entire valve) must be replaced. Specifically, the portion of the displacement volume located at or near an inner diameter (ID) of the contact surface must flow a great distance radially outwards towards an outer diameter (OD) of the contact surface in response to contact between the seal and the valve seat, producing a substantial amount of heat, stress, and corresponding strain in the radially inner portion of the displacement volume.

Additionally, during the operational life of the displacement pump, the strikeface of the valve body may gradually wear in response to repeated contact between the strikeface and the valve seat. Wear to the strikeface exacerbates the elevated levels of heat, stress, and strain subjected to the radially inner portion of the displacement volume of the seal, accelerating the wear occurring to the seal and thereby reducing the operational life of the seal. These issues may of course be aggravated by operating the displacement pump at elevated pressures and temperatures in order to achieve a desired discharge pressure.

Accordingly, embodiments of durable valves for displacement pumps such as well service pumps are disclosed herein. Particularly, embodiments of durable valves are disclosed herein which include an annular seal configured to decrease the amount of displacement volume of the seal located at or near the ID of a contact surface of the seal. The displacement volume of the seal is instead shifted towards the OD of the contact surface where the heat, stress, and strain subjected to the displacement volume is less severe than that subjected to the radially inner portion of the displacement volume. By minimizing the amount of displacement volume at or near the ID of the contact surface (while leaving enough displacement volume to cushion the impact of the strikeface against the valve seat) the degree of heat, stress, and strain experienced by the seal during operation may be minimized, thereby maximizing the operational life of the seal.

In some embodiments, the radially outwards shift of the displacement volume is at least partially accomplished through the geometry of the contact surface of the seal. For example, the contact surface of the seal may include a radially inner frustoconical surface, a radially outer convex surface, and a concave interface formed between the inner frustoconical surface and the outer convex surface.

Referring toFIG.1, a displacement pump10is shown. In this exemplary embodiment, displacement pump10is well service pump having internal plungers28, and thus is referred to as a plunger pump10; however, in other embodiments, pump10may comprise other types of displacement pumps known in the art such as drilling pumps, mining pumps, and pumps utilized in other industrial applications. In this exemplary embodiment, well service pump10generally includes a fluid end12and a power end14coupled to a fluid end12via a plurality of stray rods or fasteners13.

The fluid end12of well service pump10includes a fluid end housing15which comprises a fluid chamber16, a suction bore18A, a discharge bore18B, a plunger bore20A, and an access bore20B, each of which intersect fluid chamber16. In this exemplary embodiment, suction bore18A and discharge bore18B of fluid end housing15are opposed and axially aligned along a common longitudinal axis. Suction bore18A of fluid end housing15is in selective fluid communication with a suction manifold21via a suction valve23A of fluid end12. Similarly, the discharge bore18B of fluid end housing15is in selective fluid communication with a discharge port25via a discharge valve23B of fluid end12. Fluid end12of well service pump10additionally includes a suction valve seat29A positioned in suction bore18A of fluid end housing15and a discharge valve seat29B positioned in the discharge bore18B of fluid end housing15. In some embodiments, discharge valve seat29B may be coupled to fluid end housing15via frictional contact, an interference fit, a connector positioned on discharge valve seat29B, and/or via a separate retainer used to fasten discharge valve seat29B with fluid end housing15. In some embodiments, suction valve seat29A may be coupled to fluid end housing15via frictional contact, an interference fit, a connector positioned on suction valve seat29A, and/or via a separate retainer used to fasten suction valve seat29A with fluid end housing15.

Suction valve23A of fluid end12is biased into engagement or contact with suction valve seat29A via a suction biasing member27A while discharge valve23B is biased into engagement or contact with discharge valve seat29B via a discharge biasing member27B. When suction valve23A is in contact with suction valve seat29A, fluid communication is restricted between suction manifold21and the fluid chamber16of fluid end housing15. Similarly, fluid communication is restricted between discharge port25and fluid chamber16when discharge valve23B contacts discharge valve seat29B.

In this embodiment, well service pump10additionally includes a plunger28slidably positioned in plunger bore20A. Plunger28may reciprocate into and out of the fluid chamber16in response to the actuation of a crank mechanism34of the power end14of well service pump10. During a suction stroke of plunger28, plunger28is withdrawn from the fluid chamber16into the plunger bore20A, thereby drawing fluid from the suction manifold21, through suction valve23A, and into fluid chamber16of fluid end housing15. During the suction stroke of plunger28, the suction valve23A is lifted off the suction valve seat29A when the force of the fluid from the fluid chamber16overcomes the force of suction biasing member27A. Fluid flows into fluid chamber16from suction manifold21in response to the suction valve23A being lifted from the suction valve seat29A.

During a discharge stroke of plunger28, plunger28displaces or extends from the plunger bore20A into fluid chamber16, whereby plunger28forces fluid in fluid chamber16through discharge valve23B and into the discharge port25of fluid end housing15. During the discharge stroke of plunger28, the discharge valve23B is lifted off the discharge valve seat29B when the force of the fluid from the fluid chamber16overcomes the force of discharge biasing member27B. Fluid flows into discharge port25from fluid chamber16in response to the discharge valve23B being lifted from the discharge valve seat29B.

Referring toFIG.2, a valve seat50and a conventional valve100for a displacement pump such as the well service pump10ofFIG.1is shown. In some embodiments, the suction valve seat29A or the discharge valve seat29B may comprise the valve seat50shown inFIG.2. In this exemplary embodiment, valve seat50has a first end52, a second end54longitudinally opposite first end52, and a central bore or passage56defined by a generally cylindrical inner surface58extending between ends52and54. Additionally, valve seat50defines an annular seating surface60that is located proximate the first end52of valve seat50. Particularly, the seating surface60extends radially between an inner diameter (ID)62of the seating surface60and an outer diameter (OD)64of the seating surface60. Additionally, a seat radius66is defined by the seating surface60and which extends annularly between the ID62and OD64of the seating surface60.

Conventional valve100generally includes a valve body102and an annular insert or seal120connected to the valve body102. Particularly, valve body102of conventional valve100includes an annular strikeface104extending radially outwards from an ID106of the valve body102, and an annular receptacle108extending radially inwards into the valve body102from an OD110thereof. Seal120is formed from a pliable material such as an elastomeric material and defines an annular contact surface122which extends radially between an ID124of the contact surface122and an OD126of the contact surface122. In this example, the OD126of contact surface122is comparable to the OD110of valve body102; however, it may be understood that in other instances the OD of a given valve body may vary from the OD of the contact surface. For example,100may be overmolded such that OD110of valve body102is greater than the OD126of contact surface122. Additionally, the contact surface122of the seal120defines seal radius128which extends annularly between the ID124and OD126of the contact surface122. Contact surface122is planar extending at a fixed, inclined angle between the ID124and the OD126thereof. However, it may be understood that the geometry of the contact surface122of seal120may vary.

The contact surface122of seal120is the portion of the exterior surface of seal120which contacts the seating surface60of the valve seat50when the valve100is in a closed position with respect to the valve seat50as shown inFIG.2. Thus, an entirety of the contact surface122of seal120falls within the seating radius66defined by the seating surface60. In other words, the ID124of contact surface122is greater than the ID62of seating surface60while the OD126of contact surface122is less than the OD64of seating surface60. The contact surface122of the seal120and the strikeface104of the valve body102of valve100collectively form or define a contact shoulder107of the valve100.

A portion of the volume of the seal120of conventional valve100is displaced in response to contact between the contact surface122of seal120and the seating surface60. As shown particularly inFIG.2, a portion of the seal120, referred to herein as the displacement volume130, enters into interference with valve seat50such that an entirety of the displacement volume130must displace or flow away from its original or rest position (corresponding to an open position of conventional valve100) to a second or displaced position (corresponding to a closed position of conventional valve100) to thereby permit the strikeface104of valve100to contact the seating surface60of valve seat50.FIG.2shows displacement volume130in its rest position in interference with valve seat50and thus is not an accurate representation of how the displacement volume130flows into its displaced position response to contact between the contact surface122of seal120and the seating surface60of valve seat50. Although not shown inFIG.2, it may be understood that the displacement volume130of seal120flows radially outwards in the direction of the OD126of contact surface122when displacement volume130is displaced from its rest position to its displaced position.

FIG.2is meant to illustrate the geometry of displacement volume130with seal120in an undisturbed state. Particularly, the contact surface122of seal120in this example is planar in shape and extends at an acute angle relative to the angle (relative to the horizontal) from which strikeface104of the valve body102extends. However, it may be understood that the geometry of the contact surface122of conventional seals like seal120may vary somewhat in shape. As shown inFIG.2, in the rest position the displacement volume130of seal120extends substantially if not entirely between the ID124and the OD126of the contact surface122. In this configuration, the elastomeric material comprising seal120must be displaced or flow across substantially the entire radius of seal120beginning at ID124of contact surface122. In other words, a substantial volume of the elastomeric material comprising seal120is displaced in response to the seal120shifting between the rest and displaced positions. The displacement volume130of seal120therefore repeatedly undergoes a high degree of stress and strain each time conventional valve100is shifted from the open position to the closed position.

Additionally, given that the displacement volume130extends at least substantially to the ID124of the contact surface122, the portion of the displacement volume130located proximal to the ID124of contact surface122may be displaced a greater distance in response to seal120shifting into the displaced position than the portion of displacement volume130located proximal to the OD126of contact surface122. Thus, a radially inner half of displacement volume130(the portion of seal120extending radially between ID124and a midway point or middle of seal radius128) may experience a greater degree of stress and strain than a radially outer half (the portion of seal120extending radially between OD126and the midway point of seal radius128) of displacement volume130. The repeated elevated stress and strain experienced by the radially inner half of displacement volume130may result in advanced fatigue and deterioration of the radially inner half of displacement volume130relatively early in the operational life of seal120, potentially inhibiting the seal120from effectively sealing the annular interface formed between valve seat50and conventional valve100. This deterioration of the radially inner half of displacement volume130may be accelerated in some instances by the normal wear that occurs to the strikeface104of valve body102during the operation of conventional valve100.

Referring now toFIG.3, an embodiment of a durable valve200for a displacement pump having a central or longitudinal axis205and generally including a valve body202and an annular durable seal250is shown. As an example, the durable valve200shown inFIG.3may comprise the suction valve23A or discharge valve23B of the displacement pump10shown inFIG.1. As will be described further herein, durable seal250is configured to minimize the size of the radially inner half of a displacement volume260of the durable seal250.

In this exemplary embodiment, valve body202of durable valve200includes an annular strikeface204extending radially between an ID206and an OD208. Additionally, an outer surface of the valve body202defines an annular receptacle210which receives at least a portion of the durable seal250and extends radially outwards to an OD212of the valve body202. In this exemplary embodiment, valve body202is coupled to a plurality of wings240which extend through the central passage56of valve seat50to centralize the durable valve200with respect to the valve seat50. However, it may be understood that in other embodiments the valve body202may not be connected to (or comprise itself) the wings240shown inFIG.3.

Durable seal250of durable valve200is formed from a pliable material such as an elastomeric material and defines an annular contact surface252extending radially between an ID254of the contact surface252and an OD256of the contact surface252. Additionally, the contact surface252of the durable seal250defines a seal radius258which extends annularly between the ID254and OD256of the contact surface252. The geometry of the contact surface252of durable seal250will be described further herein. The contact surface252of the seal250and the strikeface204of the valve body202of durable valve200collectively form or define a contact shoulder207of the durable valve200.

As with the contact surface122of seal120shown inFIG.2, the contact surface252of durable seal250shown inFIG.3is the portion of the exterior surface of durable seal250which contacts the seating surface60of the valve seat50when the durable valve200is in a closed position with respect to the valve seat50as shown inFIG.3. Thus, in this exemplary embodiment, an entirety of the contact surface252of durable seal250falls within the seating radius66defined by the seating surface60. In other words, the ID254of contact surface252is greater than the ID62of seating surface60while the OD256of contact surface252is less than the OD64of seating surface60.

Also as with the seal120shown inFIG.2, a portion of the volume of the durable seal250of the durable valve200shown inFIG.3is displaced in response to contact between the contact surface252of durable seal250and the seating surface60of valve seat50. Particularly, a displacement volume260of durable seal250enters into interference with valve seat50such that an entirety of the displacement volume260must displace or flow away from its original or rest position to a second or displaced position spaced from the rest position to thereby permit the strikeface204of valve body202to contact the seating surface60of valve seat50.FIG.3shows displacement volume260in its rest position in interference with valve seat50and thus is not an accurate representation of how displacement volume260flows into its displaced position in response to contact with the seating surface60of valve seat50.

Unlike the displacement volume130of seal120shown inFIG.2, the radially inner half of displacement volume260(the portion of displacement volume260extending between ID254and a midway point or middle of seal radius258) is minimized in size relative to the radially outer half of displacement volume260(the portion of displacement volume260extending between OD256and the midway point of seal radius258). In this configuration, the radially inner half of displacement volume260is substantially smaller than the radially outer half of displacement volume260. By minimizing the mount of displacement volume260located near ID254of contact surface252, the total amount of flow or displacement of the displacement volume260resulting from the shifting of displacement volume260between the rest and displaced positions is minimized given that less elastomeric material of the seal250must flow radially outwards from the ID254of contact surface252. By minimizing the total amount of displacement that occurs to displacement volume260as volume shifts between the rest and displaced positions, the amount of stress and strain to which the displacement volume260, and particularly the radially inner half of volume260, is exposed may in-turn be minimized, maximizing the operational life of the durable seal250even as the strikeface204of valve body202begins to wear thereby applying greater stress and strain to the radially inner half of displacement volume260.

Referring toFIGS.2-4, a graph300is shown inFIG.4showing cumulative displacement ratios of several valves for the seals of displacement pumps as a function of radial location. Particularly, graph300compares a first cumulative ratio of displaced seal volume310corresponding to the seal120shown inFIG.2with a second cumulative ratio of displaced seal volume320corresponding to the durable seal250shown inFIG.3. Particularly, graph300illustrates a ratio of displaced seal volume for each seal120and250as a function of the seal radius128,258for the given seal120,250. For example, first cumulative displacement ratio310of graph300illustrates that at approximately 32% between ID124and OD126of contact surface122the first cumulative displacement ratio310of displacement volume130is approximately 0.20, while at approximately 72% between ID124and OD126of contact surface122the first cumulative displacement ratio310of displacement volume130is approximately 0.60. As an example, if the ID124is equal to 5.00 inches (in) and the OD126is equal to 6.00 in, then 32% from the ID124to the OD126of contact surface122would equal approximately 5.32 in while 72% from the ID124to the OD126of contact surface122would equal approximately 5.72 in. Additionally, if the displacement volume130is equal to 0.50 cubic inches (in3) then the first cumulative displacement ratio310at 32% from the ID124would equal approximately 0.10 in3, while the first cumulative displacement ratio310at 72% from the ID124would equal approximately 0.30 in3.

Graph300illustrates how the radially inner half of the displacement volume260of durable seal250is substantially less than the radially outer half of displacement volume260such that a majority of the displacement volume260has been positioned along the radially outer half of volume260. For example, at 50% from the ID254of contact surface252(the midway point between ID254and OD256) the second cumulative displacement ratio320is equal to only approximately 0.18. In other words, less than 20% of the displacement volume260of durable seal250is located between the ID254and the radial midway point between ID254and OD256of contact surface252, while over 80% of the displacement volume260of durable seal250is located between the midway point and OD256of contact surface252. Thus, little of the displacement volume260of durable seal250is forced to flow or displace from the radially inner half thereof towards the OD256in response to shifting of the displacement volume260from the rest position to the displaced position, thereby minimizing the amount of stress and strain experienced by the displacement volume260as durable seal250shifts between the rest and displaced positions. Conversely, at 50% of the ID124of the contact surface122of seal120the first cumulative displacement ratio310is equal to approximately 0.35. Thus, a substantially larger share of displacement volume130resides between ID124and the midway point of seal radius128, resulting in a relatively greater amount of stress and strain experienced by the displacement volume130of conventional seal120as the volume130is shifted between rest and displaced positions. While it may be understood that the geometry of the displacement volume of conventional seals may vary to a degree, the cumulative displacement ratio of conventional seals increases much more rapidly for conventional seals moving away from the ID thereof as compared to the second cumulative displacement ratio320of durable seal250moving radially outwards from the ID254thereof. The reduced cumulative displacement ratio along the radially inner half of displacement volume260reduces wear of durable seal250along the ID254of contact surface252, thereby maximizing the operational life of valve200as the strikeface204of valve body202wears away subjecting the ID254to greater-and-greater stress and strain.

It may be understood that the ratio of displaced seal volume as a function of seal radius of the durable seal250shown inFIG.3may vary from the second cumulative displacement ratio320shown in graph300. For example, in some embodiments, at most 75% of the displacement volume260of durable seal250is displaced at a location 90% from the ID254(the ratio at 90% from ID254is at most 0.75) when the displacement volume260is in the displaced position. In some embodiments, at most 65% of the displacement volume260of durable seal250is displaced at a location 80% from the ID254when the displacement volume260is in the displaced position. In certain embodiments, at most 55% of the displacement volume260of durable seal250is displaced at a location 75% from the ID254the displacement volume260is in the displaced position. In some embodiments, at most 50% of the displacement volume260of durable seal250is displaced at a location 70% from the ID254when the displacement volume260is in the displaced position. In some embodiments, at most 45% of the displacement volume260of durable seal250is displaced at a location 65% from the ID254the displacement volume260is in the displaced position. In some embodiments, at most 40% of the displacement volume260of durable seal250is displaced at a location 60% from the ID254when the displacement volume260is in the displaced position. In certain embodiments, at most 35% of the displacement volume260of durable seal250is displaced at a location 55% from the ID254when the displacement volume260is in the displaced position. In certain embodiments, at most 30% of the displacement volume260of durable seal250is displaced at a location 50% from the ID254when the displacement volume260is in the displaced position. In certain embodiments, at most 25% of the displacement volume260of durable seal250is displaced at a location 45% from the ID254the displacement volume260is in the displaced position. In certain embodiments, at most 20% of the displacement volume260of durable seal250is displaced at a location 40% from the ID254the displacement volume260is in the displaced position. In certain embodiments, at most 15% of the displacement volume260of durable seal250is displaced at a location 35% from the ID254the displacement volume260is in the displaced position. In some embodiments, at most 10% of the displacement volume260of durable seal250is displaced at a location 30% from the ID254the displacement volume260is in the displaced position. In certain embodiments, at most 55% of the displacement volume260of durable seal250is displaced at a location 75% from the ID254the displacement volume260is in the displaced position.

The cumulative displacement ratio of durable seal250as a function of seal radius (moving from the ID254of contact surface252to the OD256thereof) may be expressed as a curve fit. Particularly, in some embodiments, the portion of the cumulative displacement ratio of durable seal250extending from the ID254to 70% from the ID254is expressible as a linear curve fit having a slope of approximately between 0.98 and 0.99 and a Y-intercept of approximately between −0.10 and −0.2. For example, a linear curve fit330is shown inFIG.4of a portion of the second cumulative ratio of displaced seal volume320extending between ID254and a location spaced 70% from the ID254. In other words, linear curve fit330is formed from the points of the second cumulative ratio of displaced seal volume320located inclusively between 0% and 70% of the percentage of the seal radius shown along the X-axis of graph300. In this exemplary embodiment, linear curve fit330has a slope of 1.00; however, it may be understood that in other embodiments the slope of linear curve fit330may vary. For example, in some embodiments, the slope of linear curve fit330is equal to or less than 0.99. In still other embodiments, the slope of linear curve fit330is equal to or less than 0.98. In certain embodiments, the Y-intercept of linear curve fit is between −0.10 and −0.50. In certain embodiments, the Y-intercept of linear curve fit is between −0.15 and −0.30.

The cumulative displacement ratio of durable seal250(and for other seals) may be integrated across the diameter of the seal to provide an integrated cumulative displacement ratio. For example, the cumulative ratio of displaced seal volume320may be integrated across the interval extending from the ID254to the OD256of durable seal whereby durable seal250has an integrated cumulative displacement ratio (indicated by arrow321inFIG.4) that is equal to 0.31 or less. In other words, the area under the curve defined by the cumulative ratio of displaced seal volume320across the interval extending entirely from ID254to OD256is a value equal to 0.31 or less. In some embodiments, the integrated cumulative displacement ratio321of durable seal250is 0.26 or less. In some embodiments, displacement ratio321of durable seal250is 0.21 or less. In certain embodiments, displacement ratio321of durable seal250is 0.16 or less.

Seal120similarly has an integrated cumulative displacement ratio (indicated by arrow311inFIG.4) across the interval from ID124to OD126that is greater than 0.31. Thus, as used herein, the term “integrated cumulative displacement ratio” is defined as the integrated cumulative ratio of displaced seal volume entirely across a diameter of an annular contact surface of the seal which extends from an ID of the annular contact surface to an OD of the annular contact surface. Durable seal250has a smaller integrated cumulative displacement ratio321than convention seal120(integrated cumulative displacement ratio311) given that a greater amount of the volume of durable seal250is concentrated near the OD256of the contact surface252as described above so as to minimize displacement volume260and concentrate the remaining displacement volume260near OD256. Conventional seal120, having a large displacement volume130that is not advantageously concentrated near OD126of the contact surface122of seal120, thus has a larger integrated cumulative displacement ratio. Thus, the integrated cumulative displacement ratio of a given seal generally declines as more of the displacement volume of the given seal is concentrated near the OD of the contact surface of the seal.

Referring now toFIGS.5,6, views of the durable seal250of durable valve200with the displacement volume260thereof in the rest position are shown. It may be understood that the description of durable seal250that follows in only exemplary and the geometry of durable seal250may vary in other embodiments. As shown byFIGS.5,6, the displacement volume260of seal250corresponds to the volume of seal250falling between the contact surface252and a projection of the strikeface204that extends radially outwards at an angle214to the horizontal (an axis extending normally from central axis205).

In this exemplary embodiment, the contact surface252of seal250is formed from or contains several surfaces including a radially inner frustoconical surface270, and a radially outer convex surface272. Frustoconical surface270extends radially outwards from the ID254of contact surface252while the convex surface272extends radially inwards from the OD256of surface252such that surfaces270and272intersect at an annular, concave interface274located between the surfaces270and272. The inner frustoconical surface270extends across an annular radius271between the ID254of contact surface252and the concave interface274. In some embodiments, the annular radius271of inner frustoconical surface270is between approximately 30% and 60% of the total radius or radial width of durable seal250; however, it may be understood that the size of annular radius271relative to the total radius of durable seal250may vary.

The inner frustoconical surface270of seal250may be planar and extend at a non-zero angle relative to the strikeface204of valve body202. For example, strikeface204may extend at angle214relative to the horizontal while the frustoconical surface270extends at an angle273relative to the horizontal, where angle273is less than angle214. In some embodiments, angle214is between approximately 30 degrees and 50 degrees from the horizontal, while angle273is between approximately 10 degrees and 30 degrees. In some embodiments, angle273is between approximately 5 degrees and 15 degrees less than angle214. A relatively small difference between the angle273of frustoconical surface270and the angle214of strikeface204may minimize the amount of displacement volume260located near the ID254of contact surface252while still leaving some cushion near the ID254to prevent excessive wear to the strikeface204of valve body202. However, it may also be understood that in other embodiments the magnitude of angles214and273as well as the magnitude of the difference between angles214and273may vary.

In this exemplary embodiment, the convex surface272of seal250is defined by an annular, bulb-shaped convex curve which projects outwardly and towards the seat surface60of valve seat50. By bulging the contact surface252outwards near the OD256of contact surface252, convex surface272assists in shifting the majority of the displacement volume260towards the OD256of surface252and away from the ID254thereof. In this configuration, a first distance or gap275is formed between the planar projection of the strikeface204of valve body202and a crest276of the convex surface272. In some embodiments, the first gap275is between approximately 0.050 inches and 0.150 inches; however, the geometry of crest276and thus the magnitude of first gap275may vary in other embodiments.

A second distance or gap277(shown inFIG.6) is formed between crest276and a projection of the frustoconical surface270. Additionally, a third distance or gap279is formed between crest276and a projection of the strikeface204. The second gap277is less than the third gap279given that the angle214between strikeface204and the horizontal is greater than the angle273formed between frustoconical surface270and the horizontal. In some embodiments, the second gap277is 50% or less of the magnitude of third gap279. In some embodiments, the second gap277is 35% or less of the magnitude of third gap279; however, it may be understood that the difference in magnitude between gaps277and279may vary.