FLUID END WITH REMOVABLE DUAL-VALVE CARTRIDGE

A fluid end assembly is described herein with a flow box having an inlet manifold having an inlet opening, an outlet manifold having an outlet opening, and a housing between the inlet manifold and the outlet manifold; and a valve cartridge removably disposed in the housing. In one embodiment, the valve cartridge includes a sleeve with a first end and a second end; a valve seat at each of the first and second ends; a first valve disposed in the sleeve at the first end; and a second valve disposed in the sleeve at the second end.

FIELD

Embodiments described herein relate to fluid ends for high pressure pumps.

BACKGROUND

High pressure pumps used in industries such as oil and gas have a plurality of linear force members, such as pistons or plungers, coupled to a crankshaft that rotates to cause the linear force member to reciprocate. The linear force member heads extend and retract inside a fluid end that channels the fluid flow powered by the linear force members. The flow channel of the fluid end is typically perpendicular to the stroke axis of the linear force member. During the suction phase of the stroke, the linear force member retracts producing a vacuum inside the fluid end. A suction valve inside the fluid end on the inlet side has fluid pressure on one side of the valve and internal pressure of the fluid end on the other side. As the linear force member retracts, declining pressure on the internal side of the suction valve causes the suction valve to retract, allowing fluid into the fluid end. During the power phase of the stroke, the linear force member then advances raising the pressure on the fluid in the fluid end. The pressure reseats the suction valve, closing the inlet side of the fluid end. A discharge valve inside the fluid end on the discharge side has line pressure on the outside of the valve and internal pressure of the fluid end on the inside of the valve. As the linear force member increases pressure inside the fluid end, the discharge valve opens, allowing fluid from the fluid end to flow through the valve into the line, exiting the fluid end. The stroke then repeats, with the discharge valve closing and the suction valve opening again.

The valves must seat and seal during each stroke to avoid fluid flow in the wrong direction. Typically, the valves use springs to bias each valve closed. Spring constants are chosen such that pressures developed upstream, downstream, and within the fluid end cause the valves to open at appropriate times and the springs cause the valves to close when the pressure equalizes. The valves are typically held in place by a fluid end cap that fastens to the fluid end and seals fluid into the assembly.

In conventional fluid ends, the valves seat directly against portions of the fluid end. The fluid end is a sizable object that can house two, three, or more valve assemblies, each comprising a suction and discharge valve. Every stroke of the linear force member results in a valve contacting a portion of the fluid end, which must be shaped to match the valve shape and form a seal. This causes wear on the fluid end and valves, which must eventually be replaced. If a valve is damaged, the fluid end cap must be removed and the valve extracted. Specialized tools are frequently needed to extract the valves. Further, the fluid end must be specially designed to fit the shape of the valves. There is a need for a fluid end that does not require such specialized design and handling.

SUMMARY

Embodiments described herein provide a fluid end assembly, comprising a flow box with an inlet manifold having an inlet opening, an outlet manifold having an outlet opening, and a housing between the inlet manifold and the outlet manifold; and a valve cartridge removably disposed in the housing, the valve cartridge comprising a first valve seat at a first end of the cartridge assembly and a second valve seat spaced apart from the first end; a first valve disposed in the cartridge assembly at the first end; a second valve disposed adjacent to the second valve seat; a first resilient member disposed between the first and second valves in contact with the first valve and the second valve; and a second resilient member disposed between the second valve and a second end of the cartridge assembly opposite the first end.

Other embodiments described herein provide a valve cartridge, comprising a cage comprising a first valve seat and a second valve seat; a first valve disposed in the cage, the first valve having a first stem and a first plug portion; a second valve disposed in the cage, the second valve having a second stem and a second plug portion, wherein the second stem is hollow and the first stem fits within the second stem; a first resilient member disposed within the second stem between the first stem and the second plug portion; and a second resilient member disposed between the second plug portion and the cage, wherein the second valve seat is between the first plug portion and the second plug portion.

Other embodiments described herein provide a valve cartridge, comprising a first valve aligned with a second valve; a first valve seat at a first end of the valve cartridge adjacent to the first valve; a second valve seat between the first valve and the second valve; and a resilient member between the first valve and the second valve in contact with the first valve and the second valve.

DETAILED DESCRIPTION

FIG. 1is a front view of a fluid end assembly100coupled to a pump102. The fluid end assembly100includes a flow box104with an inlet106, which is a suction side, and an outlet108, which is a discharge side. The flow box104includes an inlet manifold (not visible inFIG. 1) and an outlet manifold110. Fluid being pumped flows into the flow box104through the inlet106into the inlet manifold, through valves to be described further below, into the outlet manifold110, and through the outlet108. Piping is typically connected to the inlet106and the outlet108to carry fluid to and from the flow box104.

A plurality of valve cartridges112is disposed in the flow box104dividing the inlet manifold from the outlet manifold110. In the embodiment ofFIG. 1, three valve cartridges112are shown, but the fluid end assembly100may include any number of valve cartridges112. A fluid end cap118is removably attached to the flow box104, typically at an upper region thereof, or at the outlet or discharge side thereof, to enclose the fluid end assembly100. When the fluid end cap118is removed, the valve cartridges112are removable from the flow box104by lifting the valve cartridges112from the flow box104through the outlet manifold.

The fluid end assembly100is coupled to a casing114of the pump at a force end116thereof. The fluid end assembly100has a plurality of openings (not visible inFIG. 1) for accommodating linear force members disposed in the pump casing114such that the linear force members can apply pressure to fluid inside the fluid end assembly100. The linear force members are coupled to a power module120, which may include a crankshaft. The power module120causes the linear force members to reciprocate, extending toward and away from the fluid end104through an adapter122. Openings (not visible) in the adapter122register with the openings in the flow box104to allow the linear force members to pressurize fluid in the flow box104.

FIG. 2is a cross-sectional view of one of the valve cartridges112in operating position in the flow box104. The valve cartridge112includes a first valve201and a second valve200. The first valve201is disposed in a sleeve206, at a first end210thereof, and the second valve200is disposed adjacent to a second end212of the sleeve206. The sleeve206is disposed in a housing208in the flow box104. The sleeve206is a cylindrical object with an outer diameter similar to an inner diameter of the housing.

In the embodiment ofFIG. 2, a first valve seat202is optionally disposed in the first end210of the sleeve206, and a second valve seat204is optionally disposed in the second end212of the sleeve206. The first valve seat202is disposed between the first valve201and the first end210of the sleeve206. The second valve seat204is disposed between the second valve200and the second end212of the sleeve206. The valve seats202and204each have a seating surface203that engages a seating surface205of each valve201and200.

The first end210of the sleeve206has a lip214that extends radially inward from the first end210. The second end212of the sleeve206has a lip216that extends radially outward from the second end212. Each valve seat202and204has a lip215that extends radially outward and engages a portion of the sleeve206to stabilize the valve seat. At the first end210of the sleeve206, the lip215of the first valve seat202engages the lip214at the first end210of the sleeve206. At the second end212of the sleeve206, the lip215of the second valve seat204engages directly with the second end212of the sleeve206. The first valve201thus operates inside the sleeve206while the second valve200operates outside, and adjacent to the sleeve206.

The valve seats202and204are optional because the sleeve206may be configured with sealing surfaces to engage the sealing surfaces205of the valves directly. For example, valve landings (not shown inFIG. 2) may be shaped directly into the wall of the sleeve206at appropriate locations to provide sealing surfaces to engage the sealing surfaces205of the valves. Further description of such optional sealing surfaces is provided below in connection withFIG. 3.

The sleeve206has an opening213in registration with an opening (not shown) in the flow box104to allow fluid communication to the power adaptor122(FIG. 1). The opening213typically has an axis orthogonal to a general direction of fluid flow through the valve cartridge112.

Each of the first valve seat202and the second valve seat204has a first end218and a second end220. In the embodiment ofFIG. 2, the first end218of each valve seat has a diameter greater than a diameter at the second end220. The lip215of each valve seat has a planar surface224extending along a plane perpendicular to an axis of the valve cartridge112, which is also an axis of movement of the valves200and201, and the axis of general fluid flow through the valve cartridge112. Each valve200and201moves along its axis, and the axis of the sleeve206substantially corresponds with the axes of the valves202and204.

Each valve seat202and204also has a tapered side226that extends from the lip215at the first end218to the second end220. The lip215protrudes radially outward from the tapered side226such that the planar surface224and the tapered side226define an angle. The tapered side226has a diameter that declines monotonically from the first end218to the second end220. The decline may be linear, may include a linear section, or may be non-linear. Each valve seat202and204remains substantially concentric with the overall axis of the valve along its length.

The tapered side226of each valve seat202and204provides additional stabilization of the valve seat, if desired. The lip215of the first valve seat202engages with the lip214of the sleeve206along the planar surface224. Additionally, and optionally, the tapered side226of the first valve seat202may engage with an inner surface of the lip214at the first end210. The lip214has a tapered inner surface228that matches the tapered side226of the first valve seat202and a planar surface230that matches the planar surface224of the first valve seat202. The tapered surfaces of the first valve seat202and the lip214are optional features. In alternate embodiments, each of the tapered side226of the first valve seat202and the tapered inner surface228of the lip214may be untapered, i.e. vertical in the view ofFIG. 2. Alternately, the tapered surfaces of the first valve seat202and the lip214may be tapered in different ways or at different angles, or one may be vertical while the other is tapered. Additionally, the side226of the valve seat (tapered or untapered) and the inner surface228of the lip214(tapered or untapered) may define a gap, such that the valve seat202engages the lip214only at the planar surface224.

The second valve seat204engages directly with the second end212of the sleeve206. In the embodiment ofFIG. 2, the second valve seat204also optionally engages an inner wall232of the sleeve206at the second end212. The inner wall232is tapered to match the tapered side226of the second valve seat204. The second end212of the sleeve206also has a planar surface234that matches the planar surface224of the lip215of the second valve seat204.

As with the first valve seat202, the side226of the second valve seat204, and the inner wall232of the sleeve206, may alternately be any combination of tapered and untapered, and may define a gap such that the second valve seat204engages with the second end212of the sleeve206only at the planar surface224of the lip215.

It should be noted that the lip215of the first valve seat202may have a radial extent different from the lip215of the second valve seat204. Likewise, the tapered side226of the first valve seat202may have a different taper from the tapered side226of the second valve seat204, which may differ in any or all of linearity, non-linearity, and angle.

Each of the first and second valves201and200is biased closed by a valve restraint240. InFIG. 2, the valve restraints240are springs. The valve restraint240coupled to the first valve201is coupled between a rear217of the first valve201and a stem242of the second valve200. The valve restraint240coupled between the first and second valves201and200is disposed around a rear stem219extending from the rear217of the first valve201and around the stem242of the second valve200which extends from the front of the second valve200toward the first valve201through the interior of the sleeve206. When the first valve201opens due to declining pressure between the first and second valves201and200, the second valve200remains closed and provides a biasing force through the valve restraint240between the first and second valves201and200such that when pressure between the first and second valves201and200equalizes, the biasing force urges the first valve201to seat in the first end210of the sleeve206, stopping fluid flow into the valve cartridge112from the inlet manifold251.

The valve restraint240coupled to the second valve200is coupled to the rear217of the second valve200around the rear stem219of the second valve200. The valve restraint240coupled to the rear217of the second valve200may be coupled between the rear217of the second valve200and a valve cap244, which may be attached to the sleeve206. The valve cap244includes a collar248that removably engages with the sleeve206at the second end212thereof by any convenient means such as press fitting, snap fitting, or threading (in the embodiment ofFIG. 2the collar248engages with the second end212of the sleeve206by a snap fit) and a crown (not visible in the cross-sectional view ofFIG. 2) that extends from the collar248around the rear stem219of the second valve200to back-stop the valve restraint240disposed around the rear stem219of the second valve200.

The valve restraint240coupled to the rear217of the second valve200provides a biasing force to the second valve200, supported by the crown of the valve cap244. When the second valve200opens due to increasing pressure between the first and second valves201and200, the valve restraint240coupled to the rear217of the second valve200compresses and the biasing force increases. As the second valve200moves away from the first valve201, the valve restraint240coupled between the first and second valves201and200may lose contact with the second valve200at the stem242. As pressure between the first and second valves201and200equalizes, the biasing force on the second valve200urges the second valve200to seat in the second end212of the sleeve206(i.e. in the second valve seat204in the embodiment ofFIG. 2), and the stem242moves back into contact with, or close proximity to, the valve restraint240between the first and second valves201and200.

The valve cartridge112is held in place inside the housing208by a cartridge restraint246. The collar248of the valve cap244may have a landing surface250for the cartridge restraint246that faces away from the sleeve206. Alternately, the cartridge restraint246may contact the sleeve206directly at the planar surface234or the lip216. Seals252may be provided at the first and second ends210and212of the sleeve206where the two ends of the sleeve206contact the housing208. Compression is maintained on the seals252by action of the cartridge restraint246, which is compressed between the fluid end cap108(not shown inFIG. 2) and the sleeve206.

FIG. 3is a cross-sectional view of the sleeve206of the valve cartridge112ofFIG. 2. The tapered inner wall232(which is optional as described above) of the sleeve206has a first diameter at a first end302of the tapered inner wall232and a second diameter at a second end304of the tapered inner wall232. The first end302of the tapered inner wall232is at the second end212of the sleeve206, and the second end304connects to a second inner wall306of the sleeve206. The second diameter is less than the first diameter due to the taper of the tapered inner wall232. The second inner wall306has a diameter that may be the same as, or different from, the second diameter, either larger or smaller. In the embodiment ofFIG. 3, the diameter of the second inner wall306is the same as the second diameter.

The opening213of the sleeve206is formed through the wall of the sleeve206, and generally has a diameter less than an outer diameter of the sleeve206. The diameter of the opening213may be the same as, or different from, the diameter of the second inner wall306. In the embodiment ofFIG. 3, the opening213has a diameter that is greater than the diameter of the second inner wall306such that the second inner wall306connects to a curved inner wall308, which has a radius of curvature equal to the radius of the opening213. The curved inner wall308joins a fourth inner wall310which, in the embodiment ofFIG. 3, has a constant diameter substantially equal to the diameter of the opening213. The fourth inner wall310extends from the point of joining with the curved inner wall308to the lip214at the first end210of the sleeve206. Thus, proceeding from the second end212of the sleeve206to the first end210of the sleeve206is the tapered inner wall232, then the second inner wall306, then the curved inner wall308, then the fourth inner wall310. It should be noted that fourth inner wall310may have a diameter that is the same as, or different from, the diameter of the opening213, so long as the fourth inner wall310has a length selected to avoid obstructing the opening213. Thus, the fourth inner wall310may have a diameter greater than the diameter of the opening213. Alternately, the fourth inner wall310may have a diameter less than the diameter of the opening213if the curved inner wall308is extended around the periphery of the opening213to join the fourth inner wall310.

As noted above, the separate valve seats202and204of the valve cartridge112are optional. Shown in phantom inFIG. 3are optional valve seats formed in the sleeve206. A first valve seat312is shown at the first end210and a second valve seat214is shown at the second end212. The first valve seat312has a seating surface316to engage the seating surface205of the first valve201. The seating surface316is angled, or otherwise shaped, to match the seating surface205of the first valve201to provide an operative seal when the first valve201is closed. The second valve seat214likewise has a seating surface318that is angled to match the seating surface205of the second valve200. In each case, the sleeve206is shown with an interior wall320that is different from the tapered inner wall232and the second inner wall306. As shown in phantom the alternative interior wall320of the sleeve206is has a diameter that is equal to a minimum diameter of the seating surfaces316and318. In the case of the seating surface318, the interior wall320of the sleeve206is shown having a constant diameter from the seating surface318to the opening213. For the seating surface316, the interior wall320extending from the seating surface316to the first end210Is shown with constant diameter from the seating surface316to the first end210. Although such features (constant diameter interior wall) simplify manufacture of the sleeve206, the constant diameter of the interior wall extending from the seating surfaces316and318is optional. The interior wall320may be shaped in any convenient way to promote flow of fluid through the valve cartridge112, pressure operation of the valves200and201, or for any other reason.

The sleeve206may be made from any material with structural strength to withstand operating pressures and forces experienced inside the fluid end100and chemically resistant to fluids flowing through the fluid end100. In some cases, the sleeve206may be made of a tough plastic such as polypropylene, polystyrene (for example high impact polystyrene), polybenzimidazole, or hard styrenic polymers such as acrylonitrile butadiene styrene terpolymer. In other cases, the sleeve206may be made of any appropriate metal. The various features of the sleeve206may be accomplished by molding and/or by machining according to standard practices known in the art.

FIG. 4Ais a cross-sectional view of a fluid end assembly400according to another embodiment.FIG. 4Bis a close-up view of the valve cartridge ofFIG. 4A. The flow box104is the same as inFIG. 1, with the inlet106, outlet108, and outlet manifold110. Here, the inlet manifold is visible, labelled402. In the example ofFIG. 4, the fluid end assembly400is shown with a cap403in place covering the outlet manifold110. An inner wall401separates the inlet manifold402from the outlet manifold110and a plurality of openings405provide fluid flow pathways from the inlet manifold402through the inner wall401into the outlet manifold110.

Three valve cartridges404of a different design from the valve cartridge112are disposed in the fluid end assembly400. As noted above, the fluid end assembly400can be configured with any convenient number of valve cartridges404to match the number of linear force members. Each valve cartridge404fits in a housing407formed in the inner wall401. Each housing407is coaxial with one of the openings405.

Each valve cartridge404features a first valve406and a second valve408. The first and second valves406and408are engaged in a telescoping relationship. The second valve408has a hollow stem410with an inner diameter412. The first valve406also has a stem414, shown here as a solid stem, but which may also be hollow. The stem414of the first valve406thus moves within the stem410of the second valve408. The first and second valves406and408have respective plug portions416and418coupled to their respective stems414and410. The stem410and the stem414may be sized with lengths such that an end420of the stem410contacts the plug portion416of the first valve406to define a maximum travel of the stem414within the stem410. A plurality of openings422, in this case horizontal (i.e. perpendicular to the movement axis of the first and second valves406and408), are provided in the second valve408near where the stem410meets the plug portion418of the second valve408to provide hydrostatic balancing as the stem414moves within the stem410. Here, there are four openings422, but any convenient number of openings422may be provided. For example one, two, or three openings422may be provided, or more than four openings422may be provided. Additionally, one, more than one, or all the openings may be angled in any convenient manner, for example toward or away from the first valve406. The hollow stem410of the second valve408is bored axially to a depth that provides a desired travel for the stem414within the stem410.

The first and second valves406and408are housed in a cage424. The cage has an upper portion426and a lower portion428. The lower portion428includes a first seat430for the first valve406and a second seat432for the second valve. A plurality of posts434connect the first seat430to the second seat432to provide structural strength for the lower portion428. The plug portion416of the first valve406travels within the lower portion428of the cage424, while the plug portion418of the second valve408travels within the upper portion426of the cage424. The upper portion426of the cage features a top plate434that provides structural strength for the valve cartridge404, and may, in some cases, provide a contact surface for the cap403. Here, a gap435is provided between the top plate434and the cap403.

The cage424can be molded as one piece including the upper portion426and the lower portion428in a single molded article. Alternately, the upper and lower portions426and428can be separately molded and then welded together. For example, the posts of the upper portion can be welded to the second seat432. The cage424can generally be made of structurally strong plastic or metal selected based on loading, cycling, and chemistry of anticipated service. The example plastics listed above in connection with the sleeve ofFIG. 3can also be used for the cage424.

The lower portion428of the cage424fits within the housing407. The first seat430contacts a floor444of the housing407such that the first seat430is adjacent to the opening405. The first seat430has an inner wall429with a dimension that is substantially the same as a dimension of an inner wall431of the opening405. It should be noted, however, that flow characteristics of the fluid end assembly400can be changed by using a valve cartridge with a first seat that has an inner wall with dimension different from that of the inner wall431of the opening405. For example, if the dimension of the inner wall of the first seat is smaller than the dimension of the inner wall431of the opening405, flow through the fluid end assembly400can be constrained. Such flow characteristics can be changed by swapping a first valve cartridge having a first flow rating with a second valve cartridge having a second flow rating different from the first flow rating, without changing any other pump hardware.

The housing407has a first portion446and a second portion448. The first portion446extends from the floor444to the second portion448. The first portion446has an inner wall447with a dimension larger than the dimension of the inner wall431of the opening405. The second portion448has an inner wall449with dimension larger than the dimension of the inner wall447of the first portion446. As described above, the first seat430contacts the floor444of the housing407. The first seat430has an outer wall450with a dimension that is smaller than the dimension of the inner wall447of the first portion446, so the first seat430contacts the housing407only at the floor444thereof. The second seat432has an outer wall452with a dimension larger than the dimension of the outer wall450of the first seat430and larger than the inner diameter447of the first portion446. The outer diameter452is substantially the same as the inner diameter449of the second portion448such that the second seat432contacts the second portion448at a sidewall thereof. The first portion446and the second portion448together define a shelf454that extends from a side wall of the first portion446, at the top end of the first portion446, to the side wall of the second portion448, at the bottom end of the second portion448. The second seat432also contacts the shelf454, and thus provides a snug fit of the second seat432within the second portion448of housing407at the shelf454.

A first seal member460is disposed in a groove462along the bottom surface of the lower portion428, which contacts the floor444of the housing407, to provide a first seal between the valve cartridge404and the inner wall401. A second seal member464is provided in a groove467around the periphery of the second seat432, where the second seat432contacts the side wall of the second portion

The second valve408has a rear stem436oriented toward the top plate434. The top plate434has an alignment bore438that extends from an inner surface of the top plate434toward the plug portion418of the second valve408. The rear stem436is inserted into the alignment bore438of the top plate434, and travels within the alignment bore438to maintain alignment of the first and second valves406and408. In this case, the second valve408can travel until the plug portion418of the second valve408contacts an end440of the alignment bore438. At that time, the rear stem436protrudes above the top plate434into the gap435. Length of the alignment bore438is selected to provide sufficient travel for the second valve408based on flow characteristics needed for the valve cartridge. Thickness of the top plate434can be varied to optimize structural strength and cost. The top plate434is connected to the second seat432by a plurality of posts442that provide structural strength for the upper portion426while allowing fluid flow through the upper portion426into the outlet manifold110.