Valve trim assembly and method

Abstract

The invention relates to a valve trim assembly for a control valve. A bushing assembly includes a first bushing having a helical hole pattern and configured to be coupled to an outer surface of a sleeve assembly, a second bushing having a helical hole pattern and configured to be coupled to a wall of the sleeve assembly, and a third bushing having a helical hole pattern and configured to be coupled to the spool movable between a closed position and an open position. The valve trim assembly further includes a first pressure recovery region disposed between the first bushing and the second bushing and a second pressure recovery region configured to be disposed between the sleeve assembly and an outer surface of the spool when the spool is in the open position.

Description

Technical Field

[0001] The present disclosure relates to valve trim assemblies for control valves, and in particular, to an anti-cavitation valve trim assembly for a control valve having a bushing with a spiral hole pattern. Background Art

[0002] Typically, for example, a three-stage valve trim assembly is used to reduce cavitation and protect the valve seat of a control valve. However, due to design limitations, many known three-stage valve trim designs include bushings with a horizontal hole pattern, resulting in dead zones between the horizontal rows in the bushing and, consequently, a stepped flow (Cv) curve for the valve sleeve assembly. This is generally unacceptable because it, at the very least, results in inaccurate control of the control valve.

[0003] Figures 1 to 4 An exemplary conventional three-stage valve trim assembly 10 is depicted in FIG. Figure 1 As shown, the valve trim assembly 10 includes a first-stage bushing 12 disposed on a sleeve assembly 14, a second-stage bushing 16 installed in the sleeve assembly 14, and a third-stage bushing 18 disposed in the wall 20 of the sleeve assembly 14. Because both the first-stage bushing 12 and the second-stage bushing 16 are installed using a shrink assembly method, the first-stage bushing 12 and the second-stage bushing 16 must be thin for ease of manufacturing. There must also be a large enough space for pressure recovery between each two adjacent stages. Each of the first-stage bushing 12, the second-stage bushing 16, and the third-stage bushing 18 includes a hole pattern design. Although the third-stage bushing 18 in the wall 20 of the sleeve assembly 14 has a deep enough hole 22 to provide pressure recovery space due to the thicker wall 20 of the sleeve assembly 14, the second-stage bushing 16 is much thinner than the third-stage bushing 18. As a result, the hole 24 in the second-stage bushing 16 cannot provide sufficient pressure recovery space. The groove 26 is used for pressure recovery in the valve trim assembly 10, as shown in FIG. Figure 2 However, the grooves 26 must be horizontal and isolated from one another, which dictates that the hole pattern design on the second stage liner 16 and the hole pattern design on each of the first stage liner 12 and the third stage liner must also be horizontal, as shown in FIG. Figures 2 to 4 As shown. At least because each row is horizontal in the first-stage bushing 12, the second-stage bushing 14, and the third-stage bushing 18, there will be a dead zone between each row. Therefore, for this conventional valve trim assembly 10, the flow (Cv) curve of the sleeve assembly is stepped or stepped, as shown in FIG. Figure 5 As described in . Summary of the Invention

[0004] According to a first example aspect, a valve trim assembly for a control valve includes a first liner having a helical pattern of holes and configured to be coupled to an outer surface of a sleeve assembly, and a second liner having a helical pattern of holes and configured to be coupled to a wall of the sleeve assembly. The valve trim assembly also includes a third liner having a helical pattern of holes and configured to be coupled to a spool movable between a closed position and an open position. Additionally, the valve trim assembly includes a first pressure recovery region disposed between the first liner and the second liner, and a second pressure recovery region configured to be disposed between the sleeve assembly and an outer surface of the spool when the spool is in the open position.

[0005] According to another example aspect, a control valve includes a valve body having an inlet and an outlet, a sleeve assembly disposed within the valve body, and a valve seat coupled to the sleeve assembly. The control valve also includes a spool disposed within the sleeve assembly and movable between a closed position and an open position, and a valve trim assembly. The valve trim assembly includes a first liner having a helical pattern of holes and coupled to the sleeve assembly, a second liner having a helical pattern of holes and coupled to a wall of the sleeve assembly, and a third liner having a helical pattern of holes and coupled to the spool. The valve trim assembly also includes a first pressure recovery region disposed between the first liner and the second liner, and a second pressure recovery region disposed between the sleeve assembly and an outer surface of the spool when the spool is in the open position.

[0006] According to another example aspect, a method of reducing cavitation of a valve seat of a control valve using a valve trim assembly is disclosed. The method includes coupling a first liner of the valve trim assembly to an outer surface of a sleeve assembly, the first liner having a helical pattern of holes, and coupling a second liner of the valve trim assembly to a wall of the sleeve assembly, the second liner having a helical pattern of holes. The method also includes coupling a third liner of the valve trim assembly to a spool movable between a closed position and an open position, the third liner having a helical pattern of holes. The method further includes forming a first pressure recovery region between the first liner and the second liner, and forming a second pressure recovery region between the wall of the sleeve assembly and an outer surface of the spool when the spool is in the open position.

[0007] Further to any of the foregoing example aspects, the valve trim assembly, the control valve, and / or the method of reducing cavitation of a control valve using a valve trim assembly can further include any one or more of the following preferred forms.

[0008] In some preferred forms, the first liner can be associated with a first stage of the valve trim assembly, the second liner can be associated with a second stage of the valve trim assembly, and the third liner can be associated with a third stage of the valve trim assembly.

[0009] In other preferred forms, the second bushing can be configured to be disposed proximate the first bushing such that the first bushing surrounds the second bushing. Additionally, the third bushing can be configured to be disposed separately from the first and second bushings and the sleeve assembly and around the spool.

[0010] In another preferred form, the first pressure recovery region can be disposed between the first and second bushings within a wall of the sleeve assembly, and the second pressure recovery region can be disposed between the second and third bushings when the spool is in the open position.

[0011] In other preferred forms, the sleeve assembly can include a wall having an inner surface and an outer surface, and the spool can include a body having an outer surface, wherein the first pressure recovery region can be disposed between the inner surface and the outer surface of the wall of the sleeve assembly, and the second pressure recovery region can be disposed between the inner surface of the wall of the sleeve assembly and the outer surface of the body of the spool when the spool is in the open position.

[0012] In other forms, the third bushing can be disposed downstream of the seat line of the valve seat when the spool is in the closed position, thereby reducing the risk of cavitation near the seat line.

[0013] In other forms, the dead band of the sleeve assembly can be equal to the dead band of the spool, and the dead band of the sleeve assembly can be disposed at an area from the first bore at the end of the second bushing to the seat line of the spool and the dead band of the spool can be disposed at an area from the centerline of the first bore at the end of the third bushing to the seating surface of the valve seat.

[0014] In other forms, forming the first pressure recovery region between the first and second bushings can include forming the first pressure recovery region disposed between the first and second bushings within a wall of the sleeve assembly, and forming the second pressure recovery region between the wall of the sleeve assembly and the outer surface of the spool can include forming the second pressure recovery region between the second and third bushings when the spool is in the open position.

[0015] In yet other preferred forms, forming the first pressure recovery region between the first and second bushings can include forming the first pressure recovery region between an inner surface of the wall of the sleeve assembly and an outer surface of the wall of the sleeve assembly, and forming the second pressure recovery region between the wall of the sleeve assembly and the outer surface of the spool when the spool is in the open position can include forming the second pressure recovery region between the inner surface of the wall of the sleeve assembly and the outer surface of the body of the spool when the spool is in the open position.

[0016] In yet another preferred form, coupling a third bushing having a spiral hole pattern to a valve core capable of moving between a closed position and an open position may include positioning the third bushing downstream of a seating line of the valve core and the valve seat when the valve core is in the closed position, thereby reducing the risk of cavitation near the seating line, wherein the dead zone of the sleeve assembly is equal to the dead zone of the valve core.

[0017] Any one or more of these aspects may be considered individually and / or combined with each other in any functionally appropriate manner. In addition, any one or more of these aspects may further include any one or more of the optional exemplary arrangements and / or features described below and / or be implemented in any one or more of the optional exemplary arrangements and / or features described below. These and other aspects, arrangements, features, and / or technical effects will become apparent upon detailed inspection of the accompanying drawings and the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The novel features of the present disclosure are set forth with particularity in the appended claims. The present disclosure may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements throughout the several views, and in which:

[0019] Figure 1 is a cross-sectional view of a conventional three-stage trim assembly for a control valve;

[0020] Figure 2 corresponds to Figure 1 a view of a bushing of the first stage of the valve trim assembly;

[0021] Figure 3A yes Figure 1 A side view of another bushing of the valve trim assembly;

[0022] Figure 3B yes Figure 3A Another view of the bushing;

[0023] Figure 4 yes Figure 1 a view of yet another bushing of the valve trim assembly;

[0024] Figure 5 Is a description of Figure 1 A graph showing the step flow (Cv) curve of a control valve with a trim assembly;

[0025] Figure 6 is a cross-sectional view of a valve trim assembly according to the present disclosure, wherein a control valve and a valve plug of the control valve are in a closed position;

[0026] Figure 7 yes Figure 6 A close-up view of the trim assembly and portion of the control valve;

[0027] Figure 8 is a cross-sectional view of a valve trim assembly according to the present disclosure, with a control valve, a spool of the control valve in an open position;

[0028] Figure 9 is Figure 8 a close-up view of a portion of the valve trim assembly and control valve of

[0029] Figure 10 is Figure 6 a cross-sectional view of a sleeve assembly of

[0030] Figure 11 is a first bushing of a valve trim assembly of the present disclosure;

[0031] Figure 12 is a second bushing of a valve trim assembly of the present disclosure;

[0032] Figure 13 is a third bushing of a valve trim assembly of the present disclosure; and

[0033] Figure 14 is a graph depicting a non-step flow (Cv) curve for a sleeve assembly of a valve trim assembly of Figures 6 to 13 DETAILED DESCRIPTION

[0034] A valve trim assembly for a control valve is depicted. The valve trim assembly is a three-stage valve trim assembly that includes a first bushing having a helical bore pattern and configured to couple to an outer surface of a sleeve assembly of a control valve. The first bushing is associated with a first stage of the valve trim assembly. The valve trim assembly also includes a second bushing that also has a helical bore pattern and is configured to couple to a wall of the sleeve assembly. The second bushing is associated with a second stage of the valve trim assembly. The valve trim assembly further includes a third bushing having a helical bore pattern and configured to couple to a spool of the control valve, the third bushing being separate from the first bushing and the second bushing, and the spool being movable between a closed position and an open position. A deadband on the sleeve assembly is equal to a deadband on the spool. Additionally, the valve trim assembly includes a first pressure recovery region disposed between the first bushing and the second bushing, and a second pressure recovery region configured to be disposed between the sleeve assembly and an outer surface of the spool when the spool is in the open position. As so configured, a flow curve of the sleeve assembly is non-step when the spool is in the open position and fluid flows through one or more of the first bushing, the second bushing, and the third bushing.

[0035] Reference is now made to Figure 6 ​position and an open position as depicted in Figure 6 and Figure 7 and as depicted in Figure 8 and Figure 9 are described in more detail below.

[0036] The control valve 100 also includes a valve trim assembly 124 of the present disclosure. The valve trim assembly 124 includes a first liner 126 having a helical bore pattern and coupled to the sleeve assembly 118 and a second liner 128 having a helical bore pattern and coupled to a wall of the sleeve assembly 118. In this example, the second liner 128 is configured to be disposed immediately adjacent to the first liner 126 such that the first liner 126 surrounds the second liner 128. The valve trim assembly 118 also includes a third liner 130 having a helical bore pattern and coupled to the spool 122, the third liner 130 being separate from the first liner 126 and the second liner 128 coupled to the sleeve assembly 118. Because the second liner 128 is coupled to the wall of the sleeve assembly 118, the deep bore design of the second liner 128 is viable, for example, for pressure recovery, and the bore pattern of each of the first liner 126, the second liner 128, and the third liner 130 can be helical. With this configuration, the flow (Cv) curve of the sleeve assembly 118 is non-staged when the spool 122 is in the open position and fluid flows through one or more of the first liner 126, the second liner 128, and the third liner 130.

[0037] Referring now to Figure 7 , a close-up view of the valve trim assembly 124 of Figure 6 is depicted. In the closed position of the spool 122, a seating surface 132 of the spool 122 contacts the valve seat 120, forming a seating line 133. With this configuration, the third liner 130 is disposed downstream of the seating line 133 of the valve seat 120 and the spool 122 when the spool 122 is in the closed position of Figure 6 and Figure 7 , thereby reducing the risk of cavitation near the seating line 133.

[0038] As Figure 7Further depicted in the middle, the sleeve assembly 118 includes a wall 136 having an inner surface 137 and an outer surface 138. The spool 122 includes a body 122a having an outer surface 140. The first bushing 126 is coupled to the outer surface 138 of the wall 136 of the sleeve assembly 118, and the second bushing 128 is coupled to the inner surface 137 of the wall 136 of the sleeve assembly 118. The third bushing 130 is coupled to the outer surface 140 of the body 122a of the spool 122.

[0039] In the three-stage valve trim assembly 124, it is appreciated that the first bushing 126 is associated with the first stage of the valve trim assembly 124, the second bushing 128 is associated with the second stage of the valve trim assembly 124, and the third bushing 130 is associated with the third stage of the valve trim assembly 124. As Figure 7 Further depicted in the middle, the deadband 142 of the sleeve assembly 118 is equal to the deadband 144 of the spool 122. More specifically, the deadband 142 of the sleeve assembly 118 is associated with the first bushing 126 and the second bushing 128 of the first and second stages of the valve trim assembly 124 coupled to the sleeve assembly 118. The deadband 142 of the sleeve assembly 118 is disposed at an area where a centerline of the first bore 129 at the first end 128a Figure 12 ) of the second bushing 128 extends to the seating line 133 of the spool 122 and the valve seat 120, as Figure 7 depicted. The deadband 144 of the spool 122 is associated with the third stage of the third bushing 130 of the valve trim assembly 124. The deadband 144 of the spool 122 is disposed at an area where a centerline of the first bore 131 Figure 13 ) at the second end 130b of the third bushing 130 extends to the other seating surface 132a of the valve seat 120.

[0040] Reference is now made to Figure 8 and 9 depicting a cross-sectional view of the valve trim assembly 124 with the spool 122 of the control valve 100 in an open position. In the open position, the seating surface 132 of the spool 122 is moved away from contact with the valve seat 120. As a result, the third bushing 130 coupled to the spool 122 is now disposed adjacent to the first bushing 126 and the second bushing 128, and fluid is able to flow through the inlet 114 of the control valve 100. After flowing through the inlet 114, the fluid then flows through the first bushing 126 associated with the first stage and into the first pressure recovery area 146 formed by the plurality of passages 147 in the wall 136 of the sleeve assembly 118. As Figure 9As shown, the first pressure recovery region 146 is disposed between the first bushing 126 and the second bushing 128 and the inner surface 137 and the outer surface 138 of the wall 136 of the sleeve assembly 118. Then, when the spool 122 is in the open position, fluid flows through the second bushing 128 associated with the second stage and into the second pressure recovery region 148 disposed between the inner surface 137 of the wall 136 of the sleeve assembly 118 and the outer surface 140 of the spool 122. In other words, the first pressure recovery region 146 is disposed between the first bushing 126 and the second bushing 128 and the second pressure recovery region 148 is disposed in the cavity 150 between the second bushing 128 and the third bushing 130.

[0041] Referring now to Figure 10 , a cross-sectional view of the sleeve assembly 118 having a portion of the valve trim assembly 124 of the present disclosure coupled thereto is depicted. Specifically, the first bushing 126 and the second bushing 128 are coupled to the sleeve assembly 118. The first bushing 126 is coupled to the outer surface 138 of the wall 136 of the sleeve assembly 118. The second bushing 128 is coupled to the wall 136 of the sleeve assembly 118 and is disposed between the inner surface 137 and the outer surface 138 of the wall 136 of the sleeve assembly 118.

[0042] Referring now to Figures 11 to 13 , each of the first bushing 126, the second bushing 128, and the third bushing 130 of the valve trim assembly 124 of the present disclosure are depicted. Figure 11 The first bushing 126 includes a first end 126a, a second end 126b, and a cylindrical body 156 having a helical pattern of holes 158 disposed thereon. Also, Figure 12 The second bushing 128 includes a first end 128a, a second end 128b, and a cylindrical body 160 having a helical pattern of holes 162 disposed thereon. The helical pattern of holes 162 includes a first hole 129 disposed near the first end 128a of the second bushing 128. As described above, the first hole 129 is used to determine the area of the dead band of the sleeve assembly 118. Figure 13The third sleeve 130 includes a first end 130a, a second end 130b, and a cylindrical body 164 having a helical pattern of holes 166 disposed thereon. The helical pattern of holes 166 includes a first hole 131 disposed near the second end 130b of the third sleeve 130, and the first hole 131 is used to determine the area of the dead band of the spool 122, as also described above. The helical pattern of holes 158 of the first sleeve 126, the helical pattern of holes 162 of the second sleeve 128, and the helical pattern of holes 166 of the third sleeve 130 each have a plurality of columns of holes disposed, for example, along a vertical axis of the first sleeve 126, the second sleeve 128, and the third sleeve 130. The columns are immediately adjacent to one another. In this example, in each of the helical patterns of holes 158, 162, and 166, the holes in each column are staggered from the holes in the immediately adjacent columns, and also include holes disposed, for example, along a circumference of the first sleeve 126, the second sleeve 128, and the third sleeve 130. For example, the holes along the circumference can or can not be disposed along the same horizontal and / or circumferential plane. It will be understood that the helical patterns of holes 158, 162, and 166 can include any helical pattern of holes known and understood by those skilled in the art to, for example, achieve the same functionality described herein with respect to the first sleeve 126, the second sleeve 128, and the third sleeve 130, and still fall within the scope of the present disclosure.

[0043] By separating the third sleeve 130 associated with the third stage of the valve trim assembly 124 from the sleeve assembly 118 in which only the first stage of the first sleeve 126 and the second stage of the second sleeve 128 are disposed, the pattern of holes in the first sleeve 126, the second sleeve 128, and the third sleeve 130 can be a helical pattern of holes. So configured, the flow (Cv) curve is non-staged, or achieves a non-staged flow curve, for example, as shown in Figure 14 In other words, due to the valve trim assembly 124 of the present disclosure, the flow (Cv) curve is substantially smooth or forms a substantially smooth line, as depicted in Figure 14 More particularly, Figure 14 The graph in Figure 14the flow of sleeve assembly 118 initially represented as zero in the graph. However, as the spool 122 continues to move from the closed position to the open position and more fluid is able to flow through the holes of the helical hole pattern of each of the first bushing, the second bushing, and the third bushing, the flow (Cv) of the sleeve assembly 118 continues to increase without dead zones in the helical hole pattern of each of the first bushing, the second bushing, and the third bushing. This results in a smooth and / or non-staged flow curve of the sleeve assembly 118, as shown in Figure 14

[0044] It should be appreciated that the trim assembly 124 reduces cavitation of the valve seat 120 of the control valve 100, for example, by at least one or more of the following methods. Specifically, the methods of using the trim assembly 124 to reduce cavitation of the valve seat 120 of the control valve 100 include coupling the first bushing 126 of the trim assembly 124 to the outer surface 138 of the sleeve assembly 118, the first bushing 126 having a helical hole pattern. The methods also include coupling the second bushing 128 of the trim assembly 124 to the wall 136 of the sleeve assembly 118, the second bushing 128 having a helical hole pattern. The methods further include coupling the third bushing 130 of the trim assembly 124 to the spool 122 that is movable between the closed position and the open position, the third bushing 130 having a helical hole pattern. So configured, the dead zone 142 of the sleeve assembly 118 is equal to the dead zone 144 of the spool 120. The methods also include forming a first pressure recovery area 146 between the first bushing 126 and the second bushing 128, and forming a second pressure recovery area 148 between the wall 136 of the sleeve assembly 118 and the outer surface 138 of the spool 122 when the spool 122 is in the open position. When the spool 122 is in the open position, a non-staged flow curve of the sleeve assembly 118 is created as fluid flows through one or more of the first bushing 126, the second bushing 128, and the third bushing 130.

[0045] ​In one example, forming the first pressure recovery region 146 between the first bushing 126 and the second bushing 128 can further include forming the first pressure recovery region 146 disposed between the inner surface 137 of the wall 136 of the sleeve assembly 118 and the outer surface 138 of the wall 136 of the sleeve assembly 118. Additionally, forming the second pressure recovery region 148 disposed between the second bushing 128 and the third bushing 130 when the spool 122 is in the open position can include forming the second pressure recovery region 148 disposed between the inner surface 137 of the wall 136 of the sleeve assembly 118 and the outer surface 140 of the body of the spool 122 when the spool 122 is in the open position. In another example, coupling the third bushing 130 having a helical bore pattern to the spool 122 movable between the closed position and the open position includes, for example, disposing the third bushing 130 downstream of the seat 120 and the seating line 133 of the spool 122 when the spool 122 is in the closed position, thereby reducing the risk of cavitation near the seating line 133.

[0046] In view of the foregoing, it will be appreciated that the foregoing valve trim assembly 124 and related methods include at least the following advantages. Having the valve trim assembly 124 with at least the third bushing 130 associated with the third stage coupled to the spool 122 (and not in the sleeve assembly as in conventional designs) enables each of the first bushing 126, the second bushing 128, and the third bushing 120 to have a helical bore pattern, and the flow Cv curve of the sleeve assembly 118 is non-staged and / or smooth. The valve trim assembly 124 of the present disclosure includes a sufficiently large area for pressure recovery between each adjacent stage (e.g., the first and second stages and the second and third stages described above). Having a non-staged flow Cv curve of the sleeve assembly 118 provides more precise control of the control valve 100 and reduces the risk of cavitation near the seating line 133 of the seat 120 and the spool 122.

[0047] The accompanying drawings and descriptions provided herein depict and describe preferred embodiments of control valves, valve trim assemblies, and related methods for purposes of illustration only. Those skilled in the art will readily recognize from the discussion that changes and modifications of the embodiments illustrated can be variously effected. Thus, while specific embodiments and applications have been shown and described, it is envisioned that those skilled in the art will readily apply these teachings to other types of structures and applications without departing from the spirit and scope of the disclosure defined by the appended claims. Various modifications, changes, and variations apparent to those skilled in the art can be made in the arrangement, operation, and details of the methods and assemblies disclosed herein without departing from the spirit and scope of the claimed disclosure.

Claims

1. A valve trim assembly for a control valve, the valve trim assembly comprising: a first liner having a helical bore pattern and configured to be coupled to an outer surface of a sleeve assembly; a second liner having a helical bore pattern and configured to be coupled to a wall of the sleeve assembly; a third liner having a helical bore pattern and configured to be coupled to a spool movable between a closed position and an open position; a first pressure recovery area disposed between the first liner and the second liner; and a second pressure recovery area configured to be disposed between the sleeve assembly and an outer surface of the spool when the spool is in the open position.

2. The valve trim assembly of claim 1, the first liner associated with a first stage of the valve trim assembly, the second liner associated with a second stage of the valve trim assembly, and the third liner associated with a third stage of the valve trim assembly.

3. The valve trim assembly of claim 1, the second liner configured to be disposed immediately adjacent to the first liner such that the first liner surrounds the second liner, and the third liner configured to be disposed separately from the first liner and the second liner and the sleeve assembly and around the spool.

4. The valve trim assembly of claim 1, the first pressure recovery area disposed between the first liner and the second liner within the wall of the sleeve assembly, and the second pressure recovery area configured to be disposed between the second liner and the third liner when the spool is in the open position.

5. The valve trim assembly of claim 1, the wall of the sleeve assembly having an inner surface and an outer surface, and the spool having a body with an outer surface, and the first pressure recovery area disposed between the inner surface and the outer surface of the wall of the sleeve assembly, and the second pressure recovery area configured to be disposed between the inner surface of the wall of the sleeve assembly and the outer surface of the body of the spool when the spool is in the open position. the third liner disposed downstream of a seating line of the spool and the valve seat when the spool is in the closed position, thereby reducing a risk of cavitation near the seating line.

6. The valve trim assembly of claim 1, wherein, a dead band of the sleeve assembly equal to a dead band of the spool, and the dead band of the sleeve assembly disposed at an area extending from a first bore at an end of the second liner to the seating line of the spool and the valve seat, and the dead band of the spool disposed at an area extending from a centerline of a first bore at an end of the third liner to a seating surface of the valve seat.

7. The valve trim assembly of claim 1, wherein, 8. A control valve, the control valve comprising: a valve body having an inlet and an outlet; a sleeve assembly disposed within the valve body; a valve seat coupled to the sleeve assembly; a spool disposed within the sleeve assembly, the spool movable between a closed position and an open position; and a valve trim assembly according to any one of claims 1 to 7. ​ A valve trim assembly comprising: a first liner having a helical bore pattern and coupled to the sleeve assembly; a second liner having a helical bore pattern and coupled to a wall of the sleeve assembly; a third liner having a helical bore pattern and coupled to the spool; a first pressure recovery region disposed between the first liner and the second liner; and a second pressure recovery region disposed between the second liner and the third liner when the spool is in the open position.

9. The control valve of claim 8, wherein, The dead band of the sleeve assembly is equal to the dead band of the spool, and the dead band of the sleeve assembly is disposed at an area extending from a first bore at an end of the second liner to a seat line of the spool and the valve seat, and the dead band of the spool is disposed at an area extending from a centerline of a first bore at an end of the third liner to a seating surface of the valve seat.

10. The control valve of claim 8, wherein, The closed position is a position where a seating surface of the spool contacts the valve seat, and the open position is a position where the seating surface of the spool is removed from the valve seat.

11. The control valve of claim 8, wherein, The first liner is coupled to an outer surface of a wall of the sleeve assembly, the second liner is coupled to an inner surface of the wall of the sleeve assembly, and the third liner is coupled to an outer surface of the spool.

12. The control valve of claim 8, the first liner is associated with a first stage of the valve trim assembly, the second liner is associated with a second stage of the valve trim assembly, and the third liner is associated with a third stage of the valve trim assembly.

13. The control valve of claim 8, the second liner is disposed immediately adjacent to the first liner such that the first liner surrounds the second liner, and the third liner is disposed separate from the first liner and the second liner and the sleeve assembly and surrounds the spool.

14. The control valve of claim 8, wherein, The first pressure recovery region is disposed between the first liner and the second liner within the wall of the sleeve assembly, and the second pressure recovery region is disposed between the second liner and the third liner when the spool is in the open position.

15. The control valve of claim 8, wherein, The sleeve assembly has a wall with an inner surface and an outer surface, and the spool has a body with an outer surface, wherein the first pressure recovery region is disposed between the inner surface and the outer surface of the wall of the sleeve assembly, and the second pressure recovery region is disposed between the inner surface of the wall of the sleeve assembly and the outer surface of the body of the spool when the spool is in the open position.

16. The control valve of claim 8, wherein, The third liner is disposed downstream of a seat line of the spool and the valve seat when the spool is in the closed position, thereby reducing the risk of cavitation near the seat line.

17. A method of reducing cavitation of a valve seat of a control valve using a valve trim assembly, the method comprising: coupling a first liner of a valve trim assembly to an outer surface of a sleeve assembly, the first liner having a helical bore pattern; coupling a second bushing of the valve trim assembly to a wall of the sleeve assembly, the second bushing having a helical bore pattern; coupling a third bushing of the valve trim assembly to a valve plug movable between a closed position and an open position, the third bushing having a helical bore pattern; forming a first pressure recovery area between the first bushing and the second bushing; and forming a second pressure recovery area between the wall of the sleeve assembly and an outer surface of the valve plug when the valve plug is in the open position.

18. The method of claim 17, wherein, forming a first pressure recovery area disposed between the first bushing and the second bushing includes forming the first pressure recovery area disposed between the first bushing and the second bushing within the wall of the sleeve assembly, and forming a second pressure recovery area between the wall of the sleeve assembly and an outer surface of the valve plug when the valve plug is in the open position includes forming the second pressure recovery area between the second bushing and the third bushing.

19. The method of claim 17, wherein, forming a first pressure recovery area between the first bushing and the second bushing includes forming the first pressure recovery area between an inner surface of the wall of the sleeve assembly and an outer surface of the wall of the sleeve assembly, and forming a second pressure recovery area between the wall of the sleeve assembly and an outer surface of the valve plug when the valve plug is in the open position includes forming the second pressure recovery area between an inner surface of the wall of the sleeve assembly and an outer surface of a body of the valve plug when the valve plug is in the open position.

20. The method of claim 17, wherein, coupling a third bushing having a helical bore pattern to a valve plug movable between a closed position and an open position includes disposing the third bushing downstream of a seating line of the valve plug and the valve seat when the valve plug is in the closed position, thereby reducing a risk of cavitation near the seating line, wherein a dead band of the sleeve assembly is equal to a dead band of the valve plug.

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