JPH052878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention provides energy loss and high resistance to fluid flow by discordant and separated fluid flow conditions, thereby reducing cavitation. A new and improved trim structure for a control valve that prevents

[Conventional technology and problems]

Cavitation that occurs in control valves has the disadvantage of causing removal of material from the internal valve surfaces. Cavitation occurs when the pressure at the control orifice falls below the vapor pressure that forms bubbles. When the pressure past the control orifice rises above the vapor pressure, the bubble collapses. Parts and components within the valve near the collapsing bubbles experience cavitation damage. Eliminating cavitation requires preventing the pressure at the control orifice from dropping below vapor pressure levels. This can be done by turning a single valve pressure drop into a dual pressure drop, reducing the amount of pressure recovery that occurs at any one stage.

Three basic techniques are used by valve designers to control or eliminate cavitation damage. The first technique involves hardening the inner surface of the bulb in areas where cavitation is likely to occur. The second technique is to design the trim flow-to-close. That is, the jets of fluid that are trying to form cavitation are made to converge with each other at an intermediate position of the flow,
This allows bubble collapse to occur away from the delicate internal surfaces and components of the valve. Although both of these techniques are intended to minimize and control the drawbacks of cavitation, they cannot eliminate cavitation. Naturally, these techniques are commonly used in the case of low pressure drops, i.e. when cavitation is not as severe as in other cases.

The third technique is a type of cavitation elimination. A downstream restriction is used to back up the control valve outlet pressure.
This technique requires the use of staging external to the control valve, resulting in an expensive and large valve.

U.S. Pat. No. 3,971,411 discloses a trim assembly that provides resistance to fluid flow by directing the fluid through passages that absorb some fluid energy in an axial direction. US Patent No.
No. 3,813,079 illustrates a radial fluid passageway defined by slots in one or more cylinders. U.S. Pat. No. 3,780,767 shows a dual obstruction assembly for providing resistance to flow and discloses a plurality of plates with cut-outs defining swirl chambers. Each of the structures disclosed in the above-mentioned patents includes a single technique for interfering with fluid flow. Each uses either radial or axial flow resistance and has the primary purpose of reducing noise. These devices do not split a single large valve pressure drop into multiple smaller pressure drop stages to avoid vapor pressure bubbles created in the fluid controlled by the valve.

[Means for solving problems]

That is, according to the present invention, a valve body having a fluid inlet and a fluid outlet, a valve seat ring positioned between the fluid inlet and the fluid outlet within the valve body, and a valve seat ring that is reciprocally movable within the valve body. a plurality of cage members positioned within the valve body, the plurality of gauge members having a plurality of apertures and a valve plug mounted on the valve body, the valve including a valve plug that engages the valve seat ring in a valve closing mode; a first cage member having a plurality of radially extending fins, a second cage member having a plurality of apertures and a plurality of radially extending fins, and a third cage member having a plurality of apertures. A valve is provided including a cage member, the plurality of cage members being positioned within the valve body to define an axial flow path between adjacent cage members. This new and improved fluid flow control valve includes a trim structure to prevent cavitation within the control valve.

The trim includes a plurality of concentric interference-fit cages removably positioned on the valve seat surrounding the valve plug. Concentric multiple cages are
They are slightly spaced apart from each other to define an axial gear rally between adjacent cages.

Appropriately located apertures and fins in the valve cage provide a high resistance flow path with special staging areas to prevent fluid pressure from dropping below fluid vapor pressure. The aperture, fin and gear rally areas are dimensioned as follows. That is,
The variable plug lift position allows the continuously varying flow path to properly distribute the pressure drop and prevent cavitation during intermediate as well as final stages of fluid flow.

The valve trim continuously increases the coupling fade area during the common gear rally when the valve plug is lifted. This provides a constant change in flow path configuration and pressure drop distribution compared to most other radially designed trim assemblies.

The combination of radial apertures and fins continuously mismatches and subsequently separates the fluid flow in both the radial and axial directions, providing additional high energy losses and further avoiding the risk of cavitation. . The location of the cage apertures and fins provides for more staging in the low lift position of the valve plug, and the highest pressure drop in the high lift position with less pressure drop, providing higher capacity and less staging. The low lift position is provided with both radial and axial flow passages, and the high lift position is provided with only radial passages.

The stage area defined by the apertures and fins of the multiple concentric cages provides a continuously decreasing pressure drop from the concentric cage inlet to the outlet to progressively increase the flow area. This ensures that the last stage in the outer cage has the lowest pressure drop. This is beneficial because the pressure drop in this last stage is at the optimal vapor pressure level for cavitation prevention.

〔Example〕

Referring first to FIG. 1, a control valve, designated generally by the reference numeral 10, is illustrated.
Valve 10 includes a body 12 having a fluid inlet 14 and a fluid outlet 16. The main body 12 has an inlet 1
4 and near the outlet 16, respectively, are mounted flanges 15, 17 to connect the valve 1 to the conduit of the fluid system.
0 can be connected. Valve body 1
Inside 2, a valve plug chamber 18 is provided centrally between the inlet 14 and the outlet 16.
The chamber 18 is an inlet side fluid passage 2 provided in the main body.
0 and port 22 communicate with inlet 14 . Fluid outlet 16 communicates with chamber 18 by fluid passageway 24 .

In use, the valve 10 functions on a pressure drop between 500 p.si and 3000 p.si which causes cavitation which causes damage to the inner surface of the valve body 12. The fluid flowing through valve 10 is
It is controlled by a valve plug 30 reciprocably mounted within the chamber 18. chamber 1
The upper end of 8 is the valve plug 3 into the chamber 18.
An opening or aperture 32 is included to allow insertion of a zero. The valve plug 30 has a stem 34
The valve 30 is reciprocated within the chamber 18 by an external valve controller (not shown) mechanically connected to the valve 30 by an external valve controller (not shown). Here stem 3
4 extends through the aperture 32 and is attached to the valve plug 30 by a pin 36. Pin 36 allows separation between stem 34 and valve plug 30, allowing valve plug 30 to be easily removed for replacement or repair.

The valve body 12 has a removable valve bonnet 38 with threaded studs or fasteners 40,4.
It is attached by 2. Surrounding the aperture 32 is a gasket 44 which is maintained in position by the bonnet 38.
A seal is formed between the bonnet 38 and the valve body 12. With the valve in the closed condition (FIG. 1), the valve plug 30 is attached to the valve seat ring 46 removably positioned in the aperture 22.
is closely engaged with.

To prevent cavitation within valve 10, a high resistance fluid passageway is provided by a valve cage assembly, indicated generally by the reference numeral 48. Valve cage assembly 48 includes a plurality of concentric cages in an interference fit. In the preferred embodiment shown, three cylindrical cages 50, 52, 54 are used, but other numbers may be used for design reasons. The cylindrical cages 50, 52, 54 include a plurality of apertures, fins, and gear rally areas that provide a continuously varying flow path due to the variable lift position of the plug 30 as desired to prevent cavitation. are spaced and dimensioned to distribute the pressure drop.

The cages 50, 52 each include flanges 56, 58 that define a space or gear rally area, such as an axial gear rally area 60 between the cages 50, 52 and an axial gear rally area 62 defined between the cages 52, 54. There is. The cage 50 further includes a plurality of ribs or fins 64 provided at the bottom.
Contains. Cage 52 also includes a plurality of fins or ribs 66 on the bottom. But Cage 54 has no fins.

The radial passage through the first cage 50 is defined by a plurality of apertures or openings 68 along the length of the cage 50 that correspond to the full range of lift positions of the valve plug 30. The second cage 52 includes radial openings or apertures 70 in its upper and lower portions and has an impermeable portion 72 between the upper and lower portions. Third cage 54 includes a water-impermeable lower portion 74 and an upper portion having a plurality of apertures 76 .

Cages 50, 52, 54 are removably positioned within valve body 12 and are radially retained by pins 78. Removal of pin 78 allows for rotation of intermediate or second cage 52 relative to first cage 50 and third cage 54. Rotating cage 52 causes aperture 70 to be misaligned with aperture 68 at the bottom of cage 50 (FIG. 3). When such a mismatch occurs, the fluid must change direction and flow through a tortuous channel in order to flow through the aperture 70. In the lower lift position (FIGS. 2 and 3) fluid flow is directed against the fins 64 in the axial gear rally region 62. Once the flow passes through an aperture 68 in the lower portion of the cage 50, it enters the gear rally region 60. Once the flow passes through the aperture 70 in the lower portion of the cage 52, it enters the gear rally region 62;
It flows upwardly through the fins 66 and then out through the apertures 76 and into the chamber 18 . This configuration has many stages that promote anti-cavitation. This is preferred because at low lift positions the pressure drop is at its highest value with the greatest potential for cavitation.

When the valve plug 30 is raised to the approximately half-open position (FIGS. 4 and 5), a number of apertures 68 are exposed and the flow through the lower part of the cages 50, 52 is twisted as previously described. Pass through the passage. In the intermediate portions of the cages 50, 52, the apertures 70, 68 are misaligned with the apertures 76 (FIG. 5) and the flow is substantially radial.

For relatively large valves, aperture 7
The flow path area determined by 0,76 may be substantially larger than the flow path area in the gear rally 60,
and gear rallies 60 in these large valves where there will be no flow through the lower part of the cage 52 and no pressure drop across it.
Fins 65 are provided to distribute the flow within the gear rally 60 and direct a portion of the flow within the gear rally 60 to an aperture 70 at the bottom of the cage 52, thereby more evenly distributing the total pressure drop over the length of the cage 52. .

When fully open, that is, in the position where the plug 30 is raised to the top (FIG. 6), the apertures 68, 70, 7
6 are all exposed but mismatched to allow a large volume tortuous radial flow, and less staging due to less pressure drop at this level. At these high lift positions, align and match the apertures 68, 70, 76,
and/or enlargement for larger capacity is optional. At the low lift position (FIGS. 2 and 3) there is a large pressure drop and many separation conditions for potential cavitation. Thus, in the high lift position only radial flow passages are required, whereas in the low lift position both radial and axial flow passages are provided.

In the low lift position, the gear rally region 52 has only axial flow paths. The axial flow within the gear rally 60 is such that the valve plug 30
Intermediate lift position above 4 (Fig. 4, 5)
It is added when it is lifted up to (Fig.). This configuration progressively increases the flow area to ensure that the last stage in the outer cage 54 has the lowest pressure drop. The lowest pressure drop here is beneficial as the pressure drop in this last stage is at the optimum vapor pressure level for anti-cavitation.

Since the gear rally regions 60, 62 are always exposed to flowing fluid, the valve plug 30
There is always a distribution of pressure drop along the outer diameter of the In contrast, conventional radial structures separate the flow into individual radial passages at different lift locations;
And there is no pressure drop staging on the lift position of the plug. Thus, a sufficient pressure drop crosses the tip of the valve plug, resulting in some cavitation damage to the tip of the plug.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the control valve according to the present invention, FIG. 2 is an enlarged partial cross-sectional view of the valve shown in FIG. 1 when the valve plug is slightly opened, and FIG. 4 is a view similar to FIG. 2 when the valve plug is in a higher raised position;
Figure 5 is a cross-sectional view taken along line 5-5 in Figure 4;
The figure is a view similar to FIG. 2 with the valve plug in its highest raised position, and FIG. 7 is a sectional view taken along line 7--7 of FIG. 6. 10... Valve, 12... Valve body, 14... Fluid inlet, 16... Fluid outlet, 30... Valve plug, 4
6... Valve seat ring, 50... First cage member, 52... Second cage member, 54... Third cage member, 64, 65, 66... Fin, 68, 7
0,76...Apatya.

Claims (1)

Claims: 1. A valve body 12 having a fluid inlet 14 and a fluid outlet 16, a valve seat ring 46 positioned between the fluid inlet and the fluid outlet within the valve body, and a valve seat ring 46 located within the valve body. a valve 10 including a valve plug 30 reciprocably mounted on the valve body and engaging the valve seat ring in a valve closing mode; The plurality of cage members include a plurality of apertures 68 and a plurality of radially extending fins 64, 65.
a first cage member 50 having a plurality of apertures 70, a second cage member 52 having a plurality of radially extending fins 66, and a third cage member 54 having a plurality of apertures 76. wherein the plurality of cage members are positioned within the valve body to define an axial flow path between adjacent cage members. 2. The device according to claim 1, wherein the first, second and third cage members are movably positioned within the internal chamber so as to be rotatable relative to each other. valve. 3. The valve according to claim 1 or 2, wherein the plurality of cage members are arranged concentrically around the valve plug. 4. The first cage includes the aperture over the length of the cage corresponding to the full range of lift positions of the valve plug, and the fins are located at a position less than the entire length of the first cage. The valve according to claim 1, 2, or 3, characterized in that: 5. A patent claim characterized in that the second cage includes a first region having an aperture and fins, a second region having an aperture, and an impermeable region between the first and second regions. range 1-4
The valve described in any of the paragraphs. 6. The valve according to any one of claims 1 to 5, wherein the third cage includes the aperture at a position less than the total length of the third cage. 7. A lower end of each of the cage members engages the valve seat ring, the aperture of the first cage member is along the entire length of the first cage member, and the first cage member has a lower and an upper portion. the fins of the first cage member are at the lower portion of the first cage member, the second cage member includes a lower portion, a middle portion and an upper portion, and the aperture of the second cage member is located at the lower portion of the first cage member; the lower part and the upper part of the second cage member, the middle part being impervious to water, the third cage member including an upper part and the lower part, and the aperture of the third cage member being in the third cage member. 7. A valve according to any one of claims 1 to 6, wherein the lower part of the third cage member is impermeable to water. 8 A first cylindrical valve cage is removably mounted on the valve seat surrounding the valve plug, and a second cylindrical valve cage is provided concentrically with the first valve cage. and a first axial gear rally 60 is removably mounted on the valve seat and defines a first axial gear rally 60 between the first and second valve cages, and the fins of the first valve cage are connected to the first axial gear rally. a third cylindrical valve cage extending therein and concentrically with the first and second valve cages and removably mounted on the valve seat; A second axial gear rally (62) is defined between the valve cages, the fins of the second valve cage extending into the second axial gear rally. The valve according to any of Item 7. 9. that the apertures of the first valve cage are in a mismatched position with the apertures of the second valve cage, and that the apertures of the second valve cage are in a position consistent with the apertures of the third valve cage; Characteristic claim 1
- The valve according to any of item 8. 10. A valve according to any one of claims 1 to 9, characterized in that there is an additional fin 65 on the top of the first valve cage.