JP2001159475A - Low-noise butterfly valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cavitation generated in a valve contraction part, resulting in noises to be suppressed in the case of a liquid fluid, to reduce the variation of a Cv value per movement amount of a valve opening for improved controllability, to provide applicability to a fluid containing slurry or foreign matters, to form a structure eliminating unreasonable partial stresses such as high flow velocity energy, foreign matter collision or the like and allowing the use at a high flow velocity, to easily design a sealing structure in existing technology allowing the use at a high temperature, and to decrease manufactur ing cost to a minimum. SOLUTION: In an eccentric butterfly valve, which has a seal face formed between the peripheral face of a valve element 33 and the inner face of a body 31 not to pass through the center of a valve rod during full closing, the inner diameter of the body 31 right after a valve seat 32 is an inner diameter enlarged portion 31A, having an enlarged sectional shape symmetric with the center of a flow passage and the center of a valve stem 34, is located at the inner diameter enlarged portion 31A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a butterfly valve as one of industrial valves, and more particularly to a butterfly valve for controlling a flow rate and a pressure of a liquid (including a high-temperature liquid). The present invention relates to a butterfly valve for suppressing noise caused by cavitation, which is likely to occur at different degrees, and for improving controllability.

[0002]

2. Description of the Related Art Generally, a flow rate becomes high and a pressure becomes low in a throttled portion (a contraction portion) of a butterfly valve. Due to this pressure drop, the volume of microbubbles (bubble nuclei) contained in the liquid rapidly increases, and cavitation bubbles are generated. However, when the flow speed becomes low after passing through the contraction part, the pressure recovers. And the cavitation bubbles described above collapse.

At this time, the cavitation bubbles grow from the bubble nuclei (they become large bubbles and become small again).
At this time, noise is generated because the surrounding pressure fluctuates due to the contraction movement of the bubble. Further, an impact pressure is generated at the moment when the bubble is crushed, and a so-called cavitation phenomenon, which causes damage such as an erosion phenomenon on the inner surface of the valve body and the piping downstream of the valve seat with noise and vibration, occurs.

[0004] In particular, air bubbles that have collapsed near the inner surface of the main body or the pipe or air bubbles that have collided with the inner surface cause a large damage.

[0005] The likelihood of cavitation is generally evaluated by a pressure recovery coefficient (FL value) and a cavitation initiation coefficient (Kc value). (FL value,
Cavitation is less likely to occur as the Kc value increases.) However, _{F L} = pressure recovery coefficient (dimensionless) _{P 1} = valve inlet static pressure _{^{(kgf / cm 2 a) P}} 2 = valve outlet static pressure _{^{(kgf / cm 2 a) P}} vc = valve constriction static pressure (kgf / cm ² a)

[0006] Where K _c : cavitation initiation coefficient (dimensionless) P _v : saturated vapor pressure of liquid

[0007] Further, since the conventional butterfly valve can be compactly installed in a pipe, it is widely used for controlling the flow rate of a fluid flowing down a pipe. However, compared to a globe valve, a normal butterfly valve has a lower pressure recovery coefficient (FL value) and a lower cavitation initiation coefficient (Kc value), so cavitation occurs due to fluid conditions, which damages piping and generates abnormal noise. There was a problem to do.

A butterfly valve has a capacity coefficient (Cv value).
When used as a control valve,
When a valve having the same nominal diameter as the pipe is used, there is a problem in that the Cv value change amount per movement amount from fully closed to fully open is large and controllability is poor. In many cases, a valve having a smaller nominal diameter than the nominal diameter of the pipe is reduced ( Pipes used for pipe systems having different diameters).

On the other hand, the butterfly valve used for control is
The purpose is to adjust the flow rate and pressure by reducing the opening of the valve, and for that purpose, it is necessary to endure the use of cavitation with noise for that purpose.

FIG. 6 (see Japanese Patent Application Laid-Open No. 57-157866) and FIG. 7 (see Japanese Patent Application Laid-Open No. 4-337167) show a conventional example proposed in the past as an invention for suppressing the generation of noise and cavitation. Shown in

In FIG. 6, reference numeral 1 denotes a fully closed valve body which is supported by a valve rod 3 orthogonal to the center of a body (valve body) 2. It has a valve plate (disk) 1a having a V-shaped cross section perpendicular to the valve stem 3, and a sealing surface between the inner surface 2a of the main body 2 and the peripheral surface of the valve plate (dotted line 1b in the figure).
Indicated by ) Forms the valve element of the central butterfly valve passing through the valve stem hole, and the central axis 1c of the sealing surface 1b and the vertical axis 2b of the main body inner surface 2a passing through the valve stem hole are 15 degrees or more. It is inclined at an angle of 20 degrees.

The oblong valve plate 1a which is in close contact with the inner surface (bore) 2a of the main body has two substantially semi-circular wall portions formed so as to be angularly displaced in a U-shape as described above. During use, the inflow side comb-like projection 4 protruding toward the inflow direction of the fluid (indicated by the thick arrow f) over the semicircle of the valve plate 1a, similarly to the other semicircle. Around the circumference, an outflow side comb tooth projection 5 protruding toward the fluid outflow direction on the opposite side to the comb tooth projection 4 with respect to the valve plate 1a is provided integrally. The comb-shaped protrusions 4 and 5 are formed so as to be substantially parallel to the inner surface 2a of the main body 2 when fully closed, and the ends of these comb-shaped protrusions are in a plane perpendicular to the inner surface 2a of the main body 2. These comb-shaped protrusions are formed to be shorter toward the center boss direction.

During valve operation, when the valve element 1 rotates clockwise as indicated by an arrow from the fully closed state shown in FIG. 6A, the flow rate changes in accordance with the degree of opening of the valve element 1 and flow control is performed. It has become. At this time, the inner surface 2a of the main body 2 and the valve stem 3
A nozzle flow portion (nozzle side) which is an opening formed by the peripheral portion of the valve element 1 located further downstream than the main body 2
The fluid passing through the orifice flow portion (orifice side), which is an opening formed by the inner surface 2a of the valve member and the peripheral portion of the valve element 1 located on the upstream side of the valve rod 3, is provided by a plurality of fluids provided in the portion. (A) formed between each of the interdigital protrusions 4 and 5 of FIG.
The fluid is changed into a fine jet flow from a trapezoidal (trapezoidal) passage 6 for guiding the fluid shown in FIG. 2B, which is a sectional view taken along line 2b of FIG. 2B, and the cavitation generated downstream of the valve element is dispersed and the cavitation is reduced. It is suppressing growth. 6B, reference numeral 6a denotes an inclined inlet, 7 denotes a valve stem hole, and 8 denotes a boss.

In FIG. 7, a valve shaft 13 is fitted from both sides of the valve body 12 and rotatably supported. When the valve body 12 rotates from the closed state to the open direction, the half-peripheral side 12A which faces toward the upstream side. Of approximately the same thickness is provided on the surface near the outer peripheral edge on the downstream side of the shaft 1 over the entire half circumference connecting both bearings 16 of the valve shaft 13.
4 is a butterfly valve having a cavitation suppressing function in which a plurality of through-holes 15 are provided on the protruding ridges 14 so as to be directed toward the surface center 12 </ b> C of the valve element 12 and converge in a reverse radial manner.

FIG. 8 is different from the present invention in purpose.
A conventional example in which a part of the valve structure is similar (Japanese Patent Publication No. 52-33)
No. 330), (a) is a longitudinal sectional view, and (b) is a sectional view taken along line II-II in FIG. (A). In this embodiment, a valve body is constituted by a casing body 21 and a casing flange 22, and the valve body (disc) 23 is supported by a valve stem (sideward trunnion) 24 attached to a position shifted from the valve body (disc) 23. An elastic seating ring 25 is mounted on the valve seat of the butterfly valve so as to be embedded in the inner wall recess 26, and recesses 2a and 2b of the casing body 21 on the downstream side of the valve seat are provided. . The recesses 2a, 2b
As shown in FIG. 6B, the offset trunnion 24 is formed so that the depth is maximum at an intermediate position between the bearings on both sides of the trunnion 24 and the recess is eliminated at the bearings on both sides. This is arranged so that the cross-sectional area of the flow passage is generated at almost the same ratio when the valve element (disk) 23 rotates, whereby the fluid torque applied to the disk 23 is reduced. Is intended to be reduced as compared to the value of the torque generated when the rod is placed perpendicular to the cylindrical bore during the opening movement.

[0016]

In each of the arrangements shown in FIGS. 6 and 7, a projection or a groove for securing a flow path, a hole for separating the flow path, an additional material, etc. are provided on the main body or the valve body side. ,
The flow is divided to reduce the speed difference between the high-speed contraction section and the low-speed flow section, suppress cavitation, reduce the Cv value, and improve controllability. These have the effect of preventing noise and improving controllability, but all have the following common problems.

(I) Since the flow path is finely divided, it cannot be used for a slurry or a fluid containing foreign matter. (Foreign matter is clogged.) (Ii) The manufacturing cost is high because the shape of the valve body or the main body becomes complicated. (iii) Since these structures expose projections and additional objects in the flow channel, it is difficult to secure the flow velocity energy of the fluid having a high flow velocity and the strength against foreign object collision. (Iv) When the valve element is almost fully closed, the flow path becomes very narrow, so that the effect of the projections and additional objects is reduced. (V) In both cases, when the center of the valve element and the center of the valve shaft are the same axis and have a sealing structure, the structure is not suitable for high-temperature fluid.

FIG. 8 shows a non-cylindrical shape in which the width of the recess on the downstream side of the valve seat is reduced by a bearing portion so that the cross-sectional area of the flow path becomes constant when the valve element rotates. Doing
Also, the purpose of the present invention is not to suppress cavitation and noise, but to reduce torque.

An object of the present invention is to solve the above-mentioned problems of the prior art and to improve the following points. 1) Cavitation generated in the valve contraction part is reduced, and the suppression of cavitation leads to noise suppression. (Case of liquid fluid) 2) Change amount of Cv value per movement amount of valve opening is reduced to improve controllability. 3) A structure that can be applied to a fluid containing a slurry or a foreign substance. 4) Enables use at a high flow rate as a structure that does not partially apply unreasonable stress (high flow rate energy, foreign matter collision, etc.). 5) The seal structure can be easily designed using existing technology, and the structure can be used even at high temperatures. 6) The structure is realized with minimum production cost.

[0020]

In order to solve the above-mentioned problems, the present invention adopts an eccentric butterfly in which a sealing surface between a valve body peripheral surface and an inner surface of a main body does not pass through the center of a valve stem when fully closed. In the valve, the inner diameter of the main body immediately after the valve seat is an enlarged inner diameter portion having an enlarged sectional shape symmetrical with respect to the center of the flow path, and the center of the valve shaft is located at the enlarged inner diameter portion. I have.

In addition, the outer diameter of the valve body and the inner diameter of the main body of the valve seat portion are set to be 0.8 times or less of the inner diameter D of the pipe, and the inner diameter of the main body immediately after the valve seat portion is expanded to almost the same size as the inner diameter of the pipe. It is characterized by suppressing noise and cavitation generated from the valve body.

Further, as a structure in which the valve seat and the valve shaft are eccentric,
It is characterized in that it is possible to have an elastic sealing mechanism with existing technology.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the embodiment of the present invention will be described with a theoretical explanation (cavitation) and an actual measurement (experiment) apparatus (FIG. 3) of the means for solving the problems described in the preceding section, and the results of the experiment. This will be described with reference to a graph (FIG. 4) and an example (FIGS. 1 and 2).

FIG. 5 shows the flow (flow state) of a general eccentric butterfly valve shown for comparison with the present invention. The fluid flowing out of the gap between the valve body and the main body is shown in FIG.
The portion A, which is sandwiched between the low-speed portion by the vortex on the back side of the valve body and the boundary surface of the pipe wall where the flow velocity is zero, has the highest speed and the pressure decreases. Further, in the contraction portion, the difference in flow velocity between the vortex and the vicinity of the tube wall is large, which causes the bubble nuclei to grow into cavitation bubbles.

In the contraction section A, the pressure rapidly decreases, and the bubbles rapidly increase. The bubbles continue sufficiently. When the bubbles further increase, the pressure is restored and the bubbles collapse. This is the cause of the occurrence.

In addition, since the contraction portion A is close to the tube wall, the impact when the air bubbles are crushed increases.

The cause of the cavitation is caused by the portion where the pressure is rapidly reduced as described above, and the cavitation becomes severe requires time for the growth of bubbles. For this reason, in order to suppress cavitation, it is necessary to prevent the generation of a low-pressure portion and not to allow time for growing bubbles.

Therefore, in the present invention, as shown in FIG.
An eccentric butterfly valve in which a sealing surface of a valve seat 32 and a valve body 33 formed on a main body 31 when fully closed is eccentric from a center of a valve rod 34, and an inner diameter of the main body 31 immediately after the valve seat 32 and thereafter. With an enlarged inner diameter portion 31A having an enlarged cross-sectional shape symmetrical with respect to the center of the flow path (for example, having a circular cross-section).
The center of the valve shaft 34 is located at the inner diameter enlarged portion 31A. In FIG. 1, 35 is a pipe flange, and 36 is a pipe.

In the present invention, the ratio of the inner diameter φd of the valve seat to the inner diameter φD of the pipe is set to 80% or less, and the inner diameter of the enlarged inner diameter portion 31A of the main body immediately after the valve seat increases to the inner diameter φD of the pipe. The axial center of 34 is located at the inner diameter enlarged portion 31A.

FIG. 2 shows an example of a seal portion of the valve seat portion 32.
(A) shows a state in which a metal seat ring 32a is fitted into a concave portion of the inner diameter end surface of a valve seat portion 32 formed at a side end portion of a main body 31, and is pressed and held by a valve seat presser 31a via an elastic plate-like portion 31b. ing. 4B, the resin-based seat ring 32b is attached closely to the concave portion of the valve seat retainer 31a so as to contact the outer peripheral edge of the valve body 33.

FIG. 3 is an explanatory view showing a flow state when the eccentric butterfly valve of the present invention configured as described above is used. The inner diameter φd of the valve seat 32 in contact with the peripheral edge of the valve body is shown in FIG. Since the pressure is reduced, the contraction of the contraction portion A can be reduced, and the flow velocity of the contraction portion can be reduced to reduce the pressure drop.

Further, the low-speed portion B and the contraction portion (high-speed portion) A of the vortex
, The difference between the velocities can be reduced, and the chance that the bubble nuclei begin to grow is reduced.
In addition, the amount of generated cavitation bubbles that collapse near the tube wall is reduced.

The following effects are obtained as described above.

1) The generation of bubbles is suppressed by reducing the pressure drop in the contraction portion.

2) The speed difference between the contraction part and the vortex is small, and the chance of bubble growth can be reduced.

3) Even if bubbles are generated, the pressure recovers quickly and the time for the bubbles to grow is short because the inside diameter immediately after the valve seat is large. Therefore, the growth of cavitation bubbles can be suppressed.

4) The amount of cavitation bubbles that collapse near the pipe wall is reduced, and damage to the pipe can be reduced.

FIG. 4 shows a pipe having a nominal diameter of 200 A (inner diameter φ2).
00.3), the result of measuring the FL value and the Kc value of the present invention when the inner diameter of the valve seat portion was set to φ150, the vertical axis represents the FL value and the Kc value, and the horizontal axis represents the valve opening (%). And are indicated by solid lines. The broken line shown in the graph is
9 shows the FL value and Kc value of a general eccentric valve. As can be seen from these results, the FL value and the Kc value of the present invention are significantly increased.

The valve seat diameter (φd) of a general eccentric valve is set to about 95% of the pipe inner diameter (φD). This dimension is a dimension set so as not to interfere with the pipe when the valve element rotates, and is not a dimension taking into account the suppression of cavitation as in the present invention.

The inner diameter ratio of the test described in the present invention is (φd /
φD) is 75%, but it is confirmed from other experimental results that an effect is obtained at an inner diameter ratio of 80% or less, and that the effect is not different from the case of 75% even if it is 70%.

In the above measurement results, the cavitation initiation coefficient (Kc value) is a value obtained by converting the start of cavitation into a coefficient. Further, the pressure recovery coefficient (FL value) is a value obtained by converting the degree of pressure recovery at the time of passage through the valve into a coefficient. The larger the FL value, the smaller the pressure recovery, and the less likely cavitation occurs. From the above,
When the inner diameter ratio (φd / φD) is 80% or less, there is an effect of suppressing cavitation (= reducing noise).

Next, regarding the advantage of the eccentric structure and the positional relationship between the valve seat and the valve stem, the position of the valve stem is symmetrical with respect to the center of the flow path in the pipe diameter immediately after the valve seat. The presence of the existing eccentric structure has the following effects.

1) The maximum effect can be obtained by expanding the cavitation suppressing effect as soon as possible after the throttle is narrowed at the valve seat.

2) Because of the eccentric structure, the tool structure can be easily designed by the existing technology.

On the other hand, when the center of the valve seat and the center of the valve stem are the same center valve, in order to provide the seal structure, the structure must be complicated or the enlarged position must be located downstream downstream of the valve seat. As a result, the effect of suppressing the cavitation by increasing the inner diameter decreases.

As for the improvement of the control performance, by reducing the diameter of the valve seat as described above, the valve capacity coefficient (Cv value) becomes smaller in proportion to the square of the diameter than that of a general eccentric valve having the same diameter. Cv per moving amount from fully closed to fully open
The value change amount becomes small. Thereby, controllability can be improved.

As another embodiment, other than the one shown in FIG. 2, a seat ring of a valve seat portion for sealing may not be provided and may be integrated with the main body.

[0048]

As described above, according to the present invention,
When the valve is fully closed, the sealing surface between the valve body peripheral surface and the body inner surface does not pass through the center of the valve stem. The following effects can be achieved by forming the inside diameter enlarged portion having a shape and positioning the center of the valve shaft at the inside diameter enlarged portion.

(I) As can be seen from the results of FIG. 4 showing the FL value and the Kc value on the vertical axis and the valve opening (%) on the horizontal axis, the present invention has the effect of suppressing cavitation.
This has the effect of reducing the accompanying noise.

(Ii) Since there are no protrusions or additional substances, the shape is simplified, and it can be used for a fluid containing a slurry or a foreign substance. In addition, no excessive stress is applied in part and the manufacturing cost is reduced.

The outer diameter of the valve body and the inner diameter of the main body of the valve seat portion are set to be 0.8 times or less of the inner diameter D of the pipe, and the inner diameter of the main body immediately after the valve seat portion is expanded to substantially the same size as the inner diameter of the pipe. As a result, the valve body can be made smaller, so that the amount of change in the valve capacity coefficient Cv per movement amount of the valve opening can be made smaller, and the change in the valve opening and the flow rate can be made finer, so that controllability can be improved. Similarly, a reducer is no longer necessary under the condition that the valve diameter is reduced by the conventional reducer. In addition, the conventional reducer does not have an enlarged chamber as in the present invention, so that cavitation is not reduced.

Further, because of the eccentric valve structure, the sealing structure of the valve seat can be designed to be easily designed by the existing technology, and the cavitation suppressing effect can be maximized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a low-noise butterfly valve according to an embodiment of the present invention, taken in a direction perpendicular to a valve stem.

FIGS. 2 (a) and 2 (b) are cross-sectional views of essential parts showing different embodiments of a seal portion in a valve seat portion of the present invention.

FIG. 3 is an explanatory view of the operation of the butterfly valve of the present invention.

FIG. 4 is a graph showing results of an FL value and a Kc value with respect to a valve opening degree derived from an experiment of the present invention.

FIG. 5 is an explanatory diagram showing a flow state of a general eccentric butterfly valve.

6A and 6B show a conventional example, in which FIG. 6A is a sectional view, and FIG. 6B is a sectional view taken along line bb in FIG.

7A and 7B show another conventional example, in which FIG. 7A is a longitudinal sectional view, and FIG.
FIG. 4 is a plan view of a valve body.

8A and 8B show another conventional example, in which FIG. 8A is a longitudinal sectional view, and FIG.
FIG. 2 is a sectional view taken along line II-II in FIG.

[Explanation of symbols]

 31 Body 31A Inner Diameter Enlarged Part 31a Valve Seat Holder 32 Valve Seat 32a Metal Seat Ring 32b Resin Seat Ring 33 Valve Body 34 Valve Rod 35 Piping Flange 36 Piping φd Body Inside Diameter of Valve Seat φD Piping Inner Diameter

Claims (3)

[Claims] An eccentric butterfly valve in which a sealing surface between a valve body peripheral surface and a main body inner surface does not pass through the center of a valve stem when fully closed.
A low-noise body characterized in that the inner diameter of the main body immediately after the valve seat is an enlarged-diameter portion having an enlarged cross-sectional shape symmetrical with respect to the center of the flow path, and the center of the valve shaft is located at the enlarged-diameter portion. Butterfly valve. 2. A structure in which the outer diameter of the valve body and the inner diameter of the body of the valve seat portion are 0.8 times or less of the inner diameter D of the pipe, and the inner diameter of the main body immediately after the valve seat portion is expanded to substantially the same size as the inner diameter of the pipe. The low-noise butterfly valve according to claim 1, wherein noise and cavitation generated from the valve body are suppressed. 3. The low-noise butterfly valve according to claim 1, wherein an eccentric structure of the valve seat and the valve shaft can be provided with a sealing mechanism having elasticity by an existing technology.