JP2514638Y2 - Butterfly valve with cavitation suppression function - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a butterfly valve which is connected to a pipe and opens and closes the pipe by rotating a valve body, especially a butterfly valve having a function of suppressing cavitation occurring in a relatively small opening range. Pertain to.

[0002]

2. Description of the Related Art In a butterfly valve used in a water pipe, mere corrosion or wear is unlikely to be a factor for shortening the service life, but the valve member is locally worn by cavitation, and the worn member must be replaced early. Be strong. In addition, the occurrence of cavitation causes noise and vibration. When the cavitation gradually opens the butterfly valve from the closed state, there is a pressure drop immediately downstream of the valve body, and when the pressure drop becomes less than the vapor pressure of the fluid, the fluid boils and bubbles are generated. As the pressure rises slightly downstream of the valve body, the bubbles collapsing and generate noise and vibration, and abnormally early wear of the valve member makes it unusable.

As described above, improving the cavitation and the noise caused by the cavitation has been an important proposition for the entire valve, but as a conventional technique for solving this proposition in the butterfly valve, there is shown in FIG. No. 57-157866 is proposed. When the disc 2a is closed inside the cylindrical bore 1a, it is angularly offset from the vertical axis of the bore and is fitted obliquely. Therefore, the disk 2a has an oval shape, and is angularly displaced from each other with respect to the plane axis of the semicircular wall portion that is divided into two parts at the center, so that the disk 2a has a V shape. The feature of the disk 2a is that a large number of ribs 10a and 10b extending toward the upstream side and the downstream side near the outer periphery are provided in a protruding manner to substantially form a fluid obstacle. The ribs 10a and 10b are provided in the bore 1a when the disc 2a is closed.
Extend substantially parallel to the longitudinal axis of and form two semi-circular rows. As a result of adopting the above-mentioned configuration, this conventional technology achieves reduction of cavitation, provision of complete closure, provision of excellent control characteristics, low aerodynamic noise level, and low torque and low torque that conventional technology cannot achieve. It claims to have provided a noise butterfly valve.

[0004]

Although this prior art can achieve the desired low torque and low noise, another problem arises because the valve body (disc) is provided with a special rib. One of them is that when the fluid passing through the pipeline is not fresh water but sewage containing solid foreign matter, foreign matter (hard small pieces or long strings) mixed in the fluid is between the ribs. To bite into. When the valve is closed, the ribs project almost parallel to the flow of the pipeline.Once the foreign matter is caught, the ribs on the upstream side push upward toward the flow even if the valve opens, further removing the caught foreign matter. Tends to embrace deeply. Further, there is a possibility that the foreign matter may be caught and the valve may not be completely closed again.

The second problem is that when the valve is fully opened, the ribs project at a right angle to the flow in the central part of the flow, resulting in a large fluid resistance, and in the vicinity of the center, where the flow velocity is the largest, there is a pressure loss. Is to grow.

The third problem is that in the prior art, the flow force at the small opening of the valve is reduced to suppress the occurrence of cavitation. Considering the cause of the occurrence of cavitation, when the valve is opened, , The pressure drop occurs due to the pressure imbalance between the half of the rotating valve body toward the upstream side and the half of the rotating valve body toward the downstream side, and the pressure drop becomes less than the vapor pressure of the fluid. Is. When opening the valve, the half side of the valve element that goes upstream is called the orifice side, and the half side that goes downstream is called the nozzle side.In this technology, ribs are provided protruding on the orifice side and nozzle side of the valve element. However, the effect is only to try to damp the flow force, and the pressure imbalance on both sides, which is the basic cause of cavitation, is not solved at all.

Further, in order to provide a large number of complicated comb-teeth-shaped ribs on the surface of the valve body as in the prior art, it is common to mold and cast a complicated mold. It is a burden that cannot be ignored. When wear due to cavitation is concentrated on the rib portion, the valve itself must be disassembled and the entire valve body must be replaced, which is a major problem in terms of maintenance. Further, depending on the piping route in the factory or building, the vertical flow direction may be reversed due to operational requirements. In such a case, in the conventional technique, unless the corresponding means other than removing the valve body and reattaching it in the opposite direction, there is a problem that it cannot be carried out at all in the pipeline where the flow direction is frequently changed.

In order to solve the above-mentioned problems, the present invention has a function of suppressing noise and vibration caused by cavitation, reduces pressure loss in a fully closed state as much as possible, and foreign substances mixed in a fluid. It is an object of the present invention to provide a butterfly valve that can prevent the adverse effects of the above and can relatively easily cope with the case where the flow direction of the pipeline needs to be reversed.

[0009]

A butterfly valve having a cavitation suppressing function according to the present invention has a half-circumferential side 2A which is directed upstream when the valve body 2 is rotated from the closed direction to the open direction.
The annular ridge 4 having a substantially equal thickness is detachably fixed to the downstream surface of the above, and a plurality of through holes 7 that are directed to the center 2C of the valve body surface are radially pierced in the ridge 4 by the above-mentioned problems. Solved. Further, in this configuration, it is a desirable embodiment that the average hole diameter of the through holes is approximately 10% of the valve opening diameter.

[0010]

[Function] By means of the ridges detachably fixed to the so-called orifice-side downstream surface of the valve body, the flow force squeezed between the end of the valve body and the inner wall of the valve box is suppressed, and this suppressed flow is suppressed. Since the force is directed to the center of the downstream surface through the through hole, it becomes almost in equilibrium with the flow force from the so-called nozzle side,
Prevents pressure drop due to pressure imbalance. Even when the valve is further opened to the fully open state, the ridge only fixes the one side surface of the valve body in an annular shape, and ribs protrude on both sides of the valve body to obstruct the flow path as in the prior art. The pressure loss is obviously smaller than that of the existing configuration.

Since the ridges are removably attached to the surface of the valve body, even if the flow direction needs to be suddenly reversed, the attachment surfaces to the valve body surface can be simply turned upside down. It can be dealt with immediately and avoids the laborious work of removing and reversing and reattaching the valve box itself. This is also the case when only the ridge is abnormally worn due to cavitation, and the ridge can be replaced by a simple operation of replacing the ridge with a spare part.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a longitudinal sectional view perpendicular to a valve shaft showing an embodiment of the present invention, FIG. 2 is a side view of a valve body, and FIG. 3 is a cross section in which the flow direction and the opening / closing direction of the valve body are different from those in FIG. The figure is shown. 1 and 2
In the above, the butterfly valve connected to the pipe pivotally supports the valve body 2 that rotates at a right angle around the valve shaft 3 in the valve box 1 from both sides, and the rotation of the valve body 2 opens and closes the pipe. When the valve body 2 is rotated from the fully closed state to the open direction, the half circumferential side toward the upstream side of the flow is the orifice side 2A, and the half circumferential side toward the downstream side of the flow is the nozzle side 2B. The annular ridge 4 is the orifice side 2A
Is fastened and fixed by a bolt 6 onto a mounting seat 5 provided on the surface on the downstream side of. The mounting seats 5 are similarly provided on both sides of the front and back of at least half of the circumference of the valve body (both sides of the entire circumference in this embodiment), and the bolt holes 8 are provided on both sides so that the protrusions can be mounted. Because it is perforated,
The mounting position can be appropriately selected according to the mounting direction of the valve and the flow direction.

As shown in FIG. 2, the protrusion 4 has a center 2C of the valve body 2.
A plurality of through-holes 7 that point to Through hole 7
Has a function of guiding the restricted fluid on the orifice side 2A to the downstream center C on the surface of the valve body 2, but foreign matter mixed in the fluid into the through hole 7 (such as a hard small piece or a long string). When things (such as things) are locked and stay, the action will be halved,
In consideration of this point, the hole diameter must be selected, and in consideration of the formation of a bypass effective for preventing cavitation and the passage of foreign matter, the case where the average hole diameter is approximately 10% of the valve diameter is the most desirable mode. I have confirmed that there is.

FIG. 3 shows a case where the flow direction and the opening / closing direction of the valve body are different from those in FIG. 1. Even if the flow direction or the opening / closing direction of the valve body is changed after the valve is installed, the ridges are opened more than the valve body is closed. It is shown that it can be arranged on the downstream side of the half-circumferential side (orifice side) that faces the upstream side when rotating in the direction.

[0015]

EFFECTS OF THE INVENTION The present invention has the effect of suppressing the occurrence of cavitation, which is likely to occur in a range where the valve body has a small opening degree, based on the above-described structure, and also preventing noise and vibration accompanying it. Further, when the opening of the valve body exceeds this range and the opening degree becomes large, the obstacle for cavitation countermeasure is released, so that the pressure loss until full opening of the flow velocity is reduced. Compared with the prior art of FIG. 4 provided for the same purpose, even if the fluid is used for a conduit containing solid foreign matter instead of fresh water, the concern that the foreign matter will be caught is almost wiped out, and the defective state at the time of fully closed. Less likely to cause

Since the ridge is detachably fixed to the valve body, even when the flow direction and the opening / closing direction of the valve are changed after the valve is installed, the ridge is rotated from the closed to the open direction. The same effect can be obtained by mounting on the downstream side of the half-circumferential side (orifice side) toward the upstream side. Further, if there is no need to throttle the valve, there is an advantage that the ridge can be removed from the valve body and replaced with a butterfly valve with a small pressure loss.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional front view of an embodiment of the present invention.

FIG. 2 is a side view of only the valve body.

FIG. 3 is a vertical sectional front view showing a mode different from FIG. 1 of the same embodiment.

4A and 4B are vertical sectional front views showing two aspects of the prior art by FIGS.

[Explanation of symbols]

 1 valve box 2 valve body 3 valve shaft 4 ridge 5 mounting seat 6 bolt 7 through hole 8 mounting hole

Claims (3)

(57) [Scope of utility model registration request] 1. A butterfly valve, which is connected to a pipeline and opens and closes the pipeline by rotating the valve body 2, has a downstream side of a half-circumferential side 2A that is upstream when the valve body 2 rotates in the opening direction from the closed state. An annular ridge 4 with almost equal thickness is detachably fixed to the surface,
A butterfly valve having a cavitation inhibiting function, characterized in that a plurality of through-holes (7) directed toward the center (2C) of the valve body surface are radially bored in the ridges (4). 2. The butterfly valve according to claim 1, wherein the through hole has an average hole diameter of approximately 10% of the valve opening diameter. 3. The mounting seat 5 according to claim 1 or 2, wherein a symmetrical mounting seat 5 and a plurality of mounting holes 8 formed in the mounting seat are provided on the front and back sides of at least half of the circumference of the valve body. A butterfly valve with a characteristic cavitation suppression function.