JPH0447502Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The invention of the present application is a new technology related to a movable orifice valve.

[Prior Art] A movable orifice valve is a valve that is installed in the direction of flow of fluid and used to reduce pressure. Normal 2
Two perforated plates are erected and one of them is slid to adjust the communication range of the holes with the other, thereby adjusting the head loss to a desired state. Figure 3 is an example of this, and is a proposal that improves this conventional type. In other words, the "adjustable head loss valve" (Japanese Patent Publication No. 62-3342) is 2
Recognizing that a head loss valve (movable orifice valve) in which one of two perforated plates is fixed and the other is movable is known, the perforated plate 2a on the downstream side is fixed, and the orifice 3a is shaped into a cylindrical shape. The perforated plate 4a on the upstream side is movable perpendicularly to the direction of flow of the fluid, and the orifice 5a is shaped like a truncated cone with a cross-sectional area increasing toward the upstream side. These features of the orifice allow the former to precisely control valve head loss, and the latter to prevent excessive valve head loss when the valve is fully open (the state in which both orifices overlap, as shown in Figure 3). It claims that head loss can be avoided.

[Problems to be solved by the invention] A valve that is interposed in a flow path and causes fluid pressure changes before and after the valve cannot avoid the cavitation phenomenon. When the fluid drops below its vapor pressure, a minute cavity is generated within the fluid, and when the pressure recovers to above the vapor pressure downstream, this cavity is destroyed, but at this time a huge pressure rise occurs in the nearby water. This causes vibration, noise, metal fatigue and rapid erosion of the pipe inner wall, and the downstream pipe suffers uneven and deep localized erosion.

Since orifice valves also have inherent structural characteristics that make them prone to this, they are more likely than other types to locally break the pipe wall on the downstream side and destroy the pipe line within a relatively short period of time. strong.

In order to solve the above-mentioned problems, the present invention aims to provide a new movable orifice valve that minimizes the adverse effects of cavitation on the downstream pipe wall.

[Means for Solving the Problems] The movable orifice valve according to the invention is characterized in that at least the perforated plate on the downstream side is provided with circular holes whose respective axes are inclined toward the axis of the conduit. The above problem was solved by this method.

[Operation/Example] The operation of the present invention will be explained based on FIG. 1 showing an example.

Movable orifice valve 1 installed in the pipeline in the figure
In this example, a perforated plate 2 on the downstream side is fixed to a conduit, and orifices 3A, 3B, . . . having axes CA, CB, .

On the other hand, another perforated plate 4 which is in close contact with this perforated plate 4 is slidably installed on the upstream side of the perforated plate 2, and orifices 5A, 5B, . . . are bored through this plate.

The orifice 5 on the upstream side may be parallel to the axis C of the pipe, or the orifice 3A,
3B, . . . may be given a common inclination to the axes CA, CB, . . . Due to this structural feature, the cavities generated in the fluid whose pressure has decreased are forced by the inclination of the orifice after passing through the orifice, and proceed obliquely along the extension line, converging from the four circumferences near the axis C of the conduit, and intersecting each other. collide with each other. Therefore, the cavity collapses at the center of the pipe without hitting the pipe wall, and any influence on the pipe wall can be avoided.

FIG. 2 shows another embodiment, whereas in FIG. 1 the orifices are concentrated at one point P on the axis, in this figure the orifice axes CA, CB, ... have the same inclination angle with respect to C, The location of the collision/collapse of the cavity is Q, R, S,
An example is shown in which the negative effects of cavitation are further dispersed and reduced by dispersing it to multiple points.

[Example] Some additional information will be given regarding the front sectional views of the example shown in FIGS. 1 and 2.

Fluid moves in the pipe 6 forming the conduit from the left in the figure in the direction of the arrow. The annular main body of the movable orifice valve 1 is sandwiched between two flanges 8 and 9 fixed to the pipe 6 from the left and right sides, and screwed with bolts 10. Seal rings 11 and 12 are sandwiched between the left and right circumferences for water sealing. The perforated plate 2 on the downstream side is fitted and fixed in the recess of the annular body 7, and the perforated plate 4 on the upstream side
slides up and down while remaining in close contact with the perforated plate 2. As an example for sliding, it has been shown that rotation of the manual handle 13 is converted into vertical movement of the perforated plate 4 which is integrally suspended via the threaded rod 14 and the screw 15. Needless to say, this is just one example.

[Effects of the invention] As described above, the movable orifice valve according to the invention of the present application concentrates the colliding collapse of the cavities in the fluid caused by the pressure difference near the axis of the pipe that is farthest from the pipe wall. Therefore, the negative effects of cavitation are kept to a minimum. Therefore, problems caused by the nature of orifice valves can be solved to the maximum extent possible.

[Brief explanation of the drawing]

FIGS. 1 and 2 are front sectional views showing different embodiments of the present invention, and FIG. 3 is a front sectional view showing a conventional technique. 1... Movable orifice valve, 2... Perforated plate (downstream side), 3A, 3B... Same orifice, 4... Perforated plate (upstream side), 5A, 5B... Same orifice, C
...Axis of the conduit, CA, CB...Axis of the orifice, P, Q, R, S, ...Fixed point on the axis C.

Claims (1)

[Scope of utility model registration request] Two perforated plates perpendicular to the flow direction of the fluid are interposed in the conduit and are placed in close contact with each other, one of which is fixed and the remaining one is slidably movable with respect to the other. In a movable orifice valve that variably adjusts head loss depending on the communication range of the circular holes, a circular hole whose axis is oriented toward the axis of the conduit is bored in at least the perforated plate on the downstream side. A movable orifice valve characterized by: