JPH01193488A - Valve device - Google Patents

Abstract

PURPOSE:To prevent a valve body from damage due to cavitation by providing a cylinder portion directed to a fluid passage hole in the inner wall of the valve body adjacent the outflow side of said fluid passage hole. CONSTITUTION:A cylindrical portion 20 directed to a fluid passage hole 6 in a seat ring 7 is provided projectingly integrally on a portion opposed to said hole 6 of the outflow side inner wall surface of a valve body 1 and formed inside with a cup-like vacant chamber 21. Thus, cavitation bubbles generated in a throttle section can be confined in the cylindrical portion 20 by the vortex action of fluid, so that the cavitation bubbles near the secondary inner wall of the valve body 1 are not collapsed. Thus, the valve body 1 can be prevented from damage caused by the cavitation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a valve device that controls the flow rate of a controlled fluid.
In particular, the present invention relates to improvements in valve devices in which the pressure difference between the downstream side and the downstream side is relatively large.

[Conventional technology]

Various types of valve devices have been known for controlling the flow rate of fluid flowing in pipes, and they are selected depending on the type of fluid, pressure, temperature, etc. Among them, plugs and fluid passage holes are particularly popular. A single-seat valve that controls the flow rate with a seat ring is usually constructed as shown in FIG. To roughly explain this in the figure, 1 is a valve body that connects an upstream pipe line and a downstream pipe line (none of which are shown), and the inside thereof is separated by a partition wall 2 between an inlet side and an outlet side passage 3, 4. A seat ring 7 having a fluid passage hole 6 is fitted and fixed in a hole 5 provided in the center of the partition wall 2 . 8
12 is an operating shaft that is slidably penetrated through the upper lid 8 via a packing 13; A plug 14 is integrally provided at the inner end.

The plug 14 is slidably inserted through a bush 16 into a guide ring 15 fitted and fixed to the upper opening 9 of the valve body 1, and has a substantially conical shape with an annular seat surface 14B at its lower end. A characteristic section 14A is integrally provided. When the characteristic portion 14A is moved forward and backward with respect to the fluid passage hole 6 by the reciprocating motion of the operating shaft 12, the passage hole 6
Since the area of the constriction part a formed between the characteristic part 14A and the characteristic part 14A changes according to the stroke of the operating shaft 12, the flow rate is controlled.

Note that 17 is a packing follower.

[Problem to be solved by the invention]

However, in such conventional valve devices, cavitation (gas in the fluid) occurs when the pressure is reduced to near or below the vapor pressure of the liquid at the constriction section a, which has the smallest mechanical dimension, due to the flow state of the fluid. pores that contain steam). Here, the generated vapor bubbles are called cavitation bubbles 6. In particular, in such a conventional structure, the flow after passing through the constriction part a flows along the characteristic part 14A and the inner wall part of the valve body 1, so that the high impingement generated when the cavitation bubbles 6 mentioned above collapse. 6. Fluid passage holes exposed to flow due to pressure. The characteristic portion 14A and the secondary side, that is, the downstream inner wall surface of the valve body 1, are damaged by so-called cavitation, and in severe cases, holes are formed in the wall surface of the valve body 1.

Therefore, in a valve device that significantly reduces the pressure of high-pressure fluid, the valve body 1. The seat ring 7, plug 14, etc. must be made of expensive wear-resistant materials, and the plug 1
There were problems such as the need for frequent inspections and replacements.

Therefore, the present invention solves the above-mentioned problem, and provides a valve with a simple structure that confines the collapse of cavitation bubbles at a position away from the inner wall of the valve body, thereby preventing the inner wall of the secondary side from being damaged by cavitation. The purpose is to provide a device.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an inner cylindrical portion facing the fluid passage hole on the inner wall of the valve body facing the outflow side of the fluid passage hole provided in the valve body, and the cylindrical portion is connected to the fluid passage hole provided in the valve body. It is provided facing the passage hole, and this cylindrical portion forms a υ cavity.

[Effect]

In the present invention, the cavitation flow generated downstream of the constriction portion formed by the fluid passage hole and the seat portion of the plug flows into the cavity chamber. At this time, the fluid collides with the bottom of the cavity and flows out along the inner peripheral wall, so a macroscopic vortex is generated due to the speed difference due to friction between the fluid flowing into the center of the cavity and the fluid flowing out from the outside. Since the outside of the vortex becomes a dense liquid phase due to centrifugal force, the outer periphery of the cavity becomes liquid, trapping the υ cavitation bubbles in the center of the interior of the cavity.

Therefore, the collapse of the cavitation air vortex is caused by the collapse of the cavitation air vortex.
This will not occur near the next inner wall.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view of essential parts of an embodiment of a valve device according to the present invention. Note that the same component parts in the figure as in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted.

In the figure, in this embodiment, a cylindrical portion 20 is integrally provided on the inner wall surface of the outflow side of the valve body 1 at a location facing the fluid passage hole 6 of the IJ ring T, and protrudes toward the fluid passage hole 6. The interior thereof is a hollow chamber 21 shaped like a pot. In this case, in this embodiment, the cylindrical portion 20 is formed integrally with the valve body 1, but as shown in FIG. Then, the cylindrical part 20 of the cavity forming member 23, which is manufactured separately from the valve body 1, is inserted into the outflow side passage 4 through the fitting hole 22 through the gasket 25, and then the bolt (not shown) Of course, the cavity forming member 23 may be fixed to the valve body 1.

Note that the other configurations are the same as the conventional structure shown in FIG.

In the valve device having such a configuration, when the characteristic portion 14A rises with the rise of the operating shaft and a gap is created between it and the fluid passage hole 6, the controlled fluid in the inflow side passage 3 It flows into the outflow side passage 4 through the passage hole 6. At this time, cavitation bubbles are generated on the downstream side of the constricted portion a due to the pressure drop, and these cavitation bubbles flow into the cavity chamber 21 of the cylindrical portion 20 together with the fluid stream. After colliding with the bottom surface 29 of the cavity 21, the fluid rises along the inner peripheral surface of the cylindrical portion 20 and flows out of the cylindrical portion 20. Therefore, inside the cavity 21, the macroscopic vortex 30 is generated due to the speed difference due to friction between the fluid Ll flowing into the cavity 21 and the fluid Ll rising along the inner peripheral surface and flowing out to the outside. Occurs in the center of the interior. Therefore, the outer side of the υ vortex 30 becomes a dense liquid phase due to the centrifugal force, so that the inner peripheral edge side of the cavity chamber 21 confines the liquid and the cavitation bubbles in the inner center. Therefore, collapse of cavitation bubbles does not occur near the inner wall on the outflow side of the valve body 1, and damage to the valve body 1 due to cavitation is reduced and prevented.

That is, according to the present invention, the cavitation bubbles are trapped in the cavity chamber 21 by the action of the fluid stream, and can be prevented from approaching the secondary side inner wall of the valve body 1 together with the fluid stream. Even in a valve device in which there is a large pressure difference between the front and rear parts of the valve, damage due to cavitation can be prevented without making the valve body 1 of an expensive wear-resistant material.

It should be noted that, although the above embodiment shows the case where the invention is applied to a single-seat valve consisting of a plug and a seat ring, the present invention is not limited to this in any way, and it goes without saying that it can be applied to cage valves, etc. .

〔Effect of the invention〕

As explained above, according to the valve device according to the present invention, the cavitation bubbles generated in the throttle part are transferred to the inside of the cylindrical part provided on the outflow side of the fluid passage hole so as to face the fluid. Since cavitation bubbles can be well confined, collapse of cavitation bubbles does not occur near the secondary inner wall of the valve body, and therefore damage to the valve body due to cavitation can be prevented. Therefore, there is no need to use expensive wear-resistant materials, and it can be manufactured at low cost.
This has the effect of improving durability, lengthening maintenance cycles such as checking and replacing plugs, and being economical.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a main part showing one embodiment of a valve device according to the present invention, Fig. 2 is a cross-sectional view of a main part showing another embodiment of the present invention, and Fig. 3 is a conventional example of a valve device. FIG. DESCRIPTION OF SYMBOLS 1... Valve body, 2... Partition wall, 3... Inflow side passage, 4... Outlet side passage, 6... Fluid passage hole,
T fist... seat ring, 14, fist... plug, 14A
@”・[Stock]Characteristics part, 20... Cylindrical part, 21...
・Cavity chamber, a... constriction section, bl... cavitation bubble. Patent applicant: Yamani-Newel Co., Ltd. Agent: Masaki Yamakawa (and 2 others) Figure 1 Figure 2 Figure 11:I

Claims (1)

[Claims] In a valve device that controls the flow rate of a controlled fluid by opening and closing a fluid passage hole provided in a partition wall that partitions the inside of the valve body into an inflow and an outflow side passage using a plug, the valve body faces the outflow side of the fluid passage hole. A valve device characterized in that a cylindrical portion is provided on an inner wall facing the fluid passage hole, and a hollow chamber is formed by the cylindrical portion.