KR101092527B1 - Cavitation and surging prevention of pressure reducing control valve - Google Patents

Abstract

PURPOSE: A pressure reducing control valve for preventing cavitation and pulsation is provided to prevent damage to a valve and noise by reducing a flow rate of fluid using a baffle plate. CONSTITUTION: A pressure reducing control valve for preventing cavitation and pulsation comprises a disc. The disc comprises a seat fixing plate(21) and a scream plate. The fluid is transferred through a transfer hole(23) of the seat fixing plate. The scream plate is formed on the outer circumference of the seat fixing plate. The scream plate reduces the feeding speed of the fluid transferred to through the transfer hole. The baffle plate is formed in the outer circumference of the scream plate. The frequent cavitation and pulsation surging are prevented when the pressure reduction control valve operates at a low opening rate.

Description

Cavitation and Surging prevention of Pressure reducing control valve

The present invention relates to a pressure reducing control valve for preventing cavitation and pulsation, and more particularly, a transfer hole is formed so that fluid flows into the seat fixing plate, and the outer periphery of the seat fixing plate is used to Since a scrim plate having a lattice plate is formed on the outer circumference to reduce the feed speed, when the disc is opened and closed, the fluid flows through the transfer hole and bumps through the lattice plate of the scrim plate to reduce the flow rate of the fluid, thereby reducing the pressure. When the valve is operated at a low opening rate, it prevents frequent cavitation and pulsation, thereby preventing noise and valve breakage, thereby increasing the life and efficiency of the valve, and causing a loss at a high opening rate that requires a large flow rate. It does not increase the loss of the valve itself while suppressing the cavitation Since the maximum CV value of the valve itself does not change due to the selective loss in the opening rate, the present invention relates to a pressure reducing control valve for preventing cavitation and pulsation that sends a sufficient flow rate and controls cavitation.

A general pressure reducing control valve is installed in a fluid supply pipe, has an inlet and an outlet, and a pipe-shaped body seat is fixedly bonded to a globe-shaped round body, and the disk engaged with the body seat can be opened and closed by moving up and down. The disk is connected to the disk stem to protrude upward, the stem is connected to the diaphragm is to close the disk by the pressure flowing through the pilot valve on the upper portion of the diaphragm.

The lower part of the diaphragm has an inlet hole so that the fluid of the inlet can freely flow in and through the hole, the pressure of the inlet is transmitted to the lower part of the diaphragm so that the pressure of the inlet and the pressure of the lower part of the diaphragm are the same.

In addition, when foreign matter enters the lower part of the diaphragm and the diaphragm does not come into close contact with the lower part, the disk connected to the diaphragm and the stem may not be completely closed, so that the drain valve hole is provided to discharge the foreign matter. When the pilot valve receives the pressure from the outlet and exceeds the set pressure, the inlet pressure enters the diaphragm through the connecting passage between the inlet and the diaphragm, and the pressure above and below the diaphragm is in equilibrium. And the spring is gradually closed, and when the disk is closed, when the pressure of the outlet is lower than the pilot valve set pressure, the pilot valve opens a passage connected to the outlet and the upper part of the diaphragm larger than the passage connected to the inlet and the upper part of the diaphragm. The upper pressure is lowered to the outlet pressure and the lower pressure of the diaphragm is higher than the upper pressure of the diaphragm, causing the disk to open quickly.

In this continuous operation, the diaphragm pressure reducing control valve is referred to as adjusting the opening degree of the disc so that the set pressure of the pilot valve is equal to the outlet pressure of the pressure reducing control valve.

As described above, the diaphragm pressure reducing control valve has a disc opening rate determined according to the flow rate of the outlet, which is a factor such as the time of dawn or season of using less water, which changes the amount of water used and restricts the amount of water used very little. When the valve is generated, the valve is normally operated at a disc opening rate of 10% or less, which causes cavitation, and the valve is pulsated repeatedly by opening and closing the disc.

As such, when the decompression control valve falls into such a state, the pulsation of the decompression control valve is alleviated by lowering the inlet pressure by adjusting the opening ratio of the dilution valve on the inlet side installed for maintenance of the decompression control valve. . Afterwards, when the water usage of the outlet increases, the operation of opening the water valve at the inlet side again to send sufficient flow rate is repeated, thereby increasing the human resource cost used for the maintenance of the pressure reducing valve.

Such a control valve is a known valve or a conventional pressure reducing control valve is a size of the pressure reducing control valve is determined by the pressure flowing into the inlet, the flow rate flowing into the outlet, and the pressure of the outlet to be set. A pressure reducing control valve is selected with a size of / 2.

When the valve is smaller than the selected size, the flow rate of the fluid flowing out of the outlet is insufficient, so that the pressure is kept below the set value of the decompression, and water does not come out from the side of the water actually used. On the contrary, if the valve is selected larger than the selected size, when the flow rate of the fluid flowing out to the outlet becomes small by using less water on the side using water, the valve is located at the opening of the disk where the cavitation occurs, causing cavitation and pulsation. Damage to the pipe is inevitable.

However, because the cavitation and pulsation may be restricted, the required flow rate of the water-use side cannot be limited, so even if cavitation or pulsation is concerned, the size of the pressure-reduced control valve may be sufficient to send the required flow rate to the water-side side. When less water is used on the water-use side, cavitation and pulsation occur frequently, causing damage to the valve or piping.

As such, the conventional cavitation control technology increases the total loss of the valve regardless of the opening ratio of the valve (when the cavitation occurs in the pressure reducing control valve, the loss of the inlet pressure is reduced by closing the inlet side valve. In order to control the cavitation by installing a perforated plate at the front end of the valve to impede the pressure loss that impedes the flow of the inlet, the maximum CV value (flow characteristic) of the valve itself is reduced and the appropriate valve size is selected. Even though the required flow rate is not supplied, a problem arises in selecting a larger valve.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art,

A conveying hole is formed so that fluid flows into the seat fixing plate, and a scrim plate having a lattice plate is formed at an outer circumference of the sheet circumference to reduce a conveying speed of the fluid conveyed through the conveying hole. During opening and closing, the fluid flows through the transfer hole and bumps through the scrim plate lattice to reduce the flow rate of the fluid, thereby preventing the cavitation and pulsation that frequently occur when the pressure reducing valve is operated at a low opening rate. It prevents noise and damage to the valve, thereby increasing the life and efficiency of the valve.It does not cause loss at high opening rate, which requires a large flow rate, so it does not increase the loss of the valve itself while suppressing the cavitation. As the loss occurs selectively, the maximum CV value of the valve itself remains unchanged. To the service at the same time as sending the cavitation and anti-pulsation pressure control valve for controlling the cavitation it is aimed.

In order to achieve the above object, the present invention is a flange is formed on both inlet and outlet so as to be connected between the tube and the tube, and the stepped projection is formed so as to support a disk for opening and closing the flow of fluid therein, the upper end is a stepped A body having a settled portion formed with a space such that the supported disk is driven up and down;

The inclined portion of the body is provided to be inclined to open and close between the step, the lower portion is in close contact between the step and the conical seat fixing plate is installed so that the fluid is smoothly transferred when opening, the one side surface of the seat fixing plate A conveying hole is formed which is introduced and conveyed, and is penetrated by the outer circumference of the seat fixing plate, and the scrim is reduced at the outer circumference of the seat fixing plate to prevent the cavitation and the pulsation phenomenon by reducing the conveying speed of the fluid transferred through the conveying hole. A disk on which a plate is formed;

A stem fixedly installed at the center of the disk and provided to be inclined at the settled portion, and configured to drive the disk up and down;

A diaphragm portion fixed to the upper end of the settled portion of the body, and having an upper end portion of the stem fixed therein to drive the stem up and down to drive the disk by a predetermined pressure; And a pressure reducing control valve for preventing pulsation.

As described above, the pressure reduction control valve for preventing cavitation and pulsation of the present invention is formed with a transfer hole so that the fluid flows into the seat fixing plate, the outer periphery of the seat fixing plate of the fluid transferred through the transfer hole Since a scrim plate having a lattice plate is formed on the outer circumference to reduce the feed speed, when the disc is opened and closed, the fluid flows through the transfer hole and bumps through the lattice plate of the scrim plate to reduce the flow rate of the fluid, thereby reducing the pressure. When the valve is operated at a low opening rate, it prevents frequent cavitation and pulsation, thereby preventing noise and valve breakage, thereby increasing the life and efficiency of the valve, and causing a loss at a high opening rate that requires a large flow rate. It does not increase the loss of the valve itself while suppressing the cavitation. By a selective loss occurs at rates up to the CV value of the valve itself has the effect of controlling the cavitation at the same time as there is no change sending a sufficient flow rate.

1 is a cross-sectional view showing a pressure reducing control valve for preventing closed cavitation and pulsation according to an embodiment of the present invention.
2 is a cross-sectional view showing a 15% open cavitation and pulsation prevention pressure reducing control valve according to an embodiment of the present invention,
3 is a cross-sectional view showing a pressure reducing control valve for preventing fully open cavitation and pulsation according to an embodiment of the present invention.
4 and 5 are exploded views showing the seat fixing plate of the disk according to an embodiment of the present invention,
Figure 6 is a development view showing a scrim plate according to an embodiment of the present invention,
7 is an exploded perspective view showing a scrim plate according to an embodiment of the present invention,
8 is a combined perspective view showing a scrim plate according to an embodiment of the present invention,
9 is an enlarged view illustrating a portion B of FIG. 3.

The present invention has the following features to achieve the above object.

The present invention is a flange is formed on both inlets and outlets so as to be connected between the pipe and the tube, the stepped protrusion is formed so as to support a disk for opening and closing the flow of fluid therein, the upper end of the disk is supported on the step A body having a settling portion formed with a space to be driven downward;

The inclined portion of the body is provided to be inclined to open and close between the step, the lower portion is in close contact between the step and the conical seat fixing plate is installed so that the fluid is smoothly transported when opening, the one end surface of the seat fixing plate A conveying hole is formed which is introduced and conveyed, and is penetrated by the outer circumference of the seat fixing plate, and the scrim is reduced at the outer circumference of the seat fixing plate to prevent the cavitation and the pulsation phenomenon by reducing the conveying speed of the fluid transferred through the conveying hole. A disk on which a plate is formed;

A stem fixedly installed at the center of the disk and provided to be inclined at the settled portion, and configured to drive the disk up and down;

It is fixed to the upper end of the settled portion of the body, the upper end of the stem is fixed to the inside to drive the stem up and down to drive the disk by a set pressure; characterized in that it comprises a.

The present invention having such characteristics can be more clearly described by the preferred embodiments thereof.

Before describing the various embodiments of the present invention in detail with reference to the accompanying drawings, it can be seen that the application is not limited to the details of the configuration and arrangement of the components described in the following detailed description or shown in the drawings. will be. The invention may be embodied and carried out in other embodiments and carried out in various ways. It should also be noted that the device or element orientation (e.g., "front," "back," "up," "down," "top," "bottom, Expressions and predicates used herein for terms such as "left," " right, "" lateral, " and the like are used merely to simplify the description of the present invention, Or that the element has to have a particular orientation. Also, terms such as " first "and" second "are used herein for the purpose of the description and the appended claims, and are not intended to indicate or imply their relative importance or purpose.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a cross-sectional view showing a closed cavitation and pulsation preventing pressure reducing control valve according to an embodiment of the present invention, Figure 2 is a 15% open cavitation and pulsation preventing pressure reducing control valve according to an embodiment of the present invention 3 is a cross-sectional view showing a fully open cavitation and pulsation-resistant pressure reducing control valve according to an embodiment of the present invention, Figures 4 and 5 is a seat fixing plate of the disk according to an embodiment of the present invention 6 is an exploded view showing a scrim plate according to an embodiment of the present invention, Figure 7 is an exploded perspective view showing a scrim plate according to an embodiment of the present invention, Figure 8 is an embodiment of the present invention Combination perspective view showing a scrim plate according to, Figure 9 is an enlarged view showing a portion B of FIG.

1 to 9, the pressure reduction control valve 100 for preventing cavitation and pulsation of the present invention includes a body 10, a disk 20, a stem 30, and a diaphragm portion. .

As shown in FIGS. 1 to 3, the body 10 has flanges 15 formed at both inlets 11 and outlets 12 so as to be connected between the tube and the tube, and an upper end portion of the body 10. Is formed into a space portion 14 is formed so that the disk 20 is driven up, down, and the settle portion 14 is formed to be inclined at the upper end of the body 10, the body 10 as a whole in cross-section " Y "form. At this time, the upper end of the settled portion 14 is hollow to communicate with the outside and the flange 15 is formed so that the partition 40 is coupled.

Here, the two stepped portions 13 protrude from each other so as to support the disk 20 for opening and closing the flow of fluid in the body 10, and the stepped portion 13 in contact with the disk 20. An elastic sheet 17 is further provided to prevent the disk 20 from being in close contact with each other and to be damaged by mutual friction. At this time, the fluid is transferred between the step (13).

In addition, the inlet 11 and the outlet 12 of the body 10 is formed with a discharge hole 16 penetrating the outside, respectively, the discharge hole 16 is connected to the pressure-reducing pilot valve 80 and the pipe In the present invention, the decompression pilot valve 80 is compared with the fluid pressure of the inlet port 11 to the fluid pressure of the outlet 12 by adjusting the opening and closing degree of the disk 20 in accordance with the fluid pressure of the outlet (12) A pressure reducing pilot valve 80 which allows a constant amount of fluid to flow at the outlet 12 at all times.

The pressure reducing pilot valve 80 is a well-known valve, and is connected to the pressure reducing pilot valve 80 at the outlet 16 of the inlet 11 and the outlet 16 of the outlet 12, respectively. In the valve 80, the fluid flows into the space portion 60 between the partition 40 and the cover 50 through the adjustment hole 52 of the cover 50.

1 to 9, the disk 20 is formed in a disc shape is provided inclined to the settled portion 14 of the body, opening and closing the fluid transported by opening and closing between the step (13), The disk sheet 22 is further installed at the portion of the disk 20 in contact with the step 13 so as to be in close contact with each other and to reduce mutual friction.

Here, the conical seat fixing plate 21 is coupled to the lower portion of the disk 20 so that the fluid introduced into the inlet 11 moves to the outlet 12 while hitting the seat fixing plate 21, and the fluid is transferred to the disk 20. Do not receive resistance when passing through.

That is, when the lower portion of the disk 20 is flattened as in the prior art, the fluid introduced into the inlet 11 hits the lower portion of the flat disk 20 and is subjected to resistance to the flow of the fluid, but in the present invention, the fluid is conical. The seat fixing plate 21 is moved while hitting so that the flow of the fluid is not resisted.

As such, the fluid flowing into the inlet 11 hits the conical seat fixing plate 21 and flows to the outlet 12 through the gap between the disk 20 and the step 13, but the fluid flows from the conical seat fixing plate 21. It can flow without being resisted.

And, one end surface of the seat fixing plate 21, that is, one end surface formed in a conical shape, as shown in Figure 4, a plurality of conveying holes 23 are formed so that the fluid is introduced into the conveying, the conveying hole 23 is a cross-section "a" It is bent in the form of the end portion penetrates through the outer periphery of the sheet fixing plate 21.

In addition, on the outer circumference of the seat fixing plate 21, as shown in FIGS. 1 to 3, the scrim plate 24 is provided to reduce the feeding speed of the fluid transferred through the transfer hole 23 to prevent cavitation. 7 and 8, the scrim plate 24 is formed by stacking a plurality of mutually, the insertion hole 25 in the central portion so as to communicate with the transfer hole 23 is provided on the outer periphery of the seat fixing plate 21 ) Is formed.

Here, one end surface of the scrim plate 24, as shown in Figures 5 to 8, a plurality of transfer holes 26 are formed so that the fluid transferred through the transfer hole 23 of the seat fixing plate 21 is transferred to one side The grating is formed.

As such, the scrim plate 24 is stacked in plural numbers, as shown in FIGS. 7 to 9, wherein the lattice plates are alternately stacked so that the fluid transferred through the transfer hole 23 of the sheet fixing plate 21 is transferred to the transfer hole 26. In Figure 9, as the upper, lower zigzag and left and right zigzag is transferred to the fluid hits the grid to reduce the flow rate. In this case, the transfer holes 26 are alternately stacked with each other so that the boundary surface of the upper scrim plate 24 is positioned in the transfer hole 26 of the scrim plate 24 stacked below.

As described above, the operation method in the installed state is briefly described. First, when the disc 20 is opened and closed about 15% as shown in FIG. 2 by the flow rate of the fluid in the state in which the disc 20 is closed, the disc ( As the gap is generated between the step 20 and the step 13, the vortices are generated by the rapid acceleration of the fluid, which causes cavitation, cavitation, and pulsation.

Here, the pulsation phenomenon is the degree of opening and closing of the disk 20 according to the flow rate of the outlet 12 in order to maintain a constant pressure of the outlet 12 irrespective of the change in the water pressure flowing into the inlet 11 Rate) of the inlet (11) when the inlet (11) water pressure is high and the outlet (12) use flow rate is small in the decompression control valve 100 is automatically adjusted to the set pressure of the pressure reducing pilot valve (80). Opening degree of the disk 20 is so close that the opening and closing degree of the disk 20 is almost closed to maintain the pressure set at 80, so that the gap between the disk sheet 22 and the body sheet 17 is narrowed and thus the orifice portion (not shown) is narrowed. In this case, the flow rate is increased, and the pressure is lowered, so that the disk 20 is lifted to move toward the body seat 17 due to the pressure difference between the bottom and the top of the disk 20. When the disk 20 is closed, the fluid flow is Suspended lift It disappears and the water pressure of the outflow pipe is lowered and the disk 20 of the pressure reducing control valve 100 is opened again by the pressure reducing pilot valve 80 and the pressure is lowered again by the high flow rate, so that the disk 20 is closed repeatedly. It is called a pulsation phenomenon.

Therefore, in the present invention, when the disk 20 is opened and closed by about 15% as shown in FIG. 2 by the flow velocity of the fluid in the state in which the disk 20 is closed, first, the fluid flows into the transfer hole 23 of the seat fixing plate 21. And bends up and down while passing through the lattice plate of the scrim plate 24. At this time, the flow velocity of the fluid is reduced by the loss generated every time the fluid rotates by 90 °, and the disk 20 is opened and closed, so that the step 13 Even if there is a gap between the gaps, the fluid velocity is reduced, so cavitation and pulsation do not occur.

1 to 3, the stem 30 is fixed to the central portion of the disk 20 is provided to be inclined to the settle portion 14, the stem 30 by the diaphragm 70 The disk 20 is driven up and down in accordance with the up and down driving.

Here, the stem 30 has an end portion (the opposite side of the disk 20) is provided in the space portion 60 between the cover 50 and the partition 40 through the central portion of the partition 40, the end The diaphragm 70 is connected to the part.

And, the outer circumference of the stem 30 is provided with a spring 31, the spring 31 is supported at both ends on the upper surface of the disk 20 and the lower surface of the partition 40 to the pressure of the fluid The pressure is applied to the disk 20 driven upward.

1 to 3, the diaphragm portion is fixed to the upper end of the settled portion 14 of the body 10, the upper end portion of the stem 30 is fixed inside to raise the stem 30, The partition 40, the cover 50, and the diaphragm 70 are comprised so that it may drive downward and drive the disc 20 by a set pressure.

1 to 3, the partition 40 is fixed to the flange 15 of the settled portion 14 by fixing members such as bolts (not shown), and the stem 30 is partitioned. It penetrates the central portion of the 40, and the center portion of the lower surface protrudes downward so that the pierced stem 30 is supported by the partition 40, and is formed in a cross-sectional "∪" shape.

Here, the stem bush 41 is further installed between the stem 30 and the protruding center to reduce the friction caused by the stem 30 in the up and down driving.

In addition, the lower surface of the partition 40, that is, the lower surface positioned in the settled portion 14, has a fluid hole 42 formed therethrough so that the fluid of the outlet 12 may be introduced therein, and a drain may be provided on the side surface of the partition 40. The diaphragm is formed by a foreign matter that is formed in the hole 43 and is filled in the space 60 between the partition 40 and the cover 50 through the drain hole 43, that is, the foreign matter introduced under the diaphragm 70. If the 70 is not in close contact with the lower portion of the disk 20 is connected to the diaphragm 70 and the stem 30 is not completely closed to discharge the foreign matter.

1 to 3, the cover 50 is fixed to the upper end of the partition 40 is formed in a "∩" shape in cross section so that the space portion 60 is formed between the partition 40, The stopper 51 is further installed in the center to check the internal space 60.

Here, the control hole 52 is formed on the upper side of the cover 50 so that the fluid flows into the space 60 from the pressure reducing pilot valves 80 and 90, and one end of the upper side of the cover 50. An air hole 53 is formed in the same manner as the partition 40, and the air filled in the space 60 between the partition 40 and the cover 50 can be effectively discharged through the air hole 53. The air hole 53 may be prevented or opened using a fixing screw (not shown).

As shown in FIGS. 1 to 3, the diaphragm 70 is provided in the space portion 60 between the partition 40 and the cover 50 to elastically drive the stem 30 while moving up and down elastically. By driving up and down, it is fixed to the upper end of the stem 30, both ends of the diaphragm 70 is fixed between the partition 40 and the cover 50 so that the stem 30 is diaphragm Is fixedly penetrated through the central portion of the 70 is to be driven up and down elastically.

Here, the diaphragm plate 71 is further provided on the upper and lower surfaces of the diaphragm 70 so that the diaphragm 70 is fixed to the stem 30, and the center portion of the diaphragm plate 71 is attached to the stem 30. ) Is penetrated and attached.

In addition, the diaphragm 70 will be driven up and down elastically in the form of "∪" and "∩" in cross section with reference to FIGS. 1 to 3.

10 body 20 disk
30: stem 40: partition
50: cover 60: space
70: diaphragm 80: pressure reducing pilot valve
100: pressure reducing control valve

Claims (4)

Flange 15 is formed at both inlet 11 and outlet 12 so as to be connected between the tube and the tube, and the stepped portion 13 protrudes to support the disk 20 for opening and closing the flow of fluid therein. The upper end portion includes a body 10 having a settled portion 14 formed with a space such that the disk 20 supported by the step 13 is driven up and down;
The inclined portion of the body 10 is provided to be inclined to open and close between the step (13), the lower portion of the seat fixing plate 21 of the conical form so that the fluid is smoothly transported during opening while in close contact between the step (13). It is installed, one end surface of the seat fixing plate 21 is formed with a conveying hole 23 through which the fluid flows into the outer periphery of the sheet fixing plate 21, the outer periphery of the sheet fixing plate 21 is transferred A disk 20 on which a scrim plate 24 is formed to reduce the conveying speed of the fluid transferred through the hole 23 to prevent cavitation and pulsation;
A stem 30 fixedly installed at a center portion of the disk 20 to be inclined at the settled portion 14 to drive the disk 20 up and down;
It is fixed to the upper end portion 14 of the body 10, the upper end of the stem 30 is fixed therein to drive the stem 30 up and down to drive the disk 20 by the set pressure It is configured to include; diaphragm portion,
The scrim plate 24 is formed by stacking a plurality of mutually, the insertion hole 25 is formed in the center to communicate with the transfer hole 23 is provided on the outer periphery of the sheet fixing plate 21, the sheet fixing plate 21 Pressure reducing control valve for preventing cavitation and pulsation, characterized in that the grating plate formed of a plurality of transfer holes 26 is formed on one end surface so that the fluid transferred through the transfer hole (23) of one side is transferred to one side.
The method of claim 1,
The scrim plate 24 is a plurality of stacked mutually, the lattice plate is stacked alternately and the fluid transferred through the transfer hole 23 of the sheet fixing plate 21 is transferred to the zigzag in the transfer hole 26 to reduce the flow rate Pressure reducing control valve for preventing cavitation and pulsation, characterized in that to prevent cavitation and pulsation.
According to claim 1, The diaphragm portion,
It is formed in a cross-sectional "∪" shape to be fixed to the upper end portion 14 of the body 10, the stem 30 penetrates the center to the lower side to support the stem 30 when driving up and down A partition 40 between the stem 30 and the protruding center portion, wherein the stem bush 41 is further installed to reduce friction due to the up and down driving of the stem 30;
A cover 50 which is fixed to an upper end of the partition 40 and is formed in a “∩” shape in cross section so that a space 60 is formed between the partition 40;
It is provided in the space portion 60 between the partition 40 and the cover 50 and is fixed to the upper end of the stem 30 to drive the stem 30 up and down, both ends of the partition 40 And a diaphragm 70 fixed between the cover 50 and driven up and down in a central portion where the stem 30 is fixed;
Pressure reduction control valve for cavitation and pulsation prevention, characterized in that comprising a.
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