KR100591291B1 - Backflow preventer - Google Patents

Abstract

The present invention relates to a backflow preventer, and more particularly, is installed in a pipe system in which fluid flows, and quickly discharges the fluid introduced due to backflow to the outside, and the opening and closing action of the relief valve is incomplete due to foreign matter. And a backflow preventer capable of selecting and installing any one of a plug member and a relief valve according to the fluid flowing in the piping system. To this end, the present invention has a backflow preventer, a hollow flow passage connecting the inlet and the outlet is formed, the case is formed between the inlet and the outlet outlet; A first check valve installed between the inlet and the outlet to selectively open and close the flow path to prevent backflow of the fluid; And a second check valve installed between the outlet port and the outlet port to selectively open and close the flow path to prevent backflow of the fluid, and the case includes a plug member for sealing the outlet port or a fluid introduced between the first and second check valves. One of the relief valve selectively discharged through may be installed.

Valve, Backflow, Check Valve, Back Pressure, Reverse Efund

Description

Backflow preventer

1 is a cross-sectional view showing a diaphragm type backflow preventer according to the prior art.

Figure 2 is a cross-sectional view showing a non-return device according to the prior art, showing the operation in the water supply state.

3 is a cross-sectional view showing that the backflow prevention device of FIG. 2 operates in a back pressure or a backfill state.

4 is a cross-sectional view showing a backflow preventer according to a preferred embodiment of the present invention, showing that the stopper member is installed in the outlet.

FIG. 5 is a cross-sectional view illustrating a non-return checker according to a preferred embodiment of the present invention, in which the first and second check valves and the relief valve installed at the outlet are operated in a water flow state.

6 is a cross-sectional view showing that the backflow preventer of FIG. 5 operates in a back pressure or a reverse punch state.

FIG. 7 is a detailed cross-sectional view of portion A of FIG. 5.

<Explanation of symbols for the main parts of the drawings>

10: diaphragm type backflow preventer 20: backflow preventer

30: case 50: stopper member

60: relief valve 100, 200: backflow preventer

The present invention relates to a backflow preventer, and more particularly, is installed in a pipe system in which fluid flows, and quickly discharges the fluid introduced due to backflow to the outside, and the opening and closing action of the relief valve is incomplete due to foreign matter. And a backflow preventer capable of selecting and installing any one of a plug member and a relief valve according to the fluid flowing in the piping system.

In general, the water supply system in the water supply system has been widely used as a direct water supply system in which a water pipe is directly connected to a water supply pipe, and a direct pressure system in which water is supplied directly from a water supply drain pipe to a water supply without passing through a water tank in a building.

In the direct water supply method and the direct pressure method, it is important to prevent backflow because water is directly supplied to the water supply pipe or the water supply line. As a conventional means of preventing the backflow of the fluid, a check valve is used in which the fluid flows in only one direction and the valve is automatically closed during the backflow.

The check valve has no difficulty in blocking back flow in a water supply state or a normal stop state in which a fluid flows normally inside a pipeline, but there is a limit in preventing a back flow caused by a back pressure and a backfill. In order to solve this problem, a double check valve has been developed. However, foreign matter is caught in the valve seat or the valve itself is not completely closed due to damage to the valve itself.

In order to solve this problem, the diaphragm type backflow preventer 10 shown in FIG. 1 has been proposed. The diaphragm type backflow preventer 10 includes a lift type first check valve 13 and a second check valve 14 installed so as to operate independently upstream and downstream of the flow paths 12a, 12b, and 12c, and And a pressure regulating mechanism 16 provided between the first and second check valves 13 and 14. The pressure adjusting mechanism 16 includes a bypass flow passage 16a, a diaphragm 16b, and a relief valve 17.

The relief valve 17 is installed to penetrate the diaphragm 16b, one end of which is connected to the disk 17a, and the other end of which opens and closes a rod member 17b and an outlet 16d provided in the air chamber 16c. The disk 17a and the spring 17c provided in the said disk 17a are included. The air chamber 16c is installed to prevent the relief valve 17 from being opened rapidly.

That is, the relief valve 17 has the pressure P _a of the upstream side 12a, the pressure P _b of the intermediate chamber 12b, the elastic force of the spring 17c, and the weight of the relief valve 17. It moves up and down and selectively opens and closes the outlet 16d.

However, when the rod member 17b moves upward to open the outlet 16d, the pressure in the air chamber 16c increases to act in the direction of closing the outlet 16d. In addition, when the rod member 17b moves downward to seal the outlet 16d, the pressure in the air chamber 16c decreases and acts in the direction of opening the outlet 16d. Due to the action of the pressure in the air chamber 16c, there is a problem that the reaction speed of the relief valve 17 is slowed. In addition, a chattering phenomenon may occur in which the closing and opening of the outlet 16d are repeated.

In addition, since the rod member 17b is installed on the flow path of the diaphragm type backflow preventer 10, the flow of fluid is not smooth and vortices are likely to occur. That is, there is a problem that a large pressure loss of the fluid occurs.

The first check valve 13 seals the flow path when the pressure difference P _a -P _b between the upstream side 12a and the intermediate chamber 12b is equal to or less than a predetermined value, and opens when the predetermined value exceeds the predetermined value.

Meanwhile, the Korean Water Supply Association requires that the relief valve 17 be opened only when the differential pressure P _a -P _b is equal to or less than a predetermined value (0.14 kgf / cm 2) to discharge the fluid in the intermediate chamber 12b to the outside. Doing. However, in the diaphragm type backflow preventer 10, the relief valve 17 opens at a differential pressure of a predetermined value (0.14 kgf / cm 2) or more due to a structural problem, and the differential pressure is set to a predetermined value as the relief valve 17 opens. 0.14 kgf / cm 2). Therefore, even when the normal water flow state, that is, when the pressure difference between the upstream side 12a and the intermediate chamber 12b exceeds a predetermined value (0.14 kgf / cm 2), the relief valve 17 is opened so that the fluid is discharged to the outside. have.

In order to solve these problems, a backflow prevention device has been proposed in which an inner cylinder installed inside a pipe slides along a flow direction of a fluid and opens and closes a valve hole. The backflow prevention device is disclosed in Korean Unexamined Patent Publication No. 2001-0014725.

Figure 2 is a cross-sectional view showing the reverse flow prevention device, a view showing the operation in the water supply state, Figure 3 is a cross-sectional view showing the operation in the back pressure or a back-filled state.

2 and 3, the backflow prevention device 20 is slidably installed with respect to the trauma 21 and the sliding surface 22 of the trauma 21 so that the valve hole 23 can be opened. And an inner cylinder 24 for selectively opening and closing, and first and second check valves 25 and 26 for opening and closing the flow path in accordance with the flow direction of the fluid.

When the fluid flows in the forward direction, the first and second check valves 25 and 26 are opened, and the inner cylinder 24 is the valve seat because the pressure at the inlet port 27a is greater than the pressure in the intermediate chamber 27b. It comes in close contact with 21a to seal the valve hole 23.

When the fluid flows back, the first and second check valves 25 and 26 are sealed, and since the pressure in the intermediate chamber 27b is greater than the pressure in the inlet port 27a, the inner cylinder 24 is inlet port 27a. The valve hole 23 is opened by sliding toward the side. Therefore, the fluid flowing into the intermediate chamber 27b due to the backflow of the fluid is discharged to the outside through the valve hole 23.

The backflow prevention device 20 can prevent the chattering phenomenon caused by the pressure change in the air chamber (16c of FIG. 1), and the reaction rate for the back pressure or the reverse-fund can be faster than the diaphragm type backflow preventer 10. The advantage is that you can. In addition, since there is no member that prevents the flow of the fluid, such as the rod member (17b of FIG. 1), the pressure drop of the fluid can be reduced. In addition, since the valve hole 23 is opened only when the pressure difference between the inlet port 27a and the intermediate chamber 27b is equal to or less than a predetermined value, the loss of the fluid can be prevented.

However, the backflow prevention device 20 is not sliding smoothly of the inner cylinder 24 when foreign matter is inserted between the sliding surface 22 and the inner cylinder 24. That is, a problem may arise that the inner cylinder 24 cannot fully open and close the valve hole 23.

In addition, in order for the inner cylinder 24 to open the valve hole 23 by the occurrence of a back pressure or a reverse-funded phenomenon, the first check valve 25 slides toward the inlet port 27a to seal the flow path and at the same time the inner cylinder 24. Should slide toward the inlet 27a to open the valve hole 23. At this time, friction occurs between the sliding surface 22 and the inner cylinder 24, and friction also occurs between the valve shafts 25a and 26a and the valve guides 25b and 26b. That is, the opening of the valve hole 23 is delayed due to the friction at two places, so that the fluid is not discharged quickly. This also occurs when the fluid flows back in the forward direction and the valve hole 23 is closed.

On the other hand, it is economically very important to install a suitable backflow preventer depending on the fluid flowing inside the piping system. That is, in a piping system in which a relatively low-risk fluid, such as a beverage, flows, employing a simple backflow preventer having first and second check valves is an expensive backflow including both a relief valve and a first and second check valves. It is more economically advantageous than employing a preventer. On the other hand, it is important to reliably discharge the backflowed fluid by using a backflow preventer including a relief valve and a first and a second check valve in a piping system in which hazardous substances with a high risk flow.

In view of this point, the diaphragm type backflow preventer 10 and the backflow preventer 20 may include first and second check valves 13, 14, 25, 26, and intermediate chambers 12b and 27b. Since it is provided with a relief valve 17 or the inner cylinder 24 for discharging the fluid introduced into the), there is a problem in that it is advantageous to discharge the backflowed fluid to the outside, but economically disadvantageous.

The present invention has been made to solve the above problems, and an object thereof is to provide a backflow preventer capable of quickly discharging the fluid introduced between the first and second check valves due to the backflow.

Another object of the present invention to provide a backflow preventer that can prevent the incomplete opening and closing of the relief valve due to foreign matter.

It is still another object of the present invention to properly modify and use a simple backflow preventer having only the first and second check valves or a backflow preventer having both the relief valve and the first and second check valves depending on the fluid flowing in the piping system. To provide a backflow preventer that can be.

In order to achieve the above object, the backflow prevention device includes a case in which a hollow flow passage connecting the inlet and the outlet is formed, and the outlet is formed between the inlet and the outlet; A first check valve installed between the inlet and the outlet to selectively open and close the flow path to prevent backflow of the fluid; And a second check valve installed between the outlet port and the outlet port to selectively open and close the flow path to prevent backflow of the fluid, wherein the case includes a closure member or the first and second checks to seal the outlet port. Any one of the relief valve for selectively discharging the fluid introduced between the valves through the outlet can be installed.

Preferably, the relief valve, the valve body is detachably installed in the discharge port, the side of the valve body is formed with a discharge hole for discharging the fluid to the outside; It is installed inside the valve body, the lower surface of the plunge of a predetermined length is formed protruding, the space between the pressure of the first chamber and the first and second check valve space between the first check valve and the inlet A disk for vertically reciprocating according to the pressure of the second chamber, and discharging the fluid introduced into the second chamber to the outside by moving downward to open the discharge hole when Equation 1 is satisfied; An elastic member installed to be connected to the disk to elastically bias the disk downward; And a cover installed at a lower end of the valve body and having a mating groove formed therein to be coupled with the plunge such that the plunge is inserted and sealed, and having a communication hole communicating with the first chamber. The vertical reciprocating movement is performed while the plunge is inserted into the mating groove.

Equation 1

P ₁ -P ₂ ≤ △ P

However, P ₁ : pressure of the first chamber

P ₂ : pressure of the second chamber

△ P : Predetermined pressure

More preferably, the backflow preventer has a disk and an elastic member satisfying the following expressions 2,3.

Equation 2

d ² _DiscU + d ² _pl -d ² _DiscD = 0

Expression 3

However, in the formula 2, 3,

d _DiscU : _diameter of the upper surface of the disk to which the pressure P ₂ of the second chamber acts

d _pl : diameter of the plunge

d _DiscD : diameter of the lower surface of the disc

F: elastic force of the elastic member

P _h : pressure inside the matching groove

W: weight of the disk

In addition, the forming groove is formed to communicate with the outside, the pressure (P _h ) acting on the plunge is preferably atmospheric pressure.

In addition, the communication port is in communication with the first chamber by a predetermined connection pipe, at least one of both ends of the connection pipe, and the upper end of the valve body is preferably provided with a mesh to prevent the inflow of foreign matter.

Here, it is preferable that the closure member and the relief valve are detachably attached to the case, respectively.

Hereinafter, a backflow preventer according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. 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.

Figure 4 is a cross-sectional view showing a backflow preventer according to a preferred embodiment of the present invention, showing that the plug member is installed in the outlet.

Referring to FIG. 4, the backflow preventer 100 includes a case 30 and first and second check valves 42 and 46 installed in the case 30 to prevent backflow of the fluid. A closure member 50 for sealing the outlet 32 formed between the two check valves 42 and 46 is provided.

A hollow flow path is formed in the case 30. The fluid is introduced through the inlet 33a and then discharged through the outlet 33c via the flow path. The flow path is divided into first, second and third chambers 34 and 35 and 36 by first and second check valves 42 and 46, respectively. That is, the flow path between the inlet 33a and the first check valve 42 is divided into the first chamber 34, and the flow path between the first check valve 42 and the second check valve 46 is the second chamber. And a flow path between the second check valve 46 and the outlet 33c is partitioned into the third chamber 36.

The second chamber 35 is formed with an outlet 32 for discharging the fluid introduced due to the reverse flow. Preferably, the outlet 32 is formed on the lower surface of the second chamber 35.

The first and second check valves 42 and 46 open and close the flow path according to the flow direction of the fluid to prevent backflow. The first and second check valves 42 and 46 are provided on the seat rings 42a and 46a and the seat rings 42a and 46a provided on the flow path to open and close the flow path according to the flow direction of the fluid. 42b and 46b, and elastic means 47 for providing an elastic force to the valve bodies 42b and 46b.

The first and second check valves 42 and 46 shown in dashed lines in FIG. 4 indicate that the valve bodies 42b and 46b are opened in the water passage state. Since the first and second check valves 42 and 46 are generally widely used, a detailed description thereof will be omitted.

The first and second check valves 42 and 46 are designed to close the flow path when the pressures P ₁ and P _{2 of the first and} second chambers 34 and 35 satisfy the following equation.

P ₁ -P ₂ ≤ △ P

However, P ₁ : pressure of the first chamber 34

P ₂ : pressure in the second chamber 35

    ΔP: predetermined pressure

That is, the pressure (P ₁₎ of the first and second chambers 34, 35, the differential pressure is the predetermined pressure (△ P) equal to or less than the pressure in the second chamber 35 of the (P ₂₎ a first chamber (34) If larger, the flow path is sealed. Here, by adjusting the elastic force of the elastic means 47, the flow path is closed when the differential pressure of the first and second chambers 34 and 35 is equal to or less than the predetermined pressure? P.

The closure member 50 is installed in the case 30 to seal the outlet 32. The closure member 50 is detachably installed in the case 30 so that the plug member 50 can be replaced with a relief valve to be described later. Preferably, a screw thread (not shown) is formed on the inner circumferential surface of the closure member 50, and a screw thread (not shown) is formed on the case 30 to match the screw thread. That is, the closure member 50 is screwed to the case 30.

Although FIG. 4 shows that the plug member 50 is installed in the outlet 32, the relief valve 60 may be installed as shown in FIG. That is, one of the plug member 50 and the relief valve 60 is provided in the discharge port 32. In a piping system in which a relatively low-risk fluid flows, such as drinking water, employing a backflow preventer 100 that seals the outlet 32 by using the cap member 50 is expensive because the relief valve 60 is installed in the outlet 32. It is more economically advantageous than employing a high flow rate backflow preventer 200. On the other hand, it is important to reliably drain the fluid flowing into the second chamber 35 using the relief valve 60 in the piping system through which the hazardous substances with a high risk flow. This point has been described above.

The relief valve 60 is provided with a valve body 62 installed at the outlet 32, a disk 63 installed inside the valve body 62 to reciprocate up and down, and an elastic force to the disk 63. It provides an elastic member 64 and a cover 67 provided on the lower end of the valve body 62.

The valve body 62 is detachably installed at the outlet 32. The valve body 62 has a hollow portion communicating with the outlet 32 in the longitudinal direction. The disk 63 is installed in the hollow portion. A jaw 62a protruding toward the hollow portion is formed inside the valve body 62 to serve as a stopper when the disk 63 moves upward. In addition, a discharge hole 62b for discharging the fluid introduced into the second chamber 35 is formed at the side of the valve body 62. The discharge hole 62b is opened when the disk 63 moves downward, and is formed at a position closed by the disk 63 when the disk 63 recovers to its original position.

Preferably, a net (not shown) is installed at the upper end of the valve body 62. The mesh prevents foreign matter from flowing into the second chamber 35 to smoothly move up and down the disk 63.

The disk 63 is installed in the valve body 62 and is disposed between the jaw 62a and the cover 67 according to the pressure P ₁ (P ₂ ) of the _first and second chambers 34 and 35. Move. The lower surface of the disk 63 is formed by protruding the plunge 63a for mating with the fitting groove 67a of the cover 67.

The elastic member 64 is installed such that one end thereof is connected to the disk 63 and the other end thereof is connected to the valve body 62. The elastic member 64 provides an elastic force for biasing the disk 63 downward.

The cover 67 is installed at the lower end of the valve body 62, and includes a mating groove 67a for mating with the plunge 63a and a communication port 67b for communicating with the first chamber 34.

The fitting groove 67a is closed due to the insertion of the plunge 63a. The disk 63 moves up and down with the plunge 63a inserted into the mating groove 67a.

Preferably, the matching groove 67a is formed to communicate with the outside. In this case, an external atmospheric pressure P _atm acts on the lower surface of the plunge 63a.

The communication port 67b communicates with the first chamber 34 by a connecting pipe 68. By the connecting pipe 68, the pressure P ₁ of the first chamber 34 and the pressure under the disk 63 become equal to each other. Preferably, a portion of both ends of the connecting pipe 68 is connected to the first chamber 34 is provided with a net (not shown). The net prevents foreign matter from entering the connecting pipe 68 to smoothly move up and down the disk 63. Of course, the mesh may be installed in the communication port (67b).

As such, the backflow preventer 200 is not provided with an air chamber (16c in FIG. 1), and only the friction between the disk 63 and the valve body 62 is present when the discharge hole 62b is opened. The fluid introduced into the (35) can be quickly discharged to the outside.

When the relief valve 60 satisfies Equation 1, the relief valve 60 discharges the fluid introduced into the second chamber 35 to the outside by opening the discharge hole 62b. That is, the area of the upper surface of the disk 63 on which the pressure P ₂ of the second chamber 35 acts, the area of the lower surface of the disk 63 on which the pressure P ₁ of the first chamber 34 acts, and By adjusting the elastic force of the elastic member 64, when the equation 1 is satisfied, the disk 63 moves downward to open the discharge hole 62b.

If this is described in more detail as follows.

6 and 7, the conditions under which the downward force to open the discharge hole 62b and the upward force to seal the discharge hole 62b are balanced as follows.

A _DiscU P ₂ + F + W = A _DiscD P ₁ + A _Pl P _h ......... (ⅰ)

In the formula (i) above,

A _DiscU : Area where the pressure P ₂ of the second chamber 35 acts on the upper surface of the disc 63.

....................(ⅱ)

..... (ii)

d _DiscU : _Diameter of the upper surface of the disc 63 to which the pressure P ₂ of the second chamber 35 acts. In other words, the inner diameter of the portion of the jaw 62a

F: Elastic force of the elastic member 64

W: weight of the disk 63

A _DiscD : Area in which the pressure P ₁ of the first chamber 34 acts

....................(ⅲ)

.......... (ⅲ)

d _DiscD : Diameter of the lower surface of the disc 63, d _pl : Diameter of the plunge 63a

....................(ⅳ)A _Pl : Diameter of Plunge 63a

.......... (ⅳ)

P _h : Pressure inside the mating groove 67a

The pressure P _h of the mating groove 67a becomes the atmospheric pressure P _atm when the mating groove 67a communicates with the outside.

Substituting Eq. (Ii), (iii), (iv) and Equation 1 into Equation (i) above,

......... (ⅴ)

Becomes

At this time, the following equations ( ₂ ) and ( ₃ ) must be satisfied in order for the expression (v) to be satisfied regardless of the change in the pressure P ₁ of the first chamber 34.

In other words, by installing the disk 63 and the elastic member (64) satisfy the following formula 2, 3 in the relief valve 60, a second, regardless of the change in pressure (P ₁₎ of the first chamber 34 is 1, When the differential pressure of the two chambers 34 and 35 is ΔP or less, the disc 63 moves downward to open the discharge hole 62b. In other words, when the differential pressures P ₁ -P _{2 of the first and} second chambers 34 and 35 are ΔP or less, the first and second check valves 42 and 46 are sealed and at the same time the discharge holes 62b. This is opened so that the fluid in the second chamber 35 is discharged to the outside. Therefore, even in the normal water flow state, the discharge hole 62b is opened, thereby solving the problem of the fluid being discharged to the outside. The disk 63 moved down in FIGS. 6 and 7 is indicated by the dotted line.

As such, the backflow preventer 200 according to the preferred embodiment of the present invention includes dual safety devices of the first and second check valves 42 and 46 and the relief valve 60. As a result, even when the first and second check valves 42 and 46 do not operate normally at the time of the back flow, the fluid flowed back through the discharge hole 62b is discharged to the outside, thereby preventing the risk of the back flow of the fluid. have. The valve body 42b shown in broken lines in FIG. 6 indicates that the first check valve 42 is not completely sealed due to the adhesion of foreign matter.

Preferably, ΔP in Equations 1 and 3 is 0.14kgf / cm 2. This is to satisfy the standards of Korea Waterworks Association. That is, the pressure P ₂ of the second chamber 35 is greater than the pressure P ₁ of the first chamber 34 or the differential pressure P ₁ -P _{2 of the first and} second chambers 34 and 35. ) 0.14kgf / ㎠ In the following cases, the flow path is sealed by the first and second check valves 42 and 46, and the disc 63 moves downward to open the discharge hole 62b.

Then, the operation of the backflow preventer 100 and 200 according to the preferred embodiment of the present invention will be described. The backflow preventer 100 and 200 may be used as the backflow preventer 100 having only the first and second check valves 42 and 46 by closing the outlet 32 using the cap member 50. Instead of the plug member 50, the relief valve 60 may be installed at the outlet 32 to be used as the backflow preventer 200 having both the first and second check valves 42 and 46 and the relief valve 60. have.

First, as shown in FIG. 4, the backflow preventer 100 provided with the plug member 50 at the outlet 32 will be described.

The closure member 50 simply serves to seal the outlet 32. Therefore, P ₁ -P ₂ > ΔP If is When the first and second check valves 42 and 46 are opened so that the fluid flows from the inlet 33a to the outlet 33c, and Equation 1 is satisfied, that is, P ₁ -P ₂ ? The first and second check valves 42 and 46 are sealed to block backflow of the fluid.

The backflow preventer 100 may be economically used in a piping system through which a low risk fluid, such as a beverage, flows.

On the contrary, as shown in FIGS. 5 to 7, the non-return valve 200 having the relief valve 60 installed in the outlet 32 instead of the plug member 50 prevents the back flow of the fluid in the piping system through which the high-risk fluid flows. It can be used effectively to prevent. Referring to the operation of the backflow preventer 200 is as follows.

First, when P ₁ -P ₂ > ΔP, the first and second check valves 42 and 46 are opened so that fluid flows from the inlet 33a to the outlet 33c, where Equation 1 is satisfied. When P ₁ -P ₂ ≤ ΔP, the first and second check valves 42 and 46 are sealed. That is, the relief valve 60 opens the discharge hole 62b only when the differential pressure of the first and second chambers 34 and 35 is lower than or equal to the predetermined pressure ΔP. Discharge. Therefore, in the normal water supply state, the discharge hole 62b is opened to solve the problem of the fluid being discharged to the outside.

In the case of P ₁ -P ₂ ≤ΔP, if foreign matter adheres to the valve bodies 42b and 46b or the seat rings 42a and 46a, or foreign matter enters the shaft of the valve bodies 42b and 46b. In some cases, the first and second check valves 42 and 46 cannot completely seal the flow path.

At this time, when designing the disc 63 and the elastic member 64 of the relief valve 60 so as to satisfy the following formula 2,3, P ₁ -P ₂ ≤ △ regardless of the change of the P ₁ P when the disk The 63 moves downward to open the discharge hole 62b. That is, the fluid introduced into the second chamber 35 is discharged to the outside through the discharge hole 62b.

As described above, the backflow preventer according to the present invention has the following effects.

First, the fluid flowing into the second chamber due to the backflow can be quickly discharged to the outside.

Second, the foreign matter can prevent the operation of the relief valve, that is, incomplete opening and closing of the discharge hole.

Third, the installation cost of the valve piping system can be reduced by selecting and installing any one of the plug member and the relief valve according to the fluid flowing inside the piping system.

Fourth, it is possible to prevent the loss of fluid by opening the discharge hole only when the pressure difference between the first chamber and the second chamber is less than or equal to a predetermined value.

Claims (6)

delete A case in which a hollow flow passage connecting the inlet and the outlet is formed, and the outlet is formed between the inlet and the outlet; A first check valve installed between the inlet and the outlet to selectively open and close the flow path to prevent backflow of the fluid; And And a second check valve disposed between the outlet port and the outlet port to selectively open and close the flow path to prevent backflow of the fluid. The case is provided with a relief valve for selectively discharging the fluid introduced between the first and second check valve through the outlet, The relief valve, A valve body detachably installed at the discharge port and having a discharge hole formed at a side thereof to discharge the fluid to the outside; It is installed inside the valve body, the lower surface of the plunge of a predetermined length is formed protruding, the space between the pressure of the first chamber and the first and second check valve space between the first check valve and the inlet A disk for vertically reciprocating according to the pressure of the second chamber, and discharging the fluid introduced into the second chamber to the outside by moving downward to open the discharge hole when Equation 1 is satisfied; An elastic member installed to be connected to the disk to elastically bias the disk downward; And, A cover formed at a lower end of the valve body and configured to engage with the plunger so that the plunger is inserted and sealed, and formed with a communication port communicating with the first chamber. And a plunger is inserted into the mating groove to vertically reciprocate. Equation 1 P ₁ -P ₂ ≤ △ P However, P ₁ : pressure of the first chamber P ₂ : pressure of the second chamber     ΔP: predetermined pressure The method of claim 2, And the disk and the elastic member satisfy the following expressions 2 and 3. Equation 2

Expression 3

However, in the above formula 2,3 d _DiscU : _diameter of the upper surface of the disk to which the pressure P ₂ of the second chamber acts d _pl : diameter of the plunge d _DiscD : diameter of the lower surface of the disc F: elastic force of the elastic member P _h : pressure inside the matching groove W: weight of the disk The method of claim 3, The forming groove is formed so as to communicate with the outside, the pressure (P _h ) acting on the plunge is atmospheric pressure characterized in that the atmospheric pressure. The method of claim 4, wherein The communication port is in communication with the first chamber by a predetermined connecting pipe, At least one of both ends of the connecting pipe, and the top of the valve body, the backflow preventer, characterized in that the mesh is installed to prevent the inflow of this material. The method according to any one of claims 2 to 5, The relief valve is a backflow preventer, characterized in that each detachably installed in the case.

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