Patent Application
20180142808
The present invention relates to a water piping system. More particularly, it relates to a water piping system that can alleviate water hammer due to slamming of a check valve by reducing the pressure difference between the front end and the rear end of the check valve by supplying some of fluid at the rear side of the check valve to the front side of the check valve when a pump is stopped, and a method of controlling the water piping system.
In general, when a pump is suddenly stopped or a valve is suddenly closed in a water piping system, a transient condition in which the flow rate of fluid rapidly changes is generated, and this phenomenon is called water hammer. Due to the water hammer, the pressure in the pipe rapidly increases or the pressure in the pipe drops under the saturation vapor pressure of water and vapor is produced, and then the pipe line may be broken or damaged by shock waves in the process of column separation and return.
For example, a common piping system shown in
In this water piping system, when the pump 2 suddenly stops, the fluid flowing through the main pipe 10 temporarily keeps flowing through the main pipe 10 in the main flow direction by inertia, but the discharge amount from the pump 2 rapidly decreases. Accordingly, negative pressure is generated at the rear side (outlet port) of the pump, vapor cavity is generated in the pipe, and the fluid flows backward, whereby the vapor cavity breaks and large pressure waves are generated. Therefore, the main pipe 10 and the pump 2 may be broken. Accordingly, a pressure tank 5 is provided to alleviate water hammer due to vapor cavity.
Meanwhile, water hammer may be generated by slamming due to sudden closing of the check valve 4. Slamming is a phenomenon in which, as shown in
A pressure change (ΔH) due to slamming of a check valve, as can be seen from the following Equation (1), is determined by a backflow speed change (ΔV) of fluid at the last moment when the disc 4a of the check valve 4 is closed.
ΔH=(C/g)ΔV Equation (1)
(where ΔH: pressure change (shock wave), C: propagation speed of shock wave based on properties of material of pipe, g: acceleration of gravity, ΔV: backflow speed change of fluid)
In detail, when the discharge amount rapidly decreases due to sudden stopping of the pump 2, the fluid that is flowing starts to flow backward after a period of time, so the disc 4a of the check valve 4 is closed. At the moment when the disc 4a is closed, the flow speed of the fluid is rapidly changed (the disc is rapidly closed), so negative pressure or low pressure is generated at the front end (primary side) of the check valve 4, while a rising pressure wave (slamming) are generated at the rear end (secondary side) of the check valve 4. A slow closing check valve etc. have been designed to solve this problem (rapid closing of the disc of a check valve), but the more the disc 4a is closed, the larger the contact area between the backflow fluid and the portion of the disc 4a to which force is applied by the fluid, so the closing speed of the disc 4a is gradually increased. Accordingly, when the disc is fully closed, the disc is rapidly closed due to an increase in the closing speed of the disc. Further, since the disc 4a is slowly closed at the early stage, the amount or the speed of the backflow fluid is increased, so larger slamming is caused. When the closing speed of the disc 4a and the backflow speed of the fluid are increased, as described above, as can be seen from Equation (1), the backflow speed change (ΔV) of the fluid increases and the pressure change (ΔH) also increases. Accordingly, high pressure is instantaneously generated at the rear end (secondary side) of the check valve, and accordingly, water hammer (slamming) is generated. Further, since negative pressure or low pressure is generated at the front end (primary side) of the check valve 4 by rapid closing of the disc 4 of the check valve 4, a vacuum shutoff vale and an air valve are used at present. However, the effect of preventing vacuum cannot be achieved and the degree of removing vacuum after the vacuum is generated is a limit of the current technology.
Therefore, in order to alleviate water hammer due to slamming of the check valve 4, it is required to effectively suppress negative pressure or low pressure at the front end of the disc 4a and prevent the pressure difference at the front and rear ends of the disc 4a from excessively increasing, thereby preventing the disc 4a of the check valve 4 from rapidly closing.
(Patent Document 1) Korean Patent No. 10-0868908, titled “Water hammer preventing system”
(Patent Document 2) Korean Patent No. 10-1538728, titled “Check valve for preventing slam and waterhammer”
The present invention has been made in an effort to solve the problems with water piping systems of the related art and an object of the present invention is to provide a water piping system that can attenuate slamming due to rapid closing of a check valve and corresponding water hammer by preventing or minimizing negative pressure or low pressure at the front end of a check valve by supplying supplementary water at positive pressure to the front end of the check valve, and by reducing a pressure difference between the front end and the rear end, when a pump in a pipe is suddenly stopped, and a method of controlling the water piping system. That is, the object of the present invention is to alleviate slamming and water hammer using a method (controlling the flow of fluid in a pipe) other than physical methods for slowly closing a check valve.
In order to achieve the above object, according to one aspect of the present invention, there is provided a water piping system having a function of alleviating slamming of a check valve, the system including: a pump pressurizing fluid; a main pipe for delivering the fluid pressurized by the pump; a check valve disposed at an outlet port of the pump to prevent backflow of fluid; a sub-pipe having both ends connected to a front side and a rear side of the check valve, respectively, to supply some of fluid at the rear sides of the check valve to the front side of the check valve therethrough when the pump is stopped; and a control valve disposed in the sub-pipe to open and close a flow channel.
The pump may be a plurality of pumps connected to each other in parallel, the sub-pipe may be a plurality of sub-pipes connected to the main pipe and respectively connected to front ends of check valves disposed at outlet ports of the pumps, and the control valve may be disposed in each of the sub-pipes.
The sub-pipes may have first ends respectively connected to the front sides of the check valves disposed at the outlet ports of the pumps and second ends connected to a header, and the header may be connected to the main pipe.
The control valve may be closed after a predetermined period of time passes from the moment when the pump is stopped. The water piping system may further include a controller controlling opening and closing of the control valve, in which the controller may close the control valve after a predetermined period of time passes from the moment when the pump is stopped.
The system may further include: a controller controlling opening and closing of the control valve; a first pressure sensor sensing pressure at the front side of the check valve of the main pipe; and a second pressure sensor sensing pressure at a rear side of the check valve of the main pipe, in which the controller may receive and compare pressures at the front side and the rear side of the check valve sensed by the first pressure sensor and the second pressure sensor, and may close the control valve after a predetermined period of time passes when the pressure at the rear side of the check valve is higher than the pressure at the front side of the check valve as the result of comparing.
The system may further include a differential pressure sensor sensing a pressure difference between the front side and the rear side of the check valve, in which the control valve may close after a predetermined period of time passes when it is determined that pressure at the rear side is higher than pressure at the front side of the check valve on the basis of the pressure difference sensed by the differential pressure sensor.
The system may further include a flow rate sensor disposed at the rear side of the check valve of the main pipe, in which the control valve may be closed after a predetermined period of time passes when it is determined that the pump has been stopped on the basis of flow of fluid sensed by the flow rate sensor.
The control valve may be a mechanical slow closing valve that is closed after a predetermined period of time passes from the moment when the pump is stopped, and the control valve may be a slow closing check valve.
The control valve may include: a valve body disposed in the sub-pipe connecting a front end and a rear end of the check valve in the main pipe; and an actuator having a disc dividing an inside horizontally to the left and right therein, having both ends connected to the front end and the rear end of the check valve in the main pipe, respectively, and opening and closing the valve body when the disc is moved by a pressure difference between the front end and the rear end of the check valve. Further, the system may further include a needle valve disposed at a front side of the actuator.
The sub-pipe connected to the front side of the check valve may have an end extending in the main pipe and curved toward the check valve.
The sub-pipe connected to the front side of the check valve may have an end extending in the main pipe and diagonally disposed toward the check valve.
A pressure tank may be connected between a rear side of the control valve in the sub-pipe and the rear side of the check valve. The control valve may include: a valve body disposed in the sub-pipe having a front end connected to a front end of the check valve of the main pipe and a rear end connected to the pressure tank; and an actuator having a disc dividing an inside horizontally to the left and right therein, having both ends connected to the front end and the rear end of the check valve, respectively, and opening and closing the valve body when the disc is moved by a pressure difference between the front end and the rear end of the check valve. The system may further include a needle valve disposed at a front side of the actuator.
A plurality of pumps may be connected to each other in parallel, a plurality of sub-pipes may be connected to the pressure tank and respectively connected to front ends of check valves disposed at outlet ports of the pumps, and a control valve may be disposed in each of the sub-pipes.
The sub-pipes may have first ends respectively connected to the front ends of the check valves disposed at the outlet ports of the pumps and second ends connected to a header, and the header may be connected to the pressure tank.
The system may further include a diffuser disposed in the pressure tank and connected to the sub-pipe, in which the diffuser may be connected to the sub-pipe connected to a rear side of the control valve, may be annularly disposed around an inner side of the pressure tank, and may have a plurality of spray holes formed through a surface thereof.
The system may further include a diffuser disposed in the pressure tank and connected to the sub-pipe, in which the diffuser may be connected to the sub-pipe connected to a rear side of the control valve and may have an end curved in an elbow shape.
According to another aspect of the present invention, there is provided a method of controlling the water piping system having a function of alleviating slamming of a check valve., the method including: delivering fluid through the main pipe by operating the pump; opening the control valve disposed in the sub-pipe; monitoring whether the pump is operated; and supplying fluid at the rear side of the check valve to the front side of the check valve through the sub-pipe by keeping the control valve open for a predetermined period of time when the pump is stopped, and closing the control valve after a predetermined period of time passes.
According to another aspect of the present invention, there is provided a method of controlling the water piping system described above, the method comprising: delivering fluid through the main pipe by operating the pump; opening the control valve disposed in the sub-pipe; sensing pressure at the front side and pressure at the rear side of the check valve of the main pipe; and comparing the sensed pressures at the front side and the rear side of the check valve and closing the control valve after a predetermined period of time passes when the pressure at the rear side of the check valve is higher than the pressure at the front side of the check valve, as a result of the comparing.
According to the present invention, it is possible to alleviate slamming due to sudden closing of the check valve and corresponding water hammer by minimizing negative pressure and low pressure at the front end of the check valve by supplying some of the fluid at the rear side of the check valve to the front side of the check valve, and by maintaining positive pressure to reduce the pressure difference between the front end and the rear end of the check valve, when the pump is stopped.
The configuration and operation of a water piping system having a function of alleviating slamming of a check valve according to the present invention are described in detail with reference to embodiments and the accompanying drawings. The water piping system stated herein includes all kinds of fluid piping systems such as common water supply pipes, circulation pipes for heating/cooling and industrial facilities, pipes for agriculture and industries, and petrochemical plants.
The sub-pipe 20 is a pipe for supplying some of fluid from the rear side of the check valve 4 to the front side of the check valve 4 to suppress negative pressure or low pressure that is generated at the front side of the check valve when the pump 2 is stopped. To this end, the sub-pipe 20 has both ends connected to the front side and the rear side of the check valve 4 in the main pipe 10 and is connected to the main pipe 10 in parallel with respect to the check valve 4. The sub-pipe 20 connected to the front side of the check valve 4 in the main pipe 10 may be connected to a portion as close as possible to the check valve 4.
The control valve 30 is disposed in the sub-pipe 20. The control valve 30, which is provided to open/close the flow channel of the sub-pipe 20, is opened when the pump is operated, and is closed after a predetermined period of time passes when the pump is stopped.
In water piping systems including a plurality of parallel pumps 2, 2′, and 2″, as shown in
Further, as shown in
Further, as shown in
However, fluid can be supplied only for a predetermined time to the front end of the check valve 4 through the sub-pipe 20 when the pump is stopped. If a large amount of fluid is continuously supplied to the front end of the check valve 4 through the sub-pipe 20, damage may be caused by reverse revolution of the pump, and all the fluid in the pipes returns to the pump, so a large accident may be caused. Accordingly, fluid may be supplied to the front side of the check valve 4 through the sub-pipe 20 temporarily for a predetermined time such that the check valve 4 can be slowly closed. The time may be experimentally determined as an appropriate value in advance, depending on the size or the operation state of the water piping system. According to experimental values, the closing time of the check valve 4 in a piping system equipped with a pressure tank is very short, within several seconds after a pump is suddenly stopped.
In order to supply fluid to the front side of the check valve 4 through the sub-pipe 20 for a predetermined period of time when the pump is suddenly stopped, the control valve 30 may be a slow closing valve that automatically closes or gradually closes when a predetermined period of time passes after the pump is stopped.
To this end,
When it is determined that the pump has been stopped as the result of monitoring whether the pump is operated, the controller 100 closes the control valve 30 after a predetermined period of time (input in advance in the controller 100) passes (S4). To this end, the control valve 30 may have a built-in timer to be closed when a predetermined period of time passes after the controller 100 gives a control instruction.
The fact that the pressure at the front end of the check valve 4 is higher means that the pump is in operation, while the fact that the pressure at the rear end of the check valve 4 is higher means that the pump has been stopped. Accordingly, the controller 100 keeps the control valve 30 open when the pressure at the front side of the check valve 4 is higher than the pressure at the rear side (when the pump is in operation), and closes the control valve 30 in other cases, for example, when the pressure at the rear side of the check valve 4 is higher than the pressure at the front side (when the pump is stopped) (S400).
On the other hand, as another embodiment, the control valve 30 may be controlled to open and close by a differential pressure sensor DPS, as shown in
Further, as another embodiment, the control valve 30 may be controlled to open and close by a flow rate sensor FS, as shown in
Although the control valve 30 is an electrically controlled valve in the above description, the control valve 30 may be a mechanically controlled valve. The mechanical control valve 30 is configured to automatically close after a predetermined period of time passes when the pump is stopped, by a mechanical configuration thereof without a specific part such as the controller 100. The control valve 30 should be a mechanical slow closing valve so that the control valve automatically closes after a predetermined period of time with a pump stopped.
There are various mechanical slow closing valves. For example, the control valve 30 may be a slow closing check valve. In this case, the disc 4a is open while a pump is operated, but when the pump is suddenly stopped, the check valve 4 is closed first and then the control valve 30 in the sub-pipe 20 is closed. That is, a check valve including a hydraulic cylinder that provides a shock-absorbing force opposite to the closing direction of a disc of the control valve may be selected as the control valve 30 so that the disc of the control valve 30 is closed after a predetermined period of time passes. Further, a ‘check valve having parallel-cylinder’ (Korean Patent No. 10-1487748) by the applicant(s) may be selected as the control valve 30 to further decrease the closing speed of the disc.
The valve body 30a is disposed in the sub-pipe 20 connecting the front end and a rear end of a check valve 4 of a main pipe 10 to each other and the actuator 30b is connected to the valve body 30a. In detail, the actuator 30b has a disc D that horizontally divides the inside thereof to the left and right and, both ends of which are connected to the front and rear sides of the check valve 4 of the main pipe 10, respectively, through a hydraulic hose or a common pipe. Further, the disc D in the actuator 30b is connected to a valve unit that connects/disconnects (opens/closes) the flow channel in the valve body 30a so that when the disc D is moved, the valve unit is operated to open/close the flow channel in the valve body 30a. The structure and the connection relationship of the disc D and the valve body 30a are not limited as long as the valve body 30a can be opened/closed when the disc D is moved. The system may be configured such that when the disc D is horizontally moved, the valve unit is horizontally moved to open the flow channel in the valve body 30a, or such that when the disc D is horizontally moved, the valve unit is rotated to open, using a gear assembly such as a rack and pinion between the disc D and the valve unit. When the valve unit is rotated to open and close, the valve body 30a may be a ball valve or a butterfly valve. According to this configuration, when the fluid at the front and rear ends of the check valve flows to the front and rear sides of the actuator 30b, respectively, the disc D in the actuator 30b is moved to any one side by the pressure difference between the front and rear ends. Further, as the disc D is moved, the valve unit of the valve body 30a connected to the disc D is moved and the flow channel of the sub-pipe 20 is closed.
The control valve is controlled to open and close, depending on whether the pump 2 is operated. While the pump 2 is operated, the pressure at the front side is higher than the pressure at the rear side of the check valve 4, and when the pump 2 is stopped, the pressure at the front side is lower than the pressure at the rear side of the check valve 4. Accordingly, while the pump 2 is operated, the disc D in the actuator 30b is moved from the front side to the rear side of the check valve 4 (from the left to the right in
A needle valve 30c may be additionally disposed at the front side of the actuator 30b. When the needle valve 30c is provided, it is possible to reduce the speed of the disc D moving from the rear side to the front side by adjusting the amount of fluid flowing to the main pipe out of the actuator 30b when the disc D in the actuator 30b is moved to the front side from the moment when the pump is stopped, by setting the degree of opening in advance, whereby it is possible to achieve the effect of slowly closing the valve body 30a.
Although the front and rear ends of the actuator 30b are connected to the front and rear ends of the check valve, respectively, in the above description, the front end of the actuator 30b may be connected to the sub-pipe connected to the front end of the check valve and the rear end of the actuator 30b may be connected to the sub-pipe connected to the rear end of the check valve.
Further, various mechanical slow closing valves such as a needle valve, a spring type valve, a diaphragm valve, and a relief valve may be used as the control valve 30 as long as they can close after a predetermined period of time passes with a pump stopped.
Dead water means a phenomenon in which contamination is generated by fluid remaining for a long period of time in the pressure tank 5 connected to the main pipe 10 to prevent water hammer. In particular, when the water piping system is used for delivering tap water, purified water, or milk, the tap water, purified water, or milk to be supplied to the consumers may be contaminated by dead water, so there is a need for measurements for preventing this problem.
Accordingly, in the present invention, the fluid in the pressure tank 5 is continuously discharged to the main pipe 10 by connecting the pressure tank 5 to the sub-pipe 20 so that fluid flows into the pressure tank 5 through the sub-pipe 20 when the pump is operated, whereby it is possible to prevent fluid from remaining for a long period of time and suppress dead water. As described above, when the pressure tank 5 is connected to the sub-pipe 20, it is possible to supply the fluid at the rear side of the check valve 4 to the front side of the check valve 4 through the sub-pipe and to prevent dead water, when the pump is stopped, so it is possible to achieve a double purpose.
On the other hand, though not shown in the figures, in a system having a main pipe 10 that is a circulation pipe, gas in the main pipe 10 flows to a pressure tank 5 through a sub-pipe 20, so the sub-pipe 20 may be used to discharge the gas in the main pipe 10.
In most work sites, a check valve, an electric valve (not shown) for controlling flow rate, and a manual shutoff valve (not shown) are installed at the outlet port of a pump, so a large friction loss is caused by the valves and a large pressure difference is generated between the front end of the check valve 4 and the joint of a pressure tank 5 and a main pipe 10. Accordingly, an environment in which fluid can flow to the pressure tank through a sub-pipe where there is little friction loss is made and a large pressure difference is generated when a pump is operated with the electric valve (not shown) for controlling a flow rate closed by about 10 to 50% to control a flow rate, so the technique for preventing dead water can be more effectively used. Further, it may be possible to control the amount of fluid flowing to the sub-pipe 20 by adjusting the degree of opening of the electric valve (not shown) for controlling a flow rate.
Further, a diffuser 50 connected to the sub-pipe 20 may be additionally provided in the pressure tank 5 so that the fluid supplied through the sub-pipe 20 is uniformly distributed in the pressure tank 5. The diffuser 50, as shown in
Although the present invention was described in detail with reference to embodiments, the scope of the present invention is not limited thereto and includes the range substantially equivalent to the embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0132359 | Sep 2015 | KR | national |
This application is a continuation application of international application PCT/KR2016/010275, filed on Sep. 12, 2016, now pending, which claims foreign priority from Korean Patent Application No. 10-2015-0132359, filed on Sep. 18, 2015 in the Korean Intellectual Property Office, the disclosure of each document is incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/KR2016/010275 | Sep 2016 | US |
| Child | 15864770 | US |
