JP2008196850A - Failure detection system of spring check valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure detection system of a spring check valve capable of effectively detecting the failure condition generated by biting a small foreign matter or the capability of generating the small amount of reverse flow which have been difficult to detect. <P>SOLUTION: The failure of the check valve is made to detect as follows: a pair of pressure sensors are arranged on the primary and the secondary sides adjacent to the spring check valve which is reversely biased against the liquid flow by a spring, at least more than one flow sensors are provided adjacent to the check valve on the flow path for making it possible to monitor the differential pressure and also make it possible to discriminate between the normal directional flow, reverse directional flow, and stationary water. Thereby, the check valve is constituted such that the failure of the check valve etc., are made to be detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an abnormality detection system for a spring-type backflow prevention valve capable of discriminating and detecting abnormalities such as a foreign object biting between a valve body and a valve seat and a decrease in feed water pressure from pressure / flow rate data.

In recent years, with the spread of the direct water supply system, the water supply devices have become more sophisticated and diversified, and the types and number of installations have increased. Inappropriate construction management for these water supply devices may adversely affect not only the water supply system in the building but also the water supply piping system, so ensuring safety in the water supply device is one of the important issues. The characteristics of the backflow prevention device, which is an important component of the water supply equipment, have been evaluated so far, and effective backflow prevention methods according to the risk of backflow have been studied. The current situation is not yet known.
Under such circumstances, configurations shown in Patent Documents 1 and 2 are known as an abnormality detection system for a backflow prevention valve.

JP-A-8-178805 JP 2006-177316 A

  By the way, as the name suggests, the backflow prevention valve is for preventing backflow in the pipeline, and if a failure or abnormality occurs in this, there is a possibility that backflow will naturally occur. In other words, it is only necessary to determine that the backflow prevention valve is abnormal when there is a backflow. When the flow rate of the backflow shows a relatively large change, it is easy to suspect the abnormality of the backflow prevention valve. However, when a small foreign object such as a wire is caught, the change in the flow rate is extremely small, and it is not easy to investigate the cause.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to detect an abnormal state or a minute amount of the check valve caused by biting a small foreign object that is difficult to detect with the conventional configuration. It is an object of the present invention to provide an abnormality detection system for a spring-type check valve that can effectively detect the possibility of the occurrence of backflow.

  In order to achieve the above-described object, in the present invention, a pair of spring-type backflow prevention valves urged in the direction opposite to the water flow direction by the spring pressure are provided on the primary side and the secondary side. A pressure sensor is provided, and at least one flow rate sensor is provided in the vicinity of the backflow prevention valve on the flow path so that the differential pressure between the primary side pressure and the secondary side pressure of the backflow prevention valve can be monitored by the pair of pressure sensors. Means that can distinguish forward flow, reverse flow, and water stoppage by the flow rate sensor were used. That is, a spring-type backflow prevention valve urged by the spring pressure in the direction opposite to the water flow direction, and a pair of pressure sensors installed on the primary side and the secondary side close to the backflow prevention valve And at least one or more flow sensors installed in the vicinity of the check valve on the flow path, and the outputs of the flow sensors and pressure sensors, and collect pressure data and flow data on the primary side and the secondary side in time series. The digital data collection device stores in advance the minimum operating valve differential pressure at which water flow starts when the backflow prevention valve is positive pressure, and the primary side pressure and the secondary side based on the pressure data collected by the digital data collection device The valve differential pressure, which is the pressure difference, is calculated, and the normal flow, the reverse flow, and the water stop are determined based on the flow rate data. Warning if less than pressure It is possible to configure the abnormality detection system of spring-loaded check valve from the emitting determination device. According to this system, it is possible to detect an abnormality such as a foreign matter biting in the check valve and a decrease in the feed water pressure before an abnormal phenomenon such as a reverse flow actually occurs.

  Further, when a reverse flow is determined and the valve differential pressure is less than 0, a means of issuing a severe warning is selectively adopted. In this case, there is an abnormality in the backflow prevention valve, and a backflow actually occurs and it is necessary to take urgent measures.

  Furthermore, even if the valve differential pressure is equal to or higher than the minimum operating valve differential pressure, an alarm is issued when a reverse flow is determined. This is because sensor abnormality is suspected.

  Furthermore, even if the valve differential pressure is equal to or higher than the minimum operating valve differential pressure during positive flow, an alarm is issued if the water flow rate is less than the specified value. This is because there is a suspicion of poor water flow or abnormal sensor.

  By the above means, the present invention can be configured by a simple system, and furthermore, the presence / absence of an abnormality is comprehensively determined from the flow rate and the valve differential pressure. By comparing the valve differential pressure with the minimum operating valve differential pressure, it is possible to accurately grasp the abnormality of the check valve. In addition, by analyzing the valve differential pressure-flow rate characteristics based on the collected primary and secondary pressure data and flow rate data, not only the foreign matter of the check valve is caught, but also the spring pressure due to deterioration over time. It is also possible to discriminate and detect a wide variety of abnormalities such as a drop, a drop in water supply pressure, poor water flow, and sensor failure.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a circuit diagram of the system of the present invention. In the figure, 1 is a spring-type backflow prevention valve as a test equipment, 2 and 2 are front and back of the backflow prevention valve 1 (primary side and secondary side) ), 3 and 3 are flow sensors installed in front of and behind the backflow prevention valve 1, and 4 is a data logger device as a digital data collection device that takes the output of each sensor 2 and 3 and converts it into data 5 calculates the difference between the primary side pressure and the secondary side pressure (valve differential pressure), the flow rate difference, etc. from the flow rate / pressure data converted into data by the data logger device 4 and refers to the data table stored in advance in the memory. However, it is a determination device such as a personal computer that compares the calculated data table values to determine the presence or absence of an abnormality. Reference numeral 6 denotes a pressurizing tank that applies positive pressure and reverse pressure to the check valve 1. Reference numeral 7 denotes a negative pressure generator that applies negative pressure to the primary side of the check valve. Then, using this system, an experiment for detecting abnormalities at the time of positive pressure, reverse pressure, and negative pressure was performed on the three test devices. In addition to the data logger device, the digital data collecting device can take a method such as directly capturing data with a personal computer incorporating an analog / digital conversion device. In addition, it is sufficient that at least one flow sensor is installed in the vicinity of the backflow prevention valve 1 on the flow path, but in each embodiment of the present application, from the viewpoint of more accurately detecting the flow rate on the primary side and the secondary side, It is installed at two locations on the primary and secondary sides.

  In the present invention, the spring-type backflow prevention valve that is most widely distributed among the backflow prevention devices is selected as a detection target instrument, and in the embodiment described later, the aperture is 20 mm, the spring constant is 76 g / cm, and the spring pressure is After removing the low-pressure spring-type backflow check valve (test equipment 1) and the secondary side valve of the pressure reduction type backflow preventer, only the primary side valve is built into the body of the double check valve with a diameter of 20 mm. This is a modified product with a spring constant of 1667 g / cm and a large spring pressure check valve (Equipment 2). Three types of backflow prevention valves (test equipment 3) with a medium pressure were prepared. In addition, for these three types of EUTs 1-3, there is a difference between the normal valve state and the abnormal valve state where the abnormality is reproduced by biting the wire, during positive pressure, reverse pressure, and negative pressure. Experiments were conducted.

Here, using the configuration shown in FIG. 2, an experiment under positive pressure was performed according to the following procedure. The valve V1 is operated as the operation target valve according to the following procedure, while the valve V2 is always fully closed and the valve V3 is always fully open.
The check valve 1 is attached and the valve V1 is fully closed.
The primary pressure is set using the pressurized tank 6.
With the valve V1 fully closed, each part is vented to fill the pipe with water.
(4) Start recording pressure and flow data.
(5) Gradually open the valve V1 in increments of about 1/5 until it is fully opened (check that the flow rate is stable at each opening).
(6) Fully close valve V1.
(7) End data recording.
(8) The primary side pressure by the pressurized tank 6 is changed in the range of 0.1 to 0.8 MPa, and the above procedures (1) to (7) are repeated.

  As an example of Example 1, FIG. 3 shows the result of the normal state and FIG. 4 shows the result of the abnormal state <wire engagement> for the test instrument 3 when the primary pressure is 0.8 MPa. First, as shown in FIG. 3, at the time of normal operation, a valve differential pressure of 0.015 MPa (primary side pressure-secondary side pressure) has already occurred during the initial water stoppage. That is, this valve differential pressure of 0.015 MPa is the minimum operating valve differential pressure. And simultaneously with the start of water flow, both the primary side and the secondary side decreased in pressure, but the valve differential pressure increased to about 0.020 MPa. After that, with the increase in water flow rate, the pressure difference further decreased, although the pressure further decreased on both the primary and secondary sides. When the water was stopped again, the primary / secondary pressure and valve differential pressure recovered to the state before water flow. On the other hand, when a wire having a diameter of 1.0 mm was bitten, no valve differential pressure was generated when the water was stopped at the beginning of the experiment, and the pressure was 0 MPa. However, the transition of the start of water flow was the same as normal. And when it stopped again, it returned to the state before water flow, and the valve differential pressure also became 0 MPa. The flow rate changed in the same way on the primary and secondary sides through a series of experimental operations, and there was no difference between the two. Further, the valve differential pressure during the normal stoppage was different between the other test instruments 1 and 2, but the above-described tendency was the same as that of the test instrument 3.

  Further, FIGS. 5 to 7 show valve differential pressure-flow rate characteristics of the test devices 1 to 3 in Example 1. FIG. From these, it is clear that (1) the valve differential pressure-flow rate characteristic is substantially constant regardless of the magnitude of the positive pressure, as long as the same state is maintained for each test device. (2) In order to start the water flow by applying a positive pressure at normal time, a specific minimum operating valve differential pressure is required for each test device. (3) In the EUT having the same structure, the minimum operating valve differential pressure is proportional to the spring constant.

Next, using the configuration shown in FIG. 8, the test equipment in a normal state was subjected to an experiment under back pressure by the following procedure. The valves V1 and V4 are operated as follows, while the valve V2 is always fully open and the valve V3 is always fully closed.
(1) Attach the check valve 1 and fully open the valve V1 and fully close the valve V4.
(2) The secondary side pressure is set to 0.6 MPa using the pressurized tank 6.
(3) Each part is ventilated with the valve V1 fully opened and the valve V4 fully closed, and the pipe is filled up to the secondary side of the check valve 1.
(4) Start recording pressure and flow data.
(5) The valve V4 is gradually and intermittently opened until it is fully opened (at this time, it is confirmed that no flow rate is generated at each opening).
(6) The valve V1 is gradually and fully closed gradually (at this time, confirm that no flow rate is generated at each opening).
(7) End data recording.

Furthermore, using the configuration shown in FIG. 9, an experiment under a reverse pressure was performed on the EUT under an abnormal condition in which a wire having a diameter of 1.0 mm was bitten in the same manner as in Example 2. The procedure was as follows. The valve V1 was always fully opened and the valves V2 and 3 were operated according to the following procedure.
The check valve 1 is attached, the valve V2 is fully closed, and the valve V3 is fully open.
(2) The secondary pressure is set using the pressurized tank 6.
(3) With the valve V2 fully closed and the valve V3 fully open, each part is vented to fill the inside of the pipe.
After the valve V3 is fully closed, recording of pressure and flow rate data is started.
(5) The valve V2 is opened gradually and gradually until the reverse flow rate suddenly decreases (at this time, it is confirmed that the flow rate is stable at each opening).
(6) The valve V2 is fully closed gradually in stages (At this time, it is confirmed that the flow rate is stable at each opening degree).
(7) End data recording.
(8) The secondary pressure is sequentially changed within a range of 0.1 to 0.6 MPa, and the above procedures (1) to (7) are repeated.

As an example of Examples 2 and 3, FIG. 10 shows the experimental results of a test instrument 3 in a normal state under a 0.6 MPa back pressure, and FIG. 11 shows the test results of a test instrument 2 in an abnormal state under a 0.15 MPa back pressure. First, as shown in FIG. 10, at the beginning of the experiment, the primary side pipe was already opened to the atmosphere and a reverse pressure of 0.6 MPa was applied at the beginning of the experiment. Because the valve body was functioning normally, no back flow occurred. After that, the secondary pressure was gradually reduced, but the primary pressure remained at the original 0 MPa, so that the valve differential pressure approached 0 MPa, but no back flow occurred in this process. . On the other hand, when a wire having a diameter of 1.0 mm is bitten, as shown in FIG. 11, since the pressure before and after the product is the same pressure, no valve differential pressure is generated and 0 MPa, but the primary pressure is reduced. Immediately after that, a negative valve differential pressure was generated, and a back flow occurred because a gap was present between the valve element and the valve seat due to the wire biting. Further, when the primary pressure is gradually decreased, the valve differential pressure increases in the negative direction, and the reverse flow rate increases accordingly. However, when the valve differential pressure reaches -0.05 MPa and the flow rate reaches approximately -6 L / min, the valve instantaneously increases. A phenomenon (yield) that suddenly fluctuated to a differential pressure of −0.15 MPa and a flow rate of about −1.5 L / min occurred. After the yielding, the water flow was stopped while gradually decreasing although the reverse flow rate temporarily increased slightly as the valve differential pressure approached 0 MPa while gradually eliminating the reduced pressure state on the primary side. Note that the flow rate changed in the same way on the primary and secondary sides through a series of experimental operations, and there was no difference between the two. Moreover, although the value of the valve differential pressure and the flow rate at the time of yield occurrence differed for each test equipment, the above-described tendency was the same for other test equipment.

  Furthermore, in Example 3, the valve differential pressure-flow rate characteristic after yield of each of the test devices 1 to 3 is shown in FIGS. From these, it is clear that (1) when reverse pressure is applied to the check valve and the valve differential pressure is increased in the negative direction while the wire is bitten, initially, the reverse flow rate increases accordingly. There is a yield point where the reverse flow rate suddenly decreases when a certain valve differential pressure is exceeded, (2) there is no reverse flow rate above the yield point, and (3) the same condition for each EUT. As long as it is maintained, there is a certain yield point, and the valve differential pressure-flow rate characteristic is almost constant regardless of the magnitude of the back pressure.

Subsequently, an experiment under a negative pressure was performed by the following procedure using the configuration shown in FIG. The valve V1 was always fully opened, and the valves V2 and V3 were operated according to the following procedure as the operation target valves.
(1) Attach a check valve, fully close valve V2, and fully open valve V3.
(2) The tip of the secondary side pipe is submerged in the water tank.
(3) Each part is ventilated while the valve V2 is fully closed and the valve V3 is fully opened, and the pipe is filled with water.
(4) Start the negative pressure generator and maintain the primary pressure at -85 kPa.
(5) After the valve V3 is fully closed, pressure and flow data recording is started.
(6) When normal, fully open, and when abnormal (wire engagement), gradually open the valve V2 until the reverse flow rate decreases (at this time, there should be no reverse flow at normal stage, Confirm that the flow rate is stable at the time of abnormality).
(7) The valve V2 is fully closed gradually in stages (At this time, it is confirmed at each opening degree that no flow rate is generated at normal time and that the flow rate is stable at abnormal time).
(8) End data recording.
(9) Using the pressurized tank 6, the secondary pressure is set to 0.1 MPa, and the above procedures (1) to (8) are repeated.

  As an example of Experimental Example 4, FIG. 16 shows the experimental results under a negative pressure with the secondary side set to 0.1 MPa for the EUT 1 in a normal state and the EUT 2 in an abnormal state in FIG. . First, as shown in FIG. 16, under normal conditions, there is no valve differential pressure at the beginning of the experiment because the pressure is the same before and after the test equipment. If the primary side is in a negative pressure state, the negative valve differential pressure − Although about 0.19 MPa was generated, no back flow occurred because the valve body was functioning normally. On the other hand, in the abnormal state in which a wire having a diameter of 1.0 mm was bitten, the pressure difference was not generated at the beginning of the experiment because the pressure before and after the test equipment was the same pressure, but 0 MPa. As soon as the negative pressure is reached, a negative valve differential pressure is generated, and there is a gap between the valve body and the valve seat due to the biting of the wire. Increased in the negative direction, and the reverse flow increased accordingly. However, when the valve differential pressure reached -0.015 MPa and the flow rate reached approximately -2.5 L / min, the valve differential pressure -0.055 MPa and flow rate -2 were instantaneously reached. A yield phenomenon that suddenly fluctuated to about 0.0 L / min occurred. After yielding, the water flow was stopped while the reverse flow rate gradually decreased as the valve differential pressure approached 0 MPa while gradually eliminating the negative pressure state on the primary side. Note that the flow rate changed in the same way on the primary and secondary sides through a series of experimental operations, and there was no difference between the two. Moreover, although the value of the valve differential pressure and flow rate at the time of yield occurrence differed for each test equipment, the above-mentioned tendency was the same for other test equipment. However, the yield phenomenon could not be confirmed in the experiment in which the secondary side of the EUT 1 was atmospheric pressure. This is considered to be because the negative pressure differential pressure required to bring the valve body and the valve seat into close contact with each other was not generated by the negative pressure alone.

  Furthermore, in Example 4, FIG. 18 shows the valve differential pressure-flow rate characteristics after yielding of the test apparatus 1, and FIG. 19 shows the same characteristics of the test apparatus 2. From these, it is clear that (1) In an abnormal state in which the wire is bitten, the same situation as when reverse pressure is applied is reproduced, yielding through the occurrence of backflow, (2) (3) As long as the same state is maintained for each test equipment, there is a yield point similar to when reverse pressure is applied, and the magnitude of negative pressure Regardless, the valve differential pressure-flow rate characteristic is almost constant.

  Finally, according to the same configuration and procedure as in Example 3, the diameter of the wire was changed and an experiment under back pressure was performed. As an example, under a reverse pressure with the secondary side of the test apparatus 3 being 0.6 MPa, a wire having a diameter of 1.2 mm is inserted in FIG. 20 and a wire having a diameter of 1.6 mm is inserted in FIG. The experimental results are shown. First, when a wire with a diameter of 1.2 mm was bitten, at the beginning of the experiment, the pressure across the EUT 3 was the same pressure, so no valve differential pressure was generated and 0 MPa, but the primary pressure was reduced. Immediately after that, a negative valve differential pressure was generated, and a backflow also occurred due to the presence of a gap between the valve body and the valve seat due to the engagement of the wire. When the primary pressure was further reduced, the valve differential pressure increased in the negative direction, and the reverse flow increased accordingly. However, when the valve differential pressure reached -0.05 MPa and the flow rate reached approximately -14.0 L / min, A yield phenomenon that suddenly fluctuated to a valve differential pressure of -0.6 MPa and a flow rate of -0.5 L / min occurred. After the yielding, the water flow was stopped while the reverse flow rate gradually decreased as the valve differential pressure was brought close to 0 MPa while gradually eliminating the reduced pressure state on the primary side, although there was a slight slight increase. On the other hand, when a wire having a diameter of 1.6 mm is bitten, a negative valve differential pressure is immediately generated by the pressure reducing operation on the primary side, and the above-described 1.2 mm diameter wire is kept until a backflow occurs. Although it was the same as the case, even if the primary side pressure was further decreased, the reverse flow only increased and the yield phenomenon was not generated. As a result of the wide diameter wire widening the gap between the valve body and the valve seat, it was not possible to generate the valve differential pressure in the negative direction necessary to adhere the valve body and the valve seat, It is probable that no surrender occurred. In addition, the above-mentioned tendency generate | occur | produced similarly with other test instruments, and there existed a tendency for the valve differential pressure and flow volume at the time of a yield generation to increase in a negative direction, so that each test instrument became thick. However, even if the wire has the same diameter, the value of the valve differential pressure and flow rate at the time of yielding differs for each test device, and the limit value of the wire diameter at which the yield phenomenon cannot be generated is also the test device. Every one was different. In other words, when the wire is bitten into the EUT under reverse pressure, the smaller the wire diameter, the smaller the reverse flow rate generated at the same valve differential pressure, the valve differential pressure at the yield point, and the reverse flow rate tend to decrease. It became clear that.

As mentioned above, we prepared three types of test equipment (backflow prevention valve), conducted experiments under normal pressure and under normal pressure, under negative pressure, under negative pressure, and collected and analyzed data. As long as the state of the EUT is constant, it has become clear that it has almost constant valve differential pressure-flow rate characteristics from yield to positive pressure regardless of the pressure conditions before and after the EUT. When comparing the normal time and the abnormal time, it became clear that the following two points were different.
(1) When valve differential pressure in the negative direction occurs, backflow does not occur in a normal state, but backflow immediately occurs when a foreign object (wire) is engaged (abnormal state).
(2) When valve differential pressure in the positive direction occurs, water flow is not started until the minimum operating valve differential pressure is reached in a normal state, but water flow is immediately started in an abnormal state.

  More specifically, since the water supply device can always supply water by opening the terminal faucet, positive pressure is always applied to each part of the water supply device, and normally 0 is necessary to enable sufficient water supply. A positive pressure of about 2 MPa is secured. Therefore, the spring-type backflow prevention valve that is normally installed should always be in a positive pressure state of about 0.2 MPa. Considering the EUT having the characteristics shown in FIG. 22 with this as a precondition, since the positive pressure is applied even when the water is stopped, the valve differential pressure during the normal stop is always the lowest operating valve. A differential pressure of 0.015 MPa is indicated, and when water flow is started, a positive flow rate is generated and the valve differential pressure is also increased. Therefore, since this is repeated in a normal stop water operation, the valve differential pressure is always maintained at 0.015 MPa or more.

  On the other hand, in the foreign object biting state, a gap is generated between the valve body and the valve seat, so that the valve differential pressure at the time of water stoppage shows 0 MPa, and a positive flow rate is generated when water flow is started. The valve differential pressure also increases according to the flow rate. For this reason, in the foreign matter biting state, the valve differential pressure may be 0 to 0.015 MPa.

As a situation other than these, if a negative valve differential pressure is generated, this is not an abnormality of the check valve but an abnormality in the feed water pressure. In addition, when a negative valve differential pressure is generated while a foreign object is caught, a back flow also immediately occurs. Based on these facts, the following situations may occur with the spring-type check valve.
(1) When both the feedwater pressure and the backflow prevention valve are in a normal state, no valve differential pressure less than the minimum operating valve differential pressure is generated.
(2) When the water supply pressure is normal and foreign matter is caught, a valve differential pressure of 0 to the minimum operating valve differential pressure is generated when the water stoppage or the minute water flow amount is generated.
(3) The occurrence of a positive valve differential pressure that is less than the minimum operating valve differential pressure under normal conditions is caused by a decrease in the feed water pressure.
(4) Generation of the negative valve differential pressure is caused by the generation of a reverse pressure or a negative pressure in the water supply device. If the alarm setting using the valve differential pressure and the flow rate is performed based on this result, the table shown in FIG. 23 is obtained.

  It is not necessary to always measure when setting the alarm, but after setting the minimum operating valve differential pressure for each check valve, the valve differential pressure is determined as negative value, 0 MPa, minimum operating valve differential pressure, flow rate For, it is necessary to distinguish between reverse flow, water stoppage, and normal flow. Each discriminant value has a width that takes into account the measurement error, but the resolution of each sensor is preferably highly accurate. As for the alarm sequence, a heavy warning is given when the occurrence of backflow is obvious, a light warning is given when there is a risk of backflow occurrence and when the sensor is abnormal. Furthermore, according to the present invention, it is possible to detect a problem caused by the biting of a foreign substance before the backflow occurs. Further, when the spring constant decreases, the minimum operating valve differential pressure also decreases, which is effective for detecting a decrease in spring pressure due to aging.

Circuit diagram of the system of the present invention Circuit diagram of experiment under positive pressure (Example 1) Experimental results of Example 1 (normal state) Experimental results of Example 1 (abnormal state) Valve differential pressure-flow rate characteristics of Example 1 (Test equipment 1) Valve differential pressure-flow rate characteristics of Example 1 (Test equipment 2) Valve differential pressure-flow rate characteristics of Example 1 (Test equipment 3) Circuit diagram of back pressure experiment in normal state (Example 2) Circuit diagram of back pressure experiment in abnormal state (Example 3) Experimental results of Example 2 (under 0.6 MPa back pressure of the test equipment 3) Experimental result of Example 3 (under test instrument 2 under 0.15 MPa back pressure) Valve differential pressure-flow rate characteristics of Example 3 (test equipment 1) Valve differential pressure-flow rate characteristics of Example 3 (test equipment 2) Valve differential pressure-flow rate characteristics of Example 3 (Test equipment 3) Circuit diagram of negative pressure experiment (Example 4) Experimental result of Example 4 (test equipment 1 in a normal state) Experimental results of Example 4 (test equipment 2 in a normal state) Valve differential pressure-flow rate characteristics of Example 4 (test equipment 1) Valve differential pressure-flow rate characteristics of Example 4 (test equipment 2) Experimental result of Example 5 (1.2 mm diameter wire biting) Experimental result of Example 5 (1.6 mm diameter wire biting) Valve differential pressure-flow rate characteristics of another test equipment Example of alarm setting

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spring type backflow prevention valve 2 Pressure sensor 3 Flow rate sensor 4 Data logger device 5 Discriminating device 6 Pressurization tank 7 Negative pressure generator V1-V3 valve

Claims (5)

  Proximity to a spring-type backflow prevention valve energized in the direction opposite to the water flow direction by the spring pressure, a pair of pressure sensors are provided on the primary side and the secondary side, and the backflow prevention valve on the flow path At least one or more flow sensors are provided in the vicinity, and the differential pressure between the primary side pressure and the secondary side pressure of the backflow prevention valve can be monitored by the pair of pressure sensors, and normal flow, backflow and water stoppage can be monitored by the flow rate sensor. An abnormality detection system for a spring-type backflow prevention valve characterized by being distinguishable.   A spring-type backflow prevention valve biased in the direction opposite to the water flow direction by the spring pressure, a pair of pressure sensors installed on the primary side and the secondary side in the vicinity of the backflow prevention valve, At least one or more flow sensors installed in the vicinity of the backflow prevention valve on the flow path, and digital data that takes in the outputs of the flow sensors and pressure sensors and collects primary and secondary pressure data and flow data in time series The collecting device and the minimum operating valve differential pressure that starts the water flow when the backflow prevention valve is positive pressure are stored in advance, and the primary side pressure and the secondary side pressure are based on the pressure data collected by the digital data collecting device. The valve differential pressure, which is the difference, is calculated, and the normal flow, the reverse flow, and the water stop are discriminated based on the flow rate data. At the time of the normal flow or the water stop, the valve differential pressure is greater than the minimum operating valve differential pressure. If it is too small, warn Abnormality detection system of spring-loaded check valve which is characterized by comprising a discrimination device.   3. The abnormality detection system for a spring-type backflow prevention valve according to claim 2, wherein a serious warning is issued when the backflow is determined and the valve differential pressure in the negative direction is calculated.   4. The abnormality detection system for a spring-type backflow prevention valve according to claim 2 or 3, wherein a warning is issued when a backflow is determined even if the valve differential pressure is equal to or greater than a minimum operating valve constant differential pressure. Furthermore, even if the valve differential pressure is greater than or equal to the minimum operating valve differential pressure at the time of normal flow, if the water flow rate is less than the specified value, an alarm is issued. Anomaly detection system.

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