JP6802685B2 - Water hammer prediction system and water hammer prediction method in piping - Google Patents

Description

The water hammer prediction system and the water hammer prediction method in a pipe according to the present application relate to a technique for predicting the occurrence and location of a water hammer in a pipe such as a steam pipe.

Industrial plants may be equipped with a piping system that transfers steam generated by the boiler to the supply destination at high temperature and high pressure. When steam is liquefied in this pipe, drain (condensed water of steam) stays and the space for steam transfer is reduced, resulting in a decrease in steam transfer efficiency.

In order to avoid such a situation, a large number of steam traps are provided everywhere in the piping system. When the amount of drain water inside the steam trap reaches a certain level due to liquefaction, the built-in float floats and opens the outlet of the steam trap. Normally, the pressure inside the pipe on the inlet side of the steam trap is higher than the pressure inside the pipe on the outlet side, so when the outlet of the steam trap is opened, the drain is automatically discharged from the outlet due to this pressure difference. Will be done. The discharged drain is collected through a drain collection pipe and is generally reused by supplying water to the boiler again.

By the way, when a certain amount of drain is present inside the drain recovery pipe, a water hammer may occur in the drain recovery pipe. Water hammer is a phenomenon that occurs when drainage lumps collide with each other inside a pipe, and when this water hammer occurs, a sudden pressure change of 10 MPa or more may occur instantly inside the pipe. For this reason, if water hammer is repeatedly generated, the joints and valves of pipes at specific locations will be destroyed at once due to the accumulation of the impact, and a large amount of steam and high-temperature drain will be ejected, leading to a risk of a major accident. ..

In addition, as a result of the drain not being properly discharged from the steam trap due to the stall phenomenon, the drain may stay in the heat exchanger and a water hammer may occur in the heat exchanger. In such a case, the heat exchanger may be damaged. , Causes serious damage.

In order to avoid such a danger caused by a water hammer in a pipe, a detection technique as disclosed in the patent document described later has been proposed. In this detection technology, a plurality of thread-like sensors are attached in the circumferential direction of a specific part of the pipe. This sensor is attached to the pipe by applying tension without loosening, and has a structure that breaks when a force exceeding a certain tensile force is applied. When a water hammer is generated in a pipe, the impact causes the pipe to vibrate, so that a force exceeding a certain tensile force is applied to the thread-shaped sensor and the pipe breaks. Therefore, it is possible to detect that a water hammer has occurred in the vicinity of the sensor mounting location by visually recognizing the breakage of the sensor.

Japanese Unexamined Patent Publication No. 2012-68175

However, in the technique disclosed in the patent document, it is not possible to detect if a water hammer does not actually occur in the pipe, and it is not possible to predict the occurrence or location of the water hammer in advance. As mentioned above, the occurrence of water hammer may destroy the piping system and lead to a major accident. Therefore, a technique for predicting the possibility of water hammer occurrence before it occurs is required as much as possible.

Therefore, the water hammer prediction system and the water hammer prediction method in the pipe according to the present application have a problem of solving these problems, and water in the pipe can easily and surely predict the occurrence and location of the water hammer. The purpose is to provide a water hammer prediction system and a water hammer prediction method.

The water hammer prediction system in the piping according to the present application is
Piping that fluid moves from upstream to downstream inside
An on-off valve provided in the piping that shuts off or opens the movement of the fluid. When opened, the open / close valve discharges the fluid from the upstream to the downstream due to the pressure difference between the pressure on the upstream side and the pressure on the downstream side. valve,
An upstream detection unit provided in the upstream piping near the on-off valve, which detects the upstream pressure in the piping and outputs an upstream pressure signal indicating the upstream pressure.
A downstream detection unit provided in the downstream piping near the on-off valve, which detects the downstream pressure in the piping and outputs a downstream pressure signal indicating the downstream pressure.
A calculation unit that captures the upstream pressure signal and the downstream pressure signal and calculates the pressure difference of the downstream pressure with respect to the upstream pressure.
Prediction unit that predicts the occurrence of water hammer in the pipe based on the pressure difference calculated by the calculation unit,
It is characterized by being equipped with.

In addition, the water hammer prediction method in the piping according to the present application is
Piping that fluid moves from upstream to downstream inside
An on-off valve provided in the piping that shuts off or opens the movement of the fluid. When opened, the open / close valve discharges the fluid from the upstream to the downstream due to the pressure difference between the upstream pressure and the downstream pressure. valve,
Regarding the water hammer prediction system equipped with
Detects the upstream pressure in the upstream pipe near the on-off valve and the downstream pressure in the downstream pipe near the on-off valve.
Calculate the pressure difference of the downstream pressure with respect to the upstream pressure,
Predict the occurrence of water hammer in the pipe based on the pressure difference,
It is characterized by that.

In the water hammer prediction system and the water hammer prediction method in the pipe according to the present application, the occurrence of water hammer in the pipe is predicted based on the pressure difference of the downstream pressure with respect to the upstream pressure.

That is, when the on-off valve is opened, the fluid is discharged from the upstream side to the downstream side due to the pressure difference between the upstream side pressure and the downstream side pressure. Therefore, when the pressure difference is not sufficient, the fluid is discharged. It can be predicted that it will not stay on the upstream side. Therefore, it is possible to easily and surely predict the occurrence and location of water hammer due to the retention of fluid.

It is a functional block diagram which shows the 1st Embodiment of the water hammer prediction system and the water hammer prediction method in the pipe which concerns on this application. It is a figure which shows the time-dependent change of the pressure difference calculated by the control unit 6 shown in FIG. It is a functional block diagram which shows the 2nd Embodiment of the water hammer prediction system and the water hammer prediction method in the pipe which concerns on this application. It is a figure which shows the time-dependent change of the pressure difference calculated by the control unit 6 shown in FIG. It is a figure for demonstrating the cause of occurrence of water hammer.

[Explanation of terms in the embodiment]
The main terms shown in the embodiments correspond to the following components of the water hammer prediction system and the water hammer prediction method in the pipe according to the present application, respectively.
Steam, drain 2 ... fluid drain recovery pipe 10, drain connection pipe 12, steam pipe 20 ... piping steam trap 40 ... on-off valve temperature and pressure sensor 31 ... upstream side detector temperature pressure sensor 32 ... downstream side detector control unit 6 ... calculation Unit, prediction unit Reference value a ... Prediction standard Temperature / pressure sensor 33, 34 ... Temperature detection unit

[First Embodiment]
The first embodiment of the water hammer prediction system and the water hammer prediction method in the pipe according to the present application will be described below. Industrial plants may be equipped with a piping system that transfers steam generated by the boiler to the supply destination at high temperature and high pressure. In this embodiment, a water hammer generated in such a piping system is taken as an example, and a technique related to its prediction is illustrated.

(Explanation of the cause of water hammer)
First, the cause of water hammer will be described as a premise. The causes of water hammer are not uniform, but the most common one is considered to be water hammer, which occurs when drains collide with each other due to rapid condensation of steam.

FIG. 5 is a diagram showing the connection points between the drain recovery pipe 10 and the drain connection pipe 11. High-temperature and high-pressure drain 2 generated in various parts of the pipe is collected and transferred into the drain recovery pipe 10 through a large number of drain connection pipes. By the way, when a high-temperature and high-pressure drain is exposed to a low-pressure atmosphere in various places, a flash steam (re-evaporated steam) 4 in which a part of the drain is vaporized is generated, and this flash steam 4 is also transferred together with the drain. As a result, as shown in FIG. 5A, the flush steam 4 transferred through the drain connection pipe 11 is also sent to the drain recovery pipe 10.

Since the temperature of the drain 2 flowing in the drain recovery pipe 10 decreases with the passage of time, when the high temperature flash steam 4 comes into contact with the cold drain 2, the flash steam 4 rapidly condenses due to heat dissipation and drains at once. As a result, the part where the flash vapor was present may temporarily become a state close to vacuum. Then, in this case, as shown in FIG. 5B, the surrounding drain is drawn into this space and collides with it, so that a water hammer is generated.

Water hammer can also be caused by the stall phenomenon. The stall phenomenon is that the pressure difference between the pressure of the pipe on the inlet side of the steam trap and the pressure of the pipe on the outlet side becomes small, and the drain is not discharged from the steam trap and the drain stays inside the heat exchanger or the like. It is a phenomenon.

The steam trap is a structure that utilizes the pressure difference generated by the pressure on the inlet side being higher than the pressure on the outlet side, and discharges the drain from the discharge port on the outlet side by the momentum. Therefore, for example, when the pressure difference becomes small in a float type steam trap, the drain cannot be properly discharged even if the internal float rises, and as a result, the drain gradually flows into the piping on the inlet side of the steam trap. It stays and this drain reaches the piping in the steam trap (for example, heat exchanger) connected to the inlet side. In this state, for example, when high-temperature and high-pressure steam is supplied to the heat exchanger, the steam comes into contact with the accumulated drain and a water hammer is generated, and the impact damages the heat exchanger and surrounding piping members. There is a danger.

(Explanation of block diagram of system in this embodiment)
The configuration of the system in this embodiment will be described with reference to the block diagram shown in FIG. The steam pipe 20 transfers the high-temperature and high-pressure steam generated in the boiler (not shown) to each device in the plant. FIG. 1 illustrates a hot air heater 62, which is a kind of heat exchanger, as a device that receives steam transfer. A valve 45 is provided in the steam pipe 20, and an amount of steam corresponding to the degree of opening and closing of the valve 45 is given to the hot air heater 62.

The steam pipe in the hot air heater 62 is supplied with air for the heater (not shown), and hot air is generated by passing between the steam pipes. When the hot air reaches the set temperature, the valve 45 is closed to reduce the opening degree, and the amount of steam passing through the steam pipe is suppressed. This stops the rise in hot air temperature. Then, when the hot air temperature falls below the set temperature, the opening degree of the valve 45 increases again, the amount of steam in the steam pipe increases, and the hot air temperature rises. In this way, the hot air temperature is maintained at the set temperature by repeatedly opening and closing the valve 45.

By the way, as a result of the latent heat in the thermal energy of the steam being transferred to the object to be heated by the use of steam, the steam is liquefied and drain (condensed water of steam) is generated in the steam pipe. If this drain is excessively retained in the steam pipe, the steam supply efficiency will decrease, so it is necessary to promptly discharge it to the outside.

Therefore, steam traps are provided everywhere in the piping system. For example, a float type steam trap 40 is installed in the piping on the downstream side of the hot air heater 62 shown in FIG. Normally, the pressure in the steam pipe 20 on the upstream side (hot air heater 62 side) of the steam trap 40 is higher than the pressure in the drain connection pipe 12 on the downstream side, so when the float in the steam trap 40 floats, Drain is discharged from the upstream side to the downstream side due to the momentum due to the pressure difference. As a result, the drain is sent out to the drain recovery pipe 10 via the drain connecting pipe 12. The drain 2 collected in the drain collection pipe 10 is collected in a drain tank (not shown) and reused.

Here, a temperature / pressure sensor 31 for detecting the temperature and pressure in the steam pipe is installed in the immediate vicinity of the upstream side of the steam trap 40, and a temperature / pressure sensor 32 is installed in the immediate vicinity of the downstream side of the steam trap 40. Has been done. The temperature / pressure sensor directly detects the temperature and pressure in the steam pipe.

Each of the temperature / pressure sensors 31 and 32 has a wireless communication function, and wirelessly transmits the detected temperature data and pressure data, respectively. Then, these data are received by the receiving unit 5, and the receiving unit 5 further transmits the data to the control unit 6. The control unit 6 includes a memory 7 and controls the display of the monitor 8.

(Explanation of system operation in this embodiment)
Next, the operation of the system in this embodiment will be described. The system according to the present embodiment detects that the pressure difference between the pressure on the upstream side of the steam trap 40 and the pressure on the downstream side becomes smaller than a predetermined reference value, and the stall in which the drain stays in the hot air heater 62. It predicts the occurrence of a phenomenon and predicts the occurrence of a water hammer in the hot air heater 62.

The control unit 6 receives pressure data from the temperature / pressure sensor 31 and the temperature / pressure sensor 32 via the receiving unit 5, respectively. As a result, the control unit 6 grasps the pressure in the pipes on the upstream side and the downstream side of the steam trap 40. Then, the control unit 6 calculates the pressure difference between the pressure on the upstream side and the pressure on the downstream side.

Figure 2 shows the change over time in the pressure difference. As described above, the valve 45 for supplying steam to the hot air heater 62 repeatedly opens and closes in order to adjust the temperature of the hot air. When the valve 45 opens and the amount of steam increases, the pressure on the upstream side of the steam trap 40 increases, and as a result, the pressure difference from the pressure on the downstream side increases. On the contrary, when the valve 45 is closed and the amount of steam is reduced, the pressure on the upstream side of the steam trap 40 becomes low, and as a result, the pressure difference from the pressure on the downstream side becomes small.

A preset reference value a is stored in the memory 7 in the control unit 6 shown in FIG. This reference value a indicates the minimum value of the pressure difference required for the steam trap 40 to discharge the drain on the upstream side toward the downstream side from the discharge port. This value is determined based on the experimental value and empirical value of the drain discharge of the steam trap.

The control unit 6 calculates the pressure difference of the pressure on the downstream side with respect to the pressure on the upstream side of the steam trap 40, and then compares the value of the pressure difference with the reference value a. Then, after P1 when the value of the pressure difference becomes smaller than the reference value a, it is predicted that a stall phenomenon in which drain stays in the hot air heater 62 will occur, so that a water hammer will occur in the hot air heater 62. Foresee that.

Then, the control unit 6 starts a predetermined notification process such as displaying a danger mark of water hammer in the hot air heater 62 on the plan view of the piping system displayed on the monitor 8. Then, at the time point P2 when the value of the pressure difference becomes larger than the reference value a, this notification process is terminated. That is, during the section t1, it is predicted that a water hammer will occur in the hot air heater 62, and the danger mark for the occurrence of the water hammer will continue to be displayed. The notification by this danger mark allows the operator to properly take necessary measures against the water hammer.

[Second Embodiment]
Next, a second embodiment of the water hammer prediction system and the water hammer prediction method in the pipe according to the present application will be described with reference to FIGS. 3 and 4. The basic configuration of the system according to the present embodiment is the same as that of the first embodiment described above. That is, as in the first embodiment, the temperature and pressure sensors 31 and 32 are installed on the upstream side and the downstream side of the steam trap 40, respectively, and the control unit 6 receives each pressure data and the pressure on the upstream side. After calculating the pressure difference of the pressure on the downstream side with respect to the above, in the sections t1 and t2 where the pressure difference value is smaller than the reference value a, it is predicted that a water hammer will occur in the hot air heater 62, and a predetermined notification process is performed. Do.

In the present embodiment, in addition to such a configuration, as shown in FIG. 3, the drain recovery pipe 10 is further provided with temperature and pressure sensors 33 and 34. These temperature and pressure sensors 33 and 34 are installed on both sides of the connection point with the drain connection pipe 12.

Here, in the process of changing the pressure difference of the pressure on the downstream side with respect to the pressure on the upstream side of the steam trap 40, the pressure difference becomes smaller than "0" as shown in the section t3 shown in FIG. 4, that is, the steam trap 40 A reversal phenomenon may occur in which the pressure on the downstream side is larger than the pressure on the upstream side of the. Such a reversal phenomenon also occurs when steam leaks from the upstream side to the downstream side due to deformation of the float in the steam trap 40 or the like.

When the reversal phenomenon occurs, when the float in the steam trap 40 floats, the drain flows in the opposite direction from the downstream side to the upstream side, and under the influence of this, the drain 2 in the drain recovery pipe 10 The proper flow is obstructed, and the drain 2 stays in the drain recovery pipe 10. In such a state, for example, when steam flows into the drain recovery pipe 10 from another path, there is a risk that a water hammer will occur in the drain recovery pipe 10.

Water hammer due to the rapid condensation of steam is likely to occur at cold drain locations. Therefore, the control unit 6 grasps each temperature value based on the temperature signals from the temperature and pressure sensors 33 and 34 at the time point P11 when the reverse rotation decrease occurs, and installs a temperature and pressure sensor having a lower temperature by comparing these. It predicts that a water hammer will occur at a location, and starts a predetermined notification process, such as displaying a danger mark indicating the danger location of the water hammer on the plan view of the piping system displayed on the monitor 8.

Then, at the time point P12 when the value of the pressure difference becomes larger than "0", this notification processing is terminated. That is, during the section t3, it is predicted that a water hammer will occur at the location where the temperature / pressure sensor with a lower temperature is installed, and the notification processing such as the danger mark is continued. By this notification, the operator can properly take necessary measures against the water hammer in the drain recovery pipe 10.

In the present embodiment, the section t3 where the reversal phenomenon occurs occurs within the range of the section t1 where the stall phenomenon is predicted to occur. Therefore, during the section t3, the control unit 6 generates a water hammer in the hot air heater 62. In addition to notifying the location of the water hammer in the drain recovery pipe 10.

In the present embodiment, the temperature and pressure sensors 33 and 34 are provided at two locations on the downstream side of the steam trap 40, but the temperature and pressure sensors are provided at three or more locations and the temperature at the three or more locations is compared to compare the temperature of the water hammer. It is also possible to predict the location of occurrence.

[Other Embodiments]
The water hammer prediction system and the water hammer prediction method in the pipe according to the present application are not limited to the system shown in the above-described embodiment, and other pipes as long as they relate to the prediction of water hammer generated in the pipe in which the fluid moves inside. It can also be applied to strains.

Further, in the above-described embodiment, the temperature and pressure sensors 31, 32, 33, and 34 that directly measure the temperature and pressure are shown, but instead of these, malfunctions such as discharge failure and sealing failure of each steam trap are inspected. It is also possible to utilize an inspection sensor for this purpose. This inspection sensor detects the temperature and vibration in the pipe at the installation location and outputs the temperature data and vibration data.

That is, when the steam trap has a discharge failure, the drain is excessively retained in the nearest pipe and the temperature drops. Therefore, if the detection temperature falls below a certain temperature, it is judged that the discharge failure has occurred. Can be done. Further, when a sealing defect occurs due to deformation of the float of the steam trap or the like, a leaking sound is generated due to steam leakage. Therefore, it can be determined that the sealing defect has occurred if the detection vibration of a specific frequency is detected. Data detected by an inspection sensor for inspecting the malfunction of such a steam trap may be taken in, the pressure may be calculated based on the data, or the temperature may be grasped.

Further, in each of the above-described embodiments, the danger mark of water hammer occurrence is displayed on the plan view of the piping system displayed on the monitor 8 for notification, but for example, the three-dimensional diagram of the piping system is displayed on the monitor 8. , It is also possible to display a danger mark at the place where the occurrence of water hammer is predicted. Further, the danger mark may be displayed by blinking, and an alarm sound such as a buzzer may be emitted at the same time as the danger mark is displayed.

Further, as a danger notification, it is possible to generate an alarm sound, lighting of a lamp, or the like not only on the screen of the monitor 8 but also at the corresponding site in the plant. By processing the danger notification based on the occurrence of the water hammer and the prediction of the occurrence location, it is possible to take appropriate measures according to the situation such as interruption of work or evacuation by the worker at the location.

2: Drain
6: Control unit
10: Drain recovery pipe
12: Drain connection pipe
20: Steam piping
31, 32, 33, 34: Temperature and pressure sensor
40: Steam trap
a: Reference value

Claims (5)

Piping that fluid moves from upstream to downstream inside
An on-off valve provided in the piping that shuts off or opens the movement of the fluid. When opened, the open / close valve discharges the fluid from the upstream to the downstream due to the pressure difference between the upstream pressure and the downstream pressure. valve,
An upstream detection unit provided in the upstream piping near the on-off valve, which detects the upstream pressure in the piping and outputs an upstream pressure signal indicating the upstream pressure.
A downstream detection unit provided in the downstream piping near the on-off valve, which detects the downstream pressure in the piping and outputs a downstream pressure signal indicating the downstream pressure.
A calculation unit that captures the upstream pressure signal and the downstream pressure signal and calculates the pressure difference of the downstream pressure with respect to the upstream pressure.
Prediction unit that predicts the occurrence of water hammer in the pipe based on the pressure difference calculated by the calculation unit,
A water hammer prediction system in the piping, which is characterized by being equipped with. In the water hammer prediction system in the pipe according to claim 1.
The prediction unit predicts that when the pressure difference is smaller than a preset prediction standard, a water hammer will occur at a predetermined location in the piping on the upstream side of the on-off valve.
A water hammer prediction system in the piping that is characterized by this. In the water hammer prediction system in the pipe according to claim 1.
The prediction unit predicts that when the pressure difference is smaller than "0", water hammer will occur at a predetermined location in the pipe on the upstream side of the on-off valve and at a predetermined location in the pipe on the downstream side of the on-off valve. ,
A water hammer prediction system in the piping that is characterized by this. In the water hammer prediction system in the pipe according to claim 3.
A plurality of temperature detection units provided at different locations in the piping on the downstream side of the on-off valve, each of which detects the temperature inside the piping and outputs a temperature signal indicating the temperature.
Is equipped with
The prediction unit takes in each temperature signal and predicts a place where water hammer occurs based on the temperature signal.
A water hammer prediction system in the piping that is characterized by this. Piping that fluid moves from upstream to downstream inside
An on-off valve provided in the piping that shuts off or opens the movement of the fluid. When opened, the open / close valve discharges the fluid from the upstream to the downstream due to the pressure difference between the pressure on the upstream side and the pressure on the downstream side. valve,
Regarding the water hammer prediction system equipped with
Detects the upstream pressure in the upstream pipe near the on-off valve and the downstream pressure in the downstream pipe near the on-off valve.
Calculate the pressure difference of the downstream pressure with respect to the upstream pressure,
Predict the occurrence of water hammer in the pipe based on the pressure difference,
A method of predicting water hammer in piping, which is characterized by this.

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