JP2638203B2 - Variable speed water supply device and its operation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable-speed water supply apparatus for adjusting the amount of water in a water supply facility and a method of operating the same.

[Conventional technology]

2. Description of the Related Art Conventionally, in a water supply facility, there is a demand on a user side at a pipe end to obtain a required pressure and flow rate, and the flow rate used varies, but it is necessary to maintain a required pressure. In response to fluctuations in the amount of water used, systems (methods) that vary the speed of the water supply pump using various motor variable speed systems to maintain a constant pump discharge pressure regardless of the magnitude of the water supply load have rapidly spread in recent years. In recent years, however, constant control of terminal pressure by an estimation method has also been systematized.

The system as described above uses an operating pressure, which is a process value, as a PI with respect to a target pressure preset by an arithmetic unit.
(Proportional and integral) control to make the deviation zero.

FIG. 6 shows an example of constant pressure control for keeping the pump discharge pressure constant. The horizontal axis shows the flow rate and the vertical axis shows the pressure. In this case, the discharge pressure P of the pump is a pressure obtained by adding the pressure loss Pc of the pipe at the maximum flow rate to the required pressure Pn at the end of the pipe, and the rotation speed is controlled so that the discharge pressure of the pump is constant.

FIG. 7 is an example of the terminal pressure constant control by the estimation method shown by the same coordinates as FIG. 6, and the pump discharge pressure P is determined in consideration of the pressure loss of the pipeline so that the terminal estimated pressure becomes constant.
The pump discharge pressure is changed according to a change corresponding to the flow rate of the pressure loss Pc of the pipeline, that is, a resistance curve. (Japanese Patent Laid-Open No. 60-15
[Problem to be Solved by the Invention] In the above-described conventional variable speed water supply device, in the case of constant discharge pressure control, the target pressure is always constant regardless of the flow rate and the number of rotations. In the terminal pressure constant control based on the estimation method, there is a point that the PI control does not easily converge because the pressure serving as the target value changes as needed with a change in the flow rate or the rotation speed.

If there is no pressure tank, change in pump speed
There is almost no response delay of the change in the pipe pressure, and it is possible to converge.However, when the pressure tank enters this system, due to the pressure tank capacity and the air filling pressure in the pressure tank, etc.
A response delay occurs between the change in the number of revolutions of the pump and the change in the pressure in the pipe due to the amplitude of the air in the pressure tank, and the hunting state may not be achieved, or a very long time may be required for the convergence. This is because the shrinkage of the air sealed in the pressure tank is much higher than that of water.

For example, if the pressure of the pump during operation changes and falls, a deviation occurs from the target pressure, and the pump attempts to increase the rotation speed by PI control to increase the pressure. When there is a pressure tank, especially when the tank capacity is large, the pressure rises slowly because the air shrinkage rate is large, and when the operating pressure reaches the predetermined target pressure, the rotation speed from PI control has already been increased. Has overshot, and as a result, the pressure is too high. Then, the PI control changes to the rotation speed reduction designation, but when the predetermined target pressure is reached again, the rotation speed reduction command from the PI control has already overshot, and as a result, the rotation speed has fallen too much below the predetermined pressure. This behavior (hunting)
Will be repeated.

In particular, in the case of the estimated terminal pressure constant control method of setting the target pressure by reading the data of the pressure and the rotation speed at the time of the cutoff, when the rotation speed is changed to approach the target pressure,
Since the target pressure changes again due to the change in the number of revolutions, there is a problem that control often does not easily converge.

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable-speed water supply device and a method of operating the same that eliminates a response delay between a change in the number of revolutions of the pump and a change in the pressure in the pipe caused by the pressure tank.

[Means for solving the problem]

Means for Solving the Problems To achieve the above object, an invention according to claim 1 includes a pump, a pressure tank provided on a discharge side of the pump, a pressure sensor for detecting a discharge pressure of the pump, and a small flow rate with a discharge flow rate of the pump. A flow rate switch that can be detected, a variable speed device that varies the speed of the pump, a PI control device, and a control device that has a calculation unit and a control unit that presets the relationship between the rotation speed and the pressure or the relationship between the flow rate and the pressure at each operating point. In a variable-speed water supply device provided with a variable-speed pump, the terminal pressure of the pump is kept constant by an estimation method or the discharge pressure of the pump is kept constant, the branch is branched from a main pipe connected to the pump discharge side. A solenoid valve was installed in the middle of the pressure tank piping, and the control unit of the control device was operated to open the solenoid valve under the condition that the flow rate switch detected a small amount of water. The solenoid valve is configured to be closed, and the variable speed device of the control device is operated at the maximum number of revolutions after opening the solenoid valve at the time of detecting the small amount of water, and after accumulating the pressure in the pressure tank, the pump is operated. The present invention is characterized in that the pump is stopped and restarted when the pressure in the pipe becomes lower than or equal to the pump starting pressure again. Provided pressure tank, pressure sensor that detects pump discharge pressure, flow switch that can detect small amount of water by pump discharge flow rate, variable speed device that varies pump speed, PI control device, rotation speed at each operating point And a control device having a calculation unit and a control unit for presetting the relationship between the pressure and the relationship between the flow rate and the pressure, and keeping the terminal pressure of the pump constant by the estimation method by changing the speed of the pump, or In the operation method of the variable-speed water supply device that keeps the discharge pressure of the pump constant, during steady operation, the solenoid valve attached in the middle of the pressure tank pipe branched from the main pipe connected to the pump discharge side is closed, At the time of the water volume, open the solenoid valve before stopping the pump once, operate the pump motor at the maximum rotation speed, accumulate water in the pressure tank, stop the pump, and if the pipe pressure drops below the pump starting pressure again The pump is restarted, and the electromagnetic valve is closed after a lapse of a predetermined time.

(Operation)

According to the first aspect of the present invention, when the variable speed automatic operation of the water supply pump is started, (i) at first, the solenoid valve is closed, and the pressure tank is disconnected from the system.

(Ii) The PI control unit compares and calculates a preset target pressure and a process value of the pressure sensor from the current rotation speed signal from the variable speed device or the current flow rate signal from the flow rate sensor or the like in the calculation unit of the control device. In addition, an appropriate motor speed command is output by the variable speed device, so that stable constant control of the estimated end pressure or constant discharge pressure can be obtained.

(Iii) When the amount of water used on the load side decreases, the flow rate switch detects the small amount of water, and the pump motor operates at the maximum speed. At this time, the solenoid valve is opened by a signal from the control unit, the pressure tank is connected to the system, and the pressure is stored in the pressure tank.

(Iv) When the pressure accumulation is completed, the pump / motor stops.
In this way, energy saving is achieved by stopping the pump / motor, and a required pressure is secured by the pressure tank while the pump is stopped.

(V) Then, when the amount of water used increases, the pressure in the pressure tank drops, and the pressure reaches the restart pressure, the pump / motor restarts.

(Vi) After a certain period of time has elapsed after the restart, the solenoid valve is closed by a signal from the control unit, the pressure tank is disconnected from the system again, the system is in a steady operation state, and the stable estimated end pressure constant control is again performed. Alternatively, discharge pressure constant control can be performed.

According to the second aspect of the present invention, at the time of steady operation, the solenoid valve attached in the middle of the pressure tank pipe branched from the main pipe connected to the pump discharge side is closed, and when the amount of water is low, the shut-off operation that adversely affects the pump is performed. Before stopping the pump temporarily to prevent or save energy, open the solenoid valve and stop the pump as it is.To maximize the stop time, operate the pump motor at the maximum speed and accumulate pressure in the pressure tank.
After increasing the water holding, stop the pump. Next, when the amount of water used increases again, the water stored in the pressure tank is initially supplied through the solenoid valve in the open state, and is maintained at the supply water pressure. After that, the pump restarts when the pipe pressure falls below the pump starting pressure. Then, after a lapse of a certain period of time when water supply from the pressure tank becomes unnecessary, the electromagnetic valve is closed, the pressure tank is disconnected from the system again, and a steady operation state is set.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flow sheet of a variable speed water supply apparatus for performing constant discharge pressure control or constant estimated end pressure control utilizing the relationship between pressure and frequency, showing a first embodiment of the present invention.

In the figure, a main pipe 13 on the discharge side of a pump (water supply pump) 12 driven by a motor 11 for controlling the number of revolutions by changing the frequency has a pressure on the way downstream of the check valve 14 and the gate valve 15. The tank pipe 13a is branched, and a pressure tank 2 is attached to an end of the tank pipe 13a. An electromagnetic valve 16 is attached in the middle of the pressure tank pipe 13a, and a gate valve 15a is attached before and after the solenoid valve.

A pressure sensor 3 is provided at the branch point of the pressure tank pipe 13a.
The flow switch 4 is attached downstream of the main pipe 13 and communicates with a water supply terminal.

On the other hand, the control device 5 is connected to the variable speed motor 11 and controls the rotation speed of the motor 11, and the variable speed device 6 is connected to the pressure sensor 3 and is controlled by the pressure value in the main pipe 13. A PI control device 7 to be controlled, and a calculation unit 8 connected to the input from the variable speed device 6 and output to the PI control device 7 for presetting the relationship between the rotation speed and the pressure at each operating point, The solenoid valve 16 on the tank pipe 13a is opened based on the input of the water supply amount at the end where the small amount of water is detected by the flow rate switch 4 on the main pipe 13, and after a lapse of a certain time after restarting, the solenoid valve is opened. And a control unit 9 which is connected so as to control so as to perform the closing operation.

 Next, the operation will be described.

When the variable speed automatic operation of the water supply pump is started, (i) the solenoid valve 16 is initially closed and the pressure tank 2
Is disconnected from the system.

(Ii) the target pressure and the pressure sensor 3 set in advance by the arithmetic unit 8 of the control device 5 from the current rotational speed signal from the variable speed device 6
The PI control device 7 compares and calculates the process value, and the variable speed device 6 outputs an appropriate motor rotational speed command, whereby stable constant control of the estimated end pressure or constant discharge pressure is obtained.

(Iii) When the amount of water used on the load side decreases, the flow switch 4 detects the small amount of water, and the pump motor operates at the maximum rotation speed. At this time, the electromagnetic valve 16 is opened by a signal from the control unit 9, the pressure tank 2 is connected to the system, and pressure is stored in the pressure tank 2.

(Iv) When the pressure accumulation is completed, the pump / motor 1 stops. As described above, energy saving is achieved by stopping the pump / motor 1, and the pressure tank 2 is stopped while the pump is stopped.
Thus, the required pressure is secured.

(V) The amount of water used increases, the pressure inside the pressure tank 2 drops,
When the pressure reaches the restart pressure, the pump / motor 1 restarts.

(Vi) After a certain period of time after restarting, the solenoid valve 16 is closed by a signal from the control unit 9, the pressure tank 2 is disconnected from the system again, and a steady operation state is established.
It is possible to perform stable stable control of the estimated end pressure or constant discharge pressure again.

The above operation (operating state) is shown in the flowchart of FIG.

Next, FIG. 2 is a float sheet of a variable-speed water supply device for performing constant control of estimated terminal pressure utilizing the relationship between pressure and flow rate according to a second embodiment of the present invention, which is shown in FIG. The same reference numerals as those described above indicate the same or similar parts.

In this embodiment, a flow sensor 10 is mounted downstream of the flow switch 4 on the main pipe 13 on the discharge side of the pump 12, and the flow sensor 10 is used to preset the relationship between flow and pressure at each operating point. It is connected to the calculation unit 8. In the first embodiment (FIG. 1) described above, the current rotation speed signal is input from the variable speed device 6 by the arithmetic unit 8 of the control device 5, whereas in this embodiment, as described above, The difference is that the current rotation speed signal is input from the flow sensor 10 provided on the main pipe 13, and there is no difference in other points.

According to both the first and second embodiments described above, the estimated end pressure always stable without being affected by the pressure pulsation caused by the pressure tank in a steady operation state without impairing the energy saving effect of attaching the pressure tank. Constant control or constant discharge pressure control is obtained.

FIG. 4 and FIG. 5 show the above effect.
FIG. 4 is a diagram showing a steady state in which the amount of load water is constant, in which the horizontal axis represents time, and the vertical axis represents pressure and rotation speed, and FIG. FIG. 2B shows the structure of the present invention.

As is clear from comparison of these two figures, the conventional method (a
FIG. 4) shows a hunting state, whereas the present invention (b)
In the figure, there is almost no pulsation.

Similarly, FIG. 5 is a diagram showing the convergence state after the load water amount changes, with the horizontal axis representing time and the vertical axis representing pressure and rotation speed, respectively. FIG. FIG. 2B shows the structure of the present invention.

As is clear from comparison of these two figures, the conventional method (a
FIG. 3B shows a state in which the present invention (FIG. 2B) converges without pulsation as compared with FIG.

[Effects of the Invention] As described above, according to the invention of claim 1, a pump, a pressure tank, a pressure sensor for detecting a discharge pressure of the pump, and a flow switch capable of detecting a small amount of water by a discharge flow rate of the pump are provided. A variable speed device of the pump, a PI control device, a control device having a calculation unit and a control unit for presetting the relationship between the rotational speed or the flow rate and the pressure at each operating point, and estimating by operating the pump at a variable speed. In a variable-speed water supply device in which the terminal pressure is kept constant or the discharge pressure is kept constant, an electromagnetic valve is attached in the middle of a pressure tank pipe branched from a main pipe connected to the pump discharge side, and The control unit is configured to open the solenoid valve when the flow rate switch detects a small amount of water, and to close the solenoid valve after a lapse of a predetermined time after restarting. After the solenoid valve is opened at the time of detecting the small amount of water, the pump is operated at the maximum rotation speed, the pump is stopped after accumulating the pressure in the pressure tank, and restarted when the pipe pressure becomes lower than the pump starting pressure again. With such a configuration, without impairing the energy saving effect of attaching the pressure tank,
Pressure pulsation by the pressure tank during steady-state operation can be prevented by eliminating the response delay of the pump rotation speed change and the pipe pressure change by the pressure tank.

According to the second aspect of the present invention, the solenoid valve is closed at the time of steady operation, is opened at the time of a small amount of water, and the pump motor is operated at the maximum rotation speed before the pump stops to accumulate the pressure in the pressure tank. By stopping the pump and controlling the pressure to drop again and close it after restarting (operating method), it is possible to always maintain a stable estimated end pressure constant control without impairing the energy saving effect of attaching the pressure tank. Discharge pressure constant control is obtained.

[Brief description of the drawings]

1 and 2 are flow sheets of a variable speed water supply device showing a first embodiment and a second embodiment of the present invention, FIG. 3 is a flowchart showing the operation of the embodiment of the present invention, and FIG. ) And (b) are comparison diagrams between the conventional method showing a steady state in which the load water amount is constant and the present invention, and FIGS. 5 (a) and (b) show a convergence state after the load water amount changes. FIG. 6 and FIG. 7 are diagrams showing a conventional control system. 1 ... Pump motor, 11 ... Motor, 12 ... Pump,
13 ... Main piping, 14 ... Check valve, 15,15a ... Gate valve, 16 ...
... solenoid valve, 2 ... pressure tank, 3 ... pressure sensor, 4 ...
... Flow switch, 5 ... Control device, 6 ... Variable speed device,
7 ... PI control device, 8 ... Calculation unit, 9 ... Control unit, 10 ...
... Flow sensor.

Claims (2)

(57) [Claims] 1. A pump, a pressure tank provided on a discharge side of the pump, a pressure sensor for detecting a discharge pressure of the pump,
A flow rate switch that can detect a small amount of water by the discharge flow rate of the pump, a variable speed device that varies the speed of the pump, a PI control device, an arithmetic unit that presets the relationship between the rotational speed and the pressure or the relationship between the flow rate and the pressure at each operating point and A control device having a control unit, the variable speed water supply device in which the terminal pressure of the pump is kept constant by the estimation method by keeping the pump variable, or the discharge pressure of the pump is kept constant, Attach an electromagnetic valve in the middle of the pressure tank pipe branched from the main pipe to be connected, and control the control unit of the control device,
When the flow rate switch detects a small amount of water, the solenoid valve is opened and the solenoid valve is closed after a certain period of time after restarting. The pump is operated at the maximum speed after the solenoid valve is opened at the time of detection, the pump is stopped after accumulating pressure in the pressure tank, and restarted when the pipe pressure falls below the pump starting pressure again. Variable speed water supply device characterized by the above-mentioned. 2. A pump, a pressure tank provided on a discharge side of the pump, a pressure sensor for detecting a discharge pressure of the pump,
A flow rate switch that can detect a small amount of water by the discharge flow rate of the pump, a variable speed water supply device that varies the speed of the pump, a PI control device,
A control unit having a calculation unit and a control unit for presetting the relationship between the rotational speed and the pressure or the relationship between the flow rate and the pressure at each operating point, and making the pump variable speed so as to make the terminal pressure of the pump constant by an estimation method. In the operation method of the variable-speed water supply device for maintaining or keeping the discharge pressure of the pump constant, at the time of steady operation, an electromagnetic valve attached in the middle of a pressure tank pipe branched from a main pipe connected to the pump discharge side is used. Close, when the water volume is low, open the solenoid valve before temporarily stopping the pump, run the pump motor at the maximum speed to accumulate water in the pressure tank, stop the pump, and again reduce the pipe pressure to below the pump starting pressure. The operation method is characterized in that the pump is restarted when the pressure drops to a lower value, and the solenoid valve is closed after a certain period of time.