JP2005171767A - Pump switching method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly perform engagement-changeover of a pump, while stabilizing water distribution. <P>SOLUTION: A controller 1 stops PID control by starting a post-starting pump started by the engagement-changeover by a number control part 7. After a specific time T1 passes when a delivery valve of the post-starting pump opens a little, a rotating speed control part 6 sets a target rotating seed in the present operation number on the basis of actual data 4, and controls a rotating speed. When the delivery valve of the post-starting pump fully opens when the operating whole pumps reach the target rotating speed (within a predetermined deviation), the number control part 7 issues a stopping command to a pre-starting pump stopped by the engagement-changeover, and returns the target rotating speed to a rotating speed before the engagement-changeover after a specific time T2, and resumes the PID control by stopping the pre-starting pump. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pump switching system that implements pump replacement support.

  In water and sewage facilities that operate a plurality of pumps, pumps are switched (switched) for uniform operation time and maintenance of the pumps. Conventional pump replacement uses a system in which a start command and a stop command are performed simultaneously, PID control is continued even during the replacement, or the rotational speed is gradually increased or decreased. Further, Patent Document 1 describes that pressure control is performed after the number control.

JP-A-9-251301 (paragraph 0017)

  In the technique of Patent Document 1, there is a problem that the pressure temporarily changes suddenly when the pump is started or stopped.

  In addition, the conventional method in which the start command and the stop command are performed at the same time has a problem that water distribution may stop when the pump cannot be started due to a start traffic jam or the like, which makes it difficult to stably supply water.

  In addition, the conventional method in which PID control is continued during the change has a problem that it takes time until the change is completed because it takes time until the flow rate becomes stable after the increase or decrease in the number of units occurs. There is also a problem that the flow rate fluctuation is large, the pressure rises, and the piping is burdened. In the case of the method of gradually increasing and decreasing the rotational speed, there is a problem that it takes time to complete the replacement.

  An object of the present invention is to provide a pump switching control method and apparatus that overcome the above-mentioned problems of the prior art, suppress a sudden change in pressure during replacement, shorten the replacement time, and enable stable supply of water distribution. There is.

  The present invention that achieves the above object suppresses a sudden change in pressure (flow rate) by temporarily controlling the number of revolutions when changing. For this reason, the operation result data is held as internal data, and the target rotational speed corresponding to the number of operating units is obtained.

  That is, the pump switching method of the present invention instructs the start of the start pump when the start pump to be newly started and the stop pump to be stopped are replaced for a plurality of pumps installed in a plant or the like. The control (for example, PID control) with respect to the pump in operation is stopped, and the rotational speed control is performed by setting the target rotational speed corresponding to the current operating number and the flow rate based on the operation result data.

  Further, when the rotation speeds of all the pumps operating under the rotation speed control reach a predetermined value of the target rotation speed, and the discharge valve of the start pump is fully opened, the target rotation speed is changed before the replacement. Returning to the rotational speed, the stop pump is stopped and the control before the rotational speed control is resumed.

  The pump switching device according to the present invention is a PID that installs a plurality of pumps in a plant and performs a replacement of a start pump to be newly started and a stop pump to be stopped. Number of units for selecting a control unit, a start pump and a stop pump for replacement, and outputting a start command for the start pump and a stop command for the PID control, and a stop command for the stop pump and a restart command for the PID control A control unit and a rotation speed control unit that sets a target rotation speed corresponding to the current operation number and flow rate based on operation performance data and performs rotation speed control are provided.

  ADVANTAGE OF THE INVENTION According to this invention, the flow volume fluctuation | variation at the time of a change is reliably suppressed from the operation performance data of a pump, the sudden change of a pressure (flow volume) can be suppressed, and the stable distribution of water becomes possible.

  In addition, since the target rotational speed is set from the start of the replacement, there is little fluctuation in the rotational speed, and the replacement can be completed quickly.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pump switching method and apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a pump change control device according to an embodiment. Parameters necessary for the replacement control are set in the parameter storage unit 3 from the CRT 10 via the man-machine interface 2 of the controller 1. The parameters include a target flow rate, a start / stop selection machine, a target rotation speed setting timer T1, a pre-replacement rotation speed writing timer T2, and the like.

  The number control unit 7 increases the number of water pumps 9 to be operated at the timing of start of replacement, and starts the start-up selection number machine. At the same time, the output of the PID control unit 5 is stopped. As a result, the number of pumps temporarily increases by one. For this reason, if it is the same rotation speed as before the replacement, the actual flow rate becomes larger than the target flow rate. Therefore, the number of revolutions required to output the flow rate at the time of replacement is fetched from the operation result data 4 of the number of revolutions, and the deviation between the target flow rate and the actual flow rate is performed by performing the revolution number control with the revolution number as a target. To minimize.

  The rotational speed control unit 6 performs rotational speed control based on the target rotational speeds of all the pumps obtained from the actual data in the actual data storage unit 4. When the rotation speeds of all the pumps are equal, the number control unit 7 stops the stop selection machine and reduces the number of water pumps 9 to be operated by one. Thereafter, the target rotational speed of the pump is returned to the rotational speed before the replacement, and the control by the PID control unit 5 is resumed.

  FIG. 2 is an explanatory diagram showing the relationship between PID control and rotational speed control. Normal pump control by the controller 1 performs PID control based on the deviation between the target flow rate and the actual flow rate, and reflects the operation amount in the rotational speed control (NIC). During the changeover control according to the present invention, the PID control is stopped, the rotational speed is directly obtained from the actual data, set, and the NIC control is performed to minimize the fluctuation of the flow rate.

  FIG. 3 is a graph of the actual data of the rotational speed and the flow rate. In this example, when the target flow rate is Q, the number of rotations necessary for the two water pumps is N1. For example, in the change control, when the number of units is temporarily operated, the rotational speed is reduced to N2. Since the actual data storage unit 4 has the actual data shown in FIG. 2, the rotational speed control unit 6 can maintain the target flow rate when the number of water pumps increases by one from the relationship between the target flow rate and the number of operating units. Control for. Thereby, the flow rate (pressure) sudden change at the time of switching can be suppressed.

  FIG. 4 is a flowchart of the pump change process according to an embodiment. First, the operator selects the pump to be operated and the pump to be stopped one by one from the CRT 10 (S10). Then, the change start process is started by quicking the change start button (S11). Next, a start command is output to the start selection car (successor) (S12), PID control is stopped, and the current rotation speed is held (S13). The process up to this point is performed by the number control unit 7.

  Next, the discharge valve of the later machine is opened (S14), and when a fixed time (T1) has elapsed from the timing (s15), the number of revolutions is the target number of revolutions obtained from the number of pumps currently operated and the flow rate at this time. Control is performed (S16). S17 represents a branching process for selecting a flow rate-rotation number curve according to the number of operating units.

  FIG. 5 is a flowchart of the branching process for selecting the rotation speed. Branches with the current number of operating units (S170), and when two units are operating, the number of revolutions is calculated from the flow rate-revolution number curve when two units are operating (S171). When operating 3 units, calculate the number of rotations from the flow rate-rotation number curve when operating 3 units (S172). When operating 4 units, calculate the number of rotations from the flow rate-rotation number curve when operating 4 units. (S173).

  The number control unit 7 again determines whether the actual rotational speed of all the pumps being operated has reached the target rotational speed or an approximate value, and the discharge valve of the subsequent machine has been fully opened (S18). If the determination condition is satisfied, a stop command is output to the stop selection car (starting machine) in S10. After a certain time (S20), the target rotational speed is set to the rotational speed before replacement (S21), and the state before the replacement is restored. When it is confirmed that the starting machine is stopped (S22), the PID control is resumed (S23), and the exchange is completed.

  FIG. 6 shows a timing chart of the change control. This is an example when the pump No. 1 in operation is switched to the pump No. 2. Pump No. 1 is operated at the target pump speed before change, and PID control is executed. When a start command is output to Pump No. 2, PID control is stopped. After pump 2 started operation and the fully closed signal of the discharge valve opening was removed (dimensioned), after a certain time (T1) by the target rotation speed setting timer, all pumps in operation A target rotational speed is set, and rotational speed control is executed.

  The target rotation speed setting timer T1 is set by the loss time of the operation of the discharge valve (time until water is pushed out as a flow rate). The discharge valve of the pump has a characteristic that the flow rate does not increase immediately after being fully closed to open, but increases rapidly after reaching a certain degree of opening. That is, if the target rotational speed is set immediately after the discharge valve of the starter is opened, the discharge amount will not be sufficient and the actual flow rate will be too small. Therefore, by setting the target rotational speed after the elapse of T1 after the discharge valve is fully opened, the replacement control at a value close to the target flow rate becomes possible.

  By the rotational speed control, the rotational speeds of the pump No. 1 and the pump 2 are lowered and raised toward the target rotational speed, respectively. When the actual rotational speeds of both pumps are equal to or close to the target rotational speed and the discharge valve of pump 2 is fully opened, a stop command is output to pump 1.

  After the stop command is output to the pump No. 1, the target rotation speed is set to the rotation speed before replacement after T2 of the rotation speed writing timer before replacement. Then, when the pump No. 1 is stopped from being stopped, the PID control is resumed, and the replacement is completed.

  T2 of the pre-replacement rotation speed writing timer is a pump loss time from the stop command to the stop. When a stop command is output, the water pump is operated at the minimum number of revolutions and stops after a certain time. Even if it is the minimum number of revolutions, the flow rate is out, so if you give the stop command and immediately return the target revolution number of the other pumps before the change, the actual flow rate will become too large for the target flow rate. . Thus, by setting the target rotational speed after the elapse of T2 from the output of the stop command, it is possible to perform replacement control with a value close to the target flow rate.

  According to the present embodiment, since the rotation speed during replacement is obtained from the operation data of the rotation speed, the deviation between the target flow rate and the actual flow rate is small, sudden changes in flow rate and pressure can be suppressed, and stable water distribution is ensured. it can. Further, since the target rotational speed is set from the start of the replacement, the rotational speed is less disturbed and the replacement can be performed quickly.

  In the above embodiment, the rotation speed is obtained from the operation result data of the flow rate and the rotation speed. However, when PID control is performed on the pressure, the rotation speed is calculated using the operation record data of the pressure and the rotation speed. You may ask for it. Further, in addition to the operation result data shown in FIG. 3, similar replacement control is possible with pump characteristic data.

  Moreover, although the change pump was selected by operator operation and the change was started, it is also possible to automate including these selection operations.

The block diagram of the pump change control apparatus by one Example. Explanatory drawing which shows the relationship between PID control and rotation speed control. A graph showing the actual data of flow rate and number of revolutions in a curve. The flowchart which shows the pump change process by one Example. The flowchart of the branch process of rotation speed selection. The timing chart which shows the execution example of a change.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Controller, 2 ... Man machine interface, 3 ... Parameter memory | storage part, 4 ... Performance data memory | storage part, 5 ... PID control part, 6 ... Rotational speed control part, 7 ... Number-of-units control part, 8 ... Process input / output processing part, 9 ... Water pump, 10 ... CRT.

Claims (5)

For a plurality of pumps installed in a plant or the like, in a pump switching method for switching between a start pump to be newly started and a stop pump to be stopped,
At the time of changeover, the start pump is instructed to start, the control for the pump in operation is stopped, and the target speed is set according to the current operation number and flow rate based on the operation result data, and the speed control is performed. The pump switching method characterized by this.   2. The target rotational speed according to claim 1, wherein when the rotational speed of all the pumps operating in the rotational speed control reaches a predetermined value of the target rotational speed and the discharge valve of the starting pump is fully opened. The pump switching method characterized by returning to the rotation speed before the replacement, stopping the stop pump and restarting the control before the rotation speed control.   3. The target rotational speed is set after a predetermined T1 time after the start valve discharge valve opening is fully opened, and the start pump discharge valve opening is fully opened and stopped by the stop pump. A pump switching method, wherein the rotation speed before the change is set after a predetermined time T2 after the command is issued. In a pump switching device that installs a plurality of pumps in a plant and performs switching between a start pump to be newly started and a stop pump to be stopped,
A PID control unit that performs PID control of the pump in operation according to the target flow rate;
A number control unit that selects a start pump and a stop pump for replacement, and outputs a start command for the start pump and a stop command for the PID control, and a stop command for the stop pump and a restart command for the PID control;
A pump switching device, comprising: a rotation speed control unit configured to set a target rotation speed according to a current operation number and a flow rate based on operation result data and to perform rotation speed control. 5. The pump switching device according to claim 4, wherein the rotation speed control unit is configured to perform rotation speed control independently while the PID control unit is stopped.

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