JPH0672599B2 - Water drop prevention device for variable speed pump and operating method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating device for a variable speed pump in a suction operation, and more particularly to a falloff prevention device for the same device that does not require discharging a part of pumped water.

[Background of the Invention]

The following method has been proposed as a technique for preventing the water drop of the pump in the suction operation.

(JP-A-53-124319, JP-A-54-162901, etc.) An outline of one of these techniques will be described with reference to FIGS. 5 and 6. FIG. 5 is a block diagram of the pump device. 1 is a water absorption level, 2 is a foot valve, 3 is a suction pipe, 4 is a variable speed pump, 5
Is a check valve, 6 is a sluice valve, and 8 is a pressure sensor provided in the water supply pipe 7, which sends an electric signal in response to the pressure there.
Further, 9 is a pressure tank, 10 is a replenishment pipe, 11 is a check valve, 12 is a discharge solenoid valve, 13 is a discharge pipe, 14 is a replenishment tank, 15 is a replenishment pipe, 16
Is a ball tap, and 17-1 and 17-2 are sluice valves.

FIG. 6 is an operating characteristic diagram of the pump shown in FIG.
H, the horizontal axis shows the amount of water Q. Here, Ho is the target pressure (corresponding to the total head of the pump), and curves A, B, C, D, E, F, G are the maximum operating speeds of the pumps Nmax, N ₁ , N ₂ , N ₃ , N ₄ , the speed N ₅ corresponding to the discharge rate Qf required to prevent the pump from falling, and the pump Q-at the minimum speed Nmin
H performance is shown. Further, Qa, Qb, Qc, Qe and Qf respectively represent water amounts at the intersections of the above-mentioned target pressure Ho and the curves AF.

The pump 4 detects a pressure change H in the water supply pipe with a change in the amount of water used by the pressure sensor 8 and compares it with a preset target pressure Ho, so that the pump 4 matches the target pressure Ho. Operate at different operating speeds to supply water to the end of the water supply. For example, if the amount of water used changes from Qa → Qb → Qe → Qd → Qe, the operating speed will be accompanied by Nmax → N ₁ → N ₂ → N ₃ → N ₄
It changes like that. However, when the amount of water used is less than Qf, that is, when the pump is operated for a long time with an excessive amount of water, the swirling flow on the suction side of the pump 4 separates the air in the water and collects it on the suction side, causing a water drop phenomenon (pressure drop). Alternatively, the water temperature in the pump rises. Therefore, conventionally, when the amount of water used falls within a range smaller than Qf, the operating speed N ₅ is detected, the solenoid valve 12 shown in FIG. 5 is opened, and part of the pumped water is discharged through the discharge pipe 13, Discharge amount of 4 is always Qf
As described above, the water drop phenomenon (pressure drop) was prevented.
It is also conceivable to provide a flow rate sensor on the discharge side of the pump instead of detecting this speed and thereby detect the excessive water amount Qf.

The replenishment tank 14 in FIG. 5 is for replenishing water from the gland portion when the pump 4 is stopped or against the water leak from the foot valve 2. The replenishment tank 14 is always operated through the replenishment pipe 10 and the check valve 11. Keep the inside of 4 full. Further replenishment tank 14
It is performed via a branch pipe 15 and a ball tap 16.

As described above, in the prior art, a part of pumped water is discharged unnecessarily in order to prevent the water from falling due to the operation when the amount of water is too small, and the countermeasure against this is a technical problem.

[Object of the Invention]

It is an object of the present invention to provide a water supply device for eliminating a water drop phenomenon without wasting part of pumped water when the pump is operated under suction operation conditions.

[Outline of Invention]

The features of the present invention are a pump, a water supply pipe connected to the discharge side of the pump, a pressure tank provided in the water supply pipe, a pressure sensor for detecting the pressure in the pressure tank, and an operation of the pump. In the case of supplying water by changing the operating speed of the pump according to the fluctuation of the demand water amount, the demand water amount decreases, and the rotation speed of the pump becomes a predetermined amount of water that begins to fall. When approaching the corresponding speed, the operating speed of the pump is increased so as to send a sufficient amount of water to supply water to the pressure tank, and thereafter, the pump is operated at an extremely low speed that does not drop for a predetermined time.

Therefore, the discharge pipe can be omitted, the frequency of starting the pump can be suppressed, and the water drop of the pump can be prevented.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of the present embodiment, in which the solenoid valve 12 and the discharge pipe 13 of FIG. 5 shown in the conventional example are omitted, and other points are the same as those in FIG. FIG. 2 is an operating characteristic diagram of FIG. 1, and those denoted by the same symbols as those in FIG. 6 have the same meanings, and those denoted by the same symbols will not be described. Curve F is the amount of water Qf at which falling water begins to occur and the target pressure
The pump Q-H performance curve at the operating speed N ₅ at the intersection point with Ho, curve I, shows that when the amount of water used falls into the falling water operation range smaller than Qf, the air in the water separates and becomes the suction side. The minimum speed Nmin ′ that can be commanded by the variable speed driving means so that the accumulated water drop phenomenon does not occur (specifically, the maximum speed Nmax and the minimum speed Nmin are generally set by the control configuration of the variable speed driving means. The ratio is 10: 1, eg Nmax 3600 rpm
Then Nmin is 360 rpm. ) Q when driving in
-H performance. It is conceivable to operate at the operating speed Nmin 'immediately when the amount of water used falls within the range smaller than Qf, but if this is done, the amount of water used will be smaller than Qf, but the water supply pressure will gradually drop. . If the amount of water used is less than Qf, pump 4
It is possible to stop the pump immediately, but this will increase the frequency of starting the pump. In order to reduce the space and initial cost and to suppress the starting frequency of the pump, it is necessary to continue the operation for a sufficient time within the range smaller than Qf to satisfy these requirements. Therefore, in the present invention, when the amount of water used reaches a range smaller than Qf, it is not operated at the speed Nmin 'immediately, but first, the water supply amount necessary for operating at the speed Nmin' for the sufficient time is held in the pressure tank in advance. After that, it was designed to operate at a speed of Nmin '. The curve J is the Q-H performance when the operating speed of the pump 4 is increased to Nt in order to retain the required amount of water supply in the pressure tank 9. FIG. 3 shows a control device of the present embodiment, PW is a power source, MCB is a wire or a breaker, and INV is a variable speed drive means for a pump motor, although it is not particularly limited to a variable frequency inverter device. . Although not shown, M is a motor for driving the pump 4 shown in FIG. 1, CT
L is a control device that performs these controls by a signal emitted from the pressure sensor 8. FIG. 4 is a flow chart showing the control procedure of the control device, and of course, the contents of the program shown in this figure are stored in the storage unit of the control device, although the explanation is omitted.

Now, assume that the water supply pressure is operating at the operating speed of Ho. In this state, when the control device executes the processing of the loop L ₁ , L ₂ or L ₃ shown in FIG. 4 and the feed water pressure H becomes larger than the target pressure Ho, the deceleration control is performed so that the feed water pressure H exceeds the target pressure Ho. If is smaller, the speed-up control is performed, and if both are equal, the operation is continued without shifting. From this state, when the amount of water used decreases to Qf or less and the operating speed reaches N ₅ or less, the fourth
It is judged at 3 steps in the figure that this state is below N _{5 and} the operation proceeds to 4 steps. As described above, the operation is carried out for the time T ₁ second required to hold the water amount in the pressure tank 9. Command the speed Nt, then invert the inverter in 5 steps.
Command the minimum speed Nmin 'that INV can output and continue operation for ₂ seconds. After that, the counter is incremented by 1 at 6 steps, and it is judged at the next 7 steps whether the preset counter has reached n. If not, the processing from 1 step is repeated. The process proceeds to step, where stop control processing is executed, and jumping is performed to a portion (not shown) of the control for executing restart determination processing, and the subsequent processing is executed. By the way, the above-mentioned counter setting value n
If, Nmin 'time T ₂ for commanding the capacity is small held water may in this time T ₂ set longer to the example water demand water supply pressure (pressure tank or water supply to and have been used near Qf little pressure tank This is provided to prevent this because the pressure inside the pipe) will drop. Therefore, if the time T ₂ is reduced and the time T ₂ is 5 seconds and the counter setting value n is 12 times, the loop L ₄ runs 12 times Nt → Nm
in 'is repeated for 120 seconds and the pump 4 is stopped. In addition,
If the water supply pressure does not drop when the tank capacity is sufficiently large, the counter setting value n may be set to 1 and the time T ₂ may be set appropriately.

As described above, according to the present embodiment, since the impeller in the pump 4 is simply rotating at a low speed because it is operating at an extremely low operating speed Nmin ', it does not perform effective work, so that a swirling flow occurs. In addition, there is an effect that the falling water phenomenon can be eliminated without separating the air in the water.

〔The invention's effect〕

According to the present invention, when the predetermined underwater amount range is reached,
Immediately do not operate at extremely low speed that does not cause water drop phenomenon, first hold the amount of water supply necessary for operating for the sufficient time in the extremely low speed operation in advance in the pressure tank, and then operate at the extremely low speed. Therefore, the discharge pipe can be omitted, the starting frequency of the pump can be suppressed, and the water drop of the pump can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a pump device according to an embodiment of the present invention, FIG. 2 is an operation characteristic diagram of the pump shown in FIG. 1, FIG. 3 is a control device of the pump device, and FIG. 5 is a flow chart showing the control procedure of the control device, FIG. 5 is a configuration diagram of a conventional pump device, and FIG. 6 is an operation characteristic diagram of the pump shown in FIG. 4 is a pump, 5 is a check valve, 8 is a pressure sensor, 9 is a pressure tank, 13 is a replenishing tank, 14 is a ball tap, INV is a variable frequency inverter device, and CTL is a control device.

Claims (3)

[Claims] 1. A pump, a water supply pipe connected to the discharge side of the pump, a pressure tank provided in the water supply pipe, a pressure sensor for detecting the pressure in the pressure tank, and an output of the pressure sensor. On the basis of which water is supplied by changing the operating speed of the pump according to the fluctuation of the demand water amount, the control unit controlling the operation of the pump based on the predetermined amount is defined in accordance with the water amount at which the water drop of the pump begins to occur. With respect to the speed, speed detection means for detecting that the operation speed is lower than or equal to the speed, and operating for a predetermined time so as to increase the operation speed by receiving the detection output of the speed detection means and accumulate water in the pressure tank In response to the completion of the water storage operation of the water storage operation means and the water storage operation means,
A water drop prevention device for a variable speed pump, comprising means for operating at a low speed that does not cause air accumulation and for a predetermined time as a time sufficient to suppress the starting frequency of the pump. 2. The variable speed pump according to claim 1, wherein the low speed at which the air accumulation is not generated is the minimum speed that can be output by the variable speed drive means of the pump. Water fall prevention device. 3. A pump, a water supply pipe connected to the discharge side of the pump, a pressure tank provided on the water supply pipe, a pressure sensor for detecting the pressure in the pressure tank, and an output of the pressure sensor. In a method for operating a variable speed pump, which comprises a control means for controlling the operation of the pump based on the above, and changes the operating speed of the pump according to the fluctuation of the demand water amount to supply water, the water supply pressure and a predetermined target pressure are set. A step of comparing, a step of comparing an operating speed with a predetermined speed corresponding to a water amount at which the water drop of the pump begins to occur when the water supply pressure is lower than the target pressure, and a water amount at which the water drop of the pump begins to occur Then, when the operating speed is lower than or equal to the predetermined speed, the operating speed is increased to operate for a predetermined time so as to accumulate water in the pressure tank. And a step of operating for a predetermined time as a time sufficient to suppress the start frequency of the pump at a low speed that does not cause air accumulation, in response to the completion of the water storage operation step. A method for operating a variable speed pump, comprising: