JPH05172079A - Vertical shaft pump - Google Patents

Abstract

PURPOSE:To maximize the storage effect of a water suction basin in a precedent awaiting operation pump which can be operated at low water levels by providing a vortex prevention device which can prevent generation of vortexes through flow control using suction air and works at below the lowest water level of the water suction basin. CONSTITUTION:An impeller 1 is located below a position corresponding to the lowest water level of a pump water suction basin below which air may be sucked from a suction bell. A plurality of an inlet ports 7 each of which is open to the inner wall surface of a pump casing 2 are provided in the portion of the pump casing 2 beneath the impeller 1. A pipe is provided which is connected at one end to each of the air inlet ports 7 and communicated with atmosphere at the other end. A vortex prevention device 11 is provided which prevents generation of vortexes particularly through flow control using intake air and works at below the lowest water level of the water suction basin. Therefore, the lowest water level up to which drainage operation of the pump is possible can be made lower than in conventional pumps and so the storage effect of the water suction basin can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump installed in a water absorption tank, and more particularly, to a pump installed even when the water level in the water absorption tank is lowered, and is provided for draining water discharged during rainfall, for example. The present invention relates to a pump that is suitable as a pump for performing the preceding standby operation and that can be used for the pump management operation in normal times.

[0002]

2. Description of the Related Art Conventional vertical shaft pumps of this type are disclosed in Japanese Patent Laid-Open No. 63-
As described in 90697 publication, an impeller is installed slightly above a specific water level specific to the pump, which corresponds to the lowest water level that sucks air from the suction bell when the water level when the pump is submerged is below this level. A method of providing a vacuum breaking hole in the pump casing near the minimum water level and separating steam and water into a stable idle state by vacuum breaking when the water level becomes lower than the water level corresponding to the minimum water level. There is.

Another conventional vertical shaft pump of this type is
As described in Japanese Utility Model Laid-Open No. 63-150097, the impeller is positioned at a level lower than the water level in the water absorption tank, and a through hole communicating with the outside is provided near the impeller inlet, and the through hole is connected to a pipe. The other end of the pipe has an opening near the level where the impeller in the water absorption tank submerges, and when the water level drops, air is sucked into the pump suction side from the pipe to control the flow rate and vacuum at a lower water level. There is known a method of causing destruction, separating steam and water, and shifting to idle operation.

[0004]

Usually, in order to perform the preceding standby operation based on the rainfall information or the like, it is desirable that the drainage operation can be performed at the lowest possible water level because the storage effect of the water absorption tank increases.

However, the former one of the conventional techniques cannot be operated at a water level lower than the lowest water level due to the generation of vortices because the flow rate cannot be controlled.

In the latter of the prior arts, the amount of intake increases as the water level decreases, the pumping action gradually decreases, and when the water level reaches near the level at which the intake hole is installed, the water vapor separates. , The impeller shifts to idle operation. Generally, as shown in FIG. 9, it is known that a valve is provided in the intake pipe and air and water are separated when the intake amount is reduced, and the water level at which idling operation is shifted can be adjusted downward. However, in this case, at a certain water level, a sufficient reduction in flow rate required for the submerged depth could not be obtained, and the pump sucked the vortex from the suction bell,
There is a problem that vibration increases and driving becomes impossible,
It was not possible to operate by lowering the water level below a certain level.

An object of the present invention is to control the flow rate of the pump by intake air and to perform drainage operation at a water level lower than LWL so that the water level at which drainage operation is possible is reduced as much as possible to maximize the storage effect of the pump water absorption tank. To increase.

[0008]

In order to achieve the above object, the present invention provides a swirl preventive device which operates at a water level equal to or lower than the minimum water level of a water absorption tank capable of preventing the generation of swirls by controlling the flow rate by intake air. is there.

[0009]

According to the present invention, in the pump for adjusting the flow rate by the intake at the low water level, the intake amount is reduced by narrowing the intake amount to separate the water into the idling operation. By providing a vortex flow preventive device that works below the critical water level at which suction of vortices from the suction bell cannot be prevented only by controlling the flow rate, the water level that can be drained is made as low as possible and stable operation is possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 9, a suction bell 4 is connected to a lower side of a casing liner 3 for accommodating a pump casing 2 and an impeller 1, and an upward direction is a pumping pipe 5 which is a part of the pump casing and a discharge elbow. 6 is connected to form a pump. An intake hole 7 is provided near the lower part of the impeller 1, an intake pipe 8 connected to the intake hole 7 is provided, an intake amount adjusting valve 9 is provided in the intake pipe 8, and an intake port 10 of the intake pipe 8 is provided. It is installed at a position higher than the maximum water level HWL in the water absorption tank, and these constitute a flow rate control device. The intake hole 7 has a conventional minimum water level, that is, the minimum water level WL at which air is sucked from the suction bell below this water level.
1 is provided at a position where air is not taken in through the air intake hole 7.

Now, at a water level WL4 higher than WL1, this pump is operated to lower the water level and the water level in the water absorption tank becomes W.
When L1 is reached, the pump sucks air from the intake hole 7. At this time, the pump is in a gas-liquid two-phase operation, but as the water level decreases, the amount of air taken in also increases and a certain water level WL3
At, the pump becomes unable to pump water, and steam separates and shifts to idle operation. After this, when the water level rises again and the water level reaches WL2, the pump operates in a gas-liquid two-phase operation while inhaling air, and when the inflow amount into the water absorption tank is large relative to the pumped water amount, the water level rises. The temperature continues to rise, and when it reaches WL1, the inflow of air is stopped and the normal pumping operation is started.

FIG. 1 shows an embodiment of the present invention. Now, assume that a preceding standby operation pump as shown in FIG. 9 is installed in the water absorption tank. Water level
If it is in WL4, start the pump and start the intake operation when the water level reaches WL1 as the water level drops. At this time, when the amount of inflow into the water absorption tank is smaller than the amount of discharge of the pump, the water level further decreases, and when the loss coefficient of the intake pipe 8 is small, the water and water are separated when reaching WL3. , Shift to idling operation. At this time, if the intake air amount adjusting valve 9 is adjusted to reduce the intake air amount, the water-water separation does not occur in WL3,
At the lower water level WL3 ', air-water separation occurs.

As described above, by adjusting the intake air amount adjusting valve 9, the water level at which steam is separated can be lowered. However, if the water level is adjusted only by narrowing the intake air amount adjusting valve 9 in this way, at a certain water level, the rate of decrease of the flow rate with respect to the decrease of the water level will be insufficient, and vortices will occur.

Hereinafter, this point will be supplementarily described with reference to FIG.

FIG. 8 schematically shows the result of measuring the relationship between the change in the pump discharge amount and the water level by changing the opening degree of the intake amount adjusting valve 9 in the preceding standby operation pump having the configuration shown in FIG. It is a thing. A, B, and C in the figure show the measurement results when the intake air amount adjusting valve 9 is fully opened, half-opened, and 1 / 4-opened, respectively. The figure also shows the vortex generation limit of this pump system.

As shown in the figure, in the cases of A and B, water-water separation occurs before the vortex occurs, and the pumping is stopped, but the water levels WLa and WLb are considerably higher than the tip of the suction bell 4, respectively. Since the drainage operation cannot be performed at the water level of, the storage effect of the water absorption tank cannot be expected. On the other hand, in the case of C, the water can be drained up to the water level WL6 near the tip of the suction bell 4, but at the water level below WL5 in the figure, a vortex occurs.

As described above, it is difficult to perform the drainage operation to a low water level while suppressing the generation of vortices only by adjusting the intake air amount adjusting valve 9. Therefore, it is conceivable that the intake amount adjusting valve 9 is gradually closed according to the decrease in the water level to perform the drainage operation to the vicinity of the tip of the suction bell 4 along the path indicated by the broken line in the figure, but it is a very delicate valve operation. Is required, and it is not very realistic in terms of reliability and cost.

In the embodiment, since a device (vortex flow prevention device 11) for preventing such a vortex is attached at a water level lower than the water level WL5, the drainage operation is performed up to the water level WL6 near the tip of the suction bell 4 without generating a vortex. Is possible.

In order to prevent the generation of vortices, an eddy current prevention device 1
It is well known that 1 is provided in the water absorption tank, but normally, this type of eddy current prevention device 11 operates at a water level which is 1.5 to 1.9 times higher than the pump diameter from the tip of the suction bell 4. In contrast to the conventional design, this embodiment operates at a water level (WL5) or lower, which is lower than a water level which is 1.5 to 1.9 times higher than the pump diameter from the tip of the suction bell 4. It is a difference.

FIGS. 2 to 3 show a second embodiment, in which an arc-shaped straightening plate 12 is provided along the pump casing provided on the side surface of the pump as the above-mentioned eddy current preventing device. However, the operation and effect are similar to those of the first embodiment.

FIGS. 4 to 5 show a third embodiment, in which a swirl preventive plate 13 which crosses the water absorption tank in the upstream direction of the pump is provided as the aforementioned swirl preventive device. The operation and effect are similar to those of the first embodiment.

Further, FIG. 6 shows, as an eddy current prevention device, a buoyant flat plate 14 which covers a free surface near the pump in the water absorption tank.
The operation and effect are similar to those of the first embodiment. This will be described in detail below.

An eddy current preventing device consisting of a floating plate 14, a guide rod 16 and a stopper 15 is installed behind the pump. The guide rod 16 is fixed vertically from the bottom of the water absorption tank, and the buoyant flat plate 14 moves up and down along the guide rod 16, and the stopper 15 fixed to the guide rod 16 causes the water level WL5 in which a vortex is generated. It is configured to stop at. Now, when the water level of the water absorption tank drops to WL5 or less, the buoyant flat plate 14 moves up and down on the water surface of the water absorption tank in conjunction with the water level to prevent the generation of vortices. After that, when the water level rises again and becomes equal to or higher than WL5, the buoyant flat plate 14 is fixed at the position of WL5.

[0025]

According to the present invention, when the water level is low, the flow rate is controlled by the intake air, and in the preceding standby operation pump which operates to the low water level while preventing the vortex generated in the water absorption tank, the intake air amount is reduced. When you try to operate to a lower water level, if you can not suppress the generation of vortices only by controlling the flow rate by intake air, a swirl preventive device that works below the limit water level is provided, so that pump drainage operation is possible. Since the minimum water level can be made lower than before, the storage effect of the water absorption tank can be increased.

[Brief description of drawings]

FIG. 1 is a side view of a pump showing an embodiment of the present invention.

FIG. 2 is a side view of a pump showing a second embodiment of the present invention.

FIG. 3 is an XX arrow view of the pump showing the second embodiment of the present invention.

FIG. 4 is a side view of a pump showing a third embodiment of the present invention.

FIG. 5 is an XX arrow view of the pump showing the third embodiment of the present invention.

FIG. 6 is a side view of a pump showing a fourth embodiment of the present invention.

FIG. 7 is a view on the arrow XX of the pump showing the fourth embodiment of the present invention.

FIG. 8 is a supplementary explanatory diagram of the embodiment of the present invention.

FIG. 9 is an overall side view of a vertical shaft pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Casing, 4 ... Suction bell, 7 ... Intake hole, 8 ... Intake pipe, 9 ... Intake amount adjustment valve, 11 ... Eddy current prevention device.

Claims (1)

[Claims] 1. An impeller is located below a position corresponding to a minimum level at which the water level of the pump water absorption tank is lower than that of the suction bell, and the pump casing below the impeller has an inner wall surface of the pump casing. In a stand-by standby vertical pump that has a plurality of intake holes open to the air, one end of which is connected to the intake hole, and the other end of which is connected to the atmosphere, a vortex is generated by controlling the flow rate by intake air. A vertical axis pump provided with an eddy current preventive device that operates below the minimum water level of the water absorption tank.