JPH04362292A - Vertical shaft pump - Google Patents

Abstract

PURPOSE:To provide a vertical shaft pump which generates little vibration when performing drainage operation while making air supply. CONSTITUTION:As for a vertical shaft pump which is constituted so that an intake hole 9 is formed on a pump casing below a vane wheel 1, and an intake pipe 10 whose one edge is connected with the intake hole and the other edge is opened to the atmosphere at the level higher than the water level in a pump suction tank, a through hole 13 which communicates to the inside and outside of the pump casing 4 is formed on the pump casing 4 below the vane wheel 1. Accordingly, of the through hole performs the buffer action for the pressure in the intake the part and the water level lowers to the level of the through hole during the air supply operation, air supply is carried out from the through hole, too. Accordingly, the variation of the air intake quantity in the air supply operation or the intake air quantity itself can be reduced in comparison with the conventional case having only the intake hole, and the vibration of the pump can be reduced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a vertical shaft pump installed in a water suction tank, and in particular, it is capable of pumping water even when the water level in the water suction tank is low. The present invention relates to a vertical shaft pump that is suitable as a vertical shaft pump that is installed in an office and performs advance standby operation, and that can also be used for management operation of the pump during normal times.

0002

2. Description of the Related Art Conventional vertical shaft pumps of this type include, for example, as described in Japanese Patent Application Laid-open No. 63-90697.
An impeller is installed at a position slightly above a specific part of the pump that corresponds to the minimum water level at which air will be sucked in if the water level when the pump is submerged is below this level, and an impeller is installed in the pump casing near the minimum water level below the impeller. It is known that a hole is provided for breaking the vacuum, and when the water level becomes lower than the minimum water level, the vacuum breaks and the water runs idle, causing water to fall and disabling the drain operation.

[0003] In addition, as a conventional vertical shaft pump, for example, as described in Japanese Utility Model Application Publication No. 150097/1983, an impeller is located at a location lower than the water level of the water suction tank.
A through hole leading to the outside is provided near the inlet of the impeller, the through hole is connected to a pipe, and the other end of the pipe is provided with an opening near the level at which the impeller is submerged in water in the water absorption tank. Are known. Furthermore, it is also known that the opening of the pipe is set higher than the highest water level in the water absorption tank and is open to the atmosphere.

0004

[Problem to be Solved by the Invention] Normally, in order to perform advance standby operation based on rainfall information, etc., it is desirable to be able to perform drainage operation at the lowest possible water level because the storage effect of water absorption tanks and pipe systems increases. , and setting an appropriate flow rate according to the water level of the water absorption tank is effective in preventing vortices and reducing the surging phenomenon of the water absorption tank.
Enables stable pump operation. However, among the above-mentioned conventional techniques, the former does not take into consideration draining operation at a water level lower than the lowest water level. Drainage operation was not possible at a water level lower than the known lowest water level, which is seven times the level.

According to the latter of the above conventional techniques, when the water level in the water suction tank falls below the level of the opening, air is sucked in through the opening, and as the water level falls, the water pumping action of the pump gradually decreases. , it is possible to perform pumping operation at low water levels, and the transition to the idling state does not occur suddenly. This seems to be suitable for pumps that operate on standby. However, in the latter case, the water level in the water suction tank is low and drainage operation is performed while sucking air, so consideration must be given to avoid increasing the vibration of the pump during suction operation.

According to research conducted by the inventors, a so-called breathing phenomenon, in which the amount of intake air fluctuates during intake operation, is sometimes observed, and at the same time, vibration of the pump increases. This phenomenon of fluctuation in the amount of intake air is thought to be caused by pressure fluctuations at the impeller inlet position where the intake hole is provided, but this effect changes the performance of the pump, so the pressure fluctuation near the impeller entrance increases. This is thought to increase further and become a cause of increased vibration. If a valve is provided in the pipe connected to the intake hole and the valve is throttled, the above-mentioned vibrations will be reduced, but the amount of intake air will be reduced, so there is a problem that the vacuum cannot be broken even if the water level falls.

[0007] Furthermore, when the performance of the pump decreases due to intake air, the operating point shifts to a low flow rate region, but if the pump has unstable characteristics, there is a risk of unstable operation similar to surging. However, in the prior art, no consideration has been given to ensuring stable air intake by reducing pressure fluctuations within the pump near the intake holes.

The present invention was made in order to solve the problems of the prior art described above, and its purpose is to provide a vertical shaft pump that generates small vibrations when draining is performed while drawing air. It is something to do. Another object (second object) of the present invention is to provide a vertical shaft pump that can be operated down to the lowest possible water level during draining operation while drawing air. Still another object (third object) of the present invention is to provide a vertical shaft pump that can perform stable operation even when the pump has unstable characteristics when performing drainage operation in a low flow rate region while drawing air. be.

[0009]

[Means for solving the problem] The above purpose (first purpose)
In order to achieve this, the configuration of the first invention related to the vertical shaft pump of the present invention is to provide an intake hole in the pump casing below the impeller, connect one end to this intake hole, and connect the other end to the water level of the pump water intake tank. In a vertical shaft pump having an intake pipe opened to the atmosphere at a higher level, the pump casing below the impeller is provided with a through hole that communicates the inside and outside of the pump casing. More specifically, the through hole is provided close to the intake hole.

In order to achieve the above second object, the structure of the second invention related to the vertical shaft pump of the present invention is based on the same premise as the first invention, but a through hole is provided below the intake hole, and a water suction tank is provided. The drain is provided at a distance from the intake hole at an interval that allows drainage operation to be performed until the water level of the drain becomes lower than the level of the intake hole.

[0011] Furthermore, in order to achieve the above third objective,
The configuration of the third invention related to the vertical shaft pump of the present invention is that an intake hole is provided in the pump casing below the impeller, one end is connected to this intake hole, and the other end is connected to the atmosphere at a level higher than the water level of the pump water intake tank. In a vertical shaft pump provided with an intake pipe opened to the inner wall of the pump casing below the impeller, a rib is provided on the inner wall of the pump casing below the impeller, the intake hole is located on the rib, and the A through hole is provided on the upstream side of the rib and close to the rib.

0012

[Operation] The operation of each of the above technical means is as follows. Generally, when draining is performed while drawing air through the intake hole, if the amount of intake air fluctuates due to pressure fluctuations near the intake hole in the pump casing, this will cause increased vibration of the pump as described above. In the vertical shaft pump of the first invention, the pump casing below the impeller in which the intake hole is provided is further provided with a through hole that communicates the inside and outside of the casing. The flow rate flowing into the casing increases or decreases due to pressure fluctuations within the casing. By attenuating this pressure fluctuation, fluctuations in the amount of intake air from the intake hole can be reduced, and vibrations of the pump can be reduced (achieving the first objective). Note that in order for the flow rate from the through hole to increase or decrease to closely follow pressure fluctuations near the intake hole, it is preferable to provide the through hole close to the intake hole, thereby minimizing pressure fluctuations near the intake hole. It can be effectively reduced.

The vertical shaft pump of the second invention has the following functions in addition to the above-mentioned pump vibration reduction. The intake hole lowers the pump performance through air intake and prevents the generation of pump suction vortices at low water levels, but if the intake air is taken only from the intake hole, there will be no water flow even if the water level in the water absorption tank falls below the position of the intake hole. If the water level further drops below the level of the through-hole, air will start to be taken in through the through-hole, and water will fall below the impeller for the first time, resulting in no-water operation. Make it. This allows the drainable level to be lower than the conventional level (intake hole level).

Further, in the vertical shaft pump of the third invention, a vertical rib is provided on the inner wall of the pump casing below the impeller, and a through hole is provided close to the rib on the upstream side of the rib with respect to the rotational direction of the impeller. By providing this, when the pump operating point shifts to a low flow rate region and a backflow that swirls in the rotational direction occurs on the suction side of the impeller, this backflow passes through the through hole and is discharged to the outside of the pump casing. As a result, even if the pump has unstable characteristics, the characteristics are made stable, so unstable phenomena such as surging can be prevented, and since backflow does not reach the intake hole, intake is performed stably. In addition, when operating near the normal flow rate, similar to the above, pressure fluctuations within the pump casing during intake operation are attenuated,
Pump vibration can be reduced.

[0015]

Embodiments Each embodiment of the present invention will be described below with reference to FIGS. 1 to 8. [Embodiment 1] FIG. 1 is an overall side view of a vertical shaft pump according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a main part showing an intake hole and a through hole in FIG. 1. As shown in FIG. 1, a suction bell mouth 3, which is a part of the pump casing 4, is connected to the lower side of the casing liner 2, which is a part of the pump casing 4, and which houses the impeller 1. A lift pipe 5 and a discharge elbow 6, which are part of the pump casing 4, are connected to the vertical shaft pump. A discharge pipe 7 and a discharge valve 8 are provided on the discharge side of the discharge elbow 6.
is provided.

Further, an intake hole 9 is bored in the vicinity of the lower part of the impeller 1, and an intake pipe 10 is connected to the intake hole 9, and the intake pipe 10 is further provided with an intake air amount adjusting valve 11.
The suction port 12 of the intake pipe 10 is located at the highest water level (
It opens at a higher position than HWL). A through hole 13 that communicates between the inside and outside of the pump casing 4 is bored in the vicinity of the intake hole 9 and below. If the water level in the water suction tank 20 is above the conventional minimum water level, that is, the minimum water level unique to the pump, which sucks air from the lower end of the suction bell mouth 3 if the water level is lowered below this water level,
The position of the intake hole 9 is adjusted so that air is not taken in from the intake hole 9.
The area of the through hole 13, etc. are set.

The static pressure H (m) at the intake hole 9 is expressed by the following formula (
1).

[Equation 1] Here, H0: Atmospheric pressure (10.33 m), l: Water level (m), hs: Suction loss head of pump casing (m), v: Flow rate of liquid handled at the suction hole (m) ), ΔH: pressure increase (m) due to inflow water from the through hole. In equation (1), ΔH is the inflow amount q of external water from the through hole 13
It changes depending on the value of. That is, if q is large, ΔH will be large. Therefore, the static pressure H changes depending on the area of the through hole 13.

FIG. 2 shows details of the intake hole 9 and the through hole 13 shown in FIG. In the steady state in FIG. 2, the pressure Ha at point a outside the through hole 13 is Ha=H0+l' (here, l' is the water level). Moreover, the pressure Hb at point b inside the through hole 13 is Hb=H0+l'-hs-v2/
2g, so the differential pressure between point a and point b is Ha−Hb=
hs+v2/2g. Therefore, the flow rate expressed by the following equation (2) flows into the pump casing 4 through the through hole 13.

[Math 2] Here, C is a constant and a is the cross-sectional area of the through hole.

This inflow amount q increases or decreases under the influence of pressure fluctuations at point b. Then, by selecting the area and length of the through hole 13 so that the delay in the change in the inflow amount due to the inertia of water in the through hole does not become a problem with respect to the frequency of pressure fluctuation, Due to the change in the inflow amount, pressure fluctuations near point b, that is, the intake hole 9, can be reduced. As shown in FIG. 2, by providing the through hole 13 close to and below the intake hole 9, the effect of reducing the pressure fluctuation is increased.

By the way, FIG. 1 shows that the water level in the water suction tank 20 is expressed by the submerged depth S from the lower end of the suction bell mouth 3.
Water levels WL2 and WL that sequentially decrease as 1, S2, and S3
3, WL4 is shown. In FIG. 1, when the water level in the water absorption tank 20 is in the range B (water levels WL1 to WL4), the pressure P in the intake hole 9 falls below atmospheric pressure, and an intake operation is performed. When the water level is WL2, the pressure P in the intake hole 9 is slightly lower than atmospheric pressure, so the amount of intake air is small and the flow rate of the pump is also slightly reduced. In this case, the immersion depth S1 of the pump is sufficient for the pump flow rate at this time, so no vortex is generated.

When the water level is WL3, the pressure P in the intake hole 9
decreases as the water level decreases, so it becomes smaller than atmospheric pressure by that amount, the intake air volume increases, and the pump flow rate also decreases when the water level reaches WL.
2, the flow rate can be set to a flow rate that does not generate vortices even at the submersion depth S2. When the water level is WL4, the through hole 13 is exposed above the water surface, and the through hole 1
From 3 onwards, you will be able to inhale. Therefore, the amount of intake air increases rapidly, the pump becomes unable to pump water, and the water at the bottom of the impeller 1 falls, resulting in a non-drainage operation state.

In this way, when the water level is higher than that of the through hole 13, the inflow water from the through hole 13 alleviates pressure fluctuations in the adjacent intake hole 9, thereby providing a stable state. It works to realize air intake and prevent vibration increase. On the other hand, when the water level falls below the through hole 13, air is taken in from the through hole 13 in addition to the air intake from the intake hole 9.
Intake volume increases. Therefore, even if the intake air amount adjustment valve 11 is throttled to reduce the intake air amount to prevent vibrations or the like, water will certainly fall due to vacuum breakdown when the water level drops, and standby operation without drainage can be realized. That is, a vibration reduction effect can also be obtained by reducing the amount of intake air.

[Embodiment 2] FIG. 3 is a vertical cross-sectional view of a main part showing an intake hole and a through hole portion of a vertical shaft pump according to another embodiment of the present invention. In the figure, parts with the same reference numerals as those in FIG. 1 are the same parts as in the previous embodiment, so a description thereof will be omitted. In the embodiment shown in FIG. 3, the through hole 13A is spaced downward from the intake hole 9 provided near the inlet of the impeller 1, and is provided at a position close to the suction bell mouth 3 of the pump. When the water level decreases from WL1, the operation continues while taking in air from the intake hole 9. The amount of intake air increases as the water level falls, and the pump flow rate decreases, but the cross-sectional area of the intake hole 9 and the diameter of the intake pipe 10 are adjusted so that pumping is not possible due to vacuum breakdown even if the water level falls beyond the intake hole position WL5. The resistance is determined. On the other hand, vortices are prevented by reducing the pump flow rate. Then, when the water level falls below the level WL6 at which the through hole 13A is provided, air is also taken in through the through hole 13A, so the vacuum is broken and the system enters a non-drainage standby operation.

[0024] From this state, the water level starts to rise, and even if the water level reaches WL6 or higher and the through hole 13A is submerged in water, the state of vacuum breakdown due to the intake hole 9 continues, so the water level does not rise above WL6. Even if the pump is re-drained, the pump will not start re-draining immediately, and hunting in the pump operation can be prevented. Also,
Drainage operation is now possible up to a water level WL6 lower than the level WL5 at which the intake hole 9 was conventionally provided.

[Embodiment 3] FIG. 4 is a vertical cross-sectional view of a main part showing the intake hole and through hole portion of a vertical shaft pump according to still another embodiment of the present invention, and FIG. FIG. In the figure, parts with the same reference numerals as those in FIG. 1 are the same parts as in the previous embodiment, so a description thereof will be omitted. In the embodiment shown in FIG. 4, a plurality of (four in this example) ribs 1 are provided on the inner surface of the pump casing 4 below the impeller 1 in the vertical direction (vertical direction in this example).
4 is provided, and the intake hole 9A and the through hole 13B are bored through the rib 14 in close proximity to each other. These intake holes 9A
The opening inside the casing of the through hole 13B is provided at a position projecting inward from the inner wall surface of the pump casing, that is, at the rib end surface 14a. By providing the intake hole 9A and the through hole 13B at such positions,
Even if the pump operation shifts to a low flow rate region and a backflow occurs on the suction side of the impeller 1, stable intake air and external water inflow are performed.

[Embodiment 4] Next, FIG. 6 is a longitudinal cross-sectional view of a main part showing the intake hole and through hole portion of a vertical shaft pump according to still another embodiment of the present invention, and FIG. -Y arrow sectional view, FIG. 8 is a pump characteristic diagram explaining the effect of the through hole in FIGS. 6 and 7. In the drawings, the same reference numerals as those in FIGS. 4 and 5 are the same parts as in the previous embodiment, so the explanation thereof will be omitted. In the embodiment shown in FIGS. 6 and 7, similarly to the embodiment shown in FIGS. 4 and 5, a vertical rib 14 is provided, an intake hole 9A is provided passing through the rib 14, and an opening inside the casing of the intake hole 9A is provided. A portion is provided at a position projecting inward from the inner wall surface of the pump casing, that is, at the rib end surface 14a. Therefore, the position of the through hole 13C is different from the example of FIGS. 4 and 5,
A hole is formed on the upstream side of the rib 14 close to the rib 14 with respect to the rotational direction of the impeller 1, and is opened at the inner wall surface of the casing.

When the water level is high and the amount of air intake from the intake hole 9A is small, the deterioration in pump performance due to intake air is small, so the pump is operated at around the normal flow rate and no backflow occurs on the suction side of the impeller 1. In such a state, external water flows in from the through hole 13C to alleviate pressure fluctuations within the pump casing 4. On the other hand, the water level decreases, the amount of air intake from the intake hole 9A increases, and the pump operating point shifts to the low flow area.
When a backflow occurs on the suction side of the impeller 1, this backflow flows toward the suction side while rotating in the rotation direction of the impeller 1. The water then collides with the rib 14, passes through a through hole 13C provided on the upstream side of the rib 14 and close to the rib 14, and flows out to the water absorption tank 20 outside the pump casing 4.

In FIG. 8, the horizontal axis shows the flow rate Q, and the vertical axis shows the total head.
FIG. 7 is a pump characteristic diagram showing the case where there are No. 7 through holes 13C with broken lines. If the pump has unstable characteristics in the low flow rate region as shown in Figure 8, this backflow flows out through the through hole 13C, resulting in stable characteristics as shown by the broken line in Figure 8, which prevents surging, etc. This can prevent unstable operation. Furthermore, even if the water level is high and the operation is performed at the normal flow rate, even if dirt or the like adheres to the inlet of the through hole 13C, if the water level drops and the above-mentioned backflow occurs, this backflow will flow through the through hole 13C.
Since it flows out through the 3C, it has the function of removing the adhesion of the above-mentioned dust, etc.

[0029]

As described in detail above, according to the present invention, it is possible to provide a vertical shaft pump that exhibits small vibrations during draining operation while drawing air. Further, according to the present invention (second invention), it is possible to provide a vertical shaft pump that can be operated to the lowest possible water level when draining is performed while drawing air. Further, according to the present invention (third invention), it is possible to provide a vertical shaft pump that can perform stable operation even in a pump having unstable characteristics when draining is performed in a low flow rate region while drawing air. .

[Brief explanation of drawings]

FIG. 1 is an overall side view of a vertical shaft pump according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a main part showing an intake hole and a through hole in FIG. 1;

FIG. 3 is a vertical sectional view of a main part showing an intake hole and a through hole portion of a vertical shaft pump according to another embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of a main part showing an intake hole and a through hole portion of a vertical shaft pump according to still another embodiment of the present invention.

FIG. 5 is a sectional view taken along the line XX in FIG. 4;

FIG. 6 is a vertical cross-sectional view of a main part showing an intake hole and a through hole portion of a vertical shaft pump according to still another embodiment of the present invention.

7 is a sectional view taken along the YY arrow in FIG. 6. FIG.

8 is a pump characteristic diagram illustrating the effect of the through holes in FIGS. 6 and 7. FIG.

[Explanation of symbols]

1 Impeller 3 Suction bell mouth 4 Pump casing 9,9A Intake hole 10 Intake pipe 13, 13A, 13B, 13C Through hole 14 Rib 14a Rib end surface 20 Water absorption tank

Claims (6)

[Claims] [Claim 1] A vertical shaft provided with an intake hole in the pump casing below the impeller, and an intake pipe that connects one end to the intake hole and opens the other end to the atmosphere at a level higher than the water level of the pump water intake tank. A vertical shaft pump, characterized in that the pump casing below the impeller is provided with a through hole that communicates the inside and outside of the pump casing. 2. The vertical shaft pump according to claim 1, wherein the through hole is provided close to the intake hole. 3. A through hole is provided below the intake hole at a distance from the intake hole at an interval that allows drainage operation to be performed until the water level in the water absorption tank becomes lower than the level of the intake hole. The vertical shaft pump according to claim 1. 4. A vertical shaft provided with an intake hole in the pump casing below the impeller, and an intake pipe connected at one end to the intake hole and with the other end open to the atmosphere at a level higher than the water level of the pump water intake tank. A vertical shaft pump characterized in that a rib is provided on the inner wall of the pump casing below the impeller, and the intake hole and a through hole adjacent to the intake hole are provided on the rib. [Claim 5] A vertical shaft provided with an intake hole in the pump casing below the impeller, and an intake pipe with one end connected to the intake hole and the other end opened to the atmosphere at a level higher than the water level of the pump water intake tank. In the pump, a rib is provided on the inner wall of the pump casing below the impeller, the intake hole is located on the rib, and the intake hole is located upstream of the rib with respect to the rotational direction of the impeller and close to the rib. A vertical shaft pump characterized by having a through hole. 6. The vertical shaft pump according to claim 4, wherein the opening of the intake hole is provided at a position projecting inward from the inner wall surface of the pump casing.