JPH0392595A - Vertical shaft pump - Google Patents

Abstract

PURPOSE:To prevent hunting while keeping waiting running performance for full speed by arranging a valve, which is closed through discharge pressure and is opened during closing of a discharge pipe, at a suction port of a reverse U-letter shaped branch pipe connected to an inlet casing, and also by setting a return bend portion of the branch pipe higher than a suction head due to maximum negative pressure in a runner casing. CONSTITUTION:A reverse U-letter shaped branch pipe 3 is connected to a suction casing 2 communicating with an impeller casing 6. A lower open end 7 of the branch pipe 3 is located near the lowest water level, and the branch pipe 3 has an air inlet port 14 for introducing air. A valve 13 is provided at the air inlet port 14 for closing the pipe line by discharge pressure and for opening the pipe line during no-discharge. A return bend portion 8 of the reverse U-letter shaped branch pipe 3 is set higher than the suction head due to the maximum negative pressure generated in the impeller casing 6. Thus, transition from operation in air to pumping operation and vice versa is performed on the basis of different water levels. Consequently, it is possible to prevent hunting while keeping waiting running performance for full speed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a vertical shaft pump that can be operated at full speed regardless of the water level. [Conventional technology] Traditionally, general vertical shaft pumps installed in pump water intake wells of drainage pump stations, etc., have a problem in that when the water level is lower than a certain level, a vortex is generated even though the suction port is underwater. Each pump has its own minimum water level (pumping stop level), at which air-mixed water is sucked into the pump, and if the pump is operated when the water level is lower than this minimum water level, air suction vortices may occur. It has the characteristic of generating vibrations and noise due to breathing phenomena. Therefore, if a general vertical shaft pump like this is operated at full speed and left on standby in case of an unexpected water outflow, etc.
When the water level is below the above-mentioned minimum water level, severe vibrations and noise may occur, causing pump operation malfunction or damage to the foundation or building. Therefore, conventional general vertical shaft pumps do not perform full-speed standby construction, but instead perform dimple rotation only when the water level is higher than the minimum water level, and stop operation when the water level is lower than the minimum water level. It was. However, in recent years, the water retention function of the strata has been decreasing due to an increase in paving ratio and a decrease in green areas due to the progress of urbanization, and at the same time, the amount of water flowing into the water absorption wells has been increasing. There are many cases where large amounts of water suddenly and rapidly flow into water intake wells, such as in so-called flash floods. Therefore, in water intake wells, etc., the water level fluctuates in a short period of time, and the above-mentioned operation system using conventional vertical shaft pumps cannot accurately control the operation start timing and operation stop timing of the vertical shaft pump, and the water level changes. There were concerns that abnormal rises could lead to flooding, and abnormal drops could lead to problems with pump operation. Therefore, in Japanese Patent Application No. EL-280867, the applicant of the present application proposed a vertical shaft pump that can perform stable full-speed standby operation regardless of whether the water level is higher or lower than the minimum water level.

As shown in FIG. 4, this vertical shaft pump has a branch pipe 3 that is much smaller in diameter than the suction port and is open to the atmosphere in a suction side casing 2 in front (upstream side) of a pump impeller 1.
At the same time, an intake valve 4 is connected to the tip of this branch pipe 3.
The intake valve 4 is opened and closed by a signal from a water level detector 5.

This vertical shaft pump is operated at full speed in the atmosphere. When the water level of the water intake well P is rising from below the minimum water level, the intake valve 4 is opened while the water level detector 5 detects that the water level has reached the minimum water level, When the water level detector 5 detects that the water level in the water intake well P has reached the minimum water level, the intake valve 4 is controlled to close. Air is taken into chamber 6 and water is not pumped, so-called
After the full speed operation in air continues without difficulty and the water level reaches the minimum water level, the intake of air from the branch pipe 3 to the impeller chamber 6 is stopped and normal water pumping operation is performed. On the other hand, when the water level of the water intake well P is falling from above the minimum water level, the intake valve 4 is closed while the water level detector 5 detects that the water level has not reached the minimum water level. The condition is maintained and pumping operation continues. When the water level detector 5 detects that the water level has reached the lowest water level, the intake valve 4 is opened, air is sucked into the impeller chamber 6 through the small diameter branch pipe 3, and water pumping is cut off, making pumping operation impossible. 〈Switches to air driving. Therefore, with this vertical shaft pump, it is possible to perform full-speed standby operation that can cope with sudden rises or falls in the water level, and the above-mentioned problems such as flooding caused by an abnormal rise in water level or pump operation malfunction caused by an abnormal drop in water level can be achieved. It becomes possible to prevent such things. [
Problems to be Solved by the Invention] However, the water level detector 5 used in this vertical shaft pump
There are concerns that water quality and dust may have negative effects on water quality. This is an extremely important issue considering that the vertical shaft pump is required to be able to cope with unexpected water outflows. In addition, the intake valve 4, which is operated by an electric valve or a pneumatically operated valve, requires an external drive source, and sequence control is also required to operate it. In light of these circumstances, the applicant further filed the patent application No. 1
- In No. 113193, water level detector and 1! We proposed a vertical shaft pump that can perform stable full-speed standby operation regardless of whether the water level is higher or lower than the minimum water level without using a dynamic intake valve. As shown in FIG. 5, this vertical shaft pump has a branch pipe 3 shaped like an inverted U, with its lower open end 7 set at the same level as or close to the lowest water level LWL, and the U-shaped branch The folded portion 8 of the tube 3 is set at a position higher than the suction lift due to the maximum negative pressure generated in the suction portion of the impeller chamber 6 when the impeller 1 is operated at full speed.

In this vertical shaft pump, when the water level of the water suction well P rises from below the lowest water level LWL during full speed operation, and the water level does not reach the lower open end 7,
Since air is taken into the impeller chamber 6 from the lower open end 7 via the branch pipe 3, water is not pumped and so-called full-speed operation in air continues without difficulty, whereas the water level is lower than the minimum water level LW.
When the lower open end 7 reaches L, the lower open end 7 is sealed with water, and the operation is quickly switched to pumping operation while sucking in the residual air in the suction side casing 2 including the bell mouth 9 and the branch pipe 3, and the remaining air in the suction side casing 2 is removed. A complete pumping operation is performed when the air is completely sucked in, and since the folded part 8 of the branch pipe 3 is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber 6, During pumping operation, water is sucked up by the hanging portion 10 of the branch pipe 3 to a height corresponding to the negative pressure of the impeller chamber 6, and a balanced state is created.
Water is not sucked into the impeller chamber 6 from the branch pipe 3, and water is sucked up only through the suction side casing 2, resulting in smooth water pumping operation. On the other hand, if the water level in the water suction well P is lower than the lowest water level LWL during full speed operation of the vertical shaft pump, and if the water level has not fallen to the lower open end 7, then the lower open end 7 Since the water remains sealed, water pumping continues, and water is sucked up into the hanging portion 10 of the branch pipe 3 to a height corresponding to the negative pressure in the impeller chamber 6, resulting in a balanced state. There is. When the water level reaches the lowest water level LWL and the water seal at the lower open end 7 of the branch pipe 3 is released, the water sucked up into the hanging part 10 falls and opens the branch pipe 3 along its entire length. Air is sucked into the impeller chamber 6 from the open end 7 via the branch pipe 3, and the water filling the suction side casing 2 and the like is shut off with the intake air, and the operation is quickly and easily switched to air operation. According to this vertical shaft pump, the pump can be put on standby in full speed operation in the event of a sudden rise or fall in the water level, and the above-mentioned flooding due to an abnormal rise in water level or pump operation malfunction due to an abnormal drop in water level can be avoided. At the same time, since there is no need to use the water level detector 5 or the water intake valve 4 explained in FIG. Problems such as complication will be eliminated, and it will be possible to reliably deal with unexpected flooding. However, in the vertical shaft pump shown in Figure 5, the lowest water level LW
If the water level fluctuates slowly near L or its lowest ice level L
When the water surface is undulating near the WL, the behavior of the lower open end 7 of the branch pipe 3 being submerged in water and being exposed to the atmosphere is repeated many times in a short period of time, causing the lower open end 7 to When the lower open end 7 is exposed to the atmosphere, the opening area and opening time of the lower open end 7 may be insufficient. When such a situation occurs, a so-called hunting phenomenon occurs, in which insufficient air is intermittently drawn into the impeller chamber 6 by the branch pipe 3 in a short period of time, and the process changes from air operation to pumping operation. Alternatively, there is a concern that the switch from pumping operation to submerged operation may not be performed smoothly, and excessive force may be applied to the impeller l, causing pump malfunction. This hunting phenomenon is especially observed in water absorption well P.
This occurs noticeably when the water level falls from above the lowest water level LWL and switches from pumping operation to submerged operation. This is because the transition between submerged operation and pumped storage operation during full-speed standby operation is performed with reference to the level of the lower open end 7, which is set at the same level as or near the lowest water level LWL. Moreover, the lower open end 7
This is because if the opening area or opening time of the casing 2 is insufficient, it will not be possible to secure the amount of air sucked into the suction side casing 2 that is necessary to quickly shut off the water pumping that has been performed up to that point. The present invention has been made in view of the above circumstances, and by making the transition from submersible operation to pumping operation and the transfer from pumping operation to submersible operation based on different levels, The purpose of this invention is to provide a vertical shaft pump that can prevent the hunting phenomenon described above while maintaining the full speed standby operation performance of the vertical shaft pump explained in the figure.
[A thousand steps to solve the problem] The first invention according to the present invention is an inverted U-shaped in which the lower open end of the suction side casing communicating with the impeller chamber is set at or near the lowest water level of the vertical shaft pump. branch pipe is connected,
An intake port through which air can be introduced is opened in this branch pipe, and a valve that is closed by the pumping pressure of the vertical pump and opened when the pumping is cut off is interposed, and the inverted U-shaped inlet of the branch pipe The folded part is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber. In addition, in order to achieve the above object, the second aspect of the present invention
In the invention, an inverted U-shaped branch pipe whose lower open end is set at or near the lowest water level of the vertical shaft pump is connected to the suction side casing communicating with the impeller chamber, and this branch pipe and the discharge side casing of the vertical shaft pump are connected to each other. A communication pipe is provided to communicate the two with each other, and an intake port is provided in the communication pipe, which is closed by the pumping pressure of the vertical pump and is opened when the pumping is interrupted to open and close the communication pipe to the atmosphere. , the inverted U-shaped folded portion of the branch pipe is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber.

[Operation] According to the first invention, the valve is open during submerged operation because pumping pressure does not act on the valve. Therefore, during submerged operation, if the water level is below the position where the lower open end of the branch pipe is sealed, air is sucked into the impeller chamber from both the lower open end of the branch pipe and the intake port. Therefore, submerged operation continues without pumping water. Even if the water level reaches the water level that seals the lower open end of the branch pipe and air cannot be taken in from the lower open end, air is taken in from the intake port through the valve, so the water does not get pumped up and remains in the air. Driving continues.

When the water level rises further and reaches the pumping start water level, pumping starts from the suction side casing due to the self-priming action of the impeller. In this way, even when water pumping starts, since the folded part of the branch pipe is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller room, water flows through the branch pipe into the impeller room. Since water is not sucked in, the flow of water in the impeller chamber during pumping operation is not disturbed. The valve is closed by the pumping pressure in the discharge side casing generated by pumping operation. Naturally, when the water level is higher than the pumping start water level, pumping operation continues through the suction side casing. Since the valve is closed during pumping operation, even if the water level drops during pumping operation, pumping operation will continue until the water level falls to the lower open end of the branch pipe. As the water level further decreases, it becomes lower than the lower open end of the branch pipe, and when the water seal at the lower open end is released, air is drawn into the impeller chamber from the lower open end due to negative pressure in the impeller chamber. The intake air cuts off the pumped water that filled the casing on the suction side and switches to air operation. When pumping water is cut off, pumping pressure no longer acts on the valve, so the valve opens and air is also taken in from the intake port.

Further, according to the second aspect of the invention, during submerged operation, pumped water does not flow from the discharge side casing to the passage pipe, so pumping water pressure does not act on the valve, so the valve is open. For this reason, if the water level is below the position where the lower open end of the branch pipe is permanently sealed during submerged operation, it will pass through the lower open end of the branch pipe, the intake port, and part of the communication pipe to the branch pipe. Air is drawn into the impeller chamber from the merging path, and air is also drawn into the discharge side casing from the intake port through the communication pipe, allowing air operation to continue without pumping water.

Even if the water level reaches a water level that seals the lower open end of the branch pipe and air is no longer taken in from the lower open end, the air flows from the intake port, through the valve, through part of the communication pipe, and into the branch pipe. Air is sucked into the impeller chamber from the path
Since air is drawn into the discharge side casing from the intake port through the communication pipe, air operation continues without water being pumped up.

When the water level rises further and reaches the pumping start water level, pumping starts from the suction side casing due to the self-priming action of the impeller. In this way, even when water pumping starts, water does not flow into the impeller chamber through the branch pipe because the turned part of the branch pipe is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber. Since it is not sucked in, the flow of water in the impeller chamber during pumping operation is not disturbed. During pumping operation, pumped water flows from the discharge side casing into the communication pipe, and the pumping pressure closes the valve. Naturally, when the water level is higher than the pumping start water level, pumping operation continues through the suction side casing. Since the valve is closed during pumping operation, even if the water level drops during pumping operation, pumping operation will continue until the water level falls to the lower open end of the branch pipe. As the water level further decreases, it becomes lower than the lower open end of the branch pipe, and when the water seal at the lower open end is released, air is sucked into the impeller chamber from the lower open end due to the negative pressure in the impeller chamber. The pumped water filling the suction side casing is cut off by the intake air, and the system switches to air diversion. When pumping water is cut off, pumping pressure no longer acts on the valve, so the valve opens and air is also taken in from the intake port in the same way as above. [Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows a first embodiment of the present invention, in which a suction side casing 2 is connected in communication with the lower side, that is, the upstream side, of an impeller chamber 6 which is internally installed with an impeller l being pivotally supported. A discharge side casing 11 consisting of a pumped water vl1A and a discharge side elbow IIB with a discharge valve 12 interposed therebetween is connected to the upper side, that is, the downstream side, and constitutes a pump body.

An inverted U-shaped branch pipe 3 is connected to the suction side casing 2. The lower open end 7 of this branch pipe 3 is set at the same level as or near the lowest water level LWL specific to the vertical shaft pump, and the folded part 8 is set at the suction lift due to the maximum negative pressure generated in the impeller chamber 6 when the impeller 1 is operated at full speed. It is set higher than the An intake port 14 with a valve l3 interposed therein is provided at one end of the folded portion 8 of the branch pipe 3. As shown in FIGS. 2A and 2B, the valve 13 includes a diaphragm 13A, a valve body 13G integrally connected to the diaphragm 13A via a valve stem 13B, and a valve body 13C that is placed inside the intake port 14. It is constituted by an elastic member 13D that urges the valve seat 14A away from the valve seat 14A. The outer surface of the diaphragm 13A communicates with the lift pipe LIA in the discharge side casing 11 via the pipe line 15. Next, we will explain the operation of the above-mentioned Kaikai. During submerged operation, pumping pressure does not act on valve 13 in Fig. 1, so valve 13
is open as shown in Figure 2A. Therefore, during submerged operation, the water level is lower than the hanging part 10 of the branch pipe 3 in FIG.
If the lower open end 7 of the branch pipe 3 is lower than the lowest wood level LWL for sealing the lower open end 7 of the branch pipe 3, air is sucked into the impeller chamber 6 from both the lower open end 7 of the branch pipe 3 and the intake port 14, so that the pumping ``Driving while distracted'' continues.

Even if the water level reaches or near the lowest level LWL at which the lower open end 7 of the branch v3 is permanently sealed, and air is no longer drawn from the lower open end 7, the valve 13
Air is taken in through the tank, so air operation can continue without pumping water. The water level rises further and pumping starts at water level WL.
When it reaches this point, the self-priming action of the impeller 1 sucks in the residual air in the suction side casing 2 and starts pumping water. In this way, even when water pumping starts, since the folded part 8 of the branch pipe 3 is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber 6, the vertical part l of the branch pipe 3
Water is sucked up to O by a height corresponding to the negative pressure in the impeller chamber 6, and a balanced state is created. Therefore, water is not sucked into the impeller chamber 6 through the branch pipe 3, so that the flow of water in the impeller chamber 6 during pumping operation is not disturbed. The pumping pressure in the discharge side casing 1l generated by pumping water is transmitted to the diaphragm 1 of the valve 13 in FIG. 2A via the pipe l5.
3A, the valve rod 13B is advanced against the elastic member 13D, and as shown in FIG. 2B, the valve body 13c is moved against the valve seat 14A.
Press to close valve 13. Muren, pumping start water level W
When the water level is higher than L, the suction side casing 2
Pumping operation continues throughout the period. Valve 13 is closed during pumping operation. Therefore, even if the water level drops during the pumping operation, the pumping operation continues until the water level drops to the lowest tree level LWL corresponding to the lower open end 7 of the branch pipe 3. That is, even if the water level falls from above the pumping start water level WL to below the pumping start water level WL, the pumping operation continues. When the water level further falls below the lowest water level LWL and the water seal at the lower open end 7 of branch v3 is released,
Water that has been sucked up to a balanced height within the hanging part 10 falls from the lower open end 7 into the water suction well, and is sucked into the impeller chamber 6 from the lower open end 7 of the branch pipe 3 due to negative pressure in the impeller chamber 6. The pumped water filling the suction side casing 2 is cut off by the intake air, and the operation is switched to air operation.

By switching to air operation, the above-mentioned pumping pressure no longer acts on the valve l3, so the valve 13 opens as shown in Fig. 2A, and air is also taken in from the intake port 14. ．． In other words, the transition from submerged operation to pumping operation is at the pumping start water level W.
In contrast, the transition from pumping operation to submerged operation is performed based on the lowest water level LWL, and there is a Since there is a predetermined height difference, the hunting phenomenon mentioned above can be reliably prevented. FIG. 3 shows a second embodiment of the present invention, in which the same or equivalent parts as in the first embodiment are designated by the same reference numerals, and detailed explanation thereof will be omitted. In this embodiment, a tank 16 is interposed in the folded part 8 of the inverted U-shaped branch pipe 3, and a communication pipe 17 is bridged between the ceiling of the tank 16 and the discharge elbow l1B in the discharge side casing 11. That is, the folded portion 8 of the branch pipe 3 and the discharge side casing 11 are configured to communicate with each other through the communication pipe 17. An intake port 14 having a valve 13 formed of, for example, a check valve is provided at a position in the communication pipe 17 that is biased towards the tank 16 side. valve l3
is closed when the pumping pressure flowing into the communication pipe 17 from the discharge side casing l1 is loaded, and is opened when the pumping pressure load is released by shutting off the pumping water, and the atmosphere flows into the pump from the intake port l4. It operates as follows.

In addition, a drain pipe 18 is installed hanging from the bottom of the tank 16 to the water absorption well P, and a lower open end 18A of this drain pipe l8 is installed.
The position of is set below the bottom open end 7 of the folded part 8. Next, the operation of the second embodiment will be explained. During submerged operation, pumped water does not flow from the discharge side casing 1l to the communication pipe 17, so pumping pressure does not act on the valve 13.
3 is open. Therefore, during submerged operation, if the water level is lower than the lowest ice level LWL that seals the lower open end 7 of the hanging part 10 in the branch pipe 3, and higher than the lower open end of the drain pipe 18, , through the lower open end 7 of the branch pipe 3, the intake port i4 and a part of the communication vl7 to the tank l6.
Since air is sucked into the impeller chamber 6 from the path that joins the branch pipe 3 within the tank, air operation continues without water being pumped up. Even if the water level reaches or near the lowest water level LWL that seals the lower open end 7 of the branch pipe 3 and no air is taken in from the lower open end 7, the valve 13
Since air is sucked into the impeller chamber 6 from a route that passes through a part of the communication pipe 17 and joins the branch pipe 3 in the tank 16, the air operation is continued without pumping water.

When the water level further rises and reaches the pumping start water level WL, the self-priming action of the impeller sucks in the remaining air in the suction side casing 2 and pumping starts.

Even if water pumping is started in this way, since the turned part 8 of the branch pipe 3 is set at a position higher than the suction lift due to the maximum load generated in the impeller chamber 6, the hanging part 1 of the branch pipe 3
0 and the drain pipe l8, water is sucked up to a height corresponding to the load of the impeller chamber 6 and is in a balanced state. Therefore, water is not sucked into the impeller chamber 6 through the branch pipe 3, so that the flow of water in the impeller chamber during pumping operation is not disturbed. During the pumping operation, pumped water flows into the communication /f17 from the discharge elbow IIB of the discharge side casing l1, and the pumping pressure closes the valve 13. The water flowing into this communication pipe 17 falls into the tank 16, and from there it falls into the drain pipe 18. Since the above-mentioned balance is maintained in the drain pipe l8,
A considerable amount of water that has fallen from the tank 16 to the drain pipe 16 is returned to the water absorption well P. Therefore, it is not sucked into the impeller chamber 6. Naturally, pumping operation continues through the suction side casing 2 when the water level is higher than the pumping start water level WL. Since the valve l3 is closed during the pumping operation, even if the water level falls during the pumping operation, until the water level falls to the lowest ice level LWL corresponding to the lower open end 7 of the branch pipe 3, Pumping operation will continue.

That is, even if the water level drops from above the pumping start water level WL to below the pumping start water level WL, the pumping operation continues. When the water level further falls below the lowest water level LWL and the water seal at the lower open end 7 of the branch pipe 3 is released,
Water that has been sucked up to a balanced height in the hanging part 10 and the drain pipe l8 falls into the water suction well P, and is sucked into the impeller chamber 6 from the lower open end 7 of the branch pipe 3 due to the load on the impeller chamber 6. The pumped water filling the suction side casing 2 is cut off by the intake air, and the operation is switched to air operation.

By switching to air operation, the above-mentioned pumping pressure no longer acts on the valve l3, so the valve l3 is opened and air is also taken in from the intake port l4 in the same manner as described above. In other words, the transition from submerged operation to pumping operation is at the pumping start water level W.
In contrast, the transition from pumping operation to submerged operation is performed based on the lowest water level LWL, and the transition between the pumping start water level WL and the lowest water level (pumping cutoff water level) LWL Since there is a predetermined height difference between the two, it is possible to reliably prevent the aforementioned hunting phenomenon. Note that when switching from pumping operation to submerged operation, part of the water that had been sucked up by the hanging part 10 to maintain balance is mixed with the intake air flow from the lower open end 7, resulting in a so-called intake air mixed flow. Although the air is sometimes sucked up as water, air and water are separated as it passes through the tank l6, and the water separated from the intake air is returned to the water intake well P via the drain pipe l8. Furthermore, even if the pipe line 15 (see FIG. 1) of the first embodiment is connected to the discharge elbow IIB of the discharge side casing 11, or the communication pipe 17 (see FIG. 3) of the second embodiment is connected to the discharge elbow IIB of the discharge side casing 11, Even if it is connected to the pumping pipe 11A of the side casing 1l, the same effects as described above can be achieved. [Effects of the Invention] Since the present invention is configured as described above, it produces the following effects. According to the vertical shaft pump of claim (1), the water level gauge, Tv. It eliminates the need for intake valves configured with valves and pneumatically operated valves, water level gauges, and sequence control devices to operate the intake valves, and eliminates the occurrence of air intake vortices and breathing phenomena that were previously a concern. This can be avoided and the pump can be left running at full speed. Moreover, a predetermined height difference is provided between the transition level to pumped storage operation at the lowest water level and the transition level to aerial operation at the pumping cutoff water level, and the transition from pumped storage operation to aerial operation is ,
Since the transition from submerged operation to pumped storage operation is performed based on different levels, it is possible to reliably prevent the hunting phenomenon caused by these transition phenomena being repeated in a short period of time. can. In addition, the vertical shaft pump of claim (2) also includes an intake valve that is controlled by a water level gauge, an electric valve, a pneumatically operated valve, etc., as well as a sequence control device for operating the water level gauge and the intake valve, as in the past. This allows the pump to operate at full speed and standby, avoiding the occurrence of air suction vortices and breathing phenomena, which were concerns in the past. Moreover, a predetermined height difference is provided between the transition level to pumped storage operation at the lowest water level and the transition level to aerial operation at the pumping cutoff water level, and the transition from pumped storage operation to aerial operation is ,
Since the transition from submerged operation to pumped storage operation is performed based on different levels, it is possible to reliably prevent the hunting phenomenon caused by these transition phenomena being repeated many times in a short period of time. can.

[Brief explanation of drawings]

Fig. 1 is a side view showing the first embodiment of the wooden invention, Figs. 2A and 2B are sectional views showing an example of the valve, Fig. 3 is a side view of the second embodiment, and Fig. 4 is the conventional valve. Explanatory diagram, FIG. 5 is an explanatory diagram of a comparative example. 2... Suction side casing 3... Inverted U-shaped branch pipe 6... Impeller chamber 7... Lower open end 8... Turned part 13... Valve l 4... Inlet port 1 7...Communication pipe LWL...Minimum water level patent applicant Kubota Iron Works Co., Ltd.

Claims (2)

[Claims] (1) An inverted U-shaped branch pipe with its lower open end set at or near the lowest water level of the vertical shaft pump is connected to the suction side casing that communicates with the impeller chamber, and an intake port into which air can be introduced A valve that is closed by the pumping pressure of the vertical pump and opened when the pumping is cut off is installed at the intake port, and the inverted U-shaped folded portion of the branch pipe is connected to the maximum negative A vertical shaft pump characterized by being set at a position higher than the suction head due to pressure. (2) An inverted U-shaped branch pipe with its lower open end set at or near the lowest water level of the vertical shaft pump is connected to the suction side casing that communicates with the impeller chamber, and this branch pipe and the discharge side casing of the vertical shaft pump are connected to each other. A communication pipe is provided to communicate with each other, and an intake port is provided in the communication pipe, which is closed by the pumping pressure of the vertical pump, and is opened when the pumping is interrupted to open and close the communication pipe to the atmosphere. A vertical shaft pump characterized in that an inverted U-shaped folded portion of the branch pipe is set at a position higher than a suction lift due to a maximum negative pressure generated in the impeller chamber.