JPH0826869B2 - Vertical pump - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vertical shaft pump capable of performing full speed operation regardless of water level.

[Conventional technology]

Conventional vertical pumps that have been installed in pump suction wells of drainage pumping stations, when a water level is lower than a certain level, generate vortices and suck water containing air even if the suction port is underwater. There is a peculiar minimum water level (operable minimum water level) for each pump, and there is a characteristic that vibration and noise are generated when the pump is operated when the water level does not reach this minimum water level. Therefore, if such a general vertical axis pump is operated at full speed regardless of the water level of the water intake well and is put on standby for unexpected water discharge (full speed standby operation), the water level is below the minimum water level above. Occasionally, violent vibration or noise may occur, which may cause a pump operation dysfunction or damage to the foundation or building. Therefore, in a conventional general vertical axis pump, an operation system is adopted in which full speed standby operation is not performed, operation is performed only when the water level is higher than the minimum water level, and operation is stopped when the water level is lower than the minimum water level.

However, in recent years, the water retention function of the strata has declined due to an increase in the pavement rate and a decrease in green space due to the progress of urbanization, while the inflow of water into the above-mentioned water intake wells and the like tends to increase. Moreover, a large amount of water often suddenly and suddenly flows into the intake well like a so-called flash flood.
Therefore, the water level changes in a short time in water intake wells, etc., and it is difficult to precisely control the operation start timing and operation stop timing of the vertical axis pump with the above-mentioned conventional general vertical axis pump operation system, and the abnormal rise of the water level There was a concept that caused situations such as flooding and abnormal deterioration of pump operation.

Therefore, the applicant of the present application has proposed, in Japanese Patent Application No. Sho 61-280967, a vertical shaft pump capable of performing stable full speed standby operation regardless of whether the water level is higher or lower than the minimum water level.

As shown in FIG. 3, this vertical pump communicates with a suction casing 2 at the front (upstream side) of a pump impeller 1 through a branch pipe 3 which is far smaller in diameter than its suction port and is open to the atmosphere. At the same time, the electric intake valve 4 is interposed at the tip of the branch pipe 3, and the electric intake valve 4 is controlled to be opened / closed by a signal from the water level detector 5.

This vertical shaft pump is operated at full speed standby. When the water level of the water intake well P rises from a lower level than the lowest water level, while the water level detector 5 detects that the water level has not reached the lowest water level, the electric intake valve 4
Is opened, and when the water level detector 5 detects that the water level of the water intake well P has reached the above-mentioned minimum water level, the electric intake valve 4 is controlled to close, and branching is performed until the water level reaches the above-mentioned minimum water level. The pump 3 is sucked into the impeller chamber 6 from the pipe 3 and pumping is not performed, and so-called full-speed operation in the air continues reasonably, while the branch pipe 3 is used after the water level reaches the minimum water level.
Intake from the impeller chamber 6 is stopped and water is pumped,
Normal pumping operation is performed.

On the other hand, when the water level of the intake well P is lower than the uppermost water level, the electric intake valve 4 is closed while the water level detector 5 detects that the water level has not reached the lowest water level. Pumping operation is continued as it is. When the water level detector 5 detects that the water level has reached the minimum water level, the electric intake valve 4 is opened, air is sucked into the impeller chamber 6 through the branch pipe 3 with a small diameter, and pumping is interrupted, which causes air in the air. Switch to driving.

Therefore, this vertical shaft pump enables full-speed standby operation that can cope with sudden rise and fall of the water level, and prevents the above-mentioned flooding and abnormal drop of pump operation dysfunction due to the abnormal rise of the water level. It becomes possible to do.

[Problems to be Solved by the Invention]

However, the water level detector 5 used in this vertical shaft pump is easily affected by water quality and dust.
This is one of the most important issues in view of the fact that the vertical shaft pump is required to be able to cope with accidental water discharge and the like. Further, the electric intake valve 4 requires an external drive source and sequence control for operating it.

In view of such circumstances, the applicant of the present application further discloses, in Japanese Patent Application No. 1-113193, a stable full-speed standby operation regardless of whether the water level is higher or lower than the minimum water level without using a water level detector or an electric intake valve. We proposed a vertical pump that can be operated.

As shown in FIG. 4, the branch pipe 3 has an inverted U-shape, and the lower open end 7 is set at the same level as or close to the minimum water level LWL. The folding | returning part 8 of 3 is set to the position higher than the suction lift by the maximum negative pressure which arises in the suction part of the impeller chamber 6 when the impeller 1 is driven at full speed.

In this vertical shaft pump, when the water level of the water intake well P rises from a lower level than the lowest water level LWL during full speed operation, when the water level does not reach the lower open end 7, the lower open end 7 Since it is sucked into the impeller chamber 6 from the branch pipe 3 through the branch pipe 3, pumping is not performed, and so-called full-speed operation in air continues reasonably, while the water level is the above-mentioned minimum water level LW.
When reaching L, the lower open end 7 is water-sealed, so that the residual air in the suction casing 2 and the branch pipe 3 including the bell mouth 9 is sucked in, and the pump is immediately switched to the pumping operation to completely remove the residual air in the suction casing 2. When it is sucked into the water, a complete pumping operation is performed. Since the folded-back portion 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 impeller is provided in the hanging portion 10 of the branch pipe 3 during the pumping operation. Since water is sucked up by a height corresponding to the negative pressure of the chamber 6 and is in a balanced state, the impeller chamber 6 from the branch pipe 3 does not absorb the water, and the water is sucked up through the suction casing 2 and smoothly pumped. Driving is done.

On the other hand, when the water level of the suction well P is lower than the uppermost water level LWL during full speed operation of the vertical shaft pump, if the water level does not reach the lower open end 7, the lower open end 7 is The pumping operation is continued because it remains sealed, and water is sucked up by the hanging portion 10 of the branch pipe 3 by a height corresponding to the negative pressure of the impeller chamber 6 and is in a balanced state. . When the water level reaches the minimum water level LWL, when the water seal of the lower open end 7 of the branch pipe 3 is released, the hanging part 10
Since the water sucked up by the water drops to open the branch pipe 3 over the entire length, air is sucked into the impeller chamber 6 from the lower open end 7 through the branch pipe 3, and the suction casing 2 and the like are sucked along with the suction. The filled water is shut off and the operation is immediately switched to air operation.

With this vertical axis pump, it becomes possible to stand by as a pump full speed operation state against sudden rise and fall of the water level, and the above-mentioned flood and abnormal drop of pump operation due to abnormal rise of the water level can cause functional problems. It is possible to prevent this, and at the same time, the water level detector 5 explained in FIG.
Since there is no need to use the electric intake valve 4 or the electric intake valve 4, there is no problem that the water level detector 5 is adversely affected by water quality or dust, and there is no problem that the control device becomes a little complicated, and it is possible to reliably handle accidental water discharge. Will be able to.

However, in the vertical pump of Fig. 4, the minimum water level LW
When the fluctuation speed of the water level near L is slow or the minimum water level LWL
If the water surface is wavy near the branch, branch pipe 3
The opening area and opening time of the lower open end 7 when the lower open end 7 is exposed to the atmosphere are repeated many times within a short period of time such that the lower open end 7 is exposed to the atmosphere. May be insufficient. When such a situation occurs, a so-called hunting phenomenon occurs in which insufficient intake of air into the impeller chamber 6 by the branch pipe 3 is intermittently performed within a short time, and a so-called hunting phenomenon occurs. There is a concern that switching from driving to aerial driving may not be performed smoothly and an unreasonable force may be applied to the impeller 1 to cause a pump functional disorder. This hunting phenomenon occurs remarkably when the water level of the suction well P or the like falls from a level higher than the lowest water level LWL and switches from pumping operation to air operation. This is performed on the basis of the level of the lower open end 7 where the transition between the air operation and the pumping operation during the full speed standby operation is set to the same level as the above-mentioned minimum water level LWL or a level in the vicinity thereof. In addition, if the opening area and the opening time of the lower open end 7 are insufficient, it is not possible to secure the air intake amount necessary for promptly interrupting the pumping that has been performed up to that time in the intake casing 2.

The present invention has been made in view of the above circumstances, by making the transition from the aerial operation to the pumping operation and the transition from the pumping operation to the aerial operation based on different levels, An object of the present invention is to provide a vertical shaft pump capable of preventing the above-mentioned hunting phenomenon from occurring while maintaining the full speed standby operation performance of the vertical shaft pump described in FIG.

[Means for solving the problem]

In the vertical shaft pump of the present invention, a U-shaped blood vessel portion is extended to a hanging portion of an inverted U-shaped branch pipe connected to a suction casing communicating with the impeller chamber, and an upper portion of the curved pipe portion is opened. The end is set higher than the lowest water level of the vertical pump, and the level of the turning point of the curved pipe section is set between the level of the upper open end of the curved pipe section and the lowest water level. The inverted U-shaped folded portion of the branch pipe is set at a position higher than the suction head due to the maximum negative pressure generated in the impeller chamber, and the branch pipe has a pipe line when the water level is equal to or higher than the minimum water level. It is characterized in that the entire middle part of the is configured to be shielded from the outside air. Here, the "branch pipe is configured so that when the water level is equal to or higher than the above-mentioned minimum water level, the entire middle portion of the pipe line is blocked from the outside air."
Means that when the water level is lower than the minimum water level, a part of the middle part of the branch pipe is connected to, for example, the drain pipe and the outside air However, when the water level is above the minimum water level, it is not possible to adopt a configuration in which even a part of the middle part is open to the outside air. It will be apparent from the examples described later.

〔Example〕

1A, 1B and 1C show a vertical pump according to an embodiment of the present invention.

This vertical shaft pump is located in front of the pump impeller 1 (upstream side).
A branch pipe 3 having a diameter much smaller than that of the suction port is made to communicate with the suction casing 2 of the above, and the branch pipe 3 is formed in an inverted U shape, and a U-shaped bent pipe is provided in a hanging portion 10 of the branch pipe 3. The part 11 is extended, and the upper open end 12 of the curved pipe part 11 is set higher than the minimum water level LWL of the vertical shaft pump, and the level of the upper open end 12 and the minimum water level LWL are The level of the turning point 13 of the curved pipe section 11 is set between them. The minimum water level LWL here has the same meaning as explained at the beginning, and when the water level is lower than a certain level, a vortex is generated and water containing air begins to be sucked in even if the suction port is in water. It means the water level peculiar to each pump. In addition, the folded portion 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.

A closed tank 14 is interposed in the horizontal pipe forming the folded portion 8 of the branch pipe 3, and the lower open end 16 of the drain pipe 15 which is lowered from the closed tank 14 is higher than the lowest water level LWL. It is set lower.

Further, the discharge casing 17 on the rear side (downstream side) of the impeller chamber 6 and the hanging portion 10 of the branch pipe 3 are connected by a communication pipe 18, and an opening / closing 19 is interposed in the communication pipe 18.

[Work]

Next, a case where the water level of the water intake well P rises from a lower level of the lowest water level LWL and a case where the water level falls from a higher level of the lowest water level LWL will be described separately while the on-off valve 19 is closed.
The following description is for a case where the vertical pump is in the full-speed standby operation.

(1) When the water level rises from below the lowest water level LWL When the water level W ₁ does not reach the lower open end 16 of the drain pipe 15 as shown by the phantom line in FIG. Since the upper open end 12 and the lower open end 16 of the drain pipe 15 connected to a part of the middle portion of the branch pipe 3 are open,
Depending on the negative pressure of the impeller chamber 6, as shown by arrows a and b, from the open ends 12 and 16, the curved pipe portion 11, the drain pipe 15, the branch pipe 3, the closed tank 14, the branch pipe 3 and the suction casing 2 are shown. Since the air is sucked into the impeller chamber 6 through the communication port 20 with, the pumping is not performed and the aerial operation is reasonably continued.

When the water level reaches the lower open end 16 of the drain pipe 15, the lower open end 16 is water-sealed and the entire middle part of the branch pipe 3 is shielded from the outside air. Since it remains open, the impeller passes through the upper open end 12, the curved pipe part 11, the branch pipe 3, the closed tank 14, and the communication port 20 as indicated by the arrow a depending on the negative pressure of the impeller chamber 6. Since the air is taken into the chamber 6, the pumping is not carried out and the air operation is continued smoothly. Such air operation is continued until the water level reaches the upper open end 12 of the curved pipe section 11. The state in which the entire middle portion of the branch pipe 3 is shielded from the outside air as described above is
It may be achieved when the water level reaches the minimum water level LWL.

As shown by the phantom line in FIG. 1B, the water level W ₂ reaches the upper open end 12 of the curved pipe section 11, and water is introduced from the upper open end 12 into the curved pipe section 11 due to gravity or the negative pressure of the impeller chamber 6. Inflow and curved pipe section
When the internal passages of 11 are water-sealed, the branch pipe 3 to the impeller chamber 6
Intake to the is cut off. At this time, since the folded portion 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 hanging portion of the branch pipe 3 is lowered.
At 10 the water is sucked up by a height H ₁ corresponding to the negative pressure of the impeller chamber 6, and the water is balanced. Since the water level W _{2 at} this time is higher than the above-mentioned minimum water level LWL, the negative pressure in the impeller chamber 6 causes the residual air in the suction casing 2 to be rapidly sucked into the pumping operation to completely remove the residual air. When it is sucked into the water, a complete pumping operation is performed. Therefore, in the following description, the water level at the same level as the upper open end 12 of the curved pipe section 11 is referred to as the pumping start water level WL ₂ .
This water level WL ₂ corresponds to the operation start water level (that is, pumping start water level) HWL of a general pump.

When the water level W ₃ is higher than the pumping start water level WL ₂ as shown in Fig. 1C, the smooth pumping operation is performed similarly.

(2) When the water level falls from above the lowest water level LWL When the water level does not reach the pumping start water level WL ₂ , the pumping operation up to that point is continued. The same applies when the water level reaches the pumping start water level WL ₂ .

The water level is the pumping start water level WL ₂ and the turning point 13 of the above curved pipe section 11
When reaching the water level between the water column W and the water column W, for example, when reaching the water level W ₄ shown by the imaginary line in FIG. The water level drops by ΔH _1, while the water level of the water column in the drooping part 10 of the branch pipe 3 is ΔH ₂
Just rise. In this case, assuming that the pumping amount does not change due to the fluctuation of the water level and the internal passage diameters of the branch pipe 3 and the curved pipe portion 11 are the same in each portion, the relationship of ΔH ₁ = ΔH ₂ = ΔH / 2 is established. Therefore, the water level is the pumping start water level WL ₂ and the curved pipe section 1 above.
Even when it reaches between the turning point 13 of 1 and the water column of the hanging part 10 of the branch pipe 3, the water is sucked up by a height H ₂ corresponding to the negative pressure of the impeller chamber 6, and the water column is in a balanced state. The part 11 remains sealed with water and the pumping operation is continued.

Water wells P water level further down in the [Delta] H _3/2 = water level of the water column in the upper open end 12 of L become water level WL within the curved pipe portion 11 becomes to ₁ position indicated by W ₅ in FIG. 2, i.e. songs When reaching the turning point 13 of the pipe portion 11 and further lowering it slightly, the balance of the water column formed over the curved pipe portion 11 and the hanging portion 10 of the branch pipe 3 is lost, and the water in the curved pipe portion 11 is lost. The seal is released. When the water seal is released in this way, air is sucked from the upper open end 12 of the curved pipe portion 11 due to the negative pressure of the impeller chamber 6, and the curved pipe portion 11, the closed tank 14, the branch pipe 3, the communication port. Air is taken into the impeller chamber 6 via 20 and the pumped water that fills the suction casing 2 and the like is shut off as the air is taken in, and the operation is swiftly switched to air operation. Therefore, in the following description, the water level at this time is referred to as the pumping cutoff water level WL ₁ . At this time, the water that forms the water column in the curved pipe portion 11 or the hanging portion 10 of the branch pipe 3 may be entrained in the air, but such entrained water is separated into air and water when passing through the closed tank 14. Then, it is returned to the suction well P through the drain pipe 15.

As is clear from the above description, in the above vertical shaft pump, the transition from the air operation to the pumping operation depends on the pumping start water level WL ₂
(I.e., the water level at the same level as the upper open end 12 of the curved pipe section 11) is used as a reference, while the transition from pumping operation to air operation is performed with reference to the pumping cutoff water level WL ₁ .
The water level WL ₁ is the same as or higher than the lowest water level LWL.
Moreover, the level difference between the water level WL ₁ and the pumping start water level WL ₂ is the same as twice the rising length L (see FIG. 2) on the upper open end side of the curved pipe section 11. Therefore, by setting the rising length L to an appropriate length, the occurrence of the above-mentioned hunting phenomenon can be prevented in advance.

In the vertical pump described above, there is a concern that dust may enter the curved pipe portion 11 for some reason and impair the water draining action at the turning point 13 (that is, the water draining action when the water column collapses). In order to eliminate this concern, the opening valve 19 is opened during the pumping operation, and part of the pumped water passing through the discharge casing 17 is opened through the communication pipe 18, the hanging part 10 of the branch pipe 3, and the curved pipe part 11 to open the upper part thereof. It is sufficient to let it flow out from the end 12 and clean the curved pipe section 11 accordingly. The on-off valve 19 is closed after cleaning. Even if some of the water flowing out from the communication pipe 18 flows into the folded portion 8 of the branch pipe 3, the water flows into the water intake well P from the drain pipe 15 through the closed tank 14. In the present invention, the drain pipe 15 and the closed tank 14 are not essential, and it is possible to omit them.In such a vertical shaft pump, the water level is at least the minimum water level or a position lower than the minimum water level. Irrespective of whether or not there is a condition, the entire middle portion of the branch pipe 3 is always shielded from the outside air.

〔The invention's effect〕

As described above, according to the vertical shaft pump of the present invention, while maintaining the full-speed standby operation performance of the vertical shaft pump described in FIG. 4 as it is, the pumping start water level for shifting from the air operation to the pumping operation and the pumping operation to the air operation. It is possible to maintain a certain level difference from the minimum water level (pumping cutoff water level)
It is possible to prevent the occurrence of the hunting phenomenon when the pumping is cut off. Therefore, according to the vertical shaft pump of the present invention, it is possible to make the pump stand by in a full-speed operation state even if the water level suddenly rises or falls, and of course, the water level is abnormal regardless of whether the water level fluctuation is fast or slow. It becomes possible to prevent floods due to rising and pump operation dysfunction due to abnormal decline. Further, since the water level detector and the electric intake valve described in FIG. 3 are not used, the structure is simple and the operation reliability is high, and it is possible to sufficiently cope with the sudden rise and fall of the water level. .

[Brief description of drawings]

1A to 1C are explanatory views of the action of the vertical shaft pump when the water level is rising, FIG. 2 is an explanatory view of a process of shifting from pumping operation to air operation, and FIG. 3 is an explanatory view of a conventional example. FIG. 4 is an explanatory diagram of a comparative example. 2 ... Suction casing, 3 ... Branch pipe, 6 ... Impeller chamber, 8 ... Folded part of branch pipe, 10 ... Hanging part of branch pipe,
11 …… bent pipe part, 12 …… upper open end of bent pipe part, 13 …… turning point of bent pipe part, 17 …… discharge casing, 18 …… communicating pipe,
19 ... Open / close valve.

Claims (2)

[Claims] 1. A U-shaped blood vessel portion extends from a hanging portion of an inverted U-shaped branch pipe connected to a suction casing communicating with the impeller chamber, and an upper open end of the curved pipe portion is provided. It is set higher than the minimum water level of the vertical shaft pump, and the level of the turning point of the curved pipe section is set between the level of the upper open end of the curved pipe section and the minimum water level. The inverted U-shaped folded-back part of is set at a position higher than the suction lift due to the maximum negative pressure generated in the impeller chamber,
The vertical shaft pump is characterized in that the branch pipe is configured so that the entire middle portion of the pipe line is blocked from the outside air when the water level is equal to or higher than the minimum water level. 2. A vertical shaft pump according to claim 1, wherein the discharge casing communicating with the impeller chamber and the hanging part of the branch pipe are communicated with each other by a communication pipe, and an on-off valve is interposed in the communication pipe. .