JPH02291497A - Vertical shaft pump - Google Patents

Abstract

PURPOSE:To inhale the air by making a hole exposed on the water negative pressure even when the driving of the small amount of water, etc., is carried out, so as to perform vacuum destruction assuredly by providing a resistor on the upper side along the driving direction of an impeller of the hole for vacuum destruction communicating with the atmosphere. CONSTITUTION:To the lower part of a casing 2 with an impeller 1 internally installed, an inhelation bell-mouth 3 is connected, while to the upper part a column pipe 4 is connected, to the upper side of which a discharge elbow 6 provided with a discharge valve 5 is connected, so as to construct a pump main body. On a specified position of the pump corresponding to the lowest water level 'LWL', a straightening rib is projected as a resistor. On the lower side along the rotational direction of the impeller of the straightening rib 9, a hole 8 for vacuum destruction communicating with the atmosphere is opened. At the time of the driving of small amount of water or at the time of no- discharge operation, when the hole 8 is exposed on the water surface, the hole 8 is made negative pressure, whereby vacuum destruction is sure to be carried out by means of air inhelation from the hole 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a standing pump used in a pump intake well or rainwater pump equipment of a drainage pumping station installed mainly for draining waterways during floods. ．． Conventional technology Normally, this type of vertical shaft pump has a minimum water level at which it creates a vortex and sucks air when the water level of the pump suction well in which it is installed falls below a certain level, and this minimum water level If the temperature drops below this level, problems such as vibration and noise will occur due to air intake, so it is necessary to stop pump operation. However, due to an increase in the amount of rainwater runoff due to the increase in paving ratio due to the progress of urbanization in recent years, and a decrease in water retention function due to a decrease in green areas, rainwater flowing into pumping stations tends to flow in large quantities and rapidly.

On the other hand, because it is difficult to secure sufficient storage capacity of facilities such as pump water intake wells, it is difficult to plan accurate timing for pump operation, and there is an increasing demand for advance standby operation based on rainfall information. ing. However, as mentioned above, in order to perform advance standby operation in facilities where the water level in the pump intake well fluctuates rapidly, it is necessary to continue operation even when the water level is low. Therefore, the applicant previously filed an application (Japanese Patent Application No. 1983-236748) for a vertical shaft pump that can operate even when the water level is low. This vertical shaft pump has a hole that communicates with the atmosphere in the flow path upstream of the impeller.In this vertical shaft pump, when the water level in the pump suction well etc. becomes low, the hole rises above the water surface. If exposed, air is sucked into the pump through this hole and the vacuum is broken, causing the water inside the pump to fall and allowing air operation, preventing vortex suction and breathing phenomena, and reducing vibration and vibration. , which was intended to produce no noise.

Problems to be Solved by the Invention However, in the vertical shaft pump described above, when the operating point of the pump is on the low water flow side (approximately 50% or less of the water flow at the maximum efficiency point), the water level becomes low and the hole for vacuum breaking Even when there is a mist on the water surface, there is a large swirling flow due to the backflow from the impeller, and the centrifugal force creates a positive pressure in the vicinity of the hole, which may prevent vacuum breakdown. I understand.

The present invention solves the above-mentioned problems, and aims to provide a vertical pump that can reliably break the vacuum in the pump when the water level becomes low even when the bomb performs a small water flow operation or a shut-off operation. This is the purpose.

Means for Solving the Problems In order to solve the above problems, the present invention provides a resistor provided protrudingly in a flow path upstream of the impeller, and a resistor connected to the atmosphere in the impeller rotation direction. It has a vacuum breaking hole that opens toward the downstream side.

Effect With the above configuration, even when the pump performs small water flow operation or shut-off operation, when the water level drops and the vacuum breaking hole is exposed above the water surface, the vacuum that opens toward the downstream side of the resistor is released. The vacuum breaking hole becomes a negative pressure due to the swirling flow of the impeller, and air is sucked through the vacuum breaking hole to ensure vacuum breaking and switch to air operation without vortex suction or breathing phenomena.

Example Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a suction bell mouth 3 is located on the lower side, that is, upstream side, of a casing 2 that is internally installed with an impeller 1 being pivotally supported.
is connected to the pump body, and a lift pipe 4 is connected to the upper side, that is, the downstream side, and a discharge elbow 6 in which a discharge valve 5 is interposed is connected to the upper side of the lift pipe 4, thereby forming a pump body. There is. In addition, the impeller 1 is located above a specific part of the pump corresponding to the lowest water level LWL, which sucks air if the water level falls below this level when the pump is submerged in water, by a distance corresponding to the height of the impeller 1. The suction bell mouth 3 is arranged so that the suction port 3a at the tip thereof can be immersed in water to the necessary and sufficient extent in the specific part of the pump. Incidentally, the connecting pipe 7 may be removed and the suction bell mouth 3 may be lengthened by that amount. As shown in FIG. 2, a rectifying rib 9 as a resistor is protrudingly provided at approximately the same position with respect to a specific part of the pump corresponding to the lowest water level LWL, and a rectifying rib 9 is also provided. A vacuum breaking hole 8 communicating with the atmosphere is opened at a downstream side of the rectifying rib 9 in the direction of rotation of the impeller in the wall body. Note that the number of rectifying ribs and vacuum breaking holes is not limited to the numbers shown in Figure 2 and below. Further, 11 is a vacuum breaking pipe connected to the vacuum breaking hole 8. Next, the operation will be explained. In the region A where the submerged depth water level of the pump disposed in the water tank is above the lowest water level LWL, normal drainage operation is performed by the pumping action of the impeller 1. When the water level further decreases to below the lowest water level LWL, the vacuum breaking hole 8 is exposed above the water surface. Here, the operating point of the pump is discharge valve 5.
If the water flow is low or completely closed due to reasons such as
If the vacuum breaking hole 8 is simply provided, the swirling flow of the impeller 1 creates a positive pressure at the vacuum breaking hole 8, which prevents atmospheric air from being sucked in, and the vacuum may not be broken. As described in the above configuration, the vacuum breaking hole 8 has a rectifying rib 9.
Since it is provided on the downstream side in the rotational direction of the impeller, even in small water flow operation or shut-off operation, the vacuum breaking hole 8 has a negative pressure, and the atmosphere is reliably released from the vacuum breaking hole 8. It gets sucked in. Then, the water in the connecting pipe 7 and the suction bell mouth 3 falls due to the vacuum breakdown, and becomes unable to pump water, and air operation is performed. That is, in the water level region B shown in the figure, no vortex suction or breathing phenomenon occurs because the pump is operated in the air and no water is pumped up. Therefore, A, B
It is possible to perform stable operation with almost no vibration or noise in any of these areas. In addition, as shown in FIG. 3, the same effect can be obtained even if the rectifying rib 9 itself is provided with a vacuum breaking hole 12, and this vacuum breaking hole l2 is opened on the downstream side of the rectifying rib 9 in the direction of rotation of the impeller. Effects can be obtained.

Further, as shown in FIG. 4, the part where the vacuum breaking hole 21 is provided is made thick, and the upstream part of the vacuum breaking hole 21 in this part in the direction of rotation of the impeller is inward. Similar effects can be obtained by forming the baffle plate 22 as a resistor by protruding it. In addition, 23
2 is a vacuum breaking pipe connected to the vacuum breaking hole 21;
4 is a packing.

Furthermore, as shown in FIG. 5, the piping connected to the vacuum breaking hole 27 is a plug-in pipe 25, and the upstream side of the end of the plug-in pipe 25 in the direction of rotation of the impeller is made to protrude into the pump to form a baffle plate. 26 may be formed.

It should be noted that the present invention is not limited only to the above-mentioned embodiments, and it goes without saying that various embodiments are possible without departing from the scope of the claims.
A valve for opening and closing this hole may be provided so that the valve is closed during normal operation and opened and closed during standby operation.

Of course, the valve may be an electric valve, and the opening and closing may be controlled automatically according to the water level. In this case, it goes without saying that the vacuum breaking piping may be raised to the upper part of the floor and these valves may be installed above the floor.

Effects of the Invention As described above, according to the present invention, since the resistor is provided on the upstream side in the rotational direction of the impeller of the vacuum breaking hole communicating with the atmosphere,
Even when the pump performs small water flow operation or shut-off operation, when the water level drops and the vacuum break hole is exposed above the water surface, the vacuum break hole becomes negative pressure, and the vacuum break hole becomes negative pressure. Vacuum breakage is ensured by suction of air from the Therefore, in this case, it will automatically switch to air operation,
There is no vortex suction or breathing phenomenon, and vibration and noise can be significantly reduced. This allows standby operation to be performed without any problems, regardless of the pump's operating point.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of a vertical shaft pump according to an embodiment of the present invention, Fig. 2 is a plan sectional view of main parts of the vertical shaft pump, and Figs.
FIG. 5 is a plan sectional view of a main part of a vertical shaft pump according to another embodiment of the present invention. 1... Impeller, 2... Casing, 3... Suction bell mouth, 3a... Suction port, 8, 12, 21.
27... Vacuum breaking hole, 9... Rectifying rib (resistor), 22.26... Baffle plate (resistor). Agent Yoshihiro Morimoto Figure t Figure 2 Figure 4 Figure 5 Figure 21 - Vacuum breaching hole offshore 26 - 7-Year J plate (resisting body) 27 - - 8L section for empty hole joint back

Claims (1)

[Claims] 1. It has a resistor provided protruding into the flow path upstream of the impeller, and a vacuum breaking hole that communicates with the atmosphere and opens toward the downstream side of the resistor in the direction of rotation of the impeller. A vertical shaft pump featuring: