JPS59229093A - Pump pressure-feed system - Google Patents

Abstract

PURPOSE:To prevent cavitation in a cut-off valve and abnormal vibration and noise in a pump, by providing a bypass pipe having a check valve, for communicating one or both of a pump and a communicating pipe with a main discharge pipe. CONSTITUTION:A bellmouth 8 and a communication pipe 5 inserted in a pit 14 are connected, respectively to the suction and discharge sides of a pump 1 having an impeller 2 driven by a drive unit 3. A shut-off valve 11 and a check valve 12 are disposed in a bypass pipe 9 communicating between the top of the communication pipe 5 and the top of a main discharge pipe 6. When the level L of suction water lowers to such a degree that a pump 1 is stopped, a water cut-off valve 4 is fully closed. Since the pumping-up of water in a small amount is possible even if the water cut-off valve 4 is fully closed and therefore the level of suction water is regulated in accordance with the inflow rate of water, there is no risk of abrupt lowering of the level of suction water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pressure feeding system used in pumps such as horizontal shaft pumps and vertical shaft pumps.

[Background of the invention]

A conventional pressure system of this type, as shown in FIG. water valve 4
and a discharge main pipe 6 connected to a water stop valve 4, and a vacuum pump 7 is connected to the top of the pump l via an intake valve 13, and has a cutoff valve 11a, A bypass pipe 1oa communicating with the suction side of the impeller 2 is connected, while a cutoff valve 11b is provided at the lower part of the communication pipe 5,
A bypass pipe 1ob communicating with the bit 14 is also connected.

When pumping water using the above-mentioned pump 1, the normal operation is to detect the water suction level L and stop the operation of the pump 1 when the water level is below the specified level, and at the same time fully close the water stop valve 4. . However, recently, there has been an increase in the number of cases in which pumping operations are performed periodically for break-in operations during maintenance, even when not pumping water.

In this case, since the water suction level is not sufficient for pumping operation and there is often no inflow f, a means is employed to throttle the water stop valve 4 to suppress the discharge amount. However,
If the water stop valve 4 has a large diameter, it will not only be difficult to squeeze the water, but also cause cavitation in the water stop valve 4 and pump 1.
The above method is not preferred because it may generate abnormal vibrations and noise.

Therefore, as another means, as shown in FIG. 1, small-diameter bypass pipes 10a and 10b are provided to return part of the pumped water to the suction side. In this way, it is possible to perform break-in operation during maintenance even if the inflow volume and water absorption level are not sufficient.
It is difficult to control the small flow rate during normal pumping, and operations such as switching the shutoff valves 11a and llb provided in the bypass pipes 10a and 10b, respectively, during maintenance and regular pumping may be troublesome.

In addition, if the suction water level is not sufficient, there is a concern that air may be sucked from the bell mouth 8 inserted into the bit 14.
And since the water stop valve 4 is shut off, the intake air is
An air pocket is formed at the top of the pump 1 and the connecting pipe 5.

When this air pocket becomes large, the vacuum is broken and the water inside the pump falls out, which often causes the pump 1 to run dry and become unable to pump water.

On the other hand, the amount of flow varies considerably depending on location conditions, and in urban areas where the housing is narrow, there is no large reservoir in the suction tank, so the suction level often fluctuates greatly depending on pump operation. In this case, when the water suction level reaches the specified value T, the driving machine 3 is stopped and the water stop valve 4 is fully closed to completely stop pumping.
Depending on the amount of inflow, the water suction level will rise immediately, and the pump will have to start operating again. However, when the vacuum pump 7 is operated again, the water is filled up, the drive unit 3 is started, and the water stop valve 4 is fully opened, water can only be pumped up, so the startability is degraded. If the start-up υ is slow and takes a long time, the drainage area will be flooded, and the frequency of starting and stopping will increase abnormally, which has the disadvantage of shortening the life of the drive machine. .

[Purpose of the invention]

In view of the above, the present invention enables drainage of a small amount of water, prevents capitation of the water stop valve and generation of abnormal vibrations and noise of the pump, and prevents water in the pump from falling when the water suction level decreases. The purpose of this is to allow the drive machine to continue operating even when the water suction level is low, to respond quickly when the water level rises, and to suppress the frequency of startup and shutdown.

[Summary of the invention]

In order to achieve all of the above objects, the present invention provides the above-mentioned pressure feeding system comprising a pump, a water stop valve connected to the discharge side of the pump via a connecting pipe, and a main discharge pipe connected to the water supply valve. One or both of the pump and the connecting pipe are connected to the main discharge pipe via a bypass pipe, and the bypass pipe is provided with a check valve.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 1 is a pump having an impeller 2 driven by a driving machine 3, and a bell mouth 8 and a communication pipe 5 inserted into a bit 14 are installed on the suction side and the discharge side of the pump 1. each connected. 4 is a water stop valve attached to the communication pipe 5; 6 is a discharge main pipe connected to the water stop valve 4; 7 is a vacuum pump connected to the top of the pump 1 via the intake valve 13; 9 is the connection This bypass pipe connects the top of the pipe 5 and the top of the main discharge pipe 6, and the bypass pipe 9 is provided with a cutoff valve 11 and a check valve 12. Further, the bypass pipe 9 is connected to the thread path of the vacuum pump 7.

Next, the operation of this embodiment having the above structure will be explained.

When starting the pump 1, first, the intake valve 13 is fully opened to fill the inside of the pump 1 with water, and when the vacuum pump 7 takes in air and the pump 1 is filled with water, the intake valve 13 is fully closed. Next, when the drive unit 3 is started to rotate the impeller 2 and the water stop valve 4 is fully opened at the same time as water pumping starts, the pumped water in the pump 1 is pumped to the main discharge pipe 6.

When the water suction level is now lowered and reaches a level at which the pump 1 is stopped, the water stop valve 4 is fully closed. In this case, since the drive machine 3 is not stopped, it is operated at the intersection E of the 100%N Q-H% characteristic curve A and the bypass pipe resistance curve in the pump characteristic diagram shown in FIG. The amount of water pumped by the pump 1 at this time is Q2, and even if the water stop valve 4 is fully closed, it is possible to pump up a small amount of water of Q2, so there is a risk that the water suction level will drop rapidly in proportion to the inflow amount. Therefore, continuous operation of the pump 1 is possible without stopping the driving machine 3.

The diameter of the bypass pipe 90 is the same as that of the pump 1 or the connecting pipe 50 from the viewpoint of pumping a small amount of water, removing air, preventing the pump from shutting down, and preventing clogging of foreign matter contained in the pumped liquid.
It is preferable to use a small diameter of /10 to 115.

On the other hand, when the water stop valve 4 is fully closed and small water pumping is performed through the bypass pipe 9, the pumped water amount is Q in the characteristic diagram shown in Fig. 3.
If 2 is too thick, by changing the number of revolutions of the driving machine 30, Q is further shifted to the small water flow side Ql, so it is possible to control the flow rate. In addition, B and C in FIG. 3 respectively show the Q-H% characteristic curve and the pipe resistance curve of 80%N.

In FIG. 3, the number of revolutions corresponding to Ql is shown, for example, at the rated number of revolutions of 801 s. Depending on the pump, when the water stop valve 4 is fully closed and water is pumped through the bypass pipe 9, the shaft power increases compared to the rated point Qo near the valve shut-off operation, causing an overload on the drive machine. There is something that will become. However, if the pump rotation speed is lowered, the shaft power will decrease in proportion to the cube of the rotation speed reduction ratio, so changing the pump rotation speed is preferable as a countermeasure against overloading the drive machine. Sometimes.

〔Effect of the invention〕

As explained above, according to the present invention, there are various effects listed below.

(1) The small water lid can be drained during both regular water pumping operation and break-in operation during maintenance, resulting in cavitation of the water stop valve and abnormal vibration and noise of the pump. can be prevented.

(2) Even if the suction level is lowered, the water can be smoothly drained to the discharge side, and water in the pump can be prevented from falling.

(3) Even when the water suction level drops, the drive machine does not stop and continues to operate, allowing for a quick response when the water level rises.
Moreover, it is possible to suppress the frequency of starting and stopping.

[Brief explanation of drawings]

81 is a block diagram of a conventional pump pressure feeding system, FIG. 2 is a block diagram showing an embodiment of a pump pressure feeding system according to the present invention, and FIG.
The figure is a flow rate characteristic diagram of this embodiment. l...Pump, 4...Water stop valve, 5...Connection pipe, 6
...Discharge 1st (21%Z Fig. 4 vJ 3 Fig.

Claims (1)

[Claims] In a pressure feeding system consisting of a pump, a water stop valve connected to the discharge side of the pump via a communication pipe, and a main pipe connected to the water stop valve, one or both of the pump and the communication pipe and the discharge A pressure feeding system for a pump, characterized in that it communicates with a main pipe via a bypass pipe, and is equipped with a check valve in the bypass pipe.