JPS5928075A - Apparatus for preventing intrusion of air into pump - Google Patents

Abstract

PURPOSE:To prevent intrusion of water into a pump, by forming a suspension wall around a pump set in a water intake tank having a free water surface so as to form a closed space above the water surface, and communicating the closed space with the atmosphere only via a check valve so that the water level in the closed space is kept always higher than the free water surface. CONSTITUTION:A water intake tank comprises an outer wall 1, a pump 2 and a swirl preventing plate 3, and water is supplied from an external water source to the tank via an intake passage 4. Here, a depending wall 8 is formed to depend downward from the lower surface of the base of the pump disposed at an upper portion of the intake tank, so as to form a closed space 9 defined by the depending wall 8, other wall surfaces and water surface 14 around a suction casing. The closed space 9 is communicated with the atmosphere only via a pipe 11 having a check valve 10. By employing such an arrangement, when the water level 25 of the free water surface 5 at the intake passage 4 is raised, air in the closed space 9 is discharged to the outside via the pipe 11, so that the water level 24 of the water surface 14 is also raised. On the other hand, when the level 25 of the water surface 5 is lowered, the water level 24 of the water surface 14 is kept high since intrusion of air into the closed space 9 is prevented by the check valve 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an air intake prevention device when water is taken from a water intake tank with a free water surface by a pump.

Technical background of the invention and its problems] One of the representative water intake tanks having free water (full) is the water intake tank for a water tank cooling water pump in a steam power plant. An example of the conventional structure of this water intake tank is shown in FIG. In Fig. 1, the water intake tank has an outer wall 11, a pump 2, and a vortex 01 [
It consists of a prevention plate 3, and water is supplied from an external water source through an intake channel 4. The water level of the intake channel free water surface 5 is determined by the state of the external water source and the operating state of the pump 2.

In the conventional water intake tank, the vortices caused by the rotation of the blades of the pump 2 during operation of the pump 2 and the vortices caused by the approaching speed of water from the intake channel 4 are caused by the shape and dimensions of the water intake A, v, The pump 2's position ft't l shows a complicated warping pattern due to various interferences depending on conditions such as the water level of the free water surface 5. If these conditions are bad, a large vortex 6 is formed near the suction casing 2a of the pump 2, and the vortex threads 7 intersect with the free water surface, as shown in Figure 2 (2), and the vortex threads 7 intersect with the free water surface. In such a state, the pump 2 not only generates abnormal vibrations and noise, but also becomes inoperable in the worst case.

Various efforts have been made to eliminate these problems, and the eddy current prevention plate 3 is one of the effective devices. However, even if this method is used, it is impossible to prevent continuous intake of air due to the vortex in water intake tanks of all shapes. Even if there is a shape for the water intake tank or the shape of the eddy current prevention plate 3 that prevents the pump 2 from sucking air, determining such a shape is generally not possible through analysis alone, and is based on models, etc. Experimentation is essential and requires significant expense.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an air suction prevention device for a pump that prevents the pump from continuously suctioning air due to vortexes, regardless of the shape of the water intake tank, in view of the drawbacks described in B12 above.

[Summary of the Invention] To achieve the above object, the present invention shields the periphery of the suction casing of a pump attached to the upper surface of the outer wall of the water intake tank having a free water surface with a hanging wall to form a closed space above the water surface. It is characterized by communicating the closed space with the atmosphere via a check valve.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 3, a hanging wall 8 is provided that extends downward from the lower surface of the pump foundation at the top of the water intake tank, and a closed space 9 separated by other walls and the water surface 14 around the suction casing 2a is provided with a non-returning wall. Communication with the outside air is provided only by a pipe 11 with a valve 10. The check valve 10 is installed so that outside air can flow from the closed space 9. Further, the base circumference υ of the pump 2 is provided with a seal 12 to prevent leakage between the closed space 9 and the outside air through the gap around the pump. The sea level in the open ocean of the hanging wall repeats ebb and flow twice in one day, and the water level 25 at the free water surface 5 of the intake channel also repeats its rise and fall. During this period when the water level 25 increases from a low state to a high level, the water level 14 around the pump forming the closed space 9 also tends to rise. Therefore, check valve 10. The air in the closed space 90) is exhausted through the pipe 11, and the water surface 14 around the pump is discharged.
The water level 24 also increases. On the other hand, water level 2 of intake channel free water surface 5
During the period when 5 goes from high to low, the water level around the pump 1
4 also tries to descend, but air does not flow into the closed space 9 from the outside air due to the action of the check valve 10, so the water level 24 of the water surface 14 around the pump remains high. This situation shows water level 25 of the free water surface of the intake channel and water level 14 of the water surface around the pump.
Fig. 4 shows the time chart. In other words, the water level 14 of the water surface around the pump is always the water level 2 of the free water surface of the intake channel.
It is maintained at about the highest water level of 5.

The air suction vortex 6 of the pump 2 is more likely to occur as the water level is lower, and there are more air suction ridges. Therefore, if the water level 24 around the pump is always high, air suction vortices will not occur.

Further, suppose that outside air enters the closed space 9 due to a malfunction of the seal 12, and the water level 24 around the pump drops to the water level 25 of the free water surface of the intake channel. At this time, even if the air suction vortex 6 is generated and air starts to be sucked in continuously, the amount of air existing in the closed space 9 is limited, so as the air suction vortex 6 sucks in air, the water surface 14 around the pump will increase. The air suction vortex 6 rises and eventually disappears.

The hanging wall 8 has the function of reducing the speed of the water flow near the free water surface 5 of the intake channel, so the hanging wall 8 also has the function of reducing the air suction vortex 6.
It is effective in preventing the occurrence of

〔Effect of the invention〕

As described above, according to the present invention, air intake by the pump can be prevented with simple equipment in any shape of water intake tank having a free water surface, and if the pump is designed taking this effect into consideration, It is also possible to reduce the submersion depth of the pump and shorten the length of the suction.

[Brief explanation of the drawing]

Figure ffK1 is a cross-sectional view showing an air suction prevention device of a typical pump for a water tank with a free water surface, which has been conventionally used.
Fig. 2 is a cross-sectional view showing how a vortex is generated in a conventional water intake tank and how the pump sucks air; Fig. 3 is a cross-sectional view showing an embodiment of the pump air suction prevention device according to the present invention; The figure shows the curve factor showing the ashing between the water level of the free water surface of the intake channel and the water level of the water surface around the pump. 1... Water intake tank outer wall 2... Pump 5... Free water surface 8... Hanging wall 9... Closed space
10...Check valve 11...Piping 2a...
・Suction casing (7317) Representative Patent attorney Chika
Kensuke (and 1 other person) Figure 4

Claims (1)

[Claims] A closed space is formed above the water surface by shielding the periphery of the suction casing of the pump attached to the upper surface of the outer wall of the water intake tank with a free water surface by a hanging wall, and this closed space is communicated with the atmosphere via a check valve. A pump air suction prevention device featuring: