JPH053757Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a centrifugal pump, and particularly to a self-priming centrifugal pump that can pump liquid without priming due to the self-priming action between the impeller and drainer. It is something.

[Prior Art] Generally, in actual use of a pump, the efficiency of use is best when the specifications of the pump match the specifications of the customer. However, in the manufacturing stage, it is practically impossible for a pump manufacturer to envision a wide range of arbitrary specifications in advance and manufacture each pump individually. Therefore, it is not uncommon for there to be a difference between the pump specifications and the customer's specifications, and it has been common practice to restrict the flow rate with a discharge valve using a pump with oversized specifications, knowing the energy loss.

However, in today's industry, where energy conservation is emphasized, some kind of countermeasure was desired, and one solution to this problem was to change the pump characteristics by reducing the diameter of the impeller. This is a diamond cut method that corrects differences between specifications, and because it is easy and economical to implement, it has become widely adopted today as a method for matching pumps and pipes.

[Problem that the invention attempts to solve]

However, although this diamond-cut method can be easily adopted in ordinary centrifugal pumps, it is not possible to apply the diamond-cut method as is in self-priming centrifugal pumps whose characteristic is self-priming between the impeller and drainer. is impossible.

In other words, as shown in Fig. 12, when a self-priming centrifugal pump starts operating with the water level in the casing 1 at the same position, the flow rate increases at C between the impeller 3 and drainer 2, and the pressure decreases. acts like a vacuum pump, the air in the water is precipitated, and the mixture of precipitated air and water is separated into water and air in the separation chamber 4, and the water falls due to the difference in specific gravity and is pumped from the recirculation hole 5. Through this continuous action, the air in the suction pipe 6 is discharged to the discharge side 7 for self-suction, and after completion of self-suction, the liquid pumping process normally begins.

The key to the self-priming performance of such a self-priming centrifugal pump lies in the interval C between the impeller 3 and the drainer 2, and the self-priming performance is greatly influenced by the interval C. During this time, the smaller C is, the greater the self-priming force is, and it is usually set to about 1 to 5 mm. However, during this period, the diameter of the impeller must be reduced.
This leads to an expansion of C, which leads to a reduction or loss of self-priming performance, and therefore, it has been impossible to apply the diamond cut method to self-priming centrifugal pumps.

Therefore, the purpose of this invention is to make the diamond cut method applicable to a self-priming centrifugal pump in the same way as a normal centrifugal pump.

[Means for solving problems]

As mentioned above, the problem with the diamond cut in self-priming centrifugal pumps is that it inevitably leads to an increase in C between the impeller and the drainer. As a result of consideration, we came up with the idea of reducing the time that had been expanded by the diamond cut to a time that could maintain the original self-priming performance by interposing a drainage pin as a separate member in C. be.

In other words, a drain pin was installed in the enlarged space between the impeller and the drainer whose diameter had been reduced by a diamond cut, and by narrowing the distance between the drain pins, self-priming performance was ensured. The drainage pin preferably has a cylindrical shape with low resistance to fluid, and can be attached by detachably screwing onto the casing cover at its base. It goes without saying that there should be a gap between the impeller and drain pin to ensure self-priming performance, but by adopting a two-pass structure with a gap between the drain pin and a bypass. , Self-priming: Alleviates and reduces the unpleasant noise peculiar to pumps when the pump is in operation. The features of this invention will become clearer from the following description based on the examples.

〔Example〕

Figures 1 to 3 show an embodiment of the self-priming centrifugal pump according to this invention.
Parts equivalent to those in the figure are indicated by the same reference numerals. That is, 1 is the casing, 2 is the drainer, 4 is the separation chamber,
5 is a recirculation hole, 6 is a suction pipe, and 7 is a discharge side.

3' is an impeller whose diameter has been reduced by a diamond cut, and a cylindrical drain pin 8 is installed between the impeller and the drainer 2, which has been enlarged by this diameter reduction, to narrow the gap. The pin 8 is removably screwed onto the casing cover 9 at its base.

To explain in more detail with reference to FIG. 3, the cylindrical drain pin 8 has a tip of the drainer 2 near the end of the drainer 2, more specifically, approximately the center of the pin, and a tip of the drainer 2.
Located on the connection with the center O of the impeller 3',
It has a two-pass structure with a gap 〓C' between it and the impeller 3' and a gap 〓E between it and the drainer 2.

Figure 4 is a diagram equivalent to Figure 3 before diamond cutting.
Here, we conducted a comparative experiment on the changes in characteristics of the pump before and after the impeller 3' is diamond-cut, that is, the characteristics changes and self-priming performance of a normal self-priming centrifugal pump and a self-priming centrifugal pump that is diamond-cut and equipped with a drain pin 8. As a result, the results shown in FIGS. 5 and 6 were obtained. The pump used is caliber 80A/
80A, rotation speed 1750rpm, the diameters of the impeller before and after the diamond cut are 274m/m and 245m/m, respectively.
It is. Between C before diamond cutting and between draining pin 8 and impeller after diamond cutting
C' are equal, both are 3 m/m, the distance between the drain pin 8 and the drain pin 2 is 2.5 m/m, and the diameter of the drain pin is 12 m/m.

First, in Fig. 5, A and B' indicate (total head - discharge amount) curves, B and B' indicate (shaft power - discharge amount) curves, and A and B shown by solid lines are the self-priming curves of this example. 〓
The broken lines A' and B' indicate a self-priming centrifugal pump before the diamond cut (impeller diameter 274 m/m). As is clear from the graph, the changes in the curves are similar changes, and this shows that the diamond cut causes changes in pump characteristics, that is, changes in pump specifications, with almost constant fluctuation values.

On the other hand, Figure 6 shows the comparison results of self-priming force, and shows the vacuum degree vs. time (sec.) (a comparison of the relationship between the generated vacuum level and time when the suction side valve is closed, which is a guideline for self-priming force). It is a curve. Here, the solid line C shows the self-priming centrifugal pump of this embodiment, and the broken line C' shows the self-priming centrifugal pump before diamond cutting. As is clear from the graph, there is almost no change in the self-priming force before and after the diamond cut. In other words, it has been demonstrated that the self-priming performance before diamond cutting is not impaired at all by the action of the drain pin.

FIG. 7 shows that the principle of this invention can be applied to any change in the diameter of the impeller due to the diamond cut.As shown in the figure, for the impeller 3'' whose diameter is D due to the diamond cut,
It is sufficient to use a draining pin 8' that satisfies C''=C' while E is constant, and it is sufficient to cope with various changes.

In the above, a two-pass structure in which gaps 〓C' and E are provided on both sides of the drain pin 8 has been explained, but as shown in Fig. 8, a 1-pass structure in which a gap 〓C' is provided only on the impeller 3' side is explained. There is no problem in terms of the structure as well, in that it enables a diamond cut that maintains the self-priming function. Figures 9 and 10 show the performance of the 2-pass structure (solid line) in Figure 3 and the 1-pass structure in Figure 8.
This is a comparison of the performance of the pass structure (dashed line), except that the diameter of the drainage pin 8 in the one-pass structure was increased by the distance E in the two-pass structure to 14.5 m/m. The design is similar to the test example. As is clear from the comparison of (total head - discharge amount) curves A and D and (degree of vacuum - time) curves and F' in the drawing, there is almost no difference in their performance, and it is possible to achieve the objectives in the same way. it is obvious. However, as can be seen from the (noise-discharge amount) curves H and H' in FIG. 9, it was found that the two-pass structure was superior in noise reduction effect. This 2
The noise reduction effect of the pass structure is extremely preferable as it alleviates and reduces the unpleasant noise that is characteristic of this type of self-priming pump during pump operation. Conventional, especially high-head self-priming centrifugal pumps emit an unpleasant high-frequency sound over the entire area during pump operation, but with a two-pass structure, the noise is limited to only near the cutoff. The noise range has become narrower, and the sound quality has changed to a relatively dull and soft sound quality, and the noise reduction effect, which had been a problem in the past, has also been achieved. This noise reduction effect in the two-pass structure is understood to be the mitigation of cavitation noise generated in the fluid flowing at high speed between the impeller and the water cutter. That is, this is due to the fact that the bypass fluid passing between the drain pin and the drain relieves the cavitation generated in the fluid that passes between the drain pin and the impeller.

As for the installation position of the drain pin, as described above, the most preferable self-priming force is obtained near the edge of the drain, and the self-priming force decreases as it moves away from the edge of the drain along the outer periphery of the impeller.

As for the shape of the draining pin, a cylindrical one is effective, and has the advantage of having no directionality when attached and being easy to handle, but it is not necessarily limited to this. For example, as shown in Fig. 11, when the droplet-shaped draining pin 8'' is set near the end of the drainer (two positions are shown in the drawing), total head - discharge amount, shaft power - discharge amount. Comparing both the degree of vacuum and the time (sec.), the results were almost the same as those of the cylindrical drain pin, and it was found that it is applicable.However, the noise reduction effect is lower than that of the cylindrical drain pin. Ping was better.

Various materials can be used for the draining pin, and when the target is a slurry liquid, a hard material such as cemented carbide or ceramic, or a soft rubber coating material can be used.

The drain pin is designed to be removable, such as by screwing it onto the casing cover at the base, so that it can be replaced as necessary, such as when it is eroded by slurry liquid, and can be used for a long period of time. This has the advantage of ensuring self-priming power. Furthermore, the same applies not only to screwing but also to fitting structures.

[Effect of idea]

As described above, the self-priming centrifugal pump according to this invention is capable of applying a diamond cut, which has been impossible until now, by interposing a draining pin between the impeller whose diameter has been reduced by a diamond cut and the drain. Of course, the original self-priming performance is not impaired at all, and the diamond cut allows it to be easily adapted to customer specifications, resulting in a large energy-saving effect. Furthermore, by providing this drainage pin, the unpleasant noise peculiar to self-priming pumps during pump operation was alleviated and reduced, making it possible to provide a self-priming whirlpool pump with extremely high practical value. .

[Brief explanation of the drawing]

Fig. 1 is a partial longitudinal cross-sectional view of an embodiment of the self-priming centrifugal pump according to this invention, and Fig. 2 is a -
3 is an enlarged view of the main parts of this example, and FIG. 4 is a schematic cross-sectional view taken along the line, FIG.
5 and 6 are comparison graphs of the characteristics and self-priming performance of the conventional pump and the pump of this embodiment.
Fig. 7 is a state diagram showing that this invention can accommodate changes in impeller diameter, Fig. 8 is an enlarged view of the main part of another example (one-pass structure), and Figs. 9 and 10 are examples of this embodiment and others. Comparison graph of example characteristics and self-priming performance,
FIG. 11 is an enlarged view of the main part showing a modified example (water droplet shape) of the draining pin, and FIG. 12 is a schematic cross-sectional view of a conventional self-priming centrifugal pump. 2...Drainer, 3,3',3''...Impeller,
8, 8', 8''...Draining pin.

Claims (1)

[Scope of claim for utility model registration] (1) In the casing, the whirlpool chamber housing the impeller and the gas-liquid separation chamber are separated by a drainer,
In a self-priming centrifugal pump that has a self-priming effect between the impeller and the drainer and has a recirculation hole for separated water formed at the bottom of the swirl chamber, between the impeller and the drainer whose diameter has been reduced by a diamond cut, Near the end of the drainer,
There is a short distance between the drainer and the impeller.
A self-priming centrifugal pump characterized by having a cylindrical draining pin detachably attached to the casing cover. (2) The self-priming centrifugal pump according to claim 1, wherein the center of the drain pin is located on the connection between the tip of the drain pin and the center of the impeller.