JPH1089279A - Single sectional type multistage pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for a temporary clamping work and to damp vibration through internal viscosity of water at the gap of an intermediate casing. SOLUTION: A single drum sectional type multistage pump comprises an impeller 3; a diffuser 12; a single sectional type intermediate casing 4; and a balance chamber 10 on the pump discharge side. An outer casing 15 is arranged at the outside of the intermediate casing 4, and a radially sealed gap 17 is produced between the intermediate casing 4 and the outer casing 15. The casing gap 17 is communicated with the suction flow passage of a suction casing 1 or the balance chamber 10. A sealant for the intermediate casing is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-body wheel-cut multistage turbine pump suitable for a boiler feed pump for a thermal power plant.

[0002]

2. Description of the Related Art A conventional single-body single-body wheel-cut multi-stage pump is a single-body wheel-cut type multi-stage pump in which a plurality of multi-stage assembled impellers are accommodated between a suction casing and a discharge casing. Are clamped and fastened by long tightening bolts. The impeller and the balance device are mounted on a rotating shaft that transmits power from a driving machine, and the rotating shaft rotates with both ends thereof supported by bearings.

[0003] A shaft sealing device is provided between the impeller and the bearing portion. A balance chamber is formed inside the shaft sealing device on the discharge side of the pump. The balance chamber and the suction casing are connected to each other. By connecting with a balance pipe, the axial thrust is balanced by using the pressure in the balance chamber as the pump suction pressure.

In the intermediate casing, a diffuser blade having a static pressure recovery function of converting a dynamic pressure component given by an impeller into an increase in static pressure and a water return blade having a rectifying function are sandwiched.

The fitting portions of the suction casing, the discharge casing, and the intermediate casing are usually sealed with a sealing material in order to prevent leakage of the liquid handled by the pump. As typical examples of the sealing material, an O-ring is used for low temperature, and a spiral gasket is used for high temperature and high pressure.

[0006] Such a single-body wheel-cut type multi-stage pump is described in "Hirebara Association Lecture 1" (edited by The Japan Society for Thermal Power and Nuclear Power Technology: published in April 1988).

[0007]

In the above-described conventional single-body wheel-cut type multi-stage pump, a spiral gasket or the like having a large interference is used as a sealing material for the intermediate casing. Since a part of the rotor of the impeller comes into contact with the intermediate casing due to the accumulation of the interference of the gasket and it becomes impossible to assemble, it is necessary to temporarily tighten the suction casing, the discharge casing and the intermediate casing before assembling the pump. It is getting bigger.

[0008] Further, the fluid to which dynamic pressure is given by the impeller of each stage is restored to the static pressure by the diffuser impeller, then rectified by the water return impeller and sent to the impeller of the next stage. Although the fluid is pumped downstream from the pump discharge port, in this pressure-increasing process, the fluid flowing out from the high-speed rotating impeller outlet interferes with the front edge of the diffuser blade and vibrates the entire diffuser blade. This vibration occurs in all stages of the intermediate casing, and this is a noise source. In a conventional single-body wheel-cut multi-stage pump, the intermediate casing is exposed to the outside.
There is a problem that noise is larger than that of a double-body type multi-stage pump having a thick outer casing.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a single-body, wheel-cut, multi-stage turbine pump capable of reducing costs and reducing noise.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-staged impeller, a diffuser blade for restoring the static pressure of a fluid, and a single-body, single-body-shape wheel-cutting machine. A single-body, wheel-cut, multistage pump having an intermediate casing, wherein an outer casing is provided outside the intermediate casing, and a radially sealed gap is formed between the intermediate casing and the outer casing. Is connected to the suction channel of the suction casing.

[0011] The object is to provide a multi-stage impeller, a diffuser blade for restoring the static pressure of a fluid, a single-body, single-body, wheel-cut intermediate casing. A single-body wheel-cut multi-stage pump including a balance chamber disposed between a balance device on the pump discharge side and a shaft sealing device, wherein an outer casing is formed outside the intermediate casing; This is achieved by making the space between the outer casing and the outer casing equal to the suction pressure of the pump.

By eliminating the sealing material between the intermediate casings, temporary tightening becomes unnecessary, and as a result, the assembly cost and material cost can be reduced.

Further, a part of the vibration energy is converted into heat energy due to the internal viscosity of the water in the casing gap, so that the vibration is attenuated and the noise can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view showing an embodiment of a single-body wheel-cut multistage pump according to the present invention. FIG. 2 shows a cross section of a fitting portion between the suction casing and the first stage intermediate casing of FIG. 1 or a cross section of a fitting portion between the discharge casing and the last stage intermediate casing.

In FIG. 1, reference numeral 1 denotes a suction casing, which has a fluid suction port, and reference numeral 2 denotes a discharge casing, which has a fluid suction port. Reference numeral 3 denotes an impeller assembled in multiple stages, and 4 denotes a single-body, single-body, wheel-cutting type intermediate casing having a wheel-shape shape. The impeller 3 is housed in each of the mold intermediate casings 4. Reference numeral 5 denotes a tightening bolt for sandwiching and fixing the intermediate casing 4 of the single body wheel cutting type. 6 is a balance device. Reference numeral 7 denotes a rotating shaft for transmitting power from a driving machine (not shown) to the impeller 3. Reference numerals 8a and 8b denote bearings, reference numerals 9a and 9b denote shaft sealing devices, and the bearings 8a and 8b and the impeller 3 respectively. A balance chamber 10 is formed between the discharge casing 9a and the shaft sealing device 9a. Reference numeral 12 has a static pressure restoring function of converting the dynamic pressure component given by the diffuser blade and the impeller 3 into an increase in static pressure. Reference numeral 13 denotes a water return blade, which has a function of rectifying fluid.

Reference numeral 15 denotes an outer casing, which is provided outside the intermediate casing 4. The outer casing 15 is sandwiched between the suction casing 1 and the discharge casing 2 similarly to the intermediate casing 4, and both ends thereof are a spiral gasket or the like. Completely sealed with the sealing material 16. A gap 17 (hereinafter, referred to as a casing gap 17) is formed between the outer casing 15 and the intermediate casing 4, and the casing gap 17 and the suction flow passage in the suction casing 1 communicate with each other through a suction-side communication passage 18. . This suction side communication passage 18 fills the casing gap 17 with water having a pressure equal to the low pressure pump suction pressure.

With the above configuration, it is not necessary to interpose a sealing material between the intermediate casings 4. The intermediate casings 4 are in metal contact with each other, so that even if a slight leak occurs from each fitting portion of the intermediate casing 4, the pressure in the casing gap 17 is maintained at the suction pressure, and the leakage water is absorbed by the suction casing 1. It is led to the suction channel inside. Eliminating the sealing material of the intermediate casing 4 can reduce the cost of assembling the single-body wheel-cut multi-stage pump and the material cost of the sealing material, thereby reducing costs.

The above-described conventional double barrel (barrel type)
In the case of the ring-section type multi-stage pump, the high-pressure pump discharge pressure acts on the barrel casing provided outside the intermediate casing. Although it was necessary to make the barrel casing considerably thick, in this embodiment, since only a low suction pressure is applied to the casing gap, the barrel casing may be a thin one for low pressure. For this reason, a cylindrical steel pipe can be used for the barrel casing, and the material cost is reduced.

The present embodiment is also different from the conventional single-body wheel-cut type multi-stage pump in which the balance chamber and the suction casing are connected by a balance pipe in order to make the pressure in the balance chamber a suction pressure. In the above, the casing gap, which is the suction pressure, and the balance chamber are communicated with each other through the balance-side communication passage, so that the casing gap can function as a conventional balance pipe, and the balance pipe can be eliminated, thereby reducing costs. Become.

FIG. 2 shows a specific communication structure of the suction-side communication passage 18 or the balance-side communication passage 19. Since the casing gap 17 has the function of the conventional balance pipe 11, each communication passage requires a cross-sectional area equivalent to that of the conventional balance pipe. In this embodiment, however, each of the suction casing 1 and the discharge casing 2 Several holes having the same cross-sectional area as the conventional balance pipe are formed in the circumferential direction of the casing gap 17 to communicate with the suction passage and the balance chamber, respectively.

FIG. 3 shows another embodiment of the present invention.

In this embodiment, when the outer casing 15 has only a function of returning a slight leak from the casing fitting portion to the suction flow path (when the balance pipe is not considered), the casing gap 17 is not necessarily required. Therefore, the intermediate casing 4 and the outer casing 15 are brought into close contact with each other.
A groove 20 is formed in the inner surface of the outer casing 15 at a portion corresponding to the fitting portion of the intermediate casing 4, and leakage water flowing into the groove 20 is collected by a groove 21 formed in the inner surface of the outer casing 15 in an axial direction, and is connected to the suction side connection. The structure returns to the suction passage through the passage 18.

With regard to noise, the impeller 1 and the diffuser blades 12
Although the fluid noise generated from the fluid propagates to the intermediate casing 4 and generates large noise, a part of the vibration energy is converted into the heat energy by the internal viscosity of the water in the casing gap 17 according to the present embodiment, and the vibration is attenuated. That is, FIG.
As shown in the figure, water has a greater sound attenuation than metal and has a greater vibration damping effect.

As shown in FIG. 5, sound transmission loss differs between the single wall and the double wall. The larger the transmission loss TL on the vertical axis of FIG. 5 is, the higher the sound insulation performance is,
In the case of the double wall, if attention is paid to the low-frequency resonance transmission of f ₀ in the region (II), the TL is larger in the regions (III) and (IV) than in the single wall, which is advantageous in sound insulation. . For this reason, the noise of the single body wheel section type multi-stage pump is reduced.

The above embodiment shown in FIG. 1 and FIG.
In each case, a single-stage single-wheel multi-stage pump in which the first-stage impeller has single suction is shown. However, a single-body single-wheel multi-stage pump in which the first-stage impeller has both suctions may be used.

Further, although the embodiment shown in FIGS. 1 and 2 shows a single-shaft multi-stage pump with a horizontal axis, it is also effective for a single-shaft multi-stage pump with a vertical axis.

[0028]

According to the present invention described above, the following effects can be obtained.

(1) By eliminating the seal between the intermediate casings, assembly costs and material costs can be reduced.

(2) The casing gap fulfills the function of a balance pipe, so that the balance pipe can be eliminated and the cost can be reduced.

(3) The noise of the pump can be reduced, so that there is no need to attach a soundproof cover, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a single-body wheel-cut multi-stage turbine pump according to the present invention.

FIG. 2 is a cross-sectional view of a fitting portion between a suction casing and a first-stage intermediate casing or a fitting portion between a discharge casing and a last-stage intermediate casing in the embodiment of FIG. 1;

FIG. 3 is a longitudinal sectional view of another embodiment of the single-body wheel-cut multi-stage turbine pump of the present invention.

FIG. 4 is an explanatory diagram showing attenuation of sound in a solid.

FIG. 5 is an explanatory diagram showing a transmission loss of sound of a double wall.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Suction casing, 2 ... Discharge casing, 3 ... Impeller, 4 ... Intermediate casing, 5 ... Tightening bolt, 6 ... Balance device, 7 ... Rotating shaft, 8a, 8b ... Bearing, 9a, 9b ... Shaft sealing device, DESCRIPTION OF SYMBOLS 10 ... Balance chamber, 12 ... Diffuser blade, 13 ... Water return blade, 15 ... Outer casing, 16 Outer casing sealing material, 17 ... Casing gap, 18 ... Suction side communication path, 19 ... Balance side communication path, 20 ... Groove, 21 ... axial groove.

Claims (9)

[Claims] A multi-stage impeller, a diffuser for restoring the static pressure of fluid, and a single-body, single-section, ring-cut intermediate casing.
An outer casing is provided outside the intermediate casing, and a radially sealed gap is formed between the intermediate casing and the outer casing. The casing gap is a suction passage of the suction casing. A single-body wheel-cut multi-stage pump characterized by communicating with 2. A multi-stage impeller, a diffuser for restoring the static pressure of fluid, a balance chamber on the discharge side of the pump equal to the suction pressure of the pump, and a single body having a ring-shape. In a single-body wheel-cut type multi-stage pump comprising a single-body wheel-cut type intermediate casing, an outer casing is provided outside the intermediate casing, and the outer casing is radially sealed between the intermediate casing and the outer casing. Forming a gap,
The casing gap is communicated with the balance chamber. 3. The single-body, wheel-cut, multi-stage pump according to claim 1, wherein the fitting portions of the suction casing, the intermediate casing, and the discharge casing are in direct metal contact with each other. Single body wheel-cut multi-stage pump. 4. A single-body wheel-cut multi-stage pump according to claim 1, wherein the outer casing is a steel pipe. 5. The single-body, wheel-cut, multi-stage pump according to claim 1, wherein the casing gap communicates with a suction passage of the suction casing and a communication passage formed in the suction casing. A multi-stage pump with a wheel ring. 6. A single-body wheel cutting type multi-stage pump according to claim 2, wherein the casing gap and the balance chamber communicate with each other by a communication passage formed in the discharge casing. Type multi-stage pump. 7. The single-body wheel-cut multi-stage pump according to claim 1, wherein the pump is a water supply pump. 8. A single-body wheel-cut multi-stage pump comprising an impeller assembled in multiple stages and a single-body and single-body wheel-cut intermediate casing having a wheel-cut shape. Characterized in that an outer casing is formed outside the outer casing, and a gap between the intermediate casing and the outer casing is made equal to a suction pressure of the pump. 9. A suction casing having a suction passage, a discharge casing for discharging a fluid, a multi-stage assembled centrifugal impeller, a diffuser for restoring a static pressure of the fluid, and a pump. A single-chassis wheel-cut multi-stage including a balance chamber equal to the suction pressure of the pump on the discharge side, a shaft sealing device, and a single-chassis, single-slice, ring-cut intermediate casing. In the pump, the intermediate casing is in direct metal contact, an outer casing is provided outside the intermediate casing, and a casing gap is formed between the intermediate casing and the outer casing. A single-body wheel-cut multi-stage pump characterized in that a suction passage of a suction casing and a balance chamber are communicated with each other.