JP2849838B2 - Screw centrifugal pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw centrifugal pump for pumping a fluid such as sewage, slurry, or a chemical solution, and more particularly to a leak-free screw centrifugal pump.

[Prior art] The screw centrifugal pump has less clogging even when pumping liquid containing solid matter, and has a higher suction capacity than a general centrifugal pump and a shaft power characteristic that does not have a fear of exceeding horsepower. Since it has characteristics such as load characteristics, it is used for pumping liquids and slurry substances including solids.

In addition, the present applicant has already proposed a leak-free screw centrifugal pump that has no shaft seal part and all liquid contact parts are made of ceramics in order to pump highly corrosive or toxic liquids. See JP-A-63-295891).

As shown in FIG. 2, the structure of this pump includes an impeller 21 having a tapered screw centrifugal blade 21a on its inner surface,
It was housed in a pump chamber formed by the fixed body 22, the front cover 23, and the casing 24. A driven magnet 30 is arranged on the outer peripheral portion of the impeller 21, and the impeller 21 is rotated by driving an external drive magnet 31 with a pulley 29, and the fluid is pressure-fed from the suction port 25 to the discharge port 26. I was

[Problems of the prior art] The screw centrifugal pump shown in FIG.
Although the rotation of the impeller 21 is supported by the two bearings 27 and 28, there is a problem that the bearing portion is located on the outer peripheral portion of the impeller 21 so that the sliding speed is high and the bearing is easily worn.

Also, when the impeller 21 rotates, the screw centrifugal blade
There is also a problem that the tip of 21a comes into contact with the fixed body 22 and is chipped or is severely worn.

[Means for Solving the Problems] In view of the above, the present invention provides an impeller having a substantially cylindrical ceramic inner surface formed with a tapered male screw-shaped screw centrifugal vane in a pump chamber, and the above impeller is acted upon by an external magnetic force. In a screw centrifugal pump configured to rotate the impeller, the impeller is rotatably supported by a suction sleeve extending from a suction port,
The impeller is provided with a back blade on a surface on the suction port side.

[Operation] According to the present invention, since the impeller is provided with the back blade, the impeller is pressed against the suction port side during rotation, so that the tip of the screw centrifugal blade does not come into contact with the fixed body and chipping can be prevented. . Further, since the rotary bearing portion of the impeller is located at the center, the sliding speed is low and the wear is small.

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

FIG. 1 shows a cross section of a screw centrifugal pump according to an embodiment of the present invention. Reference numeral 1 denotes an impeller made of a ceramic body and having a tapered female screw-shaped screw centrifugal blade 1a formed on an inner surface thereof. A conical fixed body 3 substantially matching the tapered inner surface of the impeller 1 is mounted on the casing 2, the casing 2, the partition 8, and the front piece 9.
A pump chamber surrounding the impeller 1 is formed by this, and the pump chamber is completely sealed except for the suction port 11 and the discharge port 12.

The impeller 1 is rotatably supported in the pump chamber by a suction sleeve 4 extending from a suction port 11, and a driven magnet 5 is further attached to the impeller 1.
A pulley 7 provided with a driving magnet 6 is rotatably disposed outside the partition wall 8 and held by 1b.
A plurality of back blades 10 are provided on the surface of the impeller 1 on the suction port 11 side.
Are provided at symmetrical positions, and as a whole, are arranged vertically so that the rotation axis of the impeller 1 is in the vertical direction.

Among these components, the impeller 1, which is a liquid contact part,
The sleeve 1b, the casing 2, the fixed body 3, the suction sleeve 4, the partition 8, the front piece 9, and the back blade 10 are all made of ceramics.

 Next, the operation of this pump will be described.

First, if the pulley 7 is rotated by a motor (not shown), a rotational force can be generated in the impeller 1 by the magnetic action of the drive magnet 6 and the driven magnet 5, and the suction port 11 can be generated by the action of the screw centrifugal blade 1a. The fluid can be pumped to the discharge port 12 more. Further, at this time, since there is no shaft seal portion, the pump becomes a leak-free pump in which the pressure-feeding fluid does not leak at all, and since the liquid contact portion is entirely made of ceramics, it has excellent corrosion resistance and heat resistance.

Further, while the impeller 1 is rotating, the pumping fluid flows back through the gap between the impeller 1 and the partition 8 to return in the pump chamber to perform a lubricating action and a cooling action. The space S between the front pieces 9 has a lower pressure than the discharge port 12 side. Therefore, the impeller 1 is pressed against the front piece 9 side, and the screw centrifugal blade
There is a gap of about 0.5 to 1 mm between the tip of 1a and the fixed body 3, and they do not contact each other. Further, since the impeller 1 is pressed against the front piece 9, the impeller 1 is axially supported only by the radial bearing portion 4a of the suction sleeve 4 and the thrust bearing portion 9a of the front piece 9. Is located at the center of the impeller 1, the sliding speed (peripheral speed) is low, and the amount of wear can be reduced.

Further, since the rotation axis of the impeller 1 is in the vertical direction, the load on the bearing portion can be reduced by the gyro-moment effect in which the impeller 1 rotates independently around the lower end of the impeller 1.
A groove 9b is formed in the thrust bearing 9a of the front piece 9, and the suction sleeve 4 is connected to the groove 9b.
Since the through hole 4b is formed in the pump chamber, after the rotation is stopped, all the fluid in the pump chamber returns to the suction port 11 side through the through hole 4b, and no slurry or the like remains in the pump chamber.

In the above embodiment, only the vertical type is shown. However, the present invention is not limited to this, and a horizontal type in which the rotation axis of the impeller 1 is the same as that of the horizontal type and has the same structure can also provide excellent effects. Needless to say.

In the above embodiment, the impeller 1 is attached to the front piece 9.
Although the thrust bearing 9a is formed, the distal end surface of the suction sleeve 4 can be a thrust bearing.

Next, the ceramic material used for the screw centrifugal pump of the present invention will be described. Since the pump of the present invention is for pumping a highly corrosive fluid under pressure, it is the most important required characteristic that the ceramic material be excellent in corrosion resistance.

Therefore, when using alumina ceramics,
High-purity alumina ceramics having a ₂ O ₃ content of 99.5% or more and a balance of SiO ₂ , MgO or the like is used. If higher corrosion resistance is required, use is made of silicon carbide-based ceramics containing SiC of 80 to 95% by weight as a main component and containing B and C as sintering aids and subjected to solid-phase sintering. Since the silicon carbide ceramics are solid phase sintered, they are particularly excellent in corrosion resistance.

Further, since the partition wall 8 is desirably formed to be thin in order to increase the magnetic force, a high-strength ceramic can be used. High-strength ceramics include, for example, ZrO ₂
Is a partially stabilized zirconia ceramic containing 1 to 7 mol% of Y ₂ O ₃ as a stabilizer, or a sintering aid containing 80 to 95 wt% of Si ₃ N ₄ as a main component. Y ₂ O ₃ , Al ₂
Silicon nitride ceramics containing O ₃ and having needle-like crystals are used.

Further, when the impeller 1 is formed of ceramics, a middle mold having a tapered male screw shape and a smooth surface having the same shape as that of the screw centrifugal blade 1a is prepared, and a rubber press method, a casting method, and the like are used by using the middle mold. After molding by
It can be easily formed by extracting the middle mold while twisting and firing.

Next, the performance of the screw centrifugal pump shown in FIG. 1 will be described. The impeller 1, the sleeve 1b, the casing 2, the fixed body 3, the suction box 4, the partition 8, the front piece 9, and the back blade 10 are all made of alumina ceramic having an Al ₂ O ₃ content of 99.5%. A screw centrifugal pump was configured with a suction port 11 having a diameter of 50 mm and an impeller 1 having a diameter of 160 mm. Impeller 1 35
The characteristics when the fresh water was pressure-fed while rotating at 00 revolutions / minute and the discharge amount was changed on the discharge port 12 side were examined. The result is third
As shown in the figure.

In FIG. 3, the total head is a discharge pressure, and the discharge pressure increases as the discharge amount is reduced and reduced. The shaft power is electric power for rotating the motor, and the shaft power increases as the discharge amount increases. Further, the efficiency was obtained by dividing the work provided by the product of the discharge pressure and the discharge amount by the shaft power, and the maximum efficiency was obtained when the discharge amount was 0.3 m ³ / min.

These characteristics are comparable to those of a general screw centrifugal pump, and it is understood that the screw centrifugal pump of the present invention has sufficiently usable characteristics. Further, the above characteristics are one example, and the characteristics can be freely changed by changing the shape, angle, and the like of the screw centrifugal blade 1a.

[Effects of the Invention] As described above, according to the present invention, an impeller in which a tapered male screw-shaped centrifugal blade is formed on the inner surface of a substantially cylindrical ceramic body is housed in a pump chamber, and the impeller is acted upon by an external magnetic force. In the screw centrifugal pump, the impeller is rotatably supported by a suction sleeve extending from a suction port, and the impeller is provided with a back blade on a surface of the impeller on the suction port side. It is possible to prevent the blade tip from contacting the fixed body to cause chipping, and since the bearing portion is located at the center, the sliding speed can be reduced to reduce wear. Furthermore, if the rotation axis of the impeller is set to the vertical direction, it is possible to provide a high-performance screw centrifugal pump having various effects such as complete discharge of the fluid in the pump chamber when the rotation of the impeller is stopped.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a screw centrifugal pump according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing a conventional leak-free screw centrifugal pump. FIG. 3 is a graph showing the performance of the screw centrifugal pump of the present invention. 1: impeller, 2: casing 3: fixed body, 4: suction sleeve 5: driven magnet, 6: drive magnet 7: pulley, 8: partition wall 9: front piece, 10: back blade 11: suction port, 12: discharge port

Claims (1)

(57) [Claims] An impeller having a tapered female screw-shaped centrifugal blade formed on a substantially cylindrical ceramic body surface and having a magnetic body is housed in a pump chamber, and the impeller is rotated by an external magnetic force. The centrifugal pump according to claim 1, wherein the impeller is rotatably supported by a suction sleeve extending from a suction port, and a back blade is provided on a surface of the impeller on the suction port side.