JP7202190B2 - centrifugal pump - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Date of sale: March 26, 2018 Place of sale: Actio Engineering Division Publisher: Furukawa Sanki Systems Co., Ltd. (2) Date of sale: 2018 October 2nd Sale place: Actio Engineering Co., Ltd. Publisher: Furukawa Sanki Systems Co., Ltd. (3) Sale date: March 26, 2018 Sale place: Aktio Engineering Co., Ltd. Publisher: Furukawa Sanki Systems Co., Ltd.

The present invention relates to a centrifugal pump, and more particularly to a wetted part structure suitable for a centrifugal pump used for pumping slurry.

This type of centrifugal pump has a frame and a casing provided in front of the frame. A closed-type impeller is housed inside the casing (see Patent Document 1, for example).
FIG. 4 shows a specific configuration example of the main part. In the centrifugal pump 100B shown in the figure, the casing 102 is fixed to the casing body 120 in the center in the axial direction, the back cover 130 behind the casing body, the front cover 110 in front of the casing body, and the front cover 110 from the front side. and an annular cover flange 140 .

The casing main body 120 and the back cover 130 are fixed to each other with bolts and nuts. The casing main body 120 and the cover flange 140 are fixed to each other with bolts and nuts, and a housing space for the impeller 50 is defined inside the casing 102 .
The casing main body 120 has a discharge port 120a formed in its upper portion, and the front cover 110 has a suction port 110a projecting forward along the axial direction at its center. The suction port 110 a communicates with the discharge port 120 a through the suction portion 50 a of the impeller 50 .
Here, centrifugal pumps of this type may pump an abrasive suspension of undissolved particulate material, commonly referred to as slurry, as the pumping fluid. Therefore, in this type of centrifugal pump, high-chromium cast iron is heat-treated and used as the casing material depending on the properties of the fluid to be pumped.

Japanese translation of PCT publication No. 2007-511698 (paragraph 0002)

However, it is difficult to machine an O-ring groove with a predetermined accuracy in hardened high chromium cast iron after heat treatment. Therefore, conventionally, this type of centrifugal pump does not use an O-ring, but uses an annular seat packing 160 as shown in FIG. It is interposed between the casing main body 120 and the cover flange 140 to ensure pressure resistance.
However, this seat packing 160 is made of a non-rubber material having a relatively high hardness. The seat packing 160 also serves as a shim for adjusting the clearance of the portion where the impeller 50 and the inner surface of the front cover 110 face each other. Therefore, since a non-rubber material having a relatively high hardness is used, it is difficult to withstand a high withstand voltage.

Therefore, the present invention has been made by paying attention to such problems, and provides a centrifugal pump that facilitates machining of the O-ring groove in the wetted portion with a predetermined precision and that can improve pressure resistance performance. The challenge is to

In order to solve the above problems, a centrifugal pump according to an aspect of the present invention includes a frame that rotatably supports a drive shaft, a casing that is provided in front of the frame, a casing that is housed inside the casing, and the and an impeller connected to the tip of the drive shaft, wherein the casing includes a casing body in the center in the axial direction, a back cover behind the casing body, a front cover in front of the casing body, and fixed to the front cover from the front side. The cover flange is formed of a non-heat-treated steel material that can be machined, and has a cylindrical surface facing the inner peripheral surface of the casing body and an outer surface of the front cover. and a side surface and an opposing inner surface, wherein an annular O-ring groove is provided on each of the cylindrical surface and the inner surface.

According to the centrifugal pump according to one aspect of the present invention, the cover flange is formed of a non-heat-treated steel material that can be machined, and has a cylindrical surface facing the inner peripheral surface of the casing main body and an outer surface of the front cover. Since the annular O-ring grooves are provided on the opposing inner side surfaces, respectively, the O-ring grooves can be machined on the cylindrical surface and the flat surface with a predetermined accuracy. Therefore, pressure resistance performance can be improved.

Here, in the centrifugal pump according to one aspect of the present invention, a pair of steel adjustment plates divided into two in a semicircular shape are provided in a clearance adjustment portion where the impeller and the inner surface of the front cover face each other. Interposing between the front cover is preferable.
With such a configuration, the annular seat packing is replaced with a pair of adjustment plates that are divided into two semicircles. By inserting and removing the adjustment plate, the clearance of the portion where the impeller and the inner surface of the front cover face each other can be easily adjusted.

In addition, in the centrifugal pump according to the aspect of the present invention, the back cover and the casing body are fitted together by spigot fitting, and an annular O-shape is formed at the inner peripheral corner of the spigot fitting portion of the casing body. It is preferable that the ring groove is machined.
With such a configuration, since the O-ring groove is processed in the corner of the inner periphery of the spigot fitting portion of the casing main body, high chromium cast iron is used after heat treatment as the material of the casing. Even if there is, the circular O-ring groove with a predetermined precision can be machined using a strong cutting tool because the machining portion is the corner.

As described above, according to the present invention, it is possible to easily process the O-ring groove with a predetermined accuracy and improve the pressure resistance performance of the centrifugal pump.

1 is an explanatory view of one embodiment of a centrifugal pump according to one aspect of the present invention, in which a portion of a casing is shown in cross section along the axis; FIG. FIG. 2 is an enlarged view of a main portion of FIG. 1; FIG. 4 is a plan view showing a pair of steel plates for adjusting the impeller clearance of the centrifugal pump according to one aspect of the present invention; FIG. 2 is an explanatory diagram of an example of a conventional centrifugal pump, in which the casing portion is shown in cross section along the axis. FIG. 11 is a plan view showing a sheet packing for adjusting impeller clearance of a conventional centrifugal pump;

An embodiment of the present invention will be described below with appropriate reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship, ratio, etc. between the thickness and the planar dimensions are different from the actual ones, and the drawings include portions where the relationship and ratio of the dimensions are different from each other.
Further, the embodiments shown below are examples of devices and methods for embodying the technical idea of the present invention. etc. are not specified in the following embodiments.

As shown in FIG. 1 , the centrifugal pump 100 of this embodiment has a casing 2 provided in front of the frame 1 . A bearing portion (not shown) is provided at the rear portion of the frame 1, and the drive shaft 3 is rotatably supported via the bearings separated in the front and rear directions in the axial direction.
The casing 2 has an annular shape fixed from the front side by bolts and nuts to the casing body 20 at the center in the axial direction, the back cover 30 at the rear of the casing body 20, the front cover 10 at the front of the casing body 20, and the front cover 10. and a cover flange 40 of . The rear portion of the back cover 30 is fixed to the front surface of the frame 1 with bolts and nuts.

In this embodiment, as the material of the front cover 10, the casing main body 20 and the back cover 30, high-chromium cast iron is used after being subjected to heat treatment. On the other hand, the annular cover flange 40 is formed from a non-heat-treated steel material that can be machined. In this embodiment, the material of the cover flange 40 is, for example, general structural rolled steel (SS400), spheroidal graphite cast iron (FCD), or the like.

The casing main body 20 and the back cover 30 are fixed to each other by bolts and nuts 71 , and the casing main body 20 and the cover flange 40 are fixed to each other by bolts and nuts 72 . The front cover 10 is fixed to the cover flange 40 with fixing bolts 73 .
As a result, the front cover 10 is fixed to the casing main body 20 via the cover flange 40 , and an accommodation space for the impeller 50 is defined inside the casing 2 . A cylindrical shaft sealing device 4 containing a gland packing, a mechanical seal, and the like is provided at the center of the back surface of the back cover 30 to seal the tip side of the drive shaft 3 .

A closed-type impeller 50 housed inside the casing 2 is fixed to the tip of the drive shaft 3 so as to be rotatable integrally with the drive shaft 3 . In this embodiment, a male thread is formed at the tip of the drive shaft 3, and the male thread is screwed into a female thread formed at the center of the end face of the impeller 50 on the proximal side, so that the drive shaft 3 and the impeller 50 are coaxial. Concatenated.
The impeller 50 includes a substantially disk-shaped main plate 51, a plurality of blades 52 provided on the surface of the main plate 51 facing the suction port side and protruding axially forward, and integrally formed on the front surface of the plurality of blades 52. and an annular shroud 53 . The shroud 53 rotates facing the inner wall surface of the stationary (fixed) front cover 10 .

A discharge port 20a is formed in the upper portion of the casing body 20, and a suction port 10a is formed in the center of the front cover 10 so as to protrude forward along the axial direction. The suction port 10 a communicates with the discharge port 20 a via the suction portion 50 a of the impeller 50 . In the present embodiment, an O-ring groove 23 is machined in the casing main body 20 at the corner of the rear end of the inner periphery of the spigot fitting portion 21 with the back cover 30 . An O-ring 83 is fitted in the O-ring groove 23 .

2, the annular cover flange 40 has a plurality of first attachments for fixing to the casing main body 20 with the bolts and nuts 72 on the radially outer side, as shown in FIG. A hole 40a is formed therethrough in the axial direction. An annular concave stepped portion 40t is formed on the back side of the first mounting hole 40a, and the surface of the concave stepped portion 40t facing radially outward faces the inner peripheral surface 20n of the casing body 20 in the radial direction. It is a cylindrical surface 40s.
An annular O-ring groove 41 is formed in the cylindrical surface 40s of the cover flange 40 at a substantially central position in the axial direction by cutting. An O-ring 81 is fitted in the O-ring groove 41 .

Further, a plurality of second mounting holes 40b for fixing to the front cover 10 with the fixing bolts 73 are axially penetratingly formed radially inside the cover flange 40 . The second mounting hole 40b is formed as a counterbore so that the head of the fixing bolt 73 is embedded.
An annular concave stepped portion 40p is formed on the back side of the second mounting hole 40b. It is designed to fit with the part and spigot.

Further, between the radially outer recessed stepped portion 40t and the radially inner recessed stepped portion 40p, there is provided a radially inner recessed stepped portion 40p so as to protrude axially rearward from the outer side surface 10s of the front cover 10 in the axial direction. Opposed inner side surfaces 40n are formed.
An annular O-ring groove 42 is formed by cutting on the inner side surface 40n of the cover flange 40 at a substantially central position in the radial direction. An O-ring 82 is fitted in the O-ring groove 42 .
The cover flange 40 of the present embodiment is mounted on the mounting surface 20m of the casing main body 20 on the distal end side through a pair of steel adjustment plates 60 divided into two semicircles as shown in FIG. 72.

In this centrifugal pump 100, the impeller clearance ΔT, which is the facing gap between the inner surface of the casing 2 (in this example, the inner surface of the front cover 10) and the front edge of the impeller 50 shown in FIG. It is adjusted by increasing or decreasing the number of insertions.
Here, as shown in FIG. 3, the pair of adjustment plates 60 are formed symmetrically with respect to both the vertical axis VL and the horizontal axis HL. Each of the portions 61, 62, 63 has a groove shape that opens toward the inner peripheral side along the direction of the horizontal axis HL.
As a result, when adjusting the impeller clearance ΔT by increasing or decreasing the number of the pair of adjusting plates 60 inserted, the pair of adjusting plates 60 can be inserted and removed only by loosening the fastening state of the bolts and nuts 72 (without completely removing them). It's becoming

Next, the effects of the centrifugal pump 100 of this embodiment will be described.
According to the centrifugal pump 100 of the present embodiment, the annular cover flange 40 is formed of a non-heat-treated steel material that can be cut, and has a cylindrical surface 40s facing the inner peripheral surface of the casing body 20 and a front cover. 10 are provided with annular O-ring grooves 41 and 42 on the inner side surface 40n opposed to the outer side surface of 10, respectively, so that the O-ring grooves 41 and 42 are formed on the cylindrical surface 40s and the inner side surface 40n with a predetermined accuracy. can be processed into Therefore, it is possible to easily process the O-ring grooves 41 and 42 with a predetermined precision, and to improve the pressure resistance performance. In the configuration of the present embodiment, it is possible to secure a withstand voltage performance that is at least twice that of the conventional one.

Further, according to the centrifugal pump 100 of the present embodiment, since the O-ring groove 23 is processed in the corner of the inner periphery of the spigot fitting portion 21 of the casing body 20, the processed portion is the corner. Therefore, an annular O-ring groove 23 having a predetermined precision can be machined using a strong cutting tool.
Conventionally, as shown in FIG. 5, a mounting structure in which one annular seat packing 160 is interposed and a large number of closed mounting holes 161 formed along the center line CL of the packing width W has been employed. Therefore, in order to replace the seat packing 160, the cover flange 40 and the front cover 10 must be disassembled.

On the other hand, according to the centrifugal pump 100 of this embodiment, instead of the annular seat packing 160 as shown in FIG. Mounting portions 61, 62, and 63 through which the bolts of nut 72 are inserted are all groove-shaped and open toward the inner peripheral side along the direction of horizontal axis HL. The impeller clearance ΔT can be easily adjusted by inserting and removing the pair of adjustment plates 60 from the left and right outer sides in the radial direction without disassembling the .

It should be noted that the centrifugal pump according to the present invention is not limited to the above-described embodiment, and of course various modifications are possible without departing from the gist of the present invention.

REFERENCE SIGNS LIST 1 frame 2 casing 3 drive shaft 4 shaft sealing device 10 front cover 20 casing body 21 fitting portion 23 O-ring groove 30 back cover 40 cover flange 40n inner surface 40s cylindrical surface 41 O-ring groove 42 O-ring groove 50 impeller 51 main plate 52 vane 53 shroud 54 mounting portion 60 adjustment plate 61 first recess 62 second recess 63 third recess 71 bolt/nut 72 bolt/nut 81, 82, 83 O-ring 100 centrifugal pump ΔT impeller clearance

Claims (3)

A frame that rotatably supports a drive shaft, a casing provided in front of the frame, and an impeller housed inside the casing and connected to the tip of the drive shaft,
The casing has a casing body in the center in the axial direction, a back cover behind the casing body, a front cover in front of the casing body, and an annular cover flange fixed to the front cover from the front side,
The cover flange is formed of a non-heat-treated steel material that can be machined, and has a cylindrical surface facing the inner peripheral surface of the casing body and an inner surface facing the outer surface of the front cover, A centrifugal pump, wherein an annular O-ring groove is provided on each of the cylindrical surface and the inner surface. A pair of semicircularly divided steel plates are interposed between the cover flange and the front cover for adjusting the clearance between the impeller and the inner surface of the front cover. 2. The centrifugal pump of claim 1. The back cover and the casing body are fitted together by spigot fitting,
3. A centrifugal pump according to claim 1, wherein an annular O-ring groove is machined in a corner portion of the inner periphery of the spigot fitting portion of the casing body.

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