RU2494848C2 - Method of producing rotary pump impeller - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to power engineering and can be used for production of rotary pump impellers with OD not over 400 mm and complex shape of intervane channels. Impeller base disk is made integral with the half of total quantity of vanes arranged next but one. Cover disk is made integral with the other half said quantity of vanes. Note here that said disks have slots on surfaces engaged with vanes while the latter have ledges. Said disks are assembled so that intervane channels are formed. In assembly, vane ledges are fit in disk slots to allows transfer of torque there between. Base and cover disks are welded together. Weld joint is performed at disk slots, for example, on their outer surface. Said slots may be symmetric about impeller rotational axis.

EFFECT: higher quality of impellers, simplified production.

3 cl, 5 dwg

Description

The present invention relates to pumps of continuous displacement with rotational movement of the working bodies, and more particularly to structural units of centrifugal vane pumps. The invention can be used as a method of manufacturing an impeller of a centrifugal pump, mainly having an outer diameter of not more than 400 mm and a complex spatial shape of the inter-blade channels, in particular, used in nuclear power plants at nuclear power plants (NPPs).

The creation of a fluid flow and an increase in its energy in a centrifugal impeller pump is carried out using an impeller rotated by an engine. In a closed impeller with a one-way entrance, a hub is distinguished, a main (leading, rear) disk covering (driven, front) or cover, a disk with an inlet, and also blades connecting these disks and forming inter-blade channels in the space between the disks [1: P.13]. The impeller of centrifugal blade machines for supplying and compressing gases (compressor, fan and others), in the General case, has the same elements [2: S.126, 128].

The main parameters of the pump, the main of which are supply, pressure (pressure), power and efficiency, provide, in particular, the appropriate choice of the shape of the inter-blade channels of the impeller and the proper quality of execution of the latter (for example, their surface cleanliness). Wheel reliability determines, among other factors, the strength of the impeller.

It is known that the impeller of the TsVN-8 pump (1280 mm in diameter) for nuclear power plants with an RBMK type reactor is welded from two parts: a disk with blades of double curvature and a cover disk [3: P.182; 4: S.35]. According to the technological scheme of manufacturing the impellers, the profile of the disk with blades is processed on a copy-milling machine with programmed control, the cover disk and the disk with blades are welded together by argon-arc welding, the wheels are heat treated to relieve stresses after welding [5: P.205].

The disadvantages of this method are the difficulty of providing high wheel strength using those welded joints that are possible with the specified separation of the wheel into parts, for example, T-joints or in the form of grooves (electrical rivets), as well as the need for heat treatment of the entire wheel after welding. In this case, welds, generally speaking, distort the shape of the inter-blade channels.

A known method of manufacturing an impeller of a centrifugal pump (patent RU No. 2274509, B21K 1/36, publ. 2006), according to which the impeller is made of two parts, forming each blade by means of a butt welded joint of two elements, one of which is made in the form of a protrusion on the main disk in one piece with the last, and the other on the spanning disk in one piece with the last.

The disadvantages of this method are the technological difficulty, and in some cases the impossibility of obtaining a complex spatial shape of the inter-blade channels for small wheels.

The problem solved by the invention is to increase the reliability of the impeller, eliminating the need for heat treatment after welding, improving the quality of the flow part and simplifying the manufacturing technology of the complex spatial shape of the inter-blade channels for small impellers (outer diameter 400 mm or less).

When implementing the invention, the following technical results can be obtained:

- elimination of restrictions on the dimensions of the impellers made by welding;

- An increase in the inter-blade space on each disk;

- improving access to the tool in the manufacture;

- reduction of residual stresses and prediction of their type and magnitude;

- the exception of the angular displacement of one part of the impeller relative to another;

- centering of the parts of the impeller during assembly;

- uniform radial distribution of the mass of the wheel;

- reducing the load of the welded joints of the wheels of the impeller;

- Improving the convenience of the welder and weld control;

- improving the class of surface roughness;

- elimination of the influence of the external weld on the geometry of the inter-blade channel and the prevention of distortion of the shape of the inter-blade channels (compared to a predetermined one).

As a solution to the problem, which allows to achieve an effect with the indicated characteristics, a method for manufacturing a centrifugal pump impeller is proposed, in which the impeller is made of two parts, forming half of the total number of blades selected through one, in one piece with the main disk, and the other half of the blades for integral with the covering disk, while on the mating surfaces of the blades and disks, grooves are made on the side of the disks, and on the side of the blades there are protrusions that enter these grooves when assembling the wheel, the transmission of torque between both parts of the impeller, and then perform the welding of the protrusions of the blades to the disks in these grooves.

Preferably, the welded joint of the main and covering disks in the grooves is performed sequentially and in diametrically opposite sides.

It is advisable to weld the main and covering disks in the grooves from the outside of the disks (reverse inter-blade channels).

Preferably, the grooves are performed symmetrically about the axis of rotation of the impeller for uniform distribution of metal along the radial length of the wheel.

The above separation of the blades along the disks of the impeller provides an increase in the inter-blade space on each disk and, as a result, improves access to the tool during manufacturing, increasing the manufacturability and manufacturing quality of the disks as compared with the case when all the working blades, in whole or in part, are made in one piece with a disk.

The symmetrical arrangement of the grooves in which welding is performed provides a reduction in residual stresses and prediction of their type and magnitude, which eliminates the need for heat treatment of the entire wheel after welding.

Ensuring the exclusion of the angular displacement of one part of the impeller relative to the other, centering of the parts of the impeller during assembly and uniform radial distribution of the mass of the impeller, is achieved by the fact that protrusions are made on the end surfaces of the blades so that the protrusions fit snugly into the grooves when assembling the main and covering disks .

Thanks to the protrusions included in the grooves of the disks, they increase the reliability of the impeller, since generally speaking, these protrusions will absorb a significant proportion of the load during operation of the pump, thus unloading the welded connection of the disks of the impeller.

Due to the implementation of welding from the outside of the disks, they provide greater convenience for the welder and control of the welds, improve the surface roughness class and, thus, increase their quality and reliability, in addition, the external weld does not affect the geometry of the inter-blade channel, preventing its distortion.

The claimed invention (in the particular case of implementation) is illustrated by the following drawings:

figure 1 is a section of the impeller along aa;

figure 2 is a General view of the impeller (from the side of the covering disk);

figure 3 - the main disk with blades;

4 is a covering disk with blades;

figure 5 is a section of the impeller along BB (figure 1) (and the symbol of the weld).

A method of manufacturing the impeller (figure 1, 2), including the formation of the inter-blade channels by connecting two parts on which the elements of the inter-blade channels are made — the main disk 1 with blades 3 and the covering disk 2 with blades 4 are as follows.

Forgings of the main and covering discs use forgings. Each workpiece is processed on a numerically controlled machine, milling blades 3, which are half of the total number of impeller blades selected through one, in one piece with the main disk 1 (figure 3), and blades 4, making up the other half of the total number of blades the impeller, - in one piece with the covering disk 2 (figure 4), which provides an increase in the inter-blade space on each disk and, due to this, provides better access to the tool in the manufacture, improving manufacturability and quality of production disc burner.

At the same time, grooves 5 are performed on the main and covering disks 1, 2 (FIGS. 4, 5), symmetrically positioning them relative to the axis of rotation of the wheel, which reduces residual stresses and predicts their appearance and magnitude, eliminating the need for heat treatment of the entire wheel after welding.

On the end surfaces of the blades 3, 4, protrusions 6 are performed (Figs. 4, 5) so that when assembling the main and covering disks 1, 2, the protrusions 6 fit snugly into the grooves 5 with the possibility of transmitting torque between both parts of the impeller, providing an exception angular displacement of one part of the impeller relative to the other, centering of the parts of the impeller during assembly and uniform radial distribution of the mass of the wheel. In addition, the protrusions perceive a significant proportion of the load during the operation of the pump, thus unloading, thus, the welded connection of the impeller disks.

Then, from the outside of the main and covering disks in the grooves 5, the main disk 1 and the covering disk 2 are sequentially welded in diametrically opposite sides, forming a seam 7 (Fig. 5), for example, by means of argon-arc welding, which provides greater convenience for the welder and monitoring welds, improving the class of surface roughness and, increasing their quality and reliability. With this welding technology, they prevent the substantial formation of weld defects, get full penetration throughout the entire thickness of the protrusions 6 included in the grooves 5 and predictability of residual deformations in appearance (mainly shrinkage in the direction of the axis of rotation of the wheel) and size, and also exclude the heat treatment after welding.

In addition, taking into account the external location of the weld 7 (Fig. 5), its influence on the geometry of the inter-blade channel is leveled, preventing distortion of its shape. Then, the quality of the welds and the welded surface is monitored by external inspection and by capillary method (reliably identifying all defects), and when detected, eliminate them.

After that, further machining of the surfaces of the impeller is carried out, while removing possible uneven deposition of metal in the area of grooves 5. Then, quality control of the welds and the heat-affected surface is repeated.

INFORMATION SOURCES

1. Cherkassky V.M. Pumps, fans, compressors: Textbook for high schools. - M .: Energoatomizdat, 1984.

2. Mikhailov A.K., Voroshilov V.P. Compressor machines: Textbook for high schools. - M .: Energoatomizdat, 1989.

3. Mitenkov F.M., Novinsky E.G., Budov V.M. The main circulation pumps of nuclear power plants. 2nd ed., Revised. and additional USSR. - M .: Energoatomizdat, 1990.

4. Pumps of nuclear power plants: Reference manual / P.N. Pak, A.Ya. Belousov, A.I. Timshin et al .; Under the total. ed. P.N. Pak. - M .: Energoatomizdat, 1989.

5. Budov V. M., Farafonov V. A. Design of the main equipment of nuclear power plants: Textbook. manual for universities. - M .: Energoatomizdat, 1985.

6. A method of manufacturing an impeller of a centrifugal pump (patent RU No. 2274509, B21K 1/36, publ. 2006).

Claims (3)

1. A method of manufacturing an impeller of a centrifugal pump, mainly having an outer diameter of not more than 400 mm and a complex spatial shape of the interlobed channels, comprising making the main and covering disks in one piece with the elements of the interlobed channels, assembling the main and covering disks with the formation of the interlobed channels and making welded connection of said disks, characterized in that the main disk is integral with one and a half of the total number of impeller blades located across cut one, and the covering disk - in one piece with the second half of the mentioned number of blades, the main and covering disks are made with grooves on the surfaces mating with the blades, and the blades - with protrusions that are included in the assembly of the main and covering disks into these grooves with the possibility of transmission between the torque disks, and the welded connection of the disks is performed in the grooves of the disks. 2. The method according to claim 1, characterized in that the welded joint of the main and covering disks is performed in grooves on the outside of the disks. 3. The method according to claim 1, characterized in that the grooves are performed symmetrically with respect to the axis of rotation of the impeller.

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