Ultra-high molecular weight polyethylene coated centrifugal pump impeller

Abstract

FIELD: oil producing industry; pump engineering.SUBSTANCE: invention relates to designs and methods for manufacturing impellers of submersible multistage centrifugal pumps intended for operation in difficult conditions and aggressive environments. The impeller of a centrifugal pump with a coating of ultra-high molecular weight polyethylene (UHMWPE), characterized in that it comprises a cover disk, a main disk with working blades, and also a metal disk placed and rigidly secured between them, with a coating made on them of ultra-high molecular weight polyethylene modified by using coarse fractions of silicon carbide (SiC) as a filler, wherein the coating is applied in an electrostatic field at a temperature of at least 220 °C, at which a continuous film with a thickness of 70 mcm is formed on the surface of the metal, with a content of 7% silicon carbide. The result of the invention is an increase in the average period of operational durability of the impeller of a centrifugal pump when in contact with an aggressive environment with the proposed model for producing layers by 30-40% compared to the average period of durability of known impellers of centrifugal pumps.EFFECT: increased strength characteristics of the impeller of a centrifugal pump by applying a coating that provides increased wear resistance and corrosion resistance.2 cl, 2 tbl

Description

[0001] The invention relates to the oil-producing industry and pump engineering, namely to designs and methods for manufacturing impellers of submersible multistage centrifugal pumps intended for operation in difficult conditions and aggressive environments.

[0002] An impeller of a borehole multistage centrifugal pump for oil production is known, which includes a hub, a driving and a driven disk, and blades located between them, wherein the driving and / or driven disk is made with an annular groove in which a support washer of the impeller is placed, made of a material whose surface hardness is less than the surface hardness of the material of the impeller, characterized in that a coating of an antifriction polymer material is applied to the surface of the impeller, as well as to the outer surface of the support washer, providing protection of the surface of the impeller and the support washer from corrosion and salt deposits, wherein the coating is applied in such a way as to provide protection of all surfaces of the support washer from access by formation fluid (RU Patent No. 2355917).The disadvantage of this centrifugal pump impeller is its low operational reliability and short service life, due to its low strength characteristics, namely, low corrosion resistance when in contact with an aggressive environment.

[0003] An impeller is known that comprises a main disk with rotor blades, a cover disk, and a metal disk positioned between the main and cover disks and rigidly connected to them. The main and cover disks are made of a composite polymer material, which in a particular embodiment includes organofluorine substances in the form of isobutane derivatives with fluorine-containing organic substituents. The invention is aimed at increasing the service life of the impeller while maintaining high pump efficiency in forced mode by ensuring dimensional stability, impeller rigidity, combined with minimal imbalance and high hydrodynamic characteristics (RU Patent No. 2352823). A disadvantage of this centrifugal pump impeller is low operational reliability and a short service life due to its low strength characteristics, namely, low corrosion resistance when exposed to aggressive media.

[0004] The objective of the invention is to improve the impeller of a centrifugal pump, ensuring its reliable operation and long service life when in contact with an aggressive environment.

[0005] The technical result of the invention is to increase the strength characteristics of the impeller of a centrifugal pump by applying a coating that provides increased wear resistance and corrosion resistance.

[0006] The technical result is achieved in that the impeller of a centrifugal pump with a coating of ultra-high molecular weight polyethylene (UHMWPE), characterized in that it contains a cover disk, a main disk with working blades, and also a metal disk placed and rigidly fixed between them, with a coating made on them of ultra-high molecular weight polyethylene modified by using coarse fractions of silicon carbide (SiC) as a filler, wherein the coating is applied in an electrostatic field at a temperature of at least 220°C, at which a continuous film with a thickness of 70 μm is formed on the surface of the metal, with a content of 7% silicon carbide.

[0007] In particular, the impeller of the centrifugal pump is coated with 2-3 layers of ultra-high molecular weight polyethylene modified with 7% silicon carbide content and particle size of 50 μm.

[0008] The invention is carried out as follows.

[0009] For comparative analysis, control samples of commonly used materials, such as fluoroplastic, nylon, stainless steel, and gray cast iron, were used. Specially prepared UHMWPE samples were modified by adding fine- and coarse-grained silicon carbide (SiC) filler (size range: 50 to 1000 µm) at various mass concentrations, using mechanical activation methods to uniformly distribute the particles within the polymer matrix.

[0010] The process of direct modification of UHMWPE with SiC particles was carried out through the following series of successive stages:

[0011] - the raw material UHMWPE was subjected to mechanical grinding to a homogeneous fraction;

[0012] - the selected type of filler was introduced into the resulting polymer matrix at the required mass concentration;

[0013] - to achieve the effect of uniform distribution of particles in the matrix, a laboratory mixer was used, while the mixing procedure lasted 0.5 hours, and the maintained temperature was 22°C;

[0014] - To form protective coatings, we used a method of applying (spraying) UHMWPE powder in an electrostatic field at a temperature of at least 220°C, producing a continuous film 50-200 µm thick on the metal surface. This process can be repeated if necessary. The resulting coating is characterized by high impact strength and bending elasticity. Adhesion of the coating to the metal using the cross-cut peeling method, in accordance with GOST 15140-78, is considered the best.

[0015] Data for objective evaluation of the resistance of samples to abrasive impact was obtained through mechanical testing on a friction machine, using the standard “pin-on-disk” scheme and a number of parameters reflected in Table 1 (see in the graphical part).

[0016] To fully simulate industrial testing, a rig simulating the operation of a centrifugal pump impeller was used. In particular, impellers made of cast iron SCh20 (GOST 1412-85) were prepared for industrial testing, and the protective coatings being studied were applied to some of them:

[0017] - on the first type of wheels studied, the surface of which was protected from wear using fluoroplastic, the protective material was applied by spraying, in a layer up to 0.5 mm thick;

[0018] - On another type of test wheel, the surface of which was protected from wear using modified UHMWPE+7% SiC, the protective material was applied using hot powder spraying in an electrostatic field at a temperature of at least 220°C, with the coating thickness ranging from 50 to 200 µm. There was no need to reapply the UHMWPE layer (visual inspection of the wheels).

[0019] The control sample consisted of standard cast iron wheels without any additional protection. All samples corresponded to the standard dimensions of the 5A-50 ESP.

[0020] The corrosion resistance of the samples was studied using the gravimetric method after their exposure to aggressive environments reproducing industrial operating conditions, reflected in Table 2 (see in the graphic section).

[0021] The tests lasted 720 hours. The evaluation was based on measurements of the change in mass of the test samples and a visual inspection of their surfaces.

[0022] The result of the invention was an increase in the average period of operational durability of the impeller of a centrifugal pump when in contact with an aggressive environment with the proposed model for producing layers by 30-40% compared to the average period of durability of known impellers of centrifugal pumps.

Claims

1. An impeller of a centrifugal pump with a coating of ultra-high molecular weight polyethylene, characterized in that it contains a cover disk, a main disk with working blades, and a metal disk placed and rigidly fixed between them, with a coating made on them of ultra-high molecular weight polyethylene modified by using coarse fractions of silicon carbide (SiC) as a filler, wherein the coating is applied in an electrostatic field at a temperature of at least 220°C, at which a continuous film 70 μm thick is formed on the surface of the metal, with a silicon carbide content of 7%.

2. The impeller of a centrifugal pump according to paragraph 1, characterized in that it is coated with 2-3 layers of ultra-high molecular weight polyethylene modified with a 7% content of silicon carbide with a particle size of 50 µm.

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