RU2450408C2 - Electrochemical protection of vetokhin asynchronous machine for oil and gas wells (vamogw) - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: asynchronous machine (VAMOGW) includes frame (1) with multipack stator (2) with winding (3), at monolithic shaft (6) made of steel 20X13 there is multi-pack rotor (7) with copper bars (8) and cafe rings (9). Between packs of stator (2) and rotor (7) there is non-magnet gap (5) through which cooling stratum water passes. In order to prevent contact corrosion of electric steel of stator and rotor packs and copper of rotor winding discs (10) of magnesium alloy are pressed-fit between packs on rotor shaft and rings (4) of the same alloy are pressed-fir between stator packs. Discs (10) and rings (4) have close electric contact with packs of rotor (7) and stator (2).

EFFECT: effective electrochemical protection from contact corrosion for internal parts of multipack rotors and stators of vertical open electric machines at their immersion to aggressive stratum water - electrolyte.

3 dwg

Description

The invention relates to the field of electrical engineering, in particular to submersible electric machines, which are used for drives of various underwater mechanisms of drilling and production facilities in the development and production of minerals and mineral resources of oil and gas on the seabed, as well as for drives of downhole pumps and drilling mechanisms in exploration and industrial development of the offshore continental shelf for oil and gas.

Scientific and technological progress and prospects for the development of intensive development of the extraction of mineral resources on the continent and on the continental shelf, the development of new oil and gas fields in the Siberian energy region of Tyumen, Orenburg, etc., and due to the increase in the depth of oil deposits to 3000 m, a lot of technical means are required and operating mechanisms that must be driven by highly reliable submersible electric motors (SEMs). To date, sealed oil-filled PEMs with a rather complex multi-stage hydraulic protection installed on the drive shaft side have been used to drive oil well pumps and drilling rigs. When it is bent and formation water enters the engine cavity, it fails due to corrosion of the active parts and a decrease in the insulation resistance of the stator winding. PEM is cooled by formation fluid through the housing, for example, submersible motors for pumps and electric drills of the Kharkov Electromechanical Plant (KHEMZ) and the Special Design and Engineering Bureau of Submersible Electrical Equipment for Drilling Wells and Oil Production “Potential” (SKTBPE “Potential”, Kharkov, GOST 18058-80). For pumps of oil wells with immersion to a depth of 3000 m, the company "ALNAS" in Moscow developed a submersible electric motor of the type PEDS360-130MV5 when working in wells with formation fluid temperatures up to 150 ° C. In order to equalize temperatures throughout the entire internal volume of the engine, the rotor shaft is hollow, through the central opening of which the oil is circulated inside the machine.

The main disadvantages of these PED are:

1. The cooling system of existing sealed PEMs designed to operate at a depth of 3000 m, due to the high temperatures of the formation fluid medium reaching 150 ° C, is not effective enough.

2. Hydroprotection of various designs of sealed SEMs has low operational reliability.

3. Sealing of PEM leads to a significant increase in the temperature of the stator winding to and above 200 ° C, which reduces the reliability of the winding wire and bearings.

4. Failures of hydraulic protection (depressurization of the compensating element, wear of seals, etc.) leads to the penetration of aggressive formation fluid into the cavity of the PED and its premature failure, mainly due to electrochemical corrosion.

Known submersible pumping unit vertical design as.with. No. 939830, which contains a stator, a rotor with a shaft mounted in bearings, and bearing shields with holes for fluid inlet and outlet. A pump is mounted on the rotor shaft, which drives the coolant through the lower holes in the housing through the gap between the rotor and the stator, as well as through the upper hole in the pump housing and supplies this fluid to the consumer. This pump unit is used in wells for pumping fresh water. When immersed in aggressive acidic water with a pH <7, it will fail due to electrochemical corrosion of the active parts of the machine, bearings and windings of the stator and rotor.

Known open-type electric machine for working in sea water at any diving depth with cooling of the internal active parts of sea water outside (see "Vetokhin Electric Machine", patent No. 2072609, BI No. 3, 01/27/97), which contains a stator, a rotor with a shaft and bearings enclosed in an unpressurized housing filled with a liquid cooler, and bearing shields with holes. Sea water was used as a cooler, and the holes in the bearing shields for cold water inlet and heated water outlet were located in two groups. The main disadvantage of the known EME is that when an open-type machine is immersed in sea water, which in this case is not only a cooler, but also an electrolyte with ionic conductivity, which is in motion from the rotation of the rotor, electrochemical processes occur on its internal parts, causing electrochemical contact corrosion, mainly of electrical steel of the rotor surface and the stator bore, which leads to an increase in the non-magnetic working gap, as the main parameter of the electric trichesky machine. Due to the increase in the non-magnetic gap, as the main parameter of the electric machine, the no-load current increases, the power factor, efficiency, starting and rated torque decrease, and therefore, the required energy characteristics of the electric machine will not be provided.

Of the known devices closest to the claimed one selected for the prototype, is the "Electric machine Vetokhin EMV" (see patent No. 1813228, BI No. 16, 04/30/93), which contains a stator and a rotor with a squirrel-cage winding, consisting of copper rods and copper shorting rings. Cooling is carried out by the surrounding fluid entering through openings in the bearing shields. To protect against contact corrosion of the internal active parts of the machine, protectors made of aluminum alloy are pressed from both ends on the rotor shaft and in the stator housing, the length of which in the axial direction is from 0.05 to 0.1 of the length of the core package. The disadvantage of this design of EMV for oil wells is the commensurability of the diameter and length of the large rotor for large machines of high power, which cannot be implemented in submersible motors for pumps and "Burov" mechanisms for oil and gas wells. Submersible electric motors for oil and gas wells have a small diameter of up to 150 mm, and lengths for large engine capacities reach 8 m, with hydraulic protection up to 16 m, in which the stators, rotors and hydraulic protection are multistage, therefore, in these machines, the protector tread protection will not ensure the suspension of contact corrosion along the entire length of the non-magnetic gap of the multi-stage stator and rotor. In this case, only the outermost packages will be protected, and further to the center of the machine, the effect of protection from mechanical tread bushings and rings will decrease. Physically, this means that when the machine is immersed in produced water, the electrolyte at its ends in the extreme packets, the surface of the stator bore and the surface of the rotor barrel are the cathodes (input of the anode current), and the tread sleeves are the anodes (output of the anode current), it is known that the cathodes will be keep their condition, the anodes will corrode, i.e. dissolve in electrolyte. In this case, the extreme packages of the stator and rotor will be in the initial state, and the protectors will corrode and decrease in size. In the central rotor packages, the copper rotor rods will be cathodes (anode current input), and the stator and rotor packages steel will be anodes (anode current output), so the copper rods of the short-circuited rotor winding will be in the initial state, and the steel of the stator and rotor packages in the non-magnetic working gap will corrode, resulting in an increase in equivalent working clearance. Due to the increase in the non-magnetic gap, as the main parameter of the electric machine, the no-load current increases, the power factor, efficiency, starting and nominal moments decrease, and therefore, the required energy characteristics of the electric machine are not provided.

The aim of the invention is to increase the reliability, survivability, durability and energy characteristics of the developed asynchronous machine (AMS NGS) by eliminating contact corrosion of the surfaces of electrical steel of the stator bore and the rotor barrel in a non-magnetic gap using tread rings and tread disks placed between the stator and rotor packages.

This goal is achieved by the fact that in the well-known vertical asynchronous submersible electric machine containing a stator with a core, yoke and grooves, a rotor-groove rotor, a shaft supported by bearings, tread protection of the stator and rotor enclosed in a housing with holes for the input and output of the surrounding formation aggressive with electrolytic properties of water for cooling, the shaft is made monolithic and rotor packets are pressed onto it along a sliding fit through the key, and between them onto the shaft, with tight electric 5-8 mm thick tread disks made of aluminum-magnesium-zinc alloy having holes for rotor winding rods are pressed by a contact to the rotor packages, while the same number of tread rings of the same thickness are made between the stator packages of the same thickness from the same alloy with an inner diameter, equal to the inner diameter of the back of the stator yoke, in addition, protector rings of the same thickness and depth equal to 5-8 mm made of stator protector alloy are pressed into the inside of the housing.

The invention is illustrated by drawings, in which:

- figure 1 shows a longitudinal section of the AMV NGS;

- figure 2 shows the tread disk of the rotor;

- figure 3 shows the tread ring of the stator.

According to the invention (FIG. 1, FIG. 2), an asynchronous machine (AMS NGS) comprises a housing 1, in which stator packages 2 with a long winding 3 from a winding wire with polyimide-fluoroplastic insulation, for example, PPI-U brand, are placed. On the monolithic shaft 6 there are placed packages 7 of the rotor having a short-circuited winding of rods 8 and short-circuited rings 9. Between the packages of the rotor and the stator there is a non-magnetic working gap 5 through which cooling aggressive formation water with electrolyte properties passes. The stator has a tread protection against contact corrosion of the core package 2 in the form of rings 4 (Fig. 1, Fig. 3), for example, of a magnesium alloy of the ML4 brand. The rotor has tread protection against contact corrosion of the core package of the rotor 7 in the form of disks 10 of the same alloy (Fig. 1, Fig. 2). Since the developed machine has a large length and multi-packet stator and rotor, it is impossible to effectively implement the entire gap length to protect electrochemically against contact corrosion of all surfaces of the stator and rotor packages in a non-magnetic working gap with two protectors located close to the extreme end packages of the stator and rotor. as in the prototype. The extreme packages of the stator and rotor will be protected, since in this case the galvanic current flows through the smallest ohmic resistance along the circuit from the cathode (stator package) 2 to the anode (protector from magnesium alloy) 4, leaves the anode 4 into formation water - electrolyte 5 passes through it and enters the cathode — stator package 2. Thus, the anode 4 will release positive atoms into water 5 (the output of the anode current) and will collapse (corrode) over time, i.e. decrease in size, and on the cathode 2 the excess electrons remaining in the metals and negative ions of the solution — produced water (input of the anode current) will be assimilated, and the cathode or stator package 2 will be in its original state. Corrosion products of the anode - tread will be removed by moving water-electrolyte into the environment. In the central part of the non-magnetic gap, the influence of treads on corrosion protection of stator and rotor steel packets due to the distance and increase in electrical resistivity for the passage of anode current from central stator and rotor steel packets to treads and then to be closed through water decreases sharply. Other galvanic circuits will operate, namely: galvanic current will flow through the circuit from the cathode (copper of the short-circuited rotor winding) 8 to the anode (rotor steel package) 7, electrolyte 5 will leave the anode into water, pass through it and enter the cathode - copper of rotor 8. From this it follows that the steel of rotor 7 and stator 2 carry anode properties - the output of the anode current will corrode and decrease in size, and the copper of the winding of the rotor 8 will carry the cathode properties - the input of the anode current, will not corrode and will be in source thawing. As a result, during operation of the electric motor over time, uneven corrosion of the stator 2 and rotor 7 packages in the non-magnetic gap will occur, which will increase the value of the gap 5, and therefore, the energy performance of the machine will decrease. To eliminate this drawback, it is necessary to install tread rings 4 on the end packages of the stator 2 and rotor 7, and also between all central packages of the stator 2 and between the packages of the rotor 7 disks 10 of the same size from one aluminum-magnesium alloy, as a result, the symmetry of the galvanic circuits will be observed and corrosion of the packages of the stator 2 and rotor 7 will be suspended. To eliminate the influence of the ends of the housing on galvanic pairs and the stator and rotor circuits, it is necessary to press in the ends of the housing tread rings of the same alloy and with the dimensions of the stator rings (not shown in the drawings).

When developing the design of tread rings and discs, it is necessary to proceed from the maximum corrosion rate of aluminum-magnesium protectors with electrical contact with the steel of the stator and rotor packages, as well as with the copper of the rotor, which is in the range 0.4-0.5 mm / year, and the service life (service), in this case, the service life is 10 years. Based on this, the thickness of the treads in the axial and radial directions should not be less than 5.0 mm, taking into account the stock, you can accept the geometric dimensions of the treads in the range of 8-10 mm for any number of stator and rotor packages.

The operation of an asynchronous machine is as follows.

When the rotor rotates in cooling formation water (electrolyte), the rotor and stator are in a moving electrolyte environment. With the full contact of all internal active parts of the machine with the electrolyte, electrochemical corrosion occurs on all active metal surfaces in contact with the electrolyte, i.e. on the surfaces of packages 7 of the rotor, on the surfaces of the bores of packages 2 of the stator, on copper rods 8 and short-circuit rings 9 of the rotor, on the surfaces of the tread disks 10 of the rotor and rings 4 of the stator. Due to the fact that the electrode potential of the rotor disks 10 and stator rings 4 made of magnesium alloy of the ML4 brand is much lower than the electrode potential of the electrical steel of stator packages 2, rotor packages 7 and copper rods 8 with short-circuiting rings 9 of the rotor winding, then there is electrochemical corrosion of the tread disks 10 of the rotor and the tread rings 4 of the stator with leaching of corrosion products by a moving electrolyte. Therefore, the tread material will be consumed, and the remaining metal parts of the machine will be in their original state for the estimated and planned life without increasing the magnitude of the non-magnetic working gap and the associated fall in the energy characteristics of the machine, which will be constant throughout its life. The thickness of the rotor disks 10 and tread rings 4 of the stator made of aluminum-magnesium alloy should be in the range of 5-8 mm at a corrosion rate of treads of 0.5 mm / year.

The claimed technical solution can significantly improve the performance, reliability, survivability, durability and energy characteristics of the developed asynchronous machine (AMV NGS) by eliminating contact corrosion of the surfaces of electrical steel of the stator bore and the rotor barrel in a non-magnetic gap using tread rings and tread disks placed between the packages stator and rotor.

Claims (1)

An asynchronous machine (АМВ НГС) of vertical design, comprising a stator with a core, yoke and grooves, a rotor-groove rotor, a shaft supported by bearings, tread protection of the stator and rotor enclosed in a housing with openings for the entry and exit of surrounding formation water with electrolytic properties of water for cooling, characterized in that the shaft is made monolithic and rotor packages are pressed onto it in a sliding fit through the key, and between them onto the shaft are threaded with a tight electrical contact to the pressure rotor packages 5–8 mm thick tread disks of aluminum-magnesium-zinc alloy are provided, having holes for rotor winding rods, while the same number of tread rings of the same thickness are made between the stator packs from the same alloy with an inner diameter equal to the inner diameter of the back of the yoke stator, in addition, protector rings of the same thickness and depth equal to 5-8 mm made of an alloy of stator protectors are pressed in along the ends of the housing.

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