RU2187616C1 - Method of manufacture of rotor tubular shell of screw downhole motor - Google Patents

Abstract

FIELD: equipment for drilling of oil and gas wells. SUBSTANCE: the essence of invention consists in that forming of screw teeth on tubular shell is effected by action of fluid medium pressure with use of forming member with external screw teeth onto external surface of tubular blank. In this case, prior to withdrawal of forming member from formed tubular shell of rotor, lubricant is introduced under pressure into gap between them for expansion of tubular shell. EFFECT: provided easy withdrawal of forming member from formed tubular shell of rotor and prolonged service life of forming member. 2 cl, 4 dwg

Description

 The invention relates to techniques for drilling oil and gas wells, and in particular to methods for manufacturing a tubular shell of rotors of downhole motors for drilling oil and gas wells. The invention can also be used for the manufacture of rotors of screw pumps for oil production and pumping liquids, as well as for the manufacture of rotors of screw hydraulic machines for general purposes.

 A known method of manufacturing a tubular shell of a rotor of a downhole screw motor (USSR patent 1218740, Mcl E 21 In 4/02, publ. 01.20.2000). The method includes the shaping of helical teeth on a tubular shell by the influence of the pressure of the current medium on the outer surface of the tubular billet, inside which a forming element with external helical teeth is installed, which is removed from the tubular shell after stamping.

 When the helical teeth of the tubular shell are shaped in contact with the outer helical teeth of the forming element and the inner surface of the tubular workpiece of the helical teeth of the tubular shell, high contact stresses develop. In this process grease, which covers the forming element before stamping, is squeezed out of the contact zone, resulting in increased frictional forces that must be overcome when removing the forming element from the tubular shell, resulting in "setting" of the materials of the forming element and the tubular shell with subsequent by scoring their helical teeth.

 These disadvantages are partially eliminated in the known method of manufacturing a tubular shell of a rotor of a downhole motor (USSR patent 1688615, M. CL E 21 B 4/02, publ. 07/10/2000), which includes shaping the surface of the tubular shell by applying pressure to the tubular billet environment using a forming element with helical teeth, and inside the tubular workpiece before placing it on the forming element is introduced to the entire length and along the entire inner surface to be deformed, a foil of plastic an tritification material. In practice, copper foil was used as a plastic antifriction material, which reduced the friction forces when the forming element was removed from the tubular shell.

 The use of copper foil made it possible to somewhat facilitate the extraction of the forming element from the tubular shell and increase its durability. However, copper foil subjected to high contact loads does not exclude the risk of scoring on the teeth of the forming element. As practice has shown, sometimes when removing the forming element from the tubular shell of the rotor, the copper foil breaks and abrases on the mating surfaces, which leads to scoring of the surface of the forming element, heating of the tubular shell of the rotor and the forming element. These disadvantages are manifested especially in the manufacture of multi-step tubular shells of the rotor, as well as in the manufacture of tubular shells of the rotor having a reduced pitch of helical teeth.

 The objective of the present invention is to eliminate the disadvantages of the known method, facilitate the removal of the forming element from the molded tubular shell of the rotor and increase the durability of the forming element.

 The problem is solved in that in the known method of manufacturing a tubular shell of a rotor of a downhole motor, comprising shaping helical teeth on a tubular shell by exposing the outer surface of the tubular billet with fluid pressure using a forming element with external helical teeth and removing the forming element from the tubular shell, according to the invention before removing the forming element from the molded tubular shell of the rotor in the gap between them is introduced lubricant Pressure to expand the tubular sheath.

 Another difference is that the lubricant is introduced into the gap between the forming element and the molded tubular shell of the rotor under pressure, which ensures the expansion of the tubular shell within its elastic deformation.

 When a lubricant under pressure is introduced into the gap between the tubular shell and the forming element to expand the tubular shell, the outer diameter of the tubular shell increases, and the lubricant penetrates into the gap between the molded tubular shell and the forming element, thereby facilitating the removal of the forming element. When, after depressurizing the lubricant, the molded tubular shell undergoes a reduced (former) size due to elastic deformations, the lubricant remains in the gap between the molded tubular shell and the forming element. Due to this, it is easier to remove the forming element from the molded tubular shell, it is carried out with the application of less axial force, while the galling on the forming element is eliminated.

 The proposed method of manufacturing a tubular shell of a rotor of a downhole screw motor is illustrated by drawings.

In FIG. 1 is a longitudinal sectional view of a portion of a device for implementing the method prior to hydraulic stamping;
figure 2 shows a cross section along section aa of figure 1;
figure 3 shows a part of a device for implementing the method after hydraulic stamping;
figure 4 shows a cross section along section BB of figure 3.

 To implement the method of manufacturing the tubular shell of the rotor, the assembly of the device is carried out. On the forming element 1 (Fig. 1, 2), a tubular billet 2, centering sleeves 3 are installed and fastened with nuts 4 along the end threads 5 of the forming element 1. The centering sleeves 3 are sealed along the necks of the forming element 1 and the end sections of the tubular billet 2 with sealing rubber rings 6 and 7. In the forming element 1, an axial channel 8 and a radial hole 9 are made, which extends into the cavity 10 of the tooth 11 of the forming element 1.

 A method of manufacturing a tubular shell is implemented as follows. A forming element 1 with a tubular billet 2 mounted on it, centering sleeves 3 and nuts 4 is inserted into the hydraulic stamp housing (not shown), sealed and fixed in it. A high-pressure fluid is supplied into the sealed cavity of the hydraulic stamp body, which acts on the outer surface of the tubular workpiece 2. As a result, screw teeth 12 are formed on the tubular shell of the rotor 13 (Fig. 3, 4), while air from the cavity between the forming element 1 and the tubular blank 2 exits through openings 8 and 9.

 At the end of the hydraulic stamping process, before removing the forming element 1 from the molded tubular shell of the rotor 13, a lubricant under pressure is introduced into the gap between them through the axial 8 and radial 9 holes of the forming element 1. The tubular shell of the rotor 13 expands within the elastic deformation, and gaps filled with grease are formed between the teeth 11 of the forming element 1 and the inner surface of the tubular shell of the rotor 13.

 After depressurization of the lubricant, the tubular shell of the rotor 13 under the action of the elastic forces of the material returns to its original size, but the lubricant layer in the contact zone of the forming element 1 and the tubular shell of the rotor 13 is maintained. Therefore, the removal of the forming element 1 from the tubular shell of the rotor 13 occurs with reduced axial force and without scoring on the helical teeth 11 of the forming element 1.

 Example. For the manufacture of the tubular shell of the rotor, a tubular billet with a diameter of 57 mm and a wall thickness of 3.5 mm from corrosion-resistant steel 12X18H10T was used. Hydraulic stamping was carried out at a fluid pressure of 250 MPa. After hydraulic stamping, a lubricant (industrial oil) was introduced at a pressure of 20 MPa into the gap between the outer surface of the forming element 1 and the inner surface of the molded tubular shell of the rotor 13, while the diameter of the tubular shell of the rotor 13 increased by 0.1 mm After depressurization, the diameter of the tubular shell of the rotor 13 returned to its original value, that is, the tubular shell of the rotor 13 expanded within the elastic deformation. Removing the forming element 1 from the tubular shell of the rotor 13 occurred with a reduced by 2 times the traction forces (50 kN) and without damage to the forming element 1 and the tubular shell of the rotor 13.

 Thus, by introducing lubricant under pressure into the gap between the tubular shell of the rotor 13 and the forming element 1, a significant reduction in the axial forces required for disassembling is ensured, the molding element 1 is easier to remove from the molded tubular shell of the rotor 13, gouges on the forming element 1 are eliminated, and productivity is increased the manufacturing process of the tubular shell of the rotor 13 of the downhole motor and costs are reduced.

Claims (2)

 1. A method of manufacturing a tubular shell of a rotor of a downhole motor, comprising shaping helical teeth on a tubular shell by exposing the outer surface of the tubular workpiece to fluid pressure using a forming element with external helical teeth and removing the forming element from the tubular shell, characterized in that before removing the forming an element of the molded tubular shell of the rotor is introduced into the gap between them under pressure lubrication to expand the tubular shell.  2. The method according to claim 1, characterized in that the lubricant in the gap between the forming element and the molded tubular shell of the rotor is injected under pressure, which expands the tubular shell within its elastic deformation.

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