RU-2861485-C1 - THREADED CONNECTION FOR PIPES OF OILFIELD ASSORTMENT

RU2861485C1RU 2861485 C1RU2861485 C1RU 2861485C1RU-2861485-C1

Abstract

FIELD: pipes. SUBSTANCE: invention relates to threaded connections of pipe products of oilfield assortment, in particular to threaded connections of tubing or casing pipes. The threaded connection of pipes of oilfield assortment comprises a pin element and a box element. The pin element has an external tapered thread, a sealing surface, and a shoulder end. The box element has an internal tapered thread, a sealing surface, and a shoulder abutment. The sealing surface of the box element is made conical, and the sealing surface of the pin element includes a first curved surface, a conical surface, and a second curved surface, sequentially interfaced with each other. The first curved surface is located on the side of the shoulder end of the pin element and is formed by a convex arc with a radius of 5-105 mm. The second curved surface is located on the side of the thread of the pin element and is formed by a convex arc with a radius of 2-14 mm. The axial length of the generatrix of the conical surface of the pin element is 0.5-2 mm, and its angle of inclination to the axis of the pin element is 6-20 degrees. The angle of inclination of the generatrix of the conical sealing surface of the box element to its axis is greater than the angle of inclination of the generatrix of the conical surface of the pin element to its axis, while the difference between the angle values is less than two degrees. EFFECT: increasing the wear resistance of the sealing surfaces during the make-up of the threaded connection without a negative effect on the tightness of the connection in the assembled state. 2 cl, 6 dwg, 1 tbl

Inventors

NIKIFOROV DENIS VIKTOROVICH
Golobokov Oleg Sergeevich
Mishenkov Denis Vyacheslavovich

Dates

Publication Date: 20260505
Application Date: 20250911

Claims (5)

1. A threaded connection for oilfield tubular goods, comprising a nipple element and a coupling element, wherein the nipple element has an external conical thread, a sealing surface and a thrust end, the coupling element has an internal conical thread, a conical sealing surface and a thrust shoulder,
characterized in that the sealing surface of the nipple element includes a first curved surface, a conical surface and a second curved surface, successively connected to each other,
wherein the first curved surface is located on the side of the thrust end of the nipple element and is formed by a convex arc with a radius of 5-105 mm, the second curved surface is located on the side of the thread of the nipple element and is formed by a convex arc with a radius of 2-14 mm, the axial length of the generatrix of the conical surface of the nipple element is 0.5-2 mm, and the angle of inclination of the generatrix of the conical surface of the nipple element to its axis is 6-20 degrees,
wherein the angle of inclination of the generatrix of the conical sealing surface of the coupling element to its axis is greater than the angle of inclination of the generatrix of the conical surface of the nipple element to its axis, while the difference between the values of the said angles is less than two degrees.
2. The connection according to paragraph 1, characterized in that the angle of inclination of the surface of the thrust end of the nipple element relative to the normal to its axis is 12-20 degrees, the angle of inclination of the surface of the thrust shoulder of the coupling element relative to the normal to its axis is 12-20 degrees.

Description

Field of technology The invention relates to threaded connections of oilfield pipes, in particular to threaded connections of tubing or casing pipes. State of the art A threaded connection for oilfield pipes, disclosed in the description of the utility model to Russian Patent No. 158152 (published on December 20, 2015), was selected as a prototype. The threaded connection includes a nipple and a coupling element. The nipple element contains an external tapered trapezoidal thread, a conical sealing surface, and a thrust end. The coupling element contains an internal tapered trapezoidal thread, a conical sealing surface, and a thrust shoulder. The surface of the thrust end of the nipple element is formed at an angle ϕ 1 to the normal to the thread axis, and the surface of the thrust shoulder of the coupling element is formed at an angle ϕ 2 to the normal to the thread axis, where ϕ 1 < ϕ 2 . The angle ϕ 3 of inclination of the generatrix of the conical surface of the nipple element is less than the angle ϕ 4 of inclination of the generatrix of the conical surface of the coupling element, wherein ϕ 2 - ϕ 1 ≠ ϕ 4 - ϕ 3 . The sharp edge of the thrust shoulder of the coupling element is rounded, and the circle of rounding is located tangent to the surface of the thrust shoulder, and the center of the radius of the circle is on the line of the inner diameter of the coupling element along the axis of the connection, and the radius of rounding is not less than 2 mm. A disadvantage of the prototype is the low resistance of the sealing surfaces of the nipple and coupling elements to abrasion during make-up. This disadvantage is due to the design of the sealing surfaces of the nipple and coupling elements—both are conical, resulting in a "cone-on-cone" seal. When the connection is made, the sliding of these surfaces relative to each other occurs under high local contact pressure, which causes scoring. Attempts to improve the resistance of the conical sealing surfaces to abrasion during make-up by reducing the seal interference or by decreasing the contact sliding distance of these surfaces (by increasing their angle) will inevitably lead to a decrease in the tightness of the connection in the assembled state. Disclosure of the invention. The technical problem that the invention is aimed at solving is the need to improve the performance characteristics of threaded connections of oilfield pipes. The technical result that the invention is aimed at achieving consists in increasing the resistance of sealing surfaces to abrasion during the process of screwing together a threaded connection without negatively affecting the tightness of the connection in the assembled state. The essence of the invention is as follows. A threaded connection for oilfield tubular goods consists of a nipple and a coupling. The nipple has an external tapered thread, a sealing surface, and a thrust face. The coupling has an internal tapered thread, a conical sealing surface, and a thrust shoulder. Unlike the prototype, the sealing surface of the nipple element includes a first curved surface, a conical surface, and a second curved surface, sequentially mated with one another. The first curved surface is located on the thrust end face of the nipple element and is formed by a convex arc with a radius of 5-105 mm. The second curved surface is located on the thread side of the nipple element and is formed by a convex arc with a radius of 2-14 mm. The axial length of the generatrix of the conical surface of the nipple element is 0.5-2 mm, and the angle of inclination of the generatrix of the conical surface of the nipple element to its axis is 6-20 degrees. The angle of inclination of the generatrix of the conical sealing surface of the coupling element to its axis is greater than the angle of inclination of the generatrix of the conical surface of the nipple element to its axis, while the difference between these angles is less than two degrees. In a particular embodiment of the invention, the angle of inclination of the surface of the thrust end of the nipple element relative to the normal to its axis is 12-20 degrees, the angle of inclination of the surface of the thrust shoulder of the coupling element relative to the normal to its axis is 12-20 degrees. The aforementioned set of features of the invention, characterizing the design of the sealing surfaces of the nipple and coupling elements, reduces local contact pressure when the surfaces slide relative to each other during make-up, thereby increasing their abrasion resistance. Furthermore, after the sealing surfaces have finished sliding (when make-up is complete), the contact pressure achieved on the sealing surfaces ensures the required sealing of the connection. Brief description of the drawings The invention is illustrated by figures, where: - Fig. 1 shows a longitudinal sectional view of a threaded connection in a fully assembled state according to an embodiment; - Fig. 2 shows, on an enlarged