CN115450569A - Airtight seal thread with limiting shoulder - Google Patents

Abstract

The invention relates to the technical field of petroleum machinery, in particular to an air-tight screw thread with a limiting shoulder. The airtight thread includes a male thread on a male joint and a female thread on a female joint; a limited shoulder is provided on the male joint at the bottom of the public thread, and a tapered metal joint is provided on the outer wall of the male joint at the top of the male thread. Sealing surface I, the inner wall of the female joint at the bottom of the female thread is provided with a tapered metal sealing surface II. The invention realizes the gas-tight connection of the oil-casing pipe, satisfies the production requirements of deep wells, ultra-deep wells and high-pressure gas wells, optimizes the design of the metal sealing mechanism, reduces stress concentration, and sets the limit shoulder to simplify the installation operation.

Description

An airtight thread with a limiting shoulder

Technical field:

The invention relates to the technical field of petroleum machinery, in particular to an air-tight screw thread with a limiting shoulder.

Background technique:

Due to mature production technology and great price advantage, API threaded joints occupy an important position in the petroleum industry, accounting for half of the world's oil and casing usage. However, its own performance has certain limitations, and it cannot achieve gas sealing. With the large-scale development of deep wells, ultra-deep wells, and high-pressure gas wells, API threaded joints can no longer fully meet the requirements of the petroleum industry.

In the 1960s, the United States first developed the elastic sealing ring plug type oil casing sealing thread structure, but this kind of sealing is prone to failure when the internal/external pressure is high, and its service life is short. Subsequently, many companies at home and abroad have developed metal-to-metal sealed oil casing threaded joints. The sealing positions are all at the sharp corners of the mating bottom of the male and female joints. When sealing, it is easy to generate a large stress concentration. If the installation torque is too large, it is easy to cause If the seal is invalid and the torque is too small, the thread cannot be tightened, and there is a high risk. Therefore, when installing the oil casing with this type of thread, there are strict requirements on the installation torque, and it must be completed under the professional guidance of the manufacturer.

Invention content:

The technical problem to be solved by the present invention is to provide a gas-sealed thread with a limiting shoulder. The gas-sealed thread is equipped with a metal sealing mechanism, which realizes the gas-tight connection of the oil casing and meets the requirements for deep wells, ultra-deep wells, and high-pressure gas wells. , Optimize the design of the metal sealing mechanism, reduce the stress concentration, set the limit shoulder, and simplify the installation operation. It overcomes the problems that the existing oil casing sealing thread structure adopts a sharp-angle contact metal seal, which causes large stress concentration during sealing, low axial deviation tolerance, easy sealing failure, and strict requirements on installation torque during installation.

The technical solution adopted by the present invention is: an air-tight thread with a limit shoulder, including a male thread arranged on a male connector and a female thread arranged on a female connector; the male connector at the bottom of the male thread has a limited There is a tapered metal sealing surface Ⅰ on the outer wall of the male joint at the top of the male thread, and a tapered metal sealing surface Ⅱ on the inner wall of the female joint at the bottom of the female thread. The above-mentioned male thread and the above-mentioned female thread are tightened to the female joint. When the end face and the limit shoulder of the male joint are fully fitted, the male thread and the female thread reach the optimum tightening torque position of the thread, and at the same time, the conical metal sealing surface I and the conical metal sealing surface II complete the cooperation to form a metal seal.

The slope of the conical metal sealing surface I is 10-15°.

The beneficial effects of the present invention are:

(1) The end is sealed with a small-angle surface metal to reduce the stress concentration of the seal, the connection reliability is good, and the service life is long;

(2) Double thread seal and metal seal, good sealing performance;

(3) Designed with a limited shoulder, the buckle-up operation is convenient, and the installation accuracy is easy to ensure;

(4) Low installation requirements and good economy.

Description of drawings:

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 is a schematic diagram of the structure of a male thread.

Figure 2 is a schematic diagram of the structure of the female thread.

Fig. 3 is a schematic diagram of the mating of male and female threads.

detailed description:

As shown in Figure 1, Figure 2, and Figure 3, an air-tight thread with a limit shoulder includes a male thread set on the male joint 1 and a female thread set on the female joint 4; the bottom of the public thread A limited shoulder 2 is provided on the male joint 1, a tapered metal sealing surface I3 is provided on the outer wall of the male joint 1 at the top of the male thread, and a tapered metal sealing surface II5 is provided on the inner wall of the female joint 4 at the bottom of the female thread. When the screw thread and the above female thread are tightened until the end face of the female joint 4 and the limit shoulder 2 of the male joint 1 are fully fitted, the male thread and the female thread reach the optimal tightening torque position of the thread, and the tapered metal sealing surface I3 and the tapered The metal sealing surface II5 completes the fit to form a metal seal.

The slope of the conical metal sealing surface I3 is 10-15°.

The metal seal of the present invention adopts a small-angle conical surface seal, and compared with the existing air-tight thread sharp-angle contact metal seal, the stress concentration is small, and the axial deviation tolerance is high. The thread of the present invention is optimized in API thread technology, and can form a seal in the tightened state. When installing, tighten until the end surface of the female thread and the limiting shoulder 2 of the male thread are completely attached, that is, the optimal tightening torque position of the thread is reached. , can ensure reliable connection and complete thread sealing. At the same time, in this installation position, the conical metal sealing surface I3 on the top of the male thread and the conical metal sealing surface II5 on the bottom of the female thread complete the cooperation, which can activate the metal seal at the end and complete the secondary sealing.

It can be understood that the above specific descriptions of the present invention are only used to illustrate the present invention and are not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or Equivalent replacements to achieve the same technical effect; as long as they meet the needs of use, they are all within the protection scope of the present invention.

Claims (2)

1. An air-tight thread with a limit shoulder, comprising a male thread arranged on a male joint (1) and a female thread arranged on a female joint (4); it is characterized in that: the male joint at the bottom of the male thread (1) is provided with a limited shoulder (2), the outer wall of the male joint (1) at the top of the male thread is provided with a conical metal sealing surface I (3), and the inner wall of the female joint (4) at the bottom of the female thread is provided with a cone When the above-mentioned male thread and the above-mentioned female thread are tightened until the end surface of the female connector (4) and the limit shoulder (2) of the male connector (1) are fully fitted, the male thread and the female thread reach The optimal tightening torque position of the thread, meanwhile, the conical metal sealing surface I (3) and the conical metal sealing surface II (5) complete the cooperation to form a metal seal. 2. The air-tight screw thread with a limiting shoulder according to claim 1, characterized in that: the slope of the conical metal sealing surface I (3) is 10-15°.

Images