A plug for a pressure test configured for a tubular component, the tubular component including a male threaded element at a free end, the male threaded element including a male thread and a sealing surface, the plug including a thread compatible with the male thread, an inner annular groove, and a sealing ring held in the groove such that the sealing ring is radially compressed between an outer periphery of the male threaded element and a bottom of the inner annular groove.

A directly connected drill pipe applicable to extreme conditions includes a tool joint pin and a tool joint box, where an external pipe section is located on an external side of a threaded section of the tool joint pin, and an annular groove is formed between the external pipe section and the threaded section of the tool joint pin. An insertion section of the tool joint box can be inserted into the annular groove in a matched manner. A main shoulder of the tool joint pin is located at an end of the external pipe section, a main auxiliary shoulder of the tool joint pin is located on a bottom surface of the annular groove, and an auxiliary shoulder of the tool joint pin is located at a small end of the tool joint pin. The tool joint box has three corresponding shoulders which form a 3-stage sealing with the tool joint pin.

A method for assembling a threaded connection for a steel pipe, which connects a first pipe formed with a pin having a truncated cone shape at an end thereof, and a second pipe formed with a box having an opening end. The pin includes a male thread portion, which is a tapered thread, and a seal portion, which includes a tapered surface. The box includes a female thread portion, which is a tapered thread, and a seal portion, which includes a tapered surface. The tapered surface of the pin has a minimum diameter smaller than a maximum diameter of the tapered surface of the box. The method includes making-up the male thread portion and the female thread portion by screwing, whereby a root of the male thread portion and a crest of the female thread portion come into contact with each other after the seal portion of the pin and the seal portion of the box come into contact with each other.

High sealing performance is provided in a threaded connection used for pipes for oil wells with large wall thickness and with a connection efficiency smaller than 1. A threaded connection (10) connects pipes for oil wells (1). The threaded connection (10) includes two pins (11) and a tubular coupling. Each of the pins (11) is provided on an end of the pipe for oil wells (1) and is in continuity with the pipe body (12), which has a wall thickness not smaller than 12 mm. The coupling (2) includes two boxes (21) and a recess portion (22). The box (21) is provided on both ends of the coupling (2). The recess portion (22) has a length not smaller than 10 mm. The threaded connection (10) has a connection efficiency smaller than 1. When the wall thickness of the pipe body (12) is expressed as t.sub.pipe, the wall thickness and length of the recess portion (22) are expressed as t.sub.1 and 2×L.sub.1, respectively, and the length of each of the boxes (21) is expressed as L.sub.2, and if the following expressions (1) and (2) define T and L, then, T and L satisfy the following expression (3): $\begin{array}{cc}T=\frac{t_1}{t_{\mathrm{pipe}}}& \left(1\right)\\ L=\frac{L_1}{L_1+L_2}& \left(2\right)\\ T.Math.L^{1/15}>1.4& \left(3\right)\end{array}$

An object of the present invention is to provide a threaded connection that has high torque and still requires reduced machining time for the thread. A threaded connection (1) connects a pair of pipes. The threaded connection (1) includes a pin (10) and a box (20). The pin (10) has a male thread (11) on its outer diameter. The box (20) has a female thread (21) on its inner diameter, the female thread corresponding to the male thread (11). The box (20) and the pin (10) are made up. The male thread (11) includes a constant-thread-width portion (111) and a varying-thread-width portion (112). The constant-thread-width portion (111) has a constant thread-groove width. The varying-thread-width portion (112) has a thread-groove width equal to or larger than the groove width of the constant-thread-width portion (111) and gradually increasing, going from the constant-thread-width portion (111) toward the tip of the pin (10). The female thread (21) includes a constant-thread-width portion (211) and a varying-thread-width portion (212). The constant-thread-width portion (211) has a constant thread-ridge width. The varying-thread-width portion (212) has a thread-ridge width equal to or larger than the thread-ridge width of the constant-thread-width portion (211) and gradually increasing, going from the constant-thread-width portion (211) toward the center of the box (20).

An example fitting includes: a fitting body having counterbore, where the counterbore defines an annular shoulder within tire fitting body: a spring having a first end interfacing with the annular shoulder of the counterbore; and a seal carrier having: (i) a first end face interfacing with a second end of the spring, (ii) a second end face configured to interface with an internal surface of a port, such that the spring is configured to apply a biasing force on the seal carrier toward the internal surface of the port, (iii) a first annular groove on an exterior peripheral surface of the seal carrier, where the first annular groove is configured to have a radial seal disposed therein, and (iv) a second annular groove in the second end face, where the second annular groove is configured to have a face seal disposed therein.

A threaded connection for steel pipe is provided that prevents cross-threading and provides good compression load resistance. A threaded connection (10) includes a pin (30) and a box (40). The male thread stabbing flank (34) of the pin (30) includes two male thread stabbing flank portions (341) and (342). The male thread stabbing flank portion (341) is located farther from the pipe axis (X) of the steel pipe (20) and has a stabbing flank angle (α1) of −10 to 15 degrees. The male thread stabbing flank portion (342) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) of 20 to 60 degrees. The female thread stabbing flank (44) of the box (40) includes two female thread stabbing flank portions (441) and (442). The female thread stabbing flank portion (441) is located farther from the pipe axis (X) and has a stabbing flank angle (α1) equal to the stabbing flank angle (α1) of the male thread stabbing flank portion (341). The female thread stabbing flank portion (442) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) equal to the stabbing flank angle (α2) of the male thread stabbing flank portion (342).

The disclosed threaded connection for steel pipes includes a pin including a tapered male thread part and a shoulder part, and a box including a tapered female thread part and a shoulder part. In a made up state in which the shoulder parts are in contact with each other, clearances are provided between crests of the male thread part and roots of the female thread part. At a longitudinal section that includes a pipe axis of the threaded connection, the crests of the male thread part are formed in a convex curve that is tangent to both first corner portions which are formed in an arc that connect the crests and load flanks, and second corner portions which are formed in an arc that connect the crests and stabbing flanks. A solid lubricant coating is provided on the surface of the male thread part.

A directly connected drill pipe applicable to extreme conditions includes a tool joint pin and a tool joint box, where an external pipe section is located on an external side of a threaded section of the tool joint pin, and an annular groove is formed between the external pipe section and the threaded section of the tool joint pin. An insertion section of the tool joint box can be inserted into the annular groove in a matched manner. A main shoulder of the tool joint pin is located at an end of the external pipe section, a main auxiliary shoulder of the tool joint pin is located on a bottom surface of the annular groove, and an auxiliary shoulder of the tool joint pin is located at a small end of the tool joint pin. The tool joint box has three corresponding shoulders which form a 3-stage sealing with the tool joint pin.

A threaded connection partially in a self-locking arrangement includes a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. Only a portion of a first portion with varying thread width of the male threaded zone cooperates by self-locking tightening with only a portion of the second portion with varying thread width of the female threaded zone when made up one into the other. The connection is able to withstand high torques required for special applications such as drilling with casing or intermediate casing.