A threaded connection for steel pipe is provided that can be made up quickly and appropriately. The threaded connection includes a steel pipe 20m, a steel pipe 20f, and a coupling 50 for connecting the steel pipes 20m and 20f. The pipe bodies 21m and 21f of the steel pipes 20m and 20f include annular marking grooves 23m and 23f, respectively, formed on the outer peripheries of the pipe bodies 21m and 21f.

A tubular member includes a pin end terminating in a pin end face, an external thread profile defined on an outer circumference of the pin end and terminating at a thread termination location axially offset from the pin end face, and an axial extension provided on the pin end and extending axially from the thread termination location to the pin end face, the axial extension defining a gauge surface for obtaining diameter measurements of the pin end. An angle of the gauge surface aligns with an angle of a root plane provided by the external thread profile.

A threaded connection with good internal-pressure and external-pressure sealability while preventing galling is provided. A threaded connection 1 includes a pin 10 and a box 20. The pin 10 includes a pin lip 11, a pin metal seal 13, and a cylindrical inner machined surface 14. The pin metal seal 13 includes a pin seal taper surface 16 and a pin seal curvature surface 17. The box 20 includes a box metal seal 22 parallel to the pin seal taper surface 16. The pin metal seal 13 sealingly contacts the box metal seal 22 at a seal point SP. The threaded connection satisfies the following expressions, (1) and (2),

L>Lm>Ls  (1), and

tb/tp>1.6  (2).

L is the length of the pin lip 11; Lm is the distance between the tip AP of the pin and the end point of the cylindrical inner machined surface 14; Ls is the distance between the tip AP of the pin 10 and the seal point SP; tb is the wall thickness of the box 20 as measured at the seal point SP when the connection is made up; and tp is the wall thickness of the pin 10 as measured at the seal point SP.

A gas pipe joint contains: a connection pipe, a first threaded pipe, and a second threaded pipe. The connection pipe includes a first part and a second part, the first part has a first threaded orifice, and the second part has a second threaded orifice. The first threaded pipe includes a first coupling section, a first nut section, and a second coupling section. The second threaded pipe includes a second nut section and a third coupling section, the second nut section has a second screwing portion, and the third coupling section has at least one second recessed portion and a second groove. The third coupling section has a second shoulder. The second shoulder has a second lower gasket. The first groove has two first loops, and the second groove has two second loops.

A threaded connection for steel pipe with improved sealability against the internal and external pressures is provided. A threaded connection 1 includes a pin 10 and a box 20. The pin 10 includes a male thread 11, a nose 12, a pin shoulder surface 13, and a pin sealing surface 14. The box 20 includes a female thread 21, a box shoulder surface 23, and a box sealing surface 24. The box sealing surface 24 has a seal point SP on the taper surface 242 located at the midpoint thereof as determined along the direction of the pipe axis CL. The distance L.sub.SP between the tip of the nose 12 and the seal point SP as measured in the direction of pipe axis CL is 13 mm or larger. The shoulder angle α between the pin or box shoulder surface 13 or 23 and a plane VP perpendicular to the pipe axis CL is 2 to 13 degrees. The ratio T.sub.B/T.sub.P of the wall thickness T.sub.B of the box to the wall thickness T.sub.P of the pin 10 as measured at the seal point SP is 1.7 or higher.

An insulated tubular assembly includes jointed insulated tubing segments, all with inner and outer tubes concentrically disposed about in order to define a vacuum annulus in between and closed at both ends by annular bridges. Insulated tubing segment are provided with either male or female threads to threadably engage and form a joint directly with each other or through a coupling jointed to adjacent insulated tubing segments. An insulating sleeve held around such joint includes a first tubular shell adapted to cover at least part of one insulated tubular segment and a second tubular shell overlapping either internally or externally part of the first tubular shell, such that the second tubular shell extends axially about the threaded joint from one annular bridge to the adjacent one, with high tolerances on lengths of the insulated tubing segment extension extending beyond their respective annular bridges.

A screw joint has a tubular element with a female thread and a tubular element with a male thread, wherein the male thread and the female thread have first contact surfaces that cooperate with each other, and the tubular elements optionally have second contact surfaces adjacent to the female thread and/or the male thread, wherein the first contact surfaces and the optional second contact surfaces each have a coating including a first and a second layer, wherein the first layer is formed as a conversion layer in each case, one of the first contact surfaces that cooperate with each other has a second layer made of ceramic material with a friction reducing effect and the other of the two contact surfaces that cooperate with each other has, as a second layer, a varnish layer with a binding agent made of an organic polymer throughout which solid lubricant particles are distributed.

A connector for connecting pipes and for use with power tongs have a die length. The connector includes a body with threaded connection portions at each end of the body on an inside surface of the body. The connector includes a gripping surface defined on an outside surface of the body between the threaded connection portions. The gripping surface is at least as long as the die length. The connector includes a reinforced portion of the body proximate each of the threaded connection portions for increasing resistance to deformation of the body upon being connected with a pipe. The gripping surface and the reinforced portion together facilitate an increase in connection torque of pipes connected with the connector.

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).

A threaded tubular connection includes a tubular female end extending from a main body of a first tubular member, and a tubular male end extending from a main body of a second tubular member, such that the tubular male end includes a first machined inner surface close to the male free end and a second machined inner cylindrical surface above a threaded portion of the male end such that a second inner diameter of the second machined inner cylindrical surface is smaller than a first inner diameter of the first machined inner surface.