A method of transporting liquid petroleum gas (LPG) comprising coupling reverse thread fittings of a first tank to reverse thread fittings of a second tank, the first tank storing the LPG; and allowing the LPG to flow from the first tank to the second tank through the reverse thread fittings of the first tank and the reverse thread fittings of the second tank.

A method of transporting liquid petroleum gas (LPG) comprising coupling reverse thread fittings of a first tank to reverse thread fittings of a second tank, the first tank storing the LPG; and allowing the LPG to flow from the first tank to the second tank through the reverse thread fittings of the first tank and the reverse thread fittings of the second tank.

A threaded connection for steel pipe that provides both high torque performance and high tension performance is provided. A threaded connection 1 includes a tubular pin 10 formed by one tip portion of a steel pipe and a tubular box 20 adapted to be made up on the pin 10 as the pin 10 is inserted into the box. The pin 10 includes a male thread 11 provided on an outer periphery of the pin 10, the male thread being a wedge thread. The box 20 includes a female thread 21 corresponding to the male thread 11 and provided on the inner periphery of the box 20, the female thread being a wedge thread. The threaded connection 1 satisfies the following expression, (1):

3%≤(LP−SP)/LP≤8%  (1).

In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.

A threaded connection for steel pipe that provides both high torque performance and high tension performance is provided. A threaded connection 1 includes a tubular pin 10 formed by one tip portion of a steel pipe and a tubular box 20 adapted to be made up on the pin 10 as the pin 10 is inserted into the box. The pin 10 includes a male thread 11 provided on an outer periphery of the pin 10, the male thread being a wedge thread. The box 20 includes a female thread 21 corresponding to the male thread 11 and provided on the inner periphery of the box 20, the female thread being a wedge thread. The threaded connection 1 satisfies the following expression, (1):

3%≤(LP−SP)/LP≤8%  (1).

In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.

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.

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 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.

A flush self-locking threaded connection partially in a non-locking engagement comprises a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. First portions of the male and female threaded zones with varying thread width and root cooperate along a self-locking tightening arrangement. A locking region within the threaded connection is located in the middle of non-locking regions, and radially centered to the pipe body API tolerances in order to withstand high torque and seal performances.

A flush self-locking threaded connection partially in a non-locking engagement comprises a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. First portions of the male and female threaded zones with varying thread width and root cooperate along a self-locking tightening arrangement. A locking region within the threaded connection is located in the middle of non-locking regions, and radially centered to the pipe body API tolerances in order to withstand high torque and seal performances.

A tubular member includes a tube body, a tube end, an exterior surface, an interior surface, a nominal wall thickness, a longitudinal axis, a welded seam, and a patch of material. The welded seam forms an arcuate portion of the interior surface, and the patch covers a portion of the interior surface that includes a portion of the welded seam, extending from the tube end to an axially spaced first location. The resulting interior surface from the tube end to the axially spaced first location has a uniform inside diameter.