Nippon Steel Corporation

Vallourec Oil and Gas France

Nippon Steel Sumitomo Metal Corporation

Keita Inose

Masaaki Sugino

Hikari Nakano

Shin Ugai

Fumio Ota

Yousuke Oku

Takashi Okada

Suguru Yamaguchi

Sadao Douchi

A threaded connection for steel pipe is provided in which galling does not easily occur on any of the inner and outer threads. A threaded connection for steel pipeincludes a pinand a box. The pinincludes: a nose; a tapered inner male thread; a tapered outer male thread; a pin inner sealing surface; a pin intermediate shoulder surface; and a pin intermediate sealing surface. The boxincludes: a tapered inner female thread; a tapered outer female thread; a box inner sealing surface; a box intermediate shoulder surface; and a box intermediate sealing surface. Each of the inner male thread, outer male thread, inner female threadand outer female threadincludes a perfect thread portion. Each perfect thread portion includes an inner end located relatively close to the tip of the pinand an outer end located relatively close to the end of the pinopposite to its tip. The threaded connection for steel pipesatisfies the following Expressions (1) and (2):  (1), and  (2).

Threaded connection for steel pipe

A disclosed threaded connection for steel pipes includes a pin and a box. The pin includes, in order from a front end of the pin toward a pipe body of the pin, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a male thread part. The box includes, in order from a pipe body of the box toward a front end of the box, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a female thread part. The pin shoulder surface and the box shoulder surface incline from a plane perpendicular to a pipe axis in a direction of screwing the pin. A diameter of an inner circumferential edge of the pin shoulder surface is smaller than a diameter of an inner circumferential edge of the box shoulder surface.

Threaded connection for steel pipes

A two-step threaded connection for steel pipe includes an intermediate seal and intermediate shoulders. A pinhas an inner male-threaded sectionand an outer male-threaded sectionA boxhas an inner female-threaded sectionand an outer female-threaded sectionThe pinhas a pin intermediate critical cross section PICCS located near an end of the first male-threaded sectionThe boxhas a box critical cross section BCCS located near an end of the inner female-threaded sectionand a box intermediate critical cross section BICCS located near an end of the outer female-threaded section The pinand the boxsatisfy the following relationships:PICCSA+BICCSA&#x3e;BCCSA, and0.70&#x2264;PICCSA/BICCSA&#x2264;0.95.

A threaded connection with good internal-pressure and external-pressure sealability while preventing galling is provided. A threaded connectionincludes a pinand a box. The pinincludes a pin lip, a pin metal seal, and a cylindrical inner machined surface. The pin metal sealincludes a pin seal taper surfaceand a pin seal curvature surface. The boxincludes a box metal sealparallel to the pin seal taper surface. The pin metal sealsealingly contacts the box metal sealat a seal point SP. The threaded connection satisfies the following expressions, (1) and (2),&#x2003;&#x2003;(1), and&#x3e;1.6&#x2003;&#x2003;(2).L is the length of the pin lip; Lm is the distance between the tip AP of the pin and the end point of the cylindrical inner machined surface; Ls is the distance between the tip AP of the pinand the seal point SP; tb is the wall thickness of the boxas measured at the seal point SP when the connection is made up; and tp is the wall thickness of the pinas measured at the seal point SP.

A threaded connection for steel pipes having improved sealing performance is provided. A threaded connection () for steel pipes includes a pin () and a box (). The pin () includes a nose (), a pin shoulder surface (), a pin sealing surface () and a male thread (). The box () includes a box shoulder surface (), a box sealing surface () and a female thread (). When the position of the portion of the pin sealing surface () that first contacts the inner periphery of the box () during make-up defines a seal position (P), the distance between the seal position (P) and the end of the male thread () adjacent to the pin sealing surface () as measured in the pipe-axis direction is denoted by x, and the distance between the tip of the pin () and the end of the male thread () adjacent to the pin sealing surface () as measured in the pipe-axis direction is denoted by L, then, x/L is not smaller than 0.4 and not larger than 0.55.

A threaded connection for steel pipe is provided that improves its internal-pressure sealability while maintaining the high external-pressure sealability of a threaded connection having a nose used in a steel pipe with large diameter and large wall thickness. In a threaded connection for connecting steel pipe bodies each having an outer diameter equal to or larger than 7 inches and a wall thickness equal to or larger than 0.7 inches, Expression (1) in the description is satisfied and t/t&#x3e;1.4, where &#x3b4; [mm] is the clearance between the outer surface of the pin and the inner surface of the box upon make-up as measured at the borderline between the pin taper surface and the pin round surface, D [inch] is the outer diameter of the steel pipe body, t [inch] is the wall thickness of the steel pipe body, L [mm] is the distance between a pivot point, which is a position, in the region of contact between the pin sealing surface and the box sealing surface, which is closest to the tip of the pin, and the tip of the pin upon make-up as measured along the pipe-axis direction, t[mm] is the wall thickness of the pin as measured at the pivot point, and t[mm] is the wall thickness of the box as measured at the pivot point.

A threaded connection for steel pipes is provided that exhibits improved sealability against the external pressure while maintaining the sealability against the internal pressure. A threaded connection for steel pipes includes a pin and a box. The pin includes a nose, a tapered inner male thread, a tapered outer male thread, a pin inner sealing surface, a pin intermediate shoulder surface, a pin intermediate sealing surface, and a pin annular portion. The box includes a recess corresponding to the nose, a tapered inner female thread, a tapered outer female thread, a box inner sealing surface, a box intermediate shoulder surface, a box intermediate sealing surface, and a box annular portion. The threaded connection satisfies expressions (1) and (2), provided below. &#x3b1;is a taper slope of the inner male thread, and &#x3b1;is a taper slope of the outer male thread.  In expression (2), Lis a distance between the tip of the pin and the pin intermediate shoulder surface as measured along the pipe-axis direction when the pin and box have not been made up, and Lis a distance between the box intermediate shoulder surface and the tip of the box as measured along the pipe-axis direction when the pin and box have not been made up.

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 () connects pipes for oil wells (). The threaded connection () includes two pins () and a tubular coupling. Each of the pins () is provided on an end of the pipe for oil wells () and is in continuity with the pipe body (), which has a wall thickness not smaller than 12 mm. The coupling () includes two boxes () and a recess portion (). The box () is provided on both ends of the coupling (). The recess portion () has a length not smaller than 10 mm. The threaded connection () has a connection efficiency smaller than 1. When the wall thickness of the pipe body () is expressed as t, the wall thickness and length of the recess portion () are expressed as tand 2&#xd7;L, respectively, and the length of each of the boxes () is expressed as L, and if the following expressions (1) and (2) define T and L, then, T and L satisfy the following expression (3): 

Threaded connection for oil well

A pin includes, in order from a free end thereof, a shoulder surface, a first sealing surface, a first male threaded portion, a second sealing surface, and a second male threaded portion. A box includes a shoulder surface, a first sealing surface, a first female threaded portion, a second sealing surface, and a second female threaded portion. The flank angles of load flanks of the first male threaded portion and the first female threaded portion are each less than 0 degrees. The first male threaded portion is composed of, in order from near the second sealing surface, an incomplete thread section and a complete thread section. The incomplete thread section has a length of at least three times the thread pitch thereof and has a thread height lower than the thread height of the complete thread section. The incomplete thread section is provided with clearances between crests and roots.

Threaded joint for steel pipe

A threaded joint is constructed of a pin and a box. The pin includes, in order from an end thereof, a shoulder surface, a nose portion, a first sealing surface, a first male threaded portion, an annular portion, a second sealing surface, and a second male threaded portion. The box includes a shoulder surface, a recessed portion, a first sealing surface, a first female threaded portion, an annular portion, a second sealing surface, and a second female threaded portion. In the threaded joint, in a fastened state, the shoulder surfaces are in contact with each other, the first sealing surfaces are in contact with each other, the second sealing surfaces are in contact with each other, a clearance is provided between the nose portion and the recessed portion, a clearance is provided between the annular portions.

Threaded joint for steel pipes

A threaded joint for steel pipe is provided that ensures good sealing performance and reduces crevice corrosion. A threaded joint includes a pin () and a box (). The pin () includes a first shoulder surface (), a first male thread (), a second shoulder surface (), and a second male thread (). The box () includes a first shoulder surface (), a first female thread (), a second shoulder surface (), and a second female thread (). Supposing that the distance between the shoulder surfaces of the pin () is represented as Land the distance between the shoulder surfaces of the box () is represented as L, and the interference &#x3b4;is defined by Equation (1) given below, then, the threaded joint is constructed such that Equations (2) and (3) given below are satisfied. In Equations (2) and (3), P is the thread pitch of the first male thread (), &#x394;and &#x394;are the lower and upper limits, respectively, for the difference between the numbers of tightening rotations, and &#x3bb; is the elongation of the portion of the pin () located closer to the tip than the second shoulder surface () is.[Formula 1]&#x3b4;&#x2003;&#x2003;(1)+&#x3bb;&#x2264;&#x3b4;+&#x3bb;&#x2003;&#x2003;(2)&#x394;=&#x2212; 9/100, &#x394;= 3/100&#x2003;&#x2003;(3)

The load flanks in the male threaded portion of the pin and the load flanks in the female threaded portion of the box have a flank angle of less than 0 degrees. The female threaded portion is divided into, in order from near the seal surface, an incomplete thread section and a complete thread section. In the female threaded portion, over the entire area including the two thread sections, roots collectively define a single tapered periphery. The incomplete thread section has a length of at least three times the thread pitch and has a thread height lower than a thread height of the complete thread section. The shoulder surfaces are in contact with each other, the seal surfaces are in contact with each other, and in the incomplete thread section, clearances are provided between the roots of the male threaded portion and the crests of the female threaded portion.

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Tokyo, Japan

Keita Inose