Buttress-threaded tubular connection
AssigneesNKK Corporation, Marubeni Tubulars, Inc.
InventorsEdward O. Banker, Teruo Suzuki, Erich F. Klementich, Jeffrey K. Bouche
Life of this patent
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Abstract
The present invention pertains to an improvement in buttress-threaded tubular connections. In particular, the connection is improved by controlling the tubular member thread pitch diameter tolerance to .+-.0.0015 inch, to provide a thread bearing contact pressure which is relatively constant over the entire length of the connection. In addition, the improved connection provides a reduction in hoop stress of about 20% over known buttress-threaded tubing connections. The present invention typically includes the use of variable make-up in combination with the control of the tubular member thread pitch diameter tolerance.
Claims22
A tubular and coupling connection comprising a tubular member having a cylindrical outer surface with a tapered buttress threaded section disposed adjacent to and through the end of said outer surface, wherein said threaded section leading edge is located at the end of said tubular member and wherein said threaded section includes fully formed perfect threads and vanishing imperfect threads which vanish at the trailing edge of said threaded section, and a coupling member corresponding with said threaded tubular member and having a complementary threaded section on the internal surface thereof, said complementary threaded section including fully formed perfect threads throughout the length thereof and at least as long as the total length of said perfect and imperfect threads on said tubular member, said threaded section and complementary threaded section having threads forming crests and roots, wherein the improvement comprises:
- said threads of said tubular member and said coupling member each having a pitch diameter tolerance of .+-.0.0015 inch;
- said threads forming clearance voids between mating crests and roots ranging from slightly greater than 0.000 inches to less than 0.0035 inches;
- whereby a relatively constant thread bearing contact pressure is provided over the entire length of said connection.
A method of constructing a tubular and coupling connection,
- comprising a tubular member having a cylindrical outer surface with a tapered buttress threaded section disposed adjacent to and through the end of said outer surface, wherein said threaded section leading edge is located at the end of said tubular member and wherein said threaded section includes a length of fully formed perfect threads beginning at said leading edge and then a length of vanishing imperfect threads which vanish at the trailing edge of said threaded section, and a coupling member corresponding with said threaded tubular member and having a complementary threaded section on the internal surface thereof, said complementary threaded section including fully formed perfect threads throughout the length thereof and at least as long as the total of the lengths of said perfect and imperfect threads on said tubular member, said threaded section and complementary threaded section having threads forming crests and roots, said method including the steps of:
- machining the threads of said tubular member and said coupling member, each to have a pitch diameter tolerance of .+-.0.0015;
- forming clearance voids between mating crests and roots ranging from slightly greater than 0.000 inches to less than 0.0035 inches;
- and
- providing a relatively constant thread bearing contact pressure over the entire length of said connection.
A tubular and coupling connection comprising:
- a tubular member having a cylindrical outer surface with an external tapered buttress threaded section disposed adjacent to and through the end of said outer surface;
- said external threaded section having fully formed threads beginning at a leading edge located at the end of said tubular member and vanishing threads ending at a trailing edge of said external threaded section;
- said external threaded section including external threads with crests and roots;
- a coupling member having a length and a vertical center line, said coupling member corresponding with said tubular member and having a an inner surface with an internal threaded section complimentary to said external threaded section;
- said internal threaded section having fully formed threads beginning at a leading edge located at the end of said coupling member and extending along the length thereof with said length being at least as long as the length between said leading edge and said trailing edge of said external threaded section;
- said threads of said tubular member and said coupling member each having a pitch diameter tolerance of .+-.0.0015 inch;
- said internal threaded section including internal threads with crests and roots;
- said internal and external threads having stab flanks in bearing relationship and load flanks in bearing relationship;
- said stab flanks having a larger flank angle than said load flanks;
- said crests and roots forming clearance voids between mating crests and roots ranging from slightly greater than 0.000 inches to less than 0.0035 inches;
- and
- said bearing relationships being relatively constant between mating external and internal threads.
Dependencies are inferred from the claim text.