• Weldneck and Upset Design

    Description

     Grant Prideco Upset Design  

    • The Grant Prideco weldneck/upset design incorporates a counterbored weldneck, an extended internal upset length, a shallow internal taper angle, and generous radii to produce the optimum stress reducing geometry. 
    • A critical section of a joint of drill pipe is the transition from the pipe body to the tool joint. This section consists of the weld that joins the pipe and tool joint and the transition from the thin cross section of the pipe to the thick cross section of the tool joint. The challenge to the drill pipe designer is to ensure that: 1) the weld is stronger than the pipe body and 2) the smoothest transition between the pipe body and the tool joint is as strong as possible. 
    • When drill pipe rotates in a bent condition, tensile and compressive stresses can cause fatigue cracks that may ultimately result in drill pipe washouts. Stresses concentrate where geometries change rapidly. The shorter or more irregular the transition, the higher the stress concentration. Alternatively, the smoother or longer the transition, the lower the stress. 
    • The weldneck/upset design is a thoughtful, engineered approach to the design of this important transition. 

    Engineered Materials
    The design starts with engineered materials. Grant Prideco incorporates specially designed proprietary steels for both the drill pipe tube and the tool joint. The chemistries of the tube and tool joint materials are matched to ensure good weld compatibility and weld strength. Stringent cleanliness requirements for both materials enhance fracture toughness. The increased hardenability of the materials consistently produces more uniform mechanical properties throughout the entire cross section. This ensures adequate strength in the weld zone and the critical sections of the connection.

    Generic Design
    The thick weldneck, required for adequate weld strength, and the short internal upset of a standard industry design concentrates stress in the adjacent pipe body.

    Processing
    Modern equipment and patented proprietary processes are also integral parts of the Grant Prideco weldneck/upset region. Grant Prideco's modern austenitizing and tempering furnaces provide a controlled quench and temper heat-treating process for our tubes. The tubes undergo a full- length inspection that checks for defects. Tool joints are 1) precision contoured, 2) heat-treated by a controlled atmosphere quench and temper process, and 3) threaded on Computer Numerically Controlled (CNC) machine tools. Then the tool joints and tubes are joined by a reliable friction or inertia weld process. After welding, the weld's heat-affected zone receives the Grant Prideco® Tuff-Weld® quench and temper heat-treating process.

    Geometry
    The Grant Prideco weldneck/upset incorporates a geometry that minimizes stress concentrations. The assembly is configured to optimize the transition from the cross section of the pipe to the tool joint. The length of the internal upset is extended, producing a shallow fadeaway angle that blends into the pipe body's inside diameter (ID) with a generous radius. The surface finish of the assembly adjacent to the weld line is improved by grinding on both the inside diameter (ID) and outside diameter (OD). 

    Summary
    The Grant Prideco weldneck/upset design is a comprehensive solution that addresses all the parameters affecting the drill pipe's fatigue strength. Engineered materials and modern processing techniques ensure a tensile strength greater than the pipe body and limit detrimental stress concentration. Precision machining and grinding provide a surface finish that is free of stress risers. State-of-the-art electromagnetic and ultrasonic inspections ensure that inclusions and defects are not present.

    The resulting design has lower stress and greater fatigue strength than that obtained with the generic design.

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