STANDARD H-SERIES
The H-SERIES
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.
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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 H-SERIES weldneck/upset design is a thoughtful, engineered approach to the
design of this important transition.
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Engineered MaterialsThe 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.
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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. |
Modern equipment and patented proprietary processes
are also integral parts of the H-SERIES 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 H-SERIES® Tuff-Weld®
quench and temper heat-treating process. |
Geometry
The H-SERIES 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).
SummaryThe H-SERIES 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. |
