STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

622 Drilling and Well Completions
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Figure 4-92. Upper kelly cock [13].
Square-Forged Kellys
In square-forged kellys, the decarburized zone has been removed from the
corners of the fillet between the drive section and the upset to prevent fatigue
cracks. Hexagonal kellys have machined surfaces and are generally free of
decarburized zone in the drive section.
The life of the drive section as related to the fit with kelly drive bushings is
generally greater when the square drive section is used. However, the use of
adjustable drive bushings (adjustable bushings with wear) can drastically increase
the life of the square drive section.
The important parts of the kelly that should be examined for wear are:
the corners of the drive section (for surface wear)
the junctions between the upsets and the drive section (for cracks)
the straightness of the kelly.
Rotary Table
Rotary Table and Bushings
The rotary table (Figure 4-95) provides the rotary movement to the kelly. The
master bushing of the rotary table encases the kelly bushing or pipe slips, as