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removable bushings. Primary flexing takes place at each of the two bearing rings in
the upper and lower sections (fig. 6.22). The two pieces in the middle, the seal
assembly, are composed of the same flexing material and mainly seal between the
internal mud pressure and the external ambient pressure. The flex material is
laminated layers of steel and rubber. The action is more like a sliding, compressive
loading than the pivotal loading on the spherical surface of the single ball joint.
Hydraulic Hydraulic
pressure pressure
applied to applied to
upper lower
segment of segment of
ball- socket ball- socket
interface interface
compensat compensate
es for s for
compressio tension
n loads on loads
ball joint acting on
assembly ball joint
assembly
C-1 PRESSURE C-2 PRESSURE
Figure 6.20 – Pressure balance system —Type II single-ball flex joint
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