A system (150) and method of tensioning a bolt (44) across a flange
assembly (42). A tensioning apparatus (40) includes the bolt and an
unthreaded nut (48) connected to the shank member by an interference fit.
The interference fit may be selectively relaxed by applying a fluid
pressure to a groove (54) between the nut and the bolt. A tensioner (58)
is energized by a pressure to pre-load the bolt by pulling on the bolt
while pushing on the nut while the interference fit is sufficiently
relaxed to allow relative movement between the nut and the bolt. The
tensioner is sized to achieve the required pre-load in the bolt at the
same working fluid pressure that is necessary to relax the interference
fit on the stretched bolt, thus permitting a single pressure source (148)
to be used for both functions. Once the pre-load is established, the
interference fit is reestablished by releasing pressure to the nut to
secure the nut in position for maintaining the closure force across the
flange assembly after the tensioner is removed. Because the nut does not
need to rotate, the pre-load may be applied directly through the nut
without the use of a bridge, thereby eliminating the need for
overstressing of the bolt to accommodate seating of the nut once the
tensioner is relaxed.