| Single
Bellows |
• |
Dimension |
: |
300
NB x 150 mm. long |
• |
Axial
Movement |
: |
+
35 mm. |
|
|
This
expansion joint is simply a bellows element
with end connections. Regardless of accessories,
such as liners and covers, it will deflect
in any direction or plane that the bellows
will. It is the least expensive type, but
requires that the piping be controlled as
to the direction of the movements required
of the unit.
The expansion joint should not be expected
to control the movement of the pipe. If
the piping analysis shows that the expansion
joint must accept axial compression, then
the piping must be guided and constrained
so that only that movement will occur.
This expansion joint will not resist any
deflections with any force other than the
resistance of the bellows, which is a function
of the spring rate times the deflection
amount. It is incapable of resisting the
pressure thrust along its axis, which is
the product of the pressure times the effective,
or cross sectional, area of the bellows.
Large diameter units, even with low pressures,
can generate very large axial pressure thrust
forces, which must be reacted by main and
directional anchors. Otherwise the expansion
joint will extend with disastrous results. |
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