The universal expansion joint consists of
two bellows separated by a pipe section
or spool. The primary purpose of this arrangement
is to have a unit which will accept large
amounts of lateral deflection. The amount
of lateral deflection they can accept is
a function of the amount of angulation each
bellows can absorb and the distance between
the bellows. For a given bellows element,
the amount of lateral deflection capability
can be increased or decreased by simply
changing the length of the center spool.
In this catalog three standard overall lengths
are given with their lateral movement capability.
If the piping problem requires greater capability,
then the overall length can be increased
to suit.
Since deflections are usually the result
of piping thermal expansion, and universal
expansion joints are usually long, our units
are designed so that the thermal expansion
of the entire unit's length is accepted
as compression by the two bellows elements.
In this way, the overall length of the unit
does not change when the piping is heated.
The standard units in this catalog have
all been designed to accept the thermal
expansion of their length when the temperature
is up to the design temperature shown.
Universal types can be supplied with or
without tie rods. Tie rods connect the ends
of the unit to each other and restrain the
pressure thrust load. This unit is normally
not expected to accept any externally applied
axial deflections. The thermal expansion
of the distance between the tie rods ---within
the expansion joint--- will be handled by
the bellows element, as described above.
The tie rods usually come in sets of two
or more, equally distributed around the
circumference of the expansion joint. When
only two are provided, 180 degrees apart,
the expansion joint is free to bend, or
deflect angularly, as well as laterally.
With three or more tie rods, since rods
are loaded equally by the pressure thrust,
only lateral deflections are possible without
significant forces being applied by the
adjacent piping. Without tie rods, the universal
expansion joint will accept all of the deflections
that a single type will, and the pipe guiding
and anchoring needs discussed for the single
type above also apply.
Many times the universal expansion joints
will be attached directly to pipe elbows
as shown on page 12. As discussed in more
detail in the Applications Section, this
arrangement, because of the large lateral
deflection capability, accepts the thermal
expansion of relatively long runs of heated
pipe. So that the distance between the elbows
does not change due to thermal expansion,
the tie rods can be connected to the elbows
themselves. This catalog offers this type
of arrangement as one of the standards,
and can be seen on each of the Universal
expansion joint pages, along with their
dimensions and performance characteristics.
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