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Pressure Balanced
This expansion joint is a unique design that not only restrains the pressure
thrust, but also balances this thrust force so that main anchoring of the pipe
and adjacent equipment is not necessary. The result is that the forces and
moments on the nozzle connections of delicate equipment such as pumps and
turbines are kept below the allowable loads. This expansion joint is used
in cases where a Tied Expansion Joint is required to accept axial movement
while restraining pressure thrust. The Pressure Balanced Expansion Joint
can be designed as a single, or a universal if large amounts of lateral
movement are required. The Pressure Balanced Expansion Joint is normally
used at a change of direction in the piping, and the elbow is mounted
between the line or flow bellows and the balancing bellows. The line bellows
and balancing bellows have the same cross-sectional area and are connected
by tie rods that restrain the pressure thrust. As the line bellows compresses,
the tie rods force the balancing bellows to extend an equal amount and the
elbow between the two is free to move axially with only the resistance of
the spring rates of the bellows. The axial spring rate of the expansion
joint is the sum of the spring rate of the line bellows and the balancing
bellows. However, the lateral deflection and spring force of the expansion
joint is only a function of the line bellows, whether it is a single or
universal, and the balancing bellows is not subject to the lateral deflection.
Return to EXPANSION JOINTS
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