Pressure Piping Expansion Joints

Pressure Balanced Expansion Joints
Elbow or Tee, Single-Flex Series "PBES" and Universal Series "PBEU"

Thorburn's Series PBES Sing-Flex and PBEU Universal are custom designed pressure balanced elbow or tee expansion joint systems. These joints are specifically designed to overcome the reaction load, due to internal pressure acting against turbine casings, pumps, structures and other equipment. They are used at a change in direction of piping where a main anchor cannot be installed, to absorb axial and lateral motion while restraining pressure thrust.

Thorburn's pressure balanced expansion joint design uses flow and balancing bellows that are inter-connected by the use of tie rods. The balancing bellows is subjected to the same line pressure as the flow bellows. As the flow bellows compresses, the tie rods make the balancing bellows extend an equal amount. Since there is no change in the volume of the system, the pressure forces remain in balance. It should be noted that when the flow bellows deflect laterally, there is no volume change and therefore the balancing bellows need only contain the proper number of convolutions required to absorb the axial movements of the system. The axial force, however, is the total of the force required to move the line bellows and balancing bellows.


How does it work? The balancing bellows is subjected to the same line pressure as the flow bellows. As the flow bellows compresses, the tie rods make the balancing bellows extend an equal amount. Volume remains unchanged and pressure forces remain balanced.

A schematic illustration showing the principle behind Thorburn pressure balance flexible piping technology.


A= FLOW BELLOWS
B= BALANCING BELLOWS
C= TEE OR ELBOW CONNECTOR
D= TIE RODS
E= MEAN DIAMETER OF CORRUGATIONS
F= PRESSURE THRUST OF THE LINE
G=REACTION PRESSURE THRUST ON THE
    BALANCING END


Applications

Absorbs axial and lateral movements while
still restraining pressure thrust
Eliminates main anchors
Minimum Guiding required



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Boiler Feed Pump Turbine Exhaust
Expansion Joint "PBEU"




SERIES "PBES"



Thorburn's pressure balanced expansion joints are used where there is a change in the direction of the pipe line. The most common applications for Thorburn's pressure balanced elbow is adjacent to a piece of equipment such as a turbine, pump or valve where allowable nozzle loads necessitate the elimination of pressure thrust.