Technical Terms

  • Axial Movement: Axial compression and axial extension are referred as axial movement.
  • Axial Compression: Dimensional change in Bellow Expansion in which bellow length compresses due to operational factors affecting on it.
  • Axial Extension: Dimensional change in Bellow Expansion in which bellow length increases due to operational factors affecting on it.
  • Lateral Movement: Displacement of two ends of Bellow Expansion in perpendicular direction to the direction of flow is referred as lateral movement. Such movement can be in one to two planes.
  • Angular movement: When Bellow Expansion bends into arc form from its straight flow direction it is referred as angular movement.
  • Control Rods: Control Rods also referred as tie rods or limit rods is arrangement of solid rods or pipes fixation over Bellow Expansion. This arrangement varies according to its purpose. Control rods are used for
    1. Limiting movement of Bellow Expansion to its design.
    2. To absorb thrust force applied of Bellow Expansion.
    3. To avoid buckling of Bellow Expansion.
    4. It may also be used to shipping purpose only. If so such rods are removed after installation.
    5. For large diameter Bellow Expansion control rods are attached for adjusting length of Bellow Expansion during installation. After proper installation of Bellows this rods are removed.
  • Spool Piece: Also referred as distance piece. A piece of pipe connected with bellows at its both ends. This arrangement is seen in universal bellow expansion and double bellow expansion. In universal bellows this pipe deflects to absorb lateral displacement, whereas in double bellows spool piece remains steady attached with anchor support.
  • Corrugations: The spiral of a spring type structure in Bellow is called corrugation.
  • Inner Sleeve: If medium of flow through Bellow contains particles, liquid material or any such material which can chock gap between corrugations than in such case Bellow is provide with inner sleeve. If temperature inside Bellow is high, than to avoid heating of corrugations inner sleeve is provided.
  • End Connections:Two connecting parts at the end of Bellow matched to fix with pipeline fixture. These connections can be pipe ends or flanges. Connecting ends are generally specified by clients or are advised by Bellow manufacturer.
  • Lugs: Support plates for control rods on end connecting pipe of flanges are referred as lugs.
  • Shipping Bars: Yellow painted bars welded for maintaining length of Bellow during transit.
  • Bellow: Corrugated part of an Expansion Joint meant for flexibility.
  • Expansion Joint: Device or instrument for compensating dimensional changes in various directions in pipeline due to pressure or thermal effect.
  • Thermal Expansion: Increase in length of pipe due to temperature.
  • Thermal Contraction: Decrease in length of pipe due to temperature.
  • Braiding: Layer of group of wires wounded on conduit.
  • Gimbal Ring: In gimbal bellow a center ring or square attached with pins as to give Bellows an angular movement is referred as gimbal ring.
  • Hinge Plates: Plates connected with pins at one end and lugs at other end attached with end connections of Bellow.
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