fabric expansion joints

Fabric flue duct expansion joints serve as a non-metallic solution for relieving stress in piping and ducting systems. With their multi-plane movement capabilities and efficient vibration absorption, fabric expansion joints are suitable for a range of ambient, hot air, and flue gas services.

Fabric Expansion Joints for High Temp Flue Ducts

ThermaFlex Fabric Expansion Joints are non-metallic flue duct expansion joints that provide stress relief for piping and ducting systems by absorbing thermal growth and shock, isolating mechanical vibration, and allowing for misalignment.  ThermaFlex expansion joints are precision engineered specifically for your application.

ThermaFlex Flue duct expansion joints are custom engineered to handle low pressure (±3 psig) applications with temperatures ranging from -100°F to more than 2000°F.

Service Features of Fabric Expansion Joints

  • Absorb axial, transverse and torsional movements
  • Corrosion and chemical resistance
  • Negligible spring rates and loads
  • Easily repairable and installable
  • High cycle life
  • Unique application solutions
  • Vibration dampening and sound attenuation
  • More movement in shorter face-to-face
  • Less force to flex than metal expansion joints
  • Excellent corrosion and chemical resistance
  • Temperature capability range (-110°F to more than 2,000°F)
  • Lower shipping and installation costs
  • Variety of flexible belt materials available:
    • Single-layer and composite belts
    • Elastomers have excellent abrasion resistance
    • Custom designed for each specific application

Design Considerations

  • Media: Internal and External Environment
  • Temperature: Constant operating and maximum excursion
  • Pressure: Normal positive or negative
  • Movements: Axial and lateral, simultaneously or independently
  • Installation: Existing equipment and duct flanges
  • Assembly: Factory-assembled or field-spliced


Baffles are usually not necessary with elastomeric expansion joints due to the tube resistance to most abrasive particular matter. However, baffles must be used with fabric composite joints to protect the inner surface form particulates in the gas stream. UIP International, Inc. can supply baffles fabricated from carbon steel, stainless steel, or other materials as required.

Retaining Rings

Standard construction calls for 2″ wide, 3/8″ thick bars with slotted holes for easy installation. Material of construction can be carbon steel or stainless steel.


  • U-type
  • Belt type
  • Square
  • Rectangular or round
  • No size restriction
  • Choice of FF dimension, depending on movements
  • Associated Metal Work: Backup bars, frames, flanges and baffles

Design Advantages of Non-Metallic Ducting Expansion Joints

  • Large movement capability / Multi-plane movements
  • Corrosion / Chemical Resistance
  • Range of Design Temperature Capability (-110° F -+2000° F)
  • Negligible Spring Rates / Loads
  • Vibration Dampening & Sound Attenuation
  • Lower Overall Costs (Design, Installation, Replacement & Repair)
  • Easy to Install / Repair
  • High Cycle Life
  • Unique Application Solutions

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