Flue Duct Expansion Joints

Flue Duct expansion joints are used in a variety of industries and applications, including power generating facilities, pulp and paper mills, steel mills and petro-chemical plants. Expansion joints are used primarily to relieve stresses in piping and ducting systems caused by thermal expansion and contraction.

At Zepco, we have over 70 years of combined experience that goes into the design, fabrication and installation of expansion joints in ducting and piping applications. A comprehensive knowledge of operating conditions goes into the design and construction as well as the installation of expansion joints. While resiliency, durability and maintenance are always of paramount concern, understanding the operating conditions, temperatures and pressures in the ducting system, as well the external environmental conditions, is achieved only through years of hands-on experience.

Flue gas is often treated with a series of mechanical and chemical systems to remove pollutants. Electrostatic precipitators, fabric filters (baghouse) are used to remove particulate matter, while flue-gas desulfurization captures sulfur dioxide. Catalytic converters (SCR and NSCR systems) neutralize other selective and non-selective gases typically found as byproducts in the burning of fossil fuels.

Non-metallic flue duct expansion joint designs typically include the use high temperature/high strength fabrics, elastomers, thermal plastics and metal fabrications. Well-designed flue duct expansion joint systems provide flexible connectors that absorb thermal growth and shock, while minimizing the impact of vibration. As specialists in the expansion joint market, Zepco has designed and installed expansion joints in both typical and non-typical applications throughout North America.

Our flue duct expansion joints are designed typically to handle low pressure applications and gas temperatures up to 2000°F. They are available in various configurations and can be manufactured with almost no size restrictions.

  • Fabric expansion joints can move in multiple directions (axially, laterally or rotationally) on X, Y and Z-axes. Metal moves one way only, laterally or axially. Additionally, fabric expansion joints are superior in absorbing twisting movements caused by differential heating.
  • Non-metallic expansion joints are more effective in isolating vibration and mitigating noise.
  • Corrosion-resistance is greatly enhanced with fabric construction.
  • Non-metallic expansion joints are significantly less expensive to fabricate ship, assemble and install. Just as important, repair and replacement are less costly.

For more information about the benefits of non-metallic expansion joints, please contact Zepco with any questions or comments.

Materials of construction

In the designing of flue duct expansion joints, the materials of construction are important to maximize the life of the joint. A composite joint, just because it has a higher temperature rating, designed for 1000*F operating condition will not give a longer life in service operating at 300*F in a corrosive flue gas application than a molded rubber joint. The materials of construction used in expansion joints need to be designed for the operating conditions.

Molded rubber joints using EPDM rubber are designed typically for gas temperatures from ambient to 300*F. Typical applications would include Force Draft Fans and flue gases below 300*F.

Viton/FKM rubber joints are used in flue gas application from ambient air temperatures to 400*F with excursion temperatures that could reach 750*F.

Teflon-based expansion joints can used without insulation for gas temperatures up to 500*F. When used in composite joints with specially designed pillows and layers of insulation they can be used for flue gases reaching 1200*F.

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