Choosing chemical-resistant fabric expansion joints for flue gas applications requires a systematic engineering evaluation of the operating conditions, materials performance, structural design, and installation implications. Properly specified fabric joints accommodate thermal movements, corrosive atmospheres, low pressures, and velocity-related erosion while minimising stress on adjacent ductwork. The following approach provides a technically robust framework tailored to engineers, EPCs, and maintenance professionals.

Fabric joints supplied by DEKOMTE are engineered for a wide range of gaseous media—including exhaust gases, flue gas streams with acidic condensates, and abrasive particulates—via modular, multilayer construction that balances flexibility with durability.

1. Establish Detailed Operating Conditions

Before material or design selection, it is essential to compile the full operating envelope:

• Temperature profile
  Define continuous operating temperature, start-up and shutdown spikes, and transient excursions. Material thermal limits directly affect service life.

• Gas composition
  Quantify corrosive species such as SOx, NOx, chlorides, moisture, and acidic condensates. Corrosion attack mechanisms influence material selection and sealing strategies.

• System pressure and vacuum levels
  Confirm that internal pressures, including dynamic pressure changes, are within the allowable range for the selected joint. Fabric joints are typically applied in low-pressure flue gas ducts but must be verified.

• Movement requirements
  Quantitatively establish axial, lateral, and angular movements induced by thermal expansion and structural dynamics (in mm and degrees). External standards and references such as the Expansion Joint Manufacturers Association (EJMA) provide design guidelines for acceptable movement criteria.

• Gas velocity and erosion factors
  High velocities or particulate loading accelerate wear; these influence the need for internal sleeves or erosion-resistant layers.

These parameters feed directly into material compatibility, mechanical design, and serviceability planning.

2. Material Selection: Chemical and Thermal Resistance

Fabric expansion joints are composite assemblies with each layer contributing specific mechanical or environmental performance. Component materials should be selected based on thermal limits, chemical compatibility, and mechanical resilience.

Primary Fabric and Coating Materials

• PTFE-coated fabrics
  Polytetrafluoroethylene (PTFE) provides exceptional chemical resistance, low gas permeability, and thermal stability for corrosive flue gas streams. This makes PTFE coatings a leading choice for acidic environments.

• Fiberglass base fabrics
  Glass fibre substrates serve as the structural backbone of many fabric joints due to their high heat tolerance and dimensional stability under load.

• Silicone and elastomeric coatings
  These coatings enhance weatherability and moderate chemical resistance, though their upper temperature limits are lower than PTFE.

• Ceramic and high-silica fabrics
  Used in zones with extreme thermal demands; these materials deliver superior thermal and chemical stability when combined with appropriate coatings.

DEKOMTE’s Fabric Expansion Joints page provides an overview of the multi-layer constructions available and the variety of materials deployed for flue gas and exhaust service.

3. Joint Construction and Design Strategies

Material selection must be paired with the correct joint architecture to achieve performance and longevity.

Single-Layer vs Multi-Layer Assemblies

• Single-layer joints offer cost efficiency but limited chemical and thermal capacity.

• Multi-layer assemblies integrate gas impermeable barriers, insulating layers, and reinforcement fabrics to achieve a balance of chemical resistance, thermal control, and mechanical robustness. Such multi-layer designs are typical in flue gas applications.

Internal Sleeves and Reinforcements

Internal sleeves protect the structural layers from direct impingement by high-velocity gas and particulate flow. Reinforcement meshes or ribbing prevent distortion under pressure and movement.

Frames, Seals, and Interfaces

The joint must interface with flanges or duct frames whose geometry and sealing strategy minimise leakage and mechanical stress at the boundary. Selection of gasketing materials and attachment methods affects long-term sealing performance.

DEKOMTE’s product information details the configurable designs and options for fabric joint constructions across a range of movement and environmental conditions.

4. Movement and Mechanical Load Assessment

Fabric joints are chosen for their ability to absorb complex movement with low reaction forces imposed on piping. For effective specification:

• Confirm that the joint can accommodate expected axial, lateral, and angular movements without exceeding fabric strain limits.

• Evaluate cyclic loading and fatigue behaviour under typical thermal cycling.

Thermomechanical modelling and consultation with manufacturers can help ensure that movement demands are matched to joint geometry and fabric grades.

5. Installation, Environment, and Maintenance Considerations

Environmental exposure and installation constraints influence design choices:

• External protection for UV and weather exposure may be necessary for outdoor ducts to prevent degradation.

• Select flange or belt type attachment systems that simplify field installation and future replacement.

• Ensure access for inspection and maintenance, as fabric joints will experience wear over time and may require scheduled replacement.

6. Manufacturer Expertise and Standards

Work with reputable suppliers who provide:

• Custom design support for specific operating envelopes.

• Engineering performance data for temperature, chemical compatibility, and durability.

• Integration with inspection, repair, and maintenance services, such as DEKOMTE’s Technologie de réparation des points d'accès.

Also reference industry design standards and best practices to validate joint selection and design validation.

Summary Checklist

Application Data
Define temperature, pressure, and gas chemistry.
Quantify mechanical movements under operating conditions.

Sélection des matériaux
Choose base fabric and chemical barrier (e.g., PTFE) based on resistance requirements.

Design Details
Specify multi-layer construction tailored to movement and chemical conditions.
Include protective internal sleeves and properly engineered frames.

Implementation
Ensure correct attachment method and accessibility.
Plan inspection intervals and maintenance access.