Industrial off-gas handling is one of the most demanding jobs in composites. Ductwork carrying corrosive, high-temperature process gas has to survive sulfur-bearing gases, acidic condensate, abrasive solids, vacuum and constant thermal cycling — and still run for decades. Get the material and structural design right and FRP ductwork far outlasts metal; get it wrong and it fails early.
A real-world engineering evaluation
Crimar’s engineering team was recently engaged to evaluate replacement options for a large FRP duct system in a demanding metallurgical process. The existing duct had run for decades under severe service — itself a testament to well-designed composites — and the facility wanted to apply modern materials and methods to support future reliability.
The service conditions
- Elevated operating temperatures approaching 80 °C (176 °F)
- Sulfur dioxide (SO₂)-rich process gas
- Acidic condensate exposure
- Continuous vacuum service
- Heavy solids accumulation and loading
- Extreme seasonal temperature swings, wind and maintenance loads
Evaluating material options
Conventional FRP (vinyl-ester)
Vinyl-ester resin reinforced with corrosion-resistant glass remains the industry standard for flue-gas and chemical-process duct. Properly designed FRP ductwork offers excellent corrosion resistance, proven long-term performance, cost-effective lifecycle economics, and ease of fabrication and installation.
Carbon-fiber reinforcement
For select high-temperature applications, carbon-fiber reinforcement can add a higher stiffness-to-weight ratio, improved dimensional stability, lower thermal expansion, and an optimized support and expansion-system design. Whether the added investment delivers a meaningful operational advantage depends on the application — it warrants a detailed engineering review, not a default specification.
Good duct design is more than wall thickness
In corrosive gas service, the structural calculation is only part of the picture. Engineers also have to evaluate resin selection, corrosion-barrier construction, surface veil materials, reinforcement architecture, thermal expansion effects, chemical compatibility and long-term aging behavior. A system that performs well at moderate temperature can behave very differently as temperatures rise.
Applications
Our FRP ductwork and piping and scrubbers and towers serve non-ferrous metal smelting, sulfuric acid plants, chemical processing, air-pollution control, wet gas scrubbing and hydrometallurgical facilities — closely overlapping our work in chemical, oil & gas and mining and mineral processing.
Partner with experienced FRP engineers
Whether your operation needs large-diameter ductwork, scrubbers, stacks, tanks or custom process equipment, the right material system and structural design deliver long service life in corrosive environments. With FRP fabrication in China and Mexico — backed by US-based engineering and decades of composite experience — Crimar supports customers worldwide.