Flue Duct Expansion Joint

Critical Flexibility for High-Temperature Gas Conveyance Systems

A Flue Duct Expansion Joint is a specialized flexible connector engineered to absorb movement,isolate vibration,and compensate for misalignment within industrial flue,exhaust,and air handling ductwork.These joints are vital for maintaining the structural integrity of duct systems subjected to extreme thermal cycles,aggressive chemical environments,and dynamic mechanical forces.

Core Design Challenges&Solutions

Flue duct joints operate in some of the most punishing conditions,requiring designs that address:

Extreme Temperatures:Withstanding continuous operation from ambient to over 1800°F(1000°C)in applications like boiler uptakes and incinerator exhausts.

Corrosive&Abrasive Media:Resisting acidic condensates(acid dew point corrosion),abrasive particulate(fly ash,catalyst dust),and chemical byproducts.

Complex Multi-Directional Movement:Accommodating large thermal growth(axial,lateral,angular)of large,often poorly restrained duct sections,as well as equipment vibration and seismic activity.

High Positive&Negative Pressure:Maintaining a gas-tight seal under both pressurized and induced-draft(vacuum)conditions.

Primary Types&Material Configurations

1.Non-Metallic(Fabric/Fiber)Joints

Construction:Multiple plies of high-temperature fabrics(fiberglass,silica,ceramic)coated with elastomers(silicone,EPDM,PTFE)and often include internal insulation layers.

Benefits:Excellent for absorbing large multi-directional movements,vibration damping,and thermal insulation.Cost-effective for large rectangular ducts.

Typical Use:Baghouses,SCR/SNC systems,lower-temperature flue gas desulfurization(FGD)ducts,general HVAC exhaust.

2.Metallic Bellows Joints

Construction:Manufactured from high-grade stainless steel(321,310,316L),high-nickel alloys(Inconel®625),or specialty steels,often with multi-ply construction.

Benefits:Superior strength for high pressure/vacuum,extreme temperature capability,and excellent resistance to abrasion.

Typical Use:Main boiler exhaust uptakes,gas turbine exhaust,catalytic cracker flue ducts,high-pressure combustion air ducts.

3.Hybrid(Composite)Joints

Construction:Combine a metallic flanged frame with a non-metallic flexible membrane,sometimes incorporating a metallic foil or mesh liner for added temperature/abrasion resistance.

Benefits:Balances movement capability,temperature resistance,and cost.The metal frame handles structural loads while the membrane flexes.

Typical Use:A wide range of applications where temperatures exceed standard fabric limits but full metallic joints are not required.