Duct Expansion Joints

Flexicraft offers a full offering of quality non-metallic "fabric" belt type, and also integrally flanged fully molded type, duct expansion joints for lower pressure gaseous service, including high temperature flue gas.

These expansion joints are used to add flexibility to industrial ducting systems and fan/blower connections to absorb thermal growth, isolate vibration and noise, and allow for misalignments. Their large movements in a given space, small spring rates, and large temperature range give them advantage not available with other types of joints. They are needed in a wide array of industries, including power, petrochemical, pulp & paper, along with countless other industrial facilities.  A variety of styles and materials are available to meet the specific requirements of any given application.

The high quality fully molded joint types are made from reinforced rubber elastomers, and have the advantage of integral flanges and easy installation.  They can be made with or without molded arches, which can provide additional movement and reliability.

The fabric belt joint types combine different steel frame types with elastomers, fluoropolymers, or composite layered materials for complete versitiliy. 

Also see our metal bellows type duct expansion joints.  Contact us with your application details.

 Fabric Expansion Joints

The fabric belt joint types combine different steel frame types and industry proven materials and options. In some instances, additional components such as insulation pillows, accumulation barriers or flow liners are used to help protect the fabric material. The basics are shown below, but a number of other design elements are possible.

The belt type uses a flat belt flexible element made as a flat belt, and is versitile and effective in terms of manufacture and installation.  And they allow many different types of frames to suit operating conditions.  Various baffles (liners) are also commonly used, depending on the service.  

Attachment methods of the frame to the duct include bolt frames to mating flange, weld frames to mating flange, and weld frames to duct end. Fabric Expansion Joint Frame Types

Chemical resistance, temperature limitations, abrasion resistance, tensile strength and susceptibility to flutter/vibration are major considerations when selecting a flexible element fabric material. They are configured either as a flat-type or convex type.   Types of Fabric Expansion Joints

Materials include elastomers, fabrics, insulation materials and fluoroplastics, either constructed in a single layer or multiple layers. See below for the more common material choices, along with allowable movements for various face-to-face widths.

  • EPDM elastomer flexible element material for fabric belt expansion joints are reinforced with fiberglass, are avaialble in 1/8" and 1/4" thicknesses, and are normally rated for 300F. Low cost, with high tensile strength and excellent resistance to oxygen and ozone. Good flexing characteristics.

  • Fluoroelastomer (FKM) flexible element material for fabric duct expansion joints are reinforced with fiberglass, are avaialble in 1/8" and 1/4" thicknesses, and are normally rated for 400F. Outstanding resistance to chemicals and oils compared to other elastomers.

  • Fluoropolymer flexible element material for fabric duct expansion joints are reinforced with fiberglass, and have a PTFE laminate layer of variable thicknesses  They have excellent chemical resistance, zero porosity, and can be used in wet or dry service. Rated for 600F.

  • Composite flexible element material for fabric duct expansion joints are have a multi-layered design with insulating layers, reinforcing plies, and vapor barriers with either fluoropolymer or elastomeric covers. Movements for a given face-to-face width are less than other materials. Rated for 400F thru 1200F.

  • High quality fully molded rubber duct expansion joints with integral flanges are often used as flexible fan & blower connecotrs, and are available in round and rectangular configurations, and with or without arches. Used in low pressure air & gas services. Any dimensions and flange drill pattern can be accomodated.