Bustduct Bellows: A Guide

Flexible connectors are used in ducting systems to reduce vibration transmission, shock and accommodate thermal movements with minimum stress to the ductwork. Since pressure requirements in ducts are very low compared to piping systems, they are manufactured in lighter construction to be more responsive to the reduced stiffness of sheet metal ducting. Designs are always airtight to prevent particle intake or leakage.

These products come in many configurations as no standard design can meet the varied scope, service or connection requirements. They can be round, square, rectangular, round on one end and square on the other and even “T" or “L" shaped. Concentric and Eccentric Reducers are common and custom made designs can be made to offset or compensate for older misaligned heavy ducting systems. The common characteristics are flexibility and long life. Motion requirements are met with single and multiple arches and by varying the face-to-face length.

Materials

Sometimes the duct joints are in all rubber with no reinforcement, but the most common construction is natural rubber or synthetic liner, plies of rubber impregnated tyre cord or fabric and a rubber cover. When pressure or vacuum conditions are extreme, wire of steel ring reinforcement is used as well.

Polymers available are Natural Rubber, EPDM, SBR, Neoprene, Butyl, Hypalon, Nitrile, Silicone and Viton. Reinforcement may be square woven fabric but more commonly Nylon, Polyester or Kevalr tyre cord.

These Bellows can also be in Aluminum for Busduct Applications in Round and Rectangular Configuration.

Connections

Duct joints can be slip-ons retained by lightweight or heavy banding. Most of them are flanged and we can work to your requirements. We can supply the steel back up flanges in individual pieces in carbon steel, stainless steel, aluminum or any other required material. Carbon steel is normally painted, but can be hot dip galvanized or electroplated.

Liners

When temperatures are very high or the gases contain particle concentrations that tend to build up, carbon or stainless steel liners are often used. These liners pass through the duct connector and enter the adjacent ducting system to minimize damage and increase the service/cycle life of the duct connector.

Different Types of Busduct Bellows

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