The Expansion Joints Blog

See an example of how fabric expansion joints are being used with ducting. The figure below represents a typical balanced draft system with a “cold” precipitator. The black components represent the locations of fabric expansion joints throughout the system.

**The examples above are representative and should not be used for design. The user should obtain actual values for the particular system being considered

The main sections of the ducting are as follows:

• FD Fan to Air Preheater
• Air Preheater to Boiler
• Air Preheater to Pulverizer
• Air Preheater to Inlet from Boiler
• Air Preheater to Precipitator or Bag house
• Precipitator or Bag house to ID Fan
• ID Fan to Scrubber
• Scrubber to Stack

Fabric expansion joints are often used in ducts which carry hot gases at very low pressures. Layers of different fabrics and insulation can be combined to accommodate the temperatures and pressure in the system.

Round Fabric Expansion Joints

Fabric expansion joint applications include, air and flue gas duct systems, flue gas desulfurization systems, gas turbines and diesel engine exhaust, incinerators, etc.

Rectangular Fabric Expansion Joints

Materials for fabric expansion joints include: silica cloth, mineral wool insulation pillows, PTFE coated fiberglass, ceramic fiberglass and aluminum coated fiberglass.

Furnace Sealing Bag

A special type of high temperature fabric expansion joint developed by U.S. Bellows, Inc. is a furnace sealing bag. The objective of the bag is to seal the air inlet conduits penetrations into a furnace and thus prevent heat loss.

View the Technical Bulletin on Furance Bags