A tied universal expansion joint was custom designed for service in an acid regeneration plant in Louisiana. It is 48″ in diameter, 141″ in overall length and designed for 1″ axial movement, 2-1/2″ lateral movement and .33° angular rotation. The expansion joint is fabricated with 310 stainless steel bellows, and 301 SS liner, duct, flanges, transition duct and covers. It was designed for 10 psig at 1150°F, and was dye penetrant examined, hydro-tested at 15 psig, and the bellows and pipe longitudinal weld seams were 100% x-rayed.
A total of thirty-six fabric expansion joints were custom designed for a lignite coal processing and gasification plant in Mississippi. They are 12″ diameter, 14″ overall length and designed for 1/4″ axial movement and .8″ lateral movement. The expansion joints are fabricated with carbon steel flange ends, stainless steel clamps and a PTFE coated fabric belt. They are designed for hot air circulation flow at 600°F and a pressure of 30″ water column.
Fabric expansion joints are often used in ducts which carry hot gases at low pressures. The major design parameters are the temperatures and flow rates of the gases and the amount and abrasiveness of solids suspended in the gases. Layers of different fabrics insulation can be combined to accommodate the temperatures and pressure in the system. We specialize in all types of fabric expansion joints from high temperature furnace bags to fabric expansion joint and duct work assemblies.
View the Materials Comparison Chart to see the details behind each material used in fabric expansion joints.
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Air Duct Fabric
Expansion Joint |
44″ Dia. Fabric
Expansion Joint |
24″ Dia. Fabric
Expansion Joint |
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These universal metallic expansion joints were custom designed for an offshore application. They are 42″ diameter, 24″ overall length and designed for 2″ axial movement and 1-1/2″ lateral movement. The expansion joints are fabricated entirely from 316 L stainless steel and designed for 1,000°F and 1 psig. Each unit was 100% dye penetrant examined and soap and air tested prior to shipment.
A special type of high-temperature fabric expansion joint developed by U.S. Bellows, Inc. is the furnace sealing bag. The objective of the bag is to seal the air inlet conduits’ penetrations into a furnace and thus prevent heat loss. Because of thermal expansion of both the conduits and the furnace, the bag must be able to expand and contract during normal cycles of operation.
The bag consists of a tapered sleeve formed from layers of flexible, flame and heat-resistant impervious fabric, which is connected at its upper end to another sleeve in the furnace floor. The lower end of the bag is connected to the air inlet
conduit (usually a pipe) so as to form an airtight seal. The connection to this pipe is made such that the fabric is collapsed when the furnace is cold and extended when the furnace is hot. When required, a tapered coil spring formed from suitable metal is installed around the conduit inside the bag. This prevents the fabric from collapsing inward during vacuum conditions inside the furnace. For most applications, band straps may be used to attach the bag at both ends.
Read more in this technical bulletin on High Temperature Furnace Seal Bags.
U.S. Bellows is proud to release our online fabric expansion joint catalog!
Fabric expansion joints perform a function of compensating for duct misalignment and duct thermal growth typical in power plants and other ducting systems. Fabric expansion joints are found wherever there is a need to convey hot media in low pressure applications such as “in flowing air” and “out flowing gas” in large combustion processes.
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These universal metallic expansion joints were custom designed for a chemical plant in Texas. They are fabricated entirely from stainless steel with 304 stainless steel bellows. The expansion joints are 12" diameter, 77-1/2" long and designed for 4-1/2" axial movement and 2" lateral movement. They were designed for 200°F and 100 psig. Each unit was 100% dye penetrant examined and hydrotested prior to shipment.
U.S. Bellows designed and fabricated tied universal expansion joints and single hinged expansion joints for a power plant in Canada. All the units were fabricated from carbon steel with 316 stainless steel bellows. The universal tied joints are 102″ diameter, 225″ long and are designed for 8.2″ lateral movement. The hinged joints are 102″ diameter, 71″ long and designed for 0.76° angular rotation. Each expansion joint can withstand temperatures up to 250°F at 7.25 psig. The bellows and pipe long seams were 100% x-rayed, and all the welds were 100% dye penetrant tested. A soap and air test was performed prior to shipment.
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
The two assemblies shown, a mitered elbow duct work and fabric expansion joint and duct work assembly, are designed for a sulfuric acid plant. Both assemblies are fabricated from 1/4" thick 304L stainless steel. They are designed for a 15" water column with a temperature of 180°F, axial compression of 3/4", and lateral movement of 3/4". A dye penetrant examination is performed on all welds prior to shipment.
