Fabric expansion joints consist of two major components, the fabric belt material and the metal frame. The frame can connect to the ducting by welding or bolting. Each U.S. Bellows frame style has features designed to minimize the detrimental effects of temperature, movements, pressure, media, and turbulence. The U.S. Bellows team is experienced in evaluating application conditions and implementing designs that lead to long term expansion joint service.
Design alterations can include the following:
Adequate stand off height
Adequate face to face dimension
Inclusion of liner
Frame material
Belt material
Inclusion of accumulation barrier
Inclusion of insulation pillow
Proper bolt hole spacing
And more
Although U.S. Bellows can provide weld-in and bolt-in frame styles, wherever possible, it is strongly recommended that the expansion joint be welded in place.
Weld in design frame styles allow the expansion joint to weld directly to the duct or duct flanges. These frames styles are basic designs that can be augmented with optional components.
Benefits of weld in designs include:
Weld in designs are less expensive to manufacture.
Accurate field bolt hole dimensional data can be difficult to obtain and verify.
Welded connections can accommodate “real world” field conditions and inaccuracies that occur during installation.
Bolt in design frame styles allow the expansion joint to bolt directly to duct flanges or equipment flanges supplied by others. These bolt in designs are generally more expensive to manufacture and are potentially more difficult to install due to hole pattern irregularities and inaccuracies. These frame styles are basic designs that can be enhanced with the optional components.
This 118″ diameter tied universal expansion joint was designed for steam service in a power plant in Alaska. The expansion joint duct, tie rods and cover are fabricated from carbon steel with 304 stainless steel bellows and liner. The overall length is 225″. It was designed for 250°F at 7.25 PSIG and 3.52″ of lateral movement. Dye-penetrant testing, spot x-ray and an air and soap test were performed on the universal expansion joint assembly prior to shipping.
Similar Applications: Fossil Fired Power Plant (Gas Recirculation System), Pulp and Paper Plant (Recovery Boiler to Precipitator), Refinery (Turbo-Expander to CO Boiler and CO Boiler to Precipitator), Cement Plan (Clinker Cooler to Heat Exchanger)
Typical Conditions: 650°F to 850° operating temperature, -10″ to -25″ WG pressure, fuel gas media with heavy particulate, boiler growth contributes to large axial or lateral expansion joint movements depending on the orientation of the joints
Similar Applications: Fossil Fired Power Plant (Air Heater to Coal Pulverizers), Cement (Clinker Cooler to Heat Exchanger)
Typical Conditions: 600°F to 750°F operating temperature, 5″ to 80″ WG pressure, clean air media, boiler growth contributes to large axial or lateral expansion joint movements depending on the orientation of the joints.
Common Design Features:
Fabric Belt: High temperature fabric belt. (FLEXXCEL HT1, HT3, or HT5 depending on maximum temperature.)
Accumulation barrier: 6″ minimum standoff and outboard belt attachment flanges to dissipate heat.
Liner: contoured around expansion joint to allow heat dissipation.
Similar Applications: Cement Plant (Preheat Tower), Refinery (CO Boiler to Precipitator)
Typical Conditions: 250°F to 500°F operating temperature, -35″ to -50″ WG pressure, flue gas with possibly fly ash carryover through air heater, moderate thermal movements in ducting.
Similar Applications: Fossil Fired Power Plant (Re-heater to Chimney), Pulp and Paper Plant (Induced Draft Fan to Chimney), Refinery (Steam Generator to Stack)
Typical Conditions: 250°F to 500°F operating temperature, -35″ to +50″ WG pressure, minimal particulate downstream of precipitator, potential for wet conditions.
Common Design Features:
Fabric Belt: At fan locations, the belt material should have a high resistance to flutter. (FLEXXCEL FF1)
Accumulation barrier: Bolt-in design for attachment to equipment or duct flanges. (If equipment or duct flanges are not present, weld in designs are recommended.)
Liner: Flow liner to reduce turbulence/flutter of fabric belt material.
Similar Applications: Fossil Fired Power Plant (Scrubber Bypass to Stack and Scrubber to Re-heater), Pulp and Paper Plant (Scrubber Inlet and Scrubber to Re-heater)
Typical Conditions: 120°F to 350°F operating temperature, +5″ to +15″ WG pressure, minimal particulate, highly corrosive wet gas, minimal movements.
Common Design Features:
Fabric Belt: Fabric material should have the maximum chemical barrier due to corrosive conditions. (FLEXXCEL HC40)
Recommended Expansion Joint Designs: Style 100W, 300W, 100B, and 500B
A custom fabricated 31″ I.D. turbine expansion joint was designed and fabricated to be placed in service for a company in Texas. The expansion joint unit was reverse engineered, from the previous unit, with improvements to the current design. It is fabricated from 321 stainless steel with Inconel 625 bellows. The turbine expansion joint is 36″ long and is designed for 70 PSIG at 450 deg. F and axial travel of 4″. The expansion joint was 100% dye-penetrant examined and hydro-tested prior to being shipped to the customer.
