Fabric Expansion Joints — The Expansion Joints Blog

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Find Your Fabric Expansion Joint by Applications

August 13th, 2012 Comments off
High Temperature Dirty Flue Gas
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

Common Design Features:

Fabric Belt: Un-insulated fabric material. (FLEXXCEL HD7)

Accumulation barrier: Fills expansion joint cavity to minimize the accumulation of particulate.

Liner: Flow liner to retain the accumulation barrier and protect the belt from abrasion.

Recommended Expansion Joint Designs: Style 200W, 100W, 300W, 600W, and 700W

Fabric Expansion Joint Movement Illustration
Turbulent Air
Similar Applications: Pulp and Paper Plant (Primary Air to Recovery Boiler)

Typical Conditions: Ambient temperature, 40″ to 50″ WG pressure, clean air movement mainly limited to vibrations

Common Design Features:

Fabric Belt: At fan locations, a flutter resistant fabric belt material should be used. (FLEXXCEL FF1)

Accumulation barrier: Bolt-in design for attachment to equipment or duct flanges.

Liner: Flow liner to reduce turbulence/flutter of fabric belt material.

Recommended Expansion Joint Designs: Style 200B, 100B, 300B, 400B, and 500B

Fabric Expansion Joint Movement Illustration
High Temperature Clean Air
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.

Recommended Expansion Joint Designs: Style 200W, 100W, 300W, 200B, and 100B

Fabric Expansion Joint Movement Illustration
Dirty Flue Gas
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.

Common Design Features:

Fabric Belt: Un-insulated fabric material. (FLEXXCEL HD7)

Accumulation barrier: Fills expansion joint cavity to minimize the accumulation of particulate.

Liner: Flow liner to retain the accumulation barrier and protect the belt from abrasion.

Recommended Expansion Joint Designs:Style 200W, 100W, 300W, 600W, and 700W

Fabric Expansion Joint Movement Illustration
Turbulent Flue Gas, Wet Gas
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.

Recommended Expansion Joint Designs: Style 200B, 100B, 300B, 400B, and 500B

Fabric Expansion Joint Movement Illustration
Low Temperature Wet Flue Gas
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

Fabric Expansion Joint Movement Illustration

Directional Movement for Fabric Expansion Joints

July 30th, 2012 Comments off

Directional Movement for Fabric Expansion Joints

Fabric Expansion Joint Diagram Showing Axial Compression

Axial Compression

The reduction in the breach opening along the axis of the duct. This is usually a result of thermal expansion of the ducting.

Fabric Expansion Joint Diagram Showing Axial Extension

Axial Extension

The increase in the breach opening along the axis of the duct. In certain configurations, the duct thermal expansion may result in extension at the expansion joint location.

Fabric Expansion Joint Diagram Showing Laterial Movement

Lateral Movement

The relative movement of the upstream and downstream faces in the direction perpendicular to the axis of the duct.

Fabric Expansion Joint Diagram Showing Torsional Rotation

Torsional Rotation

The twisting of one side of the duct about the longitudinal axis.

Fabric Expansion Joint Diagram Showing Angular Rotation

Angular Rotation

The twisting of one side of the duct about an axis perpendicular to the longitudinal axis.

View our online fabric catalog for more information on fabric expansion joint movement

Fabric Expansion Joints and Factors Influencing their Design

July 16th, 2012 Comments off

Fabric Expansion Joints and Factors Influencing their Design

Rectangular Fabric Expansion Joint with a Three Layer Fabric BeltFabric expansion joints perform a function of compensating for duct misalignment and duct thermal growth typical in power plants and other ducting systems. Proper design of these joints starts with asking the right questions about the application, providing the correct answers, and applying design rules to arrive at the appropriate solution.

The guiding principle for fabric joint design is to protect the fabric belt element so that it can absorb movement while retaining the media. The longevity of the belt life can be diminished by many factors. These factors include excessive temperature, harsh corrosives, exposure to abrasive particulate, excessive movements, fly ash weight against the belt, and high internal pressures. All of these problems can be solved if they are anticipated. The quality of the expansion joint design is only as good as the information provided up front. A realistic and accurate analysis of the system is step one. Assuming that is taken care of, these guidelines are a brief introduction to factors that influences the success of the expansion joint.

Temperature

http://www.usbellows.com/images/literature/sample-multi-layered-fabric-ej.jpgFabric gas seal membranes have specific temperature capabilities. When necessary, the addition of insulating materials between the temperature source and the belt will extend the service life. The magnitude of the temperature will determine the thickness of the integral belt insulation and if a separate high density insulation pillow is required.

The belt attachment flanges should be outboard of the cavity and have sufficient standoff from the duct. Care should be taken to avoid external insulation or lagging outside of the belt which prevents proper heat dissipation.

Chemical Attack

Applications that do not have high temperatures sometimes have a different problem. Relatively low temperatures in flue gas ducting can lead to corrosive condensation. In these situations, a chemical barrier is required to protect the load bearing fiberglass carcass of the belt. External insulation over the joint in these locations can reduce condensation and heat loss.

Movements

High Temperature Round Fabric Expansion Joint Cross SectionGenerally, movements occur along the axis of the duct (usually compression but occasionally extension) or at right angles (lateral). The key to being able to handle these movements is having the proper width of belt installed in a sufficient span. For compression, a ratio of installed belt span to movement roughly at 4:1 is suggested. The lateral capability is influenced by the amount of belt slack available. Concurrent axial compression will provide the slack thus allowing more lateral. In certain situations, there is lateral offset in the cold installed condition. This may require “pre-compression” of the joint which is in essence just providing extra belt width.

Abrasion

In flue gas ducting with particulate, a liner should be used to protect the belt from direct exposure. If the pressure is negative, the belt stand-off from the gas stream should be increased to keep the belt from being pulled into the gas stream or against the liner. Belt clamping bar edges next to the fabric should be radiused. The belt attachment flange should also be smooth and free of rough surfaces.

Pressure Fluctuations

Fabric expansion joints exposed to sudden pressure fluctuations, such as near ID fans and dampers, may result in the belt “fluttering”. The fabric will fatigue over time resulting in tears. Using stiffer fabric material, installing a liner and increasing the standoff are steps to take to avoid flutter.

Summation

Each location throughout a ducting system can have different conditions that affect the design of expansion joints. As a result, there isn’t one design that can fit all applications. The goal of the expansion joint supplier is to work with engineers and end users to provide the optimum economical solutions.

View the full online Fabric Expansion Joint Catalog.

What is a fabric expansion joint, how do they work and what are the advantages of design integration?

July 2nd, 2012 Comments off

What is a Fabric Expansion Joint?

Diagram of fabric expansion joint in a power plantFabric expansion joints perform a function of compensating for duct misalignment and duct thermal growth typically 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.

Fabric expansion joints can absorb larger movements than metal expansion joints and do so without spring loads. This is critical to limiting thermally induced stresses in ducting, ducting supports, and related equipment.

How Does a Fabric Expansion Joint Work?

Frabic Expansion Joint Movement DiagramA fabric expansion joint is inserted into a gap in the ductwork where movement will occur. A fabric expansion joint has two main components — the fabric gas seal and the metal frames. The fabric gas seal is a closed loop, like a belt, with its two edges clamped all around to the metal frames that are in turn connected to the end of ducting. As the ducting moves the fabric belt deforms. The fabric material must do this without tearing or leaking while sometimes being exposed to high temperatures and/or corrosive media.

In some instances, additional components such as insulation pillows, accumulation barriers or flow liners are utilized to help protect the fabric material. The following section describes the basics of fabric expansion joint components and how they are designed.

Design Integration for Fabric Expansion Joints

Expansion Joint Assembly with Duct WorkIn addition to fabric expansion joints, U.S. Bellows is a major designer and fabricator of ducting. Design Integration is the design, manufacture and shipping of expansion joints integrated into the ducting as a complete unit directly from U.S. Bellows. This enables U.S. Bellows to offer optimum system design and the lowest installed cost.

Design Integration Advantages:

  1. Elimination of flanged connection gasketing and potential leaks.
  2. Elimination of the risk of installing sensitive assemblies at the job site.
  3. Fabric Expansion Joint Duct WorkSignificant costs savings of both manufacturing and installation labor.
  4. Delivery of the largest “shippable” duct and piping sections to the job site to eliminate as many filed connections as possible, further reducing installation labor.
  5. Minimize the number of flanged expansion joint connections.
  6. Allows integration of ducting to serve as expansion joint flow liner.
  7. Allows expansion joint frames to take the place of duct stiffeners.
  8. Elimination of labor to install flanged expansion joint assemblies at the job site.

Fabric Expansion Joint Style 100WU.S Bellows has considerable experience in design and fabrication of integrated ducting with metal and fabric expansion joints. U.S. Bellows is also very knowledgeable with transportation capabilities for wide and heavy loads and can make firm commitments “up-front” for the largest shippable size and heaviest weight.

The drawing below shows a cross section of an expansion joint designed to allow the ducting to serve as a flow liner. The joint frame takes the place of a stiffener flange. The complete duct/expansion joint ships as one factory assembled component.

Neoprene Fabric Expansion Joints for a Ventilation Fan Intake Duct

May 21st, 2012 Comments off

Neoprene Fabric Expansion Joints for a Ventilation Fan Intake Duct

Neoprene fabric expansion joints were custom designed for a ventilation fan intake duct in a power plant. They are 42″ in diameter and are 65″ in overall length. They were designed for 1/4″ axial movement, 1/8″ lateral deflection and a 100″ water column at 200°F. The expansion joints are fabricated with a neoprene reinforced belt with stainless steel clamps, carbon steel spool pipe and angle flange ends. Each joint was dye penetrant examined prior to shipping.

Fabric Expansion Joints Designed for a Lignite Coal Processing & Gasification Plant

April 23rd, 2012 Comments off

Fabric Expansion Joints Designed for a Lignite Coal Processing & Gasification Plant

Fabric Expansion Joints Designed for a Lignite Coal Processing & Gasification Plant

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 from High Temp. Furnace Bags to E.J. and Duct Work Assemblies

April 16th, 2012 Comments off

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.

Air Duct Fabric Expansion Joint 44" Diameter Fabric Expansion Joint 24" Diameter Fabric Expansion Joint
Air Duct Fabric
Expansion Joint
44″ Dia. Fabric
Expansion Joint
24″ Dia. Fabric
Expansion Joint

Get pricing now for your next fabric expansion joint project.

High Temperature Furnace Sealing Bags Designed to Prevent Heat Loss

April 2nd, 2012 Comments off

Furnace Sealing Bag, A High-Temperature fabric Expansion Joint

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.

Furnace Sealing Bag, A High-Temperature fabric Expansion Joint

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.

Browse Our Brand New Fabric Expansion Joint Catalog Online

March 26th, 2012 Comments off

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.

Browse our fabric expansion Joint catalog!

  1. Learn About Fabric Expansion Joints
  2. Find the Right Fabric Expansion Joints by Applications & Conditions
  3. Fabric Expansion Joint Design Styles
  4. Fabric Expansion Joint Materials

Where Fabric Expansion Joints are Typically Used in a Fossil Fired Power Plant

March 2nd, 2012 Comments off

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.

Expansion Joints in a Typical Blanced Draft System with a Cold Precipitator

**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

 

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