The Fabric Expansion Joint is a single or multilayer construction made with glass fiber or ceramic fibers and insulation materials. The expansion joint absorbs the thermal originated movements as well as vibrations and pipe or ducts torsion. Flexibility is the key word for the Fabric Expansion Joints. SAFETECH may design and fabricate every type of Expansion Joint to exactly meet your installation demands. The advantages of the Fabric Expansion Joints are:
- No transmission of reactive stress
- No transmission of vibrations and resonance
- Only one expansion joint may absorb different directions movements a the same time
- Noise reduction
- Easy installation
- Fabrication program for temperatures up to 1000 ºC.
Single layer fabric expansion Joints
The Single Layer Expansion Joints are fabricated with one layer of Fluorelastomer or Fluoroplastic material, internally reinforced by a fabric or metallic wire mesh. Their main field of application corresponds to the duct lines where there is a high concentration of condensed fluids. The Single Layer Expansion Joints are high density elements and provide a high chemical resistance.
Multilayer fabric expansion Joints
The flexible element of a “Multilayer Textile Expansion Joint” is built by superposing individual layers of different materials, each contributing to the whole a certain desired feature allowing it to withstand the severe service conditions that will affect the expansion joint throughout its service life. The chemical nature of the circulating gases, the content of particles in suspension and their characteristics, the ﬂow regime, temperature, pressure and its fluctuation over time, the combination of movements and number of cycles are some of the factors that condition the choice of materials and their quantity, dimensions and assembly sequence.
A The external layer shelters the compensator from weathering, since moisture, air, UV radiation and acid rain harm the materials found in the inner layers. PTFE, silicone and other elastomeric materials such as Viton® and EPDM are used in this outer layer.
B The core of the expansion joint is an impermeable layer that acts as a chemical barrier providing the desired gas tightness for the compensator. A varying range of different grades of PTFE films are the common choice at this level, however certain elastomers may also be used.
C In the thermal insulation stage, materials such as glass fibers or ceramic felts reduce the high temperatures transmitted by the circulating gases, thereby protecting the thermally sensitive upper layers (A and B) from over-heating.
D The inner layer is in direct contact with the ﬂ owing gas and provides mechanical protection for the other layers and structural integrity for the overall assembly. Stainless steel and Incoloy wire meshes, glass fiber, ceramic or silica fabrics are the materials of choice.
Construction of a fabric expansion joint
These joints comprise the following elements:
A The Expansion Joint itself may be constructed with single or multilayer flexible elements that incorporate a gas seal membrane (chemical and permeability barrier), a thermal insulation layer and reinforcing members.
B An extra reinforcement layer in the flange area protects and isolates the flexible elements in contact with the steel parts.
C The back-up bars clamp the flexible element to the steel frame of the duct. The width, distance between drill-holes, thickness, etc., depend on the type of expansion joint and the operating conditions.
D Bolts, their nuts and washers deliver the optimum clamping force.
E The ductwork steel frame is a flanged structure supporting the expansion joint. Frames can be designed as per a wide range of geometries determined by the operating conditions. Steel frames may include internal sleeves or baffles aimed at providing mechanical protection for the flexible element and insulation bolster, avoiding the harmful effects of turbulent ﬂow, the entrance of solid particles and erosion by high velocity gases.
F The insulation bag or bolster is a ‘pillow’ filled with insulating material that protects the expansion joint flexible element against high temperatures, mechanical damage resulting from turbulent flows with high solid particle contents and/or high velocities. Additionally, it provides considerable noise reduction.