Concrete Expansion Joints

Fabric Expansion Joints And Their Importance

Expansion joints are devices that are made up of one or more bellows that are meant to assist with structural changes that might be caused by thermal expansion or contraction of a pipe, tube or vessel. Generally expansion joints for pipeline systems are made of various types of metal however recently fabric expansion joints have been introduced on the market and they have lead to some revolutionary results.
Expansion joints play a crucial role in any application where heated, volatile, pressurized or otherwise contaminated gases or liquids are being transferred from one point to another.

Fabric bellows have allowed engineers to tackle the problems of thermal expansion, as well as abrasive and corrosive problems that normally occur in turbine related applications in easier ways. Making use of a variety of fabric membranes and designs, fabric joints can be used for turbine exhaust applications which are particularly problematic because they pose real problems in regards to the long term performance and resistance of the materials.

Metal expansion joints on the other hand are usually used in pipeline systems as they are designed to compensate for the variations that might appear in the pipeline length which are usually due to temperature differences.

When considering the type of assemblies or ducting that fabric joints will have to function with it is crucial to take all the characteristics and conditions into account as these will influence the type and make of joints that you will need.

For instance the joints for a clean air system, meaning that you’re only dealing with a simple intake and exhaust of a ventilation system will never be able to deal with the requirements for moving around gases with a high acid content, as a result of this there is a very wide choice of expansion joints available to deal with any and all possible applications.

The basic design of a fabric expansion joint contains a gas seal membrane which is the exterior part that can be seen after they are installed, a series of insulating layers, back up bars which use clamping pressure in order to create the fabric-to-duct seal while also restraining the fabric when it start to move due to system pressure, metal liner, an accumulation bag, fabric attachment flanges and a gasket. The size and shape of these various components will vary in concordance to the application at hand.

The joint engineers take into account the system thermal expansions which cause variations in temperature and movement when they select the material for each expansion joint. Often times the positioning of joint locations can be chosen in such a way as to optimize the number of joints used, the fewer the better. The location of joints should also be carefully considered in order to assure accessibility for future belt replacements. Depending on the type of fluid that will be transported through the joints these can incur four types of movement: lateral movement, axial compression or extension, torsional deflection and angular deflection.

Fabric expansion joints have represented a great boon for specialty applications but they can as easily be used for more mundane ones such as a flue duct.

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