An expansion joint is a flexible connection that allows a pipeline or structure to expand and contract. They also dampen vibrations and misalignments caused by temperature fluctuations, mechanical movements, and other environmental conditions. The location of an expansion joint is important for optimum performance. It should be placed in a position with adequate movement allowances, sufficient ambient cooling, and simple accessibility. In addition, the positioning of anchors and supports should be considered.
While most Expansion Joints are made from metal, they can be made of a variety of materials. They can be prefabricated or built on site. Precompressed foam expansion joints provide a weathertight, primary seal that self-expands and is capable of up to 50% movement from their mean joint size. Precompressed foam also provides water resistance and fire resistance. It is a popular choice for ducting applications and offers an advantage over traditional concrete expansion joints.
A toroidal expansion joint consists of an assembly of bellows with convolutions that can absorb changes in axial stroke while absorbing vibrations and reducing pressure-induced deformation. These bellows are manufactured hydraulically under high-forming pressure. Toroidal expansion joints are available in various diameters and lengths, as well as different materials and finishes. For example, some have an aluminized coating that increases corrosion resistance and reduces the amount of oil used to form the bellows.
Many expansion joints are installed in ducts, but they can be found in other applications as well. For instance, they can be used in concrete structures to mitigate vibrations and displacement resulting from seismic activity, and they are often used in bridges to allow them to expand and contract in response to traffic loads.
A properly sized, designed, and fitted expansion joint should not require maintenance, but regular inspections are recommended to ensure that they are functioning as intended. This will help identify any wear indicators and ensure that the expansion joint is able to handle its intended range of motion.
When expansion joints are used in concrete structures, they should be designed to adapt to a wide range of forces that can cause movements. These forces can include thermal expansion and contraction, soil-setting and creep, seismic activity, wind or traffic-weight displacement, and other environmental conditions. These forces can also cause movement of concrete slabs and walls that are not connected to the expansion joint. This type of movement can cause cracking, buckling, and other damage to the concrete. An expansion joint can prevent these problems from occurring if it is properly designed and positioned. If not, the expansion joint can deteriorate or close up over time, leading to failure and causing concrete damage. By using an expansion joint that is designed to withstand these forces, you can protect your concrete investment and extend the lifespan of your concrete structures. For maximum protection, use an expansion joint that is certified to a fire-resistance rating such as UL 2079 for deck and wall applications. UL 2079 requires that the expansion joint pass a fire-resistance test and a joint cycling test to ensure that it will not fail due to heat exposure.