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Glossary
Differential Expansion
Differential expansion is the difference in how much two materials or components expand or contract with temperature change. It happens because materials have different coefficients of thermal expansion and because parts in an assembly may heat or cool at different rates, so they don’t all change size by the same amount at the same time.
In bolted industrial joints, differential expansion matters because it can change clamp load and sealing stress. If the flanges, gasket, and bolts expand by different amounts as temperature rises (or cools), the joint can see preload increase or decrease, sometimes unevenly around the bolt circle. Over repeated thermal cycles, that shifting load can contribute to gasket relaxation/leakage, bolt loosening or yielding, joint distortion, and fatigue—especially in equipment like heat exchangers, piping flanges, and pressure vessels where temperature swings are routine.