Bellows primarily encompass metal bellows, corrugated expansion joints, corrugated heat-exchanger tubes, diaphragms/capsules, and flexible metal hoses. Metal bellows are mainly used to compensate for thermal expansion in pipelines, dampen vibrations, and accommodate settlement-induced deformation; they are widely employed in sectors such as petrochemicals, instrumentation, aerospace, chemical processing, power generation, water conservancy, and metallurgy. Bellows made from other materials, such as plastics, play an indispensable role in applications including fluid transport, electrical conduit, machine tools, and home appliances.
A bellows is an elastic pressure-sensing element used in pressure-measuring instruments. It consists of a thin-walled, cylindrical, corrugated shell featuring multiple transverse folds. Possessing inherent elasticity, the bellows can undergo displacement when subjected to pressure, axial or lateral forces, or bending moments. Bellows are extensively used in instrumentation, primarily as sensing elements that convert pressure into displacement or force. Due to their thin walls, they offer high sensitivity and can measure pressures ranging from tens of pascals to tens of megapascals. Furthermore, bellows can serve as sealing or isolation components-separating two different media or preventing hazardous fluids from entering the sensitive parts of an instrument. They can also function as compensation elements, utilizing their variable volume to offset temperature-induced errors in instruments, or act as flexible elastic couplings between two components. Bellows are categorized by material into metal and non-metal types, and by structure into single-layer and multi-layer configurations. Single-layer bellows are the most common; multi-layer bellows, which offer higher strength, greater durability, and lower internal stress, are typically reserved for critical measurement applications. Common materials for bellows include bronze, brass, stainless steel, Monel, and Inconel.