Introduction of Expansion Bellows

Expansion Bellows (they are also called compensators) are compensating elements for thermal expansion and relative movement in pipelines, containers and machines. They consist of one or more metal bellows, connectors at both ends, and tie rods that depend on the application. They are differentiated according to the three basic types of movement: axial, angular and lateral expansion joints.

Expansion Joins  are elastic vessels that can be compressed when pressure is applied to the outside of the vessel, or extended under vacuum. When the pressure or vacuum is released, the bellows will return to its original shape (provided the material has not been stressed past its yield strength).

Features of Expansion Bellows

1. Reasonable structure, good elasticity, large range of compensation pipeline and little counterforce to the brackets of pipeline.

2. Shock absorption and noise decrease, heat and dust insulation, environmental protection and simple structure bracket.

3. The displacement can be deflected to prevent damagment caused by subsidence of connected brackets and equipment base. It can adapt itself to the centrifugal difference of pipeline installation to provide convenience to installation and maintenance.

4. Good resistance to milling, heat, aging and corrosiveness and long service life.

5. Little resistance and little weight. Each performance is better than the compensation device of other materials.

6. The temperature range of media is wide:-40–300oC

Manufacture of Expansion Bellows

Welded Expansion Bellows can be fabricated from a variety of exotic metals and alloys, whereas formed bellows are limited to alloys with good elongation – brass being a prime example. Welded bellows are not fabricated from brass because of its fundamentally poor weldability. Other advantages to welded bellows include compactness (higher performance in a smaller package), ability to be compressed to solid height with no damage, resistance to nicks and dents, and dramatically greater flexibility.

The welding of metal bellows is a microscopic welding process, typically performed under laboratory conditions at high magnification.

Hydroformed bellows are produced by forcing a metal tube to expand under hydraulic pressure inside a bellows-shaped mold, and assume the convoluted shape of the mold.

Electroformed bellows are produced by plating metal onto a bellows-shaped model (mandrel), and the subsequent mandrel removal by chemical or physical means.