Metal Bellows

Metal bellows 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).

There are two main types of metal bellows - formed and welded.

Formed Bellows
Formed bellows are produced by a variety of processes, including cold forming(rolling), electroforming and hydroforming.
Hydroformed bellows are produced by forcing a metal tube to expand under hydraulic pressure inside a bellows-shaped mould to assume the convoluted shape of the mould whereas rolled formed bellows are mechanically formed using rollers.

Welded Bellows
Welded bellows (also called edge-welded or diaphragm bellows) are highly flexible. These are manufactured by welding a number of individually formed diaphragms to each other both in the ID and OD.