The design of Modern Metal bellow expansion joints

  Metal expansion joints 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. 

1.The multi-ply design of metal bellows expansion joint

  In modern expansion joints, the metal bellows expansion joints are often produced with a so-called multi-ply design. And multiple thin plies of metal are layered to form the bellows walls to increase both flexibility and stability. There are two basic design types: The multi-ply and the multi-walled bellows structure. The multi-ply structure consists of a pressure-tight, longitudinally welded outer and inner cylinder of stainless steel. In between these cylinders is an open, spiral cylinder which forms multiple plies depending on the design. The multi-walled structure consists of several concentric, longitudinally welded cylinders. Each cylinder forms a pressure-tight and closed "wall".

2.The main advantages of multi-walled bellows expansion joint:

Resistance to high and very high pressures

Large movement absorption

Small dimensions

Small adjusting force rates

Optimal compensation in a very small space

Early leak indication (in case of damage) via standard check hole

Complete burst resistance

Possibility of permanent leak monitoring in critical media

Economical use of high-quality, corrosion-resistant materials such as Inconel, Incoloy, Hastelloy, titanium and Tantal

Insulation against structure-borne noise up to 20 dB

This design has both technical and economic advantages. For example, the bellows can be constructed of different materials, such as high-alloy stainless steels for the pipes in contact with the medium (inside and/or outside), and low-alloy stainless steels for the intermediate plies.