Expansion Joints / Metallic Bellows / Flexible Bellows

Sohail Engineering Corporation is leading manufacturer of expansion joints and bellows. Thermal growth, cyclic movement, equipment vibrations or pressure pulsation causes a growth in piping system. Now if this growth is not absorbed by the system itself, an expansion joint is a perfect solution to go for.

Factors determining the selection of bellows:

     *Temperature     * Pressure     *Media     *Size     * End Fittings     *Motion

Bellows Movements:

There are three main movements that an expansion joint can take. These are axial, lateral and angulation.

Axial Movement:

Axial movements is the change in length of bellows in longitudinal direction. These movements can be either compression, extension or a combination of both. Compression is always shows with negative sign (-) and extension with a positive sign (+). The unit of axial spring rate is displayed in N/mm.

Axial Movements

Lateral Movement:

Lateral movement is the displacement of one end of bellows to the other end in a direction perpendicular to horizontal axis. Lateral movement can be absorbed by a single bellow, but the degree of freedom is very small. Hence to achieve greater lateral offset two bellows are joined together with central pipe. This result in greater offset and much lower offset forces. The units of lateral spring rates is displayed in N/mm.

Lateral Movements


Angulation Movement:

Angulation movement is the rotational displacement of a bellow. The corrugations at the most inner point are in compression whereas those at furthest away are in extension. The angulation of one bellows is often compensated with the second bellow in line. The angulation spring rate of bellow is displayed as Nm/deg.

Angular Movements

Kinds of Metallic Bellows:


Standard Bellows:

Single Un-restrained Bellows                            Single Tied Bellows                                       Universal Un-restrained Bellows                           

Universal Tied Bellows                                      Hinged Bellows                                               Double Hinged Bellows    

Gimbal Bellows                                                    Warsila, CAT, Niigata & Jenbacher


Specific Bellows:

High Pressure Bellows                                         Thick Wall Bellows

Jacketed Bellows                                                  Rectangular Bellows

Clamshell Bellows                                                   In-Line & elbow pressure expansion joint