Metallic Bellows Expansion Joint

The simplest type of expansion joint consists of a single bellows element welded to end fittings, normally flange or pipe ends. The single bellows can absorb small amount of axial , lateral & angular movement. The addition of tie rods to a single bellows assembly adds design flexibiltiy to a pipe system. The tie rods are attached to the pipe or flange with lugs that carry the pressure thrust of the system , eliminating the need for main anchors.

The double expansion joint extends the magnitude of flexibility and is primarily utilized for straight axial motion. when used in combinationwith other movements, the predominant motion is straight axial.Each bellows acts as a single Expansion joint and absorb the movement of the pipe section in which it is installed (independently of the other bellows). Not to be confused with universal expansion joints.

The Universal Expansion Joint (articulated double expansion joint-containing two bellows joined by a common connector for the purpose of absorbing any combination of the three basic movements : Axial, Lateral and Angular) usually furnished with control rods to distribute the movement between the two bellows of the expansion joint and to stabilize the common connector.
Overall control rods govern the movement of the centre pipe section and equally divide motion between the bellows elements. This configuration is used primarily for lateral deflection but can accommodate axial movement as well. Another application for this type of expansion joint utilizes overall tie rods which fix the overall length of the expansion joint and contain full pressure thrust (only lateral deflection is accommodated)

The hinged expansion joint can absorb angular movement in one plane. Hinged assemblies are normally used in sets of two or three to absorb large amounts of expansion in high pressure piping systems. Only low spring forces are transmitted to the equipment. The hinged hardware is designed to carry the pressure thrust of the system, and often times, used to combat torsional movement in a piping system.

An In-Line Pressure Balanced Assembly is designed to absorb small amounts of axial and lateral movement while counteracting the pressure thrust in a system. This is achieved with a series of rods similar to the Pressure Balanced Elbow Assembly and a balancing bellows with twice the effective area as the line bellows. The elimination of the elbow is what makes this expansion joint unique.

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