Metal Expansion Joints
Size: from 1/4" to 300"
Bellows : SS 304, SS 316L, SS 316Ti, SS 321, AL, CU, ... Single or Multiple Layer
Shape: Circular, Rectangular
Configurations:
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EXPANSION JOINT:
Expansion joint is simply a bellows element with end connections. Regardless of accessories, such as liners and covers, it will deflect in any direction or plane that the bellows will. It is the least expensive type, but requires that the piping be controlled as to the direction of the movements required of the unit. The expansion joint should not be expected to control the movement of the pipe. If the piping analysis shows that the expansion joint must accept axial compression, then the piping must be guided and constrained so that only that movement will occur. This expansion joint will not resist any deflections with any force other than the resistance of the bellows, which is a function of the spring rate times the deflection amount. It is incapable of resisting the pressure thrust along its axis, which is the product of the pressure times the effective, or cross sectional, area of the bellows. Large diameter units, even with low pressures, can generate very large axial pressure thrust forces, which must be reacted by main and directional anchors. Otherwise the expansion joint will extend with disastrous results.
Erteash Gostar Peyman Co. has adopted and encourages the use of the definitions of expansion joint components and related equipment as published by The Expansion Joint Manufacturers Association. The definitions are taken, in part, from the Nine Edition of the EJMA Standards.
Definitions:
Axial Movement:
The dimensional shortening and lengthening of an expansion joint along its longitudinal axis.
Lateral Deflection:
The relative displacement of the tow ends of an expansion joint perpendicular to its longitudinal axis. This has been referred to as lateral offset, lateral movement, parallel misalignment, direct shear, or transverse movement.
Angular Rotation:
The displacement of the longitudinal axis of the expansion joint from its initial straight line position into a circular arc, Angular rotation occasionally referred to as rotational movement. This is not torsional rotation.
Torsional Rotation:
The twisting of one end of the Expansion joint with respect to the other end about its longitudinal axis, this twisting generally produces extremely high shear stresses in the bellows. For this reason it is extremely important that special hardware be used to limit the amount of torsional shear stress in the bellows.
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SINGLE EXPANSION JOINT:
The simplest form of expansion joint, of single bellows construction, designed to absorb all of the movements of the pipe section in which it is installed. |
