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Rubber Expansion Joints

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Typical Piping Layout

This simple illustration shows typical applications. While most pump inlets are under pressure, a pump used in lifting service must have a vacuum joint (1) on the pump suction. Once past the pump to the discharge, joints (2) are selected for pressure.

It is always best to install the expansion joint (2) on the equipment side of the valve, as it simplifies inspection or replacement. If the piping is anchored near the pump and by an anchor before the next expansion joint, there is no need for control rods.

Expansion joints (3) and (4) are designed to take the expansion or contraction between two anchors. Since all the thrust force will be taken by the anchors, no control rods are needed. If there is a long run between anchors, there will be movement at the intermediate points and the pipe should be supported by sliding guides (5).

At location (6), the piping is not anchored on either side of the expansion joint. Control rods must be used to take the pressure thrust or the expansion joint will drive the piping and probably fail. When control rods are added, the expansion joint will always be in the full open position and will not accept additional axial extension. Expansion joints using control rods can still handle compression, transverse and angular movement.

Source: Mercer Rubber Co.