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
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
Source: Mercer Rubber Co.