——— General Description ———
In practice, pipe riser Isolation is used for one or both of two functions. The first is to isolate the pipe from the structure and thereby minimize the noise and vibration transmitted into the structure by the vibrations that may be carried along the riser itself. The second, more common reason is to address the issue of relative expansion and contraction between the piping and the structure.
As there is nothing special about the vibration isolation application, this document will address the more specialized expansion/contraction issue.
Expansion or contraction occurs when in service, the fluid carried by the pipe is either heated or cooled. As the temperature of the pipe shifts away from the temperature of the structure, the pipe will either grow or shrink relative to it as well. As risers tend to be relatively long, a few degrees of temperature change can often result in as much as an inch length variation. If the pipe was to be hard-mounted, this growth or shrinkage could damage the riser, the support structure, or both.
The use of spring coils for riser support allows the pipe to grow or shrink with a minimal change in the support forces. Higher deflection coils allow greater expansion of contraction of the pipe where lower deflection coils allow less. Pads allow virtually none and hard mounting allows none at all. The appropriate suspension system needs to be selected based on a number of different factors that can vary from project to project.
