Written by: John Breen for Piping Design Central


Hanger spacing charts for horizontal "runs" of pipe are based upon limiting the bending stress in the horizontal piping (and they DO NOT address concentrated loads like large valves). Supporting vertical piping is quite a different thing.


How a vertical riser is supported depends greatly upon its operating temperature. If you support the "hot" riser near its top, the pipe will expand down its length so that the total expansion displacement at the bottom of the riser may make the rest of the support scheme difficult to design. Similarly, the opposite situation is to be expected if you were to support the riser too close to its bottom. If there is rotating equipment to consider the expansion of a long riser may require some "creative" design work.


Generally, you will want to support the riser as near to its top as is practical (if rotating equipment is not an issue) so that the weight of the vertical piping will cause a tensile loading in the pipe wall. Compressive vertical loadings in pipe risers that are supported at their bottom tend to cause column buckling loadings (instability) in the vertical piping.


In some long vertical risers in power plants (main steam, hot reheat, cold reheat, etc.) you will see the piping supported by a "rigid" rod hanger pair somewhere near the "midpoint". Then there will be spring hangers above the "rigid" location (elevation) and also be spring hangers below the "rigid" location (elevation). The height on the riser where the "rigid" rod hanger is located will be at about the same elevation as the point where the piping terminates at the connection to the turbine.


Pipe support design includes equal shares of science and art. Our good fortune is that we are now blessed with computers.


You may benefit from the knowledge that Anvil-Grinnell has a FREE hanger design manual available that will give you a lot of design background and some valuable design data. You can download it here:


http://www.anvilintl.com/SharedContent/Pdf/Literature_Catalog/PipeHanger_DesignEngineering_Catalog.pdf


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