Thermal Linear Expansion of PVC and CPVC Pipe

时间：2016-07-09 10:39:35点击：次

Thermal expansion and contraction is fairly common inmost piping materials. The coeficient of linear expansion or expansivity for PVC and CPVC pipe is the ratio of the change in pipe length per degree change in temperature.
Adjustments for Above-Ground Thermal Expansion and Contraction
When designing  for  the use of any expansion  joint, it should be  remembered  that  this  joint  is usually considered  to be  the weakest  link  in  the entire piping system. The  responsible project engineer should determine the system requirements and then evaluate the design  feasibility of each  type of  joint. To get an dea of what  is available, here are some of  the more common variations of joints:Expansion Loop - A fairly simple but eficient method for growth control. Expansion  loops generally contain no moving parts (o-ring seals or gaskets) and are easily fabricated from pipe and elbows. Their drawbacks are of  f s e  t space requirements and  limitations on  large diameter pipe.Flexible Bend - This  type of  joint (plastic or metallic) is available  in many configurations. They absorb excessive vibration, allow multi-directional movement, and correct  for mis-alignment or structural shift  in the system. Negatives are pressure  limitations and resistance  to corrosive  fluids  in  the case of 100% metallic bends.Plastic Piston Expansion Joint - Usually a fabricated device constructed by  telescoping  two pieces of pipe. They will allow  for considerable movement  in a  linear direction only. For this reason, careful alignment is very necessary for smooth operation. The critical component in this device is the elastomeric oring seal, which must be evaluated for chemical and heat resistance as well as positive sealing characteristics during wear.
Bellows and Rubber Expansion Joints  - of  these joints will absorb growth  in  the system due  to  thermal changes and will allow  for dynamic movements of machinery, support structures, and buildings. Rubber expansion joints will allow for axial, lateral, angular and torsional movement. Both types are installed in-line and are  fairly compact. The manufacturer of each should be consulted to determine speciic design advantages and limitations.
Bellows and Rubber Expansion Joints  - of  these joints will absorb growth  in  the system due  to  thermal changes and will allow for dynamic movements of machinery, support structures, and buildings. Rubber expansion joints will allow for axial, lateral, angular and torsional movement. Both types are installed in-line and are  fairly compact. The manufacturer of each should be consulted to determine speciic design advantages and limitations.

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