Most engineers and installers treat thermoplastic piping systems like metal during design and installation. As a result, mechanical stresses get permanently locked into the piping system, which can reduce its life expectancy. This is the most common failure mode of a piping system.
Piping systems are dynamic. They expand and contract due to temperature changes in the ambient environment and the media flowing inside. There may also be a significant temperature difference between time of installation — when the piping gets clamped in place and restrained — and when the system starts operating. Plastics expand and contract at greater rates than metal (see Figure 1). All these factors must be taken into account for proper installation. For example, if a contractor at a food production facility installs a 100-ft straight run of polyvinyldene fluoride (PVDF) pipe on a cool morning (50°F), it will expand 2.88 inches in length when the ambient temperature rises to 80°F. To find out more, you can read the full article here.