Companies spend a significant amount of time and energy selecting the best type of pipe material for the application, calculating size and lengths needed, and following and implementing standard instructions for proper pipe installation.
Even when all this is carefully completed, there can still be problems with premature pipe failure or pipe damage that leads to leaks. In either case, the result is the same - costly downtime for repairs or replacement.
The main reason plastic piping failure still occurs is that many in the industry design and install thermoplastic piping systems in the same way as metal. Using metal pipe methods in plastic systems causes mechanical stresses to become permanently locked into the piping system, reducing its life expectancy.
Metal design and installation methodologies also do not take into consideration the fact that plastic piping systems are dynamic, and that plastic expands and contracts at a greater rate (10 times faster) than metal. Plastic pipe expands and contracts from temperature changes in the ambient environment, and from the media being conveyed. There may also be significant expansion or contraction due to temperature differences between time of installation - when the pipe gets clamped in place -and when the system actually starts operating. In process heating applications, for example, a 100-foot straight run of plastic PVDF pipe installed on a cool (50°F) morning, will expand 2.88 inches in length when the media temperature in the pipe runs at 80°F. All these factors must be taken into account for proper installation.
Traditional pipe and valve support products for even plastic piping systems create problems of their own:
- Many clamps designed to hold pipe firmly allow the installer to “overtighten” against the pipe. This can stress the pipe at time of installation, and later when it needs to move naturally.
- Clamps with sharp metal edges can damage the pipe.
- Traditional pipe guides that allow movement do not provide enough support during an earthquake. Pipes that can move freely from side to side (perpendicular to the axis) can become damaged.Engineers need to consider the supporting structure beneath the pipe guide if large forces aretransferred during an earthquake.
- Valve manufacturers usually recommend that valves be independently supported in a piping system.In practice, installers often clamp valves down as fixed points creating concentrated stresses \\when the pipe cannott move naturally.
All of these issues contribute to stress concentrations that increase the risk of premature failures and leaks.