Processing, July 2018

Special Section Piping EXTEND industrial piping service life An improved pipe and valve support system reduces the risk of premature failure By Alphonse Anderson GF Piping Systems ost 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 288 inches in length when the ambient temperature rises to 80 F Issues with traditional clamps supports Issues can arise when using traditional pipe and valve support products for plastic piping systems First many clamps are designed to hold the pipe firmly or do not prevent an installer from overtightening against the pipe This can stress the pipe at time of installation and later when it needs to move naturally see Figure 2 Second many clamps have sharp metal edges that can easily come in contact with the pipe and cause damage Third traditional pipe guides which do allow movement do not provide proper pipe support during an earthquake The pipe can freely move side to side perpendicular to the axis and become damaged This also requires engineers to especially consider the supporting structure beneath the pipe guide because of large forces that would be transferred during an earthquake Finally valve manufacturers typically recommend that valves are independently supported in a piping system in practice installers often clamp them down as fixed points The valves then become unintentional fixed points where stresses will concentrate when the pipe cannot move naturally All of these issues contribute to stress concentrations that increase the risk of premature failures and leaks Solution Improper piping system support can result in premature failures and subsequent damage leading to leaks and expensive downtime for repairs or replacement New solutions are available to resolve this such as a pipe and valve support system that has been especially designed to eliminate the stress transfer to pipe due to thermal expansion installation or seismic events This system see Figure 3 includes pipe guides in sizes inch to 8 inches iron pipe size IPS and metric sizes and valve supports in sizes 38 inch to 2 inches It can be used with any thermoplastic piping system material PP PVDF HDPE PVC CPVC ABS etc as long as it is IPS inch or metric size Pipe guides The pipe guides are designed to have a 3 millimeter mm gap oversized between the plastic insert and the pipe it supports Molded from low friction UV resistant HDPE the design allows the piping to slide easily and freely in the axial direction with absolute minimal stress and wear during each thermal M Figure 1 Thermal expansion plastic versus metal All graphics courtesy of GF Piping Systems Figure 2 Stress concentration from traditional pipe 22 Processing JULY 2018