What You Need to Know About Plastic Pipe Installation

Jun 1, 2019 9:00 AM
snake pipeConventional pipe supports are inadequate and can cause premature leaks and pipe failure.

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 problems

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.

GF Stress Less PRFigure 1.

Overcoming traditional problems

To address these problems, a new pipe and valve support system has been especially designed to eliminate stress transfer to plastic pipe due to thermal expansion, installation or seismic events. The system (Figure 1) includes Stress Less® Pipe Guides in sizes ½” to 8” (IPS and metric sizes) and Stress Less® Valve Supports in sizes 3/8” to 2” (IPS and metric sizes). The system 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.

Stress Less® Pipe Guides

Pipe guides in the new system are designed with a 3mm gap (oversized) between the plastic insert and the outer diameter of the pipe it supports.  Molded from low friction, UV-resistant HDPE, this allows the piping to slide easily and freely in the axial direction with absolute minimal stress and wear during each thermal expansion cycle. Additional strength is provided via an outer metal bracket that withstands all operating conditions including strong seismic events. By design, the metal bracket cannot touch the plastic pipe (Figure 2). No matter how hard the installer bolts down the metal bracket, the guide will not squeeze the pipe.

Support with Metal bracketFigure 2.

Stress Less® Valve Supports

The new valve supports allow valves to move in two directions (+/- 3 inches) as the pipe expands and contracts, all in a controlled manner and while properly supported. The support base and slide components are made of low friction, durable PP. Valves can slide with virtually no resistance.  Piping centerlines str aligned when the pipe guide is mounted on standard strut height taller than the valve support.

New installation flexibility

Stress Less Pipe Guides can mount directly on any flat surface, on standard strut, horizontally as a hanger, or vertically.  In vertical orientation, an elastomer material is inserted to create sufficient friction and snugly secure the pipe. In a horizontal mount, the pipe is free to move. A separate hanger kit allows mounting to all thread or rods connected to the ceiling. In all cases, the pipe never touches the metal bracket or hardware. Sizes are embossed and stamped on with IPS inserts in gray and metric inserts in black for easy identification.

Additional installation simplicity is provided with the integrated base supports that come with GF Type 546, 523, 543, and 5-series diaphragm valves. These supports line up directly with the sliding portion of the valve support and the included fastening hardware.. Due to the profile molded underside of the support base, it can be mounted to any flat surface or directly onto standard strut.

The new support system can extend the life of thermoplastic piping systems in both high purity facilities and corrosive environments. Applications with aggressive media, indoor to outdoor transitions, or those subject to wide temperature variations will especially benefit.

For more information on the new Stress Less® Pipe and Valve Support System from GF Piping Systems, visit www.gfps.com,  View Video or call toll-free 1-800-854-4090.