How far apart do the hangers have to be for Installing my PVC pipe?

Hanger & Support for SCH40 and SCH80 PVC and CPVC pipe

Hanger Support Spacing

Proper support selection and spacing is critical to prevent stress concentration areas due to weight loading, bending stress, thermal expansion/contraction effects, and to limit pipe displacement (sag). As with all thermoplastic materials, proper pipe support spacing depends on pipe size, the locations and magnitude of any concentrated weight loads, and the operating temperatures of the system due to the effects that temperature has on the tensile and compressive strength of the material. Temperature increases require additional support. When operating at or near the maximum recommended temperature limits, providing continuous support for the system via a structural angle or channel free from rough or sharp edges may be more economical. Local building codes should also be consulted for applicable requirements before installation.

Proper support spacing can be calculated similarly to metallic systems using simple and continuous beam calculations. This can be achieved using the maximum fiber stress of the material or deflection based on the long-term modulus of the material at the temperature selected as the limiting factor.

Hanger Selection

Many hangers designed for metallic pipe are suitable for thermoplastics; however, hangers and supports must provide an adequate load-bearing surface that is smooth and free of rough or sharp edges that could damage the pipe. The use of improper supports can generate excessive sag resulting in failure. The movement caused by the effects of expansion and contraction of the system due to temperature variations and movement as the result of pressure fluctuations must be considered to ensure proper hanger selection and placement. Hangers and supports used must permit axial movement of the system; they should not compress the pipe or otherwise restrict this movement.

Placement

Common practice is to install suitable hangers within two feet (2 ft) of each side of a pipe joint; changes in direction should be supported as close as possible to the fitting to reduce tensional stress. Heavy system components such as valves, flanged assemblies, tees, and other concentrated stress loads must be independently supported. In addition, valves should be braced adequately to prevent movement/stress loads due to operational torque. Consideration should also be given to certain processes where solids accumulation within the line is possible.

Precautions

The use of protective sleeves or pads between the pipe and the hanger may be desirable in certain applications, as their use will distribute stress loads over a greater surface area, particularly when using U-bolt and roller-type hangers. Piping should not be permitted to contact abrasive surfaces that could cause damage during axial movement of the system. Protective sleeves or pads should be used when a horizontal pipe rests on concrete or other abrasive support structures. Contact with localized heat-producing sources must also be avoided. Plastic piping systems shall not be installed near steam lines or other high-temperature equipment without providing appropriate protection to prevent damage from distortion or forces generated by the effects of expansion or contraction.

Vertical lines must be supported properly at intervals that prevent excessive loading on the fitting at the lower end. Hangers and clamps suitable for this purpose include riser clamps or double bolt-type clamps installed to allow for pipe movement due to thermal expansion and contraction. Clamps and hangers must not compress, distort, cut, or rub the piping. Common practice is to install clamps just below a coupling so that the shoulder of the coupling rests on the clamp. Fittings can be modified in the field to achieve this by cutting a coupling in two, just above the stop at the socket bottom, and then cut this piece in half lengthwise to provide two halves that do not contain the stop. Then two ends are solvent-cemented to the pipe at the proper location so that the shoulder of the modified coupling rests on the clamp. Clamps must not exert compressive stresses on the pipe; using riser clamps that utilize compression to support the pipe weight is not recommended.

Anchor Guides

Anchors are utilized to direct the movement of the piping by providing restraint at key points in the system. Their use may be required to control the effects of movement caused by expansion and contraction, forces generated by pressure surges, vibration, and other transient conditions. Anchors and guides are typically installed on long straight runs, at changes in the direction of the system, and where expansion joints and other thermal compensation methods are utilized. Guides are necessary to help direct this movement between anchors by allowing longitudinal movement while restricting lateral movement. Since guides act as supports, they should have the same load-bearing surface and other requirements of hangers designed for the system. Guides must be rigidly attached to the structure to prevent lateral movement but should not restrict longitudinal movement of the pipe through the guide. Anchors and guides must be engineered and installed in such a manner as to perform adequately without point-loading the system. For additional information, reference should be made to the section concerning thermal expansion and contraction.

Hanger Support Recommendations

Horizontal pipe system support spacing is greatly influenced by operating temperature. The charts show the recommended support spacing according to size, Schedule, and operating temperature. Do not clamp supports tightly – this restricts the axial movement of the pipe. If the short spacing is necessary, continuous supports may be more economical. Charts are based on liquids up to 1.00 specific gravity but do not include concentrated loads or allowance for aggressive reagents.

The following hanger supports spacing recommendations that are considered conservative and based on straight runs of un-insulated lines with the fluid being conveyed with a specific gravity of 1.00 or less. These values do not consider concentrated weight loads or aggressive reagents.

Support Spacing Chart for Harvel Plastics, Inc. PVC Pipe

PVC Pipe Support Spacing (ft)

Schedule 40

Temperature (°F)

Schedule 80
Temperature (°F)

Note: Although support spacing is shown at 140°F, consideration should be given to the use of CPVC or continuous support above 120°F. The possibility of temperature overrides beyond regular working temperatures and cost may make either of the alternatives more desirable. This chart based on continuous span and for un-insulated line carrying fluids of specific gravity up to 1.00.

CPVC Pipe Support Spacing (ft)

Schedule 40

Temperature (°F)

Schedule 80
Temperature (°F)