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)
Pipe size 60° 80° 100° 120° 140° 1/4" 4' 3-1/2' 3-1/2' 2' 2' 3/8" 4' 4' 3-1/2' 2-1/2' 2' 1/2" 4-1/2' 4-1/2' 4' 2-1/2' 2-1/2' 3/4" 5' 4-1/2' 4' 2-1/2' 2-1/2' 1" 5-1/2' 5' 4-1/2' 3' 2-1/2' 1-1/4" 5-1/2' 5-1/2' 5' 3' 3' 1-1/2" 6' 5-1/2' 5' 3-1/2' 3' 2" 6' 5-1/2' 5' 3-1/2' 3' 2-1/2" 7' 6-1/2' 6' 4' 3-1/2' 3" 7' 7' 6' 4' 3-1/2' 4" 7-1/2' 7' 6-1/2' 4-1/2' 4' 6" 8-1/2' 8' 7-1/2' 5' 4-1/2' 8" 9' 8-1/2' 8' 5' 4-1/2' 10' 10' 9' 8-1/2' 5-1/2' 5' 12" 11-1/2' 10-1/2' 9-1/2' 6-1/2' 5-1/2' 18" 13' 12' 11' 8' 7' 20" 14' 12-1/2' 11-1/2' 10' 8-1/2' 24" 15' 13' 12-1/2' 11' 9-1/2' 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)
Pipe Size 73° 100° 120° 140° 160° 180° 1/2" 5' 4-1/2' 4-1/2' 4' 2-1/2' 2-1/2' 3/4" 5' 5' 4-1/2' 4' 2-1/2' 2-1/2' 1" 5-1/2' 5-1/2' 5' 4-1/2' 3' 2-1/2' 1-1/4" 5-1/2' 5-1/2' 5-1/2' 5' 3' 3' 1-1/2" 6' 6' 5-1/2' 5' 3-1/2' 3' 2" 6' 6' 5-1/2' 5' 3-1/2' 3' 2-1/2" 7' 7' 6-1/2' 6' 3-1/2' 3-1/2' 3" 7' 7' 7' 6' 4' 3-1/2' 4" 7-1/2' 7-1/2' 7' 6-1/2' 4-1/2' 4' 6" 8-1/2' 8' 7-1/2' 7' 5' 4-1/2' 8" 9-1/2' 9' 8-1/2' 7-1/2' 5-1/2' 5' 10" 10-1/2' 10' 9-1/2' 8' 6' 5-1/2' 12" 11-1/2' 10-1/2' 10' 8-1/2' 6-1/2' 6' 14" 12' 11' 10' 9' 8' 6' 16" 13' 12' 11' 9-1/2' 8-1/2" 7'Schedule 80
Temperature (°F)
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Pipe Support Spacing
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(Structural)
(OP)
8 Jun 10 16:35We have a project where we need to provide frames to support some 8" and 12" schedule 40 pipes. Based on the existing framing I want to install the frames at 15'-6"o.c.. The pipes can easily span the distance, but I believe there is a code requirement on spacing of supports. The Mech Engineer on the project claims there are no such rules. Anybody know what the requirements are, if any? thanks
(Structural)
8 Jun 10 19:40For industrial applications with steel pipe, unless piping codes have changed (on this subject) in recent years, there are NO specified pipe support spacings. This is because there are so many factors, such as the location and rating of valves, fittings, pipe wall schedule, etc., that any "required" span could be either too long or too short, depending on the details.The pipe installation companies, such as Grinnell, have long published technical books and (voluntary) guidelines on the subject. To quote from page 158 of "Piping Design and Engineering", Fifth Edition (1976) by ITT Grinnell Industrial Piping, Inc:"No firm rules or limits exist which will positively fix the location of each support on a piping system. Instead, the engineer must exercise his own judgment in each case to determine the appropriate hanger location."
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(Structural)
8 Jun 10 23:30typical pipe rack has 20 ft distance between bents..
so 15'-6" is more than ok.. 8" dia pipe can span more than that..
dont step on other disciplines scope of work.. pipe stress/design will tell you if support distance is too long..
(Structural)
(OP)
9 Jun 10 09:21Thanks sliderule and westheimer. The mech eng doesn't want anything to do with the support racks, so came to us. I just looked at gravity load stresses (plus some thermal changes) in the pipe (with water) and things looked fine at 15'6, just could have sworn there were rules.
(Structural)
9 Jun 10 11:15You don't state what the pipes will be carrying, if it's a pressure pipe or gravity flow or an interior or exterior installation.
westminster 1234's comments about other disciplines scope is good advice particularly about the pipe stress, so don't indirectly assume that responsibility. Ditto on Sliderule Era's comments, my copy of Grinnell is the catalog PHDE-96. ASHRAE & ASME both address "supporting elements" requirements. ASME B31.1 table 121.5 lists "Suggested Pipe Support Spacing" for water or steam-gas-air service. For water service, it lists 19' for 8" pipe, and 23' for 12" pipe.
Normally what dictates support location is allowable deflection and concentrated loads (valve banks). In some applications, seriously bad things can happen if liquid ponds in a pipe. Ammonia refrigeration piping supports were 7' centers based on ANSI/IIAR requirements. Steam piping is another animal all to itself, so don't go there unless you've done it before. Generally for exterior applications the pipe has sufficient lateral rigidity from bends, valve banks and headers that the pipe actually supports the stands. What I was taught is standard practice is to assume the pipes are full of water when designing the pipe stands, and empty when for wind loads. Of course you have know if that would adequate for your application. ASCE 7.15 addresses requirements for seismic piping attachments. If I recall correctly from the Grinnell catalog, recommended maximum movement for pipe hangers, parallel to the pipe, is 7 degrees, but that needs to be verified. For gravity piping, the stands need to accommodate post construction adjustments.
For trapeze type stands, don't forget to check the deflection of the horizontal support.
(Structural)
9 Jun 10 11:29I found it, recommended movement for rod hanger is 4 degrees.
(Structural)
9 Jun 10 11:58In short, the span of the pipe has to come into play in the design of the pipe --> meaning the support spacing should be given to you by the pipe designer.
(Structural)
9 Jun 10 12:54MSS SP 58 is another often quoted reference. It has several tables of maximum recommended support spacings.
(Structural)
9 Jun 10 13:04I deal with this all the time. I typically set my spans based on the following:
1. Assume pipe to be uniformly loaded simple beam.
2. Limit the allowable stress that the pipe would see due to its own dead weight, including fluid (or hydrostatic test conditions where applicable) and insulation to one half of the maximum allowable stress [fb = 0.5Fb]. From this you can get your allowable span.
3. Find maximum deflection [y = (5wL^4)/384EI]. Limit the deflection to 1/4 of the nominal pipe size or 1 inch, whichever is less.
4. The max span should be the lesser value obtained from Step 2 and Step 3.
Note that these steps do not account for any valves (or any other concentrated loads, for that matter) or thermal expansion. For thermal expansion I always refer to our pipe stress engineer and/or pipe stress analysis reports.
Now, to answer your question, I have never seen anything limiting the spans of supports other than the calculations I listed above. (FYI, most of my work is pertains to industrial sites.)
(Structural)
9 Jun 10 13:05If any of you want, I can forward on a spreadsheet I developed that gives me max spans. Let me know if you do and I'll post it.
(Structural)
(OP)
9 Jun 10 13:23Thanks for all the responses. There are (2)12"(hot water) and (2)8" (cold water) pipes supported on frames bolted to a concrete wall at 10'o.c.. We need to move the pipes off the wall in a couple of places to allow for some other work. All the valves and such are still mounted to the concrete wall so we just need to support the pipes/water/insulation. I did calcs similar to aswierski described and things work fine at 15'(15'-6 in my original post was a typo, the floor framing is spaced at 7'-6"o.c.). It is just a lot more work to put the frames in at 7'-6".
Thanks all
(Structural)
9 Jun 10 18:00Any closer together it will be more efficient to put them twice as far apart and run beams between the supports.
I like greater spacing and beams running bewteen supports for several reasons:
- You can add intermediate members when they need to run a small line (such as a condensate line or electrical conduit).
- The beams help with stability bewteen supports and you might not nned to consider the columns cantilevered.
- Fewer foundations.
(Mechanical)
9 Jun 10 22:31We had a project long ago where we had some 18" pipes vertically unsupported for about 75'. They met all the stress criteria that way, but were vibrating in the wind, which was something we hadn't thought of. I doubt this would happen if the pipe was normally full, but something to consider otherwise.
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