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technical data
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PIPE SUPPORT
Considerations for the Hanging or Supporting of Grooved Piping Systems
Grooved piping products have a very good maintenance track
record out in the feld. Whenever there is a “perceived” problem
with installed grooved product, a high percentage are often
related to the hanging or supporting method or application
chosen. Although supported very similarly to welded piping
systems, a few considerations should be given to assure the
proper selection and application of hangers and supports used
on a grooved piping system such as Anvil’s Gruvlok® brand.
REVIEW REQUIREMENTS AND LOGISTICS
A variety of hangers and supports are typically used on grooved
piping systems, ranging from a simple band hanger, clevis hanger,
and trapeze supports to more intricate rack designs using
structural steel or a mechanical framing/strut system. All of these
are acceptable hanging or supporting methods but they are
dependent on the project’s type, design and specifcation
requirements. With this in mind, a vital frst step is to refer to the
project and code requirements when choosing the proper
hanging or supporting method.
Project logistics is another consideration regardless of system
type. Quite often hangers and supports are an after thought on
a project simply because the big-ticket items, such as labor, major
equipment and schedule, are the focus of the project team.
However, hangers and supports are one of the frst components
needed on a project since you cannot hang pipe without them.
In nearly every hanger or support assembly there are three
components that make up the assembly. These components
are an upper attachment (beam or structural attachment),
intermediate attachment (rod, couplings, eye nuts, etc.) and the
lower attachment (pipe clamps, U-bolts, trapezes). See accom-
panying illustrations for examples of typical assemblies. All
three components should arrive on the project site together and
early. To save costly feld labor hours, consideration might be
given to having the hangers or supports pre-assembled by the
manufacturer or fabricated in the contractor’s shop. Compo-
nents can also be bundled and tagged by system or area of the
project so they can be easily assembled and located on-site.
MAKE A MATCH
The type of grooved coupling used on a project is the next
consideration to choosing the correct hanger or support method.
The proper maximum spacing allowables governed by project
specifcations, the applicable code and/or the hanger manufac-
turer’s recommendations all must also be reviewed. Flexible
couplings used on horizontal runs of pipe need to be supported
at every coupling and usually require intermediate supports to
satisfy the maximum spacing allowable requirements. Rigid
couplings, on the other hand, can be hung or supported based on
the maximum spacing requirements only. In addition, wherever
there is a change in direction of the piping system a hanger or
support is usually required immediately following that change in
direction and then the system is hung or supported accordingly.
PRESSURE POINT
System pressurization should also be reviewed when choosing the
proper hanging or support method. As the couplings are installed,
the pipe ends can either be butted up tight to one another or a
gap can exist. Once the system is pressurized, those areas or joints
where the pipe ends are butted up tight and held by a grooved
coupling can “pop” or grow to the maximum gap depending on
the coupling chosen. The joint at a fexible grooved coupling can
expand about 1/4" at each coupling whereas the joint at a rigid
grooved coupling can grow about 3/32". If there is a long run of
horizontal or vertical pipe with multiple joints the overall length
of the system will grow depending upon which grooved coupling
you have chosen.
For example, if you have a grooved piping system that is 400 ft.
long there will be roughly 19 grooved joints (assuming 21 ft. lengths
of pipe are used). If you multiply the number of joints by the
growth of each joint you can determine the overall growth of
the system due to pressurization. If it is a fexible system, 19
joints x .25" = 4.75" of overall growth. A rigid system would be
19 joints x .0938" = 1.78" of overall growth.
As one can see, this growth due to pressurization can have a
signifcant impact on the hangers or supports used on a project.
One way to avoid this growth is to install the grooved joints at
full gap so that pressurization has no impact at testing or start
up. If this is not possible, then periodic air pressurization as the
system is installed will expand the grooved joints to full gap
and the hangers or supports can be adjusted accordingly.
HOT AND COLD
Thermal expansion is another important consideration when
choosing hangers or supports for a grooved system. This is
especially important on hot systems versus chilled systems since
the amount of thermal expansion will be greater on hot systems
as opposed to the thermal contraction that will occur on chilled
systems. This is all due to the temperature variation from ambient
conditions when the pipe is installed to operating conditions.
For example, if you again take 400 ft. of grooved piping, let us
assume the system is heating hot water that will operate at 170°F.
The pipe is installed under ambient conditions assumed to be
at 70°F so you have a 100°F variation in temperature. At 70°F the
pipe has a coeffcient of thermal expansion of 0.0 in/ft but at
170°F the pipe has a coeffcient of thermal expansion of 0.0076
in/ft. To determine the total thermal expansion of the pipe from
ambient temperature to operating temperature you multiply the
length of pipe by the coeffcient of thermal expansion. In this
case 400 ft. x 0.0076 in/ft. = 3.04 in. In other words the pipe has
grown in length over 3 inches because of the thermal expansion.
This is signifcant growth especially if there is a change of
direction at the end of the 400 ft. pipe run or there are branch
lines coming off the main run. If this thermal growth exceeds the
allowable defection of a grooved joint, especially where a change
of direction or a branch line connects, then problems could occur.
GL-2.10