Chemical Engineering October 2020 - 26

Cover Story
Pipe Supports:
Challenges and Solutions
Pipe supports in industrial process plants are often more complicated than commonly thought.
Presented here are some of the challenges that can arise and how to address them
Scott Feller
AMG Inc.
IN BRIEF
THERMAL EXPANSION OR
CONTRACTION
PIPE-INDUCED FORCES
ON EQUIPMENT
ANCHORS, GUIDES AND
SLIDES
PRACTICAL PIPE
SUPPORTS
O
n one level, the topic of pipe
supports seems like it should be
simple: support the pipe. And
sometimes, it is that simple, but
most often, it is not. In industrial processing
plants, regardless of the process or utility,
there are a myriad of considerations when
it comes to pipe supports. Concerns such
as maximum allowable span for stress, deflection,
vibration, harmonics and thermal
growth need to be addressed, as well as
the interaction among the pipe, its supports
and the structures that support those supports.
What happens when pipes of various
materials of construction, with different allowable
stresses, and operating at different
temperatures share a common pipe rack?
When these conditions are thoroughly considered,
proper pipe supports can become
more complicated.
This article discusses various pipe-support
challenges and some ways to overcome those
challenges. It will also point out examples of
supports that are either ineffective in the way
they are utilized, or much more expensive to
install than a simpler approach would be.
Thermal expansion or contraction
Situations involving thermal expansion and
contractions of piping are very common
in steam and condensate systems, chilled
water and cryogenic applications, and in
many other process-piping systems. These
pipe runs can present multiple challenges,
including high anchor loads, nozzle loads on
equipment, expansion-loop geometry, or expansion
joint selection and placement. The
trick is to choose the anchor points wisely.
Often, it is necessary to create anchors close
to (within 20 feet or so) connecting equipment,
such as tanks or pumps, so that the
thermal expansion or contraction between
the anchor and the equipment can be minimized
and more easily controlled with supports,
flexible legs, flex joints, springs and
so on. The longer runs between these end
anchors can be challenging, particularly in
26
Pipe anchor
Exaggerated deflected
shape
Pipe slides
Part 2
Pipe slides
Pipe guide
Pipe anchor
FIGURE 1. Long pipe runs can be complicated by thermal expansion
and contraction, and the distances must be determined
congested pipe racks. If expansion loops are
necessary, they may block the routing of adjacent
lines. Using an up-and-over loop may
solve that problem, but might also prevent
pipe drainage, require additional steam traps
or interfere with other piping, ductwork or
electrical runs above. Linear or axial expansion
joints might be an option, but care must
be taken to address the pressure-induced
thrust that might occur. Pressure-balanced
(or compensated) expansion joints are a
good option, but can be expensive. Ideally,
if the pipe run has changes in direction, they
can be utilized as flexible legs to allow growth
or contraction, as illustrated in Figure 1. The
expansion or contraction distance must be
determined to properly space adjacent pipes.
Pipe-induced forces on equipment
Process equipment, particularly devices with
rotating components, such as pumps and
compressors, are sensitive to forces applied
by piping. Reduced seal life and premature
bearing wear can result from large forces
applied to nozzles. Atmospheric tanks and
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