Quick Check on Piping Flexibility

L. C. Peng, PE
Peng Engineering, Houston, Texas

One major requirement in piping design is to provide adequate flexibility
for absorbing the thermal expansion of the pipe. However,
due to lack of quick method of checking, piping are often laid-out
to be either too stiff or too flexible. In either case, valuable
time and material are wasted. This paper presents some of the quick
methods for checking piping flexibility. These methods include
visual, hand calculation, and micro computer approaches. They are
all quick and easy for designers to use in planning their layouts.
Once the designers have taken care of the flexibility problem, the
iterative procedure between the stress engineers and the designers
become simpler. The project schedule can also be improved.

PIPING FLEXIBILITY

As the pipe temperature changes from the installation condition to
the operating condition, it expands or contracts. In the general
term, both expansion and contraction are called thermal expansion.
When a pipe expands it has the potential of generating enormous
force and stress in the system. However, if the piping is flexible
enough, the expansion can be absorbed without creating undue force
or stress. Providing the proper flexibility is one of the major
tasks in the design of piping system.
Piping is used to convey a certain amount of fluid from one
point to another. It is obvious that the shorter the pipe is used
the lesser the capital expenditure is required. The long pipe may
also generate excessive pressure drop making it unsuitable for the
proper operation. However, the direct shortest layout generally is
not acceptable for absorbing the thermal expansion.

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