Page 18 - COMSOL_News_2016
P. 18


Improving Gas Pipeline
Squeeze-O Standards
with Numerical Simulation

In order to reduce the challenges associated with everyday gas pipeline maintenance,
Gas Technology Institute (GTI) uses simulation-driven engineering to propose revisions
to the ASTM squeeze-off standards.


Routine natural gas maintenance                                                     Coupling
procedures often require digging
into main roads, forcing drivers to        Squeeze-off tool  Prescribed distance
navigate through a complex series of                         between fitting and
detours and backroads. But what if the                       tool
process of repairing and replacing gas
pipelines could be more ef cient and       FIGURE 1. A polyethylene gas pipeline undergoing a squeeze-off procedure.
less invasive? Gas Technology Institute
(GTI), a leader in natural gas research,   To avoid damage and malfunction,        This rule was put in place to avoid
development, and training, aimed to
investigate the industry standards for     there are certain standards, such as the strain and breakage in pipes. However,
squeeze-off length in gas pipelines in an
effort to make the pipes                   ones published by the American Society a number of gas utilities are interested
more accessible.
                                           for Testing and Materials (ASTM), which in shortening the minimum required
SQUEEZE OFF?                               must be met during the squeeze-off      distance. The twelve-inch distance

Illinois-based GTI is a research and       procedure. One particular standard      requirement is high for most pipelines
development organization committed
to the advancement of new energy           involves the location of the squeeze-off (the majority of pipes used in housing
and natural gas technologies. One
sector of their research involves the                                                                                 and commercial
investigation of squeeze-off distances
for polyethylene (PE) gas pipelines.       “[We] trust the finite element method                                      applications are
Squeeze-off is a seemingly simple                                                                                     2.375 inches
procedure that involves compressing         implementation in COMSOL for                                              in diameter or
a pipe to completely stop the ow of        getting good results as proven by
gas (see Figure 1). This is commonly                                                                                  smaller). This
performed for maintenance tasks and        previous testing.”                                                         means that
to replace sections of pipe without                                                                                   although the
shutting down the whole system.
                                           — OREN LEVER, PRINCIPAL ENGINEER, ENERGY DELIVERY                          three-diameter
   After squeeze-off is completed, the
pipe recovers much of its original shape,  & UTILIZATION, GAS TECHNOLOGY INSTITUTE                                    distance would
allowing gas ow to resume. There are
natural bene ts to polyethylene as a                                                                                  be seven inches,
pipe material: its exibility and ability
to undergo large deformations; the         relative to pipe ttings. The standard   the squeeze-off still has to be performed
absence of corrosion; its fusable and
homogenous nature; and its resistance      states that squeeze-off must be at a    at the greater distance of twelve inches.
to harsh environmental conditions.
                                           distance of either the length of three  The large length requirement for the

                                           pipe diameters or twelve inches from    small pipe diameters leads to more

                                           the next pipe tting, whichever          digging into the ground, rerouted

                                           is greater.                             roads, and more time and money spent.

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