Streamline - Summer 2016 - (Page 36)
When and How to
Use Piping Restraints
Piping restraints play an essential role in ensuring safe water
and wastewater system operations. However, it's important
to evaluate criteria such as local soil conditions, materials,
existing infrastructure, deflection, seismic activity and
cost to determine the most appropriate restraint to use.
BY DOUG RISEDEN
piping stays connected and help prevent costly repairs that can shut down a water or
wastewater system. Mechanical-joint piping connections such as 45s, 90s, end caps, and hydrant connections are common points
of restraint as well as connections within wells, wastewater lift stations and treatment plants.
RESTRAINING TECHNIQUES ENSURE
Restraining inline piping has become
so common that the practice is often a
matter of standard procedure among city
or project engineers. Instead of using
restraints for specific applications,
some engineers use restraints throughout entire systems. Adding restraints
in this manner can be expensive and
increase project costs significantly. It's
worth examining what criteria should
be followed for restraining pipe connections and which techniques to use within
particular conditions and environments.
Criteria for restraining pipe
Although engineers typically decide
when and how to restrain pipes, utility managers can and should be part
of the process. Once a piping system is
A Thrust block
36 S T R E A M L I N E * S u m m e r 2 0 1 6
completed, it's in their hands to ensure
the system works properly and to make
repairs, so it's essential to include their
input. The first things to examine are
the factors that may affect the chances
of pipe movement and separation.
Important criteria to consider include
the nature of the piping system, ground
movement, and other ground stresses.
The nature of the piping system. The
first consideration is the design of the
piping system itself. In a pressurized
buried pipeline, such as a water main
or wastewater force main, axial thrust
forces act on the pipe based on changes
in fluid velocity, pipe size, or pipeline
direction. This generally happens at fittings such as plugs, caps, valves, tees,
bends or reducers. Such hot spots definitely need to be restrained.
Ground movement. Earthquakes
and ground movement can cause connection failure, beam or shear breaks,
and cracks along the length of a pipe.
A region's geographic phenomena can
greatly determine how much the ground
moves. Some regions regularly experience ground movement, whereas others
are relatively stable.
With its location on the San Andreas
Fault, California experiences dramatic
earthquakes, causing the ground to
move suddenly and with great force.
It's no surprise that a high level of
restraint is used on water and sewer
pipes in many areas along the West
Coast. Although other parts of the
country located on major fault lines can
incur less dramatic ground movement,
such movement can still stress water
and wastewater pipelines.
The New Madrid fault line is particularly noteworthy, as it can affect more
than 15 million people in Alabama,
Arkansas, Illinois, Indiana, Kentucky,
Mississippi, Missouri and Tennessee.
The Ramapo Fault runs about 70 miles
through New Jersey, New York and
Pennsylvania. Ground movement caused
by this fault has stressed piping systems
even without full-blown earthquakes.
In addition, scientists have warned of
earthquake risk from hydraulic fracturing operations.
Ground movement can also be caused
by seasonal weather changes, especially during winter and spring. The
ground freezes in the winter, and ice
Table of Contents for the Digital Edition of Streamline - Summer 2016
From the President: Life’s a Dance
From the Executive Director: Drum Roll Please...
VRWA’s 2016 Conference Highlights
VRWA Says “Until We Meet Again
System Efficiency and Production: Time for a Change???
Confessions of the Chronically Late
OSHA’S Recordkeeping Rule
Revenue and Reasonable Rates
When and How to Use Piping Restraints
Retaining Operators: Is it Really Just About $$?
What is WaterPAC?
Note from Myrica Keiser, Executive Director, VRWA
Throwing My Loop: The Secret to Creativity
VRWA Members Corner
Benefits for VRWA Members
Board of Directors
Index to Advertisers/Ad.com
Streamline - Summer 2016