TM 5-814-2/AFM 88-11, Vol. 2
improperly or subjected to high temperature wastes, and
b. Surge control valves. To protect pumps and
chemical breakdown caused by prolonged exposure to
piping from surges caused by pump shutdown or power
sunlight. The following types of plastic pipe are suitable
failure, gravity operated swing check or ball check
for use:
valves, or automatically operated cone, plug, ball or
(1) Polyvinyl chloride (PVC). PVC pipe is
butterfly valves will be installed in the pump discharge
available in diameters 4-inch through 12-inch, and with
line. The operation of surge control valves is discussed
screw, push-on, or solvent weld joints.
(2) Polyethylene (PE). PE pipe may be used
c. Blowoff valves. A valve outlet installed at the
in diameters 11/2-inch through 48-inch. Pipe joints
low point in a force main, and arranged to drain or flush
consist of mechanical, flanged, or heat fusion type.
the pipeline, is termed a blowoff. Normally, blowoffs will
(3) Polypropylene (PP).
Pipe diameters
be required only on long depressed sections of force
available with polypropylene pipe are 1/2-inch through
main, or where an accumulation of solids is likely to
4-inch. All pipe will be joined by heat fusion methods.
occur. Blowoff connections will be installed in manholes
Screwed and flanged joint pipe will not be used
or valve structures, and will be protected against
underground. Manufacturer's recommendations will be
freezing. A means of discharging to a suitable location
used in design of plastic pipe, in addition to the
materials flushed from the system will be provided. The
Handbook of PVC Pipe-Design and Construction
pipe size of the outlet connection should coincide with
published by the Uni-Bell Plastic Pipe Association.
the size of the force main.
g. Fiberglass. Fiberglass pipe provides a good
d. Air valves. Air valves will be installed at high
alternative for use in large diameter force mains. High
points in force mains for the purpose of admitting and
structural integrity, low pipe friction coefficient, and a
releasing air. When the pipeline is taken out of service
high resistance to internal/external corrosion and to high
for draining, flushing and filling operations, a manually
temperature wastes, are important properties of
operated valve will be adequate. However, where air
fiberglass pipe. The following types of fiberglass pipe
pockets or pressures less than atmospheric are likely to
may be used:
occur with the pipeline in service and under pressure,
(1) Reinforced thermosetting resin pipe
automatic air release and/or air vacuum valves will be
(RTRP). RTRP pipe may be installed in diameters of
used. Manual valves can also be used with the pipeline
6inch through 144-inch. Jointing systems for RTRP pipe
under pressure by leaving the valve partially open.
include bell and spigot, flanged, or special mechanical
Automatic valves are not recommended due to
type couplings. Elastomeric gaskets are used to provide
maintenance problems, and should be used only where
flexible joints.
absolutely required. Automatic valves will be of a type
(2) Reinforced plastic mortar pipe (RPMP).
specially designed for sewage, and will be provided with
Pipe diameters available for RPMP pipe range from 8-
backflushing connections. All valves will be installed in
inch to 144-inch. Pipe joints are made with grooved
a manhole or valve structure with adequate drainage
couplings or bell and spigot joints utilizing rubber
and protection against freezing.
gaskets. Design of fiberglass force mains will follow the
manufacturer's recommendations.
6-3.
Installation
h. Interior piping. Pump suction and discharge
a. Structural design. Structural design of force
piping inside the station will normally be ductible iron or
mains will be in accordance with the requirements set
steel. However, other pipe materials covered in this
forth for sewers in chapter 5 of TM 5-811/AFM 88-11,
paragraph are not precluded from use. Pipe, fittings and
Vol. 1.
joints serving as force mains will be selected to
b. Thrust restraint. Force mains will be restrained
withstand the maximum internal operating pressures,
to resist thrusts that develop at bends, tees, wye
including transient surges, as determined in chapter 5.
connections and plugs in the pipe. The magnitude of
The project specifications will indicate the appropriate
such forces can be calculated with the use of formulas
pressure class and rating for each pipe application.
found in standard hydraulics textbooks.
Required
methods of restraint will consist of tie rods and clamps,
Valves and appurtenances. The use of valves
or concrete thrust blocks, and will be designed in
6-2.
in wastewater pumping can be divided into the following
accordance with Section VI of the CIPRA Handbook of
categories:
Ductile Iron Pipe, Cast Iron Pipe.
a. Isolation or shutoff valves. Where the need to
c. Depth of cover. Force mains will be installed
isolate pumps or part of the piping system occurs,
with sufficient depth to prevent freezing, and to protect
manually operated shutoff valves will be used. Gate
the pipe from structural damage. A minimum
valves or butterfly valves generally serve as shutoff
valves, however ball valves or plug valves may also be
used. Shutoff valves are required on the suction and
discharge sides of all pumps.
6-2
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