TM 5-852-5/AFR 88-19, Volume 5
6-5. Materials.
non-pressure drainage, sewer and vent piping. It is
not recommended for single pipe systems buried in
The basic selection of pipe materials will be in
permafrost areas.
accordance with TM 5-813-5/AFM 88-10, Vol.5.
g. Asbestos-cement (AC). This pipe is relatively
The discussion that follows is intended to give some
inexpensive, light weight, corrosion resistant and
indication of the performance of these materials in
has a smooth interior. However, it is brittle and is
the Arctic and Subarctic.
not suited for buried installations in the Arctic or
a. Copper. Type K copper is commonly used for
Subarctic where differential settlements and frost
service lines because it can be thawed by using
heaving are expected.
electrical resistance while plastic pipes cannot be
h. Others. Reinforced concrete is usually used
thawed in this manner.
for large transmission lines. Wood stave piping has
b. Ductile iron. Ductile iron pipe can take some
been successfully used in the past. It is corrosion
shock loadings and is slightly flexible. It has poor
free, has a smooth interior and can usually be re-
corrosion resistance and lining is necessary. It is a
stored after a freezing event, but cannot be thawed
heavy, durable pipe often used in rocky areas or
electrically.
where adequate pipe bedding materials are not
i. Insulation. Pipe units composed of the mate-
available. Ductile iron pipe with special joints is
rials (except wood and concrete) described above
used where bridge strength is required to span piles
are typically insulated with high density urethane
or where differential settlements are anticipated in
foam at the factory and covered with either a steel
buried systems. It can be thawed with electrical
or a 40-mil high density polyethelene jacket,
resistance.
depending on the final conditions of exposure in the
c. Steel pipe. Steel pipe is lighter, more flexible,
field. Design calculations to determine insulation
and more corrosion resistant than ductile iron. Con-
thickness are described in section 12 (see example in
tinuously welded steel pipe has been used to obtain
para 12-91). These prefabricated pipe units are then
maximum span between piles. It can also be thawed
shipped to the job site with preformed half shells of
using electrical resistance. Expansion and contrac-
urethane insulation for the joints. Heat shrink
tion, including necessary thrust anchors, must be
sleeves or special tape is used to complete the field
considered. The differential expansion and contrac-
joint when PE is used as the outer jacket. Prefabri-
tion between a steel pipe and rigid heat tracing
cated sections are used for steel-jacketed pipes. Pipe
components or insulations attached to the pipe must
insulation is not normally done on-site because of
also be considered.
high costs and labor. Factory prefabrication will
d. High density polyethelene (PE). Pipe of this
usually ensure a better quality insulation. Exceptions
material is very flexible and impact resistant, with a
are appurtenances such as hydrants where foamed-
high coefficient of expansion and contraction, high
in-place urethanes are commonly employed.
corrosion resistance and a smooth interior, but it
cannot be threaded. Butt-fused polyethelene pipe
6-6. Appurtenances.
has been used extensively in Canada for water and
sewer mains. Typically the water pipe is insulated
On typical water distribution system these include
with urethane and then covered with a thin polyeth-
hydrants and valves.
a. Hydrants. Figure 6-9 illustrates the typical
elene jacket. Field joints are insulated and covered
with heat shrink couplings. The most common use
details of a hydrant installed on an above-ground
has been in buried systems, and experience has
water main. The insulated hydrant box must be
shown that the pipe and contained water can freeze
specially designed and fabricated to fit the equip-
solid without breaking the line.
ment to be used and the particular location. The
e. Polyvinyl chloride (PVC). This is the most
riser from the main to the hydrant base will be as
common type of plastic pipe used for water mains.
short as possible so that heat conducted from the
It can be threaded, is corrosion resistant and has a
water flowing in the main can keep the hydrant from
smooth interior but is not as flexible as PE, and may
freezing. A typical hydrant connection to a buried
rupture if pipe and contents freeze. As a result PVC
water main is shown in figure 6-10. The hydrant is
pipe is not the best choice for single pipe systems
normally on-line to minimize the possibility of
buried in permafrost areas.
freezing, with a frost-isolating gasket between the
f. Acrylonrile-butadiene-styrene (ABS). This
hydrant barrel and the tee into the main. The
pipe has a higher impact strength and flexibility but
hydrant barrel is insulated with 3-inch prefabricated
a lower mechanical strength than PVC. It has a
polyurethane inside a polyethelene sleeve. The
smooth interior and does not become brittle at cold
annulus between the sleeve and the insulated barrel
temperatures. ABS pipe has mostly been used for
is filled with an oil and wax mixture to prevent frost
6-6
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