Figure I Generalized map of the Wilbur Mining ... - University of Utah

The' following four^ types of piping systems
were investigated:
- Steel Pipe in a Concrete Tunnel (350°F Maxiraura
Temperature). This type systera is essentially
a poured-iri-place or precast reinforced concrete
tunnel with removable'concrete lids, which ca'h be
used for sidewalks, and renraved to provide access
for maintenance or insiiallation of future p.ipeS;.
The insulated carrier pipes'are supported on steel
rollers which are imbedded into the concrete tunnel,
hfter installation, piges are insulated with
preformed fiberglass or rPckwool. Allowance for
expansion is by\a bellows type expansion .joint
which is dual acting with an anchor.between the bel-
1 ows. The pipe is al so free to expand at elbows
with the use of guides. The concrete tunnel is
placed on a gravel bed which contains a dizain tile.
The concrete tunnel is extremely durable, can be
used for other utilities, arid can be; constructed by
local contractors. Its main drawbaek is that it is
expensive to .construct compai-ed to other type systems
.
Concrete tunnel type pi pi rig is popular in
European district'heating systeras and the Icelanders
who usually use it for pipes larger than 10 inches,
in diameter, -claim there is no better system.
CONCBETE TFffiNirf)
INSULATION
sreeL PIPE
ROLLER PW)
'BACKfiLL
GBAVEL BED
FIGURE 5. Steel Pipe in a Concrete Tunnel
Steel Pipe in a Protective Co.verinn ,(25D°F
Maximum Temperature).- A single carrier pipe- is enclosed
in polyurethah irsulation with a. tight jacket
of glassfiber reinforced piasti'c (FRP) of PVC.,
Joints of pipe are welded, insulated, and sealed
with a joint kit and placgd in a bed of sand in the
CLASS 8 BED
FRP JAGKET
URETHANE INSULATION
STEEL RIPE
FIGURE 6. Steel Pipe in a Protective Covering
trench. Manholes are constructed between anchor's
to house the! expansion bel Vows and insulation
around elbows is oversized to allow expansiori.
There are usually eight segments (320. ft) between
an anchor and manhole, the manholes are construetedof
reinforced concrete; with drain provisions, this
type system is very durable, r^esistant to external
corrosion^ however, susceptible to exterior cdrro-
391
Lund j et. al.
sion. Although costs per lineal foot are comparableto
rion-TCtallic pipe, the added cost for manholes
arid expansion bellows makes it more expensive.
Fiberglass Reinforced Plastic Pipe (FRP)
(.210°F Maximum temperatureT^ A .single: FRP carrier
pipe is enclosed in polyurethane insulation with a
tight jacket of FRP or PVC. The pipe is a filament
wound fiberglass with either epOxy or polyester
resin plastic. The epoxy type can handle
temperatures up to 350°F 'a'nd has a low coefficient
of roughness, C = 140. The pipe, usually does not
have any expansion joints,, as the co.efficient of
linear expansion is 8.5 x 10^^ per °F as corapared
to 12 X., 10"^ per °F I'or steel pipe. Elbow_s are located
in poured concrete thrust blocks in Order to
hold the pipe in, position and allpw expansion in
straight lengths. A polyester resin pipe of this
type failed recently when it pulled apart, raairily
,a;t joints, when the pipe cooled. There is available
pn the market a slip-ring type joint.tha't may
be more desirable than the epoxy jpiried pipes. A
check On the filament wound epoxy resin pipe installation,
carrying .353°F'water", proved satisfactory,
hov/ever, flashing must never occur in FRP
pipe. In areas wHer^e flashing conditions' are expected,
steel pipe sections must be used. The main
'advantages of this type piping systera is its resistance
to corrosion and Tow roughness coefficient.
BACKFILL
FIGURE 7\ Insulated FRP Pipe
CLASS B BE13
PVC JACKET
URETKANE INSULATION
FRP PIPE
Asbestos Cement Pipe (AC) (200°F Maximum
Teraperature). This type.pipe has ^an epcfxy 'lined
AC 'carrier' pipe, polyurethane insulation arid an AC
•^^^