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

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The' following four^ types <strong>of</strong> piping systems<br />

were investigated:<br />

- Steel Pipe in a Concrete Tunnel (350°F Maxiraura<br />

Temperature). This type systera is essentially<br />

a poured-iri-place or precast reinforced concrete<br />

tunnel with removable'concrete lids, which ca'h be<br />

used for sidewalks, and renraved to provide access<br />

for maintenance or insiiallation <strong>of</strong> future p.ipeS;.<br />

The insulated carrier pipes'are supported on steel<br />

rollers which are imbedded into <strong>the</strong> concrete tunnel,<br />

hfter installation, piges are insulated with<br />

preformed fiberglass or rPckwool. Allowance for<br />

expansion is by\a bellows type expansion .joint<br />

which is dual acting with an anchor.between <strong>the</strong> bel-<br />

1 ows. The pipe is al so free to expand at elbows<br />

with <strong>the</strong> use <strong>of</strong> guides. The concrete tunnel is<br />

placed on a gravel bed which contains a dizain tile.<br />

The concrete tunnel is extremely durable, can be<br />

used for o<strong>the</strong>r utilities, arid can be; constructed by<br />

local contractors. Its main drawbaek is that it is<br />

expensive to .construct compai-ed to o<strong>the</strong>r type systems<br />

.<br />

Concrete tunnel type pi pi rig is popular in<br />

European district'heating systeras and <strong>the</strong> Icelanders<br />

who usually use it for pipes larger than 10 inches,<br />

in diameter, -claim <strong>the</strong>re is no better system.<br />

CONCBETE TFffiNirf)<br />

INSULATION<br />

sreeL PIPE<br />

ROLLER PW)<br />

'BACKfiLL<br />

GBAVEL BED<br />

FIGURE 5. Steel Pipe in a Concrete Tunnel<br />

Steel Pipe in a Protective Co.verinn ,(25D°F<br />

Maximum Temperature).- A single carrier pipe- is enclosed<br />

in polyurethah irsulation with a. tight jacket<br />

<strong>of</strong> glassfiber reinforced piasti'c (FRP) <strong>of</strong> PVC.,<br />

Joints <strong>of</strong> pipe are welded, insulated, and sealed<br />

with a joint kit and placgd in a bed <strong>of</strong> sand in <strong>the</strong><br />

CLASS 8 BED<br />

FRP JAGKET<br />

URETHANE INSULATION<br />

STEEL RIPE<br />

FIGURE 6. Steel Pipe in a Protective Covering<br />

trench. Manholes are constructed between anchor's<br />

to house <strong>the</strong>! expansion bel Vows and insulation<br />

around elbows is oversized to allow expansiori.<br />

There are usually eight segments (320. ft) between<br />

an anchor and manhole, <strong>the</strong> manholes are construeted<strong>of</strong><br />

reinforced concrete; with drain provisions, this<br />

type system is very durable, r^esistant to external<br />

corrosion^ however, susceptible to exterior cdrro-<br />

391<br />

Lund j et. al.<br />

sion. Although costs per lineal foot are comparableto<br />

rion-TCtallic pipe, <strong>the</strong> added cost for manholes<br />

arid expansion bellows makes it more expensive.<br />

Fiberglass Reinforced Plastic Pipe (FRP)<br />

(.210°F Maximum temperatureT^ A .single: FRP carrier<br />

pipe is enclosed in polyurethane insulation with a<br />

tight jacket <strong>of</strong> FRP or PVC. The pipe is a filament<br />

wound fiberglass with ei<strong>the</strong>r epOxy or polyester<br />

resin plastic. The epoxy type can handle<br />

temperatures up to 350°F 'a'nd has a low coefficient<br />

<strong>of</strong> roughness, C = 140. The pipe, usually does not<br />

have any expansion joints,, as <strong>the</strong> co.efficient <strong>of</strong><br />

linear expansion is 8.5 x 10^^ per °F as corapared<br />

to 12 X., 10"^ per °F I'or steel pipe. Elbow_s are located<br />

in poured concrete thrust blocks in Order to<br />

hold <strong>the</strong> pipe in, position and allpw expansion in<br />

straight lengths. A polyester resin pipe <strong>of</strong> this<br />

type failed recently when it pulled apart, raairily<br />

,a;t joints, when <strong>the</strong> pipe cooled. There is available<br />

pn <strong>the</strong> market a slip-ring type joint.tha't may<br />

be more desirable than <strong>the</strong> epoxy jpiried pipes. A<br />

check On <strong>the</strong> filament wound epoxy resin pipe installation,<br />

carrying .353°F'water", proved satisfactory,<br />

hov/ever, flashing must never occur in FRP<br />

pipe. In areas wHer^e flashing conditions' are expected,<br />

steel pipe sections must be used. The main<br />

'advantages <strong>of</strong> this type piping systera is its resistance<br />

to corrosion and Tow roughness coefficient.<br />

BACKFILL<br />

FIGURE 7\ Insulated FRP Pipe<br />

CLASS B BE13<br />

PVC JACKET<br />

URETKANE INSULATION<br />

FRP PIPE<br />

Asbestos Cement Pipe (AC) (200°F Maximum<br />

Teraperature). This type.pipe has ^an epcfxy 'lined<br />

AC 'carrier' pipe, polyurethane insulation arid an AC<br />

•^^^

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