Evening star., 1898-11-18
ENORMOUS PIPE LINE.
An Australian Water Conduit Over
Three Hundred Miles Long.
From the Engineering News.

rtoLi Cle TbhShfeifhs ->e"s.
The Coolgardie project proposes the de-
livery of five million gallons of water per
day at point in the mining regions of
Australia, 32s miles from the reservoir in
the mountains near the coast, where it is
impounded To force water through pipe
line for this long distance, not only must
its friction be overcome, but it has to be
actually raised total vertical distance of
1,330 feet. Further, the district through
which the pipe line passes is a desert whose
soil is impregnated with salts, which are
said to be SO corrosive to iron that it is
deemed safest not to bury the pipe in the
ground al all.
Another reason for having it exposed is
that in a pipe line of such great length
avoidance of leaks is essential. If an
dinary pipe line leaks a thousandth part of
its flow in a mile the loss may be a trifiing
matter; yet even small a loss in pipe
line of this length would amount to nearly
a third of its flow. In the arid desert
through which this pipe line will pass il is
thought that the soil might absorb small
leaks, SO that they would not show at all
on the surface Of the ground if the pipe
were buried Facility of inspection, there
FORE is another important reason for keep
ing the pipe above ground instead of bury
ing it,
Besides this, the ordinary reasons for
way, and to keep them from freezing in
winter-do not obtain at all in the region
over which this pipe line Will pass; and as
the cost OF eXcaVatlng and back filling a
trench 32S miles long will be saved by plac-
ing the pipe on the surface, the decision
not to bury it seems, on the whole, a wise
one.
The one great difficulty which is involved
in keeping the pipe on the surface is the
cessity of providing for expansion and con-
traction. In an ordinary continuous steel
conduit, buried in the earth in a temperate
climate, the extremes of temperature of the
water passing through it will probably not
exceed 81 degrees.
Turning now TO the Coolgardie conduit, to
be laid unprotected on the surface of the
ground, and with distance between pump
ing stations great seventy-five to
eighty miles, il is evident that the water
confined from evaporation and exposed in
steel pipe to the fierce rays of the Aus
tralian sun may reach very high tempera-
ture in its passage from one pumping sta
tion to the next, which in the case of the
longest conduits will require nearly three
days. The English engineers estimate the
range of temperature which will occur in
the pipe line at 70 degrees. and We should
think this rather an underestimate. 1t will
be seen at once that with such a range Of
temperature internal strains would be set
up in the pipe which might become so great
as to cause movement and leakage at the
circumferential joints.
Expansion joints are, therefore, essential
to the safety of the pipe. and the English
engineers propose that such joints shall be
placed at intervals of about 12O feet for the
whole length of the conduit, which would
make a total of about $1,000 expansion
joints in the length Of the conduit.
The engineering problem presented then
land one which We need hardly say is with
out precedenD is the design of an expan-
sion joint for a pipe of twenty-siX to thirty
one inches diameter, which shall provide
for a motion reaching fve-eighths of an
inch, which shall sustain pressures reach
ing 200 pounds per square inch, which shall
be and remain tight, with little no at
tention, and which shall be nearly as
possible a permanent part Of the pipe line.