THE SUPPLY OR FEED PIPES.
The
water is conveyed in iron feed pipes from the pressure box to the
claim, and by means of iron gates on the lower end of the feed pipes it
is distributed to the discharge pipes. The supply pipe is funnel-shaped
where it connects with the pressure box, and from there on it is
usually of uniform diameter as far as the gate or discharge nozzle.
Where
22 to 30-inch pipes are used it is not advisable to use lighter iron
than No. 14, B. G., even under extremely low heads, as lighter pipe of
that size will not bear handling.
The
main supply pipe should descend in the most convenient and direct line
into the diggings, avoiding, so far as practicable, angles, rises, and
depressions. Air-valves should be arranged at proper distances to allow
the escape of air when filling the pipe, and also to prevent any
collapse. Where the pipe passes over steep banks into the claim it is
carried on a trestle and braced, care being taken to prevent any
movement of the column. When necessary the pipe is secured with
frame-work and weighted with stones. At all angles the pipe is braced
and weighted.
In
filling the supply pipe the water should be turned on gradually, all
sudden straining of the column being thus avoided. Leakage in the slip
joints can be readily stopped with a few bags of sawdust or by wedging
them with thin pieces of soft pine. Large leaks have to be closed by
iron grip-bands drawn together by means of screws or wedges.
The
lower end of the supply pipe was formerly fitted into a distributing
box of cast iron, from which one or more branch pipes were taken by
means of gates. These are now abandoned owing to their great cost and
liability to burst.
The present practice is to fork the main pipe wherever
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