|
PIPES AND NOZZLES.
|
167
|
||
|
|
|||
|
This sinks and opens when the water leaves it, and floats and shuts when the water rises to it.
The contrivances used on the Virginia City and Gold Hill Water Company's siphon are shown in Figs. 25 and 26.
Fig. 25 shows the blow-off used in every low place (also marked with a triangle in the profile, Fig. 27).
Fig. 26 shows the self-acting air or vacuum valve used at each high point on the line. When the water is on, the valve a is kept open and the valve c closed, while the self-acting valve b is shut by the pressure. If any air accumulates in the pipe it is blown off occasionally by opening the cock, c. Should a break occur in the main pipe-line at a point lower than the air-cock, and within its district, the valve b falls
down and admits the air so as to prevent a vacuum. After a break on the
main line is repaired and the water is let on again, the valve b being down or open, the air rushes out, the valve-stem being weighted, d, so as to close only when the water reaches it.
Preservation against Rust and Accidents.— In
order to protect the pipe it should (as far as possible) be laid in a
trench and covered with earth to a depth of at least one foot for the
ordinary conditions of hydraulic mining.
Wrought-iron
pipes should be treated externally and internally with asphaltum or
coal-tar, the life of a pipe being dependent to a very great extent
upon this bituminous coating, which preserves the iron from rust and
|
|||
|
|
|||