APPLICATION OF THE LAWS OF HYDROSTATICS 23
the masonry gas uptake with an average temperature of 600°,
thence into a long horizontal main constructed of steel plates,
where its temperature drops to approximately 300°. The gas then
flows down a vertical gas downtake to the underground gas flue,
which it reaches with a temperature of 200°.
Assuming that the height of the masonry gas uptake is 9 m
above the grate of the producer and that the producer gas has a
weight of 1 kg 07 per cubic meter at 0°, the hydrostatic pressure
of the gas at the top of the uptake will be
$coo = 9 1 . 29 ~Tinr) = 8 mm 64 of water.
\ -L T~ YY 3V
The average temperature of the gases in the downtake will be
In order to force the hot gas down through the vertical downtake
there must be an initial pressure at the head of the downtake
sufficient to overcome the hydrostatic pressure of the gases in
the downtake with an average temperature of 250°.
The resistance due to the hydrostatic pressure in the downtake
5250 = 9 (l . 29 - ^~^} = 6 mm 57 of water.
According to the foregoing the hydrostatic pressure of the gas
within the underground flue will be equal to
d= 5Goo--525o = 8. 64-6.57= +2 mm 07 of water.
As the frictional resistance of the gas mains and flues to the
passage of the gas is generally less than 2 mm 07 of water, the
Siemens " siphon " favors the " draft " of the gas producer. It is
evident that the draft on the gas producer would be stronger if
the length of the conduit were increased, as in this case the drop
in temperature in the horizontal section would be greater.
The position of the horizontal gas main, at a considerable
height above the grate of the gas producer, assures a pressure in
the main somewhat higher than that of the atmosphere, and this
constitutes a guarantee against the risk of explosions with gas
producers operating without forced draft. On the contrary, a