This type of apparatus has the defect characteristic of
A^2, Fig. 1; for the pressure in the service steadily diminishes as the
effective weight of bell plus hopper decreases by consumption of carbide.
But it has also two other defects--(1) that ordinary carbide is too
irregular in shape to fall smoothly through the narrow annular space
between the valve and its seat; (2) that water vapour penetrates into the
hopper, and liberates some gas there, while it attacks the lumps of
carbide at the orifice, producing dust or causing them to stick together,
and thus rendering the action of the feed worse than ever. Most of these
defects can be avoided by using granulated carbide, which is more uniform
in size and shape, or by employing a granulated and "treated" carbide
which has been dipped in some non-aqueous liquid to make it less
susceptible to the action of moisture. Both these plans, however, are
expensive to adopt; first, because of the actual cost of granulating or
"treating" the carbide; secondly, because the carbide deteriorates in
gas-making capacity by its inevitable exposure to air during the
granulating or "treating" process. The defects of irregularity of
pressure and possible waste of gas by evolution in the hopper may be
overcome by disposing the parts somewhat differently; making the holder
an annulus round the hopper, or making it cylindrical with the hopper
inside.
Pages:
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199