J. C. Hoadley & Co.
(Page 7 of 10)
15. To guard against injury to the cylinder or piston,
from overheating, the following apparatus, referred to in Section
11, is introduced.
From the chamber of the slide starting-valve at the base of the
dome, a small pipe extends down nearly to the crown-sheet of the
firebox, so that its lower end is always immersed in the water. A
small cock, inch diameter, is inserted in this pipe, with its plug
parallel to the axis of the boiler; and a rod coupled to this plug
extends through a stuffing-box in the fire-box casing above the
fire-door, and below the rod of the slide starting-valve. A small
handle, like a gimlet handle, on this rod, serves to turn it by,
and to indicate the state of the -inch cock. When the handle is
vertical, the cock is open, and a jet of water forced through the
-inch pipe enters the valve-chamber under the whole difference of
pressure caused by the action of the governor-valve. Entering the
steam-pipe at a higher temperature than that of the steam inside,
it speedily evaporates, so that no water appeared at the cylinder
petcocks when this injection-cock was opened for experiment.
When the handle is horizontal, the cock is shut, and no water
enters the steam-pipe.
*16. With considerable effort, a brisk fire, good draught, and
the engine at rest, the cylinder was in one instance intentionally
heated, in the course of an hour, to such a degree that a squeaking
noise was produced by the friction of the piston on starting.
This noise almost instantly ceased on opening the
injection-cock; and, after keeping it open three or four minutes,
giving time for the current of steam to reduce slightly the
temperature of the cylinder, the engine ran smoothly with the
injection-cock permanently closed.
In this manner, by introducing a slight degree of moisture into
the steam-pipe and cylinder, when required for lubrication,
superheated steam may be safely and conveniently used almost all
the while, and all danger of excessive heating obviated.
17. The steam-gauge (a Bourdon gauge, made by the American
Steam-Gauge Company, Boston), is arranged to indicate either the
pressure in the steam-dome or that in the steam-pipe below the
governor-valve, as required; thus showing at any time the extent of
'throttling' produced by the governor. This is managed by a
two-way cock, admitting steam to the pressure-gauge from either one
of two pipes, one entering the dome and passing down to the
starting valve chamber, and the other opening into the dome
18. The safety-valve is placed at the top of a chamber on
the side of the fire-box casing, and held down by a spiral spring
pressed upon by the base of the whistle, which serves as a
set-screw to regulate the pressure required to lift the
safety-valve. When lifted, the escaping steam blows the whistle. To
blow the whistle, the safety-valve is lifted by the whistle-lever.
To the chamber above mentioned are attached the glass water-gauge,
three gauge-cocks, and the steam-pressure gauge; so that all the
indications required about the state of water and steam in the
boiler are combined in this apparatus, which might be called with
some propriety, a Pantaphane.
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