All About Engines
Forfatter: Edward Cressy
År: 1918
Forlag: Cassell and Company, LTD
Sted: London, New York, Toronto and Melbourne
Sider: 352
UDK: 621 1
With a coloured Frontispiece, and 182 halftone Illustrations and Diagrams.
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94 All About Engines
The case of large pipes or high pressures is met
by the “ double-beat ” or equilibrium valve, shown
in Fig. 49. Here one passage ends in a sort of blind
alley, except for an opening top and bottom. There
are two valves on the same spindle, the lower one
being a little smaller than the other to enable it to
be put in from the top. Since steam, passing from
the boiler in the direction
Fig. 49.—Double-beat or Fig. 50.—Cornish double-beat
equilibrium valve or crown valve
top of the lower valve and on the bottom of the upper
one, the forces are balanced, or very nearly so. For
the lower valve being slightly smaller than the other,
there is a slight excess of pressure on the lower side
of the upper valve. A still better form is the Cornish
double-beat or crown valve, shown in Fig. 50. Here
there is an opening in the partition between the
two pipes, and a disc a little smaller than this open-
ing is fixed, by means of a sort of claw stand, above