New Orleans daily crescent. [volume] ([New Orleans, La.]) 1851-1866, 1866-05-28

Chat the steam was highly surcharged with heat,
appears by comparing the pressures corresponding
to the temperatures with those given by Dulouy
and Arrays for saturated steam.
The answer to this question is given by the expert.
ments just detailed; and as they established the
negative in relation to the surcharged steam be.
coming saturated, there was no necessity for a
repetition Of the experiments to ascertain the pre-
else temperature Of the water in the boiler. When
the fire was applied to the top Of the boiler the
water within was at 318 fab; moderate fire was
kept up below, and enc SO nearly uniform that
great variations from that temperature could not
have taken place, and which the results satisfac.
torily show did not occur.
comparison of the second and third columns
e of the table y shows that in these experiments,
which lasted more than two hours { each, the
surcharged steam remained in contact with water
without acquiring from it the water necessary to
convert it into saturated steam but retaining its
surcharged state. There is nothing to warrant
the belief that any Of the surcharged steam was
condensed by the water" REPORT Of the COM
mittee Of the Franklin Institute-pages 20, 81 and
%, part lst.)
=" Experiments have concusively proven the
possibility of heating steam in contact with water,
without increasing the temperature of the bulk of
the water, the upper stratum of which alone be-
comes heated By the contact. Let it, therefore, be
! supposed, for example, that the steam has been
heated to four hundred and thirty-fve degrees
| Fahrenheit, and that water has been suddenly in
jected into it, the pressure will be instantly raised
to that due to the presence Of the water; deter
mined, By the experiments of Arago and llony,
to be three hundred and sixty pounds per square
inch, at that temperature or, to use a more
familiar illustration one thousand degrees Of heat
applied to steam will but increase its volume three
| fold, while the same amount would multiply
that Of water one thousand seven hundred
times. This vast increase weuld certainly be mo-
difed by the latent heat absorbed by the water
in its conversion into steam but will nevertheless,
serve to show a sudden and local generation of ex-
cessiye pressure, which, it is very reasonable to
suppose, would result in explosion.
In this case, the water in the boiler had been
low, 50 low as to expose the 1ews and super-heat
the steam and the sudden flow of steam into the
engine and pipes e BY opening the throttle valveD
had partially relieved the water Of its pressure
which had consequently been raised by the agita.
ton, so as to mix with thesuperheated steam, and
had thus been suddenly converted into vapor Of
too high tension for the boiler.
tits we'll known fact to those conversant with the
practical management of the steam boiler that the
water stands higher when the engine is in opera
ton than when it is idle and that it can be further
raised by opening the safety valve; and this effect
is more apparent when the water surface is con
tracted, and the steam room comparatively small ,
Scientific Artisan, CHM, Sept. 9th. 1858
SAFETY.