The Progress., 1889-03-02
"a LESSON ON STEAM.
xhes Nature OF tho Force which Drives Il
ss Engines Of the Gnnn1rrY. -. .


The Nature Of the Force Whioh Drives tho
Engines Of the Country.
will begin now, and ask you what
. steam engine tsp
hats steam enginep Why, it's
this machine here, that drives the mill.
That easy enough. =
Why does steam let into a machine
drive itp Common air let into it
swouldn' { drive 1t, would itpn
mo, sir. =
ssThen there must be something
about steam different from other
fluids, such as air (for air is a d uid the
same as water), to fit it for motive
spoWerP"
IS. sir: =
well, let us see II we can find out
what peculiarities it has. Air and
steam are just the same in one respect
they are both tluids-or flow like
fluids. and are therefore called fluid
gasses, and either one, under pressure,
would move an engine; both are
capable Of expansion and contraction
in nearly equal degree, SO nearly that
the laws of one govern the other,
and''-
Hold on, now, my friend; you are
getting too fast. You are Just like all
the fellows who under AXE to tell a
man who has had no chances son !
thing about his business. Get back,
will you, to where you started, and
tell me why steam drives an engine. .
by reason of its elastic forcep''
q "And how does it get that force?''
"From being coiled up-just as a
spring is wound up-by heat. Steam
is hevapor of water. and arises from
it at all temperatures above zero. You
can see it any cold morning evaporat-
ing into the air from the surface Of a
pond = =
''Well that's all right. have seen
it. though didn't know it was steam,
but since the vapor Of water Is steam,
! suppose it was. Now would that
steam drive an engine?''
mo, not at the pressure at which It
is generated, When you see the vapor
Of water rising from u pond it is at
the same pressure as the atmosphere,
and has no force above atmospheric c
pressure; but the same vapor con-
tinued in a boiler. and compressed by
the constant addition Of more vapor
generated by heat. will increase to any
rnnI1irol 1,1sn cY,,,a ~
Then all there is about steam is
IItaHhat it is the vapor Of water, and
gets its elasticity from being confined
in a close vessel like steam boiler,
is that itp'
THAT is the exact fact. Steam at
the pressure Of the atmos phere is pre-
cisely the same as steam at 15o
pounds per square inch; only differing
in the Intensity of the force. If you
let steam of 80 pounds down to at
mospheric pressue again, you see it
is the same old thing. and if con-
densed. it finally becomes the water
it was generated from
"Ain't steam some kind Of gas
that will explode if touched of at HIGH
pressurep''
No; the water Of winch the steam
IS made consists of two gases, oxygen
and hydrogen, and the steam itself is
just the same. Now these gases can
be divided as you would say, or Sc pa
ratel again by destroying the steam;
that is by forcing it through a tube
heated white hot. The oxygen likes
the hot iron better than it does the
hydrogen, and goes for it. while the
hydrogen-g1ad to get rid of the
oxygen-goes on by itself. Now, if
these two gases, oxygen and hydrogen,
are brought together in st ,ut re-
ceiver In certain roportions. they can
be ignited and exploded by an
electric spark, and their union results
III water, but to explode either of the
gases alone requires a certain amount
Of common air to be mixed wilt hem,
and this is not found in steam boiler.
That's what you mean, suppose, by
steam turning into gas, is it note'
" Vile yoo, 4EOdO SOilFcW WlkotO tNIC q
boiler blew up once because the steam
was red hot, and turned into gas, and
I was kinder interested in that part of
your story, for ! sometimes get this
old kettle pretty hot myself, and
wanted to know if there was any
truth in it. =
There isn't the sIightcs.. Under
the conditions under which Steam is
used in 4 steam boiler, it might get
even red not and there would be no
danger whatever, unless there was
sufeient surface Of red hot iron to
absorb the oxygen, and atmospheric
air admitted in sufficient bulk 10 dilute
the hydrogen to the explosive point.
That's 4 cross roads notion Of the
cause Of steam boiler explosions,
which you must pay no attention to
whatever. All you've got 10 do IS to
keep scant three gauges Of water in
that boiler; keep the safety valve ii
good order, and go ahead. Z Milling
EaaQiasesa.