Wauwatosa news. [volume] (Wauwatosa, Wis.) 1900-1948, 1903-05-16
THE TRUE FLASH BOILER.
Objection Raised to the Term in Connec
ton With the LONGITUDE
or SerpoIlet Type.

Objection has, Of late, been raised
against the use Of the term flash boil
ers" in connection with boilers of the
small, longitude, or Serpoiet type Those,
it has been argued, are nor fash boilers
at all, though, as the London Engineer
says, it is not easy 10 find a better or
more compact name. The true flash
boiler, according to the same authority,
is q very old invention. 1t consisted es-
sentially Of a large cast iron pot the
major portion of which was kept red hot,
and into the pot water was injected
through rose of sprayer, and, falling on
the hot iron, was instantaneouSly
flashed" into steam. The intention of
the inventor WAS to send in just so much
water at each stroke of the engine as
would supply steam for the next stroke.
In another form of flash boiler mercury
was kept at a high temperature and wa
ter was dropped on il 10 be flashed into
steam. These, and a dozen similGx in
ventionS, all died a natural DEATH The
SerpOlet boiler closely resembles the
Herreschoff and several other steam gen
orators, in that it consists of a long coil
OF tubing, into one end of which water
IS pumped, and out of which, at the other
end, 1t IS confidently expected that steam
moderately superheated will issue. Only
qualified success has hitherto been Oh
tanned with these steam generatorS-they
do not in any way deserve the title Of
boilers.
If We take a small. thick pipe, contin-
ues The Engineer. about 12O feet long.
and. say, 12-inch bore, coil it closely on
itself, heat it highly, and pump water
III at one end white we take OFF steam at
the other. certain curious phenomena Will
now and then present themselves, the
causes of which are a little obscure There
are various agencies at work, each pro-
ducing. or trying to produce, its own sDe-
cial results. Unless these agencies are
taken into account, little satisfaction will
be gotten from a longitude generator.
1t would, however. be impossible to deal
with these matters here in any detail.
We can only, within reasonable limits
of space, direct our readers attention to
them III very gencraI way. In the first
place, 1t IS clear that highly heated wa
ter, saturated steam and superheated
steam traverse the whole length of the
tube. and when all things proceed in an
orderly fashion we shall find that differ
ent lengths of the tube viii contain in
succession cold water. hot water. Satu-
rated steam and supcrheated steam Eacn
stroke of the pump will be followed by
the rush to the engine of the precise
equivalent in steam of the water sent in
by the pump. SO far, so we'll TheO-
reticaily, there is no reason why this
should not be the sequence of events
In practice. this result is very otter
secured; but, unfortunately, it also often
happens that it is not secured, and if any
permanent success is to be obtained VITA
this type of boiler it will be by ascertain
ing and eliminating the cause of trouble.
The main cause of trouble is want of
regularity in communicating the heat to
the water. During trials made years ago
by engineers of the United States navy,
II was found that now and then in a Her
reschoH boiler the water filled the steam
space, and there was nothing but steam
III the water space. Things got inverted
In small-tube boiler. if steam is sud
denly generated in the lower part of the
tube, it will blow the water above
It into, the upper part of the tube.
The phenomenon is brought about
in two ways. The first and sim
plest is sudden variation in the
temperature of the furnace. This is
largely avoided by the use of oil fuel.
The second. most complex and most
interesting, is want of permanent contact
between the wate" and the tube. In
other words, il appears to be by no
meas easy to keep the surface of these
highly heated, tubes wetted 1t is not
so much that the spheroidal condition is
established as that some kind of repul-
sion appears to be set up between the
metal and the water. The spheroidal
condition may, however, also be set up.
Be this as it may, for some reason not
fully explained, heated plates are in GER
tain cases not thoroughly wetted by wa
ter. Consequently we find that not in
frequently violent surging and crackings
take place in flash boilers; the production
of steam becomes irregular, and the en-
CINE may stop or be filled with water
Most makers of fash boilers repudiate
the idea that Spheroidicity manifagts it.
However there 10 =
one time the generation of steam goes
on with clockwork regularity at another
we have turbulence and printing.
AS there is no steam space and no re-
serve of water in any but the most lin
tied sense of the terms, it is evident that
whatever goes, on in the pump is imme-
dlately reproduced in the boiler. and
whatever takes place in the boiler at
once affects the engine. Thus. if the
pump misses a few strokes, the water
level will instantly descend in the tube.
the water will become hotter. surfaces
will become dried. and when the pump
again throws water, the surface may
refuse to be wetted. and so the whole
balance is upset. Or. again, the pump
may throw too much water. with the
result of lowering the temperature. and
possibly drowning the engine. In the
same way, all going on steadily. the fire
is suddenly urged; the result is that the
water is now evaporated faster than the
pump sends it in and large portion of
the tube may become dry In one word.
the whole operation of generating steam
and working an engine with a fash
boiler is an exceedingly delicate physical
operation. depending for its success on
the maintenance of a precise balance in
the relations of the various phenomena,
which balance is so often secured that
the long small-tube boiler enjoys great
deal of favor with those yyhn thorouphlv
understand it, while it inhicts untold
miseries on those who do not understand
it. and are unable to humor its very Pc
culiar and domneering idiosyncraSies
Dogs as Policemen.