The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1873-01-24
SUpTRHEATED STEAM.


An Engineer Who sustains the Fire
Marshal I'm His Statement that Build
inSs May BE Ignited by the Heat Arising
from Superheated Steam.
NEW YORK, jan. %, 1873
To THE EDITOR OF THB HERALD
Since the report Of the Fire Marshal was made,
in which he stated that many fires have been caused
by superheated steam, and that under certain con-
ditions steam in pipes and boilers "set up in brick
work" might become 0verheated Oh superheated
with a,temperature high enough to cause the
ignition of cOmbustibles contiguous to the pipes
for this is essentially the assertions he has made
much has been said or written and published, pas
s0nate or dispassionate, by interested and disih.
terested persons in relation to 1t, and the public
mind has only been confused, while the real meTats
OF the important question involved have keen
lost sight or 10 does not prove that steam
may not be superheated in boiler ''set up in
brick work. and under certain other conditions
heretofore named to assert, as one OF your cOrre-
spondents has, that during several weeks when the
fires were ''0anked" in marine boiler under his
charge on a steamboat, the engineer did not set
fire to his boat, see any evidences of superheated
steam or believe that steam had ever been super
heated under such circumstances, because great
many witnesses who have not are required to
COunterbalance the testimony OF one who has seen
thing, and because the marine boiler referred to
was not 'set up in brickn-a condition essential as
will be SEEM to the theory of the Fire Marshal For
an engineer to refer to those pressures within q
boiler 'that always attend upon named tempera-
turcs," only seems to show, when no explanation Is
made. that he does not know That the rate Of in
crease Of expansive force for increase OF tenn
peratures is widely different with superheated
steam and saturated steam. For instance, take
saturated steam at fifty pounds pressure to the
square inch and has temperature OF 30l degrees
Fahrenheit, which is the same as the temperature
of the water within the boiler. Now, add Al de-
GRO nf no n H.
crease in temperature to the same degree and
the pressure will be 100 pounds. But II we increase
to act upon the water until the pressure Is In
creased to 100pounds, the steam Will have temper
combustbles as charcoal &C., while the water Will
only have the temperature OF 342 degrees Fahren-
heit All that part OF this discussion that relates
to dissertation or decomposition oil steam into Its
original elements, the separation Of oxygen and
hydrogen, the ignition, explosion or combustion
OF these gases within the pipes TO heat them or to
set flre to buildings upon escaping Through the
pores" or via leaks of the pipes, should be dis
carded, as the theory which presupposes that
buildings are set on fire or consumed by over
heated steam refers only to steam confined within
boilers or pipes which has received heat enough to
sufficiently supcrheat 1t from some source OF heat
capable Of giving it the high temperature required,
and that after 1t Is so heated that 1t Is conveyed to
the place where the combustibles are found along
the pipes, heating them by its contact VITA the
material of which they are composed, alter which
the fire Is started OF COmbustibles ignted by the
Overheated pipes.
1t is wen known that steam can be superheated in
aproper apparatus readily as air, any other gas or
combination OF gases. Many persons do not know
land ignorance has made trouble many times be-
fore) that steam can be heated much more rapidly
than water-that is, the same number OF units OF
heat will raise the temperature OF pound or
steam-ata low or high pressure, indfferently-
two or three times as high as pound OF water
would be heated by the same quantity OF heat.
And it, instead Of considering the relative quanti
ties OF steam and water to be heated by weight, we
take them bulk for bulk, it can be seem as pound
OF steam may at the pressure of the atmosphere
occupy about seventeen hundred times as much
space as pound OF water, upon the communica-
ton Of an equal quantity of heat to one seven
the temperature would theoretically rise from
three to i've thousand times as high in the steam
of knowledge of our subject, we are prepared to
believe that small quantity OF red hot brick with
nearly equal capacity for heat to water, could
steam should be enclosed in pipes, within a
red hot ''baker's oven," as described by the Fire
Marshal in his earnest and lucid speech before the
Polytechnic Club OF the American Institute.
Water cannot be heated from its upper surface
downNards while steam Is being generated or
while 1t has o temperature above forty degrees
Fahrenheit; and this is also an important fact in
connection with this subject, because so many, in
presence OF water" as If that made difference
under the circumstances referred to. AS TO
Museum we're the all ra ae upaer ah e
boiler was enclosed in pipes OF considerable con-
tnuous length, running back and forth In zig2ag
direction having about ten folds or returns six OF
which were usually filled with water, the four
upper ones with steam. All these pipes were
nudded together within thick brick walls, forming
q chamber enclosing the pipes, sizes and top, and
the hot coal fire built on CRATES at the bottom,
the hot gases resulting from the combustion OF the
fuel impinging directly against these pipes and in
terror OF the walls Of the chamber. 1t can be seen
that ten or twelve hours OF steady and vigorous
firing would make all the interior or the brick
work red hot 1t would be expected that
the steam contained in the upper rows OF
es W"n be be or the
action Of the steam generated In the lower pipes,
by which such ebullition would occur as to sur
charge the steam with water enough to absorb the
heat Communicated directly to the higher pipes or
radiated 10 them from the red-hot walls. When
the hre Is .'banked' or Withdrawn the ebulliton
ceases, and the water contracts and finds lower
level. The steam first becomes 'dry Steam," and
is then superheated. entirely by the heat radiated
these pipes would be made very hot under such
circumstances if there was no steam or water In
them, or if they contained only common air.
Dry steam Is heated at exactly the same
rate as air, and the water Is quiet in
the bottom OF the boiler at this time or in the
lower tubes after the fire is banked, and as 1T can
not be heated by the steam, the steam cannot part
with any of the heat 1t has received in that man
ner. The superneated steam. therefore, and
cendary, along the pipes lea ing from the top o.
the boiler to the place where "combustlbles,'
charrcd by previous visits OF the element, to be
found, OF easy ignition. Fires caused In this man
ner usually occur In the night, when inmates o.
buildings sleep and at the hour when no one IS on
the watch-uSuay, too, all the evidences of the
cause are destroyed Fortunately, in large mum
Der OF late cases the fire has been discovered and
extinpulshed so early as to afford clew to the
vgilant Fire Marshal and his aids Tor the detection
OF its real origin.
II those who pronounce the statements made by
the Fire Marshal or myself In relation to super
heated steam ''absurd" and "monstrOus" would
examine the records in his office, or take the
trouble 10 visit steamboats, or buildings containing
boilers with me, or will ask questions OF engineers
| can dcsignate--who are witnesses, who nave seer
the thing not OF those who have not-such con
1rmation Of the TACT that fires result from super
heated steam will be found as to preclude the pos
sibIlity OF further misunderstanding about 1t. Re
specially, NOhMAN WlAhD.