The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1872-02-10
r. From appiesons' Journal.
ryyhv YSofsnss gRnrxf 50 $El

persons C1aG steaIn EXPLOSIONS are often due
20 mysterious If not unpreventable causes
| an account In a weekly journal Of some re.
ent experiments upon this subject declared
/ chat, "to the establishment of the expert.
inenters," certain boilers used in the inyesti.
CATION blew up "under very low pressure
of steam." The causes Of such explosions
are, indeed, not generally known. But to
| readers who live in u country where steam
explosions are subject Of such serious inn
portance to the public as they are with us, a
causes of these explosions can hardly fail to
be Of interest. Such an account, freed from
technicarties, we propose to give in the pre-
sent paper. Among other forms of explo-
sion we shall show how, OH the one hand, an
fatally; and how, on the other, boiler
without a single drop of water in it may be
shattered to fragments by the action of heat
alone.
l. The first and simplest cause of boiler
explosions, frequent though it is, need not
long detain us. 1t is the gradual increase of
steam prcssurc-as in the case of racing
steamboats,, with the traditional negro seated
upon the safety-yalve-to point beyond the
power of the boiler to resist. In a wcll-made
force-one that is much greater than that
under which the boiler is designed to work.
Mr.. Fairbairn concluded, from his expert
mcnts, that one Of the low-pressure boilers
which he burst could not have given way at
pressure of less than three hundred and
fifty pounds to the square inch. Explosions
Of this sort are, more than any other, due to
inexcusabIe carelessness, if not to wanton-
n FOL fbn tboty
have mentioned.
2. Unequal expansion in the boiler, caused
by low water, or by the accumulation of
mineral scale or sediment upon parts of its
inner surface, is fertile cause of explosion
Under such conditions there may be a diff
ference of two hundred degrees or more
Fahrenheit between the temperature of the
hues and Of the boiler-shell; and the unequal
expansion of the metal thus caused is enough
TO rupture the toughest iron. As already
stated, this may happen without the pressure
Of steam to aid it. Near Grand Rapids.
Michigan, boiler twenty feet long was
opened for the purpose of cleaning the fiues.
The man intrusted with this duty. inserted
III armful of shayings in either end of each
IF the two flucs, and set them on fire, hoping
to loosen the incrustatiOns upon them in this
manner. But presently, by the expansion OF
Inc titlcS, the whole head of the boiler was
blown" of, and driven through the walls
of the building into the adjoining field. An
American engineer, Mr.. Wizard, claims to
have devised method Of keeping every part
of Il boiler at the same temperature, and so OF
avoiding all explosions from unequal cXpan-
sion: but we must not stop here to eX.
plain it.
8. Explosions caused by the propulsion OF
the water' arc of special interest because
they form one class of the So-called mystic
riolls explosions. In these cases no excessive
pressure of steam or heat of fires is apparent
the gauges stand at their usual level; and yet
while there is no sign of danger, fri@httu
| explosion may occur. rs if some new and ire
sistiblc energy were liberated within the fated
boiler. Such is indeed the case, though it is nc
| new explosive compound, generated by the
presence of oil or other impurities in the wa.
| ter. as some engineers have argued, that doe:
| the mischief. In these cases, some part OF the
boiler below the water-lcycl has become
heated to higher degree than the watcrabovt
| It. The result is, that the water is repealed
| from the metal, and Il thin film of steam inter
venes between the two bodies. In thi; condi
| ton, which is known rs the 'Sphcroidal state,
! the iron may become intensely hot, while tho
| watcrrcmainS comparatively cool. But now
| let any clllSe-:s Il strong circulation otthc Wa
ter i'm the boiler, where it itshes around under
| the fierce heat and pressure like Il tortured
| aninal-forcc it into contact with the red-hO
| metal An immense volume of steam is in
| SANITY generated; it "thrOWs" - the wateI
above it with the energy Of bullets before N
| exploding charge of powder, and the force o.
| yhis tremendous steum-hammer Is sufficient
| to sl.atter the top of the strongest boiler il
| llse These terrible explosions are apt t.
| occur at the moment Of starting locomo
| tive or marine engine. when the escape i
shut down and the pressure Is suddenly III
creased 70 prevent them, it is necessary t.
make sure that the fires are of uniform nca
throughout their whole extent, so as to ayoC
| excessive heating in any part of the boiler
and also to avoid any too sudden increase
| (cyen though it be slight one) of the pres
| sure in the boiler.
| 4. In the lust class of explosions to be con
| sidered there is the same Slattcrin% Of th'
upper part of the shell Of the boiler as il
| those that we have Just described. But they
are at first sight more mysterious than those
for in them no evidence can be found that any
part of the boiler has been at all oyerhcated
and TO make tile surprise still greater, the!
occur at low temperature of the water, alt
aco rrcspondin@Iy low pressure ofsteam: Wllll'
vet they are of the most frightful violence
As, under the subject of "lmcqual eXpan
sion" we have described explosions that ma.
take place without any steam, so now w
have reached class of explosions that may
occur without any boiler. They may be thu
explained: Letan open pan of water be KEEP
for u long time heated Just to its boiling point
| Little by little, it loses the air which it con
tains in solution, and its boiling point rises
In this way NJ. Denny heated water to tW'
hundred and seycnty-lye degrees Falren
hcit, the attraction Of the particles of Watc
for each other being apparently increased
but finally il YaporiZed with eXpio>iv
| suddcnneSS. In the same manner, when Il
last the temperature of the waller III TN
boiler is carried to 4 high point, and tn
water j. freed from air. vaporlZatlon may oc
cur, not gradually, but instantly. The opcl
Dan of water has been known to cNplod
almost like q charge Of gunpowder, ana, &C
cording to NJ. Denny, with fatal result.
THESE explosions may, then, be said to result
from temperature above that which is du
to the pressure" Mr.. J. II. Robinson,
competent engineer. says, in little bool
unon steam-boiicr explosions. that all violcn
explosions occurring when the fire is mode
rate and the steam low may he ascrDed t
this cause. In these cases the water
thrown much in the same way rs in the OK
blossoms last described; and so much of tn
water may be overlicated, and to such dc
gree, that the top of the boiler shall he shat
tered by the first blow. That the water i
raised to very high temperature i'll thes
explosions is shown by the fact that it some
|'times flashes instantly and entirely int
steam, leaving no trace of water near til
exploded boiler. NJ. Pendrcd, of Dublin
experimenting upon this subject, erected