The Weston Democrat. [volume] (Weston, W. Va.) 1875-current, 1875-02-08
ABOUT STEAM BOILERS.
APraetieal EusInccr Tells N. why they are
Weakened nnd Explode.

tr weakened and Explode.
Safety and the production OF a large
quantity Of dry steam are the two essen.
tails Of a good boiler, said james Whit
ney before the New York Society Of
Practical Engineers, but these two re-
quirements are antagonistic 10 each.
other, and the best boilers are the result
Of compromise. II we could have q
perfect hollow sphere Of metal, we would
have theoretically the strongest form OF
steam generator, and in the infancy OF
steam engineering some spherical
boilers were made in England, and con-
tinued in use nearly 10 our own time.
But II is possible to bring the FIRE in
contact with only o small portion Of the
surfdce, and hence we have little steam
for good deal of fuel. The form,
therefore, is changed to q cylinder, with
the fire underneath and playing upward
against the sides. This affords q greater
heating surface, but the ends do not
bear the same relation to the pressure as
the sides, and must be stayed by braces
that shift a portion OF the strain on the
heads to other portions Of the shell. II,
now, our fire is started under the boiler,
the lower parth fasterthan the upper
part, and consequently expands more.
This bends the lower part outward on
the arc Of circle, which, although i'm
perceptible to the eye, Is the result Of
IN irresistible force. This expansion Of
the lower part Of the boiler brings o
strain upon the upper part; when the
boiler IL allowed to cool IL resumes It's
original form. At each changeof tenn
perature, therefore, there Is q to and fro
movement Of the Tapped edges Of the
plates where they are eriveted together.
The final effect Is that the plate
cracks along the line Of its least resist
ance. In some boilers the fracture may
be along q line Of riyets, and be entirely
hidden from any possible view. But Il
the riyeting be extremely good the min.
ute bonding to and fro Ia more apt TO
occur in one plate close to the over.
tapping edge Of the plate to which 1t is
riyeted, and when the crevice opens 10
the interior Of the boiler, any acid in the
water viii act chemically 10 increase 1t,
This is termed growing by the Eng
lish engineers, and is not confined 10 any
particular type. For II, instead Of
placing our fires beneath the cylinder,
we extend q large cylindrical fue through
the cylinder or shell Of the boiler, we
simply change the locality in which the
effects Of this alternate expansion and
contraction are exerted. The fues are
fixed in the ends Of the shell, and are
hotter than the shell, and Of course ex-
pand more. Being confined against the
ends, the fiues bend upward. II we put
on steam drum in which the otherwise
waste heat from the escaping products
Of combustion may dry the steam from
its contained yesicles Of yapor, we ac-
complish IN increased economy Of fuel;
but by adding a vertical cylinder inter
secting horizontal one, we have IN
additional joint between portions subject
to quite different temperatures, and at
which "grooying " Is liable TO occur. II
the joint is made with angle iron, in
which the grain runs parallel with the
sharp corner in the angle Of the iron,
the danger Is much increased, and this
has led American engineers 10 discard
the English plan Of using angle iron in
steam boilers, The new and better sys-
tenn is to make the joint on q curve hay
ing radius OF about four inches. The
ends Of the shells or cylinders Of boilers
are often fitted in their places with angle
iron, but the same objection holds as in
the filling Of the domes. AS rule.
sharp and rigid corners should be avoid
edbetween plates liable to unequal ex-
panGon from heat. This gradual de-
terioration Of boilers from the cause In
dicated is one Of the most insidious Of
al the causes OF explosions, and 1t is
one that 10 inherent in all notifications
81 the cylinder type. Skill and good
Judgment may reduce the danger but
cannot wholly obviate 1t. Il