200 STEAM.
to pass, will cause a tremendous explosion, with consequent
loss of life and property. It is of course quite plain that the
part of the boiler likely to give way under these circum-
stances, will be the softened plates above the furnace. When
heated like this, they lose five-sixths of their strength. In fact
they will be driven into the furnace or collapse. The remedy
against incrustation is a proper amount of blowing out and
chipping off of the hard substance as it accumulates.
225. () Deficiency of Water.-From what was said
under b, it is quite possible that from lack of a duo supply
of water that the remainder in the boiler may assume a
spheroidal condition, which must result, when the heat
decreases, in an explosion. Such a result can hardly be
brought about if the least attention be paid to the water
cocks, the feed pumps, and the glass water gauge. Sufficient
water must always be kept in the boiler to cover every part
in immediate contact with the heat. Should these parts get
hot, as was mentioned above, they lose five-sixths of their
strength, and only one-sixth of the ordinary strength of the
boiler will be an insufficient safeguard against an explosion.
Should the engineer lose his water, he must not attempt to
open the feed valves or cocks-many a life has been thus need-
lessly thrown away to save a little scolding or dismissal. It
is a thousand times wiser and more manly to face these con-
sequences, than to risk life, limb, and far greater punish-
ment. When the valves are thus opened, a great amount of
clastic steam is immediately developed, and the softened
plates give way. Therefore risk no life, open the fire doors
and take out the fires, and then gradually ease the safety
valves. Fusible plugs are a good preventative against acci-
dents happening from a deficiency of water.
226. (9) Collapsing.-A boiler or flue is said to collapse
when it gives way to exterior pressure, or from the air or
steam acting against a vacuum or partial vacuum. In
such cases the steam enters the flues, and scalds and de-
stroys everything in the engine room. A partial vacuum
bas by some means been created in the flues, then the
pressure of steam within the boiler has driven in the plates
of the tube, and an explosion has followed, or the iron las
become softened and worn, and the pressure being greater
