through the heating surfaces.

Boilers should be taken out of service at regular intervals for cleaning
and repairs. When this is done, the boiler should be cooled slowly, and
when possible, be allowed to stand for twenty-four hours after the fire
is drawn before opening. The cooling process should not be hurried by
allowing cold air to rush through the setting as this will invariably
cause trouble with the brickwork. When a boiler is off for cleaning, a
careful examination should be made of its condition, both external and
internal, and all leaks of steam, water and air through the setting
stopped. If water is allowed to come into contact with brickwork that is
heated, rapid disintegration will take place. If water is allowed to
come into contact with the metal of the boiler when out of service,
there is a likelihood of corrosion.

If a boiler is to remain idle for some time, its deterioration may be
much more rapid than when in service. If the period for which it is to
be laid off is not to exceed three months, it may be filled with water
while out of service. The boiler should first be cleaned thoroughly,
internally and externally, all soot and ashes being removed from the
exterior of the pressure parts and any accumulation of scale removed
from the interior surfaces. It should then be filled with water, to
which five or six pails of soda ash have been added, a slow fire started
to drive the air from the boiler, the fire drawn and the boiler pumped
full. In this condition it may be kept for some time without bad
effects.

If the boiler is to be out of service for more than three months, it
should be emptied, drained and thoroughly dried after being cleaned. A
tray of quick lime should be placed in each drum, the boiler closed, the
grates covered and a quantity of quick lime placed on top of the
covering. Special care should be taken to prevent air, steam or water
leaks into the boiler or onto the pressure parts to obviate danger of
corrosion.

[Illustration: 3000 Horse-power Installation of Babcock & Wilcox Boilers
in the Main Power Plant, Chicago & Northwestern Ry. Depot, Chicago,
Ill.]

BRICKWORK BOILER SETTINGS

A consideration of the losses in boiler efficiency, due to the effects
of excess air, clearly indicates the necessity of maintaining the brick
setting of a boiler tight and free from air leaks. In view of the
temperatures to which certain portions of such a setting are subjected,
the materi