iler equipment. The tendency of soot to collect on the crown
sheets of certain vertical water-tube boilers has been noted. Such
deposits are difficult to remove and if corrosion goes on beneath such a
covering the sheet may crack and an explosion result.

[Illustration: Rear View--Longitudinal Drum Vertical Header Boiler,
Showing Access Doors to Rear Headers]

It is almost impossible to thoroughly clean water legs internally, and
in such places also is there a tendency to unsuspected corrosion under
deposits that cannot be removed.

In Babcock & Wilcox boilers every portion of the interior of the heating
surfaces can be reached and kept clean, while any soot deposited on the
exterior surfaces can be blown off while the boiler is under pressure.

Inspection--The accessibility which makes possible the thorough cleaning
of all portions of the Babcock & Wilcox boiler also provides a means for
a thorough inspection.

Drums are accessible for internal inspection by the removal of the
manhole plates. Front headers may be inspected through large doors
furnished for the purpose. Rear headers in the inclined header designs
may be inspected from the chamber formed by such headers and the rear
wall of the boiler. In the vertical header designs rear tube doors are
furnished, as has been stated. In certain designs of water-tube boilers
in order to assure accessibility for inspection of the rear ends of the
tubes, the rear portion of the boiler is exposed to the atmosphere with
resulting excessive radiation losses. In other designs the means of
access to the rear ends of the tubes are of a makeshift and
unworkmanlike character.

By the removal of handhole plates, all tubes in a Babcock & Wilcox
boiler may be inspected for their full length either for the presence of
scale or for suspected corrosion.

Repairs--In Babcock & Wilcox boilers the possession of great strength,
the elimination of stresses due to uneven temperatures and of the
resulting danger of leaks and corrosion, the protection of the drums
from the intense heat of the fire, and the decreased liability of the
scale forming matter to lodge on the hottest tube surfaces, all tend to
minimize the necessity for repairs. The tubes of the Babcock & Wilcox
boiler are practically the only part which may need renewal and these
only at infrequent intervals When necessary, such renewals may be made
cheaply and quickly. A small stock of tubes, 4 inches in diameter, of
sufficien