flame spreads outward toward the sides in the
form of a fan. There is no tendency of the flames to impinge directly on
the heating surfaces, and the furnace can handle any quantity of flame
without danger of tube difficulties. The burners should be so located
that the flames from individual burners do not interfere nor impinge to
any extent on the side walls of the furnace, an even distribution of
heat being secured in this manner. The burners are operated from the
boiler front and peepholes are supplied through which the operator may
watch the flame while regulating the burners. The burners can be
removed, inspected, or cleaned and replaced in a few minutes. Air is
admitted through a checkerwork of fire brick supported on the furnace
floor, the openings in the checkerwork being so arranged as to give the
best economic results in combustion.

[Illustration: Fig. 29. Babcock & Wilcox Boiler, Equipped with a Peabody
Oil Furnace]

With steam atomizing burners introduced through the front of the boiler
in stationary practice, it is usually in the direction in which the
furnace decreases in height and it is with such an arrangement that
difficulties through the loss of tubes may be expected. With such an
arrangement, the flame may impinge directly upon the tube surfaces and
tube troubles from this source may arise, particularly where the feed
water has a tendency toward rapid scale formation. Such difficulties may
be the result of a blowpipe action on the part of the burner, the over
heating of the tube due to oil or scale within, or the actual erosion of
the metal by particles of oil improperly atomized. Such action need not
be anticipated, provided the oil is burned with a short flame. The
flames from mechanical atomizing burners have a less velocity of
projection than those from steam atomizing burners and if introduced
into the higher end of the furnace, should not lead to tube difficulties
provided they are properly located and operated. This class of burner
also will give the most satisfactory results if introduced so that the
flames travel in the direction of increase in furnace volume. This is
perhaps best exemplified by the very good results secured with
mechanical atomizing burners and Babcock & Wilcox marine boilers in
which, due to the fact that the boilers are fired from the low end, the
flames from burners introduced through the front are in this direction.

Operation of Burners--When burners are not in use,