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REVERBERATORY FURNACES                          61
the designer placed a wall in the center of the heating chamber and
connected the two halves of the chamber by ports in the lower
portion of this wall. Nevertheless the bricks on the hearth were
not sufficiently well burned. It therefore became necessary to add
a supplementary waste gas flue with ports in the hearth of the
heating chamber.
A very interesting type of chamber reverberatory furnace has
been installed at the Lyswa works for the remelting of scrap and
large broken castings. It was built by M. Onoufrowitch after an
American design (Fig. 41). The rear portion of an ordinary
reverberatory furnace has been replaced by a large chamber,
the waste gas flue having been left in its former place.
Computations for this furnace may be made in the following
manner: the consumption of coal is 0 kg 31 per second. Assum-
ing that the air supply is 1.40 times the theoretical requirements of
combustion, and that the temperature t is equal to 1300°, the
volume of gas Qo = l m3 82 per second and Qi3oo = 10 ni3 48 per
second. For a furnace width of 1 m 60, therefore, hi3QQ= 1 m 05.
That is, the normal thickness of the layer of gas below the
inverted weir for this furnace is equal to 1050 mm and, for this
furnace to work, the distance from the hearth to the top of the
waste gas port should not exceed 1050 mm. Otherwise the hot
gases would not touch the hearth of the furnace and it would not
heat well. The vertical distance from the tapping hole to the
top of the waste gas port actually is 1100 mm, which agrees very
"well with the calculated distance. The charging door of this
furnace is very large and high, but it. is hermetically closed when
the furnace is in operation, and on this account it occasions no
loss of the hot gases.
The volume of the heating chamber of the Onoufrowitch furnace
is llm3 00, of which 8 rn3 70 are comprised in the chamber. By
reason of this, the gases remain in the heating chamber slightly
longer than one second, and therefore the furnace gives good
A very interesting type of furnace is that used in the heating
of steel plates. In this case the necessity of having the hot gases
at the level of the hearth is still more absolute than in ordinary
furnaces. In effect, the presence of air upon the hearth of the
furnace causes considerable damage, as it oxidizes the iron and in
this manner produces a quantity of surface defects. It is for this