CONTINUOUS HEATING FURNACES
that the wall ab resulted in the formation of a pocket of stagnant
gases. As a remedy for this condition, the author suggested the
removal of the wall and the reconstruction of the furnace according
to the sketch (Fig. 122).
NOTE.—Furnaces with descending skids give a great deal of trouble with
billets sagging due to improper heating conditions.
Another small furnace, of a similar design, is shown in Fig. 123,
in which the reconstruction recommended is shown in dotted lines.
These changes were made, and the output of the furnace was
thereby increased from 11.2 tonnes to 14.7 tonnes a day, that is
to say, an increase in output of 30 per cent, with the same coal
As to the profile which should be given to the roof of a con-
tinuous heating furnace, the following suggestions may be of
If the mixture of the air and the combustible gases is not
sufficiently intimate in the firebox, it will be necessary to use some
method of restricting and retarding the flow of the reacting gases
within the port. The device frequently used is a strangulation or
restriction of the port or passage through which the reacting gases
enter the heating chamber. A serious disadvantage of this
method is that it gives the jet of flame an exaggerated velocity.
In order to absorb and reduce this velocity, two special forms of
roof construction are used, which are shown in Figs. 122 and 123.
If the mixing in the firebox is well accomplished, or if the gases
flow into a large free space under the roof of the heating chamber
at a low velocity, these spaces will act as a combustion chamber,
and there will be no necessity for the strangling of the flow through
If the rear end of the roof ascends, recourse is frequently had to