THE BLAST-FURNACE DEPARTMENT: STANDARD BLAST FURNACES.
23
is the most convenient for working and for reducing the
ores which are employed. One of the furnaces above
mentioned was put into blast on September 8th, 1897 ; the
construction of this furnace is shown in section and plan,
Fig. 46 ; such modifications as hâve been introduced
refer almost entirely to matters of detail. The mouth of
the apparatus, a trame consisting of heavy cast-iron
girders that shift the weight (or beai’ing points) of the
apparatus nearer to the edge of the furnace, and to
tliose points where the masonry incurs no risk of being
injured. Within the gas cliamber, a cast-iron lining
2 in. thick has been placed, with the object of protecting
m
Fig. 46. Sections of Standard Type of Blast-Fumace.
the furnace is closed by a bell operated by hydraulic
presses ; the arrangement is peculiar to Creusot, and is
clearly illustrated by Fig. 47. The closing apparatus in
the earlier types was placée! on the refractory lining at
the top of the furnace. This arrangement was found
wanting in stability when the lining became worn in the
vicinity of the falling charge. The defeet has been
remedied by placing underneath the columns carrying
the inner shell from breaking down on account of the fall
of the charges. The air mains have been lightened, in
such a way as to facilitate moving and replacing them.
It is always désirable, as far as possible, to shift the
mains by hand, without the use of crânes, which are
inconvénient and less rapid than manual working. The
tuyere arches have been reduced to a minimum of opening,
and are made of steel Castings ; the strength of the hearth