The Flow Of Gases In Furnaces

220

APPENDIX VII

regularly. These reversing machines also permit the operator to
reverse the furnace at any time he sees fit. Machines of this type
have been installed at a number of by-product coke-oven plants,
but there seems to be a tendency upon the part of the " heaters "
to cut out the automatic timing device. It is hardly necessary
to state that a certain amount of passive or impassive opposition
might be expected to the use of a machine of this kind, a species of
sabotage which is extremely difficult to overcome. Under
ordinary working conditions there should be two to eight reversals
per hour, and it is necessary to proportion the checkerwork to
suit the longest time period.

TABLE 7

MAXIMUM AND MINIMUM VOLUME OF CHECKER BRICK ASCERTAINED PROM

PRACTICE

Capac-
Gas
Air
Air+Gas

ity,

Tons

.

Minimum
Maxiniuni
Minimum
Maximum
Minimum.
Maximum

10
29.7

39.1

68.8

15
33.6

41.0

74.6

20
21.0
25.8
23.6
39.0
44.6
64.8

25
27.6
29.3
32.7
40.8
60 .,3
70.1

30
17.7
23.4
23.6
31.2
41.3
54.6

35
18.7
19.0
24.6
25.9
43.3
44.9

40
18.4
21.0
23.6
24.3
42.7
44.6

50
17.9
66.0
31.4
66.0
50.4
132.0

60
21.0
46.3
23.6
94.4
44.6
128.2

75
33.5
44.5
44.5
70.2
78.0
114.7

80
21.0

24.8

45.8

100
21.0

23.6
----
44.6

The time factor has a definite bearing on the thickness of the
checker brick. This is shown by the curves of Fig. 153. These
curves were plotted for a fire-clay brick. For a silica brick or
brick of other material the co-ordinates would be different, but
the curves would be similar to those shown. These curves show
the rise in temperature at the center line of a brick in per cent
of the rise in temperature at the surface, when both faces of the
brick are heated during various time intervals. In these curves