When the clays are rich and require soaking in troughs, the following arrangement maybe adopted (Fig. 154). An endless band brings to the pug-mill the clay which has been soaked in the troughs, and after pugging the clay falls into a machine which transforms it into bricks.
We suppose in this installation that the clays do not need to be separated. Rich clays should generally be mixed: Fig. 155 shows an installation in which the mixing mill is placed above the soaking troughs. These troughs are provided with doors in one side, and near these doors is placed a pug-mill. The workman cuts the clay out of the troughs vertically and throws it into the pug-mill. Thence it goes to the moulding machine.
Estimate of an installation of this kind, producing front 25,000 to 30,000 bricks per day of 10 hours.
2 mixing mills, at 1100 francs...
2 pug-mills, at 1800 frances...
2 cylinder machines, at 1600 francs...
Belting, gearing, etc...
Motive force : 4 horse-power for the mixing mills, 8 to 10 for the pug-mills, 6 to 8 for the moulding machines - in all, 25 horse-power, costing for engine, broiler, and erection, about....
Lift or tramway with waggons, soaking troughs, and sundries....
The daily output requires a staff of 1 engine-driver, 2 men for the mixing mills, 2 men to spread the clay in the troughs, 2 men to fill the pug-mills, 2 cutters, and 3 men to take the bricks to the drying-rooms - altogether, 12 men.
Net cost of 1000 bricks : 0. 22 x 0. 11 x 0.065.
We shall give as a last example of installations, one for manufacture with dry clay. The dry state is obtained by natural means, or more frequently by warming in a stove or in the kilns. The clay, having been crushed by a mill with perforated pan, falls into a receptable below, whence a lift takes it to a sifting cylinder. The powder is received into a damping machine, and the tailings are returned to the crushing mill. The clay having been suitably moistened is once more mixed in a mill and finally falls into a receptacle, whence it reaches the press through a conduit. These presses (Fig. 157) are placed near the kiln, for the bricks manufactured by them are hard enough to be at once fired.
The estimate of such an installation is as follows: -
2 crushing mills, at 5350 francs .........
2 sieves, at 675 francs ...........
2 damping machines, at 835 francs........
2 mixing mills, at 3000 francs .........
5 moulding machines, at 5300 francs........
Belting, gearing, lifts, etc...........
Motive force : 10 horse-power for the crushing mills, 6 for the sieves and damping machines, 6 for the mixing mills, 20 for the moulding machines - in all, 42 horse-power, costing for engine, boilers, and erection, about .
Total for machines .
The staff comprises: 1 engine-driver, 2 men to put the clay into the crushing mills, 5 men for the machines - altogether, 8 men.
Interest at 4 per cent, on 31,000 fr. = 1240
Depreciation ,, 10 ,, ,, = 3100
Per 1000: = 4340/6000 = 0.723..........
12 men at 5 fr. a day = 60 fr., or, per 1000, = 60/30....
Coal, 1.25 kilos per horse-power-hour =
310 kilos at 25 fr. the ton . . = 7.25 fr.
12 fr., or, per 1000, 12/30
Oil and maintenance, etc. . . 4.25
Extraction of the clay, per 1000 bricks...............................
Total cost .