The installation of a brick factory depends too much upon local circumstances for us to give precise details on the subject; we must be content with a few general hints. A very common arrangement consists in the construction of a building of two or three storeys, having on the ground-floor the kiln or kilns, and on the other floors drying-rooms which receive heat from the kilns. At the end of these kilns are placed the machines. Communication between the machines and the drying-rooms is made either by brick-elevators (Fig. 187) or by lifts to carry up the waggons and barrows, or by inclined planes.
When space allows, and work is suspended during the winter, open-air drying-grounds are used instead of drying-rooms in storeys. We will speak of them in the chapter on drying.
Economy of labour should be our guide in the arrangement of the machines. As far as possible the clay should pass automatically from the pit to the machines, and from them to the drying-rooms, the workmen's hands being used as little as possible.
The dividing cylinders are over the moistening machine; they receive the clay direct from the pit and pass it, well divided, to the moistening machine. When it issues from the latter, the clay falls into a vertical pug-mill, and the blended paste is then received into a cylinder expulsion machine, which transforms it into bricks (Fig. 153).
Dividing cylinders and the moistening machine are not indispensable, especially for clays which have undergone weathering, but they facilitate and hasten the treatment. In fact, the clay is always extracted in more or less large blocks; in order to get a regular moistening these blocks must be split up with the pick or shovel in a slow and irregular manner. The clay must be arranged in layers for damping, then damped with a watering-can and left for at least twenty-four hours. Then it is cut up and thrown into the machine. But it often happens, when there is a large quantity of clay to be moistened, that a sufficient volume cannot be prepared in advance, or that the distance between the heap of clay and the pug-mill is too large for a single stroke of the shovel; a second workman is then required to bring the clay nearer, and the daily cost is increased.
Fig. 153. Type of Installation comprising Separating Cylinders, Damping Machine, Pug-mill, and Cylinder Impression Machine.
The arrangement shown gives great economy of labour, and whenever the clay is suited for this kind of treatment we should not hesitate to adopt it. Some makers say that their machines treat the clay without previous blending. This is true, but the considerable loss caused by the clay being insufficiently worked up soon makes up, and more, for the cost of a pug-mill.
Estimate of an installation of this kind, producing from 25,000 to 30,000 bricks per day of 10 hours.
2 moistening machines, each producing about 1500 to 2000 bricks per hour, at
2 pug-mills, each producing about 1500 to 2000 bricks per hour, at 1800 francs =
2 cylinder expression machines, able to make pottery, producing about 1500 bricks per hour, at 2100 frances...
Belting, transmission, gearing....
Motive power necessary: 15 to 20 horse-power for damping and cylinder machines, 8 to 10 for pug-mills, 6 to 8 for moulding machines - in all, 40 horse-power, costing for engine and boiler and erection about .....
Installation of a lift, if the drying-rooms are in storeys, or waggons and tramway if the drying is in the open air, about...
The building is estimated at......... for generally it serves to shelter the kilns, and its price is added to theirs.
An installation of this kind allows of an annual output of 6 to 10 millions, according as work is carried on for 7 or 8 months or for the whole year. It requires as staff: 1 engine-driver; 2 men to empty the waggons as they arrive automatically, and to put the clay in the rolling machines; 2 men for the damping machines ; 2 men for cutting; 3 men to carry bricks and place them in the drying-sheds - in all, 10 men.
Net cost of 1000 bricks : 0.22 x 0. 11 x 0.065.
Interest at 4 per cent, on 40,000 fr. = 1600 fr.
Depreciation,, 10 ,, ,, = 4000,,
Per 1000, taking minimum output: 5600/6000= 0.93 fr. ....
10 men at 5 fr. per day = 50 fr., or, per 1000,50/30 = 1.67 fr.....
Carry forward ........ . .
Coal, I kilo per horse-power-hour = 400 kilos
at 25 fr. the ton . . . . 10 fr.
15 fr., or, per 1000, 15/30 =
Oil, repairs, etc., per day . . 5 fr.
To this we must add the cost of extraction of the clay, which varies (p. 32) from
1 fr. 30 to 2 fr. 20, according to the gradient (2 cubic metres per 1000 bricks) the average is....
Total cost .
We must add the cost of pressing for high-class bricks; this is estimated at from 2 to 3 fr. per 1000.