COAL-BREAKING MACHINERY.
Where a large business is done, the saving of five per cent. in the waste of coal by breaking effects a considerable saving in the year, and this can be done in most cases. On 500 tons per day this amounts to 25 tons, or 7500 tons per annum, which is worth from $1.00 to $1.50 per ton at the top of the breaker. We think some of our improved breakers effect at least this saving over others; and in some cases we have no doubt that the waste is ten per cent. greater than it should be, with proper care and pro visions. We think the waste occasioned by the crushing of coal in rollers ranges from 10 to 20 per cent. of the whole shipments, as a general rule: we include in this estimate pea-coal. In cases where all the coal goes through the rolls, the waste is greater, and may reach, in a few cases, 25 per cent. of the entire production of the mine.
The first care should be to put as little through the breaker as possible. All that may be judiciously saved—as lump and steamboat—may be kept out of the and all that is already small enough should be passed down to the screens without going through the rolls, since the greater the mass that is rushed through, the greater will be the waste. Even a cargo of prepared coal put through the second time would lose by the operation from one-fifth to one-tenth of its bulk in pea-coal and dirt, depending on the volume with which it was fed into the rolls.
Therefore, only the coal which is required to be reduced should be passed through the breaker, and the rolls should be constructed with as little crushing tendency as Possible. The best breakers we have seen are the "HAWK-BILLED*" rollers, and the
Dickson wrought-iron rolls with steel teeth. The hawk-billed rolls may be made with sharp, chilled teeth, and the Dickson rolls can have the teeth sharpened whenever required.
We think either of these patterns would effect a saving of at least five per cent, over the old form of segments and dull, short, cast-iron teeth. The knife-edged teeth are also better than the old-fashioned square teeth.
To do the large business required in great colliery establishments, it is difficult to find any motion so available for coal-breaking as the rotary. A great many other modes have been suggested and tried, but we have not yet seen any which are so effectual.
There has, however, been very little inventive talent brought to bear on this subject. The fate of the first inventor of coal-breakers is not an encouraging example to others. We think the coal-trade have paid pretty dearly for their opposition to the celebrated breaker patent, however exorbitant its demands, from the fact that we continue to crush our coal to an extent that will be sadly felt when our mines are exhausted, and our mining villages deserted, while mountains of refuse stand as their monuments. Had the inventor been encouraged, we have no doubt the case would have been different, since there is plenty of room for improvement.