Function of A Coal Breaker
The first function of a coal breaker is to break coal into pieces and sort these pieces into categories of nearly uniform size, a process known as breaking. The second function of a coal breaker is to remove impurities (such as slate or rock), and then grade the coal on the basis of the percent of impurities remaining. The sorting by size is particularly important for anthracite coal. In order to burn efficiently, air must flow evenly around anthracite. Subsequently, most anthracite coal is sold in uniform sizes. In the 1910s, there were six commercial sizes of coal (with the smallest size having three subsets):
- Steam - 4.5 to 6 inches in size (primarily used as steamship fuel).
- Broken - 3.25 to 4.5 inches in size.
- Egg - 2.25 to 2.3 inches in size.
- Stove - 1.5 to 1.625 inches in size (primarily used for use in home cooking stoves).
- Chestnut - 0.875 to 0.9375 inches in size.
- Pea - 0.5 to 0.625 inches in size. There were three subsets of "pea coal":
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- No. 1 Buckwheat - 0.25 to 0.3125 inches in size.
- No. 2 Buckwheat - 0.1875 inches in size.
- No. 3 Buckwheat - 0.09375 to 0.125 inches in size.
Coal pieces smaller than 0.09375 inches in size were considered "culm," and unable to be separated from the impurities (and thus useless). The grade of coal ranged from a low of 5 percent impurities for steam or broken coal to a high of 15 percent for pea-size coal and its subsets.
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