1. Rationale
Note 1 in ASTM C 737 is not consistent with the language in 30 CFR 75.403. Specifically the CFR states that ". . .the incombustible content of the combined coal dust, rock dust, and other dust shall be not less than 65 per centum, but the incombustible content in return aircourses shall be no less than 80 per centum." The CFR only refers to incombustible content; it does not require a specific limestone content as claimed in Note 1. Although limestone may be the most common rock dust used in coal mines, other materials may also be used as rock dusts. The incombustible content includes moisture, ash from the coal, rock dust (usually limestone), plus any other incombustible dust naturally present in the mine (such as from the roof or floor rock). The language in C 737 should be consistent with the language in 30 CFR 75.403.
Keywords
coal mines; dolomitic limestone; high calcium limestone; limestone; limestone dust; mine explosions; moisture content; silica content;
Citing ASTM Standards
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