Determine the character of fuel to be used.[62] For tests of maximum
efficiency or capacity of the boiler to compare with other boilers, the
coal should be of some kind which is commercially regarded as a standard
for the locality where the test is made.
In the Eastern States the standards thus regarded for
semi-bituminous coals are Pocahontas (Va. and W. Va.) and New
River (W. Va.); for anthracite coals those of the No. 1
buckwheat size, fresh-mined, containing not over 13 per cent ash
by analysis; and for bituminous coals, Youghiogheny and
Pittsburgh coals. In some sections east of the Allegheny
Mountains the semi-bituminous Clearfield (Pa.) and Cumberland
(Md.) are also considered as standards. These coals when of good
quality possess the essentials of excellence, adaptability to
various kinds of furnaces, grates, boilers, and methods of
firing required, besides being widely distributed and generally
accessible in the Eastern market. There are no special grades of
coal mined in the Western States which are widely and generally
considered as standards for testing purposes; the best coal
obtainable in any particular locality being regarded as the
standard of comparison.
A coal selected for maximum efficiency and capacity tests, should be the
best of its class, and especially free from slagging and unusual
clinker-forming impurities.
For guarantee and other tests with a specified coal containing not more
than a certain amount of ash and moisture, the coal selected should not
be higher in ash and in moisture than the stated amounts, because any
increase is liable to reduce the efficiency and capacity more than the
equivalent proportion of such increase.
The size of the coal, especially where it is of the anthracite class,
should be determined by screening a suitable sample.