r through burning
in patches, nothing can be done to remedy it until the fire is cleaned
as a whole. After this grade of fuel has been fired it should be left
alone, and the fire tools used as little as possible. Owing to the
difficulty of igniting this fuel, care must be taken in cleaning fires.
The intervals of cleaning will, of course, depend upon the nature of the
coal and the rate of combustion. With the small sizes and moderately
high combustion rates, fires will have to be cleaned twice on each
eight-hour shift. As the fires become dirty the thickness of the fuel
bed will increase, until this depth may be 12 or 14 inches just before a
cleaning period. In cleaning, the following practice is usually
followed: The good coal on the forward half of the grate is pushed to
the rear half, and the refuse on the front portion either pulled out or
dumped. The good coal is then pulled forward onto the front part of the
grate and the refuse on the rear section dumped. The remaining good coal
is then spread evenly over the whole grate surface and the fire built up
with fresh coal.

A ratio of grate surface to heating surface of 1 to from 35 to 40 will
under ordinary conditions develop the rated capacity of a boiler when
burning anthracite buckwheat. Where the finer sizes are used, or where
overloads are desirable, however, this ratio should preferably be 1 to
25 and a forced blast should be used. Grates 10 feet deep with a slope
of 1-1/2 inches to the foot can be handled comfortably with this class of
fuel, and grates 12 feet deep with the same slope can be successfully
handled. Where grates over 8 feet in depth are necessary, shaking grates
or overlapping dumping grates should be used. Dumping grates may be
applied either for the whole grate surface or to the rear section. Air
openings in the grate bars should be made from 3/16 inch in width for
No. 3 buckwheat to 5/16 inch for No. 1 buckwheat. It is important that
these air openings be uniformly distributed over the whole surface to
avoid blowing holes in the fire, and it is for this reason that
overlapping grates are recommended.

No air should be admitted over the fire. Steam is sometimes introduced
into the ashpit to soften any clinker that may form, but the quantity of
steam should be limited to that required for this purpose. The steam
that may be used in a steam jet blower for securing blast will in
certain instances assist in softening the clinker, but a much greater