Accucraft trains D&RGW K-28 COAL FIRED Instruction Manual - page 7
D&RGW K-28 COAL FIRED MANUAL
7
Selecting Coal, Water And Oil
Your selection of coal , water and oil will contribute as much to the success of your coal firing experience as your
firing technique.
Coal
A discussed above, coal is a complex compound and comes in many “flavors.” Coal falls into 4 basic classifica
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tions, anthracite is a hard, shiny coal with a high heat content; in excess of 15,000 BTU per pound, and a carbon
content of 85 to 95%. Next down the scale is bituminous. It is softer, has less carbon, 45 to 85%, has a heat
content of 10,500 to 15, 000 BTUs, and has less sulphur. Following this is sub-bituminous coal which contains
upwards of 50% carbon, has a heat con lent between 8,000 and 13,000 BTU per pound, is softer and dull col-
ored. On the bottom is lignite which is totally unsuitable for our purposes. All of these have other characteristics,
depending upon their impurities and how they were formed millions of years ago, which impact their ability to be
used in the small fireboxes of gauge one locomotives. These characteristics are less dependent upon their basic
classification and more dependent upon the specific mine the coal comes from. Just because it is being used by
some power company in a generating plant, does not mean it is suitable for our small firebox boiler.
Anthracite, bituminous and sub~bituminous coals can all be suitable for our uses. The single most important char-
acteristic for our consideration is their ash content and their ash fusion temperature. Coals with high ash content
and low ash fusion temperatures are prone to clinkering, clogging grates and forming masses that can blanket the
bed of coal. In our small fireboxes this is especially problematic. As mentioned above, our boilers depend upon a
significant transfer of heat radiantly . Anything which reduces radiant transfer, limits steam production greatly. Our
small boilers also have a limited grate size, and anything that inhibits air flow will also inhibit steam production.
Whether you use anthracite, bituminous or sub-bituminous coal , you need to look for a clean burning coal that
has low ash and is not prone to clinkering. The Welsh steam coal available from Coles’ Power Models falls into
this category. Although it bums relatively fast and needs more continuous stoking than other coals, it burns without
much ash, no smoke, and more importantly it does not form clinker. It is also easy to break up into the smaller
size pieces needed to stoke through the firebox door.
Of the 3 or 4 different coals we have tried. Coles’ has been the most successful and easy to use, as well as the
easiest to clean up afterwards.
Water
“Water, water everywhere, but not a drop to drink.” We have all heard of the plight of the shipwrecked sailor, sur-
rounded by unlimited water, but none of it potable. The same is true with your locomotive. We are all aware of the
need to use “purified water,” but all water on the store shelf is not the same. Your locomotive’s boiler is an assem
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bly of many components that have been joined using a silver brazing compound . These brazing compounds are
atomically different enough from the copper in the boiler plates to be subject to electrolytic decomposition in the
presence of an electrically active fluid. The water used in your boiler needs to be as pure as possible, and within a
relatively narrow range of pH. pH is the measure of the ionic properties of a liquid material which classify it as an
acid or a base. This is measured on a scale from 0 to 14 where 7 is neutral: below 7 is an acid, above 7 is basic.
Acidic solutions have an abundance of H+ (hydrogen) ions while basic solutions are strong in OH (hydroxide
ions.) It is the presence of these ions that makes the fluid electrically conductive. Freshly “STEAM DISTILLED”
water will measure approximately 7. and is ionicly neutral, but with long term exposure to carbon dioxide in the air
slowly will become slightly acidic with pH of around 6; therefore. “the fresher the better.”
We often think of some natural waters as being very pure; for instance rain water, or “Pure Spring Water.” It is true
they may not have significant dissolved solids in them, but their pH can vary from acceptable to miserable, we’ve
all heard of acid rain. Just as we use acids and bases as electrolytes in batteries to pull electrons out of the metal
battery plates, the pH of your water can cause electrolytic effects to take place in your boiler, which can cause the
brazed joints to break down over time.