With London water, boilers that are in ordinary daily use should be cleaned out every 6 months to keep them in really good order, but to avoid the trouble of remembering dates, &c., many good firms keep a register for this work.
The most important places in the boiler that need cleaning are the parts immediately where the fire plays, especially the angles, where the boiler plates are welded or joined—and careless workmen are apt to neglect these parts—as the deposit is very hard and stone-like at these places.
It may be said without exaggeration that three-fourths of the fractures that occur to wrought-iron boilers are due to excessive incrustation, i.e. want of regular cleaning or removal of deposit.
Incrustation does not occur (but to an extremely small extent) in boilers used for heating purposes only, as in this instance the same water is heated over and over again, and water only contains a certain quantity of lime in solution, which is all deposited when it first boils.
It might be mentioned that in some places the deposit is organic matter, and is found in the boiler much resembling a layer of mud; in such instances the water should be filtered for obvious reasons.
The tank, cylinder and pipes, and in fact the whole apparatus (excepting the boiler) will be rendered more efficient by being covered with some non-conducting material to prevent loss of heat by radiation. Radiation is an important feature occasionally, as very many instances are known of apparatus being a complete failure, solely by reason of the tank or pipes (or both) being in very cold situations (cold draughty roofs, stone passages, &c., &c.); and a moment’s reflection shows that loss of heat is really loss of fuel attended with certain inconveniences well known to many who are suffering with this trouble. The common non-conducting material used is felt in its various forms. Hair felt is the best, as will be readily understood, and can be obtained at many ironmongers and may be applied by any one; for pipes it should be cut and put on in strips, wound round spirally, and tied. Another method is to encase the tank and pipes and pack the casing with a non-conducting material, such as cow hair, slag wool, sawdust, &c., but it is most necessary that the casing be packed, otherwise the heated pipes will render the casing a flue which will draw in cold air and very materially assist in cooling the water, especially if the casing has open or badly fitted ends, in which case failure of the apparatus can be confidently anticipated.
In addition to the heat-saving properties, this covering also possesses the advantages of keeping the different places cool (an advantage for certain seasons only, excepting the kitchen) and saves the pipes from attack of frost, and under ordinary circumstances, if a small fire is left at night with the boiler flue closed, moderately warm water can be had for bathing before the fire is lighted in the morning; these two latter advantages are perhaps the greatest.
In reference to this subject, it is a great convenience if the range (if the boiler is in a range) is provided with a means of opening the fire, as, with an open fire a small quantity of fuel can be placed on it the last thing at night and it will burn in safety for a considerable time, and really hot water can by this means be obtained at an early hour in the morning if the apparatus is “insulated” as explained above.
If the felt is placed round the pipes and tank without casing it should be one or two layers thick, say about ½ in., so that the hand can scarcely perceive any heat when the apparatus is in full action; a single layer of felt will answer, but not so perfectly.
Boiler explosions are at all times most serious disasters, for not only is the damage very great, but if any living thing is moderately near at the time the result is almost certain to be fatal, and it is a much-regretted fact that three-fourths or nearly all the terrible accidents of this kind could have been avoided with ordinary care; the reason that this form of accident is so serious is that before the explosion takes place, the steam has to attain sufficient power to burst the boiler, which is from ¼ to ½ inch thick of wrought iron, compared to which the human body is a frail object, and suffers accordingly.