A Rudimentary Treatise on Steam Boilers Author:Robert Armstrong Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Section 12.—On Enlarging The Furnace And LengthenIng The Boiler. When a wagon boiler is found to have insufficient power, it frequently admits of a very effec... more »tual remedy by lengthening the fire bars; and when the seating walls are unnecessarily thick, by widening the furnace throughout. A great portion of the brickwork on each side may be removed by supporting the boiler on six or eight cast-iron blocks or short columns, and with merely a brick in breadth wall to divide the flame bed and furnace from the side flue. When this plan is done carefully, it is always followed by a great increase in the evaporating power of the boiler, without requiring any great addition to the area of the fire grate. Fig. 4. In effecting this alteration care must be taken that the enlargement of the fire grate does not injure the draft, otherwise a contrary effect to that expected has sometimes been produced, particularly where the chimney is small and no surplus draft at command. In such a case it is necessary to diminish by a small amount some of the spaces betweei the grate bars, in order that the total area of draft space may not be increased in so great a proportion as the areand of the grate iteelf. The easiest way of effecting this is to chip or plane off one side of the heads of each of about half a dozen bars at the sides of the grate, leaving the largest draft spaces towards the centre of the fire; and if there are two lengths of bars, confine the operation to the first length, by which means the combustion will be more rapid where otherwise the coals are apt to accumulate. It has been already remarked that the evaporating power of a boiler is always found to be, other things remaining the same, in proportion to the area of the fire grate; and to this may be added, the evapo...« less