Maxims and Instructions for the Boiler Room / Useful to Engineers, Firemen & Mechanics; Relating to Steam Generators, Pumps, Appliances, Steam Heating, Practical Plumbing, etc.

by N. Hawkins

Note.

These descriptions and illustrations of the Lancashire boiler are of general value, owing to the fact that very many exhaustive tests and experiments upon steam economy have been made and permanently recorded in connection with this form of steam generator.

In the Galloway form of boiler the flue is sustained and stiffened by the introduction of numerous conical tubes, flanged at the two ends and riveted across the flue. These tubes, a sketch of which are given in [fig. 18 (a)], are in free communication with the water of the boiler, and besides acting as stiffeners, they also serve to increase the heating surface and to promote circulation.

Figs. 19, 20.

The illustration (figs. [18], [19 and 20]) give all the principal details of a Lancashire boiler fitted with Galloway tubes. [Fig. 18] represents a longitudinal section and [figs. 19 and 20] shows on a large scale an end view of the front of the boiler with its fittings and also a transverse section. The arrangement of the furnaces, flues, and the Galloway tubes is sufficiently obvious from the drawings. The usual length of these boilers is 27 feet, though they are occasionally made as short as 21 feet.

The minimum diameter of the furnaces is 33 inches, and in order to contain these comfortably the diameter of the boiler should not be less than 7 feet. The ends of the boiler are flat, and are prevented from bulging outwards by being held in place by the furnaces and flues which stay the two ends together and also by the so-called gusset stays e, e. In addition to the latter the flat ends of the boiler have longitudinal rods to tie them together; one of these is shown at A, A, [fig. 18].

The steam is collected in the pipe S, which is perforated all along the top so as to admit the steam and exclude the water spray which may rise to the surface during ebullition. The steam thence passes to the stop valve T outside the boiler and thence to the steam pipes to the engines.

There are two safety valves on top of the boiler on B ([fig. 18]), being of the dead weight type described hereafter, and the other, C, being a so-called low water safety valve. It is attached by means of a lever and rod to the float F, which ordinarily rests on the surface of the water. When through any neglect, the water sinks below its proper level the float sinks also, causing the valve to open, thus allowing steam to escape and giving an alarm. M is the manhole with its covering plate, which admits of access to the interior of the boiler and H is the mud hole by which the sediment which accumulates all along the bottom is raked out. Below the front end and underneath, the pipe and stay valve are shown, by which the boiler can be emptied or blown off.

On the front of the boiler ([fig. 19]) are shown, the pressure gauges, the water gauges and the furnace door; K is the feed pipe; R, R, a pipe and cock for blowing off steam. In the front of the setting are shown two iron doors by which access may be gained to the two lower external flues for cleaning purposes.

In the Lancashire boiler it is considered advisable to take the products of combustion, after they leave the internal flues, along the bottom of the boiler, and then back to the chimney by the side. When this plan is adopted the bottom is kept hotter than would otherwise be the case, and circulation is promoted, which prevents the coldest water from accumulating at the bottom.

The Galloway (or Lancashire) boiler is considered the most economical boiler used in England, and is being introduced into the United States with success. The long traverse of heat provided (three turns of about 27 feet each) contributes greatly to its efficiency.

It may be useful to add the following data relating to this approved steam generator, being the principal dimensions and other data of the boiler shown in [fig. 18]:

Steam pressure, 75 lbs. per sq. inch.
Length, 27 feet.
Diameter, 7 feet.
Weight, total, 151⁄2 tons.
Shell plates, 7⁄16 inch.
Furnace diameter, 33 inches.
Furnace Plates, 3⁄8 inch.
End plates, 1⁄2 inch.
Grate area, 33 sq. feet.
Heating surface:
In furnace and flues	450	sq. feet.
In Galloway pipes,	30	„
In external flues,	370	„
	850	sq. feet.

We have thus detailed step by step the improvement of the steam boiler to a point where it is necessary to describe at length the locomotive, the marine, the horizontal tubular and the water tube boilers, which four forms comprehend ninety-nine out of one hundred steam generators in use in the civilized world at the present time.