This device is an ingenious mechanism actuated by clock work and the varying pressures of steam formed within the boiler; it records the time and the pressure upon a revolving roll of paper and preserves an accurate account of the varying conditions which have existed within the boiler.
Fig. 105.
The advantages derived from its use may be thus summarized: 1, It is a monitor constantly teaching the fireman to be careful to maintain an equal pressure of steam. 2, This uniform steam made possible by the use of the gauge is productive of the greatest possible economy. 3, The even strain maintained insures a long life to the boiler and a minimum of repairs. 4, It is the vindication of an attentive and careful fireman and allows him due credit for his skill and faithfulness, which is too often ill appreciated for lack of a reliable record.
Although described as a boiler room fixture, where it is frequently found in position, the proper place for this admirable device is in the steam user’s office, thus establishing a nerve connection, between engineer and owner, relating to the safety and economy of the power-plant to their mutual great advantage.
HORSE POWER AS APPLIED TO BOILERS.
By general agreement a horse power as applied to steam boilers is thirty (30) pounds of feed water at a temperature of 100 degrees Fahr. converted into steam in 1 hour at 70 pounds gauge pressure.
The standard is all that can be asked because the same test will determine two things; first the steam making capacity of the boiler and second its evaporative efficiency, which is all that is necessary to know in determining the commercial rating of boilers.
But it is a fact that, without an engine attached, there is no such thing as calculating the horse power of a boiler upon general principles. A well constructed engine with a given pressure of steam upon a piston of a given area and moving at a certain velocity in feet per minute, will always and under all conditions develop the same power so long as the boiler is able to furnish a sufficient quantity of steam to keep up that pressure; and it matters not whether the steam is taken from a boiler rated at 60 horse power or 30.
An evidence of the fact that there is no standard rule for calculating the horse power of boilers that can be depended upon, is that no two engine builders send out the same sized boilers with the engine of the same rated power. Experience has taught them that to furnish steam sufficient to work their engines up to their ratings that a certain sized boiler is required, and what would be considered 30 horse power by one manufacturer might be considered 35 or more by another—the difference being in the economy of the engine of using the steam, and not in the boiler for making it.