"STARTING AND STOPPING A TEST.—IX. A test should last at least ten hours of continuous running, and twenty-four hours whenever practicable. The conditions of the boiler and fur nace in all respects should be, as nearly as possible, the same at the end as at the beginning of the teat. The steam pressure should be the same, the water-level the same, the fire upon the grates should be the same in quantity and condition, and the walls, flues, etc., should be of the same temperature. To secure as near an approximation to exact uniformity as possible in conditions of the fire and in temperatures of the walls and flues, the knowing method of starting and stopping a test should be adopted: "X. Standard being raised to the working pressure, remove rapidly all the fire from the grate, close the damper, clean the ash-pit, and as quickly as possible start a new fire with weighed wood and coal, noting the time of starting the test and the height of the water-level while the water is in a quiescent state, just before lighting the fire. At the end of the test, remove the whole fire, clean the grates and ash-pit, and note the water-level when the water is in a quiescent state: record the time of hauling; the fire as the end of the test. The water-level should be as nearly as possible the same as at the beginning of the test. If it is not the same, a correction should be made by computation, and not by operating pump after test is completed. It will generally be necessary to regulate the discharge of steam from the boiler tested by means of the stop-valve for a time while fires are being hauled at the be ginning and at the end of the test, in order to keep the steam pressure in the boiler at those times up to the average during the test.
"XI. Alternate of the standard method above described, the following, may be employed where local conditions render it necessary: At the regular time for slicing and cleaning fires, have them burned rather low, as is usual before cleaning. and then thor oughly cleaned; note the amount of coal left on the grate as nearly as it can be estimated; note the pressure of steam and the height of the water-level—which should be at the medium height to he carried throughout the test—at the same time; and note this time as the time of starting the test. Fresh coal, which has been weighed, should now be fired. The ash-pits should be thoroughly cleaned at once after starting. Before the end of the test the fires should be burned low, just as before the start, and the fires cleaned in such a manner as to leave the same amount of fire, and in the same condition, on the grates as at the start. The water-level and steam pressure should be brought to the same point as at the start, and the time of the ending of the test should be noted just before fresh coal is fired.
" Duarm THE TEST.—XII. Keep the Conditions boiler should be run con tinuously, without stopping for meal-times or for rise or fall of pressure of steam due to change of demand for steam. The draft being adjusted to the rate of evaporation or com bustion desired before the test is begun, it should be retained constant during the test by means of the damper. If the boiler is not connected to the same steam-pipe with other boilers,
an extra outlet for steam with valve in same should he provided, so that in Vase the pressure should rise to that at which the safety-valve is set it may be reduced to the desired point by opening the extra outlet without checking the fires. If the boiler is connected to a main steam-pipe with other boilers, the safety-valve on the boiler being tested should be set a few pounds higher than those of the other boilers, so that in ease of a rise in pressure the other boilers may blow off, and the pressure be reduced by closing their dampers. allowing the damper of the boiler being tested to remain open, and firing as usual. All the conditions should be kept is nearly uniform as possible, such as force of draft, pressure of steam, and height of water. The time of cleaning the fires will depend upon the character of the fuel, the rapidity of combustion, and the kind of grates. When very good coal is used, and the combustion not too rapid, a ten-hour test may be run without any cleaning of the grates, other than just before the beginning, and just before the end of the test. But in ease the grates have to be cleaned during the test, the intervals between one cleaning and :mother should be uniform.
" XIII. Keeping the coal should be weighed and delivered to the firemen XiiiI. Keeping the coal should be weighed and delivered to the firemen in equal portions, cavil sullieient for ;Jima one hour's ruin, and a fresh Portion should not be delivered mail the previous one hes all been fired. The time required to consume each port ion should be noted, the time being reeorded at the instant of firing the first of each new portion. It is desirable that at the time the amount of water fed into the boiler should be accurately noted and recorded, including the height of the water in the boiler. and the average pressure of steam and temperature of feed during the time. By thus recording the amount of water evaporated by successive portions of coal, the record of the test may be divided into several divisions, if desired, at the end of the test, to discover the degree of uni formity of combustion, evaporation, and economy at different stages of the test.
XIV. Priming Tests.—In all tests in which accuracy of results is important, calorimeter tests should be made of the percentage of moisture in the steam, or of the degree of super heating. At least ten such tests should be made during the trial of the boiler, or so many as to reduce the probable average error to less than 1 per cent, and the final records of the boiler-tests corrected according to the average results of the calorimeter tests. On account of the difficulty of securing accuracy in these tests, the greatest care should he taken in the measurements of weights and temperatures. The thermometers should be accurate to within a tenth of a degree, and the scales on width the water is weighed to within one-hundredth of a pound.