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whether it is more economical to heat a building continuously or to allow the

building to cool off and be reheated each time it is to be used.

In the accompanying report, submitted to the American Society of Heating and Ventilating Engineers by a special committee on the subject, a further step has been taken in the formulation of a satisfactory plan for testing house heating boilers. That the method proposed is not to be considered final is indicated by the request of the committee for additional criticisms and suggestions. The principal features of the proposed method are presented herewith.

If your committee understands the work laid out for it correctly it would appear that its recommendations should solely apply to a condition for test which

has to do with the operation of a specific boiler under conditions approaching as nearly as possible those under which the boiler is to be installed. Therefore, the testing of the boiler for such results becomes a comparatively simple operation compared with the generally accepted theory of boiler test that all relations of one part of the boiler to another should be taken into account, that is, ratio of heating surface to grate surface, proportion of direct surface to indirect surface, etc., etc.

While it is of course possible in testing a boiler to take readings which will allow consideration of varying features of design, it is not intended that this report should deal with such refinement of laboratory tests as apply to design or to set forth a rigid form of test to be applied in all instances without variation. This report, therefore, will have to do with only those items which are essential in the proper rating of the boiler for commercial or sales purposes.

It is recognized that conditions in individual testing stations may be such as to be more practical with one form of apparatus than with another, but it is our hope that we can submit a general plan which will cover the correct principles and will serve the needs in a practical way. We shall therefore confine our remarks to a code for testing boilers which will have for a specific object the

determination of the amount of steam which a boiler will furnish when burning a definite quantity of coal per hour for a given number of hours without attention to the fire, and under a fixed condition of draft tension. In other words, this code will cover what we believe to be performance conditions.

THREE SERIES OF TESTS NECESSARY ON EACH BOILER.

house-heating boiler is generally run under varying conditions. Therefore, any series of tests which are made should

It should be borne in mind that a

take this fact into account and it would seem that to obtain the proper working capacity of a boiler there should be at

leats three series of tests made on each. First, one series under maximum draft conditions burning the fuel out in as short a time as possible. Second, one so run as to burn out the fuel in a definite or fixed number of hours, as nearly as possible. Third, one with drafts regulated so that slow combustion rate shall maintain, this slow rate being such as to hold the fire the longest number of hours possible and yet maintain a constant evaporation.

A sufficient number of tests should be made in each series so as to obtain repeated or confirmatory results. The average evaporation per pound of coal based on those tests the rates of which fall between 6 and 10 hrs. duration would in our opinion form a fair or safe average on which to base the working power of the boiler under actual househeating conditions.

It is of course self-evident that tests with house-heating boilers are of necessity similar in many respects to tests such as are made with power boilers, and therefore to a large extent the methods employed in testing power boilers can be applied to house-heating boilers. In house-heating boilers conditions relating to attendance, cleanliness and method of operation are of prime importance.

It has been the practice for many years for manufacturers of house-heating boilers to rate their boilers on their capacity expressed in square feet of direct radiation or its equivalent, as it is generally desired to estimate the amount of square feet in direct radiation or its equivalent that can be supplied continuously with steam without attention to the boiler for an extended period of time. It is evident that within certain limits the amount of water evaporated per pound of coal would not vary to any considerable extent and within these limits a definite amount of fuel consumed in a short period of time would serve more condensing surface than if the same amount of fuel were burned during a long period of time.

It has seemed to the commitee that in order to have a uniformity in the matter of codes, so far as possible, it would be wise to adopt the general scheme and arrangement as indicated by the American Society of Mechanical Engineers, and, therefore, reference will be made to the code of that society where our suggestions for code precisely agree with the code of that society.

APPARATUS AND INSTRUMENTS.

The apparatus and instruments used in testing should include the following: Feed water tanks calibrated or to be used in connection with weighing scales; air pump, if water is to be fed by compressed air; weighing scales for weigh ing fuel, ashes, etc.

Differential (Ellison) draft gauges, at least three in number for measuring draft tension, in ashpit, over the fire and in the smoke pipe:

Accurately calibrated thermometers for measuring temperature of escaping gases, feed water, and temperature of

The use of the various instruments is very well set forth in the report of the Power Test Committee of the A.S.M.E. and it would seem needless to repeat same in this report.

RULES FOR CONDUCTING EVAPORATIVE
TESTS.

Inasmuch as the object of the test is to ascertain the amount of water evaporated per pound of coal fired, all measurements and readings should be taken. in such way as to give this result.

The boiler should be set up connected to a suitable chimney flue.

The boiler should be thoroughly boiled out with a solution of sal soda, potassium hydrate, or sodium hydrate and then thoroughly rinsed with clean water to remove any foreign matter.

The piping should be connected in such a way that the steam may be carried to a point away from the boiler and piping arranged so that its condensation may not flow back to the boiler itself.

The separator should be attached to the flow pipe and from the bottom of the separator a pipe should be connected in such a way as to form a water seal and with an open end so that surplus water may be conducted into a pail or barrel for weighing at completion of test.

The piping should connect the calibrated water feeding tanks into the return of the boiler, with all necessary and connections, thermometer valves cups, etc. The water should be fed to the boiler continuously from calibrated tanks, thus showing every pound of water that enters the boiler.

Special care should be used in all readings.

Where weighing tanks are used or water is fed by gravity extra precautions should be taken to avoid error in readings.

Three draft gauges suggested as part of the equipment, should be used to determine pressure loss in the ashpit, pressure loss through the fuel, and pressure loss through the flues of the boiler.

The steam pipe from the boiler should be left open to the atmosphere so that the test can be carried on at atmospheric pressure, as we believe that running a boiler under pressure gives no more accurate results as regards capacity and

efficiency than may be obtained by evaporating the water at atmospheric pressure.

FUEL.

In order that proper comparison may be made between tests, it is recommended that anthracite coal, stove-sized, such as Lehigh Valley, be used. In this connection attention is directed to statements covered by the Power Test Committee of the A.S.M.E.

STARTING.

It is recommended that a preliminary fire be made and the boiler run until such time as water in the boiler steams when the preliminary fire will be dumped, the ashpit thoroughly cleaned, and a fresh quantity of wood placed on the grate and kindled. The test shall be considered as starting at the time of firing this second charge of wood. On this charge of wood shall be placed the coal, which, for measure of comparison, should be stove-sized anthracite. The wood shall be considered as having a heating value equal to 40 per cent. of that of an equal weight of coal.

The weight and temperature of the water in the boiler at the start should be recorded.

Against the boiler should be charged. all of the fuel, including the last charge of wood, and at the end of the test the boiler is to be given credit for the unburned fuel and the quantity of water fed to the boiler during the test, less any water thrown out in excess or a quantity represented by the condensation of the pipe and separator.

If water is not brought to the steaming point at the beginning of the test, credit is to be given to the boiler for the heat expended in heating the water. contents of the boiler from the initial temperature to the boiling point at the atmospheric pressure at the time of the

the fire at the end as compared with that at the start would lead to a large degree of error in the actual calculation of the results, for it will be conceded that in small house-heating boilers in burning from 10 to 50 lbs. of coal an hour, 2 or 3 lbs. of fuel would make quite a difference in the results, while it would be almost impossible for the eye to determine such a small difference. Further than this it would prevent tests from repeating, that is, in running a series of tests a sufficient number should be made so as to get confirmatory results or until the results repeat very closely.

It is of course to be expected that no two tests will be exactly alike, but within certain limit tests should be conducted until they confirm one another. If there is a great difference between tests it is undoubtedly a sign that either false readings have been made, chimney conditions are not right, or that mistake has been made in calculation.

Readings should be taken at not to exceed 30-min, intervals, while draft and stack temperatures should be taken at 15-min. intervals.

Gas analysis should be made at least. every hour to get fair average results.

STOPPING.

When the time set for the end of the test arrives the fire should be dumped or combustion stopped by some other method such as spraying the fire with water. The contents of the firepot when dumped should be placed in tightly covered cans where they may be left to cool.

After cooling, the unburned coal and ash should be separated, the unburned coal weighed and deducted from the total quantity of fuel fed to the boiler. A proximate analysis of the coal should be made in order to determine its various constituents.

The subjects, "records," "sampling and drying coal," "ashes and refuse," "calorific test and analysis of coal," "analysis of flue gases," "smoke observations," "calculation of results," are all covered so clearly in the report of the Power Test Committee of the A.S.M.E. that we would refer to them without extending this report to quote them verbatim.