A place is also given for a signature to be appended by the one responsible for the weight notation.

Log Sheet for the Fuel Oil Fed to Furnace.-Simultaneously with the weighing of the water, a similar log sheet is kept by another set of observers setting forth the weight of fuel oil fed to the furnace. As the weighing proceeds, a periodic sample is taken to make up a composite sample for the detemination of the calorific value of the oil as set forth in the preceding chapter. The log sheet for the oil is quite similar to that used for the water and should be footed up at the end of each hourly period so that the engineer may have some definite idea of preliminary economic results. A suggestion for this log sheet is as follows:

Other Data to be Taken.-The tabulation of data to determine the steam used for atomization and the analysis of the flue gases require special treatment, depending upon the particular method decided upon by the engineer to ascertain these factors. Pre

vious chapters have already set forth in detail suggestions for the ascertaining of these quantities, and the reader is now advised to re-read them in order to correlate in his mind, as it were, all the data, that must be taken in order to ascertain the economic performance of the modern boiler utilizing crude petroleum as a fuel.

FIG. 196. The graphic log sheet for fuel oil tests.

During the progress of a test a graphic plot most conveniently sets forth the behavior of the variables under observation. The above shows a typical graphic log sheet and its method of construction for fuel oil tests.

The General Log Sheet. In addition to the two log sheets just described, a general log sheet is necessary upon which to note the temperatures, pressures, flue gas analysis and other information desired.

Here is an illustration of a suggestion for such a log sheet. At the completion of the test an average is easily obtained for

the various readings by footing up the total and dividing by the number of readings noted. The columns for the water fed to the boiler and the oil fed to the furnace are footed and as in the hourly sheets previously described, the totals from these sheets which are noted on this general log sheet should now check-that is, the total gross should equal the sum of the total tare and total net columns. The reader is to bear in mind that the actual notations to be made in any particular test are not all set down in this general log sheet suggestion, for the information desired and the purpose of the test must in each given case determine these factors. The sheet will, however, serve as a general guide for such matters.

The Plotting of Test Data.-As the test proceeds hour by hour, it is very instructive and helpful to keep a diagrammatic log sheet also. By this means a glance will often reveal certain irregularities that may be righted at their incipiency. Such a log sheet is shown in Fig. 196 and by reference to it the reader will observe how the history of a test may be simply and clearly set forth.

CHAPTER XXXVIII

THE HEAT BALANCE AND BOILER EFFICIENCY

The steaming qualities of a boiler are best set forth by measuring its so-called efficiency. The efficiency of a boiler is the relationship between the heat absorbed per pound of fuel fired and the calorific value of 1 lb. of fuel. Thus although each pound of fuel consumed in steam production is found to have a calorific value of 19,450 B.t.u. in the numerical illustration for this chapter, that portion alone of this heat which is actually represented in the steam itself is of economic value.

In the illustrative test which is made use of throughout this chapter, it will be found that of this 19,450 B.t.u. represented in each pound of oil only 14,076.56 go toward power generation. It is then useful and instructive to analyze the losses in a boiler and see through what channels this heat has been dissipated. The major portion of these losses may be easily computed by means of data taken in the test. Those which cannot be mathematically computed are thrown under the column entitled "Stray Losses," and are made to represent such an amount that the total losses together with the useful heat generated in the boiler represent the heat from 1 lb. of fuel.

Let us then examine the various channels of heat transfer going on in the boiler and see how the details of the heat balance are set forth. In this discussion H. will represent the calorific value of 1 lb. of fuel oil under test.

(a) a. The Total Heat Absorbed by the Boiler.-As has been previously shown, the equivalent evaporation of a boiler per pound of oil represents the number of pounds of water which would be evaporated into steam per pound of oil if the water was at 212°F. and under atmospheric pressure, and this water then converted into dry saturated steam at the same temperature and pressure. It is self-evident then that the total heat absorbed by the boiler for each pound of oil burned in the furnace is equal to the equivalent evaporation multiplied by the heat necessary to convert 1 lb. of water into steam under conditions just mentioned.