UNITED STATES FUEL ADMINISTRATION BUREAU OF CONSERVATION Engineering Bulletin No. 1 BOILER AND FURNACE TESTING Prepared by Rufus T. Strohm Associate Editor, Power [Illustration: Maximum Production Minimum Waste] WASHINGTON GOVERNMENT PRINTING OFFICE 1918 ---------------------------------------------------------------------- MAXIMUM PRODUCTION. MINIMUM WASTE. The United States Fuel Administration is making every effort, through the producers and transportation lines, to obtain anadequate supply of fuel for the industries of the country. Twenty-five to fifty million tons of coal a year can be saved bythe improved operation of steam-power plants without changing theirpresent equipment and without abating their production theslightest. It is absolutely necessary that this saving be realized, if ouroverburdened railroads are to be relieved and our industries keptin full operation. The extent to which it will be realized depends upon thecooperation of the owners, engineers, and firemen of every powerplant of the country. YOUR FIRING LINE IS AT THE FURNACE DOOR. DAVID MOFFAT MYERS, _Advisory Engineer to United States Fuel Administration_. ---------------------------------------------------------------------- BOILER AND FURNACE TESTING. By RUFUS T. STROHM. NECESSITY FOR TESTING BOILERS. A boiler test is necessary in order to determine how well theboiler is doing the work expected of it; that is to say, we mustfind out whether we are wasting coal in making steam and how muchthis waste may be. Such a test may be made to discover theefficiency of the boiler, or the quantity of water it isevaporating, or the cost of evaporating 1, 000 pounds of water. The United States Fuel Administration recommends that every boilerplant have some means of daily checking the efficiency of theboiler and furnace. The simplest and best way of finding out howefficiently the boiler is working is to make an evaporation test, as described in this bulletin. All the necessary records can bemade automatically with suitable instruments, although in manysmall plants the coal must be weighed on ordinary scales. Theefficiency of the furnace can be found by making analyses of theflue gases. (See Bulletin No. 2 of the United States FuelAdministration. ) Too many engineers and firemen have the idea that they are notfitted to make boiler tests. This is altogether wrong. Any man whocan weigh water and coal and read steam gages and thermometers isable to do the work required in making a boiler test forevaporation or efficiency. Such a test requires a knowledge of thefollowing: 1. The total weight of coal used. 2. [1]The total weight of water fed to and evaporated by the boiler. 3. The average temperature of the feed water. 4. The average steam pressure in the boiler. If these four items are known, a series of simple calculations willshow how much water is being evaporated per pound of coal, and theefficiency of the boiler and furnace. To make a test, the following apparatus and instruments arenecessary: 1. Scales to weigh the coal. 2. Apparatus to weigh or measure the feed water. 3. Thermometers to take feed-water temperature. 4. Gages to indicate steam pressure. A boiler test to be of value should extend over a period of atleast eight hours. The longer the test the more accurate theresults. [Footnote 1: For the sake of simplicity, only the essentialelements of boiler and furnace testing are treated in thisbulletin. For rules covering the refinements for an exhaustivetest, the reader is referred to the boiler test code of theAmerican Society of Mechanical Engineers. Copies of this code canbe obtained from the secretary, 29 West Thirty-ninth Street, NewYork City. ] WEIGHING THE COAL. The weight of coal used during a test may easily be found by usingan ordinary wheelbarrow and a platform scales, arranged as infigure 1. At each side of the scales build an incline with its toplevel with the top of the platform, but take care not to haveeither one touch the platform. Set the empty wheelbarrow on thescales, run the movable weight or poise out until it exactlybalances the weight of the barrow and lock it in position with thethumbscrew. Next, put weights on the scale pan _A_ to correspond to a netweight of 250 or 300 pounds of coal. Fill the barrow with coal, runit on the scales, and add coal or take off coal until the scalesbalance. This is easily done by having a small pile of coal _B_beside the scales. If the weights on the scale pan represent, say, 300 pounds, the net weight of coal in the barrow is exactly 300pounds. This coal is wheeled in front of the boiler and dumped onthe clean floor, and the barrow is returned for another load. [Illustration: _Fig. 1. _ 1 _Set to balance tare of wheelbarrow_2 _Add to balance net weight of coal_] Each time the barrow of coal is weighed on the scales and taken tothe boiler being tested, a tally mark should be made on a boardnailed to the wall beside the scales. Each tally mark represents300 pounds of coal, since the amount of coal in the barrow isadjusted at each weighing, so that the scales just balance. At theend of the test, therefore, the number of tally marks is multipliedby 300, and the product is the weight of coal used, provided it hasall been fired; but if any coal remains in front of the boiler atthe close of the test, it must be gathered up and weighed, and itsweight must be subtracted from the total weight indicated by thetally marks to get the number of pounds of coal actually fired. Youshould, of course, start the test with no coal in front of theboiler. Care must be taken not to forget to make a tally mark each time abarrow of coal is run off the scales. By setting the scales so asto show any net weight, such as 250 or 300 pounds, and making eachbarrow load exactly this weight, much time is saved, as it isunnecessary to change any of the weights or the position of therider on the scale beam. If the coal used in the test is to be analyzed, take a sample offrom 4 to 6 pounds from each barrow and throw it into a box nearthe scales. Do this _before_ the coal is weighed. These smallamounts from the various barrow loads will then give a fair averagesample of the coal used during the test. The condition of the furnace should be the same at the end of thetest period as at the start. Therefore, at the moment the test isbegun, observe the thickness of the fuel bed and the condition ofthe fire. If the fire was cleaned, say, an hour before the testbegan, see that it is cleaned an hour before the time when the testis scheduled to end. If the coal was fired, say, eight minutesbefore the test started, the last coal used during the test shouldbe fired eight minutes before the end of the test. The object ofthese precautions is to insure the same conditions at start andfinish, as nearly as possible; otherwise, the coal weighed will notbe the same as the coal consumed. MEASURING THE FEED WATER. The quantity of water fed to the boiler during the test may befound by metering or by weighing. A reliable water meter isrecommended for this work. There are a number of good makes, ofdifferent types, such as: 1. Venturi meter. 2. Weir or V-notch meters. 3. Diaphragm meters. 4. Displacement meters. 5. Water weighers. The best form of meter to use in any particular case depends on thelocal conditions in the plant; but _every plant should be providedwith a permanently installed meter of some type_. The displacementform of meter should be used only with cold water, however. If there is no meter or water weigher in the plant, the feed waterused during the test can be measured by the three-barrelarrangement illustrated in figure 2. Obtain three water-tight barrels, and set two of them closetogether on a platform directly over the third, leaving about 12inches above barrel 3 in which to fit the valves _V_ and thenipples in the bottoms of barrels 1 and 2. Near the top of each ofthe barrels 1 and 2 screw a 1-inch overflow pipe _O_. Run a pipe _P_ from the city main or other source of supply abovebarrels 1 and 2, and put a valve _A_ on the pipe leading to eachbarrel. From barrel 3 run a suction pipe to the feed pump that isto pump water to the boiler to be tested. It is best to have aby-pass from the usual water supply direct to the feed pump, or toanother pump connected to the boiler, so that in case of anytrouble with the testing barrels, the regular operation of theboiler may be resumed without shutting down. The next step is to fill barrels 1 and 2 with water until theyoverflow at _O_. This water should be of practically the sameaverage temperature as that which is to be used during the test. Barrel 3 should be high enough above the feed pump so that the pumpwill handle hot water. Put barrel 3 on a scales, before connectingit to the feed pump, and weigh it. Then let the water from barrel 1run into barrel 3, and weigh again. The second weight minus thefirst weight is the net weight of water run in from barrel 1 and isthe weight of water contained in barrel 1 when filled to theoverflow. The weight of water in barrel 2 when it is filled to theoverflow can be found in like manner. Mark these weights down. [Illustration: _Fig. 2. _] When the net weights are found and barrel 3 is removed from thescales and connected to the feed pump, the apparatus is ready tobegin the test. Start with the level of the water about 1 footbelow the top of the barrel 3, and drive a nail into the barrel tomark this level. When the test is finished, the level should bebrought to the same point, so that the water that has passedthrough barrels 1 and 2 will accurately represent the weight ofwater fed to the boiler during the test. When the test is to begin, stop the feed pump and tie a stringaround the gage glass on the boiler to mark the height of the waterlevel in the boiler. Then start the pump connected to barrel 3. Fill barrels 1 and 2 up to the overflow before the test is started. Then open the valve _V_ on barrel 1 and let the water run intobarrel 3 as fast as the feed pump draws water from barrel 3. Whenbarrel 1 is emptied close its valve _V_ and open its valve _A_ soas to refill it. While barrel 1 is filling empty barrel 2 into barrel 3 in the sameway, and continue to fill and empty barrels 1 and 2 alternately. Inthis way barrel 3 will be kept supplied with water that has beenmeasured in barrels 1 and 2, the net weights of which were foundbefore the test began. Keep a separate tally of the number of timeseach of the barrels 1 and 2 is emptied into barrel 3. At the end ofthe test the number of tallies for each barrel multiplied by theweight of the water that barrel will hold will be the weight ofwater measured in that barrel. The sum of these weights for barrels1 and 2 will be the weight of water used in the test. With a three-barrel arrangement like this, water can be weighedrapidly enough to supply 300 boiler horsepower. Before starting a test make sure that there is no chance for waterto leak into or out of the boiler. See that the blow-off is tight, that there is no drip from gage cocks, and that the feed-lineconnections are tight, so that all the water fed to the boiler willrepresent accurately the amount evaporated during the test. If a meter is used instead of the three-barrel method, makeabsolutely sure that the meter is correct, as the accuracy of thetest depends on the accuracy with which the water measurements aremade. _After a meter is installed, test it to see that it operatescorrectly under the plant conditions. _ The water level in the boiler should be the same at the end of thetest as at the beginning. As the time for stopping the test drawsnear, therefore, try to bring the conditions the same as at thestart. Do not, however, run the feed pump rapidly in the last fewminutes for the test in order to obtain the same water level. Ifthere is a slight difference in level, calculate the weight ofwater it represents and make the necessary correction to the totalweight of water fed. TEMPERATURE OF FEED WATER. Every plant should have a thermometer on the feed line, so as tofind the temperature of the feed water. Preferably, thisthermometer should be of the recording type. If such a form ofthermometer is used during the test, it is unnecessary to take thefeed temperature at stated intervals, as the record will show thevarying temperatures, and so the average feed temperature duringthe test can easily be found. If there is no thermometer in the feed line, take the feed-watertemperature by means of a thermometer hung in barrel 3 (figure 2)by a hook over the edge of the barrel. Read this thermometer everyhalf hour during the test if the feed-water temperature is fairlyuniform; but if it varies considerably, read the thermometer every15 minutes. The object is to obtain the average feed-watertemperature during the test period. Therefore, mark down thetemperatures as read at the stated intervals. At the close of thetest add the readings and divide their sum by the number ofreadings and you will have the average temperature of the feedwater. STEAM PRESSURE. Every boiler is fitted with a steam gage by which the pressure isindicated. It is important that the pressure gage be accurate. Whatis wanted in a test is the average pressure of the steam in theboiler, therefore, observe the pressure at regular intervals, justas with the feed-water temperature, and mark down these gagereadings. The sum of the readings divided by the number of readingstaken will be the average steam pressure during the test. A recording steam gage is best and makes its own readings. WORKING UP THE TEST. After the boiler test has been made, so as to find the weight ofcoal burned, weight of feed water used, feed-water temperature andsteam pressure, the efficiency, the horsepower, and the economymust be obtained by calculation from the test results. The processof figuring the desired results from the test data is called"working up the test. " To illustrate the method used in finding the efficiency, etc. , suppose that the data obtained from the test are as follows: Length of test hours 10 Total weight of coal fired pounds 5, 000 Total weight of water evaporated do. 35, 000 Average temperature of feed water °F 180 Average steam pressure, gage pounds per square inch 100 The efficiency of any process is always a comparison, or ratio, ofthe output to the input. In the case of a steam boiler theefficiency is the percentage of the heat supplied in the coal thatis usefully employed in making steam. The output of the steamboiler is the heat represented by the quantity of water evaporatedby a pound of coal, taking into account the feed temperature andthe steam pressure, and input is the amount of heat contained in apound of the coal used. The efficiency of the boiler is the outputdivided by the input. The heat contained in a pound of coal is called the "calorificvalue" or "heating value" of the coal. It can be found by taking afair average sample of the coal used during the test, as explainedin connection with weighing the coal, and sending the sample to achemist, who will make a calorimeter test to determine its heatingvalue. At the end of the test the sample fuel should be spread out on aclean floor and all lumps broken up, so that no pieces are largerthan 2 inches maximum diameter. Then the gross sample should bevery thoroughly mixed by shoveling, after which it should be spreadout in the form of a square of uniform depth and quartered downuntil a final average sample is obtained for shipment to acompetent chemist, experienced in fuel analysis. (See Bureau ofMines Technical Paper No. 133. ) About 2 quarts of the chemist's sample should be put in air-tighttins or jars for the determination of moisture; the balance of thesample (the total weight of which should be from 10 to 50 pounds, depending on the total weight of coal used in the test) may bepacked in a wooden box lined with paper to prevent splinters frommingling with the sample. A duplicate coal sample should be kept atthe plant to be used in case of loss of the sample sent to thechemist. The Bureau of Mines has published a bulletin or pamphlet giving theanalyses and heating values of the various kinds and grades of coalfrom all parts of the United States. (Bureau of Mines Bulletin No. 22. ) This bulletin can be used to learn the approximate heatingvalue of the coal. Simply find out what district the coal used inthe test came from, and its grade, and then refer to the bulletinto obtain the heating value of the coal. If a chemist can beobtained to make a heat test, however, it is better to use theheating value he determines. Suppose that during the test the coal used was run-of-minebituminous having a heating value of 13, 500 B. T. U. Every pound ofcoal fired, then, carried into the furnace 13, 500 heat units, andthis value therefore is the _input_ to be used in calculating theboiler efficiency. During the test 5, 000 pounds of coal was fired and 35, 000 pounds ofwater was fed and evaporated. This means that 35, 000 ÷ 5, 000 = 7pounds of water was evaporated per pound of coal burned. This isthe "actual evaporation, " and the heat required to evaporate this 7pounds of water is the output to be used in calculating theefficiency. Every fireman knows that it takes more coal, and therefore moreheat, to make steam with cold feed water than with hot feed water;also, that it is somewhat easier to make steam at a low pressurethan at a high pressure. So it is plain that the heat required toevaporate 7 pounds of water into steam depends on two things, namely, (1) the temperature of the feed water and (2) the pressureof the steam in the boiler. From the data of the test, both theaverage feed-water temperature and the average steam pressure areknown, and so it is a simple matter to find out the amount of heatneeded to evaporate 7 pounds of water from the average temperatureto steam at the average pressure. A pound of water at 212° F. Must have 970. 4 B. T. U. Added to it tobecome a pound of steam at 212° F. , or zero gage pressure. Thisvalue, 970. 4 B. T. U. , is called the latent heat of steam atatmospheric pressure, or the heat "from and at 212° F. " It is theheat required to change a pound of water _from_ 212° F. To steam_at_ 212° F. , and is used by engineers as a standard by which tocompare the evaporation of different boilers. In a boiler test the temperature of the feed water is usuallysomething less than 212° F. , and the steam pressure is commonlyhigher than zero, gage. In the test outlined previously, thefeed-water temperature was 180° F. And the pressure was 100 poundsper square inch, gage. It must be clear, then, that the amount ofheat required to change a pound of water at 180° to steam at 100pounds gage pressure is not the same as to make a pound of steamfrom and at 212° F. To make allowance for the differences in temperature and pressure, the actual evaporation must be multiplied by a number called the"factor of evaporation. " The factor of evaporation has a certainvalue corresponding to every feed-water temperature and boilerpressure, and the values of this factor are given in theaccompanying table. Along the top of the table are given the gagepressures of the steam. In the columns at the sides of the tableare given the feed-water temperatures. To find the factor ofevaporation for a given set of conditions, locate the gage pressureat the top of the table and follow down that column to thehorizontal line on which the feed-water temperature is located. Thevalue in this column and on the horizontal line thus found is thefactor of evaporation required. If the feed water has a temperaturegreater than 212° F. , obtain the proper factor of evaporation fromthe Marks and Davis steam tables. Take the data of the test, for example. The average steam pressureis 100 pounds, gage. The average feed-water temperature is 180° F. So, in the table locate the column headed 100 and follow down thiscolumn to the line having 180 at the ends, and the value where thecolumn and the line cross is 1. 0727, which is the factor ofevaporation for a feed-water temperature of 180° F. And a steampressure of 100 pounds, gage. This factor, 1. 0727, indicates that to change a pound of water at180° F. To steam at 100 pounds requires 1. 0727 times as much heatas to change a pound of water at 212° F. To steam at atmosphericpressure. In other words, the heat used in producing an actualevaporation of 7 pounds under the test conditions would haveevaporated 7 × 1. 0727 = 7. 5 pounds from and at 212° F. Hence, 7. 5pounds is called the "equivalent evaporation from and at 212° F. "per pound of coal used. As already stated, it takes 970. 4 B. T. U. To make a pound of steamfrom and at 212° F. Then to make 7. 5 pounds there would be required7. 5 × 970. 4 = 7, 278 B. T. U. This is the amount of heat required tochange 7. 5 pounds of water at 212° F. To steam at zero gagepressure, but it is also the heat required to change 7 pounds ofwater at 180° F. To steam at 100 pounds gage pressure, because 7. 5pounds from and at 212° F. Is equivalent to 7 pounds from 180° F. To steam at 100 pounds. Therefore, the 7, 278 B. T. U. Is the amountof heat usefully employed in making steam per pound of coal fired, and so it is the _output_. Accordingly, the efficiency of theboiler is-- Output 7, 278 ~ Efficiency = ------ = ------ = 0. 54, nearly. Input 13, 500 In other words, the efficiency of the boiler is 0. 54, or 54 percent, which means that only a little more than half of the heat inthe coal is usefully employed in making steam. The chart shown in figure 3 is given to save the work of figuringthe efficiency. If the equivalent evaporation per pound of coal iscalculated and the heating value of the coal is known, the boilerefficiency may be found directly from the chart. At the left-handside locate the point corresponding to the equivalent evaporationand at the bottom locate the point corresponding to the heatingvalue of the coal. Follow the horizontal and vertical lines fromthese two points until they cross, and note the diagonal line thatis nearest to the crossing point. The figures marked on thediagonal line indicate the boiler efficiency. Take the case just worked out, for example. The equivalentevaporation is 7. 5 pounds and the heating value of the fuel is13, 500 B. T. U. At the left of the chart locate the point 7. 5midway between 7 and 8 and at the bottom locate the point 13, 500midway between 13, 000 and 14, 000. Then follow the horizontal andvertical lines from these two points until they cross, as indicatedby the dotted lines. The crossing point lies on the diagonalcorresponding to 54, and so the efficiency is 54 per cent. BOILER HORSEPOWER OR CAPACITY. The capacity of a boiler is usually stated in boiler horsepower. Aboiler horsepower means the evaporation of 34. 5 pounds of water perhour from and at 212° F. Therefore, to find the boiler horsepowerdeveloped during a test, calculate the evaporation from and at 212°F. Per hour and divide it by 34. 5. Take the test previously mentioned, for example. The evaporationfrom and at 212° F. Or the equivalent evaporation, was 7. 5 poundsof water per pound of coal. The weight of coal burned per hour was5, 000 ÷ 10 = 500 pounds. Then the equivalent evaporation was 7. 5 ×500 = 3, 750 pounds per hour. According to the foregoing definitionof a boiler horsepower, then-- 3, 750 Boiler horsepower = ----- = 109. 34. 5 The "rated horsepower" of a boiler, or the "builders' rating, " isthe number of square feet of heating surface in the boiler dividedby a number. In the case of stationary boilers this number is 10 or12, but 10 is very commonly taken as the amount of heating surfaceper horsepower. Assuming this value and assuming further that theboiler tested had 1, 500 square feet of heating surface, its ratedhorsepower would be 1, 500 ÷ 10 = 150 boiler horsepower. It is often desirable to know what per cent of the rated capacityis developed in a test. This is found by dividing the horsepowerdeveloped during the test by the builders' rating. In the case ofthe boiler tested, 109 horsepower was developed. The percentage ofrated capacity developed, therefore, was 109 ÷ 150 = 0. 73, or 73per cent. HEATING SURFACE. The heating surface of a boiler is the surface of metal exposed tothe fire or hot gases on one side and to water on the other side. Thus, the internal surface of the tubes of a fire-tube boiler isthe heating surface of the tubes, but the outside surface of thetubes of a water-tube boiler is the heating surface of those tubes. In addition to the tubes, all other surfaces which have hot gaseson one side and water on the other must be taken into account. Forinstance, in a fire-tube boiler from one-half to two-thirds of theshell (depending on how the boiler is set) acts as heating surface. In addition to this, the surface presented by both heads, below thewater level, has to be computed. The heating surface of each headis equal to two-thirds its area minus the total area of the holescut away to receive the tubes. COST OF EVAPORATION. The cost of evaporation is usually stated as the cost of fuelrequired to evaporate 1, 000 pounds of water from and at 212° F. Tofind it, multiply the price of coal per ton by 1, 000 and divide theresult by the product of the equivalent evaporation per pound ofcoal and the number of pounds in a ton. Suppose that the cost of the coal used in the foregoing test was$3. 60 per ton of 2, 000 pounds. The equivalent evaporation per poundof coal was 7. 5 pounds. Therefore the cost of evaporating 1, 000pounds of water from 180° F. To steam at 100-pound gage, is-- $3. 60 × 1, 000 ------------- = $0. 24, or 24 cents. 7. 5 × 2, 000 TABLE OF TEST RESULTS. After the test has been made and properly worked up, as heretoforedescribed, collect all the results of the test on one sheet, sothat they can be kept in convenient form for reference and forcomparison with later tests. A brief form of arranging the resultsis as follows: 1. Date of test May 20, 1918 2. Duration of test hours 10 3. Weight of coal used pounds 5, 000 4. Weight of water fed and evaporated do. 35, 000 5. Average steam pressure, gauge do. 100 6. Average feed-water temperature °F. 180 7. Factor of evaporation 1. 0727 8. Equivalent evaporation from and at 212° F. Pounds 37, 545 EFFICIENCY. 9. Efficiency of boiler and furnace per cent 54 CAPACITY. 10. Boiler horsepower developed 109 11. Builders' rated horsepower 150 12. Percentage of rated horsepower developed per cent 73 ECONOMIC RESULTS. 13. Actual evaporation per pound of coal pounds 7 14. Equivalent evaporation from and at 212° F. Per pound of coal as fired, pounds 7. 5 15. Cost of coal per ton (2, 000 pounds) $3. 60 16. Cost of coal to evaporate 1, 000 pounds from and at 212° F. $0. 24 HOW TO USE THE TEST RESULTS. The object of working up a test is to obtain a clear idea as to theefficiency of operation of the boiler or its operating cost. Consequently, after the calculations have been made, they should beused as a basis for study with the idea of improving the boilerperformance. Take the matter of boiler efficiency, for example, as found fromthe test mentioned. Its value was 54 per cent. This is altogethertoo low and indicates wasteful operation. The efficiency of ahand-fired boiler ought not to be less than 65 per cent, and it canbe increased to 70 per cent by careful management under goodconditions. The chart in figure 3 can be used to indicate the evaporation thatshould be obtained in order to reach a desired efficiency. Suppose, for example, that it is desired to know how much water per pound ofcoal must be evaporated to produce a boiler efficiency of 65 percent with coal having a heating value of 13, 500 B. T. U. Per pound. Locate 13, 500 at the bottom of the chart, follow the vertical lineuntil it meets the diagonal marked 65 per cent, and then from thispoint follow the horizontal line to the left-hand edge, where thefigure 9 is found. This means that the equivalent evaporation fromand by 212° F. Per pound of coal must be 9 pounds of water. If thesteam pressure is 100 pounds gauge, and the feed-water temperatureis 180° F. The factor of evaporation is 1. 0727, then the actualevaporation must be 9 ÷ 1. 0727 = 8. 36 pounds per pound of coal. Inother words, to increase the efficiency from 54 per cent to 65 percent under the same conditions of pressure and feed-watertemperature, it would be necessary to increase the actualevaporation from 7 pounds to 8. 36 pounds. This would meanpractically 20 per cent more steam from the same weight of coalused. [Illustration: _Heating Value of Coal, in B. T. U. Per Pound_ FIG. 3. ] How to do this will require some study and experimenting on thepart of the fireman or engineer. The three most common reasons forlow-boiler efficiency are (1) excess air, (2) dirty heatingsurfaces, and (3) loss of coal through the grates. _The first ofthese items is the most important of the three. _ In most cases thegreatest preventable waste of coal in a boiler plant is directlydue to excess air. Excess air simply means the amount of air whichgets into the furnace and boiler which is not needed for completingthe combustion of the coal. Very often twice as much air isadmitted to the boiler setting as is required. This extra or excessair is heated and carries heat out through the chimney instead ofheating the water in the boiler to make steam. There are two waysin which this excess air gets into the furnace and boiler setting. First, by a combination of bad regulation of drafts and firing. Thechances are your uptake damper is too wide open. Try closing it alittle. Then, there may be holes in the fire. Keep these covered. The second way excess air occurs is by leakage through the boilersetting, through cracks in the brickwork, leaks around the framesand edges of cleaning doors, and holes around the blow-off pipes. There are also other places where such air can leak in. Take a torch or candle and go over the entire surface of yourboiler setting--front, back, sides, and top. Where the flame of thetorch is drawn inward there is an air leak. Plaster up all airleaks and repair the brickwork around door frames where necessary. You should go over your boiler for air leaks once a month. In regard to best methods of firing soft coal, see Technical PaperNo. 80 of the Bureau of Mines, which may be obtained from yourState Fuel Administrator. Dirty heating surfaces cause low efficiency because they preventthe heat in the hot gases from getting through into the water. Therefore, keep the shell and tubes free of soot on one side andscale on the other. Soot may be removed by the daily use ofblowers, scrapers, and cleaners. The problem of scale and pure feedwater is a big one and should be taken up with proper authoritieson the subject. There are many things that may be done to increase the efficiencyof the boiler and to save coal. For convenience a number of thesepoints are grouped in the following list: WHAT TO DO. | WHY. | 1. Close up all leaks in the boiler | To prevent waste of heat due to setting. | excess air admitted. | 2. Keep shell and tubes free from | To allow the heat to pass easily soot and scale. | into the water. | 3. Use grates suited to the fuel | To prevent loss of unburnt coal to be burned. | through air spaces. | 4. Fire often, and little at a | To obtain uniform conditions and time. | better combustion. | 5. Cover all thin spots and keep | To prevent burning holes in bed fire bed level. | and admitting excess air. | 6. Do not allow clinkers to form | Because they reduce the effective on side or bridge walls. | area of the grate. | 7. Keep the ash pit free from ashes | To prevent warping and burning out and hot clinkers. | of the grates. | 8. Do not stir the fire except when | Because stirring causes clinker necessary. | and is likely to waste coal. | 9. Use damper and not ash-pit doors | Because less excess air is to control draft. | admitted by so doing. | 10. See that steam pipes and valves | Because steam leaks waste heat are tight. | and therefore coal. | 11. Keep blow-off valves tight. | Because leaks of hot water waste | coal. | 12. Cover steam pipes and the tops | To prevent radiation and loss of of boilers. | heat. Make a boiler test under the conditions of operation as they nowexist in your plant. Then make all possible improvements assuggested in this bulletin, make another test afterwards and notethe increase in the equivalent evaporation per pound of coal used. Remember that the _firing line_ in the boiler room can be just aspatriotic and helpful as the _firing line_ at the front. _Table of factors of evaporation. _ ============================================================================ Feed | Steam pressure in pounds per square inch, gauge. Temperature, |--------------------------------------------------------------- °F. | 30 | 50 | 70 | 80 | 90 | 100 | 110 | 120 ------------+-------+-------+-------+-------+-------+-------+-------+------- 32 | 1. 2073| 1. 2144| 1. 2195| 1. 2216| 1. 2234| 1. 2251| 1. 2266| 1. 2279 35 | 1. 2042| 1. 2113| 1. 2164| 1. 2184| 1. 2203| 1. 2219| 1. 2235| 1. 2248 38 | 1. 2011| 1. 2082| 1. 2133| 1. 2153| 1. 2172| 1. 2188| 1. 2204| 1. 2217 41 | 1. 1980| 1. 2051| 1. 2102| 1. 2122| 1. 2141| 1. 2157| 1. 2173| 1. 2186 44 | 1. 1949| 1. 2020| 1. 2071| 1. 2091| 1. 2110| 1. 2126| 1. 2142| 1. 2155 47 | 1. 1918| 1. 1989| 1. 2040| 1. 2060| 1. 2079| 1. 2095| 1. 2111| 1. 2124 50 | 1. 1887| 1. 1958| 1. 2009| 1. 2029| 1. 2048| 1. 2064| 1. 2080| 1. 2093 53 | 1. 1856| 1. 1927| 1. 1978| 1. 1998| 1. 2017| 1. 2033| 1. 2049| 1. 2062 56 | 1. 1825| 1. 1896| 1. 1947| 1. 1967| 1. 1986| 1. 2002| 1. 2018| 1. 2031 59 | 1. 1794| 1. 1865| 1. 1916| 1. 1937| 1. 1955| 1. 1972| 1. 1987| 1. 2000 62 | 1. 1763| 1. 1835| 1. 1885| 1. 1906| 1. 1924| 1. 1941| 1. 1956| 1. 1970 65 | 1. 1733| 1. 1804| 1. 1854| 1. 1875| 1. 1893| 1. 1910| 1. 1925| 1. 1939 68 | 1. 1702| 1. 1773| 1. 1823| 1. 1844| 1. 1862| 1. 1879| 1. 1894| 1. 1908 71 | 1. 1671| 1. 1742| 1. 1792| 1. 1813| 1. 1832| 1. 1848| 1. 1864| 1. 1877 74 | 1. 1640| 1. 1711| 1. 1762| 1. 1782| 1. 1801| 1. 1817| 1. 1833| 1. 1846 77 | 1. 1609| 1. 1680| 1. 1731| 1. 1751| 1. 1770| 1. 1786| 1. 1802| 1. 1815 80 | 1. 1578| 1. 1650| 1. 1700| 1. 1721| 1. 1739| 1. 1756| 1. 1771| 1. 1785 83 | 1. 1548| 1. 1619| 1. 1669| 1. 1690| 1. 1708| 1. 1725| 1. 1740| 1. 1754 86 | 1. 1518| 1. 1588| 1. 1638| 1. 1659| 1. 1678| 1. 1694| 1. 1710| 1. 1723 89 | 1. 1486| 1. 1557| 1. 1608| 1. 1628| 1. 1647| 1. 1663| 1. 1679| 1. 1692 92 | 1. 1455| 1. 1526| 1. 1577| 1. 1597| 1. 1616| 1. 1632| 1. 1648| 1. 1661 95 | 1. 1424| 1. 1495| 1. 1546| 1. 1566| 1. 1585| 1. 1602| 1. 1617| 1. 1630 98 | 1. 1393| 1. 1465| 1. 1515| 1. 1536| 1. 1554| 1. 1571| 1. 1586| 1. 1600 101 | 1. 1363| 1. 1434| 1. 1484| 1. 1505| 1. 1523| 1. 1540| 1. 1555| 1. 1569 104 | 1. 1332| 1. 1403| 1. 1453| 1. 1474| 1. 1492| 1. 1509| 1. 1525| 1. 1538 107 | 1. 1301| 1. 1372| 1. 1423| 1. 1443| 1. 1462| 1. 1478| 1. 1494| 1. 1507 110 | 1. 1270| 1. 1341| 1. 1392| 1. 1412| 1. 1431| 1. 1447| 1. 1463| 1. 1476 113 | 1. 1239| 1. 1310| 1. 1360| 1. 1382| 1. 1400| 1. 1417| 1. 1432| 1. 1445 116 | 1. 1209| 1. 1280| 1. 1330| 1. 1351| 1. 1369| 1. 1386| 1. 1401| 1. 1415 119 | 1. 1178| 1. 1249| 1. 1299| 1. 1320| 1. 1339| 1. 1355| 1. 1370| 1. 1384 122 | 1. 1147| 1. 1218| 1. 1269| 1. 1289| 1. 1308| 1. 1324| 1. 1340| 1. 1353 125 | 1. 1116| 1. 1187| 1. 1238| 1. 1258| 1. 1277| 1. 1293| 1. 1309| 1. 1322 128 | 1. 1085| 1. 1156| 1. 1207| 1. 1227| 1. 1246| 1. 1262| 1. 1278| 1. 1291 131 | 1. 1054| 1. 1125| 1. 1176| 1. 1197| 1. 1215| 1. 1232| 1. 1247| 1. 1260 134 | 1. 1023| 1. 1095| 1. 1145| 1. 1166| 1. 1184| 1. 1201| 1. 1216| 1. 1230 137 | 1. 0993| 1. 1064| 1. 1114| 1. 1135| 1. 1153| 1. 1170| 1. 1185| 1. 1199 140 | 1. 0962| 1. 1033| 1. 1083| 1. 1104| 1. 1123| 1. 1139| 1. 1154| 1. 1168 143 | 1. 0931| 1. 1002| 1. 1052| 1. 1073| 1. 1092| 1. 1108| 1. 1124| 1. 1137 146 | 1. 0900| 1. 0971| 1. 1022| 1. 1042| 1. 1061| 1. 1077| 1. 1093| 1. 1106 149 | 1. 0869| 1. 0940| 1. 0991| 1. 1011| 1. 1030| 1. 1046| 1. 1062| 1. 1075 152 | 1. 0838| 1. 0909| 1. 0960| 1. 0980| 1. 0999| 1. 1015| 1. 1031| 1. 1044 155 | 1. 0807| 1. 0878| 1. 0929| 1. 0950| 1. 0968| 1. 0985| 1. 1000| 1. 1013 158 | 1. 0776| 1. 0847| 1. 0898| 1. 0919| 1. 0937| 1. 0954| 1. 0969| 1. 0982 161 | 1. 0745| 1. 0817| 1. 0867| 1. 0888| 1. 0906| 1. 0923| 1. 0938| 1. 0952 164 | 1. 0715| 1. 0786| 1. 0836| 1. 0857| 1. 0875| 1. 0892| 1. 0907| 1. 0921 167 | 1. 0684| 1. 0755| 1. 0805| 1. 0826| 1. 0844| 1. 0861| 1. 0876| 1. 0890 170 | 1. 0653| 1. 0724| 1. 0774| 1. 0795| 1. 0813| 1. 0830| 1. 0845| 1. 0859 172 | 1. 0632| 1. 0703| 1. 0754| 1. 0774| 1. 0793| 1. 0809| 1. 0825| 1. 0838 174 | 1. 0611| 1. 0683| 1. 0733| 1. 0754| 1. 0772| 1. 0789| 1. 0804| 1. 0817 176 | 1. 0591| 1. 0662| 1. 0712| 1. 0733| 1. 0752| 1. 0768| 1. 0783| 1. 0797 178 | 1. 0570| 1. 0641| 1. 0692| 1. 0712| 1. 0731| 1. 0747| 1. 0763| 1. 0776 180 | 1. 0549| 1. 0621| 1. 0671| 1. 0692| 1. 0710| 1. 0727| 1. 0742| 1. 0756 182 | 1. 0529| 1. 0600| 1. 0650| 1. 0671| 1. 0690| 1. 0706| 1. 0721| 1. 0735 184 | 1. 0508| 1. 0579| 1. 0630| 1. 0650| 1. 0669| 1. 0685| 1. 0701| 1. 0714 186 | 1. 0488| 1. 0559| 1. 0609| 1. 0630| 1. 0648| 1. 0665| 1. 0680| 1. 0694 188 | 1. 0467| 1. 0538| 1. 0588| 1. 0609| 1. 0628| 1. 0644| 1. 0660| 1. 0673 190 | 1. 0446| 1. 0517| 1. 0568| 1. 0588| 1. 0607| 1. 0623| 1. 0639| 1. 0652 192 | 1. 0425| 1. 0497| 1. 0547| 1. 0568| 1. 0586| 1. 0603| 1. 0618| 1. 0632 194 | 1. 0405| 1. 0476| 1. 0526| 1. 0547| 1. 0566| 1. 0582| 1. 0597| 1. 0611 196 | 1. 0384| 1. 0455| 1. 0506| 1. 0526| 1. 0545| 1. 0561| 1. 0577| 1. 0590 198 | 1. 0363| 1. 0435| 1. 0485| 1. 0506| 1. 0524| 1. 0541| 1. 0556| 1. 0570 200 | 1. 0343| 1. 0414| 1. 0464| 1. 0485| 1. 0504| 1. 0520| 1. 0535| 1. 0549 202 | 1. 0322| 1. 0393| 1. 0444| 1. 0464| 1. 0483| 1. 0499| 1. 0515| 1. 0528 204 | 1. 0301| 1. 0372| 1. 0423| 1. 0444| 1. 0462| 1. 0479| 1. 0494| 1. 0507 206 | 1. 0281| 1. 0352| 1. 0402| 1. 0423| 1. 0441| 1. 0458| 1. 0473| 1. 0487 208 | 1. 0260| 1. 0331| 1. 0381| 1. 0402| 1. 0421| 1. 0437| 1. 0453| 1. 0466 210 | 1. 0239| 1. 0310| 1. 0361| 1. 0381| 1. 0400| 1. 0416| 1. 0432| 1. 0445 212 | 1. 0218| 1. 0290| 1. 0340| 1. 0361| 1. 0379| 1. 0396| 1. 0411| 1. 0425 ---------------------------------------------------------------------------- _Table of factors of evaporation_--Concluded. ============================================================================ Feed | Steam pressure in pounds per square inch, gauge. Temperature, |--------------------------------------------------------------- °F. | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 ------------+-------+-------+-------+-------+-------+-------+-------+------- 32 | 1. 2292| 1. 2304| 1. 2315| 1. 2324| 1. 2333| 1. 2342| 1. 2351| 1. 2358 35 | 1. 2261| 1. 2273| 1. 2283| 1. 2293| 1. 2302| 1. 2311| 1. 2320| 1. 2327 38 | 1. 2230| 1. 2242| 1. 2252| 1. 2262| 1. 2271| 1. 2280| 1. 2288| 1. 2296 41 | 1. 2199| 1. 2211| 1. 2221| 1. 2231| 1. 2240| 1. 2249| 1. 2257| 1. 2265 44 | 1. 2168| 1. 2180| 1. 2190| 1. 2200| 1. 2209| 1. 2218| 1. 2226| 1. 2234 47 | 1. 2137| 1. 2149| 1. 2159| 1. 2168| 1. 2178| 1. 2187| 1. 2195| 1. 2202 50 | 1. 2106| 1. 2118| 1. 2128| 1. 2137| 1. 2147| 1. 2156| 1. 2164| 1. 2171 53 | 1. 2075| 1. 2087| 1. 2097| 1. 2107| 1. 2116| 1. 2125| 1. 2133| 1. 2141 56 | 1. 2044| 1. 2056| 1. 2066| 1. 2076| 1. 2085| 1. 2094| 1. 2102| 1. 2110 59 | 1. 2013| 1. 2025| 1. 2035| 1. 2045| 1. 2054| 1. 2063| 1. 2072| 1. 2079 62 | 1. 1982| 1. 1994| 1. 2005| 1. 2014| 1. 2023| 1. 2032| 1. 2041| 1. 2048 65 | 1. 1951| 1. 1963| 1. 1974| 1. 1983| 1. 1992| 1. 2002| 1. 2010| 1. 2017 68 | 1. 1920| 1. 1933| 1. 1943| 1. 1952| 1. 1961| 1. 1971| 1. 1979| 1. 1986 71 | 1. 1889| 1. 1902| 1. 1912| 1. 1921| 1. 1931| 1. 1940| 1. 1948| 1. 1955 74 | 1. 1859| 1. 1871| 1. 1881| 1. 1890| 1. 1900| 1. 1909| 1. 1917| 1. 1924 77 | 1. 1828| 1. 1840| 1. 1850| 1. 1860| 1. 1869| 1. 1878| 1. 1886| 1. 1894 80 | 1. 1797| 1. 1809| 1. 1820| 1. 1829| 1. 1838| 1. 1847| 1. 1856| 1. 1863 83 | 1. 1766| 1. 1778| 1. 1789| 1. 1798| 1. 1807| 1. 1817| 1. 1825| 1. 1832 86 | 1. 1735| 1. 1748| 1. 1758| 1. 1767| 1. 1776| 1. 1786| 1. 1794| 1. 1801 89 | 1. 1704| 1. 1717| 1. 1727| 1. 1736| 1. 1746| 1. 1755| 1. 1763| 1. 1770 92 | 1. 1674| 1. 1686| 1. 1696| 1. 1705| 1. 1715| 1. 1724| 1. 1732| 1. 1739 95 | 1. 1643| 1. 1655| 1. 1665| 1. 1675| 1. 1684| 1. 1693| 1. 1701| 1. 1709 98 | 1. 1612| 1. 1624| 1. 1635| 1. 1644| 1. 1653| 1. 1662| 1. 1671| 1. 1678 101 | 1. 1581| 1. 1593| 1. 1604| 1. 1613| 1. 1622| 1. 1632| 1. 1640| 1. 1647 104 | 1. 1550| 1. 1563| 1. 1573| 1. 1582| 1. 1592| 1. 1601| 1. 1609| 1. 1616 107 | 1. 1519| 1. 1532| 1. 1542| 1. 1551| 1. 1561| 1. 1570| 1. 1578| 1. 1585 110 | 1. 1489| 1. 1501| 1. 1511| 1. 1521| 1. 1530| 1. 1539| 1. 1547| 1. 1555 113 | 1. 1458| 1. 1470| 1. 1481| 1. 1490| 1. 1499| 1. 1508| 1. 1515| 1. 1524 116 | 1. 1427| 1. 1439| 1. 1450| 1. 1459| 1. 1468| 1. 1478| 1. 1486| 1. 1493 119 | 1. 1396| 1. 1409| 1. 1419| 1. 1428| 1. 1437| 1. 1447| 1. 1455| 1. 1462 122 | 1. 1365| 1. 1378| 1. 1388| 1. 1397| 1. 1407| 1. 1416| 1. 1424| 1. 1431 125 | 1. 1335| 1. 1347| 1. 1357| 1. 1366| 1. 1376| 1. 1385| 1. 1393| 1. 1400 128 | 1. 1304| 1. 1316| 1. 1326| 1. 1336| 1. 1345| 1. 1354| 1. 1362| 1. 1370 131 | 1. 1273| 1. 1285| 1. 1295| 1. 1305| 1. 1314| 1. 1323| 1. 1332| 1. 1339 134 | 1. 1242| 1. 1254| 1. 1265| 1. 1274| 1. 1283| 1. 1292| 1. 1301| 1. 1308 137 | 1. 1211| 1. 1224| 1. 1234| 1. 1243| 1. 1252| 1. 1262| 1. 1270| 1. 1277 140 | 1. 1180| 1. 1193| 1. 1203| 1. 1212| 1. 1221| 1. 1231| 1. 1239| 1. 1246 143 | 1. 1149| 1. 1162| 1. 1172| 1. 1181| 1. 1191| 1. 1200| 1. 1208| 1. 1215 146 | 1. 1119| 1. 1131| 1. 1141| 1. 1150| 1. 1160| 1. 1169| 1. 1177| 1. 1184 149 | 1. 1088| 1. 1100| 1. 1110| 1. 1120| 1. 1129| 1. 1138| 1. 1146| 1. 1154 152 | 1. 1057| 1. 1069| 1. 1079| 1. 1089| 1. 1098| 1. 1107| 1. 1115| 1. 1123 155 | 1. 1026| 1. 1038| 1. 1048| 1. 1058| 1. 1067| 1. 1076| 1. 1085| 1. 1092 158 | 1. 0995| 1. 1007| 1. 1018| 1. 1027| 1. 1036| 1. 1045| 1. 1054| 1. 1061 161 | 1. 0964| 1. 0976| 1. 0987| 1. 0996| 1. 1005| 1. 1014| 1. 1023| 1. 1030 164 | 1. 0933| 1. 0945| 1. 0956| 1. 0965| 1. 0974| 1. 0984| 1. 0992| 1. 0999 167 | 1. 0902| 1. 0914| 1. 0925| 1. 0934| 1. 0943| 1. 0953| 1. 0961| 1. 0968 170 | 1. 0871| 1. 0883| 1. 0894| 1. 0903| 1. 0912| 1. 0922| 1. 0930| 1. 0937 172 | 1. 0850| 1. 0863| 1. 0873| 1. 0882| 1. 0892| 1. 0901| 1. 0909| 1. 0916 174 | 1. 0830| 1. 0842| 1. 0853| 1. 0862| 1. 0871| 1. 0880| 1. 0889| 1. 0896 176 | 1. 0809| 1. 0822| 1. 0832| 1. 0841| 1. 0850| 1. 0860| 1. 0868| 1. 0875 178 | 1. 0789| 1. 0801| 1. 0811| 1. 0820| 1. 0830| 1. 0839| 1. 0847| 1. 0854 180 | 1. 0768| 1. 0780| 1. 0791| 1. 0800| 1. 0809| 1. 0818| 1. 0827| 1. 0834 182 | 1. 0747| 1. 0760| 1. 0770| 1. 0779| 1. 0788| 1. 0798| 1. 0806| 1. 0813 184 | 1. 0727| 1. 0739| 1. 0749| 1. 0759| 1. 0768| 1. 0777| 1. 0785| 1. 0793 186 | 1. 0706| 1. 0718| 1. 0729| 1. 0738| 1. 0747| 1. 0756| 1. 0765| 1. 0772 188 | 1. 0685| 1. 0698| 1. 0708| 1. 0717| 1. 0727| 1. 0736| 1. 0744| 1. 0751 190 | 1. 0665| 1. 0677| 1. 0687| 1. 0697| 1. 0706| 1. 0715| 1. 0723| 1. 0731 192 | 1. 0644| 1. 0656| 1. 0667| 1. 0676| 1. 0685| 1. 0694| 1. 0703| 1. 0710 194 | 1. 0623| 1. 0636| 1. 0646| 1. 0655| 1. 0664| 1. 0674| 1. 0682| 1. 0689 196 | 1. 0603| 1. 0615| 1. 0625| 1. 0635| 1. 0644| 1. 0653| 1. 0661| 1. 0669 198 | 1. 0582| 1. 0594| 1. 0605| 1. 0614| 1. 0623| 1. 0632| 1. 0641| 1. 0648 200 | 1. 0561| 1. 0574| 1. 0584| 1. 0593| 1. 0602| 1. 0612| 1. 0620| 1. 0627 202 | 1. 0541| 1. 0553| 1. 0563| 1. 0572| 1. 0582| 1. 0591| 1. 0599| 1. 0606 204 | 1. 0520| 1. 0532| 1. 0542| 1. 0552| 1. 0561| 1. 0570| 1. 0579| 1. 0586 206 | 1. 0499| 1. 0511| 1. 0522| 1. 0531| 1. 0540| 1. 0550| 1. 0558| 1. 0565 208 | 1. 0478| 1. 0491| 1. 0501| 1. 0510| 1. 0520| 1. 0529| 1. 0537| 1. 0544 210 | 1. 0458| 1. 0470| 1. 0480| 1. 0490| 1. 0499| 1. 0508| 1. 0516| 1. 0524 212 | 1. 0437| 1. 0449| 1. 0460| 1. 0469| 1. 0478| 1. 0487| 1. 0496| 1. 0503 PUBLICATIONS ON THE UTILIZATION OF COAL AND LIGNITE. A limited supply of the following publications of the Bureau ofMines has been printed and is available for free distribution untilthe edition is exhausted. Requests for all publications can not begranted, and to insure equitable distribution applicants arerequested to limit their selection to publications that may be ofespecial interest to them. Requests for publications should beaddressed to the Director, Bureau of Mines. The Bureau of Mines issues a list showing all its publicationsavailable for free distribution, as well as those obtainable onlyfrom the Superintendent of Documents, Government Printing Office, on payment of the price of printing. Interested persons shouldapply to the Director, Bureau of Mines, for a copy of the latestlist. PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION. BULLETIN 58. Fuel briquetting investigations, July, 1904, to July, 1912, by C. A. Wright. 1913. 277 pp. , 21 pls. , 3 figs. BULLETIN 76. United States coals available for export trade, byVan. H. Manning. 1914. 15 pp. , 1 pl. BULLETIN 85. Analyses of mine and car samples of coal collected inthe fiscal years 1911 to 1913, by A. C. Fieldner, H. I. Smith, A. H. Fay, and Samuel Sanford. 1914. 444 pp. , 2 figs. BULLETIN 89. Economic methods of utilizing western lignites, by E. J. Babcock. 1915. 74 pp. , 5 pls. , 5 figs. BULLETIN 119. Analyses of coals purchased by the Government duringthe fiscal years 1908-1915, by G. S. Pope. 1916. 118 pp. BULLETIN 135. Combustion of coal and design of furnaces, by HenryKreisinger, C. E. Augustine, and F. K. Ovitz. 1917. 144 pp. , 1 pl. , 45 figs. BULLETIN 136. Deterioration in the heating value of coal duringstorage, by H. C. Porter and F. K. Ovitz. 1917. 38 pp. , 7 pls. BULLETIN 138. Coking of Illinois coals, by F. K. Ovitz. 1917. 71pp. , 11 pls. 1 fig. TECHNICAL PAPER 34. Experiments with furnaces for a hand-firedreturn tubular boiler, by S. B. Flagg, G. C. Cook, and F. E. Woodman. 1914. 32 pp. , 1 pl. , 4 figs. TECHNICAL PAPER 50. Metallurgical coke, by A. W. Belden. 1913. 48pp. , 1 pl. , 23 figs. TECHNICAL PAPER 76. Notes on the sampling and analysis of coal, byA. C. Fieldner. 1914. 59 pp. , 6 figs. TECHNICAL PAPER 80. Hand-firing soft coal under power-plantboilers, by Henry Kreisinger. 1915. 83 pp. , 32 figs. TECHNICAL PAPER 97. Saving fuel in heating a house, by L. P. Breckenridge and S. B. Flagg. 1915. 35 pp. , 3 figs. TECHNICAL PAPER 98. Effect of low-temperature oxidation on thehydrogen in coal and the change of weight of coal in drying, by S. H. Katz and H. C. Porter. 1917. 16 pp. , 2 figs. TECHNICAL PAPER 123. Notes on the uses of low-grade fuel in Europe, by R. H. Fernald. 1915. 37 pp. , 4 pls. , 4 figs. TECHNICAL PAPER 133. Directions for sampling coal for shipment ordelivery, by G. S. Pope. 1917. 15 pp. , 1 pl. TECHNICAL PAPER 137. Combustion in the fuel bed of hand-firedfurnaces, by Henry Kreisinger, F. K. Ovitz, and C. E. Augustine. 1916. 76 pp. , 2 pls. , 21 figs. 15 cents. TECHNICAL PAPER 148. The determination of moisture in coke, by A. C. Fieldner and W. A. Selvig. 1917. 13 pp. TECHNICAL PAPER 170. The diffusion of oxygen through stored coal, by S. H. Katz. 1917. 49 pp. , 1 pl. , 27 figs. TECHNICAL PAPER 172. Effects of moisture on the spontaneous heatingof stored coal, by S. H. Katz and H. C. Porter. 1917. 25 pp. , 1pl. , 8 figs. PUBLICATIONS THAT MAY BE OBTAINED ONLY THROUGH THE SUPERINTENDENTOF DOCUMENTS. BULLETIN 8. The flow of heat through furnace walls, by W. T. Rayand Henry Kreisinger. 1911. 32 pp. , 19 figs. 5 cents. BULLETIN 11. The purchase of coal by the Government underspecifications, with analyses of coal delivered for the fiscal year1908-9, by G. S. Pope. 1910. 80 pp. 10 cents. BULLETIN 13. Résumé of producer-gas investigations, October 1, 1904, to June 30, 1910, by R. H. Fernald and C. D. Smith. 1911. 393pp. , 12 pls. , 250 figs. 65 cents. BULLETIN 14. Briquetting tests of lignite at Pittsburgh, Pa. , 1908-9, with a chapter on sulphite-pitch binder, by C. L. Wright. 1911. 64 pp. , 11 pls. , 4 figs. 15 cents. BULLETIN 18. The transmission of heat into steam boilers, by HenryKreisinger and W. T. Ray. 1912. 180 pp. , 78 figs. 20 cents. BULLETIN 21. The significance of drafts in steam-boiler practice, by W. T. Ray and Henry Kreisinger. 64 pp. , 26 figs. 10 cents. BULLETIN 22. Analyses of coals in the United States, withdescriptions of mine and field samples collected between July 1, 1904, and June 30, 1910, by N. W. Lord, with chapters by J. A. Holmes, F. M. Stanton, A. C. Fieldner, and Samuel Sanford. 1912. Part I, Analyses, pp. 1-321; Part II, Descriptions of samples, pp. 321-1129. 85 cents. BULLETIN 23. Steaming tests of coals and related investigations, September 1, 1904, to December 31, 1908, by L. P. Breckenridge, Henry Kreisinger, and W. T. Ray. 1912. 380 pp. , 2 pls. , 94 figs. 50cents. BULLETIN 27. Tests of coal and briquets as fuel for house-heatingboilers, by D. T. Randall. 44 pp. , 3 pls. , 2 figs. 10 cents. BULLETIN 37. Comparative tests of run-of-mine and briquetted coalon locomotives, including torpedo-boat tests, and some foreignspecifications for briquetted fuel, by W. F. M. Goss. 1911. 58 pp. , 4 pls. , 35 figs. 15 cents. BULLETIN 40. The smokeless combustion of coal in boiler furnaces, with a chapter on central heating plants, by D. T. Randall and H. W. Weeks. 1912. 188 pp. , 40 figs. 20 cents. BULLETIN 41. Government coal purchases under specifications, withanalyses, for the fiscal year 1909-10 by G. S. Pope, with a chapteron the fuel-inspection laboratory of the Bureau of Mines, by J. D. Davis. 1912. 97 pp. , 3 pls. , 9 figs. 15 cents. BULLETIN 109. Operating details of gas producers, by R. H. Fernald. 1916. 74 pp. 10 cents. BULLETIN 116. Methods of sampling delivered coal, andspecifications for the purchase of coal for the Government, by G. S. Pope. 1916. 64 pp. , 5 pls. , 2 figs. 15 cents. TECHNICAL PAPER 20. The slagging type of gas producer, with a briefreport of preliminary tests, by C. D. Smith. 1912. 14 pp. , 1 pl. 5cents. TECHNICAL PAPER 63. Factors governing the combustion of coal inboiler furnaces; a preliminary report, by J. K. Clement, J. C. W. Frazer, and C. E. Augustine. 1914. 46 pp. , 26 figs. 10 cents. TECHNICAL PAPER 65. A study of the oxidation of coal, by H. C. Porter. 1914. 30 pp. , 12 figs. 5 cents. TECHNICAL PAPER 114. Heat transmission through boiler tubes, byHenry Kreisinger and F. K. Ovitz. 1915. 36 pp. , 23 figs. 10 cents. TRANSCRIBER'S NOTES: Page 5: Added period to the sentence: "If the coal used in the testis to be analyzed, take a sample of from 4 to 6 pounds from eachbarrow and throw it into a box near the scales. ". Page 11: Changed typo "calcuate" to "calculate. " Page 18: Changed typo "1. 1854" to "1. 0854", see intersectingcolumns 184° F and 200 psi. Page 19: Changed typo "Samuel Sandford" to "Samuel Sanford. "