DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, DIEECTOB

412

TESTS OF

RUN-OF-MINE AND BRIQUETTED COAL

BY

WALTER T. RAY

AND

HENRY KREISINGER

WASHINGTON

GOVERNMENT PRINTING OFFICE

1909

CONTENTS.

Page.

Introduction............................................................. 5

Historical statement.................................................. 5

Personnel............................................................. 5

Acknowledgments-................................................... 6

Objects of the tests....................'..........................._... 6

Summary of results...............................'...,................ 6

Fuels, apparatus, and methods................ ........................... 7

The coal and the briquets............................................. 7

The locomotive and other testing apparatus............................ 8

Methods of conducting tests........................................... 11

Steam pressures.................................................. 11

Starting and closing ........................ ...................... 11

Ash and refuse................................................... 12

Fuel fired.. ...... ..^............................................. 13

Feed water. ...................................................... 13

Leaks and injector overflow....................................... 13

Flue gas. ........................................................ 13

Measuring "drafts".............................................. 13

Smoke observations.............................................. 13

Sparks........................................................... 14

Moisture in steam................................................. 14

Data and results of tests................................................... 14

Observations and computations........................................ 14

Notes on individual tests.............................................. 18

Effect of varying rates of combustion.................................. 20

On evaporation .................................................. 20

On rated capacity ........................ ........................ 21

On weight of sparks.............................................. 22

On heat distribution.............................................. 22

Graphic showing............................................. 22

Absorbed by boiler......; ...................................... 23

Loss of heat " up stack "...................................... 24

Heat unaccounted for......... ................................. 25

Heat loss in moisture......................................... 25

Heat loss in CO .............................................. 25

Loss of heat in sparks............................... .......... 26

On cost of steam ................................................. 26

Advantages of briquets for locomotive use ............................... 28

. Higher equivalent evaporation.................................... 28

Ease of manipulating fires......................................... 28

Possible increase in steam production.............................. 28

3
4 CONTENTS.

Data and results of tests Continued. Page.

Disadvantages of briquets for locomotive use........................... 29

Storage capacity.................................................. 29

Difficulty of shoveling............................................ 29

General deductions................................................... 29

Suggested changes in design and construction of locomotive............. 30

Grate and combustion chamber..................... T ............. 30

Dimensions of tubes.............................................. 30

"Draft "production...............'............................... 31

Survey publications on fuel testing and briquetting......................... 31

ILLUSTRATIONS.

FIGUKE 1. Construction of arch in furnace.................................. 8

2. Construction of smoke box...................................... 9

3. Construction of spark catcher and its attachmeat to the stack..... 10

4. Construction of nozzle regularly used on locomotive.............. 12

5. Eelations of rate of combustion to three stated factors............. 21

6. Relation of weight of ejected sparks to rates of combustion........ 22

7. Eelations of heat unaccounted for, absorbed, and loss " up stack "

to combustion................................................ 23

8. Relations of heat loss in moisture, in CO, and in sparks to combustion. 26

9. Relation of cost of steam to rates of combustion.................. 27
TESTS OF RUMF-MINE AND BRIQUETTED COAL IN A 

LOCOMOTIVE BOILER.

By WALTER T. RAY AND HENRY KREISINGER.

INTRODUCTION.

HISTORICAL STATEMENT.

In its investigation of more efficient methods for utilizing the coals

and lignites in the United States, to the end that waste may be avoided, 

the value of low-grade coals increased, and the life of the nation's fuel 

resources prolonged, the United States Geological Survey has carried 

on a study of the factors involved in the manufacture and use of briquets, including the suitabilit}' of various coals for briquetting, the 

cheapest and most satisfactory binders, and the furnace behavior and 

evaporative efficiency of briquetted fuel. The investigations began 

with the .work done at the coal-testing plant at the Louisiana Purchase 

Exposition, St. Louis, Mo., in 1904, and were continued at St. 

Louis and later at Norfolk, Va., as an essential part of the scheme of 

technologic research by the government fuel-testing plant. Accounts 

of various tests and statements of the conclusions to be drawn from 

them have appeared in a number of bulletins. 0

In connection with the work at Norfolk, comparative steaming tests 

were made in stationary, marine, and locomotive boilers with run-ofmine coal and the same coal formed into briquets of two sizes. The 

tests in a locomotive boiler that are described in detail in this bulletin 

were undertaken to add cumulative evidence to work done at other 

places. They were made possible through the courtesy of the Seaboard Air Line Railway Compai^ in supplying both the locomotive 

and the coal used. During the trials the locomotive stood on a side 

track in the shop yards of the railway company at Portsmouth, Va. 

No running tests were made.

PERSONNEL.

J. A. Holmes, expert in charge, technologic branch, United States 

Geological Survey, had general supervision of the investigations carried on at the Norfolk fuel-testing plant. H. M. Wilson, chief

oSee Bulls. U. S. Qeol. Survey Nos. 261, 290, 332, 343, 363, and 366; also Prof. Paper No. 48, p. 3.

5
6 TESTS OF COAL IN A LOCOMOTIVE BOILEE.

engineer, arranged for the locomotive tests here described, and had 

immediate control of the work done by the writers.

ACKNOWLEDGMENTS.

The authors wish to express their appreciation and thanks for the 

suggestions and criticisms of Messrs. H. M. Wilson and D. T. Randall, and of their consulting advisers, Profs. L. P. Breckenridge and 

W. F. M. Goss; but it is to be distinctly understood that none of them 

is to be held committed by any statements or opinions of the authors 

found herein.

The authors also desire to express their thanks to the officials of the 

Seaboard Air Line Railway, without whose interested aid and cooperation the tests could not have been made, especially to President 

Garrett and to Master Mechanic Poole and his assistant, Mr. Henry; 

also, to Mr. Greenwood, superintendent of shops, and his assistant, 

Mr. Yearwood, and to Chief Engineer Andrews.

OBJECT OF THE TESTS.

The primary object of the tests was to study the relative performances of the two types of briquets and of the coal, with reference to 

efficiency, tendency to smoke, and the ease with which steam could be 

kept up, when each of the three varieties of fuel was burned at several 

rates of combustion. Many secondary objects were in mind, the data 

concerning which are discussed under '' Effect of varying rates of combustion," pages 20-27.

One object kept especially in mind was the finding of ways for working locomotive boilers harder, although with present locomotive 

designs the steam production may sometimes be made sufficient to

keep the wheels slipping, so that the engines have no use for additional steaming ability of the boiler.

SUMMARY OF RESULTS.

The most useful secondary conclusion demonstrated is that the combustion of suitable fuel can be kept about the same in completeness 

over a very wide range. This result is a consequence of the scrubbing action of rapidly moving currents of gases. In the case of com- 

' bustion in the fuel bed the C02 formed at the surface of the particles 

of fuel and clinging to it is scrubbed off and replaced by fresh uncombined oxygen.

The more important results and conclusions for the locomotive used 

are briefly summarized here:

At low rates of working, run-of-mine coal gives a higher equivalent 

evaporation than briquets; at medium rates there is little difference; 

at high rates briquets do considerably better.
FUELS; APPAKATUS, AND METHODS. 7

There is little difference between the large and the small briquets; 

the larger ones crumble less.

The smaller briquets are easier to fire and to level on the fire than 

are the larger ones; either form gives the fireman far less work and 

trouble than run-of-mine coal.

In sparks briquet fires lose less than coal fires. '

On roads having heavy grades it will probably pay well to burn 

briquets, at least part of the time.

The high-capacity test run with briquets (test 14) was by no means 

the upper limit of fairly efficient combustion and evaporation, but it 

was higher than is likely ever to be attained by such draft as is 

feasibly available from a nozzle.

These particular briquets produced about as much smoke as the coal 

under similar conditions; some of the blame for this tendency to smoke

may rest on the pitch binder,

Perhaps it would pay to add combustion chambers several feet long 

to the front ends of some locomotive fire boxes, and use a larger number of boiler tubes of shorter lengths and smaller diameters.

FUELS, APPARATUS, AND METHODS.

THE COAL AND THE BRIQUETS.

All the coal was run-of-mine from the Turkey Gap mine, working 

the Pocahontas No. 3 bed at Ennis, McDowell County, W. Va. Part 

of it went to the briquetting section of the fuel-testing plant at Norfolk, where it was made into two sizes of briquets.

The smaller of these two sizes was circular in horizontal cross section, 3i inches in diameter. Its vertical cross section was nearly 

oval, 2f inches at the center by li inches near the circumference. 

The larger size was rectangular in either cross section, its dimensions 

being 3 by 4£ by 6f inches. The small briquets were compressed at 

about 1,000 pounds and the large ones, at about 2,500 pounds per 

square inch. The pitch used was approximately the same in kind and 

percentage. 0

<* For detailed description of methods of manufacture and physical tests of briquets seeBriquetting 

tests at Norfolk, Va.: Wright, C. L., Bull. U. S. Geol. Survey No. 385,1909.
8 TESTS OP COAL IN A LOCOMOTIVE BOILER.

THE LOCOMOTIVE AND OTHER TESTING APPARATUS.

The locomotive used in these tests was of the 10-wheel, freight 

type, built in 1906. The principal dimensions of its furnace and 

boiler were as follows:

TABLE 1. Principal dimensions of furnace and boiler.

Furnace:

Length ....................... inches..

Width near grate ................do....

Width at widest place..........do....

Height..........................do....

Hocking, finger-type grate:

Length..........................do....

Width...........................do....

108

41

55

55

104

41

Area .....................square feet.. 29.65

Ratio to heating surface ............ 1 to 87.2

Approximate air space .... .per cent.. 30

Boiler:

Diameter of shell............inches.. 63.5

Waist diameter ................do.... 72

Number of tubes ..................... 328

Inside diameter of tubes.....inches.. 2

Length of tubes ................feet.. 14J

Heating surface:

Of fire box ..............square feet.. 167.5

Of tubes........................do.... 2,416.5

Total...........................do.... 2,584

Approximate minimum cross - sectional

area of gas passage...... .square feet.. 1

 

IE:

1

ASH

-,..,. J

1"

PAN

-GRATE LEVEL

SECTION ON C-D SECTION ON A-B

PIGUBE 1. Construction of arch in furnace.

The furnace was equipped with a fire-brick arch supported b}^ four 

2i-inch water tubes. The position and construction of the arch are 

shown in figure 1.

Figure 2 shows the internal arrangement of the smoke box. CDF 

is a solid sheet-iron partition, FG an adjustable apron, HJK a screen 

of perforated sheet iron, a LM a deflecting plate made of cast iron, N

a Most of the locomotives of this road are now equipped with a wire network screen, which offers 

less resistance to the flow of air through it.
FUELS; APPAKATUS, AND METHODS. 9

the exhaust nozzle, and S the steam pipe. The partition CDE and the 

spark screen HJK separate the smoke box into three chambers, which 

are designated 0, 5, and c. Chamber a receives 'the gases as they leave 

the boiler tubes. From chamber a the gases flow through the contracted passage between G and L into chamber J. As the passage is 

very narrow they must flow through it at very high velocities, and 

the high velocities must in some degree be imparted to the sparks in 

chamber a. The sparks are deflected upward from their straight 

course by the plate LM and thrown against the screen HJK; they are 

partly broken by impact against the deflecting plate and the screen, 

and the small pieces pass through the latter and out through the stack.

SECTION ON A-B FRONT VIEW OF'SMOKE BOX

FIGURE 2. Construction of smoke box.

Larger pieces are reflected back and fall down toward the apron, most 

of them into the high-velocity current of gas which again hurls them 

against the deflecting plate and the screen; eventually practically 100 

per .cent pass through the stack. Just what amount of "draft" 0 

energy is required .to effect this pulverization is unknown; probably 

it is very small. The sliding apron FG can be lowered or raised so as 

to make the passage beneath it smaller or larger. The purpose of all

a Wherever the word " draft" is used in its usual sense in discussing the motive force which moves 

the air and gases through the fuel bed and boiler, it is placed in quotation marks, to call to mind the 

misusage; in the sense under consideration there is really no such thing as "draft." " With gases ' 

there is no pulling, only pushing." "Draft" maybe defined as the static difference between the 

pressures at two points .of a flowing stream of gas.

10042 Bull. 412 09 2
10 TESTS OF COAL IN A LOCOMOTIVE BOILER.

these fittings in the smoke box is to reduce the size of the sparks 

before ejectment so as to make them less noticeable and less dangerous 

to fields, buildings, etc. Locomotives equipped with such smoke-box 

arrangements are sometimes termed " self -sparking." It is very 

probable that a part of the sparks are burned in the smoke box, in 

chambers a and 1). The fact that a considerable quantity of clinker 

was found in chamber a, when cleaning the locomotive before testing, 

strengthens this probability.

WIRE SCREEN

FIGURE 3. Construction of spark catcher and its attachment to the stack.

Figure 2 shows also the location of "draff-gage connections, fluegas sampler, and a thermometer for measuring flue-gas temperature 

approximately. 0 The flue-gas sampler was made of f-inch pipe, 

having the free end plugged, and TVinch holes drilled on both sides 

in staggered rows; it extended nearly across the smoke box. The

a Granting that the thermometer in use was absolutely correct, it nevertheless read too low 

because it could "see" some water-cooled surf aces, to which it radiated some of its heat. In the case 

of a certain stationary boiler this error was over 35° F. Probably 99 per cent of all boiler 

tests published give readings of flue temperatures 10° to 200° too low. In this particular case the 

error was probably considerably less than 35°, because most of the surface the thermometer could 

" see " was nearly as hot as the gases, and the current of gas in which the thermometer was placed 

was very fast; the faster the current of gas the less the error.
FUELS; APPARATUS, AND METHODS. 11

"draft" pipe was of i-inch nominal size, with no holes in its sides, 

and having the open end situated at the center of the smoke box. The 

bulk of the thermometer was also placed close to the end of the pipe.

Figure 3 shows, attached to the stack, the spark catcher especially 

designed and constructed for these tests. Its object was to collect the 

sparks from a sector of the exit end of the stack, the sector constituting one-tenth of the total exit area, so that the total weight of sparks 

leaving the stack was approximately ten times the weight collected in 

the receptacle.

The spark catcher consists of a V-shaped vessel made of sheet iron, 

the V-shaped opening being inverted over the stack, and being a sector 

of a circle having an angular area of 36°. The portion outside is 

nearly rectangular in cross section and ends in a detachable sheet-iron 

receptacle into which the sparks fall. The outside wall of this outer 

portion is partly replaced by a wire netting having 24 meshes to the 

inch; the gases pass through, but most of the sparks fall down as 

mentioned above. When the sparks are thrown out at a rapid rate, 

the bottom receptacle can be emptied and replaced while continuing 

the test. The spark catcher was placed on the stack at right angles 

to the axis of the boiler.

METHODS OP CONDUCTING TESTS.

Steam pressures. All tests were made while the locomotive was 

standing out of doors in the yard of the Portsmouth shops of the 

Seaboard Air Line Railway. "Draft" was produced by removing 

both valves from the steam chests and blowing steam through the 

main throttle and the cylinders-into the nozzle (fig. 4) and out through 

the stack. Steam not thus used was discharged through special pipe 

connections into the main steam header of one of the stationary boiler 

plants. This plant carried a pressure of less than 100 pounds per 

square inch, while the pressure in the locomotive was 200 pounds; a 

globe valve, in the pipe between the locomotive and the header, was 

used to regulate the pressure in the locomotive.

Steam pressure was read off the regular locomotive gage, which was 

reliable within 2 or 3 pounds. The pressure was also automatically 

recorded by a Crosby recording gage, which was accurate within 2 or 

3 pounds.

Starting and closing. A modification of the " alternate method" 

was used in starting and closing tests. Fire was kindled with 

wood on a clean grate and built up very rapidly with coal. As 

soon as the steam pressure had risen to 200 pounds the fire waa leveled and the test started. This preparatory firing took one to two 

hours and required the burning of 300 to 500 pounds of coal. On 

starting the test the thickness of the fuel bed was measured as accurately as possible with a prong, and readings were taken of steam
12 TESTS OF COAL IN A LOCOMOTIVE BOILER.

pressure, height of water in the boiler, height of water in the tender, 

and "draft" in the furnace. Closing conditions of the tests were 

made as nearly as possible the same as those of starting. The tests 

were usually started with a layer of burning coal 3 or 4 inches .thick. 

Ash and refuse. Just at closing the thickness of the bed of fuel 

above the layer of clinker was estimated as nearly as possible. 

After closing the test the fire was burned down entirely, the clinkers 

pulled out through the fire door, weighed, and charged to the test. 

It was impracticable to clean the fire before the close of the test,

SECTION ON A-B

1

FIGURE 4. Construction of nozzle regularly used on locomotive.

because the lower edge of the fire door was 14 inches above tne grate. 

Immediately before starting each test the ash pan was cleaned. After 

closing and removing the clinker from the grate all the ash was taken 

from the ash pan, weighed, and charged to the test. At first thought 

it might appear that the weight of ash thus obtained must be too 

great, but the chemical analysis of the coal shows that it was too low 

in all cases excepting one. Items figured from the weight of ash 

actually obtained are inaccurate and are given to show the futility of 

calculation and deductions so based.
FUELS, APPARATUS, AND METHODS. 13

Fuel fired. Coal was weighed with small platform scales on which 

was placed a box of 300 pounds capacity. The scales with the box 

thereon were located in the front part of the tender directly in front 

of the furnace, and one side of the box was let down so that coal could 

be, easily fired from it. The time of each firing was recorded, the 

coal being weighed only each time the box was filled, the times of 

filling being recorded. Each time while the box was being filled a 

sample of coal was taken for analysis, a little at a time, amounting to 

a total of about a shovelful per box.

Feed water. Water was weighed on a small platform scale in a tank 

haying a capacity of 636 pounds. The scale and tank were placed on 

top of the tender near the rear end. Specially erected piping carried 

water from the city main to the weighing tank. The water drained 

from the weighing tank into the tender tank, and on each occasion the

time of emptying and the weight of water were recorded. A long

glass water-level gage was connected to the tender tank so that the 

height of water in it could be read from a scale at regular or special 

observations. Tests were opened with the. tender tank nearly full of 

water and closed at the same level. A thermometer was immersed in 

the water in the tender and temperatures taken at regular intervals.

Leaks and injector overflow. During tests all leakage from the 

boiler and tender was caught in buckets and weighed, and its total 

weight was subtracted from the total weight of the water put into the 

tender tank. The overflows from the injectors were likewise caught 

and allowed for.

Flue gas. Flue gas was sampled with the specially constructed gas 

sampler described on page 10 and piped into a box car set just behind 

the tender. In the car was an improvised laboratory in which the gas 

was analyzed for CO2 , O2 , and CO, in an Orsat apparatus. The 

gas was drawn into the car with a steam ejector. Samples thus collected were occasionally checked by samples taken immediately at the 

smoke box.

On most of the tests the smoke-box temperature was measured with 

a mercury thermometer; on two or three of the high-capacity tests it 

was measured with a platinum and platinum-rhodium thermocouple, 

the position of which inside the smoke box is shown in figure 2.

Measuring "drafts." Gas pressures ("drafts") were measured on 

all tests, over the fuel bed, at the exit of the boiler tubes in chamber a 

(fig. 2), and near the nozzle in chamber d On the first six tests the 

pressures were also taken over the arch in the fire box. Ordinary 

U-tube manometers were used for all these readings.

/Smoke observations. A set of Binglemann smoke charts was prepared as an aid .in the estimation of the comparative darkness of smoke; 

but inasmuch as the darkness was usually between No. 0 and No, 1 

the charts were of little advantage and were seldom used. The den-
14 TESTS OF COAL IN A LOCOMOTIVE BOILER.

sities of smoke given in Table 2 are averages of the estimates of two 

or three observers.

Sparks. The weight of sparks ejected from the stack was determined with the apparatus shown in figure 3 and described on page 11. 

As is there stated, this apparatus collected sparks from one-tenth of 

the total cross-sectional area of the stack, so that the total weight of 

sparks ejected from the stack could be fairly well obtained bjr multiplying by 10 the amount caught in the receptacle. In most cases the 

sparks were collected during the entire time of the test. On the highcapacity tests the receptacle was removed when about full and the 

time noted. It was then emptied and replaced. After weighing the 

sparks from the whole test they were carefully mixed and a sample 

of about 2 pounds taken and sent in an air-tight can for chemical 

analysis. The chemical analyses of the sparks and of the coal and 

refuse were made under the immediate supervision of Mr. Fred M. 

Stanton in the chemical laboratories of the technologic branch of the 

United States Geological Survey at Pittsburg, Pa.

Moisture in steam. A throttling calorimeter was attached to the 

steam pipe leading from the steam dome to the stationary-boiler plant 

and the moisture in the steam was determined at regular intervals. 

Of course the steam used in producing "draft" Avas not sampled by 

the calorimeter, but the location of the latter was the best under the 

given conditions.

DATA AND RESULTS OF TESTS.

OBSERVATIONS AND COMPUTATIONS.

In all, 14 tests were made; 6 on run-of-mine coal, 4 on large briquets, 

and 4 on small briquets. The tests were made at various rates of combustion, the lowest being 18 pounds of dry fuel per hour per square 

foot of grate surface when burning coal, and the highest being about 

110 pounds of dry fuel when burning small briquets. The recorded 

observations made during the tests and the results calculated therefrom are given in Table 2.

The computations embodied in the table were made according to 

the method given in Bulletin 325. a This method is in practical accord 

with the recommendations of the American Society of Mechanical 

Engineers. The figures in parentheses at the heads of columns in the 

table are the item numbers of the society's code for boiler tests.

aBreckenridge, L. P., A study of four hundred steaming tests: Bull. U. S. Geol. Survey No. 325,1907, 

pp. 151-162.
16 TESTS OF COAL Itt A LOCOMOTIVE BOILEE.

TABLE 2. Summary of observed data and calculated items of 14 tests made with a 

locomotive boiler, February 7-27, 1908 Continued.

Test No.

1

1..........

2..........

3..........

5..........

0..........

7..........

8..........

9..........

10.......... 11..:.......

12..........

13..........

14..........

Ash 

and refuse in 

dry 

fuel 

(per 

cent).

24(31)

8 V7

7.82

5.62 

0.00 

6.03 

9.83 

6.14

0.32

v Test No.

1

1.. ................

2..................

3..................

4..................

5..................

C.... ..............

7..................

8..................

9..................

10..................

11. ..................

12..................

13..................

14 ..................

Proximate analysis (per cent).

Fixed carbon.

In 

moist 

coal.

25 (32)

73. 35 

73.07 

74.24 

73. 25

73. 13 

73.12 

73.47 

72.12 

71. 24 

74. 41 

72. 66 

73! 82 

73. 17 

69.04

In ' ' combustible."

26

83.13 

83. 49 

84. 40 

84. 48 

81. 07 

82. 35 

82.85 

81.04 

82.58 

81.07 

80.87 

80.43 

83.91 

80.30

Volatile matter.

In 

1 moist 

coal.

27 (33)'

14.97 

14.50 

13.00 

13.40 

16. 41 

15.67 

15.21 

16. 8G 

15. 01 

17.37 

17.18 

17.96 

14.03 

16.93

In " combustible."

28

10.87 

10. 51 

15. 54 

15.52 

18.33 

17.65 

17.15 

18.96 

17.42 

18.93 

19.13 

19.57 

16.09 

19.70

Moisture.

In 

fuel as 

fired.

29 (34)

3.66 

4.35 

4.76 

3.78 

3.43 

4.25 

4.03 

4.31 

6.64 

2.42 

3.01 

2.24 

(i. 18 

4.56

Ultimate analysis, dry basis (percent).

Carbon.

35 (37)

83.15 

84.30 

82.73 

81.38 

84.84 

83.66 

83.98 

84.19 

84.12 

84. 48 

83. 19 

84.62 

84.73 

82.21

Hydrogen.

36 (38)

4.29 

4.23 

4.11 

4.13 

4.31 

4.10 

4.22 

4.18 

4.18 

4.05 

4.10 

4.42 

4.23 

4.25

Oxygen.

37 (39)

3.14 

2.21 

4.02 

3.19 

2.05 

3.41 

3.32 

3.07 

2.54 

4.03 

3.99 

8. 31 

'2. 45 

2.03

Nitrogen.

38 (40)

1.04 

.99 

1.05 

1.03 

.98 

1.00 

.94 

1.11 

.96 

1.10 

.81 

1.01 

.98 

.98

Carbon 

in 

refuse.

39 (44)

46.28 

20.40 

25.14 

17.42 

22.31 

34. 51 

27.68 

29.42 

26. 91 

34.69 

26. 57 

26.08 

28. 31 

34.92

( 6 )

30

4. 13 

4.93 

5.42 

4.36 

3.83 

4.79 

5.22

' 4.85

7.70 

2.53 

3.45 

2.44 

7.09 

5.31

Earthy 

matter in refuse, including moisture.

40

53.72 

79.60 

74.86 

83. 58 

77. 69 

05. 49 

72. 32 

70. 58 

73.09 

65.31 

73.43 

73.92 

71.69 

65.08

Ash.

Moist 

basis.

31

7.62 

7.42 

7.34 

9. 51 

7.03 

6.96 

6.69 

6.71 

7.11 

5.80 

7.15 

5.98 

6.62 

9.47

Dry 

basis.

32 (42)

7. 91 

7.70 

7.71 

9.88 

7.28 

7.27 

7.01 

7.0L 

7.62 

5.94 

7.37 

0.12 

7.06 

9.92

Heat value per 

pound (B.t.u.).

Dry

fuel.

41 (50)

14,463 

14,494 

14,553 

14, 245 

14,093 

14, 789 

14', 702 

14, 753 

14, 503 

14,897 

14, 742 

14, 930 

14,571 

14, 292

"Combustible."

42 (51)

15, 705 

15, 720 

15, 782 

15,816 

15,844 

15, 945 

15,815 

15, 868 

15, 688 

15, 838 

15, 743 

15,915 

15, 680 

15,871

Sulphur.o

Moist 

basis.

33

0.45 

.49 

.36 

.38 

.52 

.50 

.51 

.42 

.54 

.39 

.47 

.51 

.52 

.58

Dry 

basis.

34(41)

0.47 

.51 

.38 

.39 

.54 

.50 

!53 

' . 44 .r.8

.40 

.48 

.52 

.55 

.61

Steam (per 

cent) .

Moisture in.

43 (54)

0.5 

.7 

.3 

.5 

1.4 

.9 

1.0 

1.0 

.8 

1.0 

1.0 

.7 

.9 

1.4

Quality

Of.

44(56)

0. 996 

.995 

.998 

.996 

.990 

.992 

. 993 

. 993 

.994 

.993 

.993 

.995 

.993 

.988

a Separately determined.

6 Accompanying 100 per cent of " combustible."
DATA AND RESULTS OF TESTS. 15

TABLE 2. Summary of observed data and calculated items of 14 tests made with a 

locomotive boiler, February 7-27, 1908.a

Test 

No.

1

1... 

2... 

3... 

4

5... 

fi

7

8

9... 

10... 

11

13... 

14...

Form and condition of fuel.

2

Run of mine..... 

.....Ao.d.. ........ 

.....do. ........... 

.....do............

Large briquets... 

.....do............

.....do............

.....do............

Run of minee.... 

Small briquets/..

.....do............

Run of mine ..... 

Small briquets g..

Date of 

trial.

3(1)

Feb. 7 

Feb. 8 

Feb. 10 

Feb. 11 

Feb. 12 

Feb. 13 

Feb. 14 

Feb. 17 

Feb. 18 

Feb. 19 

Feb. 20 

Feb. 21 

Feb. 26 

Feb. 27

Duration 

(hours).

4(2)

6.08 

5.08 

6.17 

7.00 

5.28 

4.50 

4.45 

3.80 

3.92 

4.07 

3.07 

3.48. 

4.18 

2.02

Average pressures.

Barometer (inches oi mercury) .

5(11)

30.34 

80.51 

30.68 

30.50 

30.53 

30.31 

29.97 

30.06 

30.36 

29.80 

30.03 

30.16 

29.67 

29.78

Steam c 

(pounds 

per 

sq. in.).

6 (11.1)

171 

172 

149 

159 

171 

162 

186 

182 

168 

167 

182 

171 

168 

150

"Draft "6 below atmosphere 

(inches of water).

Near 

nozzle.

7

0.77 

2.30 

2.27 

.59 

1. 25 

2.63 

5.48 

7.70 

7.36 

2.11 

8.10 

5.07 

5.50 

11.80

Over 

fuel 

bed.

8

0.39 

1.05 

.87 

.33 

.57 

1.03 

1.95

Over 

furnace 

arch.

9

0.48 

'1.01 

1.12 

.41 

.70 

1.37 

2.54 

3.01 

2.65 

.56 

2.73 

1.95 

2.41 

3.10

Leaving 

boiler 

tubes.

10

0.61 

1.86 

1.86 

.53 

1.00 

1.96 

3.69 

4.10 

4.54 

1.59 

5.48 

3.69 

3.89 

8.74

Clinker 

in ash 

and 

refuse 

(per 

cent).

11 (29)

52.7 

52.7 

45.0 

52.7 

46.0 

56.0 

28.3 

45.8 

19.7 

21.5 

22.2 

24.5 

21.6 

21.8

Test

No.

1

1. .

2. .

3. .

4. .

5. .

6. .

7. .

8. .

9. .

10. .

11. .

12. .

13. .

14. .

Average temperatures (° F.) 

of 

Atmosphere.

12(15)

45

40

39

37

44

56

63

36

36

55

41

41

51

40

Steam.

13 (17)

375

376

365

370

375

371

375

380

374

374

380

375

374

365

Feed

water 

in 

tank.

14(18)

55

63

49

48

51

51

50

51

49

49

48

46

48

46

Gases

leaving 

boiler 

tubes.

15 (21)

530

580

596

487

550

612

663

697

666

595

804

684

679

910

Fuel (total weights in 

pounds).

As 

fired.

16 (25)

4,600

5,500

7,200

3,986

4,367

6,000

7,420

9,030

9,070

4,800

7,500

6,300

7,800

6,800

Dry.

17 (27)

4,432

5, 260

6,856

3,834

4,217

6,748

7,073

8,638

8,469

4,683

7,271

6,156

7,318

6,489

and 

refuse.

18 (28)

210

425

472

324

272

231

465

522

517

474

450

391

651

417

"Combustible*" »

consumed 

(Ibs.).

19 (30)

3,985

4,770

6,208

3,400

3,849

5,247

6,451

7,882

7,685

4,242

6,618

5,680

6,617

5,701

Fired per hour (pounds).

Dry fuel.

For

grate.

20 (46)

729

1,035

1,112

548

799

1,277

1,590

2, 274

2,160

1,151

2,369

1,770

1,750

3,213

Persq. 

ft. of

grate.

21 (48)

24.60

34.83

37.53

18.47

26.95

43.10

53.62

76.70

72.85

38.80

79.90

59. 69

59.02

108. 30

" Combustible*." A

For

grate.

22 (47)

655

955

1,026

494

729

1,166

1,450

2,074

1,960

1,024

2,155

1,632

1,583

2,822

23 (49)

0.253

.368

.395

.187

.282

.451

.561

.803

. .759

.403

.834

.631

.613

1.092

a Code numbers (in parentheses at the top of certain columns) refer to corresponding items 

described in Bull. U. S. Geol. Survey No. 325, pp. 151-153. See also Prof. Paper U. S. Geol. Survey 

No. 48, pt. 2.

b The word '' draft" is placed in quotation marks because it is misused when applied to the moving 

of gases or to the pressure difference which causes them to move.

c Above atmosphere.

d Wet, much slack.

«Wet, mostly slack.

/10 per cent crumbled.

a 30 per cent crumbled.

ft The "combustible" factor in all columns of this table marked thus (*) is obtained by subtracting 

from the total weightof dry fuel fired the weight of ash therein, as figured from the chemical analysis, 

and further substracting weight of the combustible in the refuse, the latter combustible being calculated from the total weight of refuse and its analysis; the composition of the refuse combustible is 

loosely considered to be the same as that of the "combustible" of the dry fuel.

i Per square foot of water-heating surface.
DATA AND KESULTS OF TESTS. 17

TABLE 2. Summary of observed data and calculated items of 14 tests made with a 

locomotive boiler, February 7-27, 1908 Continued.

Test

No.

1

1....

2 ....

3....

4....

5....

6....

7....

8....

9 ....

10 ....

n....

12....

13 ....

14 ....

Water fed to boiler (pounds).

Total.

45 (57)

43, 655

50, 064

61,028

36, 333

40, 070

.52,713

63,688

72, 558

60, 283

43, 305

62, 998

53,956

59, 484

47,730

Equivalent evaporated from

and at 212°.

Total.

46 (58)

52, 998

60, 452

74,332

44, 363

48, 885

64, 204

77,890

88,593

73, 704

52, 832

77,109

66, 096

72, 689

58, 326

Per 

hour.

47 (63)

8,681

11,840

12,023

6,312

8,977

14, 153

17,381

23, 151

.18,689

12, 889

24,941

18, 898

17, 268

28,528

( c )

48

3.36

4.58

4.65

2.442

3.474

5.48

6.726

8.966

7.233

4.99

9/64

7.313

6.682

11.040

Into

dry 

steam.

49 (61)

52, 786

60,125

74,183

44,186

47, 397

63,690

77,345

87, 973

73, 262

52, 462

76,569

65, 766

72, 180

57, 627

Actually evaporated, a.

Total.

50 (59)

43,480

49, 814

60,906

36, 188

39, 669

52,291

63,242

72, 050

69, 921

43, 002

62,557

53, 686

59, 068

47,157

Per 

hour.

51 (62)

7,151

9,806

9,871

5, 170

7,513

11,620

14,211

18, 960

16, vi85

10, 565

20, 377

15, 429

14,131

23, 345

Evaporation.

(")

52 (68)

 9.49

9.10

8.48

9.11

9.18

8.79

8.58.

8.03

6.64

9.02

8.40

8.56

7.63

7.02

Factor 

of.

53 (60)

1.211

1.207

1.218

1. 221

1. 220

1.218

1.223

1.221

1.223

1.221

1.224

1. 225

1. 222

1.222

Equivalent evaporation per pound of 

Fuel as 

fired.

54(69)

11.47

10.94

10.30

11.08

10.85

10. 62

10.42

9.74

8.08

10.93

10.21

10. 44

9.25

8.48

Dry 

fuel.

55 (70)

11. 91

11.43

10.82

11.52

11. 24

11.08

10.93

10.18

8.65

11.20

10. 52

30.68

9.86

8.88

"Com 

busti- ble*."d

56 (71)

13. 24

12. 61

11. 95

13. 00

12.31

12. 14

11.99

11.03

9.53

12.36

11. 67

11. 58

10. 91

10.11

Test 

No.

1

1...... 

2...... 

3...... 

4...... 

5...... 

6...... 

7...... 

8...... 

9...... 

10...... 

11...... 

12...... 

13...... 

14......

Horsepower 

developed.

In 

boiler.

57 (65)

251.7 

343. 2 

348.5 

183. 0 

260.0 

410.2 

503.8 

671.0 

541.1 

373.6 

722.9 

547.7 

500.5 

827.0

Per 

cen t of 

rated.*

58 (67)

' 97.4 

132.8 

134.4 

70.8 

100. 6 

159.0 

195.0 

259.5 

209.3 

144.5 

279.7 

211.9 

193.7 

320.0

Efficiency of the 

boiler, etc.

(*)/

59 (72)

81.44 

77.48 

73.14 

79.39 

75.00 

73.50 

73.26 

67.16 

' 58.69 

75.39 

70.99 

70.29 

67.21 

61.56

Including 

grate.

60(73)

79.48 

76.18 

71.79 

78.12 

73.90 

72.37 

71.81 

66.67 

57.61 

72.62 

68.94 

69.08 

65.' 36 

60.02

Average thickness of 

fuel bed 

(inches).ff

61 (81)

8 

10-12 

12 

6 

14-16 

14-16 

18 

16 

16 6-8 

12 

8 

14-16 

16-18

Average time 

in tervnls (minutes) between 

Firings.

62 (82)

3-4 

3 

3 4-5 

3 

3 

3 

3 

3

3 

3 

3

(<)

Leveling and breaking up.

63 .(83)

16 

 10 

12 

40 

40

(*)

80 

(ft) 

.20

( ft ) 

ih)

") 

16 

(ft)

Analysis of dry flue gasses (per 

cent).

CO*

64 (84)

11.46 

11.96 

11.46 

11.10 

11.96 

12.45 

11.50 

12.05 

10. 16 

13.87 

13.57 

11.78 

12.20 

11.15

oa .

65 (85)

6.92 

7.00 

7.49 

 7.84 

7.07 

5.87 

7.08 

6.93 

8.49 

4.75 

4.49 

6.74 

6.94 

7.52

CO.

66 (86)

0.23 

.10 

.23 

.14 

.22 

.17 

.15 

.13 

.25 

' .03 

.30 

.05 

.20

N2.

67 (88)

81.63 

80.81 

80.95 

80.83 

80.83 

81.46 

81. 25 

80.87 

81. 22 

81. 13 

81.91 

81.18 

80.81 

81.13

a Corrected for quality of steam.

6 Apparent per pound of coal as fired.

c Per hour per square foot of water-heating surface.

d Figured from chemical analyses of ash and coal.

«Arbitrarily rated by authors, counting 10 square feet of heating surface to a boiler horsepower.

/ Figured from chemical analyses of asn and coal.

g Method of firing, spreading.

ft Fire not disturbed.

<Firing continuous.
TESTS OF COAL A LOCOMOTIVE BOILER.

TABLE 2. Summary of observed data and calculated items of J4 tests made with a 

locomotive boiler, February 7-27, 1908 Continued.

Test No.

1

1.... ..........

2..............

3 ...............

4 ..............

5..............

6..............

7..............

8..............

9..............

10..............

11..............

12 ..............

13 ..............

14 ..............

Per 

cent 

smoke.

68 (77)

0 

15.4 

19.4 

24 

10 

10 

10 

8 

8 

12 

0 

0 

0 

0

Sparks (pounds).

Total collected.

69

1 

7 

21 

No sps 

2 

9 

14 

31 627 

5 

35 

22 

23 

37.5

Ejected.

During 

test.

70

10 

70 

210 

irks coll 

20 

90 

140 

310 

529 

50 

350 

220 

230 

375

Per 

hour.

71

1.65 

13.77 

34 

ected. 

3.79 

20 

31.5 

81.6 

135 

12.3 

114 

63.2 

55 

185

Heat balance. «

Heat value of 1 

pound of "combustible."

B.t.u.

72 

15,705 

15, 720 

15, 782 

15,818 

15, 846 

15, 955 

15, 810 

15, 865 

15,688 

15,838 

15, 743 

35,915 

15, 680 

15, 865

Per cent.

73

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100

Heat absorbed 

by boiler (1).

B. t. u.

74

12,790 

12, 181 

11, 544 

12, 558 

11,891 

11, 727 

11, 582 

10, 655 

9,206 

31,940 

11,177 

11, 186 

30,539 

9,766

Pr. ct.

75

81.44 

77.48 

73.34 

79.39 

75.00 

73.50 

73.26 

67.16 

58.69 

75.39 

70.99 

70.29 

67.21 

61.56

Loss in sparks.

B. t. u.

76

137.1

215

41 

161 

216 

441 

861 

112 

603 

431 

361 

683

Pr. ct.

77

0.88 

1.36

.26 

1.00 

1.36 

2.78 

5. 49 

.71 

3.83 

2.71 

2.30 

4.32

Test No.

1

1 ..................

2..................

3..................

4..................

5..................

7..................

8..................

9..................

10 ..................

3.1 ..................

12..................

13 ..................

14..................

Heat balance."

Loss due to moisture 

In fuel (2).

B. t. u.

78

53.1 

64.8 

71.7

55.5

50 

03 

73 

71 

111

34 

49 

33 

 96

78

Pr. ct.

79

0.34 

.41 

.45 

.35 .32' 

.39 

.46 

.45 

.71 

.21 

.31 

.21 

.61 

.50

Ofhydrogen(3).

B. t. u.

80

539 

542.7 

529.9 

525 

542 

530 

573 

591 

588 

506 

574 

577 

553 

75S

Pr. ct.

81

3.43 

3.45 

3.36 

3.32 

3.42 

3.31 

3.63 

3.73 

3.75 

3.19 

3.65 

3.62 

3.53 

4.75

Heat lost in 

dry flue 

gases (4).

B. t. u.

82

2,302 

2,451 

2,603 

2,158 

2,307 

2,384 

2,795 

2, 951 

3,340 

2,089 

3,058 

2,894 

2,821 

4,214

Pr. ct.

83

14.65 

15.60 

16.50 

13.64 

14.56 

14.91 

17.68 

18.61 

21.28 

13.18 

19.43 

18.18 

17.99 

26.56

Loss due to incomplete combustion of carbon in CO (5).

B. t. u.

84

173.6 

79 

186 

107 

176 

139 

113 . 

117 

162 

20 

227 

38 

163

Pr. ct.

85

1.10 

.50 

1.18 

.69 

1.17 

.88 

.78 

.74 

1.02 

.13 

1.43 

.24 

1.03

Loss in escaping 

hydrocarbons, 

radiation, and 

unaccounted 

for (6).

B. t. u.

86

21 

170 

741

335.5

908 

914 

432 

1,043 

1,465 

995 

262 

507 

1,272 

203

PJ-. ct.

87

0.14 

1.08 

4.69 

2.12 

5.74 

5.72 

2.73 

0.56 

9.34 

G.28 

1.66 

3.56 

8.12 

1.28

« Heat-balance items (designated by numbers in parentheses under this heading) are explained in 

Bull. U. S. Geol. Survey No. 325, p. 153. 

6 Sparks collected for two hours only.

NOTES ON INDIVIDUAL TESTS.

Test 1, run-of-mine coal. The coal caked badly; the top of the fuel bed fused over 

and greatly hindered the ascent of air; the.cakes had to be broken with the rake 

very often.

The clinkers were not removed after the close of the test; probably 200 pounds 

were left in the furnace.

Test 2, run-of-mine coal. The coal caked badly, probably because it contained a 

great deal of slack and was wet. The fuel bed had to be raked very often. During 

the first two hours of the test a high "draft" could not be obtained because the relief 

valves had been taken off the steam chests; after 12.15 p. m. the openings were
DATA AND KESULTS OF TESTS. 10

plugged and a higher "draft" was used. A thicker fire was carried without the 

appearance of much CO in the flue gases.

After closing the test the fire was allowed to burn down entirely, the clinkers were 

pulled out, weighed, and charged to the test.

Test 8, run-of-mine coal. The coal caked badly and the fire required frequent raking. The layer of clinkers on the grate at the close of the test was about 3 inches 

thick.

Test 4, run-of-mine coaL The coal swelled in the fire and caked. No sparks were 

caught during this test, their comparative absence probably being due to the fact 

that the draft was lower than during test 1.

Test 5, large briquets.-. The briquets burned freely and quickly, did not cake, but 

stayed together in the fire, which appeared to be very hot. After about 3£ hours 

the fire became unmanageable because a thin but solid layer of clinker had formed 

over the entire grate surface, shutting off the air. The trouble was probably caused 

by rocking the grate too often.

Test 6, large briquets. The briquets burned freely and stayed together. At the 

close of the test there was a layer of clinker on the grate, but it was porous and not

troublesome. The porosity of the clinker was undoubtedly due to the fact that the 

fuel bed was not disturbed at all during the test. Compare notes on test 5. The 

truth is that the best results can be obtained with large briquets by disturbing the 

fire as little as possible. Of course the fire must be occasionally leveled with a rake 

because the briquets can not be thrown in so as to keep the. fuel bed level. Below 

the surface the fire should not be disturbed.

Test 7, large briquets. The briquets stayed together in the fire. The fuel bed was 

easily worked with; during the test it was raked only when leveling it. It seems best 

to disturb the fuel as little as possible, because raking breaks up the briquets and 

rocking the grate causes troublesome clinker. The briquets made a hot fire, burned 

quickly, and smoked very little.

Test S, large briquets. The briquets burned freely and quickly and made a very 

hot, smokeless fire. The fuel bed was not disturbed. No trouble was experienced 

from clinkers at any time, although at the close of the test a 2-inch layer of them 

was found on the grate. They were light and porous and easily removed.

Test 9, run-of-mine coal. The coal caked badly; difficult to keep fire in good condition. Holes were always forming in the fuel bed, so that the latter required frequent raking.

Test 10, small briquets. The briquets burned freely and quickly and stayed together; 'they made a very hot fire which was easily kept in good condition. When 

a thicker fuel bed was carried with a low draft the briquets smoked more than the 

run-of-mine coal would have done under the same conditions. When smoke 

appeared there was also a high percentage of CO in the flue gases.

At the end of the test a layer of clinker about 1J inches thick was on the grate; 

it was porous and light and had given no trouble.

Test 11, small briquets. The briquets made a very hot fire which was easily kept 

in good condition. No difficulty \vas experienced from clinker. After the test only 

a little clinker was found on the grate in the rear of the furnace.

Test 18, small briquets. The briquets made a very hot fire which was easily kept 

in good condition. No trouble was experienced from clinkers; those found on the 

grate at the close of the test were light and porous and in separate pieces, not in a 

continuous layer. The small briquets could be spread more evenly over the grate 

than the large ones. The arch was perhaps too low for the latter.

Test IS, run-of-mine coal. The coal caked badly; holes formed in the fuel bed so 

that it had to be raked frequently; difficulty was experienced in keeping it in good 

condition. After the close of the test the grate was found covered with a layer of 

clinker about 2 inches thick; however, the clinkers had not produced any especial 

trouble.
20 TESTS OF COAL IN A LOCOMOTIVE BOILER.

Test 14, small briquets. For this test all the briquets were weighed before starting 

and placed in the tender. During the test the fire door was closed after each shovelful had been thrown into the furnace. The fire was built up gradually after starting, the '' draft'' being increased with the thickness of the fuel bed. Before the close 

of the test the "draft" was again gradually reduced as the fuel.bed burned down. 

After the test was well under way, and before the fuel bed had started to burn down, 

the rate of combustion was much higher than the average for the whole test. The 

shortness of the test was due to the lack of more briquets.,

About 30 per cent of the briquets used on this test had been crumbled by repeated transfers before they were fired. If they had been in good condition, the 

results undoubtedly would have been better.

EFFECT OF VARYING RATES OF COMBUSTION. 

ON EVAPORATION.

The curves of figure 5 should be used with the scales indicated by 

the respective arrows. The curves labeled B show the relation of 

evaporation to varying rates of combustion, indicating that with all 

the fuels the equivalent evaporation falls off as the rate of combustion 

increases and that such decrease is much more rapid with the runof-mine coal than with either style of briquet. There is not much 

difference between the two kinds of briquets. The last point of the 

small-briquet curve is undoubtedly too low because about 30 per cent 

of the fuel was crumbled when put into the furnace and the crumbled 

particles were blown up from the fire before being burned.

The curves labeled A (fig. 5) were plotted to see whether or not the 

evaporation was lessened by an increased supply of air. The curves 

indicate that within the covered range of rate of combustion the 

weight of air supplied per pound of " combustible " was very nearly 

uniform. This introduces a feature well worth remembering: The 

more rapidly air is supplied to a burning fuel the faster the fuel burns,

and the resulting composition of exit gases remains about the same. 

This feature is discussed more fully in two bulletins by the present authors, one of which has been published 0 and the other, on the 

"Transmission of heat in steam boilers, condensers, etc.," will soon 

be ready for publication.

With the run-of-mine coal the supply of air was somewhat higher 

than with the briquets, which fact probably accounts for the lower 

eyaporation. The larger air supply in the tests on coal was the outcome of the caking characteristics of the coal. Holes and cracks 

formed in the fuel bed, through which streams of air flowed into the 

furnace, thus unduly increasing the air supply, and this in spite of 

constant raking. The smaller supply of air on the tests with small 

briquets as compared with those with large briquets was very likely 

due to the fact that the small ones could be spread over the fuel bed 

much more evenly than the large ones.

a Ray, W. T., and Kreisinger, Henry, Significance of drafts in steam-boiler practice: Bull. U. S. Geol. 

Survey No. 367,1909.
EFFECT OF VAEYING BATES OF COMBUSTION. 21

ON RATED CAPACITY.

The curves labeled C (fig. 5) show the relation between the capacity 

developed by the boiler and the rate of firing dry coal. The rated 

capacity in this case is assumed to be 258.4 boiler horsepower, according to a rule which has been widely adopted in stationary practice 

to the effect that 10 square feet of heating surface are required to supply one boiler horsepower. This rule is, however, not a logical one, 

because area of heating surface is only one of four factors which 

determine the amount of steam produced by a boiler per hour; see 

Bulletin 325° and the above-mentioned bulletin on heat transmission.

50 60 70 80 SO 100 

POUNDS OF DRY FUEL FIRED PER SQ. FT. OF GRATE SURFACE PER HOUR

FIGURE 5. Curves showing relations of rates of combustion to: A, Pounds of dry chimney gases per 

pound of "combustible;" B, equivalent evaporation per pound of dry coal fired; C, per cent of 

rated capacity developed by boiler.

In locomotive practice a boiler horsepower is usually made on much 

less than 10 square feet of boiler heating surface; the above figure 

was taken mainly to have a basis on which to compare the tests 

among themselves and also on which to compare them with other 

tests made by the technologic branch of the Geological Survey. The 

curves show that the capacity increases almost directly with the nominal rate of combustion. With run-of-mine coal the rise is not quite 

so fast as with briquets, because the efficiency of evaporation drops 

off faster.

oBreckenriclge, L. P., A study of four hundred steaming tests: Bull. U. S. Geol. Survey No. 325,1907.
22 TESTS OF COAL IN A LOCOMOTIVE BOILEK.

ON WEIGHT OF SPARKS.

Figure 6 shows the relation between the pounds of sparks escaping 

out of the stack per hour and the rate of firing dry coal on the grate. 

The large briquets are somewhat superior to the small, as might be 

anticipated, because of their relatively smaller surface. Perhaps much 

of the inferiority of the smaller size was due to the incidental fact 

that in consequence of having been handled oftener and more roughly 

before testing they were more broken up; for instance, about 30 per 

cent of the fuel of test 14 had crumbled. In this connection it is 

interesting to note that tumbler tests of the two sizes of briquets show 

chat a larger percentage by weight of the smaller ones chip off, bePOUNDS SPARKS EJECTED FROMTHE HOUR OF MOIST STACK PER

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POUNDS OF DRY FUEL FIRED PER 5Q. FT. OF GRATE SURFACE PER HOUR

FIGURE 6. Relation of weight of sparks collected to rates of combustion.

cause of their greater surface exposed, notwithstanding their rounded 

surface as contrasted with the angular outlines of the larger ones. 

Either shape of briquet is somewhat superior to coal as regards loss 

in sparks. The vertical ordinate (of fig. 6) is in terms of moist sparks; 

sometimes they were dampened by exhaust steam before weighing, 

but chemical anatysis showed the moisture percentage to be negligibly low.

ON HEAT DISTRIBUTION.

Graphic showing. Figures 7 and 8 show the distribution of the 

potential heat of the combustible gasified. The arrow heads near each 

group of curves point to the scales which should be used with each 

particular group.
EFFECT OF VARYING RATES OF COMBUSTION. 23

Heat absorbed by loiter. In figure 7 the curves under B show how 

much of the total heat of the combustible gasified was absorbed by 

the boiler at various rates of combustion; or, in other words, the}' 

show the relation between boiler efficiency (item 72*, Table 2) and the 

rate of putting dry coal on the fire. This boiler efficiency is based on 

the potential heat in the combustible ascending from the grate; the 

amount of combustible ascending is determined by deducting from 

the amount fired that which falls through the 'grate, but not that 

which escapes as sparks. The loss in sparks is given in Table 2 as 

one of the items in the heat balance. In most of the tests the spark 

loss was of little consequence, but in some it deserves consideration,

20

POUNDS

30 40 . 50 60 70 80 90 100 110 

OF DRY FUEL FIRED PER SQ. FT. OF GRATE SURFACE PER.HOUR

FIGURE 7. Curves showing relations of rates of combustion to: A, Per cent of heat unaccounted for; 

B, per cent of heat absorbed by boiler; C, per cent of heat lost in dry chimney gases ("up stack").

especially in test 9, in which it constituted 5.49 per cent of the total 

heat of the combustible which ascended from the grate. Assuming 

that if this heat had been liberated only 65 per cent of it would have 

been absorbed by the boiler, then this 65 per cent of 5.49 per cent 

would have raised the 72* efficiency from 58.69 to about 62.3. In 

test 14 the efficiency 72* would have been about 64.1 instead of 61.56; 

in fact, the improvement of test 14 would have been still greater, 

because all of the sample of sparks was not caught during the latter 

end of the test on account of part of the screen of the spark catcher 

having been worn away.

However, after making due allowance for absorbable heat wasted in 

sparks, it is still true that the efficiency falls.with .increasing steam
24 TESTS OF COAL IN A LOCOMOTIVE BOILER.

production from about 80 to about 65 per cent. The.number of pounds 

of air supplied per pound of "combustible" was about the same in 

all tests, and the gas analysis shows that, at least when using briquets, 

the combustion was nearly as complete at high rates as at low. Why, 

then, is there so large a drop in over-all efficiency?

Some experimental work done by the United States Geological Survey on small multitubular boilers fed with air heated electrically 

showed that if more and more air, all at the same initial temperature, 

were forced through a boiler, the efficiency of the boiler as a heat 

absorber fell rapidly at first (from 100 per cent) and gradually assumed 

a nearly constant value, determined by the characteristics of each boiler. 

This result was, however, obtained with tubes free from soot and scale 

and far enough apart to allow unusually good water circulation. The 

locomotive tubes were fairly clean inside and out, but were so close 

together that the water circulation between them must have been 

greatly hindered. Further, the rate of transmitting heat through the 

tubes was sufficient to cause a considerable rise of tube-metal temperature with rise of capacity, thus lowering the efficiency of the boiler 

as a heat absorber.

Returning now to the locomotive tests, on the whole efficiency from 

coal to steam is higher than that usually obtained from stationary 

boilers; much of the margin is due to the burning quality of the coal, 

but more is due to the high efficiency of the boiler proper, which is a 

consequence of the larger ratio of the length of the tubes to their internal diameter. They are 170 inches long and 2 inches in internal diameter, the ratios of these two values being 170 :2 85, which is much 

greater than is usually the case with stationary multitubular boilers. 

The gases would have left them at about the same temperature if they 

had been twice as long and of twice the diameter, or half as long and 

of half the diameter. 0

This group of curves (B, fig. 7) shows that when burning run-ofnrine coal the percentage of heat absorbed by the boiler dropped rapidly as the rate of combustion increased, but that with the. briquets 

the drop was much smaller.

Loss of heat "up stack" The curves labeled C (fig. 7) indicate that 

the loss of heat in the dry chimney gases rose with the rate of combustion, and that about one-half of the drop in boiler efficiency went 

to increase the loss in the dry chimney gases. For the same rate of 

combustion the chimney loss is larger with the run-of-mine coal than 

with either style of briquet, and it increases faster when the rate of 

combustion increases. The small briquets show a greater loss in £he 

heat in the flue gases than do the large ones; this is perhaps due to 

the probable fact that the flue thermometer was inaccurate and read 

too high. On the last two tests with the small briquets it was noticed

a For a discussion of the effect of changes in the length and-diameter of boiler tubes see Bull. U. S. 

Geol. Survey No. 325,1907, pp. 121-124.
EFFECT OF VARYING BATES OF COMBUSTION. 25

that the mercury thread in the thermometer was very erratic, as 

though the mercury was boiling.

Heat unaccounted for. The group of curves under A (fig. 7) shows 

the relation between the per cent of heat unaccounted for and the 

nominal rate of combustion. The unaccounted-for heat is that left 

after deducting from the potential heat in the coal gasified (as determined by calorimetric analysis) 

(1) Heat absorbed by the boiler;

(2) Heat escaping in the dry flue gases;

(3) Heat lost in heating the moisture of the coal to flue temperature;

(4) Heat lost in heating to flue temperature the moisture formed by the burning 

of the hydrogen of the coal;

(5) Heat lost in burning some of the carbon of the coal to CO only instead of to 

C02 ; and

(6) Beat lost by noncombustion of the carbon of the sparks.

The unaccounted-for heat includes radiation, incomplete combustion

(other than CO loss mentioned above), and all errors of observation 

and instruments, as well as any errors of sampling the coal, ash, and 

sparks, and any very slight errors of analyzing them chemically. In 

other words, an}^ irregularities or false indications in the curves labeled 

A may be due to any of these causes or errors.

The locomotive boiler was well jacketed, so that the radiation was 

very small. It is very likely that the radiation is substantially constant in amount, because it depends only on the temperatures of the 

steam and the outside air, and if it is about constant it decreases in 

percentage as the rate of steam production increases.

The unaccounted-for heat of most of the tests is unusuall}7" small, 

which shows an unusual completeness of combustion, probably due to 

very careful firing and to the fact that most of the tests were on 

briquets of coal which has good burning qualities even when not 

briquetted.

Heat loss in moisture. The group of curves under A in figure 8 

shows the relation between the heat carried away in the moisture of 

the flue gases and the nominal rate of combustion of dry fuel. In the 

moisture is included that in the coal (item 2 in the heat balance) and 

that formed by burning the h}7 drogen of the coal (item 3 of the heat 

balance). All the curves show a slight increase. Inasmuch as the 

amounts of moisture and hydrogen in the coal and the briquets is 

nearly the same for all tests, the increase is undoubtedly due to the 

rise of flue-gas temperature.

Heat loss in CO. In this same figure 8 the curves labeled B show 

the relation between the heat lost in burning some of the carbon of 

the coal to CO only (instead of to CO2 ) and the nominal rate of combustion. The curves are somewhat irregular, but they seem to indicate that more heat is lost in CO when burning briquets than when 

burning run-of-mine coal;.the small briquets show a greater loss than 

the larger ones. The larger loss with briquets is very likely due to
26 TESTS OF COAL IN A LOCOMOTIVE BOILER.

the fact that less air was used with them than with the run-of-mine 

coal.

Heat loss in sparks. The group of curves marked C (fig. 8) shows 

that as the nominal rate of combustion increases the loss in sparks 

rises. The rise is greater with run-of-mine coal than with either kind 

of briquet, and greater with the small briquets than with the large 

ones. The higher loss from the coal is undoubtedly due to the presence of slack, which is partly carried through the flues without burning. Some of the small briquets were more or less crumbled when

10 20 30 40 SO 60 70 80 90 100 no

POUNDS OF DRY FUEL FIRED PER SQ. FT. OF GRATE SUFACE PER HOUR

FIGURE 8. Curves showing relations of rates of'combustion to: A, Per cent of heat lost in moisture 

in chimney gases (that is, in the free moisture of the coal plus the moisture formed by the burning of hydrogen); B, per cent of heat lost by burning some of the carbon only to CO instead of to 

C02| C, per cent of heat lost as sparks.

fired, so it is probable that their higher loss in sparks was due to the 

fact that some of the finer particles were carried up unburned.

ON COST OF STEAM.

Figure 9 shows the relative costs of steam when run-of-mine coal 

and the two kinds of briquets are burned at various rates. -The scale 

at the left is based on the assumption that the raw coal costs $2.50 per 

ton in the tender; the cost of steam from it is obtained directly from 

the equivalent evaporation. The cost of steam from the briquets is 

obtained by multiplying the values similar^ obtained from the equivalent evaporation by 112.5,125,137.5, and 150 per cent, to cover various
EFFECT OF VARYING RATES OF COMBUSTION. 27

costs of briquetting. Thus the briquet curves labeled 1.125 give the 

cost of steam if the briquets cost 1.125 times as much as run-of-mine 

coal on the tender; the briquet curves labeled 1.25 give the cost,of 

steam if the briquets cost 1.25 times as much.as run-of:inine coal, and 

so on. In computing all these costs of steam no allowance was made 

for the labor of the fireman, for water, for repairs, depreciation, etc. 

It may be stated with reasonable safety that it is easier for a fireman 

to fire li tons, or even 1^ tons, of briquets than a ton of coal in the 

same time, for he is saved the raking. The curves show that at low

.10 ao .30 4O so eo TO eo so 100 no

POUNDS OF DRY FUEt FIRED PER §Q. FT. OF GRATE SURFACE'PER HOUR

FIQUHF. 9. Curves showing relative costs of steam per 1,000 pounds when burning run-of-mine coal 

and two kinds of briquets at various costs for briquetting, all at various rates of combustion: The 

assumed basis of cost for coal is 82.50 per ton of 2,000 pounds. The figures at the upper end of each 

briquet curve indicate the cost of briquets for comparison with the cost of the coal, which is taken 

as unity.

rates of combustion it does not pay to burn briquets; nevertheless, as 

the rate increases the cost of steam, when generated from, run-of-mine 

coal, rises very rapidly, so that when burning 60 or 70 pounds per 

square foot of grate per hour the briquets give better economy. 

With a well-equipped briquetting plant the cost of making briquets 

should not exceed $1.25 to $1.50 per ton, to which must be added the 

cost of the coal, which, if the briquetting is done at the mine and 

slack coal used, may be placed at a very low figure. Inasmuch as 

locomotives are already worked at high rates of combustion, and as 

higher and higher rates will be desired, the use of briquets has a 

rather promising future in steam-locomotive service.
28 TESTS OF COAL IN A LOCOMOTIVE BOILER.

ADVANTAGES OF BRIQUETS FOR LOCOMOTIVE USE.

Higher equivalent evaporation. At higher rates of combustion briquets give better equivalent evaporation than run-of-mine coal. According to figure 5 (p. 21), as the nominal rate of combustion increases 

beyond 50 pounds of fuel per square foot of grate surface per hour 

.the evaporation from briquets remains increasingly higher than from 

coal. In present locomotive practice the usual rate of combustion is 

about 65 pounds, at which rate the briquets give about 10 per cent 

higher equivalent evaporation. At an 80-pound rate the evaporation 

is about 15 per cent higher than with coal.- For still higher rates the 

discrepancy is still higher.

The cost of steam from briquets is of course increased by the cost 

of briquetting- the coal, which, with a well-equipped plant, and especially when working up slack, should not exceed the cost of run-ofmine coal by more than 12 to 15 per cent. Ity consulting figure 9 

(p. 27) it will be seen that at such a cost of briq netting the cost of 

steam, at the present usual rate of combustion (65 pounds) would be 

somewhat lower from the briquets.

Ease of manipulating fires. The burning qualities of briquets are 

so much superior to those of ordinary run-of-mine coal as to cause 

the fireman much less work. The fact that usually a briquet fuel bed 

had better not be disturbed for hours makes it possible to burn fuel 

much faster with no more labor. (Compare under "Notes on individual tests," beginning at p. 18.) > '

Possible increase in rate of steam production. Owing to the feasibility of burning briquets much faster than run-of-mine coal with the 

same "draft," it is possible to increase the tractive power of present 

locomotives, and thus shorten the time required to pull a given train

over a certain road or to increase the train load.

It may be possible to increase the present steaming ability of 

locomotives by 25 or even 50 per cent; part of this increase may possibly be obtained by providing different exhaust nozzles, such as 

will produce greater pressure drops ("drafts") through the fuel bed 

and boiler, with the same expenditure of energy; that is, with the 

same back pressure on the pistons. (See under "Suggested changes 

in design and construction of locomotive," p. 30.) By simultaneously 

changing fuel from run-of-mine to briquetted coal this margin might 

be further increased. The resulting increase in the earning power of 

a locomotive would be accompanied by some increase in operating 

expenses.

Table 3 gives tentative figures, indicating what may be expected 

when increasing the hauling power of present locomotives. According to the statistics of the Interstate Commerce Commission, in 1906 

the average freight locomotive earned about $70,000, gross. The 

operating expenses of the average railroad were 70 per cent of its
GENERAL DEDUCTIONS. 29

operating income, and the remaining 30 per cent went to pay incidental expenses, bond interest, note interest, insurance, dividends, 

betterments, and to surplus.

To make our problem simpler, it is assumed that only the operating expenses would increase directly with the increase in earning 

power per locomotive probably a safe assumption; for certainly 

some of the operating expenses would not be increased, and the others 

would not increase as fast as the earnings per locomotive.

The table speaks in favor of increasing the hauling power. 

Nevertheless the figures are tentative only, being derived through 

rough and simple approximations; for any division of any road all 

details should be carefully included.

.TABLE 3. Estimated results of increasing the haulage poiver of freight locomotives.

Rate of working freight 

locomotive.

Increased by 25 per cent .... 

Increased by 50 per cent ....

Average 

ton-miles 

per annum 

per freight locomotive.

7, 000, 000 

8,750,000

10,500,000

Per average freight locomotive.

Earnings.

Dollars. 

70, 000

87,500 

105,000

Per cent. 

100

100 

100

Operating cost.

Dollars. 

49,000 

( 49,000 

|+ 6,125

1 55,125 

149,000 

+12,250

61, 250

Per cent. 

70

1 63.4 

1 58.3

Net earnings.

Dollars. 

21,000

32,375 

33, 750

Per cent. 

30

36.6 

41.7

oFrom report of Interstate Commerce Commission for 1906. 

DISADVANTAGES OF BRIQUETS FOR LOCOMOTIVE USE.

/Storage capacity. When briquets are shoveled or dropped into a 

tender spaces are always left, which, in the case of run-of-mine coal, 

are largely filled with slack. The presence of these air spaces reduces 

the capacity of the tender 20 to 28 per cent. Of course the large 

so-called "square" briquets could be laid up like bricks by hand, so 

as to leave almost no vacant spaces, but the extra trouble probably 

would not pay.

Difficulty of shoveling. When first beginning to handle briquets 

most firemen have considerable difficulty in getting them into the 

scoop; the annoyance often founds a prejudice. Intelligent effort will 

eliminate the trouble, especialty with the small ovoid shape.

GENERAL DEDUCTIONS.

At the usual rate of combustion in locomotives the equivalent evaporation with either kind of briquet is 10 to 15 per cent higher than with 

run-of-mine coal.

So far as blackness of smoke is concerned there seems to be little 

advantage in briquets over run-of-mine coal. However, the loss in 

sparks is less, and especially with the larger size of briquets.
30 TESTS OF COAL IF A LOCOMOTIVE BOILER.

It is a great deal easier to raise and to keep up steam with briquets 

than with run-of-mine coal. Higher rates of combustion are feasible, 

and consequently higher power, which is of especially great advantage 

on long grades.

As to efficiency, there is practically no difference between the two 

kinds of briquet, but the smaller ones are easier to handle.

SUGGESTED CHANGES IN DESIGN AND CONSTRUCTION OF

LOCOMOTIVE..

Grate and combustion chamber. Although the combustion of this 

particular coal and of briquets made therefrom was very complete, 

combustion is not usually at all good with most of the coals of the 

country, even when briquetted. The fire-brick arches of this type of 

boiler are undoubtedly of great benefit in mixing the gases and in 

igniting freshly fired coal, but some roads object to them because they 

interfere with stay-bolt inspection. The great trouble is that the 

time elapsing between the instant the gases leave the fuel bed and the 

instant they enter the tubes is much too short with ordinary coals. One 

way of materially remedying this trouble, which is being more and more 

employed, is to add a " combustion chamber" inside the cylindrical 

portion of the boiler, opening out of the front side of the fire box. 

To accomplish much improvement this additional length of gas travel 

must amount to several feet. It is usual to keep the fire tubes .the 

same length and to make the whole boiler so .much longer a subterfuge to which there are practical objections.

Dimensions of fire tubes. In Bulletin 325 a there is an extended 

discussion, touching, among other things, on the ratios between the 

length and diameter of boiler tubes as affecting their efficiency and 

capacity as heat absorbers. Specifically stated for the present case, 

if ths tubes were made half as long and of half the internal diameter, 

the gases would leave them a little cooler than now; if they were 

made two-thirds as long, and of two-thirds the internal diameter, the 

gases would also still leave them a little cooler than now. That is, the 

efficiency of a tube? aside from slight modifying factors, depends 

solely on the ratio of its length to its internal diameter, other conditions of cleanliness, etc., being the same. This sameness of efficiency 

is nearly independent of the amount of gas passing through. It is 

certainly the case that if the tubes were made half as long, of half 

the internal diameter, and if four times as many were used (to give 

the same area of flow for the gases), then the total weight of gas passing through per minute would be fully as great, and the total amount 

of heat absorbed somewhat greater. It is indeed probable that the 

number of tubes would not have to be quadrupled for the same 

" draft" in the smoke box, but perhaps only doubled.

a- JJreckenridge, L. P., op. cit., p. 121-124.
BIBLIOGRAPHY. 31

One objection to making- the tubes smaller is that they would choke 

up more quickly; nevertheless the authors have sometimes observed 

that about one-third of the tubes of locomotives are choked up anyhow within a short time after cleaning, although such is probably not 

the general condition of such boilers. The higher velocity of gas 

through the smaller tubes should tend to keep them clean, unless they 

fill up at the entrance.

It is well here to introduce a short calculation of the efl'ect of 

reduced dimensions on the strength of tubes against shearing (" cutting off") at the tube sheets. Suppose the tube to be halved in all its 

dimensions, including thickness, then it will weigh one-eighth as much 

and have one-half the bearing surface in tube sheets of the same thickness as before; it is therefore about one-fourth as likely to cut off, 

although the reasoning is mathematically only approximate.

As to bending, the tube may be considered to be a beam uniformly

subjected along its entire length to a live load of its own weight, 

though here again the reasoning is only approximate. A calculation 

with formulas for hollow cylinders used as beams shows that the 

smaller tube will be one-half as apt to bend from jarring.

"Draft" production. The function of a locomotive called "draft" 

production is so intimately connected with speed, steam pressure, per 

cent of cut-off, etc., that it would probably be hard to'greatly improve 

nozzles,; the very fact that the present shapes are the result of a long 

evolution is fair evidence that they are reasonably satisfactory, especially when we recall that the Master Car Builders' Association has 

experimented considerably on nozzles. Figure 4: shows the nozzle of 

this locomotive, which is representative of a type commonly used.

Nevertheless, it is hard for a layman to believe that it is necessary 

to absorb so large a part of the possible power in moving air through 

the fuel bed and boiler tubes; if nothing can be done to make nozzles 

more efficient, there is likely hope in the direction of utilizing some of 

the unavoidable impact of the locomotive front against the air; the fact 

that certain experiments of this kind have failed is not conclusive 

negation. The tests herein described show that this one boiler is capable of producing enough steam for two or three locomotives; part of 

the increase could be utilized in this one locomotive, providing the 

"draft" was economically obtainable and more weight was put on the 

drivers; or, in western portions of the United States,-the gain could 

be utilized in making better time or by pulling longer trains when 

using poorer coals than are commonly used at present.

SURVEY PUBLICATIONS ON FUEL TESTING AND 

BRIQUETTING.

The following publications, except those to which a price is affixed, 

can be obtained free by applying .to the Director, Geological* Survey, 

Washington, D. C. The priced publications can be purchased from
32 TESTS OP COAL IN" A LOCOMOTIVE BOILEK.

the Superintendent of Documents, Government Printing Office, 

Washington, D. C.

BULLETIN 261. Preliminary report on the operations of the coal-testing plant of the

United States Geological Survey at the Louisiana Purchase Exposition, in St.

Louis, Mo1., 1904; E. W. Parker, J. A. Holmes, M. R. Campbell, committee in

charge. 1905. 172 pp. 10 cents. 

PROFESSIONAL PAPER 48. Report on the operations of the coal-testing plant of the

United States Geological Survey at the Louisiana Purchase Exposition, St. Louis,

Mo., 1904; E. W. Parker, J. A. Holmes, M. R. Campbell, committee in charge.

1906. In three parts. 1492pp., 13 pis. $1.50. 

BULLETIN 290. Preliminary report on the operations of the fuel-testing plant of the

United States Geological Survey at St. Louis, Mo., 1905, by J. A. Holmes. 1906.

240 pp. 20 cents. 

BULLETIN 323. Experimental work conducted in the chemical laboratory of the

United States fuel-testing plant at St. Louis, Mo., January 1, 1905, to July 31,

1906, by N. W. Lord. 1907. 49 pp. 10 cents. 

BULLETIN 325. A study of four hundred steaming tests, made at the fuel-testing

plant, St. Louis, Mo., 1904,1905, and 1906, by L. P. Breckenridge. 1907. 196 pp.

20 cents. 

BULLETIN 332. Report of the United States fuel-testing plant at St. Louis, Mo.,

January 1, 1906, to June 30, 1907; J. A. Holmes, in charge. 1908. 299 pp. 

BULLETIN 334. The burning of coal without smoke in boiler plants; a preliminary

report, by D. T. Randall. 1908. 26pp. 5 cents. (See Bull. 373.) 

BULLETIN 336. Washing and coking tests of coal and cupola tests of coke, by Richard

Moldenke, A. W.. Belden, and G. R. Delamater. 1908. 76 pp. 10 cents. 

BULLETIN 339. The purchase of coal under government and commercial specifications on the basis of its heating value, with analyses of coal delivered under

government contracts, by D. T. Randall. 1908. 27 pp. 5 cents. See Bull. 378. 

BULLETIN 343. Binders for coal briquets, by J. E. Mills. 1908. 56 pp. 

BULLETIN 362. Mine sampling and chemical analyses of coals tested at the United

States fuel-testing plant, Norfolk, Va., in 1907, by J. S. Burrows. 1908. 23 pp.

5 cents. 

BULLETIN 363. Comparative tests of run-of-mine and briquetted coal on locomotives,

including torpedo-boat tests and some foreign specifications for briquetted fuel,

by W. F. M. Goss. 1908. 57 pp., 4 pis. 

BULLETIN 366. Tests of coal and briquets as fuel for house-heating boilers, by D. T.

Randall. 1908. 44 pp., 3 pis. 

BULLETIN 367. Significance of drafts in steam-boiler practice, by W. T. Ray and

Henry Kreisinger. 1909. 61 pp. 

BULLETIN 368. Washing and coking tests of coal at Denver, Colo., by A. W. Belden,

G. R. Delamater, and J. W. Groves. 1909. 54 pp., 2 pis.. 

BULLETIN 373. The smokeless combustion of coal in boiler plants, by D. T. Randall

and H. W. Weeks. 1909. 188 pp! 

BULLETIN 378. Results of purchasing coal under government specifications, by J. S.

Burrows; Burning the small sizes of anthracite for heat and power purposes, by

D. T. Randall. 1909. 44 pp. 

BULLETIN 385. Briquetting tests at Norfolk, Va., by C. L. Wright. 1909. 41pp.,

9 pis. 

BULLETIN 403. Comparative tests of run-of-mine and briquetted coal on the torpedo

boat Biddle, by W. T. Ray and Henry Kreisinger. 1909.

MINERAL RESOURCES, 1907. Coal briquetting in 1907, by E. W. Parker, pp. 223-228. 

MINERAL RESOURCES, 1908 "Jo.7 L t -iquetting in 1908, by E. W. Parker. 1909.

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