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LIBRARY
UNIVERSITY , OF CALIFORNIA,
RECEIVED BY EXCHANGE
Class
UNIVERSITY OF ILLINOIS BULLETIN
Vol. VI. SEPTEMBER 1, 1908 No. I
[Entered Feb. 14, 1902, at Urbana, 111., as second-class matter under Act of Congress July 16, 1894]
BULLETIN NO. 26
HIGH STEAM-PPvESSURES IN
LOCOMOTIVE SERVICE
(A REVIEW OF A REPORT TO THE CARNEGIE INSTITUTION OF
WASHINGTON)
BY
W. F. M. GOSS
UNIVERSITY OF ILLINOIS
ENGINEERING EXPERIMENT STATION
URBANA, ILLINOIS
PUBLISHED BY THE UNIVERSITY
HE Engineering Experiment Station was established by
action of the Board of Trustees December 8, 1903. It is
the purpose of the Station to carry on investigations
along various lines of engineering and to study problems
of importance to professional engineers and to the manu-
facturing, railway, mining, constructional, and industrial interests
of the State.
The control of the Engineering Experiment Station is vested
in the heads of the several departments of the College of En-
gineering. These constitute the Station Staff, and with the Di-
rector, determine the character of the investigations to be under-
taken. The work is carried on under the supervision of the Staff;
sometimes by a research fellow as graduate work, sometimes by
a member of the instructional force of the College of Engineer-
ing, but more frequently by an investigator belonging to the
Station cprps.
The results of these investigations are published in the
form of bulletins, which record mostly the experiments of the
Station's own staff of investigators. There will also be issued
from time to time in the form of circulars, compilations giving
the results of the experiments of engineers, industrial works,
technical institutions, and governmental testing departments.
The volume and number at the top of the title page of the
cover are merely arbitrary numbers and refer to the general publi-
cations of the University of Illinois; above the title is given the
number of the Engineering Experiment Station bulletin or circular^
which should be used in referring to these publications.
For copies of bulletins, circulars or other information,
address the Engineering Experiment Station, Urbana, Illinois.
CONTENTS
HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE
Introduction: A Summary of Conclusions
Page
I. The Research and the Means Employed in Its Ad-
vancement , 6
II. Difficulties in Operating under High- Pressures 11
III. Boiler Performance 12
IV. Engine Performance 19
V. Machine Friction and Performance at Draw- Bar. . . 26
VI. Boiler Pressure as a Factor in Economical Opera-
tion 32
VII. Boiler Capacity as a Factor in Economical Opera-
tion 36
VIII. Conclusions Concerning Boiler-Pressure vs. Boiler
Capacity as a Means of Increasing the Efficiency
of a Single-Expansion Locomotive 40
182022
PREFACE
The Report on High Steam- Pressures in Locomotive Service,
issued by the Carnegie Institution of Washington as Serial No.
66, is a publication of 144 pages dealing with a research which was
carried on in the laboratory of Purdue University during the wri-
ter's connection with that University. It illustrates and describes
the locomotive and other apparatus employed, and presents in
tabulated and graphical form the full record of observed and de-
rived results. In this Review, the text of the Report has been
freely quoted, and the conclusions and arguments by which they
are sustained appear as given in the original publication. The
Review, therefore, takes the form of a resume of the research and
its results, the complete record of which is available elsewhere.
In the editorial work incident to the preparation of this
Review, Mr. Paul Diserens has had an important share.
W. F. M. G.
December, 1908.
UNIVERSITY OF ILLINOIS
ENGINEERING EXPERIMENT STATION
BULLETIN No. 26 SEPTEMBER 1908
HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE
(A Review of a Report bo the Carnegie Institution of Washington)
BY W. F. M. Goss, DEAN OF THE COLLEGE OF ENGINEERING AND
DIRECTOR OF THE SCHOOL OF RAILWAY ENGINEERING AND
A DMINISTR ATION
INTRODUCTION
A SUMMARY OF CONCLUSIONS
The results of the study concerning the value of high steam -
pressures in locomotive service, the details of which are presented
in succeeding pages, may be summarized as follows:
1. The results apply only to practice involving single- expan-
sion locomotives using saturated steam. Pressures specified are
to be accepted as running pressures. They are not necessarily
those at which safety valves open.
2. Tests have been made to determine the performance of a
typical locomotive when operating under a variety of conditions
with reference to speed, power, and steam-pressure. The results
of one hundred such tests have been recorded.
3. The steam consumption under normal conditions of run-
ning has been established as follows:
Boiler pressure 120 Ib. , steam per indicated horse-power hour 29.1 Ib.
Boiler pressure 140 Ib., steam per indicated horse-power hour 27.7 Ib.
Boiler pressure 160 Ib., steam per indicated horse-power hour 26.6 Ib.
Boiler pressure 180 Ib., steam per indicated horse-power hour 26.0 Ib.
Boiler pressure 200 Ib., steam per indicated horse- power hour 25.5 Ib.
Boiler pressure 220 Ib., steam per indicated horse-power hour 25.1 Ib.
Boiler pressure 240 Ib., steam per indicated horse-power hour 24.7 Ib*
4 ILLINOIS ENGINEERING EXPERIMENT STATION
4. The results show that the higher the pressure, the smaller
the possible gain resulting from a given increment of pressure.
An increase of pressure from 160 to 200 Ib. results in a saving of
1.1 Ib. of steam per horse-power hour, while a similar change from
200 Ib. to 240 Ib. improves the performance only to the extent of
0.8 Ib. per horse- power hour.
5. The coal consumption under normal conditions of running
has been established as follows:
Boiler pressure 120 Ib., coal per indicated horse-power hour 4.00 Ib.
Boiler pressure 140 Ib., coal per indicated horse-power hour 3.77 Ib.
Boiler pressure 160 Ib., coal per indicated horse-power hour 3.59 Ib.
Boiler pressure 180 Ib., coal per indicated horse-power hour 3.50 Ib.
Boiler pressure 200 Ib., coal per indicated horse-power hour 3.43 Ib.
Boiler pressure 220 Ib., coal per indicated horse-power hour 3.37 Ib.
Boiler pressure 240 Ib., coal per indicated horse-power hour 3.31 Ib.
6. An increase of pressure from 160 to 200 Ib. results in a
saving of 0.16 Ib. of coal per horse-power hour, while a similar
change from 200 to 240 Ib. results in a saving of but 0.12 Ib.
7. Under service conditions, the improvement in performance
with increase of pressure will depend upon the degree of perfec-
tion attending the maintenance of the locomotive. The values
quoted in the preceding paragraphs assume a high order of main-
tenance. If this is lacking, it may easily happen that the saving
which is anticipated through the adoption of higher pressures will
entirely disappear.
8. The difficulties to be met in the maintenance both of boiler
and cylinders increase with increase of pressure.
9. The results supply an accurate measure by which to deter-
mine the advantage of increasing the capacity of a boiler. For
the development of a given power, any increase in boiler capacity
brings its return in improved performance without adding to the
cost of maintenance or opening any new avenues for incidental
losses. As a means to improvement, it is more certain than that
which is offered by increase of pressure.
10. As the scale of pressure is ascended, an opportunity to
further increase the weight of a locomotive should in many cases
find expression in the design of a boiler of increased capacity
rather than in one for higher pressures.
11. Assuming 180 Ib. pressure to have been accepted as stand-
ard, and assuming the maintenance to be of the highest order, it
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 5
will be found good practice to utilize any allowable increase in
weight by providing a larger boiler rather than by providing a
stronger boiler to permit higher pressures.
12. Wherever the maintenance is not of the highest order, the
standard running pressure should be below 180 Ib.
18. Wherever the water which must be used in boilers con-
tains foaming or scale- making admixtures, best results are likely
to be secured by fixing the running pressure below the limit of
180 Ib.
14. A simple locomotive using saturated steam will render
good and efficient service when the running pressure is as low as
160 Ib. ; under most favorable conditions, no argument is to be found
in the economic performance of the engine which can justify the
use of pressures greater than 200 Ib.
ILLINOIS ENGINEERING EXPERIMENT STATION
HIGH STEAM^PRESSURES IN LOCOMOTIVE SERVICE
I. THE RESEARCH AND THE MEANS EMPLOYED IN ITS
ADVANCEMENT
1. Steam- Pressures in Locomotive Service. — For many years
past there has been a gradual but nevertheless a steady increase
in the pressure of steam employed in American locomotive service.
Between 1860 and 1870 a pressure of 100 Ib. per sq. in. was com-
mon. Before 1890 practice had carried the limit beyond 150 Ib.
At the present time 200 Ib. is most common, but an occasional re-
sort to pressures above this limit suggests a disposition bo ex-
ceed it.
High steam-pressure does not necessarily imply high power.
It is but one of the factors upon which power depends. The
forces which are set up by the action of the engine are as much
dependent upon cylinder volume as upon boiler-pressure, and
when the pressure is once determined the cylinders may be de-
signed for any power. The limit in any case is to be found when
the boiler can no longer generate sufficient steam to supply them.
The relation between pressure and power is therefore only an in-
direct one. But anything which makes the boiler of a locomotive
more efficient in the generation of steam, or the engines more eco-
nomical in their use of steam, will permit an extension in the limit
of power. If, for example, it can be shown that higher steam-
pressure promotes economy in the use of steam, higher steam-
pressure at once becomes an indirect means for increasing power.
The fact to be emphasized is that an argument in favor of higher
steam- pressures must concern itself with the effects produced up-
on the economic performance of the boiler or engine.
2. Preparations for an Experimental Study. — In view of the
facts stated, and with the hope of ascertaining a logical basis
from which to determine what the pressure should be for a sim-
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE t
pie locomotive, using saturated steam, it was long ago deter-
mined to undertake an experimental study of the problem upon
the testing plant of Purdue University. A few experiments in-
volving the use of different steam-pressures in locomotive service
were made at Purdue as early as 1895. but as the boiler of the
locomotive then upon the testing- plant was not capable of with-
standing pressures greater than 150 lb., these early tests were
limited in their scope.1 The matter was, however, regarded as of
such importance that in designing a new locomotive for use up-
on the plant, a pressure of 250 lb. was specified — a limit which
then was and still is considerably in advance of practice. Thus
equipped, an elaborate investigation was outlined, involving a
series of tests under six different pressures, representing a suffi-
cient number of different speeds and cut-offs to define the perform,
ance of the locomotive under a great range of conditions. But the
expense of operating the locomotive under very high steam- pres-
sures proved to be so great that the limited funds which could be
devoted to the operations of the laboratory, in combination
with the demands of students, which could be most easily satisfied
by work under lower pressures, made it impracticable for a time
to proceed with the work. A grant from the Carnegie Institution
of Washington was announced late in the fall of 1903. The first
test in the Carnegie series was run February 15, 1904, and the
last August 7, 1905. A registering counter attached to the loco-
motive shows that between these dates the locomotive drivers
made 3,113,833 revolutions, which is equivalent to 14,072 miles.
3. The Tests. — The tests outlined included a series of runs for
which the average pressure was to be, respectively, 240, 220, 200,
180, 160, and 120 lb., a range which extends far below and well a-
bove pressures which are common in present practice. It was
planned to have the tests of each series sufficiently numerous to
define completely the performance of the engine when operated
under a number of different speeds and when using steam in the
cylinders under several degrees of expansion. As far as prac-
ticable, each test was to be of sufficient duration to permit the ef-
ficiency of the engine and boiler to be accurately determined, but
where this could not be done cards were to be taken. A precise
statement of the conditions under which, in the development of
1 Results of these tests will be found published in Locomotive Performance. John Wiley
& Sons.
8
ILLINOIS ENGINEERING EXPERIMENT STATION
this plan, the tests were actually run. is set forth diagrammati-
cally in Fig. 1 to 6 accompanying, in which vertical distances rep-
resent speed, and horizontal distances the point of cut-off as de-
termined by the notch occupied by the latch of the reverse lever,
counting from the center forward. Each complete circle in these
diagrams represents an efficiency test, and each dotted circle, a
shorter test under conditions involving the development of power
in excess of that which could be constantly sustained. The nu-
merals within the circles refer to the laboratory numbers by
which the several tests are identified.
I 60
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FIG. 6
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE
4. The locomotive upon which the tests were made is that
regularly employed in the laboratory of Purdue University, where
it is known as Schenectady No. 2. It was ordered of the Schenec-
tady Locomotive Works in 1897. In selecting a second locomo-
tive which should serve the purposes of the Purdue testing- plant,
it was decided to have the boiler of substantially the same capac-
ity as that of the locomotive previously employed in the labora-
tory and which in later years has been known as Schenectady No. 1.
In some other respects the new locomotive differed from its pred-
ecessor. Its boiler was designed to operate under pressures as
high as 250 Ib. , a limit which was then 25 per cent higher than
the maximum employed in practice. Horizontal seams are butt-
jointed with welt strips inside and out, and are sextuple- riveted.
The design of its cylinders and saddle is such as readily to per-
mit the conversion of the simple engine into a two-cylinder com-
pound. The driving-wheels of the new locomotive are of larger
diameter than those of Schenectady No. 1.
FIG. 7 OUTLINE ELEVATION OF LOCOMOTIVE
The principal characteristics of the locomotive are as follows:
Type ,
Total weight pounds
Weight on four drivers pounds
Valves: type, Bichardson balanced
Maximum travel inches
Outside lap inches
Inside lap inches
Ports:
Length inches
Width of steam port inches
Width of exhaust port inches
Total wheel base feet
109 000
61 000
0
12.0
1.5
3.0
23
10 ILLINOIS ENGINEERING EXPERIMENT STATION
Rigid wheel base feet 8.5
Cylinders:
Diameter inches 16
Stroke inches 24
Drivers, diameter front tire inches 69 . 25
Boilers, (style, extended wagon-top:)
Diameter of front end inches 52
Number of tubes 200
Gage of tube 12
Diameter of tube inches 2
Length of tube feet 11.5
Length of fire-box inches 72 . 06
Width of fire-box inches 34.25
Depth of fire-box inches 79.00
Heating-surface in fire-box square feet 126.0
Heating-surface in tubes, water side square feet 1196.00
Heating-surface in tubes, fire side. square feet 1086.00
Total heating-surface including water side
of tubes square feet 1322.00
Total heating-surface including fire side
of tubes square feet 1212.00
Total heating-surface, value accepted for
use in all calculations square feet 1322.00
Ratio of total heating-surface based on
water side of tubes to that based on fire
side of tubes 1.091
Grate area square feet 17.00
Thickness of crown-sheet inches TV
Thickness of tube sheet inches ^
Thickness of side and back sheets inches f
Diameter of stay-bolts inches 1
Diameter of radial stays inches 1 &
Driving-axle journals:
Diameter inches 7 1
Length inches 8 i
5. An Alternative for Higher Steam-pressures. — Previous pub-
lications from the Purdue laboratory have shown the possibility
under certain conditions of finding a substitute for very high
boiler-pressures in the adoption of a boiler of larger capacity,
the pressure remaining unchanged. If, for example, in design-
ing a new locomotive, it is found possible to allow an increase of
weight in the boiler, as compared with that of some older type of
machine, it becomes a question as to whether this possible in-
crease in weight should be utilized by providing for a high- pres-
sure or for an increase in the extent of heating- surf ace. The re-
sults of tests, supplemented by facts concerning the weight of
boilers designed for different pressures and for different capac-
ities, supply the data necessary for an analysis of this question.
Such an analysis is presented elsewhere. (See Chapters VI and
VII.)
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 11
II. DIFFICULTIES IN OPERATING UNDER HIGH-PRESSURES
6. The Work with the Experimental Locomotive has shown
that those difficulties which in locomotive operation are usually
ascribed to bad water increase rapidly as the pressure is increased.
The water-supply of the Purdue laboratory contains a consider-
able amount of magnesia and carbonate of lime. When used in
boilers carrying low pressure there is no great difficulty in wash-
ing out practically all sediment. The boiler of the first experi-
mental locomotive, Schenectady No. 1, which carried but 140 Ib.
and was run at a pressure of 130 Ib. , after serving in the work
of the laboratory for a period of six years, left the testing- plant
with a boiler which was practically clean. Throughout its period
of service this boiler rarely required the attention of a boiler-
maker to keep it tight. Water from the same source was ordin-
arily used in the boiler of Schenectady No. 2, which carried a pres-
sure of 200 Ib. or more. It was early found that this boiler
operating under the higher pressure frequently required the at-
tention of a boiler-maker. After having been operated for no
more than 30,000 miles, cracks developed in the side'-sbeets, mak-
ing it impossible to keep the boiler tight, and new side- sheets
were applied. In operating under pressures as high as 240 Ib.,
the temperature of the water delivered by the injector was so
high that scale was deposited in the check-valve, in the delivery-
pipe, and in the deli very- tube of the injector. Under this pres-
sure, with the water normal to the laboratory, the injectors often
failed after they had been in action for a period of two hours.
The interruptions of tests through failure of the injector, and
through the starting of leaks at stay-bolts, as the tests proceeded,
became so annoying that, as a last resort, a new source of water
supply was found in the return tank of the University heating-
plant. This gave practically distilled water, and its use greatly
assisted in running the tests at 240 Ib. pressure.
Probably some of the difficulties experienced in operating
under very high steam- pressures were due to the experimental
character of the plant, and would not appear after practice had
become committed to the use of such pressures by a gradual pro-
cess of approach, but the results are clear in their indication that
the problem of boiler maintenance, especially in bad- water dis-
tricts, will become more complicated as pressures are further in
12 ILLINOIS ENGINEERING EXPERIMENT STATION
creased. Since, taking the country over, there are few localities
where locomotives can be furnished with pure water, the conclu-
sion stated should be accepted as rather far-reaching in its effect.
The tests developed no serious difficulties in the lubrication of
valves and pistons under pressures as high as 240 Ib. , though
this could not be done with the grade of oil previously employed.
With increase of pressure any incidental leakage, either of the
boiler or from cylinders, becomes more serious in its effect upon
performance. In advancing the work of the laboratory, every
effort was made to prevent loss from such causes, and tests were
frequently thrown out and repeated because of the development
of leaks of steam around piston and valve rods, or of water from
the boiler. Notwithstanding the care taken, it was impossible
under the higher pressures to prevent all leakage, and the best
that can be said for the data under these conditions is that they
represent results which are as free as practicable from irregular-
ities arising from the causes referred to; that is, as far as leak-
age may affect performance, the results of the laboratory tests
may safely be accepted as a record of maximum performance.
In concluding this brief review of the difficulties encountered
in the operation of locomotives under very high steam-pressures,
the reader is reminded that an increase of pressure is an
embellishment to which each detail in the design of the whole ma-
chine must give a proper response. A locomotive which is to oper-
ate under such pressure will need to be more carefully designed
and more perfectly maintained than a similar locomotive designed
for lower pressure; and much of that which is crude and imperfect,
but nevertheless serviceable in the operation of locomotives us-
ing a lower pressure, must give way to a more perfect practice in
the presence of the higher pressure.
III. BOILER PERFORMANCE
7. The Performance oj the Boiler. — The pounds of water evapo-
rated per pound of coal plotted in terms of rate of evaporation is
shown for each of the several pressures in Fig. 8. The equations
representing the performance of the boiler and furnace as estab-
lished by these lines are:
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 13
E = 11.040 - .221 H, when pressure is 240
E = 11.310 - .221 H, when pressure is 220
E = 11.373 - .221 H, when pressure is 200
E — 11.469 - .221 H, when pressure is 160
E = 11.357 - .221 H, when pressure is 120
where E is the number of pounds of water evaporated from and at
212° per pound of coal, andflls the number of pounds of water evap-
orated from and at 212° per sq.ft. of heating-surface per hour. The
area of heating-surface employed is based upon the interior sur-
face of the fire-box and the exterior surface of the tubes. In de-
termining the position of the lines represented by these equations
certain conventions were adopted. These, and the reasons un-
derlying them, may be described as follows:
The only difference in the running conditions applying to the
tests of each series is that of pressure, and as the terms em-
ployed in plotting the several diagrams are the same, it is
evident that the differences in performance are only such as may
result from the difference in pressure. Since the quantities are in
terms of equivalent evaporation, the differences can not be great.
Accepting this view, it was first sought to determine the slope of
the lines for the several groups. This was done by plotting upon
a single sheet all the points, eight in number, available for the
series at 240 Ib. together with eight points selected as fairly rep-
resentative from each of the other series, making forty points
in all. The result is shown in Fig. 9. Points thus plotted were
divided into two groups, one representing the lower rates of com-
bustion, and the other representing the higher rates, the points
being so chosen that each group contained four points from each
of the several series. The ordinates and abscissae for points
of each group were then determined, and the several values thus
obtained averaged. The final results were then plotted, giving
the points shown by the circles inclosing a cross (Fig. 9).
The equation from the line drawn through these points is
^ = 11.305 - 0.221 H
The line thus found (Fig. 9) may fairly be assumed to represent
the slope of the mean line of any number of points which for pur-
poses of comparison may be selected from the larger group.
In determining, therefore, the location of the mean lines (Fig. 8),
the abscissae and ordinates of all points were averaged and
14 ILLINOIS ENGINEERING EXPERIMENT STATION
the results plotted. Through the derived point a line is drawn
having the slope already found; that is, the mean line of Fig. 9.
8. Effect of Changes in Steam- pressure upon the Evaporative Effi-
ciency of the Boiler. — The generation of steam at a pressure of 120
Ib. involves a temperature of the water which is 50° less than that
which must be dealt with in generating steam at a pressure of
240 Ib. , and in general it has been assumed that any increase in
boiler- pressure necessarily results in some loss of evaporative
efficiency. It has been known that for the small ranges of pres-
sure common in stationary practice this difference is not great,
but the facts have not been established with reference to locomo-
tive performance or for ranges as great as those covered by the
experiments under consideration in any service.
The performance of the boiler experimented upon under a
range of pressure varying from 240 to 120 Ib. may be seen by
comparing the mean curves already developed (Fig. 8). This
diagram shows that the lowest efficiency is obtained with the
highest pressure and that with one exception the lines represent-
ing performance under different pressures fall in order, inversely
with the pressure. The exception is to be found in the line repre-
senting performance at 120 Ib. pressure. This line falls low, a
condition which may be explained by the fact that the spark and
cinder losses for these tests are known to have been excess-
ive. The mean line located from 40 points, representing all pres-
sures (Fig. 9), will represent any of the lines of Fig. 8 with an
error not greater than 0.2 Ib.
The results clearly define four general facts, which may be
stated as follows:
(a). The evaporative efficiency of a locomotive boiler is but
slightly affected by changes in pressure.
(b). Changes in steam- pressure between the limits of 120 Ib.
and 240 Ib. will produce an effect upon the efficiency of the boiler
which will be less than 0.5 Ib. of water per pound of coal.
(c). The equation E — 11.305 — 0.221 5" represents the evapo-
rative efficiency of the boiler of locomotive Schenectady No. 2 when
fired with Youghiogheny coal for all pressures between the limits
of 120 Ib. and 240 Ib. with an average error for any pressure
which does not exceed 2.1 per cent.
9. Smoke-box Temperatures. — The results of the tests show
that in all cases the temperature of the smoke-box gases increases
as the rate of evaporation increases. Plotted diagrams showing
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 15
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FIG. 8 EVAPORATION PER POUND OF COAL, UNDER DIFFERENT
CONDITIONS OF PRESSURE
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FIG. 9 EVAPORATION PER POUND OF COAL UNDER ALL
CONDITIONS OF PRESSURE
16 ILLINOIS ENGINEERING EXPERIMENT STATION
the exact relationship indicate a marked similarity for all pres-
sures; all have the same slope and if superimposed they would
fall very closely together.
Thus, they show that when the rate of evaporation is 9 Ib.
per ft. of heating-surface per hour, the smoke-box temperature
for all pressures is between the limits of 700° and 730° F. There
are but four results for a pressure of 240 Ib. , in comparison with
eight or more for other pressures. If the results from the tests
at 240 Ib. pressure be omitted it will be found that those remain-
ing, which represent a range of pressure from 220 Ib. to 120 Ib.,
are nearly identical. This is best shown by the equations of the
curves in question, which are given in Table 1.
TABLE 1
SMOKE-BOX TEMPERATURES UNDER DIFFERENT PRESSURES
Boiler-pressure
pounds
220
200
160
120
Average
Equations
T= 496.3 + 25.665"
T= 491.0 -f 25.661?
T= 487.7 + 25.66 H
T= 478.9 + 25.66 H
= 488.5 + 25. 66 H
The average of the several equations represents the average
of any of the several groups of results obtained under different
pressures, with an error which in no case exceeds 10° F., or 2 per
cent.
Again, the equations show that the effect of increasing the
pressure from 120 Ib. to 220 Ib. is to increase the smoke-box tem-
perature 17°; that is, an increase of pressure of nearly 100 per
cent results in an increase of smoke- box temperature of approxi-
mately 3.5 per cent.
In the preceding statements is to be found an explanation of
the constancy in the evaporative efficiency of the boiler under
different steam- pressures. The fact seems to be that the water in
the boiler is about as effective in absorbing the heat of the gases
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 17
when its temperature is 400° (240 Ib. pressure) as when its temper-
ature is but 350° (120 Ib. pressure).
The data sustain the following conclusions:
(a). The smoke- box temperature falls between the limits of
590° F. and 850° F., the lower limit agreeing with a rate of evap-
oration of 4 Ib. per ft. of heating-surface per hour and the latter
with a rate of evaporation of 14 Ib. per ft. of heating-surface per
hour.
(b). The smoke-box temperature is so slightly affected by
changes in steam-pressure as to make negligible the influence of
such changes in pressure for all ordinary ranges.
(c). The equation T = 488.5 + 25.66 H, where T is the tem-
perature of the smoke-box expressed in degrees F., and H is
pounds of water evaporated from and at 212° per. ft. of heating-
surface per hour, possesses a high degree of accuracy.
10. Draft. — The term "draft," as herein employed, represents
a reduction of pressure as compared with that of the atmosphere
expressed in inches of water. The draft was observed at three
different points between the ash-pan and the stack. These were
the smoke-box in front of the diaphragm, the smoke-box back of
the diaphragm, and the fire-box. At each of these points con-
nection was made with a U-tube containing water. The results
for each different steam-pressure vary but little so that those rep-
resenting the draft as affected by rate of evaporation for any
one pressure, for example, 160 (Fig. 10), are fairly representative
of the entire exhibit. Referring to Fig. 10, the solid points rep-
resent the draft in the smoke-box in front of the diaphragm;
the crosses, the draft behind the diaphragm; and the circles, the
draft in the fire-box. Expressing the results in other terms, it
appears that vertical distances between the highest curve and
the intermediate represent the resistance of the diaphragm; verti-
cal distances between the intermediate and the lowest curve, the
resistance of the tubes; and vertical distances between the lowest
curve and the axis, the resistance of the ash pan, the grate, and
the fire upon it. Values under this curve are a close approach to
the effective draft. In general, draft values vary greatly with
the conditions at the grate. A thin, clean fire results in compar-
atively low draft values throughout the system, while a thick
fire, or one which is choked by clinkers, leads to the reverse re-
18
ILLINOIS ENGINEERING EXPERIMENT STATION
suits. It is for this reason that individual points representing
draft sometimes vary widely from the mean of all results.
When the rate of evaporation is 10 Ib. per ft. of heating-sur-
face per hour, the draft in front of the diaphragm is approximate-
ly 4 inches for all pressures.
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12 13 14
11. Composition of Smoke-box Gases. — As previous experiments
had shown irregularities in the evaporative efficiency of boilers of
locomotives, it was early decided to proceed with care in deter-
mining the composition of the smoke-box gases. It seemed prob-
able that if the composition of these were known for each test,
variations in the evaporative efficiency of the boiler might be ex-
plained. To this end, therefore, each step in the process was
carefully considered, and the work of sampling and analyzing the
gases was assigned to a chemist of experience who had no other
duties to perform.
The gases were drawn from the smoke-box over mercury, a
period of from a half hour to an hour and a half being employed
in securing the sample. The sampling-tube was of copper and
of small diameter. Its length was sufficient to extend to the
center of the smoke-box, and gas was admitted to it by small per-
forations at the extreme end only. This tube could be drawn in
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 19
and out through a stuffing-box to permit the sample to be taken
either from the center of the smoke- box or from any location be-
tween that point and the shell. In securing the sample it was the
practice to move the tube systematically at regular intervals of
time. By these means it was assumed that abnormal results
due to fluctuations in the condition of the fire would be entirely
avoided.
The results, notwithstanding all precautions, have not proved
entirely satisfactory; that is, where the evaporative performance
is abnormal, they do not permit the assignment of a definite
cause. The defects are doubtless due to faulty sampling, though
it is not clear in what manner the sampling may be improved in
connection with locomotive work. They do, however, entirely
justify certain general conclusions. They show that the amount
of excess air admitted to the furnace is never great, and in most
cases it is very small — far below the limits which are thought de-
sirable in stationary practice. They show, also, that the excess
air diminishes as the rate of combustion increases. It is appar-
ent, therefore, that the loss inefficiency arising from excess air is
under normal conditions smaller than in most other classes of ser-
vice. Moreover, while the supply of air appears limited, it is
significant that the losses from imperfect combustion, as shown
by the presence of CO, are also small, the actual amount varying
irregularly between limits which are very narrow.
12. The quality of steam was uniformly high under all
conditions for pressure, the average for all tests being 99.08. The
quality declined slightly with increase of pressure, but in no case
did the moisture exceed 1.35 per cent.
IV. ENGINE PERFORMANCE
13. Mean Effective Pressure. — A review of the calculated
results shows that the possible range of cut-off under a ful-
ly-open throttle is reduced by a definite amount with each incre-
ment of pressure. For example, under 120 Ib. pressure, it is
possible to operate at 30 miles per hour with the reverse lever in
the fourteenth notch from the center, while at 240 Ib. the longest
cut-off under similar conditions of speed is represented by the
20 ILLINOIS ENGINEERING EXPERIMENT STATION
fourth notch of the reverse lever. It is of interest to note, also,
that within the range of the experiments each change in the posi-
tion of the reverse lever results in a change in power which is
nearly proportional to the extent of the movement of the reverse
lever.
14. The Indicated Horse-power. — The range in the values of the
indicated horse- power for all pressures falls between the limits of
134 and 610 horse- power. It appears from the results that with
the coal used during the tests the normal power of the locomotive
tested, when run at speed, is between 450 and 500 horse- power.
The development of more than 500 horse- power was always at-
tended by unusual efforts on the part of the fireman.
The power of the engine, under a pressure of 240 lb., was readily
developed with the reverse lever in the second and fourth
notches, while under 120 lb. pressure either a high speed or a
much longer cut-off must be employed before this condition is
reached. All this, of course, grows out of the fact that in experi-
ments involving a wide range of pressure the cylinder volume re-
mained constant. It is significant that the only two tests giving
a horse-power in excess of 600 lb. were run at 180 lb. and 200 lb. , re-
spectively. It will hereafter be shown that the operation of the
engine under these pressures was more efficient than under con-
ditions of pressure which were either lower or higher. Remem-
bering that the results disclose the entire range for which it was
practicable to operate the engine under a fully-open throttle, it
will be accepted as a noteworthy fact that the higher pressures
do not serve to increase the output of power.
15. Steam per Indicated Horse-power per Hour. — The high ef-
ficiency which is implied by results showing the steam consump-
tion per indicated horse-power per hour, and the narrow range
which they represent, taken in connection with the comprehen-
sive character of the running conditions involved, are matters of
more than ordinary importance. For example, at a pressure of
240 lb. , the engine experimented upon, when working under a
fully-open throttle, gave a horse-power hour in return for the
consumption of less than 24 lb. of steam, and under any condition
of speed or cut-off for which it was found possible to operate the
engine under a wide-open throttle, the consumption never exceed-
ed 26.3 lb. At lower pressures, involving the possibility of a
wider choice in the conditions of operating, the range is somewhat
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 21
increased. Thus, at 120 Ib. pressure the minimum value is 27.5
and the maximum 33.8, a range which, while greater than that just
referred to, is nevertheless extremely narrow as compared with the
range incident to the operation of other classes of engines .
The most efficient point of cut-off for the lowest pressure is
that secured when the reverse lever is in the eighth notch, which
is equal to 35 per cent of the stroke. At 200 Ib. pressure the
most efficient cut-off is that represented by the sixth notch, or 27
per cent of the stroke, and the data do not disclose that a short-
er cut-off than this under a fully -open throttle is profitable for the
engine experimented upon, even though the pressures be raised
to 240 Ib. In all cases the best results are obtained at a speed
either of 20 or 40 miles an hour; for all pressures above 160 Ib.,
the most efficient speed is 40 miles. The law of the change of
efficiency with changes in speed has been discussed and the rea-
sons underlying pointed out elsewhere.1
The least steam consumption for each speed under the sever-
al different pressures employed is set forth in Fig. 11. The val-
ues of the figure are of interest. They do not, however, consti-
tute a satisfactory base upon which to form comparisons.
40
30
20
AVERAGE
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27
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160
200
ZZO
240
FIG. 11
LEAST STEAM FOB EACH OF THE SEVERAL SPEEDS AT
DIFFERENT PRESSURES
16. Steam Consumption under Different Pressures. — The shad-
ed zone upon Pig. 12 represents the range of performance as it
appears from all tests run under the several pressures employed.
i Locomotive Performance, published by John Wiley & Sons.
22 ILLINOIS ENGINEERING EXPERIMENT STATION
For purposes of comparison, it is' desirable to define the effect of
pressure on performance by a line, and to this end an attempt
has been made to reduce the zone of performance to a represent-
ative line. In preparing to draw such a line, the average per-
formance of all tests at each of the different pressures was ob-
tained and plotted, the results being shown by the circles in Fig.
12. Points thus obtained can be regarded as fairly representing
the performance of the engine under the several pressures only
so far as the tests run for each different pressure may be assumed
to fairly represent the range of speed and cut-off under which
the engine would ordinarily operate. The best result for each
different pressure, as obtained by averaging the best results for
each speed at constant pressure, is given upon the diagram in
the form of a light cross. These points may be regarded as fur-
nishing a satisfactory basis of comparison in so far as it may be
assumed that when the speed has been determined, an engine in
service will always operate under conditions of highest efficiency.
Again, the left-hand edge of the shaded zone represents a com-
parison based on maximum performance at whatever speed or
cut-off. In addition to the points already described, there is lo-
cated upon the diagram (Fig. 12) a curve showing the perform-
ance of a perfect engine,1 with which the plotted points derived
from the data of tests may be compared. Guided by this curve
representing the performance of a perfect engine, a line, AB, has
been drawn proportional thereto, and so placed as to fairly rep-
resent the circular points derived from the experiments. It is
proposed to accept this line as representing the steam consump-
tion of the experimental engine under the several pressures em-
ployed. It is to be noted that it is not the minimum performance
nor the maximum, but it is a close approach to that performance
which is suggested by an average of all results derived from all
tests which were run. Since its form is based upon a curve of
perfect performance, it has a logical basis, and since it does no
violence to the experimental data, its use seems justifiable.
17. Performance under Different Pressures, A Logical Basis for
Comparison. — The record of boiler performance as set forth in
1 This curve represents the performance of an engine working on Carnot's cycle, the ini-
tial temperature being that of steam at the several pressures stated, and the final tempera-
ture being that of steam at 1.31b. above atmospheric pressure. This latter value is the as-
sumed pressure of exhaust in locomotive service.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 23
10 15 ZO 25 30 35 4-0,45.50 55
FIG. 12 STEAM CONSUMPTION UNDER DIFFERENT PRESSURES
Chapter III, is that actually obtained from the several tests run.
It has already been shown that this performance is affected by
variations in the evaporative efficiency of the boiler, due doubt-
less to irregularities in firing, but which are in fact unaccounted
for. One of the purposes of the discussion which occupies
the preceding chapter has been to reduce the values actually
resulting from the tests to a summarized statement which
may be accepted as a general definition of performance, assum-
ing all irregularities to have been eliminated. Such a summarized
statement is that which is shown by Fig. 9. It is also expressed
by the equation
^-=11.305-0.221 H
It is now proposed to determine the coal consumption per indi-
cated horse- power, assuming the boiler efficiency to have been in
all cases that which is expressed by this equation.
It appears, also, from the data that the steam consumed by
the cylinders varies for each different pressure with changes in
speed and cut-off, and it has been sought in the preceding para-
24 ILLINOIS ENGINEERING EXPERIMENT STATION
graphs to summarize the facts derived from the experiments into
a single expression. This appears in the form of the curve AB,
Fig. 12, which is to be accepted as representing the performance
of the cylinders under different pressures without reference to
speed or cut-off. Combining this general statement expressing
cylinder performance with that already obtained covering boiler
performance, it should be possible to secure an accurate measure
of the coal consumption per indicated horse- power hour, for each
different pressure which will represent the results of all tests at
that pressure.
The steps in this process are set forth by Table 2, in which —
Column 1 gives the several pressures embraced by the ex-
periments.
Column 2 gives the steam consumption per indicated horse-
power hour for each of these several pressures as taken from
the curve AB, Fig. 12.
Column 3 gives the number of thermal units in each Ib. of
steam at the several pressures assuming the feed-water in all
cases to have had a temperature of 60° F. The values of this col-
umn show at a glance the rate of change in the amount of heat
required to supply steam at the different pressures embraced by
the experiments.
Column 4 gives the pounds of water from and at 212° F. per in-
dicated horse-power hour. It equals Column 2 X Column 3-^965.8.
Column 5 gives the pounds of water evaporated from and at
212° F. per pound of coal and is calculated as follows: Assuming
that a fair average load for the locomotive tests is 440 horse-power,
and that this unit of power is delivered under all pressures, the cor-
responding rate of evaporation may be found by multiplying this
value by those of Column 4 and dividing by the area of heating-
surface; that is, the rate of evaporation = 440 X Column 4 -j- 1322.
The equivalent pounds of water per pound of coal is found by sub-
stituting the rates of evaporation found for H in the equation,
.0=11.305-0.221 H.
Column 6 gives the pounds of coal per indicated horse-power
per hour and equals Column 4 -r- Column 5.
Column 7 gives the pounds of coal saved per horse-power
hour for each 20-lb. increment in steam-pressure.
Column 8 gives the percentage saving in coal for each 20-
lb. increment in steam-pressure.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 25
TABLE 2
ENGINE PERFORMANCE TJNDER DIFFERENT PRESSURES
i Steam per
i Indicated
B.t.u. Given
Equivalent
Pounds of
Equivalent Pounds of
Coal Saving for
r» •!*»,. Horse-
OOlier nnwpr -nfr
Pressure P°wer Per
to 1 Pound Water per
Steam Feed- Indicated
Pounds of Coal per In-
Water per ; dicated
Each Increment
Hour.
water Horse-
Pound of ' Horse-
i Values from
Temp.=60. ° power
Dry Coal power Hour
Lb.
Per cent
i Curve
1 Hour
!
1
2
3
4
5 6
7
8
240
24.7
1176.6
30.09
9.10
3.31
.06
1.8
220
25.1
1174.4
30.52
9.06
3.37
.06
1.8
200
25.5
1172.0
30.94
9.03
3.43
.07
2.0
180
26.0
1169.5
31.48
8.99
3.50
.09
2.5
160
26.6
1166.8
32.14
8.94
3.59
.18
4.8
140
27.7
1163.8
33.38
8.85
3.77
.23
5.8
120
29.1
1160.5
34.97
8.73
4.00
. . .
The values of Table 2, especially those of Columns 2 and 6,
are of more than ordinary significance. They represent logical
conclusions based upon the results of all tests. Comparisons be-
tween them will show the extent to which the performance of a
locomotive will be modified by changes in the steam-pressure
under which it is operated. They show in the matter of steam
consumption (Column 2) that-
Increasing pressure from 160 to 180 Ib. reduces the steam
consumption 0.6 Ib. or 2.3 per cent.
Increasing pressure from 180 to 200 Ib. reduces the steam con-
sumption 0.5 Ib. or 1.9 percent.
Increasing pressure from 200 to 220 Ib. reduces the steam con-
sumption 0.4 Ib. or 1.6 per cent.
Increasing pressure from 220 to 240 Ib. reduces the steam con-
sumption 0.4 Ib. or 1.6 per cent.
In the matter of coal consumption (Column 6) they show that —
Increasing pressure from 160 to 180 Ib. reduces the coal con-
sumption 0.9 Ib. or 2.5 per cent.
Increasing pressure from 180 to 200 Ib. reduces the coal con-
sumption 0.7 Ib. or 2.0 per cent.
Increasing pressure from 200 to 220 Ib. reduces the coal con-
sumption 0.6 Ib. or 1.8 percent.
Increasing pressure from 220 to 240 Ib. reduces the coal con-
sumption 0.6 Ib. or 1.8 per cent.
26 ILLINOIS ENGINEERING EXPERIMENT STATION
These values are from actual tests. Those who are inclined
to insist upon basing their conclusions upon observed data will per-
haps find in them a satisfactory conclusion of the whole investi-
gation. The results show how slight is the gain to be derived
from any increment of pressure when the basis of the increments
is above 160 Ib. But they do not in fact tell the whole story. In
order to secure such results from a single locomotive it was
necessary to employ a machine designed for the highest pressure
experimented upon. Obviously, for the tests at lower pressure,
the locomotive was needlessly heavy for its dimensions. If, for
the tests under each of the lower pressures, the excess weight
could have been utilized in providing a boiler of greater heating-
surface, the difference in performance with each increment of
pressure would have been less than that to which attention has
already been called. It is for this reason that the results already
quoted, while significant and concise in their meaning, are never-
theless to be accepted as insufficient when regarded as a relative
measure of the value of different steam- pressures. An extension
of the discussion leading to a more general view of the matter
will be found set forth in Chapters VI to VIII.
V. MACHINE FRICTION AND PERFORMANCE AT DRAW-BAR
18. The Cylinders vs. the Draw-Bar as a Base from Which to
Estimate Performance. — In the latter paragraphs of the preceding
chapter results are given disclosing the performance of boiler
and engine as based upon cylinder performance. This is a cor-
rect basis from which to proceed in discussing the relative advan-
tage of different steam- pressures; for the process of the cylinders
represents the last of the thermodynamic changes by which the
heat of the fuel is transformed into work. The cylinders are in
fact one step nearer the problem in question than the draw- bar,
which for many purposes is properly regarded as a better basis
from which to determine the performance of a locomotive. This
being the case, the purpose of the present chapter will be entirely
served if attention is called to a few of the more significant facts
which center in the output of power at the draw- bar, leaving the
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 27
general discussion as to the relative values of different steam-
pressures to be continued in the chapters which follow.
19. Machine Friction. — This is the difference between work
done in the engine cylinders and that which appears at the draw-
bar. It is difficult to summarize the facts concerning engine fric-
tion. This is not due to defects in the experimental process under-
lying the data, but to the fact that the frictional resistance of the
machinery of the locomotive varies greatly from day to day.1
Evidence of this is accessible even to the casual observer. Dur-
ing any given test it is likely that an axle-box or a crank- pin may
run warm, while during another test under identical conditions oi
power the same part will remain perfectly cool. For this reason
many variations in the frictional resistance of the machine occur.
It is a fact, however, that the friction varies but slightly with in-
crease in steam- pressure, and that changes in cut-off are most
effective in modifying engine friction. Acting upon this sugges-
tion, all results have been plotted in terms of cut-off. The results
do not, of course, fall in line, but they take such positions as readily
to suggest the form of a curve which in an approximate way may
be employed to represent them. From such a curve the values
set forth in Fig. 13 have been derived. It is proposed to accept
50
40
30
EX/' I
=*SE LrVEFl I SOTSH I T^OI-l CET^T'ER
E 4 6 dt IO 12 14
FIG. 13 CORRECTED FRICTION, MEAN EFFECTIVE PRESSURE
APPLICABLE TO ALL PRESSURES
these values as an approximate measure of the frictional loss for
locomotive Schenectady No. 2 under all pressures. They are prob-
ably a little low for pressures above 200 Ib. and are perhaps
1 A general discussion of this question with data will be found in Locomotive Performance.
28 ILLINOIS ENGINEERING EXPERIMENT STATION
somewhat high for pressures below this limit. It can not be as-
sumed that they apply to any other locomotive than that which
was involved by the experiments. The machine friction as ex-
pressed in pounds pull at the draw-bar may be found for any test
by multiplying the mean effective pressure for that test by the con-
stant 88.75.
20. Steam per Dynamometer Horse-power per Hour. — Values
covering this factor express the combined efficiency of the cylin-
ders and machinery of the locomotive. They disclose the fact
that there are few conditions of running for which the locomotive
requires more than 30 Ib. of steam per dynamometer horse- power
hour, and the consumption may fall below 27 Ib. While differ-
ences in performance for all pressures above 200 Ib. are not great,
the steam consumption is much greater when the pressure is as
low as 120 Ib. The data show, also, that for best results the cut-
off must be lengthened as the pressure is decreased. The facts
as disclosed by the data are as follows:
For 240 Ib. pressure the best cut-off is approximately the
second notch, 14 per cent.
For 220 Ib. pressure the best cut-off is approximately the
fourth notch, 19 per cent.
For 180 Ib. pressure the best cut-off is approximately the
eighth notch, 33 per cent.
For 120 Ib. pressure the best cut-off is approximately the
twelfth or fourteenth notch, 47 per cent or 56 per cent.
21. Coal per Dynamometer Horse-power per Hour. — This factor
represents the combined performance of the boiler, the cylinders,
and the machinery of a locomotive. It connects the energy de-
veloped in the boiler by the combustion of fuel with that which is
developed at the draw- bar. In all cases where data are given,
the fuel consumed was of the same quality; hence all results are
comparable. Under a pressure of 240 Ib. the range is between
3.35 and 5. 01, while at a pressure of 160 Ib. the range is between
3.79 and 4.78, results which are of interest from at least two points
of view: first, because of the small difference in performances
resulting from a relatively large change in pressure; and second,
because of the significance of the values quoted when accepted as
a measure of the locomotive performance. It is doubtful if any
other type of steam-engine exhausting into the atmosphere can
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 29
be depended upon to deliver power from the periphery of its wheel
in return for the expenditure of so small an amount of fuel.
22. Corrected Results. — The values representing coal and
steam consumption which have thus far been referred to as per-
formance at the draw-bar are those actually observed. A close
comparison of these sometimes fails to give consistent results be-
cause of irregularities in boiler performance or in the frictional
resistance of the machinery growing out of causes already dis-
cussed.
In Table 3 values are presented from which all such discrep-
ancies have been eliminated. They are those which would have
been obtained if the evaporative efficiency for all tests had been
that indicated by the equation:
E = 11.305 — 0.221 H
and if the machine friction for all cases had been that shown by
Fig. 13. Column 13 giving the corrected coal per dynamometer
horse- power, and Column 14 the corrected steam per dynamometer
horse-power, may be accepted as representing the best informa-
tion derived from the entire research.
30
ILLINOIS ENGINEERING EXPERIMENT STATION
TABLE 3
COMPARATIVE PERFORMANCE OF THE LOCOMOTIVE. ASSUMING IRREGU-
LARITIES IN THE RESULTS OF INDIVIDUAL TESTS TO HAVE BEEN
ELIMINATED
o
Designa-
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9.835
895
3.24
31.84
6.5
30.8
11.1
245.6
4600
3.64
35.86
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20-4-240
12008
9.298
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8.5
40.2
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20-6-240
13614
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11444
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30-4-240
13888
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8
40-2-240
12320
9.245
1333
3.16
29.20
6.5
61.5
14.6
360.3
3379
3.69
34.19
9
40-4-240
16320
8.576
1903
3.36
28.82
8.5
80.5
14.2
485.8
4550
3.91
33.59
11
50-2-240
14066
8.953
1571
3.37
30.21
6.5
76.9
16.5
388.6
2910
4.04
36.19
13
20-2-220
8533
9.878
864 3.38
33.42
6.5
30.8
12.0
224.5
4210
3.84
38.01
14
20-4-220
10681
9.519
1122
3.27
31.15
8.5
40.2
11.7
302.6
5670
3.71
35.29
15
20-6-220
13294
9.082
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3.39
30.81
9.3
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387.4
7260
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16
20-8-220
16653
8.521
1954
3.66
31.24
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17
30-2-220
10286
9.585
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6.5
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3430
3.91
37.51
18
30-4-220
12976
9.136
1420
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386.1
4820
3.68
33.60
19
30-6-220
15915
8.644
1841
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28.44
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66.0
11.8
493.5
6170
3.73
32.25
21
40-2-220
11471
9.387
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3.29
30.87
6.5
61.5
16.5
310.0
2910
3.94
37.00
22
40-4-220
14549
8.873
1638
3.21
28.57
8.5
80.5
15.8
428.6
4020
3.82
33.94
24
50-2-220
12017
9.296
1292
3.41
31.72
6.5
76.9
20.3
301.9
2260
4.28
39.80
25
50-4-220
16343
8.573
1906
3.39
29.08
8.5
100.6
17.9
461.7
3460
4.13
35.40
29
20-2-200
7632
10.029
761
3.40
34.14
6.5
30.8
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3610
3.94
39.61
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20-4-200
9100
9.784-
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3.23
31.64
8.5
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247.4
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3.75
36.78
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20-6-200
11774
9.337
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3.35
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331.8
6220
3.80
35.48
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20-8-200
15011
8.795
1707
3.60
31.74
8.4
39.8
8.4
433.18120
3.94
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9.839
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3.31
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30-4-200
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9.406
1207
3.29
30.92
8.5
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3830
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8.850
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9.599
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50-4-200
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20-2-180
6638
10.195
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4.04
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47
20-4-180
8475
9.888
858
3.25
32.15
8.5
40.2
15.3
223.4
4190
3.84
37.94
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 31
TABLE 3 (Continued)
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i i
32 ILLINOIS ENGINEERING EXPERIMENT STATION
VI. BOILER PRESSURE As A FACTOR IN ECONOMICAL
OPERATION
23. The amount of steam consumed by the locomotive per
unit power developed, when operated under various pressures be-
tween the limits of 120 Ib. and 240 Ib. , has already been denned
(Pig. 12). Basing conclusions on results thus disclosed, it is now
proposed to determine the increase in efficiency which may be se-
cured through the adoption of higher pressure for any given in-
crease in the weight of the boiler and its related parts. That this
may be done, it is essential to determine the relation between boilers
of a given size when designed for different pressures.
24. Weight of Locomotive as Affected by Steam- Pressure. — The
parts of a locomotive which are affected by changes in steam -pres-
sure, assuming the power to remain constant, are the boiler and
certain portions of the engine. The boiler to be adapted to a
higher steam-pressure requires thicker plates, heavier riveting,
and stronger staying, all tending to augment its weight. The
effect of the change upon the engine, however, is to make it lighter,
for since with increased pressure, cylinders, pistons, and valves
become smaller, their weight will generally diminish. As a basis
for exact values, denning their relationship, lines were laid down
for a boiler of the following dimensions:1
Diameter of first ring inches 63
Number of 2-inch tubes 258
Length of tubes feet 14
Total heating-surface square feet 2024
Length of grate inches 90
Width of grate inches 60
Area of grate feet 37 . 5
Boiler-pressure pounds 190
•
Pour designs were made, adapted to four different pressures,
respectively, from which designs weights were calculated, with
results shown by Table 4.
The weight of the cylinders, valves, and pistons which would
be used with a boiler having 2024 sq. ft. of heating- surf ace in mak-
ing up a representative locomotive carrying the different pres-
sures designated is set forth in Column 3. The weight of water
when the boiler is filled to the second gage appears as Column 4.
The weight of steam is negligible. The total weight of all parts
1 These and other determinations involve weights of boilers which were supplied by the
courtesy of the American Locomotive Company.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 33
TABLE 4
WEIGHT OF THOSE PARTS OF A LOCOMOTIVE WHICH ARE AFFECTED BY
CHANGES IN BOILER PRESSURE
Boiler Pres-
sure
Weight of Boiler
pounds
Weight of Cylin-
ders, Valves, and
Pistons
pounds
Weight of Water
pounds
Weight of All
Parts Affected by
Changes in Pres-
sure
pounds
1
2
3
4
5
160
190
220
250
30679
32913
36076
38953
12580
' 12240
11990
11620
16349
16536
16661
16848
59608
61689
64727
67421
of the locomotive directly affected by the changes in pressure is
given in Column 5, and the values of this column, for the pur-
pose of interpolation, have been plotted in terms of steam-pressure,
with results as set forth by Fig. 14.
With these data it is proposed to show the extent to which
the performance of a typical locomotive using saturated steam
may be improved by increasing the pressure carried within its
boiler. For convenience, six different pressures having values
between 120 Ib. and 220 Ib. will be utilized as bases from which to
aso
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50,000 60,000 70,000
FIG. 14 WEIGHT OF BOILER As AFFECTED BY
CHANGES IN PRESSURE
34 ILLINOIS ENGINEERING EXPERIMENT STATION
assume an increase of pressure. The increase of pressure from
each base will be such as may be possible upon the allowance of
definite increments in the weight of those portions of the locomo-
tive affected by pressure, and in like manner the improvement in
performance will be expressed as a per cent of that which is nor-
mal to the base. The results of the process outlined are present-
ed in Table 5. An explanation of the columns of this table whose
meaning is not self-evident follows:
Column 3. Weight of those parts of a typical locomotive affected by
changes in steam-pressure, including water in boiler. — The values of
this column, for each of the several pressures stated in Column 2,
are taken directly from the diagram of Fig. 14, the basis of which
has already been explained.
Column 5. New boiler-pressure obtainable by utilizing the in-
crease of weight in making a stronger boiler. — The values in this
column for each of the several weights stated in Column 4 were
taken from the diagram in Fig. 14.
Column 6. Steam per indicated horse-power per hour at the
pressures given in Column 2. — Values for this column are taken di-
rectly from the curve of Fig. 12.
Column 7. Steam per indicated horse-power per hour at the new
pressures given in Column 5. — These values, also, were taken di-
rectly from the diagram (Fig. 12).
Column 8. Direct saving in steam consumption, resulting from
an increased weight equal to the per cent shown in Column 1. — Values
of this column are equal to 100 times those of Column 6 minus
those of Column 7 divided by those of Column 6.
Column 9. Indirect saving due to reduced rates of evaporation,
percent. — Assuming the locomotive to work at the same power at
whatever pressure it may carry, the saving in steam resulting
from the increased pressure set forth in Column 8 diminishes the
demand upon the boiler, and, as the efficiency of the boiler in-
creases as the rate of evaporation is reduced, there results an in-
direct saving with each increase of pressure. The relation be-
tween the evaporative efficiency of the boiler and rate of evapora-
tion has already been defined (Fig. 9). Assuming the normal rate
of evaporation for the boiler under initial conditions to be 10, then
a reduction of 1 per cent in the rate of evaporation will effect an
increase in the evaporative efficiency of 0. 243 per cent. The values
in Column 9, therefore, are those of Column 8 multiplied by the
constant 0.243.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 35
TABLE 5
TOTAL SAVING WHEN A POSSIBLE INCREASE OF WEIGHT Is UTILIZED As
A MEANS OF INCREASING BOILER-PRESSURE
I
Hi
is
III
II
}-power
ssures 1
M
III
Deduced
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Utilizing t
sight in Ma
oiler, pounds
am per Indie
r Hour at the
Column 2, poi
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a«a<3
X 3 G
O-O-"
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Column 1. per
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0
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1
2
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4
5
6
7
8
9
10
r
120
55560
58340
150
29.1
27.1
6.87
1.67
8.54
140
57390
60260
171
27.7
26.3
5.05
1.23
6.28
B
160
59220
62180
192
26.6
25.7
3.39
.82
4.21
5 1
180
61050
64100
213
26.0
25.2
3.08
.75
3.83
200
62880
66020
234
25.5
24.8
2.75
.67
3.42
I
220
64710
67940
255
25.1
24.5
2.39
.58
2.97
120
55560
61120
181
29.1
26.0
10.65
2.59
13.24
T /\
140
57390
63130
203
27.7
25.4
8.31
2.02
10.33
10
160
59220
65140
225
26.6
25.0
6.02
1.46
7.48
I
180
61050
67150
247
26.0
24.6
5.38
1.31
6.69
120
55560
63890
211
29.1
25.3
13.06
3.17
16.23
15 {
140
57390
66000
234
27.7
24.8
10.46
2.51
13.00
1
160
59220
68100
257
26.6
24.5
7.90
1.92
9.82
20
120
55560
66670
241
29.1
24.7
15.12
3.67
18.79
Column 10. Total saving. — The total saving is the sum of
Columns 8 and 9.
The significance of this table may best be appreciated by the
following examples:
By line 1 of the table it appears that the base is 120 Ib.
(Column 2). The parts of the typical locomotive designed for this
pressure, which are affected by changes in steam-pressure, weigh
55,560 Ib. (Column 3). If, now, in designing a new lot of locomo-
tives, it becomes possible to increase this weight by 5 per cent
(Column 1), the weight of these parts for the new locomotive may
be 58,340 Ib. (Column 4). This weight, if put into a boiler of the
same capacity, will allow the pressure to be increased from 120
Ib. (Column 2) to 150 Ib. (Column 5), and as a result its steam con-
36 ILLINOIS ENGINEERING EXPERIMENT STATION
sumption per horse-power hour will fall from 29.1 Ib. (Column 6)
to 27.1 Ib. (Column 7), or 6.87 per cent (Column 8). But the sav-
ing of 6.87 per cent in steam consumption diminishes the demand
which is made upon the boiler for steam, and at the lower rate of
evaporation the boiler becomes 1.67 per cent (Column 9) more
efficient, giving a total gain as a result of the change in pressure
of 8.58 per cent (Column 10). In a similar manner each line of
the table presents a measure of the improvement to be expected
from some definite increase of pressure.
A study of the analysis which has preceded will show that the
values of Column 10 may be accepted as fairly representing the
increase in efficiency which may be secured in return for a given
increase in steam- pressure, or, as is more clearly shown by Table
4, in return for a given increase in the weight of those parts of
the locomotive affected by increase of pressure.
While the comparison is based on improved efficiency, it will,
of course, be understood that, at the limit, the saving shown may
be converted into a corresponding increase of power. It would
have been possible by assuming constant efficiency to have shown
the improvement in terms of increase of power.
VII. BOILER CAPACITY AS A FACTOR IN ECONOMICAL
OPERATIONS
25. In the preceding chapter there is considered the advantage
to be derived through the utilization of any possible increase
in the weight of a locomotive, as a means by which to secure
an increase of pressure. It is the purpose of this chapter to con-
sider the benefit which may be derived by utilizing similar incre-
ments in weight to secure an increase in boiler capacity, the pres-
sure remaining constant. The weights of boilers and related
parts involved by such a comparison have been ascertained from
considerations similar to those which controlled in the preceding
case. A boiler of the dimensions already given (paragraph 24),
designed for 190 Ib. , was made the starting-point from which
values were ascertained for boilers of different capacities de-
signed to carry 160 Ib. pressure. The characteristics of the sev-
eral boilers thus designed are set forth in Table 6.
GOSS— HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 37
TABLE 6
CHARACTERISTICS OF FOUR BOILERS DESIGNED FOR 160 POUNDS
PRESSURE AND DIFFERENT CAPACITIES
Weight of
Parts of
Diam-
eter of
Boiler
inches
Num-
ber of
2- inch
Tubes
Length
of
Tubes
feet
Length
of
Grate
inches
Width
of
Grate
inches
Area
of
Grate
sq. ft.
Area
of
Heating-
surface
Weight
of
Boiler
pounds
Weight
of Water
in Boiler
pounds
Locomotive
Which Are
Affected by
Changes in
Heating-
surface
pounds
1
2
3
4
5
6
7
8
9
10
63
258
14
90
60
37.4
2024
30,679
16,349
47,028
67
338
16
102
65
46.1
3013
41,013
20,092
61,105
69
326
14
102
65
46.1
2538
36,321
19,344
55,665
70
396
16
96
75
50.0
3498
42,894
21,965
64,859
The steam- pressure being constant, the dimensions and con-
sequently the weight of the cylinders and related parts for the
development of a given power remain unchanged. It is obvious,
also, that since the only change in the locomotive is in the
size of its boiler, the cylinder performance will be the same
for locomotives having boilers of different sizes. The saving which
will result from the employment of boilers of greater capacity will
be only that which results from the diminished rate of evaporation
per unit area of heating-surface. The relation of evaporative ef-
ficiency and rate of evaporation has already been defined (Pig. 9),
so that both factors in the problem now are known, namely, the in-
crease in weight necessary for a given increase in capacity and
the effect of any increase in capacity in improving the evapo-
rative efficiency. By means of relations thus established values
have been determined which are presented in Table 7. An ex-
planation of the columns of this table whose meaning is not self-
evident is as follows:
Column 3 is the weight of boiler, the contained water, and
the cylinders, pistons, and valves. While the cylinders, pistons,
and valves do not change for any given pressure, their weights
are included to make the values comparable with those employed
in the analysis of the preceding chapter. They are in fact iden-
tical with the values of Column 3, Table 5.
Column If.. Allowable increase in weight. — The values of this col-
umn are the percentages indicated by Column 1 of the values of
Column 3.
38 ILLINOIS ENGINEERING EXPERIMENT STATION
TABLE 7
SAVING WHEN A POSSIBLE INCREASE OP WEIGHT Is UTILIZED
As A MEANS OF INCREASING HEATING-SURFACE
Increase
of
Weight
per cent
Boiler-
pressures
Selected
as Bases
pounds
Weight of
Parts of a
Typical
Locomotive
(Boiler,
Cylinders,
Valves, Pis-
tons, and
Water)
Allowable
Increase of
Weight
pounds
Heating-
surface of
Typical
Locomo-
tives
Whose
Weights
Are Given
in
Column 3
Increase
of Heating-
surface Ob-
tainable by
Utilizing In-
crease of
Weight in
Making a
Larger
Boiler
Increase of
Heating-
Surface
per cent
Saving in
Evaporative
Perform-
ance
Due to
Reduced
Rate
per cent
pounds
sq. ft.
sq. ft.
1
2
3
4
5
6
7
8
120
55560
2778
2000
234.7
11.73
2.85
140
57390
2869
2000
242.5
12.12
2.95
160
59220
2961
2000
250.1
12.50
3.04
•
180
61050
3052
2000
257.7
12.88
3.13
200
62880
3144
2000
265.3
13.26
3.22
220
64710
3235
2000
272.9
13.64
3.31
f
120
55560
5556
2000
469.4
23.47
5.70
in J
140
57390
5739
2000
484.9
24.24
5.89
10
160
59220
5922
2000
500.4
25.02
6.08
I
180
61050
6105
2000
515.9
25.79
6.27
120
55560
8334
2000
704.2
35.21
8.55
15 {
140
57390
8608
2000
727.3
36.36
8.84
1
160
59220
8883
2000
750.6
37.53
9.12
20
120
55560
11112
2000
939.0
46.95
11.41
Column 6. Increase of heating -surf ace. — Values for this column
have been obtained by plotting weight of affected parts in terms of
heating-surface (Columns 7 and 10, Table 5). The results appear in
Fig. 15. From a representative line drawn through points thus
obtained showing the relation between the weight of the boiler
and water, and the number of square feet of heating-surface, it can
be shown that an increase of 10,000 Ib. in the weight of boiler and
affected parts permits an increase of 845 sq. ft. in heating- surf ace.
Therefore, in Table 6, Column 6 equals Column 4 multiplied by
0.0845. This relation was obtained from data of a boiler designed
for 160 Ib. pressure and is assumed to be approximately true for
boilers of other pressures.
Column 7. Increase of heating -surf ace, per cent, is Column 6
multiplied by 100 divided by Column 5. It also shows the per cent
reduction in the rate of evaporation.
Column 8. Saving in evaporative performance due to reduced
rate, per cent. — Values in this column have been obtained from
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 39
those of the preceding column by means of a relationship al-
ready established controlling evaporative efficiency of boiler and
rate of combustion (Pig. 9). This relation is such that a reduction
of 1 per cent in the rate of combustion increases the evaporative
efficiency 0.243 per cent. Values of Column 8 are, therefore,
those of Column 7 multiplied by this factor.
3,000
2,000
J;
r
x
Ill
/
u
XJ
ii
X
DC
X
D
y
^
(IJ
X
^
(1)
f
/
x
0
-
x
UJ
y
7
X
y
X
<
x
s
*
rE
GI
plT
c
F
A
FP
EI
rT
E
D
b
^R
Ti
> C
F
.0
cc
v*
^T
JV\
r -.
45,000
55,000
65,000
FIG. 15 WEIGHT OF BOILER As AFFECTED BY CHANGES
IN HEATING-SURFACE
The significance of Table 6 will be understood from the fol-
lowing illustration, based upon the first line of the table. As-
suming an existing locomotive operating under a pressure of 120
Ib. (Column 2) to have a boiler containing 2000 sq. ft. of heating-
surface (Column 5) weighing with the contained water 55,560 Ib.
(Column 3), an increase of 5 per cent (Column 1) or 2778 Ib.
(Column 4), will permit an extension in heating-surface of 234.7
sq. ft. (Column 6) which, compared with its original surface is an
increase of 11.73 per cent (Column 7). This increase in the ex-
tent of heating-surface, assuming the power developed to remain
unchanged, will result in an improvement in the performance of
the boiler of 2.86 per cent (Column 8). The facts underlying
the analysis are primarily the results of tests.
40 ILLINOIS ENGINEERING EXPERIMENT STATION
VIII. CONCLUSIONS CONCERNING BOILER-PRESSURE vs.
BOILER CAPACITY As A MEANS OP INCREASING THE EFFI-
CIENCY OF A SINGLE-EXPANSION LOCOMOTIVE
26. In the preceding chapters an analysis has been given
showing the saving which may result in locomotive service, first,
by increasing the pressure, the boiler capacity remaining un-
changed, and second, by increasing the heating-surface, the
pressure remaining unchanged. A summary of the conclusions
of these chapters is presented in Fig. 16 to 21 in which the full
line represents the gain through increase of boiler-pressure and
the dotted line the corresponding gain through increase of boiler
capacity. The values for these diagrams are taken directly from
Tables 5 and 7. It will be seen that starting with pressures
which are comparatively low, the most pronounced results are
those to be derived from increments of pressure. With each rise
in pressure, however, the chance for gain through further in-
crease diminishes. With a starting-point as high as 180 Ib. , the
saving through increased pressure is but slightly greater than
that which may result through increased boiler capacity.
The fact should be emphasized that the conclusions above de-
scribed are based upon data which lead back to the question of
coal consumption. The gains which are referred to are measured
in terms of coal which may be saved in the development of a
given amount of power. It will be remembered that conditions
which permit a saving in coal will, by the sacrifice of such sav-
ing, open the way for the development of greater power, but the
question as defined is one concerning economy in the use of fuel .
It is this question only with which the diagrams (Fig. 16 to 21)
deal.
There are other measures which may be applied to the per-
formance of a locomotive which, if employed in the present case,
would show some difference in the real values of the two curves (Fig.
16 to 21). The indefinite character of these measures prevents
their being directly applied as corrections to the results already
deduced, but their effect may be pointed out. Thus, the extent
to which an increase of pressure will improve performance has
been defined, but the definition assumes freedom from leakage.
If, therefore, leakage is allowed to exist, the result defined is not
secured. Moreover, an increase of pressure increases the chance
GOSS— HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 41
of loss through leakage, so that to secure the advantage which
has been defined, there must be some increase in the amount of
attention bestowed, and this, in whatever form it may appear,
means expense, the effect of which is to reduce the net gain which
it is possible to derive through increase of pressure. Again, in
parts of the country where the water-supply is bad, any increase
of pressure will involve increased expense in the more careful and
more extensive treatment of feed-water, or in the increased cost
of boiler repairs, or in detentions arising from failure of injector,
or from all of these sources combined. The effect of such expense
is to reduce the net gain which it is possible to derive through in-
crease of pressure. These statements call attention to the fact
that the gains which have been defined as resulting from increase
of pressure (Fig. 16 to 21) are to be regarded as the maximum
gross; as maximum because they are based upon results derived
from a locomotive which was at all times maintained in the highest
possible condition, and as gross because on the road, conditions
are likely to be introduced which will necessitate deductions there-
from.
The relation which has been established showing the gain to
be derived through increased boiler capacity is subject to but few
qualifying conditions . It rests upon the fact that for the devel-
opment of a given power a large boiler will work at a lower rate
of evaporation per unit area of heating-surface than a smaller one .
The saving which results from diminishing the rate of evaporation
is sure; whether the boiler is clean or foul, tight or leaky, or
whether the feed- water is good or bad, the reduced rate of evapora-
tion will bring its sure return in the form of increased efficiency .
An increase in the size of a boiler will involve some increase in
the cost of maintenance, but such increase is slight and of a sort
which has not been regarded in the discussion involving boilers
designed for higher pressures.
Keeping in mind the fact that as applied to conditions of ser-
vice the line A is likely to be less stable in its position than B, the
facts set forth by Fig. 16 to 21 may be briefly reviewed.
Basing comparisons upon an initial pressure of 120 lb., (Fig.
16), a 5 per cent increase in weight, when utilized in securing a
stronger boiler, will improve the efficiency 8.5 per cent, while if
utilized in securing a larger boiler, the improvement will be a
trifle less than 3 per cent. Arguing from this base, the advantage
42
ILLINOIS ENGINEERING EXPERIMENT STATION
16
12
?
^
J
/
h
y
L^
X
UJ
f
I
7
/
,e
S ':
I
x
/
s'
/
S
u
I
X
Z
/
x"
1
SI
rj
=^L
p
R
m %
s
JF
E
ffl
/
^
'
il
O
p
ot
N
D!
z
/
X
/
/
/
X
*
s
/
x
X
v
A
LI
0
Vf
Bl
E
If
c
^E
A5
E
OF
V
/E
G»
^f
ET
Cl
.n
T
S/' 10 15 ^20
FIG. 16
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making a stronger boiler to permit a higher pressure.
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
to be derived from an increase of pressure is great. If, however,
the increase in weight exceeds 10 per cent, the curve A ceases to
diverge from B and if both curves are sufficiently extended, they
will meet, all of which is proof of the fact that the rate of gain is
greatest for relatively small increments of weight.
Basing comparisons upon an initial pressure of 140 Ib. (Fig.
17), the relative advantage of increasing the pressure diminishes,
though on the basis of a 5 per cent increase in weight it is still
double that to be obtained by increasing the capacity.
Basing comparisons upon an initial pressure of 160 Ib. (Pig.
18), the advantage to be gained by increasing the pressure over
that which may be had by increasing the capacity is very small,
so small in fact that a slight droop in the curve of increased
pressure (A) would cause it to disappear. As the curve B may be
regarded as fixed, while A, through imperfect maintenance of
boiler or engine, may fall, the argument is not strong in favor of
increasing pressure beyond the limit of 160 Ib.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 43
16
12
8
-7
LU
/;
U
yX
S
H
^
x^
a
X
J
j
Y
B
1
>
f
X'
0
^
/*
x;
z
/
V
^x*
'
1
5r
ri/
^L
p
Ri
iS
SI
JR
fry
1
y1
s*
K
1-0
p
DL
N
D£
r
/
x
>
/
x
x
r.o
J
^
x"
/
X
/
/
x
//^
AJ
Lt
°1
rvA
Bl
.E
\r
«C
^E
^S
£
OF
V
/E
IQ
HT
^
EP
^C
Eh
JT
10
20,
15
FIG. 17
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making a stronger boiler to permit a higher pressure.
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
16
12
8
1
t 1
rj
9
8j
QJ
i
a
X
^'
o
x
p
B
z
x^
X
11
•si
TU
^L
P
PI
LS
SI
IR
E
17
^
x"
16
0
P(
OL
N!
DS
z
/
X
>
f
V
X
x
(^
/
X*
L
7!
x'
f'
/
f
LIO1
VP
B
.E
Ir
4C
^E
|A5
E
OF
V
/E
Gi
4T
i,!-
EP
ICI
:N
T
O 5 10 15 ZC
FIG. 18
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making a stronger boiler to permit a higher pressure.
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
44
ILLINOIS ENGINEERING EXPERIMENT STATION
Basing comparisons upon an initial pressure of 180 lb., (Fig.
19), the advantage under ideal conditions of increasing the pres-
sure, as compared with that resulting from increasing the capac-
ity, has a maximum value of approximately one-half of 1 per
cent. In view of the incidental losses upon the road the practi-
cal value of the advantage is nil. The curves A and B (Pig. 12),
16
5
ui
0
DC
UI
a
j
%
u
z
A
IT
41
rii
*L
F
R
;5
S^
IB
F
(3
^
Y
!€
Q
P
DL
N
DS
r
S
?
B
>
/
s
CO
/
s
/<
/,•
/
p
LL
0\
Vfl
p
Ir
tc
*E
^S
,E
OF
V
/E
Gt-
IT
TF
E'
^C
Er
,T
10
15
FIG. 19
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making a stronger boiler to permit a higher pressure-
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
constitute therefore no argument in favor of increasing pressure
beyond the limit of 180 lb.
Basing comparisons upon an initial pressure of 200 lb., (Fig.
20), it appears that under ideal conditions either the pressure or
the capacity may be increased with equal advantage, this being
in effect a strong argument in favor of increased capacity rather
than of higher pressure.
Basing comparisons upon a pressure of 220 lb., (Pig. 21), it
appears that even under ideal conditions of maintenance the gain
in efficiency resulting from an increase of pressure is less than
that resulting from an increase of capacity. In view of this fact,
no possible excuse can be found for increasing pressure above
the limit of 220 lb.
GOSS — HIGH STEAM-PRESSURES IN LOCOMOTIVE SERVICE 45
16
12
8
3
u
3
Q.
J
d
(J
ZT
Ir
•41
ru
\LJ
P
RJ
ES
5U
R
Itf
2C
0
F5
PI-
)r>f
DS
r
1
£>
rn
A J
K
[
/>x
B
A
V
LLoJ
/A
61
E
IH
<c
RE
AS
E
OP
•vi
VE
Gl
4T
>EF
:N
T
10
15
20
FIG. 20
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making: a stronger boiler to permit a higher pressure.
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
16
L10\
OF
V^fiie
IHITIIU- Pnsiium:
JioR>cN
4T
FEFICI
[NT
Cr 5 IO 15 2O
FIG. 21
The line A represents the saving in fuel when an allowable increase in weight is
utilized in making a stronger boiler to permit a higher pressure.
The line B represents the saving in fuel when an allowable increase in weight is
utilized in making a larger boiler to give increased capacity.
PUBLICATIONS or THE ENGINEERING EXPERIMENT STATION
Resistance of Tubes to Collapse, by Albert P. Carman. 1906. (Out of
Holding Power of Railroad Spikes, by Roy I.Webber. 1906. (Out of
Bulletin No. 1. Tests of Reinforced Concrete Beams, by Arthur N. Talbot. 1904. (Out
of print.)
Circular No. 1. High-Speed Tool Steels, by L. P. Breckenridge. 1905.
Bulletin No. 2. Tests of High-Speed Tool Steels on Cast Iron, by L. P. Breckenridge
and Henry B. Dirks. 1905.
Circular No. 2. Drainage of Earth Roads, by Ira O. Baker. 1906. (Out of print.)
Bulletin No. 3. The Engineering Experiment Station of the University of Illinois, by
L. P. Breckenridge. 1906. (Out of print.)
Bulletin No. 4. Tests of Reinforced Concrete Beams. Series of 1905, by Arthur N.
Talbot. 1906.
Bulletin No.
print.)
Bulletin No.
print.)
Bulletin No. 7. Fuel Tests with Illinois Coals, by L. P. Breckenridge, S. W. Parr and
Henry B. Dirks. 1906.
Bulletin No. 8. Tests of Concrete: I. Shear; II. Bond, by Arthur N. Talbot. 1906. ( Out
of print.)
Bulletin No. 9. An Extension of the Dewey Decimal System of Classification Applied
to the Engineering Industries, by L. P. Breckenridge and G. A. Goodenough. 1906.
Bulletin No. 10. Tests of Concrete and Reinforced Concrete Columns, Series of 1906, by
Arthur N. Talbot. 1907. (Out of print.)
Bulletin No. 11. The Effect of Scale on the Transmission of Heat through Locomotive
Boiler Tubes, by Edward C. Schmidt and John M. Snodgrass. 1907. (Out of print.)
Bulletin No. 12. Tests of Reinforced Concrete T-beams, Series of 1906, by Arthur N.
Talbot. 1907. (Out of print.)
Bulletin No. 13. An Extension of the Dewey Decimal System of Classification Applied
to Architecture and Building, by N. Clifford Ricker. 1907.
Bulletin No. 14. Tests of Reinforced Concrete Beams, Series of 1906, by Arthur N.
Talbot. 1907. (Out of print.)
Bulletin No. 15. How to Burn Illinois Coal without Smoke, by L. P. Breckenridge . 1908.
Bulletin No. 16. A Study of Roof Trusses, by N. Clifford Ricker. 1908. (Out of print.)
Bulletin No. 17. The Weathering of Coal, by S. W. Parr, N. D. Hamilton, and W. F.
Wheeler. 1908.
Bulletin No. 18. The Strength of Chain Links, by G. A. Goodenough and L. E. Moore. 1908.
Bulletin No. 19. Comparative Tests of Carbon, Metallized Carbon and Tantalum Fila-
ment Lamps, by T. H. Amrine. 1908.
Bulletin No. 20. Tests of Concrete and Reinforced Concrete Columns, Series of 1907, by
Arthur N. Talbot. 1908.
Bulletin No. 21. Tests of a Liquid Air Plant, by C. S. Hudson and C. M. Garland. 1908.
Bulletin No. 22. Tests of Cast-Iron and Reinforced Concrete Culvert Pipe, by Arthur N.
Talbot. 1908.
Bulletin No. 23. Voids, Settlement and Weight of Crushed Stone, by Ira O. Baker. 1908.
Bulletin No. 24. The Modification of Illinois Coal by Low Temperature Distillation, by
S. W. Parr and C. K. Francis. 1908.
Bulletin No. 25. Lighting Country Homes by Private Electric Plants, by T. H.
Amrine. 1908.
Bulletin No. 26. High Steam-Pressures in Locomotive Service. A Review of a Report to
the Carnegie Institution of Washington. By W. F. M. Goss. 1908.
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