TEJ
'3
A(
~':
THESIS.
SEFVICE TEST OF THE STRAMSHIP HARVARD.
ECONOMY.
May 1909.
John 7A Davis.
Carleton W. Hubbard.
/
IIDEX.
Page.
Apparatus, Description of . . . . . . . . . . . . . . 10
Boilers, Description of . . . .
Calculation .
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.
.
.
.
.
.
.
.
Conclusion . . . . . . . . . .
Data
. . . . . .... . . .
Fireroom .. .. ....
.
Gauge Corrections .
.
.
..
. . ... . 6
.......
. . . ...
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. . ...
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. .
Steamer, Description of .
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10
. . . . . . . . . . . . .26-30
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..
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Testing, Method of . .
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Time Table . . . . . . . .
31-51
. . . . . . . . . .
Method of Calculating.
.
23
*.......25
Discussion of . . . . . . . . . . .
Test, Object of
. 55
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. . ..
. .
52-62
.. . . .
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Table of . . .
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.
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Readings, Curves of . . .
Results,
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24
. . . . . 54
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19
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5
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5
11
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4:39
4
The"HARVARD".
'V
3
4
Left NW York
5.00.
@ataiua Iewint
7.6"
hstes
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itle
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3.19
ek
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snd
1.13 A. 4
Iebgba
crew
ft Liebt all
U.s
sone
ftnoek alp ult
oft
1A
Poll*: Ry bhs~g Light Ship
Nwset motA
P.1.. Rp 4& alpz"
Cape
en
4*09
4.56
5.34
6.00
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....
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THE S. So ELVA:D.
SERS=g TEBI 0
On Jane 25
am& 26 1WO a servloe test um
Wgmis
f %*
dividet up Is% tm
at.-Mto
boilers an#
d.
Maw
. 5.
made on tbe
This test was
t'h* swnines, which wzas
worked up by 1fvaw4 g. Vih&er end Philtl I. Totq.oaad
wbii i ft *e *f tOe tet
t felwlstug,
boilers.
'reston
-h
servIte con-
Iting dally t rips i etweeu
,Mile the rtepr.er ies
ditIos
aetaa
This teat fas raie uyter
on the
nam 71'W Tek
eb$eA of so twt w to fVA# 9t
gime aM boilens were
in
Wag
wAt the *no
Aetual servioe End not
what they eould be wsde to ao urder Ideal neo
such as often olttin vn trEAl tripe.
@origuiiption in e ajumettu
enc coal
*a te
tt
W3i the
eiginee by Ulossvv ?1e2er an
-
The specific ob-
to f1rit tte stei
Jeot o- the teiler test wee
t tono,
twrbIe
You.
STAW NAIVAkO
lb. EarvsvI La smeIa Ui. Mo Estrwoputmhip
Co. and was
tel*
in 1V41W
t
Iron Shipbuiling ant blae Wors (
OMa
asob's Za
MvWZr
Her engines and botllse were built %V the 1. & A. 72et.
oher 0.
She is
in servioe Lurling tk. atmmw mentbs
between Boston and New York, making the m
of 300 Nauti-
cal miles daily in fifteen hours, her average speed being
20 knots.
The general dimensions of the vessel are given
below.
Length between perpendiculars . .
386 ft. 6 in.
Breadth of hull moulded . . . . .
50 ft. 6 in.
Breadth over guards . . . . . . .
63 ft.
Dopth moulded. . . . . . . . .
.
22 ft.
. ..
16 ft.
Draught normal
.
. .
.
.
.
.
Draught at trial,
mean 11. Y. to Boston)
16 ft. 2 in.
DESCRIPTION OF BOILERS.
The Harvard is fitted with twelve single ended Scotch
boilers placed athwart ship, having a fire room running
along the center line of the vessel on each side of which
are six boilers.
This fire room is divided into two
parts by a transverse bulkhead; there being six boilers
on each side of the bulkhead.
naces.
Each boiler has three fur-
The Hiowden system of forced draft is installed,
air being supplied under a pressure of 1.75" of water by
blowers,
Total grate area . . . .
.
.
.
.756
Total heating surface
.
.
.
29520 sq. ft.
.
Ratio heating surface to grate area
sq. ft.
39.0
Fire Room.
0
222:e asor
No6
Ile,
li-t ~
DESCOIPTIOIT OF FIRE ROOM AUD APPRATUS ISTALLED.
At the forward end of the fire room there is a coal
bunker placed athwart ship from which coal is supplied to
the six boilers forward of the bulkhead.
At the after end
of the fire room there is another bunker, also placed
athwart ship, there being through this a narrow passageway
connecting the fire room with the engine room.
The six
boilers abaft of the bulkhead are supplied from this bunker, which has a door on both starboard and port sides.
Overhead trolley tracks, which carry coal buckets, lead
from these doors along in front of the boilers on the
same side of the boat.
In the forward compartment there
are two tracks similarly arranged in front of the boilers,
but these converge to a single door in the forward bunker.
The capacity of the buckets was about 500 lbs. of the kind
of coal used.
The water consumption was measured by a Hersey hot
water meter loaned for this purpose by the Hersey Manufacturing Co. of South Boston.
The meter was installed
in the suction line between the hot well and the feed
pump.
The steam supplied to the auxiliaries was measured by
means of orifices.
These were made from plates about thr'eo
sixteenths of an inch thick, and had circular openings the
edges of which were rounded on both sides of the plate.
All auxiliaries except the forced draft blowers were
supplied from the starboard auxiliary steam pipe.
LMTHOD OF TESTING.
The test was begun at 7.10 P.M. on June 25, 1908 on
the 'run from New York to Boston.
Neither the standard
nor alternate methods of starting a boiler test as
recommended by the A.S.M.E. could be used.
The standard
method involves the drawing of all the fires at the start
and the alternate method requires the cleaning of all the
fires at the start and neither of these things could be
done without causing great inconvenience in the cramped
fire room and unnecessarily delaying the boat.
When the test was started the. steamer was off Captains
Island light in Long Island Sound and was well up to speed,
being in open water and having been under way for two
hours.
In starting and stopping this test we estimated.
the amount of coal on the fire room floor.
Although a
thorough inspection of the fires in all the 36 furnaces
could not be made, a considerable number of them were
looked at, and in the judgment of the engineer on watch
and those in charge of the test, they were in service
condition.
To make the speed required by the schedules
on which these boats run it
seems practically certain to
us that the condition of the fires at the start was the
actual service condition, and although individual fur-
naces may not have been in the same condition at the end
as they were at the beginning of the test, we believe
that taking an average of the 36 furnaces, the condition
of the fires at start and finish was practically the same,
for the end of the test came at 7.00 A.M. June 26 when
the steamer was off Minots Ledge Light, an hours run from
the dock.
That other conditions were constant during the
test is shown by the steadiness of the boiler pressure as
plotted, and by the fact that the total coal and total feed
water curves are nearly straight lines.
The A.S.U.E. specifications for boiler trials require
that the coal shall be weighed in buckets and then fired
directly from these.
Owing to the cramped space in the
fire room and the rapidity with which the coal had to be
passed out, it appeared impossible to weigh coal during
the test and no attempt was made to do so.
As one bucket
supplied nine furnaces it was manifestly impossible to
fire the coal directly from the bucket, so the coal was
dumped on the floor in front of the furnaces and fired
from there.
The coal used was determined by counting the number
of buckets taken from the bunkers, a man being stationed
in each compartment of the fire room whose sole duty it
was: tocount them.
Care was taken to have the buckets
filled flush with the top.
After the test we wei.ghed
four buckets full and -empty thereby getting our average
value for the coal contained in one bucket.
This weight
agreed. to -a pound with the average obtained from some
weighings made by the Steamship Company.
It is interest-
ing to note that, crude as this method appears, it
us a value for the coal used vhich agrees
gave
ithin l%,with
the figure obtained by the chief engineer of the company
as the average coal consamption per trip based on the runs
of a whole season.
The feed water was measured by a 6" Hersey Hot Water
Meter.
This meter was calibrated by its
found to under run 1/2 of 1%.
makers and was
Tests on a 4" Hersey meter
made at the Institute showed with cold water an under run
of 1/2 of l1. but with hot water an under run of l%. From
under
this it would seem that the 6" meter would probablZ/run
from 1/2 of l% to 1% and it
assume that it
is certainly reasonable to
was accurate within 20% which is well with-
in the error of the test.
It should be noted that this
meter was so placed that the water from the hot well flowed
to it by gravity.
Tjxe A.S.M.E.
regulations remuire that
feed water for hoilers undergoing test shall be weighed
in tanks.
When it is considlered that about 3000 lbs of
water went to the boilers every minute, and the cramped.
space on ship board is taken into account, it
is evident
that measuring the water by a meter was the best we could
do.
With a boiler placed athwart ship a very slight
motion of the vessel makes the water glass indication
valueleiss and so no attempt was made to ascertain the
level in the boilers in this way.
The engineers on
the steamer have found that by admitting a certain
amount of water on each trip the level in the boilers
is practically the same at the end of a run as at the
beginning.
During the test the 3/4" pipe which admits
this fresh water was opened for about fifteen minutes.
This water was admitted to the hot well and so passed
through the meter, which measured all the condensation,
the leakage only being lost.
It seems to us that the
necessity for keeping up speed and the fact that the
steamer had been under way for two hours when the test
started, and still
had an hours steaming to do when the
test stopped, would make it
very probable that the
height of water in the boilers was governed by service
conditions.
A strong check on this is the total feed
water curve which is a straight line.
As has been stated, the steam for all the auxiliaries except the blowers came from the starboard auxiliary
steam pipe.
The port line was entirely closed and the
by-pass around the reducing valve in the starboard line
was opened wide, so that all the reduction in the
pressure of the steam supplied to the auxiliaries was due
to the throttling action of the 1-15/16" orifice which
was placed. in the line.
The steam for the blowers came
from the port line ad. was measured by means of a 7/8"
orifice.
The quality of the steam was determined by a Peabody
calorimeter which was inserted in the main steam pipe at
the point where the main steam gange was tapped in.
Calorimeter-readings were taken three times during the
test and the results obtained were practically in agreement.
The A.S.M.E.
boiler trial specifications call for
sanples of flue gas for analysis.
Such an atalysis is
very valuable when good fair samples of flue gas can be
obtained. and gives an excellent indication of what the
boiler plant is doing.
But in the case of a steamer the'
uptakes are usuall
leaky and as a result a flue gas
sample is of little
value when obtained.
This being so,
no attempt was made to obtain flue gas samples during
this test.
The boiler pressure, water meter, back pressures on
the orifices in both the auxiliary and. blower lines, number of buckets of coal, the draft and the temperature of
the feed water were all observed
at ten minute intervals
up to 2 A.M. and at fifteen minute intervals thereafter.
The boiler pressure was read on the engine room gauge
and this, ( and all other engine room guages used ),was
specially calibrated by the Crosby Steam Gauge and Valve
Co.
The internal pressure on the orifices was that of
the boiler, since care was taken to have all the reduction
in pressure in these lines due to the throttling action
of the orifices.
The back pressure on the orifice in the
auxiliary line was read on an engine room gauge, while
that on the orifice in the blower line was read from a
gauge loaned by the Institute and calibrated by the authors in the Engineering Laboratories.
This gauge failed
at 11 P.M. and thereafter the steam supplied to the blowers was calculated from the data already obtained and
modified to follow the curve of the plotted draft data.
The number of buckets of coal passed out was kept by ten
minute intervals and every hour the amount on the fire
room floor was estimated.
In this way a very fair curve
was plotted showing the rate of coal consumption.
Samples of coal were taken at regmlar intervals during the test.
The average of a number of tests on the
calorific value of this fuel made in the Laboratory of
Heat Measurements at the Institute was 14,510 B.T.U. per
lb.
7
Engine Room.
I,
-Jj~
~I'tE
a
r
NIU
LEHOD OF CALCUATING RESULTS.
As soon as the data obtained in this test was
plotted it. was evident that the conditions were not constant throughout the twelve hours.
As far as the boilers
were concerned the conditions were most constant from 9
P. M. to 4 A. ML., and therefore only these hours were taken
into account in determining the performance of the boilers.
Messrs Fisher and Young found that the engines were
working steadily from 9 P. M. to 3 A. M. and they accordingly used these hours in working up the engine test.
The value of the average shaft horse power that is quoted
is the result of their work.
Whenever it
was necessary to work out the feed water
and coal rates it
was done as shown below.
It should be
explained here that the red line on the coal curve is
drawn through the points of estimated coal on the fire
room floor and so indicates the coal rate.
IETHOD OF DETERhUJINING THE COAL AND WATER RATES.
( from carve )
Total buckets at 4 A.M.
Total buckets at 9 P.M. ( from curve )
.
.
Buckets consumed in 7 hours . . . . .
Weight of coal per bucket ....
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
277
.
.
.
.
.
.
54
.
223
....
Total. coal consumed from 9 P.M. to 4 A.M.
Rate per hour .
.
506 lbs
.
.
.
.
.
112,800 lbs
.
.
16,100 lbs.
'Cubic feet of water fed at 4 A.M. C from curve) 24,700
"T
I
i
"
IT
9 P.11.
it
t
"
" in 7 hours
IT
"I
5,100
19,600
200
Add 1%
Total cubic feet in 7 hours
19,800
to0
Average Temperature of Hot Well; (9 P.M 4 A.M.) 111.9
Weight of one cubic foot of water at 1127F
Pounds of water fed in 7 hours
Rate per hour
F
61,86 lbs
1',225,000
175,000 lbs
STEAM FOR AUXIIIARIES.
In calculating the steam used by the auxiliaries the
following formula by Grashoff was used.
P
.
0.97
W = 0.0165 A
Where W= weight in lbs. per second
P= internal pressure in lbs.
C absolute
)
A =area of the orifice-in square inches
The weight as determined by this formula has to be
multiplied by a quantity ( called the " ratio of actual
to computed discharge") which depends on the ratio of back
pressure to internal pressure, when this is greater than
0.6, and upon the shape of the orifice.
From previous ex-
periment it was determined that for an orifice of the kind
used the factor by which W in the above formula must be
multiplied is within 10% of the mean betweon the factors
given by Grashoff for converging orifices and orifices in
thin plates.
The most inaccurate term in the equation by ihich the
steam was computed is undoubtedly the " ratio of actual to
computed discharge".
The error in this term is probably
not greater than 10% which makes the errors in the other
terms negligible.
Since the auxiliary steam is only 12.5%
of the total steam an error of 15% here would affect the
engine steam by less than 2%.
A sample calculation is given here in order that there
may be ho misunderstanding as to how the " ratio of actual
to computed discharge" was obtained.
Steam for blowers.
Size of orifice 7/8" dia.
Boiler pressure
Area
0.601 sq. in.
135# gage
150 lbs. abs.
Back pressure on orifice 94 lbs. gage-109 lbs. abs.
Ratio of back pressure to internal pressure 0.73
From the table on page 433 of the
"
Thermodynamics of the
Steam Engine" by Professor C. H. Peabody
Ratio
Ratio of actual to computed discharge
Back Pressure
Converging orifice
Thin Plate
Mean
Internal Pres.
0.75
0.89
0.64
0.51
0.70
0.94
0.69
0.82
Ratio of actual to computed discharge when ratio of back
pressure to internal pressure is 0.73 is 0.79
0.97
150
148
W ( lbs. per min.) =
0.0165 x 0.601 x 148 x 0.79 x 60
70 lbs.
D A T A
12 hours
Duration of test 7 P. M. to 7 A. Id.
Barometer
14.7 lbs
29.97"
140.2 lbs gage
Temperature of Feed Water (average 9-4)
202.7 F
Temperature of Hot Well
111.9 F
"
Boiler Pressure (average 9 P.I. to 4 A.M.)
175,000 lbs.
Feed Water per Hour
96.0%
Quality of Steam
1.76" of wate
)
Draught ( average 9 - 4
29,520 sq. ft.
Total heating surface
756 sq. ft.
Total Grate Surface
Ratio Heating Surface to Grate Surface
39.0
Vacuum ( av. Sand P.- 9 P.M. to 4 A.M.)
27.44 in.
16,100 lbs.
Horse Power of Turbines,
av. 9 P.M. - 3.00 A. M.
10,400
)
Coal fired per Hour
Total Engine Steam per Hour ( 9-3.00
)
Total Auxiliary Steam per Hour ( 9-3.00),
-s.
22,000 lbs.
153,000 lbs.
RESUTS
Heat of Combustion of Coal
14,510 B.T-.U.
Total Equivalent Evaporation
from and at 212 F.
179,000 lbs.
Equivalent Evaporation per lb. of Coal
11.1 lbs
Equivalent Evaporation per sq. ft.
of Heating Sgrface
Ooal burned per sq. ft.
of Grate
Boiler Horse Power (A.S.II.E. rating)
6.06 lbs
21.3
lbs
5,190
Heat absorbed by Water in Boiler
per lb. of Coal
10,700 B.T.U.
Thermal Efficiency of Boilers
73.86%
Total Steam per Shaft H. 2.
16.8 lbs
Steam through Turbines per Shaft H. P.
14.7 lbs
B. T. U. per Shaft H. 2.
265
Coal per Shaft H. 2.
1.61 lbu
Gauge Correotions.
j
W60
71
-O
A
0
I
-
I
a-a
I
Rtifrtta21
97
aR
28
3
U
a
i
.
4
i
Curve of Total Coal.
Curve of Tot&l-Feed- Water. (uncorrected)
Ir
to
/I
i
ri4;n
6
I
Ho
,a .1*W-
4n.
+ 1
4-4
74
00o
'
+4
+
4 99*
4
+
4
+
14, "o
f
/49,000
4
d
+
u
,*
11%ft
40
4go
Curve of Total Shaft Horse Power.
Curve of Feed Water Rate.
Curve of Steam for Turbines.
Curve of Total Auxiliary Steam.
/
+
'aQQ
I~I
I
qpo
400
,zoo
Curve of Boiler Pressure.
Curve of Back Pressure on Auxiliary Orifice.
Curve of Back Pressure on Blower Orifice.
Curve of Vacuum in Starboard Condenser.
Curve of Vacuum in Port Condenser.
11
Arb,
14
4l
X --.-
46
tp
/XIOI
-Qr/ke A-iuc
A~l limu)
0~0
Port Vmtuvrm.
'p
"a
I.
+
*1
torboard
Va.-U4M
Ql
lb-
4
Curve of Boiler Pressure.
Curve of Feed Wlater Temperature.
Curve of Draft.
a
It
#1
7-1'n e
41rg
A
4
7p
"04fr.
Bodler Presjure
130'
Z40
Fed W.tCr rempertUr
k0
20*
0
1.
/so"
Draf t.
14
'."
/0
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52
CAL0ULATION
Eqnivalent Evaporation
Boiler Pressure
.
.
.
.
.
. .
Barometer . . . . . . . . . . . . . . . . .
Absolute Boiler Pressure .
.
.
.
.
.
.
.
.
140.2 lbs.
.
.
14.7 lbs.
154.9 lbs4
Quality of Steam . . . . . . . . . ....
.
Q+XR et 154'.9 lbs..
1........
B.T.U.
.1157.6
Q at 202.7 F.. ..
..
...........
%
. 96.0
170.9 B.T'.J.
Heat to vaporize 1 lb. of feed water
(4% priming) . . . . . . 986.7 B.T.U.
Q
77.7 B.T.U.
at vacuum ...................
Equivalent Evaporation
175,000 X 986.7
966.3
,-179,000
lbs.
179,000
16,000
Equivalent Evaporation per lb. of coal
-
11.1 lbs.
Equivalent Evaporation per sq. ft. of Heating Surface
179,000
29,500
6.06 lbs.
Coal burned per sq. ft. of Grate Surface per Hour
16,200
756
= 21.3 lbsa
~1
5-3
Boiler Horse Power (A.S.DI.E. Rating
175,000 x 986.7
--------33,320
)
CALCULATION ( con.
5180
Heat absorbed by Water in Boiler per lb. of Coal
175,000 z 986.7
----------16,100
1
10,9700 B. T. U.
Thermal Efficiency
986.7 x 175,000 x 100
------------14,510 x 16,100
%
73.8
Total Steam per Shaft Horde- Power
175,000
= 16.8 lbs.
10,400
Engine Steam per Shaft Horse Power
153,000
14.7 lbs.
.
10,400
B. V. U. per Shaft Horse Power
-
1080 x 153,000
-----------60 x 10,400
265 B. T. U.
Coal per Shaft Horse Power
16,100
= 1.55 lbs.
10,400
DISCUSSION OF RESULTS.
From previous statements it
is evident that errors
of more than 2% in the coal rate and 1% in the feed
water rate are unlikely.
A possible error of 10
in the
aMxiliary steam could not affect the engine steam to
more than 1.2%.
An error of 1% in the feed water will
affect the engine steam by about 1%, so that the total
error in the engine steam is not likely to be greater
than 2%.
The ecuivalent evaporation is affected by five factors--the boiler pressure, the quality of the steam,the
temperature of the feed water, the feed water rate, and
the coal rate.
Any errors which are likely to occur in
the first three of these are .so small as compared with
the probable errors in the last two as to be hegligible,
so that the error introduced into the ecu ivalent evaporation per pound of coal is not greater than 2.56%.
With probable errors of 3% in-the shaft horse power
and 1% in the feed water rate, the total error in the
steam per shaft horse power would not be more than 3.5%.
The error in the engine steam and the coal per shaft
horse power cannot be more than 3.5% as can be seen by
the above figures.
11
55dw
COICLUSION.
This test was run under favorable conditions as regarcs weather and sea and the results given here are
average results obtained in regular service between
Boston and New York.
From a consideration of all the
errors entering into this work the results are seen to
be certainly accurate within 3.5fa and the probable error
is smaller.
We hereby express our thanks to all who have in any
way aided us in this work.
Respectfully submitted.:
Signature redacted
Signature redacted