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Ju
UN
61V
T H E S I S
TEST OF HARBOR TUGBOAT.
SADIE ROSS
Submitted to the Department
of
Naval Architecture and Marine Engineering
by
Kenneth H. Campbell
May 1929
25 029
CRA W4
Professor A. L. Merrill,
Secretary of the Faculty,
Massachusetts Institute of Technology
Dear SirThe accompanying thesis on "Test of
Harbor Tug Boat - Sadie Ross" is submitted in
compliance with the requirements of the Massachusetts
Institute of Technology for the degree of Bachelor
of Science.
Respectfully yours,
INDEX
Item
Pgge.
Acknowledgement1
Appendix
Cards
24
Sample
-
27
Computations
Coal - Heating Value of
Calorimeter
Engine Constants
Equivalent Evaporation
12 - 27 - 28
12 - 29 - 28
4 - 20 - 29
43
42
29
36
37
38
Efficiency
Overall Plant
Rankine
Thermal
41
39
40
I. H. P.
12 - 27 - 28
31
12 - 29 - 28
33
4 - 20 - 29
35
Curves
Calibration
I.H.P. vs. Revolutions
Run of 12
27 - 28
Run of 12 -29 - 28
Run of 4 -20
- 29
28
26
9
10
11
Item
Page
Conclusions
22
Data
Gage Calibration
Original
28
47
Discussion
13
Plan of engine room and piping
25
Procedure
5
Purpose
3
Results
Analysis of
Boiler Tests
Engine Test
Hot Well
17
8
7
12
Unit
Description of
3
1.
A C K N O WL 3 D G E ME N T
To Mr. Harry Ross owner of the boat on which
the test was run, Professor Evers Burtner upon whose
instigation the test was undertaken and who willingly
offered assistance at all times, Mr. Nicholas Oresko
who gave liberally of his time both in preparing for and
during the trials, Mr. John Booth, Jr. who assisted on
the run, Mr. Rad B. Clough engineer of the vessel whose
cooperation helped materially and Professor 3.J. Eames,
who kindly lent apparatus and advised as to the use
thereof; the author wishes to extend his thanks for
assistance rendered.
2.
3.
Test of Harbor Tugboat
Sadie Ross
PURPOSE:The purpose of this test was to find the
average water rate, and coal consumption of an ordinary
harbor tug.
The efficiency of the boiler and economizer
was also secured as completely as possible with the
means at hand.
UNIT TESTED:The boat in question is
a typical harbor
tug of the following dimensions, length 60.5 feet,
breadth 18.6 feet, depth 7.7 feet Gross tons 49,
net tons 27.
She is equipped with a main unit consisting
of a Bertleson and Peterson steeple compound engine
rated at 250 I. H. P.
The engine was built with
11 inch high pressure and 22 inch low pressure cylinders
and 15 inch stroke.
Since then the engine had had the
high pressure cylinder replaced by a 10 inch cylinder.
4.
This has been bored once and is now 10-1/8 inches
in diameter.
The boat was originally equipped with the
ordinary Scotch boiler but this has since been replaced by an Almy boiler of the following dimensions.
Grate area 34.3 sq. ft. - Boiler heating
surface 933 sq. ft.
Economizer surface 165 sq. ft.
As nearly as could be ascertained the engine
was built in 1904 and with the exceptions noted above and
the addition of new air and circulating pump has been
in constant service without any alterations except the
usual maintainence since then.
The new boiler was built in 1926 and has been
in service ever since.
In addition to the main unit the boat has the
usual auxiliaries consisting of circulating pump, and
air pump attached to the main engine, feed water pump,
donkey pump, feed water heater and injector.
fitted with a feed and filter tank.
She is
The boiler is equipped
with an economizer.
The arrangement of the piping system is shown
in figure one.
two.
The engine room layout is shown in figure
5.
After making a preliminary trip of investigation measurements were taken and the main feed line was
out and a water meter placed therein.
As the cylinders
were not fitted with indicator cooks it was also
necessary to make provisions for taking cards.
Cocks
were fitted and a reducing motion arranged off the air
pump arm.
An integrating counter was placed on the feed
pump and another on the main engine.
Thermometers were
placed to secure the following temperatures, hot well,
boiler room, feed line after meter, and stack.
In
addition readings were taken from time to time of sea
temperature and overboard discharge.
Coal was weighed
by means of a spring balance and ash bucket.
Owing to
the difficult conditions under which the test was made,
no attempt was made to weigh ashes.
taken but proved worthless.
Orsatt readings were
6.
RESULTS:Following are the results of
the tests.
The graphs and diagrams are
largely self explanatory.
Results will be
discussed in the pages which follow.
In plotting the curves time
was taken as the abscissa and the various
other readings as ordinates.
Thus for any
time during the run conditions may at once
be found corresponding.
CoL9
Erratla:
Ratio H. S.
-
'. S.
read 32.0 instead of 3.2
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12.
Hot Well and Feed Temperatures.
12 - 29 - 28
12 - 27 - 28
Feed Water.
123
127
124
126
126
124
122
125
127
121
119
123
120
126
120
121
Hot Well
Feed Water
126
- -
-m
126
-0
120
128
127.5
113
124
116
125
128
123
122
120
120
122
109
105
108
105
110
4 - 20 - 29
Hot Well
89
96
111
112
118.5
126
100
139
126
123
111
125
85
85
135
104
80
86
111
116
116
121
116
-
115
118
Feed Water
Hot Well
104
120
124
122
131
124
124
-2
122
122
112
124
121
128
131
125
121
129
125
126
122
118
123
126
109
131
120
116
131
132
13.
DISCUSSION:In considering the results of these tests,
these facts should be borne in mind.
The test was made
by men inexperienced in the form of testing.
Although
all had done considerable stationary testing in
the
laboratory with the exception of Professor Burtner none
of us had ever run an actual service test.
This fact
led to some slight but annoying inaccuracies such as
failure to synchronize watches duplication of readings
and the like on the first runs.
On the later runs, however,
these difficulties were largely overcome.
Next the test was made while the boat
was in actual service.
As all the test installations
were made by members of the testing party and time was
limited, the test being non commercial, it was not
possible to install all the apparatus one might have
wished.
No deviations from regular operation were made
for the benefit of the test data and hence it was extremely difficult to secure some readings such as power
variations and constant power.
Furthermore the engine
room was rather lacking in space for extended observations in fact many of the readings were taken with
some difficulty.
In evaluating results these errors were
introduced.
In weighing the coal the ash bucket and
a spring balance were used.
The swaying of the bucket
14.
introduced an error which was handled by estimating the
mid point of the swing on the scale.
The tare was taken
at intervals and assumed to remain sensibly constant.
In the feed line also some error was introduced by the fact that the injector was used at times.
As water from the injector did not pass through the meter
it was impossible to ascertain the amount so used.
Howevet, it was quite small and it seems fair to neglect
it.
In view of all the above it
is not fair
to assume results to be accurate to more than 5%.
The
carefulness with which readings were taken and the
results worked up would seem however, to warrant confidence to that extent. This of course assumes all
results to be free from numerical errors,
As the last
portion of the thesis work which includes practically
all the computations was done by the author working
alone and with the time limited;
there are no doubt
errors which a careful checking would have eliminated.
The results would seem to indicate, however, that the
numerical computations are substantially correct.
In considering the data sheets one is
struck by the number of apparently unused reading.
principal one of these is the feed pump data.
The
This was
15.
taken in order to provide a standby method of computing
water rate if anything went wrong with the meter.
The
other readings might be of interest in a more extended
study of the results of this test.
Before passing on to an analysis of the curves
and figures the viewpoint from which this data is worked
up must be considered.
As the principal interest of the
majority of parties concerned was in the economy of
operation of a steam tug the results were worked up with
this in mind.
The whole basis of comparison used is
that of horsepower hours of work actually done as compared with the amount of energy expended to produce the
same.
The runs of the 27th and 29th of December are
particularly what is meant.
In
computing the steam and
coal used on these days the average horsepower developed
was multiplied by the number of hours during which the
tug was actually running.
The coal and water, however,
were taken over the total time of the test.
This means
that all standby losses and manouvering losses are inoluded in the results.
In other words to take the run
of December 29th as an example to get one indicated
horsepower hour it was necessary to expend 44.8 pounds of
steam.
Probably 50% of this went into the condenser
without doing any actual work during the time the tug
was lying idle at the dock.
The author feels that this
16.
method shows more clearly than the ordinarily accepted
way of computing, the losses occasioned by enforced
idleness.
17.
Analysis of Results.
In considering the results of these tests
and comparing the three sets of observations it
should be borne in mind that they were taken under
entirely different sets of operating conditions.
The run of December 27th
average day.
runs.
represents an
The tug was fairly busy mostly on short
She ran to Lynn, South Boston, and the Atlantic
works but there were periods of idleness.
Different
duties were undertaken the tug running both light
and with a tow.
The run of December 29th represents a slack
day.
With the exception of two short runs the tug lay
at the dock with fires banked all day.
For purposes
of comparison this may be considered a day of standby
losses.
The run of April 20th represents the nearest
possible approach to continuous full power operation it
was possible to get.
With the exception of a short run
through the Annisquam River and canal the vessel was under
full power from 2.30 A.M. when she left Boston until 5.15
when she arrived at Gloucester.
She there entered the
tidal river and proceeded to Essex. This part of the run
is included in the chart as being of general interest and
18.
completing our test but is not worked up in the computations.
On the whole it seems fair to consider this
a representative full power run.
With all the points already discussed well in
mind the tables of results require some further explanation.
Under the condition taken we should expect the
water and coal rates to be less on the longer run than
on the harbor runs and the day of standby losses to show
the greatest expenditure per horsepower.
A reference to
the engine test figures shows that while in general this
holds true it is not strictly the case.
In the matter of steam consumption this holds
very well.
The day at the dock showing 44.8 pounds per
horsepower developed per hour the day of harbor runs
showing 30.12 and the period of continuous operation showing 21.9 pounds, a considerable reduction in each case.
In the matter of the coal however this does
not hold.
Here we have, speaking again on the basis of
horsepower hours, for the day at the wharf 6.85 pounds ,
for the day of short runs 3.19 pounds and for the long
run 3.3 pounds.
In variance with our expectations we
find that continuous operation requires .11 pound more
coal per horsepower.
the boiler results.
This may be readily explained by
19.
Boiler results were figured in two ways, on
the horsepower basis as shown in the computations and in
the usual manner.
Both these methods check closely.
For
the sake of consistency we will consider only the horsepower figures.
Here we note an amazing discrepancy.
The
efficiency of the tugs' boiler while engaged in harbor
work was 70.4% while the efficiencies of the standby and
full power day was practically the same about 49%.
Some explanation of this may be given on the
grounds that the efficiency of the first day is too high.
This is perhaps true as several different observers were
engaged in the weighing of coal on that day.
But even
allowing for as great an error as 10% the efficiency would
still be 60% or about 10% higher than that of the full
power run which seemingly should show the best efficiency.
The author believes this to be due entirely to
the firemen.
On the day of Dec. 27th both firemen were
experienced and one of them seemed to be particulary good.
On the day of April 20th both firemen were greenaIe one
of them had never fired before and the other had had but
a few weeks experience.
As an additional proof we may
note the fact that the evaporation per pound of coal is
the lowest on this day of any of the three 6.2 pounds of
water per pound of coal as compared with 6.75 on the day
spent banked and 9.27 on the day of short runs.
The
20.
pounds of coal per square foot of grate surface is practically double that of the short run day being 17.2 as
compared with 9.74.
The data on quality of the steam proved very
unsatisfactory.
For some reason it was impossible to
build up a sufficient pressure in the calorimeter to
superheat the steam.
Saturated steam was, however, ob-
tained on two occassions and used as the basis of computation.
The feed heater which was of the primary type
operated by passing exhaust steam from the main engine
and auxiliaries through it.
It was open to the condenser.
This means that for a 24 inch vacuum the temperature
therein should be 1370 F.
This means that when the tem-
perature in the hot well runs up over this figure or when
the vacuum runs up a little, the device acts as a cooler
not a heater.
That this occurs at other times for some
cause is clearly shown by the figures.
Many of the cases
where the temperature of the feed is higher than that of
the hot well might be the reverse had the thermometer been
left longer in the feed and filter tank.
Such a heater is injurious for the following
reasons:-
first it puts an undue load on the condenser.
Some of the condenser cooling water is used for cooling
this feed water which means that less may be devoted to
21.
the purpose for which it was intended.
This means a
loss in vacuum and hence in engine efficiency.
Second
the colder feed water increases the load on the economizer.
This means that more heat is
taken from the stack
gas resulting in a reduction in draft.
Thirdly the colder
water entering the boiler means more heat required to raise
it
to the vaporization point resulting in a higher fuel
bill.
22.
CONCLUSIONS.
As regards the boiler and economizer we may
say that with proper firing the efficiency of the boiler
is quite satisfactory.
Sterling "Marine Engineers
Handbook" gives values ranging from 62% to 76.4% efficiency.
If this boiler can be made to average 65% it would seem to
be in accordance with usual practice.
To do this, however,
the firing must be carefully watched.
It would be interest-
ing to ascertain just what the economizer is doing.
To do
this a thermometer well must be inserted between the
economizer and boiler proper.
As this well would be under
full boiler pressure it was impossible for such an insert
to be made with facilities provided.
The efficiency and
steaming of the boiler could be considerably,unproved
by the use of higher temperature feed water.
At 150#
gage pressure the temperature of the water leaving the
economizer could well be 3650 or 366 0 F.
The coal consumption is excessive, viewed from
modern practice.
Of course allowance must be made for the
type of installation and conditions of operation.
A first
class feed heater of the closed type should, however,
reduce this consumption considerably.
With careful fire-
ing and the use of such a feed heater it does not seem
impossible to reduce the consumption by one third, as two
23.
pounds per I.H.P. per hour is not especially a high
efficiency figure.
As regards the engine the steam consumption
would seem to be quite good for this type of an installation.
On the day of continuous running it was
only 21.9 pounds per I.H.P. per hour and on the day of
harbor runs 30.12.
It is difficult to see how this could
be materially improved with the existing installation
although a higher vacuum would certainly help some.
Sterling "Marine Engineers Handbook" gives values for
compound engines, most of them larger than this, ranging
from 18.4 to 29.8
#
/ I.H.P./ hr.
In view of these
figures the consumption of this tug would seem reasonable.
24.
A P P E N D I X
FEE D Pumfl
Do N KE.
Pump
U
TES T OF
HAR630f\ TUcz
A0E R\OSS
ISOS
40
o0
4o
(.o
so
100
120
1y + 0
14c)
IS
PM
-1
-l4 2
3
-..-
Cx
-0-4
..
44
3
js
Ia
uu
A
00
444
121
9-ov-
b
S
won
.10
(33
aa
C4
29.
COVPUTATIONS
Engine Constants.
Area H. P. Cylinder piston (10-1/8" dia.)
80.52 square inches
Area H. P. piston rod (2" dia.)
-
3.14 square inches
Area of crank end
:
77.38 square inches
Area L.P. Cylinder piston (224-" dia.)
* 388.8
Area L.P. piston rod (2-3/8" dia.)
*
Area crank end of piston
= 384.37 square inches
Area L.P. Cylinder piston
3.14 square inches
385.66 square inches
of piston
plan
I. H. P.
4.43 square inches
388.8 square inches
Area H.E. Piston Rod
Area H.E.
la.0 ,
=
33,000
p.n.
33,000
mean effective pressure
where p,
1
=
stroke in feet
a
*
areof piston (net) in square inches
n
*
number of R.P.M.
Horse Power Constants
High Pressure Cylinder
H E
.a
33000
JA
12
square inches
x
8052
33,000
.00284
C
E
.a
33000
14
12
x
77.38
Z3000
*
.00273
Low Pressure Cylinder
H. E.
C.E.
.. jt.
33000
*1i
_A
=
33000
14
12
*
.0136
=
.0136
33000
12
x
384.37.
33000
:31.
COMPUTATIONS
Average M.e.p. and I.H.P.
Run of Dec. 27, 1928
Low Pressure
High Pressure,
Head End
Head End
Crank End
55
60.5
17.8
19
40.6
39.5
22.0
20.8
91.5
95.0
23.2
21.4
98.7
103.0
19.1
18.5
103.5
98.7
21
21.5
19
19.9
100.5
103.
96.5
94
19.1
19.8
84.0
92
16.75
16.75
96.8
98.1
19.7
19.95
100
94.0
20.5
21.5
98
97.7
19.4
20.5
97.7
98
19.8
20.1
95
99
19.5
19.5
1173.4
256.85
90.0
19.92
Sum 1157.8
Ave.
Crank End
88.0
Time 6 hours.
37.
I.H.P.
35.9
(Average R.P.M. :
40.6
258.2
19.93
148.5)
40.3
32.
Total I. H. P. . 153.8
Water Rate .
296 x 62.5
153.8 x 4
Coal Rate a
1960
153.8 x 4
30.12
3
3.19
#
#
water / I. H. P.
coal / I. H. P. / hr.
/ hr.
33.
COMPUTATIONS
Average M.e.p. and I.H.P.
Run of Dec. 29, 1928.
M.E.P.
Low Pressure
High Pressure
Head End
Sum
Ave.
Head End
Crank En d
Crank End
102
106
19.7
19.3
103
101
20.7
21.1
80.6
80
14.3
16.6
91
90
17.6
17.4
86.7
88.8
17.6
18.3
87
89.4
17.8
18.7
79.5
88.6
20.4
17.6
76.0
73.5
20.5
21.2
89.5
93.0
23.2
23.4
795.3
810.3
171.8
173.6
19.09
90.03
88.37
19.29
I.H.P., at 135 R.P.M.
Time 11 hours.
35.3
33.2
33.9
Total I. H. P. 137.8
x#/ cu. ft
Cu. ft. water
=
#/I.H.P./ hr.
Water rate n
time
Coal rate -
A
coal
time x H.P.
x
horse power
= #
/ I.H.P./hr.
35.4
34.
Water Rate
w
Coal Rate
:
x 62.5
x 137.8
:
44.80 # / I. H. P. / hr.
3300
3.5 x 137.8
:
6.85 # / I. H. P. / hr.
345
3.5
35.
Run of April 20,1929
M.E.P.
High Pressure
Cr ank End
Head End
Low Pressure.
Head End
Crank End.
106
103
18
20*4
98
100
18.9
20.70
98.8
100
19.3
19.85
94
17.4
19.0
397
73.6
79.95
18.4
19.99
38.7
42.
99
Sum.
401.8
Av.
100.4
99.2
I.H.P. at 154.2 R.P.M.
I.H.P.
41.8
43.8
Total I.H.P. 166.3 over 2, hours.
Water rate :
Coal rate
:
146 x 62.5
166.3 x 2.5
1370
166.3 x 2.5
21.9
:
# /
I.H.P./ hr.
3.3# / I.H.P./hr.
36.
Equivalent Evaporation.
From and At 2120
Run of 12-27-28
Evaporation as is 30.12# from average feed temperature
F and average pressure of 130# / in. 2 gage.
of 1230
130 x 15 = 145
at 145#
q = 327.4
L a 865.4
From calorimeter reading quality
=
Total heat B.T.U. at our conditions then
or
x L
+
865.4
x
(q - f)
a
H.
.95 + (327.4 - 91) : H
822 - 236.4 z
1058.4.
Then factor of equivalent evaporation is
1058.4_
970.4
:
1.085
# water F & A x 970.4
fuel x heating value per
Eff.
30.12 x 1.085 . 970.4
3.19 x 14,200
=
70.4%
95%.
37.
Equivalent Evaporation
and
Boiler Efficiency
Run of 12-29-28.
Average Pressure 125# gage
Average Temperature feed water 113.7
Total heat
H = (q.
-
f)t A, r
(324.6 - 81.7) + 867.6 (95)
:
1067.9
Factor of equivalent evaporation
:
Eff.:
1067.9
1.095
970.4
44.80 x 1.095 x 970.4
6.85 x 14,200
38.
Equivalent Evaporat ion
and
Boiler Efficiency
Run of 4 - 29 - 29
130
#
pressure
H:
r,
x
=
122.40 F
+ (q - f)
+
(865.4)
95.
feed temperature average.
(327.4 - 90)
= 1059.4
Factor of equivalent evaporation
:
1059
970.4
Boiler Efficiency.
Eff.
:
#
water
F & A x 970.4
x heating value.
#- fuel
21.9
3.3
=49.5fo
x
x
1.088 x
14,200
970.4
:
1.088.
39.
Rankine Efficiency
Run of 12-27-28
=
Rankine Efficiency
Hi - H2
Hi - 4
1192.9
1192.9
-
896.2
104.87
327.3'0
Run of 12 - 29 - 28.
Rankine Efficiency
16192.2 - 923.7
1192.2 - 125.86
25.101o
Run of 4 - 20
Rankine Efficiency
-
29
=
1192.9 - 921.1
1192.9 - 123.86
:
25.3 7o
40.
Thermal Efficiency
of Engine.
Thermal Efficiency
*
B T U equivalent of horsepower
# Steam ( Total heat - heat liquid at exhaust
Wa ti-
q2 )
Run of 12 - 27 - 28
T. E.
=
2545
30.12 (1088)
= 7.83%
Run of 12 - 29 - 28
T. E.
2545
44.8 (1066)
:
5.32%
Run of 4 - 20 - 29
T. E.
:
2545
21.9 (1074)
a:s
10.85%
41.
Overall Efficiency
of
Boiler and Engine
Efficiency
:
r
Output in B.T.U.
Input in B.T.U.
B,T,U. equivalent of one horsepower
coal x heating value of coal.
#
Run of 12 - 27 - 28
Efficiency
55
5119(14200)
5.61%
Run of 12 - 29 - 28
2545
6.85 (14,200)#
Efficiency :
: 2.62%
Run of 4 - 20 - 29
Efficiency
u
2545
3.3 (14,20)
a
5.43 %
42.
Calorimeter.
Cal. Press.
Sat. Temp.
Cal. Tempt.
Superheat
20.1
216
228
0
20.11
215
228
0
20.1
225
228
0
20.1
228
228
0
20.1
225.5
228
0
20.1
225
228
0
23.1
232
235.5
0
25.1
240
240
0
22.7
232
235
0
H2
a
xrl
1160.4
=
xi r 1 + 331.4
X,
X,
:
4 q
829.0
ri
829.0
862.3
635.5
870.9
r : 862.3
U
96fo
x (870.9)
1156 : 320.5 4
X
1
=
.95 or 95%
Total Heat.
1156.2
1160.4
43.
Heating Value of Coal
by Bomb Calorimeter
Computations.
5,650
Calories expected 6,666 x .850
Theoretical expected rise
65
2356
:
2.40
(2356 a equivalent weight of water)
60% of expected rise :
Temp.
rl
at 60% : 1.44 + 26.30 z
= t2
n 1.44
2.4 x .6
27.74
26.30 - 26.30
5
r
tln
where
r
: rate of rise
ty
:
t
r
= time firing to start.
temperature at start
temperature at firing point
Hence r
1
r2
n
: 0
no rise correction.
29.10
3 - t4
-
28.85
p
where.
rate of cooling
r2
maximum temperature
final temperature
tg4=
p
r 2:
:
time from maximum to finish
.028.
and as b - a :
2 minutes
44,
Then final temp. corrected.
(2 x .028)
+ 29.1 :
29.15
Then
total rise
-
29.15
-
a
26.30
2.850
Total calories =2356 x 2.85 : 6,720
Calories per gram :
6,720 4 .85
B T U per lbs. : 7900 x 1.8
.
=
7900
14,200
Hence heating value a 14,200
45.
Heating Value of Coal
by Bomb Calorimeter.
Minutes
0
a.
b.
c.
TeMp,0
Minutes
C.
Temp. 0 C.
26.30
9
29.10
26.30
10
29.00
2
26.30
11
28.99
3
26.30
12
28.99
4
26.30
13
28.90
4.5
26.60
14
28.90
5.0
27.70
15
28.88
5.5
28.40
16
28.85
6.0
28.90
6,5
29.00
7
29.10
7.5
29.10
8
29.10
Fired
Weight of sample
.850 gram..
Weight of water
1900 grams
Water equivalent of calorimeter 456 grams
Assume heating value of coal 6,666 Cal per gram.
46.
Gauge Calibration Data
200# Gauge
Actual
Corrected
Actual
Corrected
99
100
134
135
104
105
139
140
109
110
144
145
114
115
149
150
119
120
154
155
124
125
159
160
129
130
Vacuum guage
30# gauge.
Reading
Corrected
Reading.
5.4
5
10.4
10
15.1
15
Reading
5
9.8
Corrected Reading
6.5
11
13
13.95
13. 5
14.8
18*8
20
22
23.4
26
27.6
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