A comparison of steam and electric drive in no. 4 building of Brown & Sharpe Manufacturing Co.

FOREWORD.

Thanks are .due to Brown & Sharpe 1,Pfig I Co.

for' courtesies extended us in the preparation of 'this thesis.

We desire to make especial" mention of the assistance afforded us by Mr. W. T. Hatch, Chief Engi-near of th,s Company, Mr. Henry H. Fales, formerly

Assistant Engineer, and Mr.

vrm.

l\laclanachan, Chief Electrician.

Respectfully submitted,

Mass. Inst. of Tech. t'lay 20, 1911.

... 'j

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rShovY /n q

r;-The purpose of this thesis is to show what advan-tages are deri''red from the use of' electric instea.d of steam drive in~l Building. In order to present the sit-uation clearly it ~Nill be nece seary to give a brief

de-scription of the ata.te of affairs that exi stan at the plant early in 1910.

At that time the Bro\~ & Sharpe Mfg. Co. was main-taining fiTe separate power plants, each of which supplied a distinct group of buildings with heat and power. In all cases the engine which provic.ed power to the building was located on the first floor or basement. The boilers also occupied space that was extremely valuable for manu-facturing purposes.' The labor costs were very high,

since each engine required an engineer and in some cases an assistant, and each set of boilers at least two atok-era.

Arte r consiciering carefull:.vthe advantage sand disadvantages of the isolated power plants, the Company decided to consolidate four of them into one central plant. The fifth because of its isolation from the central plant was not included in the plan. Some of the advantages which are hoped to be derived from the consolidation of

the plants are as follows:- the large plant with electric

driTe will make possible a great reduction in labor ex-penses; it will make possible econornica.loperation of au-tomatic stokers, and thus allow the use of low-grade coal without excessive smoke; it will eliminate the losses due to the belts from the enginesto the floors; and will make available for manufacturing purposes a.large amount of floor space now occupied by the boilers and engines; it. will allow the operation overtime of separate buildings, without necessitating the use of an engine in each of the buildings, during the period, but instead the load may be

carried by one or more engines working at full load and under the charge of fewer engineers than was possible un-der the fornler conditions.

The present plana call for the removal of the recip-rocating engines from the isolated plants to the central plant, where they will be used to drive 230;volt,3M~,A.Ce generators. The'exhaust will be utilized in an exhaust

steam turbine coupled to a 750-k.vre, 240-volt, 60~

alter-nator. It was hoped that this plant would be completed in time so that the cost of electrical power supplied to #4 building could be determined, but owing to delays incident to the delivery of apparatus this cost cannot be determined, and it will be assumed that the power is to be obtained

:from the narragansett Electric Lighting Coe

Building, ma3r be briefly de scribed as follows: - In a boil-er room 60' x ?5' thboil-ere are installed two Stirling boilers

of 200 B.H.P. each, designed to supply steam at 150 lbs.

8,

and 100 degrees superheat. The boilers were hand fired, and were equipped with a fan so arranged as to aid the

draft caused by the stack ~lIhenit fell belo'",.a fixed value. These boilers yrero installed in 1906, and at the tiXIlG of this

\

teat were in excellent condition, although in need of cleaning.

.

Two Harrison boilers, installed about 1885, were

used to supply st~wn for heating and for running the

ele-vator plOOp, while the two Stirling boilers delivered steam to the engine, which supplied the power to the building.

In the engine room, 56' x 24', there was installed in 1900 a 20~ x 42ft _{Rice and Sargent simple non-condensing}

steam engine. This delivered abont 300 R.P. at 90 R.P.M. The ex-~aust was led to a feed water heater, which heated the feed to about 80 degrees Centigrade. lIone of the ex-hau'st from the engine \Vas used again in the boilers.

Power was transmitted to the six ~loor8 of the building by means of belting and jack shafts. On each floor friction clutches were placed between the line and jack shafts, in order that a certain portion of the floor could be thro'\m off if nece Bsary.

In operating #4 Building electrically three differ-ent plans were considered; the first. was to install one motor of about 300 R.P. to driTe the entire mill; the

se-cond waa to use individual driTe) anci the last, group drive. TIle first was deemed impracticable, since the space occupied by the jack shafts and beltinr; woule..not be available for mm1ufacturing purposes, and since the loss in the jack shafts, which was about 25% of the total load, would not be eliminated by this method. The second plan necessitated costly changes in the. arrangement of the line

shafting, and called for the throwing out of moat of it, and would cause serious interruption to the continuous op-eration of the machines.

The last pltm, nmnely the group driTe, was consid-ered to be the best for this building, since it would re-sult in no interruption in the operation of the plant, and would eliminate the jack shafts and jack shaft belting.

If the bUilding had been new and the'machine s not yet in operation, there is no doubt but that individual drive would have been used, since its use results in a bet-ter power factor for the system, and a saving of power, since belting losses are practically eliminated.

In order to determine what motors should be in-stalled on the different floors, a 3q R.P. motor was used

to drive the separate line shafts, and the input noted by means of a Westinghouse Graphic Wattmeter. This work was done by

the Engineering Department of the company. As a result of these investigations it was decided to install the follow-ing motors on the various floors:~ On the first floor, one 25 R.P. and 'one 10 H.P.; on the second floor, one 35 Ff..P~~; on the third , one~5 R.P. and one 5 R.P.; on the fourth, one 50 H.P. and one 5 H.P.; on the fifth, one 35 H.P.,

two

20 H.P., and one 15 H.P.; and en the sixth, two 50 H.P.,

one 20 H.P., and one 25 R.P. This makes a total of 380 H.P. These motors were manufactured by the General Elec-'tric Company, and were 230-volt,

3-f

Induction motors,

e-quipped T,vi th starting compensators and overload release. Current was supplied from the feeder panel at the power house thro~h cables to the various f~oors of #4 Building. Fuses were place~ in the feeder panels, and

also on the generator side of each starting c~npensator,

bf.l.t no circuit breakerd were used in the line other than those at the feeder panels and the compensator boxes.

Before the steam plant was removed, opportunity ';vas offered to get data for the operation of the machinery by steam •

For any comparison of stemn and electric drive in thi mill

it

is necessary to know the ~team Horse-power re-quired to run it during the average day, and the coal and

water used. To find out if the boiler is operating at good efficiency a bo~ler test must be made also.

The load on the engine was found by taking indicator cards at frequent intervals throughout three days.

Two tests on the steam plant were made; one with the boilers (Stirling) supplying the engine alone, and one with the boilers supplying the auxiliaries and engine. The pur-posa of the first test was to get the efficiency of the

engine, and that of the boilers, and that of the second to get the amount of coal and water used in the boilers to supply steam to the auxiliaries and engine.

In

order to obtain roughly the horse-power delivered to each of the six floors the following method was used. With all the fioors in operation indicator cards were taken

at the engine, then the sixth floor was throvm off by means of the clutch connecting the line to the jack shaft, and indicator carda again taken. The difference between the

two

engine

I.R.P.

was the R.P. delivered

to

floor six, plus the friction losses due to the transmission of this po~rer to that floor. Then the clutch was again thrown in, and the operation repeated for all the other floors in turn.

To determine the efficiency of the engine and also to determine the thermal efficiency of the boilers, a test was made On the engine and boilers. During this test the

auxiliaries were r2n by the set of Harrison boilers, and steam was delivered from the Stirling boilers to the engine alone. This was lnade necessary by the fact that there was no means of weighing the eXhaust from the engine, and the only practicable way of dete~ining the steam consumption was by measuring the \vater fed to the boile }~6. To do this

tm

feed water pipe line was cut and a barrel was arranged to receive the water fro~ the feed water heater placed in ~he exhaust pipe. After being weighed the water was allowed to ,flo.~linto another barrel, whence it \vas dra~m by the feed pumps and forced into the boilers.

Before the start of the test the fires were allowed to burn low, and were then thoroughly cleaned. The teat was begun at nine o'clock, at which time the barrel

supply-ing the feed pump was full, strings were tied around the water glasses at the level of the water in the boilers,

in-dicator cards were taken, steam pressure and tempe rature at

tm

engine were noted, R.P

"!\~.,

and temperature of the feed wate r read.

Readings of the instruments were made ever~' fifteen minutes from nine to fi~e with the exception of the noon hour, when the plant was shut down.

A short time before the conclusion of the test the fires were cleaned, in order that they might be in the same

condition at the conclusion of the test as at the beginning. At the end of the test care was taken to see that the level of the water in the boilers was the same as at the start, and that the barrel supplying the feed pump was full. If this were so the total amount of water fed to t~e boilers from nine to five was the amount of water poured into the barrel from the start, when the barrel was fUll, to the conclusion, when the barrel was again full.

A sL~ilar test was luade on Nov. 9, only in this case the auxiliaries were also connected to the Stirling boilers! The purpose of this test was to find the efficiency of the

boiler, and the amount of water and coal used in the boiler

B,

to furnish steam for the engine. The duration of the test was the same as the first, but readings were taken every half' hour.

The coal used during each test was carefully weighe4

the.

as was also the case in regard to11ashes.

The heating value of the coal was obtained by tests made by the engineering department of the Brown

&

Sharpe lJIanufacturing Compan:{. Barometer readings were obtained rram the United states Weather Bureau office at Providence, located adjacent to the plan,t.

All instruments u.sed in the tests were calibrated.

gage testing device; the engine thermometer was calibrated

by inserting the bulb in a bath of oil in which a United

states Goverrunent tested standard thermometer was placed. The bath was gradually heated, the oil was kept tho~oughly

stirred by means of a stirring device, and readings of the

s

t'~10 thermometers were noted at the same time. When the

maxi~,~ point of calibration was reached the bath was

al-lowed to cool off gradually, and readings of the

thennom-sters were taken as before. This method was made

neces-aary by the fact that a thennometer of this t~~e,- with a

tube bent at right angles,- is very sluggiSh in its action.

The thermometer by means of which the feed water

temperature was noted Vias calibrated in the h.eat laboratory of the Massachusetts Institute of Technology~_, by comparison with a government standard.

The Crosby steam engine indicators wera calibrated

at the factory of the Crosby cmnpany, and were found to be

accurate to within two percent.

Calibration curves of all instruments will be found

Before the installation of the new s~itchboard

op-portunity Vias offered at the pOVler house for the

insar-tion of a Westinghouse graphic wattmeter in the feeder

Bupplying floors 1, 2, and 3, and in thoJe supplying the

/0

4th, 5th, and 6th floors respectiTe1y. Due to the fact

that the sixth floor input as measured by the watmeter

was far below wnat was expected, i.e., 87.4 R.P. a~ainst

102.7 R.P. steam, it was decided to check the sixth floor.

Sinca the feed panel had been between times so arran~ed

that opporttmity was no longer offered for the insertion

of the wattmeter, this floor was checked by indicating

separately each one of the four motors installed. The

result was 114.3 R.P., which checked with the 102.7 H.P.

for stea~m driving.

The graphic Wattmeter was checked b~y being placed

in series with a General Electric recording watt-hour

meter. The two were run in series 11ith a 50 H.P. motor,

the lar.t'1'esto available ) for three hours. Readings of

Tolts and amperes were made with instruments of knovm

accurac~ in order to obtain the power factor.

The graphic wattmeter is provided with a small

calibrating weight BO arranged that with voltage, but no

current, on the mete r, e.ndthe \7eight hung on an arm on

the apparatus, the indicating point should travel a

This calibration was tried, B.nd the mete r fulfilled the above condition in each case. However, its readings did

not agree with those of the General Electric meter, which

had just been ca.libra.tedby the General Electric Compan~;. This Integrating meter ,yas also tested in the Engineering Laboratories .of the Massachusetts Institute of Technolo-&y. It was ce.librated as a single phase meter, as sug-gested in its accompanying instnlction book, with the

current coils in series, and the potential coils in

par-allel. A voltage y{as obt~tined approximately equal to

the voltage at the Bro~m & Sharpe Mfg. Company's plant, a.ndthe Bame current was used. The power factor VIas

varied from 0.50 to 1.00.. Variations in power factor were obtained by different division of the load between reactance and resistance coils.

Plota of this test will be found appended.

The integrating meter was compared with a standard instrument of the Standardizing Laborato~r, and was found to be correct. The indicated error of the Westinghouse Graphic Wattmeter was then detennined as .5li

t,

50 that

its readings were multiplieu by 1.51 throughout. This seems to be a ve~i large correction, but is justifiable. The total electric input, corrected, is seen to be larg-er than the consumption from the steam engine, and the

expected saving of 78.4 R.P. (see page2/, ) from the

elim-ination of the jack shafting may seem lost, but it must

be remembered that the electrical figures Show input from

the power house to the building. From this must be

sub-tracted a 10

%

line loss, obtained by noting the drop in

voltage between station and motors, and about 13

%

for

motor inefficiency.

The efficiency of these motors, a.s quoted bji the

manufacturers, is from 86 to 89

%.

Allowing for these losses we find the electrical

output very nearl~/ equal to the stearn horse po\ver output,

minus the belt and shafting losses.

Time 11:40 11:55 2:00 2:30 2:45 3:00 3:30 4:00 4:30 5:00 5:30 av. LOAD ON NOV.?, 1910 R.P. 314.0 286.0 298.? 295.? 308.3 302.1 284.0 290.6 28?8 284.1 285.? :323T:tf 294.3 13, Average R.P. l:rov. 7 294.3

Average lI.F. Jrov. 295.9

Average R.P. 1Tov.9 287.6

877.8

TEST OF NOV. 8, 1910 Detennination of Engine Efficienc~r Engine alone op boilers

14,

Length of te at 9 - 5 7 hra. (Shut down from 12-1)

Lbs. of water 49,507 Iba Ash 1,649 Ibs Barometer 29.74" 14.61 1bs 0 Temp of feed 143.6 F =!/--#2Buckwhe at .12,100

B.T.H.

Lbs. of coal 8,580

Steam pressure gage 119.211bs. abs.

steam Temp. 414.0

"F

LOG OF lTOV. 8.

Time TemP6ste~ress.Gage E.P. Temp.Feed

T. F

Temp.()C 9:00 396 106 287.1 61.0 9~':.15 399 104 292.8 58.0 9:30 397 105 295.3 56.0 9 :45 . 393 106 296.6 61.5 10:00 392 107 303.9 62.5 10:15 391 105 290.4 64.0 10:30 395 105 308.2 62.0 10:45 399 105 307.1 65.0 11:00 400 108 304.8 64 11:15 395 104 290.0 64 11:30 390 108 298.0 64 11:45 395 105 301.1 63 12:00 404 105 28B.4 63 1:00 355 102 284.8 65 1:15 347 105 305.6 58 1:30 380 107 298.2 64 1:45 396 106 296.7 62 2:00 405 106 294.5 65 2:15 410 105 297.3 60 2:30 407 105 292.2 62 2:45 405 105 301.7 65 3:00 410 106 292.5 63.5 3:15 412 107 296.2 63 3:30 408 105 285.7 60 3:45 409 100 308.3 59 4:00 412 104 291.1 62 4:15 415 106 284.2 62 4:30 412 102 291.8 63.0 4:45 423 104 301.7 64.5 5:00 413 106 ) 290.7 64 )119"11 T3i54 )287 6.9 )1870.5 -399.03 105.13 29rr.89

62.3

+15. -.5

corr.414° F corr.l04.6 corr.52.0 0 E

-=143.60 F

"

Calculations of Engine and Boiler Efficiency

4°507 :':;

.'7 ::;"7072.4

#

water per hour :117.87

#

per minute

At p ~ 104.6

I,

T ~ 331.l4~, R: 1232 B.T.LT.

Assuming at atmospheric back pressure - 14.6

#

B.T.n.

used per pound of water ~ 1232-179.9

.::.1052

1 R .PI.=-42.42 B.T.

n.

,per minute i. 42.42 .295.9

Engine Eff .~-1.-0027-117.9 -- 10.12

;t

. 0

Boiler feed temperature 62 C Q62o=111.6 B.T.D.

Heat absorbed in :Boilers: 1232-112= 1120 B.'I'.U. per lb.

Heat given up by coal: 8580 *l2l00

=

14820000E.ID.U. per hr.

7 "

Boiler Eff. =1120x70~2

=

53.4

%

14820000

TEST OF NOV. 0, 1910 Boilers supplying Engine and A~~iliaries

Duration of te at 7 hours

Lbs. of coal 8320 1bs.

Lbs. of ash 1998 1bs.

Lbe. of water 51900 Ibs.

Barometer beginning 29.92tl

14.7 Ibs.

end 29.90"

Cost of coal $3.60 net ton

B.T.TI.

13600

Temp. of feed 48 .8~ C 119 .gO F

Pressure 119.74//= abs.

Temp. of steam 419.0oF

LOG, nOVe 9.

Temp.Steam Time Pres s .gage . Temp.feed HP. ..

of °C 400 9:00 105 48 287.3 400 9:30 106 47 290.4 402 10:00 103 47 283.0 398 10:30 104 49 282.8 405 11:00 108 62 29!").5 400 11:30 105 48 288.5 400 12:00 105 49 283.4 375 1:00 104 39 310.9 400 1:30 106 50 287.0 405 2:00 108 52 298.8 405 2:30 108 50 290.0 400 3:00 106 49 281.3 410 3:30 105 48 285.3 410 4:00 105 49 281.0 425 4:30 102 47 281.8 425 5:00 106 49 :.274.6 ) 6460' )168,,4 )783 )46-01'.-tf 403.8()F 105.4=!Igage 48.930 _{C 287.6 HP.}

corr.

419°F -.4 - • .J..., 105704 48 .8-3"DC 14.70 119.'74#abs

IS,

JS

PLAUTTEST,NOV.9 (continued) Boiler Pressure Temp. Temp.corr.to 119.7# 119.74 Ibs. 419 0 F 341.14 H

=

77.80 C superheat 877.0

t.

312.1 4 ~5(77.80)

=

122,8.0 B • T • IJ • 87.9 Total :B.T.U.

=

=

51,900 · 1140.1

=

532.. 000000

Equi'V. ETap. from and at 212 pe r lb. of coal

Thermal Eff.Boiler :Boiler H.F. 21_~q_~O.11~0.}('__ 9 69 •7 • 8, 3 v. 11!.~1_21 ,900 7 -33,320. 1140.1 • 51,900 8320 - 13, 600. 7.341bs. 253.5 BlIP. 52.25

%

PLMTT TEST, NOV. 9, (cont.).

= Total 1bs. of water_o

per hr.from and at 212 F

to be evap.for 287.6 HP.

1228 144 1084.

1084 • 51900 8300 Ibs. of water from and at 212°F

~. g69~~~)- - for 287.6 HP.

Assume 292 HP. as average load.

292

-2R? • 6 ...,. 1.015

1.015 • 8300

=

8430 Ibs. of water per hour fram and at 212cJ

F for 292 HP.

1bs. _o.!~~~~-Io'-~~.!~r

292.!ll'.

Lbs. of coal per hour - equ.L.\,.evap;_

= 8430

7.34

2/,

DISTRIBUTION OF LOAD Steam

No load but sha~ts (machines idle) 163.4 liP. Clutches throvm out,

Shafting

₌

Full load 6th floor off Full load 5th floor off Full load 4th floor off Full load 3rd floor off Full load 2nd floor off Full load 1st floor off

with gen. carr~ing 120 v 130 am~04.5 HP.

(= 26.9 HP) 104.5 - 26.9 lIP 78.4 B:P. 301.1 HP 204.1 97.0 HP 6th. 295.7 255.3 40.4 5th. 260.3 260.3

₄

7•3 4th,

291.7

290.1 1.6 3rd. 294.7 262.8- 31.9 2nd. 29-9-.8 284.6 15.2 1st 223.4 _BP. Electriaal

KY.

unco~ KH. cor~ RP cor~

1,2,3,floors 90 ~ installed 37.9 57.4 77. HP

4th floor '55 HP ~ 23.25 35.2 47.2

5th ft 90 1m ft 29.5 44.65 59.9

6th.ft _{145 HP}

ft 43. 68..18 8~T4

6th floor Motors indicated singly 85.25 114.3

Total 2~~F0V298.4 liP VI alone Motor 50 RP 50 25 20 Uncorrected 19.60 20,:90 4.59 6.10 51.19 KW • 77.5 ,J.(N corrected

=

103.9 HP

+

10

%

line losS

=

114.3 HP

22,

DISCUSSION OF LOP~ DISTRIBUTION

Wi th all the machines idle, when the onl~{ load on

the engine was the shafting, the IEF was 163.4

With the floor clutches thro~~ out w1d a load

on the generator of 130 amperes and 120 volts, the IHP

was 104.5, of which 26.1 was due to the generator,

aa-st~ing its efficiency to be equal to 80

%.

Thus the IRP required to drive the jack shaft,

or in other words the shafting and belting fram the

engine to the clutches on the various floors, is equal

to 104.5 - 26.1 ~ 78.4 HP.

The total RP delivered to the floors, a.ccording

to the data obtained by throwing out each floor in 8UC- .

cession, equals 223.4 HP. This addeR to the power

required to drive the jack shafts • 301.8 h~, which is

very near to the actual IHP of the engine when under full load.

The power requireu to drive the various floors

Electric less 57.8 HP 3°5.4 44.9 85.9 224.0 HP 15

'it.

10 ~ 20/0 Electric 77.0 F:P 47.2 59.9 114.3 298.4-about 85

%

eff. steam 48.7 EP 37.3 40.4 97.0 223.4 run at is as follows: 1,2,& 3 4 5 6 l'Iotor 10s6 Ylhen Line 10s8 Total loas

Thus it is evident that the input of power de-termined by the electrical measurements is consistent with that determined from the readings of the steam Horse Power required.

The electrica~ input was obtained from the Graph-ic Wattmeter trace b_J: noting a sufficient number of or-dinates, taken at equal intervals, for each curve.

On the twenty-five horse power motor curve the ordi-nates chosen were closer together than on the other curves which were more regular.

We feel justified in considering these readings as trul:y representative of the average day because the:y" show such a marked uniformity.

The foremen in the building all agreed that on the days of test the floors were all running under nor-mal load.

24

CALCULATI02T OF COST S OF STE.A];I PO}lTER'

Hours running

Plant is shut down 2 weeks for repairs

50 weeks ~ 5 days of 10 hrs

50 weeks 1 day bf 5 brs

6 holidays

Total working hours per year

2500. hra 250 ...

2750. 60. 269-0: Coal and Water used

Lbs of coal per year 2690xl150, • 3,090,000.

Assume 5.1bs of coal per BEl' per day

used for banking 5xl.015(253.5)(365.)

Banking coal - 2000. . -1545. tons 112.8 Total coal 199B Ash 8320 24 ~ Ash

=

24% of 1664

Lbs of water per year 51~OO 2690

1664. tQnJ'.

399.tons.

=

19,950,000 Ibs A~ount of water in 1000 gal per year

Operating Costs

Wa.ter per ~re ar @

$

.20 per 1000 gal 2,388 x .20

Oil and W'aste @ .033

i

per IRP hr

.033

i

(292)(2690)

Ash Removal @25

t

per ton

399 x $.25 . Coal per year .

1664 tons @ $3.60 per ton

2,388 M.gal,

$477.6 259.4

99.8

847.5 1695.0 339.0 108. 25.5 120. 4.5

--Investment Cost of steam Plant

2 Stirling Boilers, 400 EHP @$13 per BHP installed

Piping

Auxiliaries (feed pump and heater)

Engine,

Simple Non-condensing 20rt_x42rt _Rice

_&

Sargent Installed

Stack @2.25 per BHP

Total Value of Installation Fixed Charge6

Interest @5

%

on 16,950 Profit, 10

%

on 16,950

Insurance and Taxes, a.Bstwing 2

%

Amortization on Boiler, 1.5

J~

for 30 year life

n on Auxiliaries

3%

for 20 yrs.life

n rt Engine,

1.5%

for 30 yr.life rt n Stack, .5% for 50 yr life

Total 5200. 2000. 850. 8000. 900. --1 [)950. ~139.5 Ope rating Cost s

Coal, 1664 tons @3.60 per

ton

Water, 2,388,000 gal. @$.20 per M.gal. Oil and Waste, .033 per IEF hr

Repairs @ 2

%

of Investment 1 Engineer, 50 weeks @~18.00 1 Assistant Engineer @$15.00

1Fireman @$12.00

Cost~.of Ash removal @ $.25 per ton

Total Cost per year

5980. 477.6 259.4 339.0 900.0 750.0 600.0 99.8 9405.8 1~545 .3

CALCULATION OF COSTS OF ELECTRICAL INSTALLATION Investment Coat of Electric Installation

Motor @i450• 81350. fI @ 360. 720. " 0001.5 603. @ 277.2 831.6 @ 233.1 466.2 @ 201.6 201.6 @ 71.1 142.2 . 4314.6 . 431.5 -51'3883-.f If " 1-8--pole...Induction_, I 6 fonn K fI I I fonn L " I' .. !{ 71pole. rorrl1 C-Total Less 10

%

discount 3 50., HP_/ 900- RP1:tI _, 2 35 1200 II 2 25 II II 3 20 II II 2 15 ". tI 1 10 " II 2 5 1800 II

The cost of the motors quoted is the cost in-stalled, a.nd includes the starting compensators.

Wiring

Total coat of installation

200. ~4083.1

Fixed Charges _

Interest @ 5

%

on 4,083.1 Profit 10

%

on 4,083.1

Insurance and taxes, 2

%

on 4,083.1 Depreciation @ 10

%

on 4,083.1

(Depreciation includes repairs and

$204.2 408.3 81.7 408.3 ob sole Bcence )1102.5 Kwh.

=

2690

x

222.5

=

598,500 Kwh per year

Cost of power when supplied to Power House of Brown

&

Sharpe Mfg. Co. by Narragansett Electric

Lighting Co.

598,500 Kwh @

a

cents per Kwh 11970

Total cost of Operation of P100lt

27

DISCUSSIor OF ELECTRICflL COSTS

If the power is supplied to the Power House by the

Lighting Company, and from this supplied to the mill, the

increased cost incurred through the use of electric drive

over that of steam drive is the difference betweenI13,072.5

and/12,545.3, which is $527.2.

If' tlie power is supplied directly to the mill by the

Narragansett Electric Lighting Company, and the 10

%

line

loss in the cables from the Power House of the Bro\vn and

Sharpe Manufacturing C~pany is sUbtracted, the cost of

electric drive is as follows:

$11875.5 $119?0.

119?

107?3. 1102.5 Cost in first case

10

%

loss

Fixed Char«;es

Total coat of operation of the Plant e lectric all~r

Coat of steam Drive 12545.3

Cost of Electric DriTe 11875.5

DISCUSSION OF RESULTS

From the accompanying data it is seen that there is but a slight difference in the total cost of power in #4 Building whether the motive power be steam or electricity.

If the Brown and Sharpe Manufacturing Companj-, in bu:>ring power from the 1Tarragans~tt Electric Lighting Company,

dis-tributed the power from ~ sub-station on the site of their present new power plant, which, it may be added, they would

not be likely to dO, the cost of the electrical drive would exceed that of the steam drive bjr $52? .20 per year.

We note, howeTer, that the steam plant was running at a rather poor economy, as the engine efficiency was only 10.1

%.

A thorough overhauling would doubtless improve this efficiencyi The engine was overhauled before ~ts re-installation in the new power plant, and it was our inten-tion to detenmine its efficiency under the improved condi-tions of running, in order to credit to the steam drive the be st elficienc:'t~obtainable. As already noted, this second test was impossible, owing to the non-completion of the work of re-installing. Whatever gain may be made in operating economy by the overhauling and resetting of the engine will leave a still greater excess cost chargeable to the electric installation.

and #4 Euilding we assume that the Narragansett Electric Lighting Company is to suppl:y powe r directly to this and and every other building. This would undoubtedly be the means of distribution, with a transformer at each building

to bring dovm the 1600 volts of the transmission line to 230 volts for the motors. The cost of electrical energy under these conditions would then be less than that of

steam power by ...-;theamount of $669 '.80. It must be remem-bered in this connection that the saving due to electrical drive would be decreased by the increased efficiency of the ,engine above referred to.

We note here that no better boiler ~fficiency is considered obtainable, as the boilers were operating at the time of the test at an efficiency of 52.8

%,

the aver-age of the two days.

It VIas hoped, ,as previovs1jr stated, that the Central Power Plant would be completed in time for a determination of the cost to generate a kilowatt hour to be made, but un-fortunately such was not the case.

It is of interest to know what this coat must be in order that the cost of the electrical drive Shall equal, but not exceed, that of the former steam drive.

The total cost of steam operation was $12545.30 per

year. The electrical fixed charges a~mount to $1102.50

per year, leaving $12545.30 - 1102.50, or $11442.80,

able expendi t.urefor 598,500 kilo1;vatthours. This giTes a rate of $11442.80~ 598,500, or 1.91 cents per kilowatt hour.

That is, .if the Brovm and Sharpe l~anufacturing Com-pany can produce power in the new power house at a cost at

the switchboard of 1.91 cents per kilowatt hour, their power expenses for #4 Building will be the same as before, with the stea~ drive. If they can ~enerate at a lower

cost, the difference will be a pure gain in favor of the electrical installation.

A point where the electrical drive makes a saving over the steam is in the matter of floor space. The mo-tors are all on the ceiling, and therefore occup~rno

vC'.l-uable space. The removal of the eng~ne has made available

on one floor a space measuring 56ft x 24 ft. The founda-tions took up a space on the floor below the engine of apl" proximatel~" the same dimensions. The removal of boilers has made available a space measuring 60 ft x 75 ft. All

this space is very valuable for manufacturing purpuses, and

will 800n be occupied by machinery.

The bel tine; and pulleys sho\m in two blue prints made from Bro\m & Sharpe Compan~lts original drawings, had

two disadvantages. They occupied a box-like tube about seyan feet square, running from the bott~n to the top of

the building. This, as has been pointed out, is now

a-.91

vailabl~ for manufacturing purpose s. These belts and

pul-leys alse absorbed, on the day of the test, 78.4 horse

power, or in round numbers, 80 horse power, which

repre-sents about 27

%

of the steam engine indicated power •

.This belt 108S is not excessive compared with that existing

at some other mills and factories, but is still large.

It could have been decreased by the elimination of the idle

pulley's and the setting further apart of' the main pulley s,

a

to gain a suitable arc of belt contact, but this woule. hIe

taken up too much room.

The use of electric drive tends to increase the

continuity of service over that attained with steam drive.

In the latter case injury to the boilers or engine would

throw out of commission the entire motive power of the m111.

On the other hand, if the power is not supplied by one

u-nit, but by a number' of small units such as electric

mo-tors, an injury to one of the motors can affect only a

small portion of the plant. A serious interruption in

the supply of pO/fer from the central station is practically

unheard of, because of the fact that the nmlber of units

supplying the porrer is such that injury to one will affect

but slightl:~r the operation of the plant. In moat case s

taeaerl

employ.A

the ot.hersmay be used until the first is in condition a-gain.

Another advantage in the use of electricity is the decreased fire risk. The" el~1nation of the stack, boil-ers, and engine, also eliminates any danger from oil soaked waste, or hot ashes.

The electric system is much more flexible than steam. In case it is desired to operate an~ydepartment overtime it is necessaljr to ntn only the motors of that department. In case

or

steam drive an engine and fireman had to be on duty whenever any department was run overtime. This advantage was particularly noticeable in the case of the sixth floor, which is almost entirely occupied with automatic gear cutting machinery. This department' was very busy cutting gears for aut~obile8,

anu

was working overtime until ten. '.Vith steam drive it would be extreme-ly doubtful if it would be advisable to require the engin-eer to work from six o'clock in the morning to ten at night, or to hire a night engineer and a fireman. The engine would also be running at extremely low efficiency, and consequently the cost of operation wou.ld be excessiva, but with electric drive overtime work may be carried on at the same cost as for that done during the regular working hours.

SUM.EARY

If the cost per ~VH is two cents, electric has no appreciable advantage over steam drive in regard to cost, but it does have the ~ollowing markeu advantage5~

1) Eco~om:rof' floor space.

2) Elimination of shafts and belting to transmit power fram engine to various floors.

a) Removes a source of danger to employees. 3) Better continuity of service.

4) Decreased fire risks.

5) Greater flexibility of plant operation.

a) Overtime work.

Eng ine The rmom . Degrees F

CALIBRATION OF INSTRIDJffiNTS Calibration of Engine Thermometer.

standard

DegreesC Degrees

F

Degrees

C

Degrees

F

Up Down Up Down 375 375 201 394 193 379 380 380 205 401 195 383 385 385 208 406 200 392 390 390 211 412 204 399 395 395 213.5 416 206 403 400 400 215.8 420 209 408 406 405 21P. 424 213 416 410 410 221 430 216 421 415 415 224.5 436 220.5 429 420 -420 227 440 224 435 425 425 230 446 230 446 Calibration of Thenm~aeter ~7666 Toe Correction 29.0 -.1 64.7 -.3 133.0 -.1 161.7 t.2

Calibration 'of Gage #6932 Gage

st

and.Preas. 85 95 105 110 115 126 125 130 135 140 Up 85 94.7 105 109.5 115.0 119.8 125.0 129.0 135.0 140.0 Down 85 95 106 109 114.5 119.5 125 130 135 140 Corree tion

o

of.15 -.50 ".75 1.25 ".35

o

+~5

o

o

Calibration of Integrating Watt~eter #2135368 K

=

25 Kj. c.oils_in

I/;:

12.5. liultiply reading by 10 in Integrating

.Rev. Time }r'7. G.E • KW#159;)62 Watts I V P.f.

20 72.8 12:.36 12.30 205x60 3.025x30 ~~24 .61 20 62.8 14.32 14.40 240 3.2 :221 .68 20 65.0 13.85 13.20 220 3.1 , .228 .64 20 66.8 13.4:8 13.26 221 3.11 281 .64 20 75.2 11.97 11.70 195 3.15 222 .56 20 73.0 12.17 11."79 196.5 3.18 223.5.55 20 86.8 10.37 9.84 164 3.05 222.5.48 15 56.8 11.88 11.64 194 3.08 222 .57 15 56.8 11.88 11.76 196 3.1 222 .57 20 i-15. ~ 20.0 20.10 335 3.0 222 .99 20 44 20.45 20.10 335 3.0 222 .99 20 43.4 20.73 20.70 345 3.08 222 .99 W

=

-~fI---3600 x 25 Rev

Wattmeter was calibrated as a single phase meter with

the potential coils in parallel and the currant coils in

series.

Single phase Wattmeter #159,362 Reading x 60

Ammete r #76,986 30 x reading Vol tmat.e r #3,770

3:1 Current Transformer #454,802

Wattmeter #159,362 was tested by Standardizing

De-partment of the Massachusetts Institute of Technology, and

showed an error of less than one-half of one percent, 1.e.,

.4 watts in 127 watts, largest error.

Calibration of Graphic Wattmeter 3 hour run Integrating wattmeter #2135368 Reading at 12 Readinr: at 9' ~1Jlrs.: Graphic Wattmeter 00157 00062 3)-9-5- KN ---3T.66 K'.vh 20.9 Correction

= -_.-

31.66 20.9

=

1.513

-a.<~ .

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