Modern Machine-Shop Practice Part 228

Another arrangement is shown in Fig. 3277, the tubes being _staggered_ or arranged zigzag. This permits of the employment of a greater number of tubes, but does not afford such free circulation of the water.

Fig. 3278 represents an arrangement where the tubes are in rows both vertically and horizontally.

Fig. 3279 represents a boiler by the Erie Iron Works, the details of the setting being as follows:

[Ill.u.s.tration: Fig. 3274.]

[Ill.u.s.tration: Fig. 3275.]

[Ill.u.s.tration: Fig. 3276.]

[Ill.u.s.tration: Fig. 3277.]

[Ill.u.s.tration: Fig. 3278.]

[Ill.u.s.tration: Fig. 3279.]

[Ill.u.s.tration: Fig. 3280.]

[Ill.u.s.tration: Fig. 3281.]

Fig. 3280 is an end view of the setting with the brickwork in section.

Fig. 3281 side view of the boiler and setting.

[Ill.u.s.tration: Fig. 3282.]

[Ill.u.s.tration: Fig. 3283.]

Fig. 3282 a front end view of the boiler, and Fig. 3283 a ground plan of the brickwork. When the front plate of the boiler setting extends above the middle of the boiler, as in Fig. 3279, it is said to have a "full arch front." Whereas when this plate or casting extends to the middle only of the boiler, it is said to have a half arch front.

[Ill.u.s.tration: Figs. 3284, 3285, 3286, 3287.]

Figs. 3284, 3285, 3286, and 3287 show the setting for a half arch front boiler, the dimensions of the settings of both these boilers being given in the following tables:

MEASUREMENTS FOR SETTING TUBULAR STATIONARY BOILERS WITH FULL ARCH FRONTS.

REFERENCE LETTERS ON DIAGRAMS.

------+---+----+----+----+----+----+------+----+----+----+----+---- No. | A | B | C | D | E | F | G | H | I | J | K | L ------+---+----+----+----+----+----+------+----+----+----+----+---- |Ft.|Ins.|Ins.|Ins.|Ins.|Ins.| Ins. |Ins.|Ins.|Ins.|Ins.|Ins.

1 | 7| 32 | 12 | 20 | 16 | 45 |44 | 7 | 32 | 64 | 85 | 26 2 | 7| 34 | 12 | 20 | 16 | 48 |47 | 8 | 34 | 66 | 90 | 26 3 | 8| 36 | 12 | 20 | 16 | 48 |47 | 8 | 36 | 68 | 92 | 26 3-1/2| 10| 36 | 12 | 20 | 16 | 48 |47 | 8 | 36 | 68 | 92 | 26 4 | 8| 42 | 14 | 20 | 16 | 48 |47 | 8 | 42 | 74 | 98 | 27 5 | 10| 42 | 14 | 20 | 16 | 48 |47 | 8 | 42 | 74 | 98 | 27 6 | 10| 44 | 14 | 24 | 16 | 48 |47 | 10 | 44 | 76 |100 | 27 7 | 12| 44 | 14 | 24 | 16 | 48 |46-1/2| 10 | 44 | 76 |100 | 27 7-1/2| 14| 44 | 14 | 24 | 16 | 47 |45-1/2| 10 | 44 | 76 | 99 | 26 8 | 12| 48 | 16 | 24 | 16 | 47 |45-1/2| 10 | 48 | 88 |103 | 26 9 | 14| 48 | 16 | 24 | 16 | 47 |45-1/2| 10 | 48 | 88 |103 | 26 10 | 12| 54 | 16 | 24 | 20 | 50 |48-1/2| 10 | 54 | 94 |112 | 26 10-1/2| 15| 54 | 16 | 24 | 20 | 50 |48-1/2| 10 | 54 | 94 |112 | 26 11 | 12| 60 | 18 | 24 | 20 | 50 |48-1/2| 12 | 60 |108 |118 | 26 12 | 14| 60 | 18 | 24 | 20 | 50 |48-1/2| 12 | 60 |108 |118 | 26 13 | 16| 60 | 18 | 26 | 20 | 50 |48 | 12 | 60 |108 |118 | 26 14 | 15| 66 | 18 | 28 | 20 | 50 |48-1/2| 12 | 66 |114 |124 | 26 15 | 16| 66 | 18 | 28 | 20 | 50 |48 | 12 | 66 |114 |124 | 26 16 | 16| 72 | 20 | 30 | 20 | 50 |48 | 12 | 72 |120 |130 | 26 ------+---+----+----+----+----+----+------+----+----+----+----+----

------+----+-------+----+----+----+----+----+----+----+------+------ | | | | | | | | | | | NO.

| | | | | | | | | | |COMMON | | | | | | | | | | |BRICK | | | | | | | | | |NO. OF|ABOVE No. | M | N | O | P | Q | R | S | T | U | FIRE |FLOOR | | | | | | | | | |BRICK.|LEVEL.

------+----+-------+----+----+----+----+----+----+----+------+------ |Ins.|Ft.Ins.|Ins.|Ins.|Ins.|Ins.|Ins.|Ins.|Ins.| | 1 | 19 | 11-6 | 20 | 40 | 12 | 16 | 36 | 34 | 4 | 600 | 6800 2 | 22 | 11-6 | 20 | 40 | 12 | 16 | 36 | 34 | 4 | 600 | 7500 3 | 22 | 12-6 | 24 | 40 | 12 | 16 | 36 | 34 | 4 | 650 | 7700 3-1/2| 22 | 14-6 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 720 | 8500 4 | 21 | 12-8 | 24 | 40 | 12 | 16 | 36 | 34 | 4 | 730 | 8500 5 | 21 | 14-8 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 770 | 9600 6 | 21 | 15-0 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 880 | 10500 7 | 21 | 17-0 | 32 | 52 | 12 | 16 | 48 | 49 | 4 | 940 | 10800 7-1/2| 21 | 19-0 | 36 | 58 | 12 | 16 | 54 | 84 | 4 | 1120 | 11500 8 | 21 | 17-2 | 32 | 52 | 12 | 20 | 48 | 49 | 4 | 1120 | 13600 9 | 21 | 19-2 | 36 | 58 | 12 | 20 | 54 | 84 | 4 | 1140 | 15700 10 | 24 | 17-6 | 32 | 52 | 12 | 20 | 48 | 49 | 4 | 1160 | 16200 10-1/2| 24 | 20-8 | 36 | 56 | 16 | 20 | 54 | 90 | 4 | 1270 | 17500 11 | 24 | 17-10 | 32 | 50 | 16 | 24 | 48 | 49 | 4 | 1400 | 20500 12 | 24 | 19-10 | 36 | 56 | 16 | 24 | 54 | 84 | 4 | 1500 | 23000 13 | 24 | 22-0 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1540 | 25300 14 | 24 | 21-2 | 36 | 56 | 16 | 24 | 54 | 90 | 4 | 1590 | 26000 15 | 24 | 22-2 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1620 | 27000 16 | 24 | 22-6 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1750 | 30000 ------+----+-------+----+----+----+----+----+----+----+------+------

NOTE.--In setting "Standard" boilers, the side walls should be so built that the longitudinal seams of the sh.e.l.l will be protected from the fire.

MEASUREMENTS FOR SETTING TUBULAR STATIONARY BOILERS WITH HALF ARCH FRONTS.

REFERENCE LETTERS ON DIAGRAMS.

------+---+----+----+----+----+------+------+----+----+----+------- No. | A | B | C | D | E | F | G | H | I | J | K ------+---+----+----+----+----+------+------+----+----+----+------- |Ft.|Ins.|Ins.|Ins.|Ins.|Ins. | Ins. |Ins.|Ins.|Ins.| Ins.

1 | 7 | 32 | 14 | 20 | 16 |46 |45 | 7 | 32 | 64 | 73 2 | 7 | 34 | 14 | 20 | 16 |46 |45 | 8 | 34 | 66 | 75 3 | 8 | 36 | 14 | 20 | 16 |46 |45 | 8 | 36 | 68 | 77 3-1/2|10 | 36 | 14 | 20 | 16 |46 |45 | 8 | 36 | 68 | 77 4 | 8 | 42 | 18 | 20 | 16 |46 |45 | 8 | 42 | 74 | 83 5 |10 | 42 | 18 | 20 | 16 |46 |45 | 8 | 42 | 74 | 83 6 |10 | 44 | 18 | 24 | 16 |46 |45 | 10 | 44 | 76 | 85 7 |12 | 44 | 18 | 24 | 16 |46 |44-1/2| 10 | 44 | 76 | 85 7-1/2|14 | 44 | 18 | 24 | 16 |46 |44-1/2| 10 | 44 | 76 | 85 8 |12 | 48 | 19 | 24 | 16 |50 |48-1/2| 10 | 48 | 88 | 93 9 |14 | 48 | 19 | 24 | 16 |50 |48-1/2| 10 | 48 | 88 | 93 10 |12 | 54 | 19 | 24 | 20 |50 |48-1/2| 10 | 54 | 94 | 99 10-1/2|15 | 54 | 19 | 24 | 20 |50 |48-1/2| 10 | 54 | 94 | 99 11 |12 | 60 | 21 | 24 | 20 |46-3/4|45-1/2| 12 | 60 |108 |101-3/4 12 |14 | 60 | 21 | 24 | 20 |46-3/4|45 | 12 | 60 |108 |101-3/4 13 |16 | 60 | 21 | 26 | 20 |46-3/4|45 | 12 | 60 |108 |101-3/4 14 |15 | 66 | 24 | 28 | 20 |47 |45-1/2| 12 | 66 |114 |108 15 |16 | 66 | 24 | 28 | 20 |47 |45-1/2| 12 | 66 |114 |108 16 |16 | 72 | 24 | 30 | 20 |48 |46-1/2| 12 | 72 |120 |115 ------+---+----+----+----+----+------+------+----+----+----+-------

------+------+------+--------+----+------+----+----+----+----+---- No. | L | M | N | O | P | Q | R | S | T | U ------+------+------+--------+----+------+----+----+----+----+---- | Ins. | Ins. |Ft. Ins.|Ins.| Ins. |Ins.|Ins.|Ins.|Ins.|Ins.

1 |26 |20 | 10-3 | 20 |33 | 12 | 16 | 36 | 34 | 4 2 |26 |20 | 10-3 | 20 |33 | 12 | 16 | 36 | 34 | 4 3 |26 |20 | 11-3 | 24 |33 | 12 | 16 | 36 | 34 | 4 3-1/2|26 |20 | 13-3 | 28 |39 | 12 | 16 | 42 | 42 | 4 4 |27 |19 | 11-3 | 24 |32-1/2| 12 | 16 | 36 | 34 | 4 5 |27 |19 | 13-3 | 28 |38-1/2| 12 | 16 | 42 | 42 | 4 6 |27 |19 | 13-7 | 28 |38-1/2| 12 | 16 | 42 | 42 | 4 7 |27 |19 | 15-7 | 32 |44-1/2| 12 | 16 | 48 | 49 | 4 7-1/2|27 |19 | 17-7 | 36 |50-1/2| 12 | 16 | 54 | 84 | 4 8 |26 |24 | 15-7 | 32 |48 | 12 | 20 | 48 | 49 | 4 9 |26 |24 | 17-7 | 36 |54 | 12 | 20 | 54 | 84 | 4 10 |26 |24 | 15-11 | 32 |48-1/2| 12 | 20 | 48 | 49 | 4 10-1/2|26 |24 | 19-1 | 36 |52-1/2| 16 | 20 | 54 | 90 | 4 11 |26 |20-3/4| 16-1 | 32 |47 | 16 | 24 | 48 | 49 | 4 12 |26 |20-3/4| 18-1 | 36 |53 | 16 | 24 | 54 | 84 | 4 13 |26 |20-3/4| 20-3 | 40 |53 | 16 | 24 | 54 | 96 | 4 14 |26 |21 | 19-5 | 36 |52-1/2| 16 | 24 | 54 | 90 | 4 15 |26 |21 | 20-5 | 40 |52-1/2| 16 | 24 | 54 | 96 | 4 16 |28-1/4|19-3/4| 20-7 | 40 |52-1/2| 16 | 24 | 54 | 96 | 4 ------+------+------+--------+----+------+----+----+----+----+----

------+------+------+----+----+----+------+------ | | | | | | | NO.

| | | | | | |COMMON | | | | | | |BRICK | | | | | |NO. OF|ABOVE No. | V | W | X | Y | Z | FIRE |FLOOR | | | | | |BRICK.|LEVEL.

------+------+------+----+----+----+------+------ | Ins. | Ins. |Ins.|Ins.|Ins.| | 1 |36 | 9 | 24 | 12 | 7 | 600 | 6150 2 |36 | 9 | 28 | 12 | 7 | 600 | 6200 3 |36 | 9 | 28 | 12 | 15 | 650 | 6700 3-1/2|36 | 9 | 28 | 12 | 25 | 720 | 7050 4 |32-3/4|12-1/4| 32 | 16 | 11 | 730 | 7700 5 |32-3/4|12-1/4| 32 | 16 | 25 | 770 | 8700 6 |32-3/4|12-1/4| 36 | 16 | 25 | 880 | 8800 7 |32-1/4|12-1/4| 36 | 20 | 35 | 940 | 9300 7-1/2|32-1/4|12-1/4| 36 | 24 | 45 | 1120 | 9500 8 |36-1/4|12-1/4| 36 | 20 | 35 | 1120 | 11100 9 |36-1/4|12-1/4| 36 | 24 | 45 | 1140 | 12900 10 |34 |14-1/2| 42 | 20 | 35 | 1160 | 13200 10-1/2|34 |14-1/2| 42 | 24 | 57 | 1270 | 14200 11 |31 |14-1/2| 48 | 20 | 37 | 1400 | 16700 12 |30-1/2|14-1/2| 48 | 24 | 45 | 1500 | 19200 13 |30-1/2|14-1/2| 48 | 24 | 65 | 1540 | 21500 14 |31 |14-1/2| 54 | 24 | 57 | 1590 | 22100 15 |31 |14-1/2| 54 | 24 | 65 | 1620 | 23100 16 |27-1/2|19 | 54 | 24 | 65 | 1750 | 26000 ------+------+------+----+----+----+------+------

NOTE.--In setting "Standard" boilers, the side walls should be so built that the longitudinal seams of the sh.e.l.l will be protected from the fire.

THE EVAPORATIVE EFFICIENCIES OF BOILERS.

[56]"Many tests have been undertaken to ascertain the evaporative power of different cla.s.ses of boilers in actual work; but few of these are of any value, owing to the unreliable means usually employed to measure the quant.i.ty of water evaporated. The easiest method, and consequently the one most frequently adopted, is to measure the quant.i.ty by the difference of its height in the water-gauge gla.s.s at the beginning and end of the trial, and also at intermediate stages. This method is very rude and uncertain, since there can be little doubt that in many boilers at work the surface of the water is not level, but is usually higher over the furnace, or where the greatest ebullition occurs. The difference in height at any moment will greatly depend upon the intensity of the ebullition, which is ever varying during the intervals between firing. With mechanical firing the difference of height is probably reduced to a minimum.

[56] From "_A Treatise on Steam Boilers_," by Robert Wilson.

"The meters employed for measuring the water are sometimes not trustworthy. The only sure method of ascertaining the quant.i.ty of water evaporated is by actual measurement with a cistern or vessel whose cubic contents are accurately known. The quant.i.ty of water in the boiler before and after the trial should be measured at the same temperature, which should not exceed 212 to insure accuracy. But even when the amount of water introduced and the quant.i.ty pa.s.sed off from the boiler are accurately ascertained, there yet remains a doubt as to how much has been actually evaporated, and how much may have pa.s.sed off in priming, unless the trial has been conducted with the boiler open to the atmosphere, which appears to be the only condition under which accuracy can be insured, unless a suitable apparatus can be provided for accurately measuring the weight and temperature of all the steam and water given off, when the boiler is working above atmospheric pressure.

"There are very few boilers that do not prime more or less, and the quant.i.ty of water pa.s.sed off in this manner is sometimes very considerable, and has led to the impossible results of 16 and 17 lbs. of water evaporated per lb. of ordinary coal in locomotive and water-tube boilers being seriously recorded. Externally fired boilers, that have given the moderate result of 5 lbs. of water per lb. of coal at atmospheric pressure, have shown the unexpected result of 10 and 12 lbs.

of water evaporated at 40 lbs. pressure. In fact, unless the amount of water pa.s.sed over with the steam by priming or foaming, when working under pressure, can be accurately ascertained, the evaporative results are not to be relied upon, however careful in other respects the trial may have been conducted. It is customary to give the quant.i.ty of water evaporated from and at a temperature of 212, or the boiling point at atmospheric pressure, to which the results of evaporation are reduced."

The quant.i.ty corresponding to any temperature of feed water and working pressure can readily be found with the aid of the annexed table, taken from _The Encyclopaedia Britannica_, wherein are presented the relations of the properties of steam, as now accepted by the best authorities.

TABLE GIVING THE PRESSURE, TEMPERATURE, AND VOLUME OF STEAM.

-----------+-----------+-----------+----------+---------+------------- Total pres-| | | | |Relative vol- sure per |Gauge pres-| Sensible |Total heat|Weight of| ume of steam square inch| sure or |temperature|in degrees|one cubic|compared with measured | pressure | in |from zero |foot of | the water from a | above | Fahrenheit| of | steam. |from which it vacuum. |atmosphere.| degrees. | Fahren- | lbs. | was lbs. | lbs. | | heit. | | evaporated.

-----------+-----------+-----------+----------+---------+------------- 1 | --- | 102.1 | 1144.5 | .0030 | 20582 2 | --- | 126.3 | 1151.7 | .0058 | 10721 3 | --- | 141.6 | 1156.6 | .0085 | 7322 4 | --- | 153.1 | 1160.1 | .0112 | 5583 5 | --- | 162.3 | 1162.9 | .0138 | 4527 6 | --- | 170.2 | 1165.3 | .0163 | 3813 7 | --- | 176.9 | 1167.3 | .0189 | 3298 8 | --- | 182.9 | 1169.2 | .0214 | 2909 9 | --- | 188.3 | 1170.8 | .0239 | 2604 10 | --- | 193.3 | 1172.3 | .0264 | 2358 11 | --- | 197.8 | 1173.7 | .0289 | 2157 12 | --- | 202.0 | 1175.0 | .0314 | 1986 13 | --- | 205.9 | 1176.2 | .0338 | 1842 14 | --- | 209.6 | 1177.3 | .0362 | 1720 14.7 | 0 | 212.0 | 1178.1 | .0380 | 1642 15 | .3 | 213.1 | 1178.4 | .0387 | 1610 16 | 1.3 | 216.3 | 1179.4 | .0411 | 1515 17 | 2.3 | 219.6 | 1180.3 | .0435 | 1431 18 | 3.3 | 222.4 | 1181.2 | .0459 | 1357 19 | 4.3 | 225.3 | 1182.1 | .0483 | 1290 20 | 5.3 | 228.0 | 1182.9 | .0507 | 1229 21 | 6.3 | 230.6 | 1183.7 | .0531 | 1174 22 | 7.3 | 233.1 | 1184.5 | .0555 | 1123 23 | 8.3 | 235.3 | 1185.2 | .0580 | 1075 24 | 9.3 | 237.8 | 1185.9 | .0601 | 1036 25 | 10.3 | 240.1 | 1186.6 | .0625 | 996 26 | 11.3 | 242.3 | 1187.3 | .0650 | 958 27 | 12.3 | 244.4 | 1187.8 | .0673 | 926 28 | 13.3 | 246.4 | 1188.4 | .0696 | 895 29 | 14.3 | 248.4 | 1189.1 | .0719 | 866 30 | 15.3 | 250.4 | 1189.8 | .0743 | 838 31 | 16.3 | 252.2 | 1190.4 | .0766 | 813 32 | 17.3 | 254.1 | 1190.9 | .0779 | 789 33 | 18.3 | 255.9 | 1191.5 | .0812 | 767 34 | 19.3 | 257.6 | 1192.0 | .0835 | 746 35 | 20.3 | 259.3 | 1192.5 | .0858 | 726 36 | 21.3 | 260.9 | 1193.0 | .0881 | 707 37 | 22.3 | 262.6 | 1193.5 | .0905 | 688 38 | 23.3 | 264.2 | 1194.0 | .0929 | 671 39 | 24.3 | 265.8 | 1194.5 | .0952 | 655 40 | 25.3 | 267.3 | 1194.9 | .0974 | 640 41 | 26.3 | 268.7 | 1195.4 | .0996 | 625 42 | 27.3 | 270.2 | 1195.8 | .1020 | 611 43 | 28.3 | 271.6 | 1196.2 | .1042 | 598 44 | 29.3 | 273.0 | 1196.6 | .1065 | 595 45 | 30.3 | 274.4 | 1197.1 | .1089 | 572 46 | 31.3 | 275.8 | 1197.5 | .1111 | 561 47 | 32.3 | 277.1 | 1197.9 | .1133 | 550 48 | 33.3 | 278.4 | 1198.3 | .1156 | 539 49 | 34.3 | 279.7 | 1198.7 | .1179 | 529 50 | 35.3 | 281.0 | 1199.1 | .1202 | 518 51 | 36.3 | 282.3 | 1199.5 | .1224 | 509 52 | 37.3 | 283.5 | 1199.9 | .1246 | 500 53 | 38.3 | 284.7 | 1200.3 | .1269 | 491 54 | 39.3 | 285.9 | 1200.6 | .1291 | 482 55 | 40.3 | 287.1 | 1201.0 | .1314 | 474 56 | 41.3 | 288.2 | 1201.3 | .1336 | 466 57 | 42.3 | 289.3 | 1201.7 | .1364 | 458 58 | 43.3 | 290.4 | 1202.0 | .1380 | 451 59 | 44.3 | 291.6 | 1202.4 | .1403 | 444 60 | 45.3 | 292.7 | 1202.7 | .1425 | 437 61 | 46.3 | 293.8 | 1203.1 | .1447 | 403 62 | 47.3 | 294.8 | 1203.4 | .1469 | 424 63 | 48.3 | 295.9 | 1203.7 | .1493 | 417 64 | 49.3 | 296.9 | 1204.0 | .1516 | 411 65 | 50.3 | 298.0 | 1204.3 | .1538 | 405 66 | 51.3 | 299.0 | 1204.6 | .1560 | 399 67 | 52.3 | 300.0 | 1204.9 | .1583 | 393 68 | 53.3 | 300.9 | 1205.2 | .1605 | 388 69 | 54.3 | 301.9 | 1205.5 | .1627 | 383 70 | 55.3 | 302.9 | 1205.8 | .1648 | 378 71 | 56.3 | 303.9 | 1206.1 | .1670 | 373 72 | 57.3 | 304.8 | 1206.3 | .1692 | 368 73 | 58.3 | 305.7 | 1206.6 | .1714 | 363 74 | 59.3 | 306.6 | 1206.9 | .1736 | 359 75 | 60.3 | 307.5 | 1207.2 | .1759 | 353 76 | 61.3 | 308.4 | 1207.4 | .1782 | 349 77 | 62.3 | 309.3 | 1207.7 | .1804 | 345 78 | 63.3 | 310.2 | 1208.0 | .1826 | 341 79 | 64.3 | 311.1 | 1208.3 | .1848 | 337 80 | 65.3 | 312.0 | 1208.5 | .1869 | 333 81 | 66.3 | 312.8 | 1208.8 | .1891 | 329 82 | 67.3 | 313.6 | 1209.1 | .1913 | 325 83 | 68.3 | 314.5 | 1209.4 | .1935 | 321 84 | 69.3 | 315.3 | 1209.6 | .1957 | 318 85 | 70.3 | 316.1 | 1209.9 | .1980 | 314 86 | 71.3 | 316.9 | 1210.1 | .2002 | 311 87 | 72.3 | 317.8 | 1210.4 | .2024 | 308 88 | 73.3 | 318.6 | 1210.6 | .2044 | 305 89 | 74.3 | 319.4 | 1210.9 | .2067 | 301 90 | 75.3 | 320.2 | 1211.1 | .2089 | 298 91 | 76.3 | 321.0 | 1211.3 | .2111 | 295 92 | 77.3 | 321.7 | 1211.5 | .2133 | 292 93 | 78.3 | 322.5 | 1211.8 | .2155 | 289 94 | 79.3 | 323.3 | 1212.0 | .2176 | 286 95 | 80.3 | 324.1 | 1212.3 | .2198 | 283 96 | 81.3 | 324.8 | 1212.5 | .2219 | 281 97 | 82.3 | 325.6 | 1212.8 | .2241 | 278 98 | 83.3 | 326.3 | 1213.0 | .2263 | 275 99 | 84.3 | 327.1 | 1213.2 | .2285 | 272 100 | 85.3 | 327.9 | 1213.4 | .2307 | 270 101 | 86.3 | 328.5 | 1213.6 | .2329 | 267 102 | 87.3 | 329.1 | 1213.8 | .2351 | 265 103 | 88.3 | 329.9 | 1214.0 | .2373 | 262 104 | 89.3 | 330.6 | 1214.2 | .2393 | 260 105 | 90.3 | 331.3 | 1214.4 | .2414 | 257 106 | 91.3 | 331.9 | 1214.6 | .2435 | 255 107 | 92.3 | 332.6 | 1214.8 | .2456 | 253 108 | 93.3 | 333.3 | 1215.0 | .2477 | 251 109 | 94.3 | 334.0 | 1215.3 | .2499 | 249 110 | 95.3 | 334.6 | 1215.5 | .2521 | 247 111 | 96.3 | 335.3 | 1215.7 | .2543 | 245 112 | 97.3 | 336.0 | 1215.9 | .2564 | 243 113 | 98.3 | 336.7 | 1216.1 | .2586 | 241 114 | 99.3 | 337.4 | 1216.3 | .2607 | 239 115 | 100.3 | 338.0 | 1216.5 | .2628 | 237 116 | 101.3 | 338.6 | 1216.7 | .2649 | 235 117 | 102.3 | 339.3 | 1216.9 | .2674 | 233 118 | 103.3 | 339.9 | 1217.1 | .2696 | 231 119 | 104.3 | 340.5 | 1217.3 | .2738 | 229 120 | 105.3 | 341.1 | 1217.4 | .2759 | 227 121 | 106.3 | 341.8 | 1217.6 | .2780 | 225 122 | 107.3 | 342.4 | 1217.8 | .2801 | 224 123 | 108.3 | 343.0 | 1218.0 | .2822 | 222 124 | 109.3 | 343.6 | 1218.2 | .2845 | 221 125 | 110.3 | 344.2 | 1218.4 | .2867 | 219 126 | 111.3 | 344.8 | 1218.6 | .2889 | 217 127 | 112.3 | 345.4 | 1218.8 | .2911 | 215 128 | 113.3 | 346.0 | 1218.9 | .2933 | 214 129 | 114.3 | 346.6 | 1219.1 | .2955 | 212 130 | 115.3 | 347.2 | 1219.3 | .2977 | 211 131 | 116.3 | 347.8 | 1219.5 | .2999 | 209 132 | 117.3 | 348.3 | 1219.6 | .3020 | 208 133 | 118.3 | 348.9 | 1219.8 | .3040 | 206 134 | 119.3 | 349.5 | 1220.0 | .3060 | 205 135 | 120.3 | 350.1 | 1220.2 | .3080 | 203 136 | 121.3 | 350.6 | 1220.3 | .3101 | 202 137 | 122.3 | 351.2 | 1220.5 | .3121 | 200 138 | 123.3 | 351.8 | 1220.7 | .3142 | 199 139 | 124.3 | 352.4 | 1220.9 | .3162 | 198 140 | 125.3 | 352.9 | 1221.0 | .3184 | 197 141 | 126.3 | 353.5 | 1221.2 | .3206 | 195 142 | 127.3 | 354.0 | 1221.4 | .3228 | 194 143 | 128.3 | 354.5 | 1221.6 | .3250 | 193 144 | 129.3 | 355.0 | 1221.7 | .3273 | 192 145 | 130.3 | 355.6 | 1221.9 | .3294 | 190 146 | 131.3 | 356.1 | 1222.0 | .3315 | 189 147 | 132.3 | 356.7 | 1222.2 | .3336 | 188 148 | 133.3 | 357.2 | 1222.3 | .3357 | 187 149 | 134.3 | 357.8 | 1222.5 | .3377 | 186 150 | 135.3 | 358.3 | 1222.7 | .3397 | 184 155 | 140.3 | 361.0 | 1223.5 | .3500 | 179 160 | 145.3 | 363.4 | 1224.2 | .3607 | 174 165 | 150.3 | 366.0 | 1224.9 | .3714 | 169 170 | 155.3 | 368.2 | 1225.7 | .3821 | 164 175 | 160.3 | 370.8 | 1226.4 | .3928 | 159 180 | 165.3 | 372.9 | 1227.1 | .4035 | 155 185 | 170.3 | 375.3 | 1227.8 | .4142 | 151 190 | 175.3 | 377.5 | 1228.5 | .4250 | 148 195 | 180.3 | 379.7 | 1229.2 | .4357 | 144 200 | 185.3 | 381.7 | 1229.8 | .4464 | 141 210 | 195.3 | 386.0 | 1231.1 | .4668 | 135 220 | 205.3 | 389.9 | 1232.3 | .4872 | 129 230 | 215.3 | 393.8 | 1233.5 | .5072 | 123 240 | 225.3 | 397.5 | 1234.6 | .5270 | 119 250 | 235.3 | 401.1 | 1235.7 | .5471 | 114 260 | 245.3 | 404.5 | 1236.8 | .5670 | 110 270 | 255.3 | 407.9 | 1237.8 | .5871 | 106 280 | 265.3 | 411.2 | 1238.8 | .6070 | 102 290 | 275.3 | 414.4 | 1239.8 | .6268 | 99 300 | 285.3 | 417.5 | 1240.7 | .6469 | 96 -----------+-----------+-----------+----------+---------+-------------

Here we see that at 212 the total quant.i.ty of heat in the steam is 1178.1, which gives a difference of 966.1. This heat, usually termed latent, is absorbed in performing the work of expanding the particles of water from the liquid to the gaseous state. Now, suppose the water is evaporated at 60 lbs. pressure, the steam will have a temperature of 307, and a total heat of 1207. If the feed has been introduced at 60, it is evident that 1147 of heat have been imparted. As the amount evaporated is inversely proportional to the quant.i.ty of heat required, we have 1147 966 = 1.2. Multiplying by this factor, the quant.i.ty evaporated at 60 lbs. pressure from 60, we obtain the amount that would be evaporated at 212 by the same quant.i.ty of fuel.

By the same table can be ascertained the comparatively small increase of heat required to evaporate water at higher pressures. Suppose we take water evaporated at 45 lbs. pressure from a feed temperature of 60, then each lb. of water will require 1202.7-60 = 1142.7 for its conversion into steam. If we take the pressure at 100 lbs., we shall have 1216.9-60 = 1156.9 as the quant.i.ty required. The difference between these two total quant.i.ties is only 14.2, and is so small as to be scarcely worth considering. Leaving out of account the loss due to the slight reduction of the conducting power of the material, the increased amount of heat required for the higher pressure will be only 1/36 of the total heat required at 60 lbs. With an evaporation of 7 lbs.

of water from 1 lb. of coal, it will be obtained by using 1/563 more fuel, or about 1 lb. in about 556 lbs., a quant.i.ty not appreciable to the ordinary modes of weighing coal. The economy is then manifest of using steam of high pressures when at the same time advantage is taken of the facilities it offers for working the steam more expansively to the engine cylinders.

The saving that may be effected by heating the feed water may be shown as follows:

If we take the normal temperature of the feed water at 60, the temperature of the heated water at 212, and the boiler pressure at 20 lbs., the total heat imparted to the steam in one case is

1192.5 - 60 = 1132.5 and in the other case 1192.5 - 212 = 980.5 152 the difference being 152, or a saving of ------- 1132.5

which is 13.4 per cent. If the pressure be taken at 120 lbs., instead of 20 lbs., the saving will be 13.1 per cent, showing a slight diminution in the economy effected by heating the feed water when a high boiler pressure is employed.

THE CARE AND MANAGEMENT OF STATIONARY ENGINE BOILERS.