The theoretical economy of using steam expansively is as follows - a like volume of steam being expended in each case, and expanded to fill the increased spaces.

Point

Of Cutting

Off.

Expansion Number.

Mean

Pressure of Steam

Gain per cent in Power

•1

10.

3.302

230.

•125

8.

3.079

208.

•166

6.

2.791

179.

•2

6.

2.609

161.

•26

4.

2.386

139.

•8

3.33

2.208

120.

.333

3.

2.099

110.

•376

2.66

1.978

97.8

•4

2.5

1.916

91.6

Point of Cutting Of.

Expansion Number

Mean

Pressure of Steam.

Gain per Cent.

in Power.

6

2.

1.693

69.3

•0

1.66

1.507

50.7

•626

1.6

1.47

47.

.666

1.6

1.405

40.5

•7

1.42

1.351

861

•75

1.33

1.285

22.3

•8

1.26

1.228

20.5

•876

1148

1181

181

•9

1.11

1104

10.4

In this illustration, no deductions are made for a reduction of the temperature of the steam while expanding or for loss by back pressure.

The same relative advantage follows in expansion as above given, whatever may be the initial pressure of the steam.