STATIONARY ENGINES.

3 ”

of one-half of the travel of the steam piston. To find its cubicalcontents, divide the cubical contents of the steam cylinder by 4-3.When the stroke of the pump equals one-half that of the steampiston, to find the diameter of the pump, in usual cases, multiplythe diameter of the cylinder by 7. The cubical contents of thecondenser should be about twice the capacity of the air-pump.

Cold-water pump and injection water. —To determine the size ofthe cold-water pump we must first ascertain the quantity of waterrequired for condensation. This is found by multiplying the tem-perature of the steam by '0034; or approximately 0’8 cubic foot, or5 gallons, are required per nominal horse-power. Multiply thisnumber by the nominal horse-power of the engine, and then by theconstant 2200; divide the result by the velocity of the pump bücketin inches per minute, and the square root of the quotient is thediameter of the pump. When the stroke of the pump is one-halfof that of the steam piston, the usual diameter allowed for the pumpis found by multiplying the diameter of the cylinder by 0'3. Thearea in square inches of the injection valve should be from x^-th to^th the number of cubic feet in the steam cylinder.

The feed pump. —To find the water required to be delivered bythe pump, multiply the cubic contents in feet of steam in thecylinder for an entire revolution by the number given in the tableof cubic inches of water required to raise a cubic foot of steam atthe desired pressure, and the result will give the contents of asingle-acting pump in cubic inches; a little more may be allowedfor waste, &c., but when the steam is cut off soon in the cylinderno additional allowance will be required.

Table of the Proportion of Water to Steam.

Pressure of steam Cubic inches of water

Pressure of steam

Cubic inches of water

per square inch. in a

cubic foot of steam.

per square inch.

in a

cubic foot of steam.

I =

1-099

45

=

3700

5

1 35 °

5°

=

3-981

10 =

1-658

55

__

4-256

20 =

2-258

60

4-535

2 5 =

2-552

65

=

4-812

3 °

2-842

70

=

5-052

35

3 -I 3°

75

=

5317

40

3-4I5

&

—

5-650

The diameter of the valves is found by multiplyingthe plunger by o - 6.

the diameter

Piston rod and connecting rod. —To find the diameter of the pistonrod for compressive strain, multiply the area of the cylinder by