424

MODERN STEAM PRACTICE.

falls into the pump chamber by gravitation; tbe head valves are

placed at the side and above the line of foot valves, with a hot well

for each pump fitted with separate

discharge pipes overboard. With this

arrangement of foot and head valves

air is not so liable to collect between

the piston and valves; it is therefore

preferable to have an air valve—

should it be desirable to place the

discharge valves below the line of

head valves—arranged at the highest

point in the foot-valve chamber, by

which the air is forced into the dis- Fig. 308.—Air Pumps with Condenser at centre1 _ 1 j rpt -1 , fitted with inverted Foot Valves and Dis-

Charge pipe overboard. The exhaust charge Ch amb=rs at side, all in one Casting.

pipe is of a large diameter, suited for a, Condenser. B, Hot well, c, Foot-valveboth engines, placed in the centre of seat ' ”■ “ ead - valve seat. , Air pump,the condenser, and the injection pipe

is placed at the top on the same centre line, thus the water isshowered down on each side of the condensing chamber: thisarrangement is very effective. In other arrangements the valvesare placed vice versa, the condensingchambers being at the side, and the dis-charge chamber placed centrally abovethe pumps, with one discharge pipeoverboard; while there are two exhaustpipes, each passing into a separate con-denser, with the injection pipes under-neath. This arrangement has the ad-vantage of the condensers for the cylin-ders being separate from each other,

and this enables us to regulate the in- Fi s- 309—Air Pump with Condenser at

. . 1-1 side fitted with inverted Foot Valves and

jection water required by each, which Discharge Chamber at centre.we cannot do when one injection pipe a, Condenser. b, Hotweii. c, Foot-valve

r 1 t 1 /-TM seat. d, Head-valve seat. e, Air pump.

serves for both condensers. ihesecon- F , Feedpump. g, Exhaust P i P e.densers, when required for engines of

ordinary power, are generally cast in one piece, but for heavyengines they should be two separate Castings, with air pump andadjuncts arranged as in the previous examples.

The Surface System of Condensation.—B efore describingthe construction of the condenser for the surface System of con-