422

MODERN STEAM PRACTICE.

The snifting valve for all condensers is fitted as low down aspossible.

For similar arrangements of air pumps situated on each side ofthe middle frame, the foot valves are placed low down on the otherside of the centre line of the cylinder in regard to the air pump,with the head valves in one chamber common to both, arrangedbetween the air pumps; the doors for getting at the valves areplaced on the top of the valve chambers, which is found a very con-venient and handy arrangement. One discharge pipe, placedcentrally with the hot well, serves for both of the pumps. Theexhaust steam comes in at the top end of the chamber, and thewater falls down underneath the air pumps, the condenser beingpartly above and partly belowthe pumps, and having a divi-sion cast in for separating andstrengthening it. The injectionvalve can be placed above theexhaust pipes, and thus showerthe injection water down on thesteam, instead of meeting it asin the previous example.

When the air pumps are situ- Fig. 306.— Air Pump with Condenser outside fitted with, , ! ,1 . • 1 inverted Foot Valves and Discharge Chamber at

ated underneath the motion bars, centre

a good plan is to invert the foot A , Conden ser. B, Hot well, c, Foot-valve seat.

1 1 • _ i.1 _ • 4-U~ D, Head-valve seat. e e, Guide bars for piston-rod

valves, placing them m the crosshead F _ Airpump . G , Discharg(! p ; pe .bottom of the condensers, which

are seated in a line with the outside frame; thus the condensingwater and the Condensed water from the steam fall into eachsuction chamber by their own gravity. In this arrangement thehead valves are placed in a central chamber between the pumps;and this chamber has one discharge pipe common to both setsof air pumps. The exhaust steam enters at the top, the injec-tion pipe is placed under and showers the water upwards tomeet the steam, care being taken that the water cannot passinto the exhaust pipe. The injection pipe, when placed below theexhaust pipe, should always be pierced with holes, to shower thecondensing water meeting the steam, instead of pouring it downvertically; by this means the water and steam are brought intobetter contact, and form a more rapid vacuum.

When the air pumps and condensers are arranged in a line with