NEW DEVELOPMENTS IN HIGH VACUUM APPARATUS. 185 



Inside the feed and filter tank the mixture of steam and air is discharged 

 through a submerged pipe perforated at the bottom. By coming into contact with 

 the water the steam is condensed while the air, forced to rise by the upward flow 

 of the water, is liberated, escaping through a vent arranged in the top of the tank. 

 Water is continuously supplied to the feed and filter tank by the turbine-driven cen- 

 trifugal condensate pump, which delivers the condensate into the filter tank through 

 a swing check valve, gate valve and a perforated pipe with holes diametrically oppo- 

 site to that of the ejector discharge pipe. A vent pipe is arranged between the 

 suction inlet of the condensate pump and the condenser. 



A re-circulating pipe, with a strainer, a thermostatically operated valve and a 

 globe valve, is provided between the feed and filter tank and the condenser to insure 

 at all times a sufficient water supply for condensing the steam from the air ejectors. 



During maneuvering or while at sea, the main engine or turbine supplying the 

 condenser with exhaust steam may stop, consequently very little condensate will be 

 delivered by the condensate pump to the feed and filter tank, and not sufficient to 

 condense the discharge from the air ejector which at the time is in continuous 

 operation. 



To prevent a rise in temperature of the water in the feed tank over that de- 

 sirable (usually 140° R, depending, however, on the general arrangement of each 

 individual installation), a thermostat is arranged in the feed and filter tank, con- 

 trolling the thermostatically controlled valve. As soon as the water reaches the 

 temperature for which the thermostat is Set, the latter will open the thermostatically 

 controlled valve and the vacuum will draw water through the re-circulating pipe 

 into the condenser. By falling over the cool condenser tubes (the circulating pump, 

 of course, being in operation), this water will be cooled and returned by the con- 

 densate pump to the feed and filter tank, thus preventing any further rise in tem- 

 perature until the exhaust from the main engine again supplies sufficient condensate. 



This arrangement makes the air ejector installation absolutely reliable, even 

 if operated by inexperienced attendants. Starting is easy, as it requires only the 

 opening of two steam valves, one for the turbine driving the condensate pump and 

 one for the air ejector. During operation no attention is required, and, to shut 

 down, only these two valves have to be closed. 



A diagrammatic arrangement of an air-ejector installation with a direct-acting 

 reciprocating piston pump is shown in Plate 80. This arrangement is generally 

 applied to marine reciprocating engine surface condensers, and is similar to that for 

 marine turbine surface condensers already described. The only difference is that 

 the speed of the reciprocating piston pump is controlled by a float arranged in the 

 hot well. 



The steam-air ejector was first tried out on board a ship about four years ago. 

 It was feared that, by discharging the co-mingled steam and air into the feed tank, 

 the amount of air absorbed by the feed water' would be greater than that when 

 using a reciprocating piston air pump. Comparative tests have shown that this fear 



