Air-pump

For displacing air, or exhausting the air from closed ve els. Invented by Otto von Guericke of Magdeburg ab. 1650. Many small air-compre ors would be called air-pumps. In a condensing steam-engine, the air-pump is an e ential organ, whose duty is to maintain the vacuum in the condenser. It is a lifting pump, the lower end of the barrel being below the level of the floor of the condenser and separated from it by the foot-valve. When the bucket rises and the water in the condenser and in the pump barrel has equally low pre ures upon it. it pa es by gravity into the pump through the foot-valve, together with any air which may have come in. When the bucket descends the foot valve closes, and the water and air pa up through the bucket-valves to be lifted and discharged to the hot-well. The IMG:content-0069.jpg:[graphic] Air-pump. cylinders. With jet-condensers, the barrel and bucket arə usually of bra -composition.