STATIONARY ENGINES.
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must be fitted with an overflow pipe, which is placed in communi-cation with the discharge from the air pump. When the water isvery bad the air pump should be lined with a barrel of compositionmetal, or a brass barrel is so placed, centrally with the condenser;and when suitably strengthened and supported from the con-denser vessel, the latter proves a very compact arrangement, com-bining the condenser and air pump in one. The foot valve, inordinary arrangements, is placed at the bottom, between the con-denser and air pump. It is a flap valve hinged vertically, and issometimes made of wrought iron, faced with a brass beating surface,with a corresponding brass face securely pinned on the cast-ironseat. The valve is bent to form a hooked hinge, so that it can bereadily taken off the spindle on which it hinges without disturbingthe seat, a door being fitted to the condenser casting for inspecting
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a, Bücket , b , Brass seat for valve. c, India-rubber disc. d, Guard. e, Rod secured witha nut at the bottom.
and adjusting the valve. The head valve, placed at the top of theair pump, is a disc of metal having a deep boss at its centre,strengthened with ribs radiating from the centre, and having a holebored through the boss for receiving the air-pump rod, which actsas a guide for the valve. Sometimes this boss is fitted with a gland