‘Slide Valve

—In a steam engine, a cup shaped piece of metal arranged to slide over and alternately cover and uncover the openings or ports through which steam is distributed to the cylinder; also called, D valve and D slide. It is situated in the steam chest, and is moved by the valve gear. This type of valve is satisfactory for use with low and medium steam pre ures, but on account of being unbalanced, it is not used to advantage with the higher pre ures., Accordingly, it is found on single cylinder engines, on the low pre ure cylinder of compound engines, and sometimes on both the intermediate and low pre ure cylinders of triple expansion engines. Engines using slide valves, can be constructed with le clearance than when fitted with piston valves; this is an advantage, but is offset by the perfect balance of the piston valve with respect to the steam features.