Exhaust valve operation and maintenance
Two stroke cross-head engine have a single exhaust valve mounted in the center of cylinder head. Exhaust valves open towards inside in the cylinder,such away that the gas pressure inside cylinder ensure positive closing & helps to avoid building up carbon on the valve seat.The valve opening and closing is controlled by cam mounted on the camshaft. Modern 2 stroke cross-head engines work on hydraulically operated air spring exhaust valves. Now a cam operate hydraulic pump instead of the push rods in earlier versions. The pump which displaces Oil from the engine LO system operate a piston in the exhaust valve which push valve to open. Here in place of the mechanical spring there is an “air spring”. Air at 7 bar through a non return valve goes to the underside of the piston attach to the valve spindle. when valve open, air underneath is then compressed. When hydraulic pressure is released, the expansion of the compressed air assist in the closing of valve. Air also taken d