34 §

MODERN STEAM PRACTICE.

strain on the piston rod is not so much feit, and when the crossheadsare uncoupled from the crank pins the cylinders are not so liableto tilt. This will be found a great convenience when undergoingrepairs at sea. The larboard and starboard trunnions are for thesteam, which passes through a beit cast along with the cylinderinto the valve casing. The faces for the valves are generally of thethree-ported type, two ports are for the steam and a central one forthe exhaust. The two central trunnions are for the exhaust steam,which passes into the beit around the cylinder, and then into the

Fig. 220.—Cylinder.

a, Cylinder. b b, Trunnions. c, Cylinder cover.d, Bottom cover. ee, Valve faces. ff, Steampassages. g, Exhaust passage.

Fig. 221.—Trunnion Pipe and Stuffing Box.

A, Trunnion pipe. B, Gland for stuffing box. C, Cy-linder. d, Throttle-valve pipe. e, Bracket forsupporting do. f, Pillow block, g, Frame.

condenser through the hollow trunnions; thus one half of the beitallows the steam from the boiler to pass into the valve casing, andthe other half acts as a passage to the condenser, the division beingformed by feathers or bars cast in the cylinder.

The trunnion pipes for the steam and exhaust are fitted with glandsand packing spaces formed in each trunnion; the form er are boltedto the branch pipes, which are supported by brackets bolted to thebottom frames, and the latter are bolted to the condenser casting,