Exhaust valve cage

The exhaust valve cage is the removable housing in a two-stroke cylinder cover that carries the single central exhaust valve, its seat, spindle guide, and the hydraulic or pneumatic actuator. Building the valve into a cage lets the crew lift the whole assembly for overhaul without disturbing the cylinder cover, cutting maintenance time at the 8,000 to 16,000 hour valve overhaul interval. The seat and spindle run in the hottest gas path and suffer high-temperature burning and hot corrosion from vanadium and sodium in residual fuel. Many designs spin the valve with vanes in the exhaust stream to even out seat temperature and wear.