Recent Tendency of Marine Boilers

Abstract

Several improvements can be poioted out in recent marine boilers of which fundamental structure, two drums, bent tube, integral single furnace has been remained to improve. The basic heat cycle of improved marine steam power plant is with 850 psig of steam pressure, 900°F or 950°F of steam temperature, and 89% of boiler efficiency and four stage feed heating system is applied. The steam condition of this cycle, which recently is specified at the main turbine inlet instead of at the boiler outlet, is stepped up with theoretical background on commercial marine practice. Boilers applied for these plant are fitted with rotary regenerative air preheaters to lower boiler exhaust gas temperature, which causes low temperature corrosion problems. The problems, however, are though to be resolved by water washing, easy replacement of cold-end elements and more accessibility. Major features of recent marine boilers are : (1) completely water-walled furnace, (2) accessible convection type superheater with interpass superheat control, (3) Minimizing of furnace refractories, (4) stronger structure of pressure parts, (5) simplification of support to minimize foundation and installation work, (6) application of long retractable mass action soot blowers for superheater, (7) enlargement of application of automatic and remote control devices.