Principles of naval engineering - Historic Naval Ships Association

Chapter 11-BOILER FITTINGS AND CONTROLSDRY PIPESTEAMSTEAMWATERSURFACE BLOWLINEINTERNAL FEEDPIPEGENERATINGTUBESFigure 11-3.— Flow of steam and water in steam drumof double-furnace boiler.38.44scrubber, its direction is changed frequently,and with each change of direction some moistureis lost. The steam passes out of thescrubber element into the top part of the steamdrum and then enters the dry pipe.While the steam is rising, the water is fallingto the base of the separator. Stationarycurved vanes in the bottom of the separatorserve to maintain the rotary motion of the wateruntil the water is finally discharged from thebottom of the separator. Since the vanes arelocated around the periphery of a flat plate, thewater passes from the separator only aroundthe outer edge. The flat plate also serves tokeep the steam, which is in the center of theseparator, from being carried downward withthe water.A flat baffle plate is fitted at the base ofeach of the two end separators on each side.This baffle plate guides the water that is beingdischarged from the separator to the center ofthe drum, where it mixes thoroughly with therest of the water in the drum. Without such abaffle, the water from these end separatorswould tend to flow directly to the downcomersand, since it is hotter than the rest of the waterin the steam drum, it would tend to disrupt theboiler circulation.Figure 11-6 illustrates the arrangement ofinternal fittings in an older single-furnaceboiler. The internal fittings for this boiler arequite similar to those found in the double-furnaceboiler, except that the single-furnace boilerhas a desuperheater (item 5 in fig. 11-6).The internal fittings in the steam drum requireroutine maintenance and upkeep. All maintenancerequirements shall be conducted inaccordance with the Planned Maintenance Subsystemof the 3-M System.When a boiler is opened for cleaning ofwatersides, the internal fittings must be removed.The fittings are bolted into place; removingthe bolts allows you to remove thefittings. Be sure that all bolts and tools usedin removing the bolts are strictly accountedfor. When removing internal fittings, be sure toidentify them so that you will be able to reinstallthem correctly.After removing the fittings from the steamdrum, thorouglily wirebrush and clean them.Check the dry pipe, the internal feed line, andthe surface blow line to be sure that all theholes are free and clear of obstructions. Inaddition, inspect the inside of the feed line foroil accumulations; if you find any sign of oilnotify the CPO in charge of the fireroom.279