Principles of naval engineering - Historic Naval Ships Association

Chapter 11-BOILER FITTINGS AND CONTROLSLONGITUDINAL SECTIONAL ELEVATIONDESIGNATION OF SYMBOLSA FEED - INLETB - FEED PIPEC - DRY PIPED - MAIN STEAM OUTLETE - SURFACE BLOW-OFF PIPEF - SURFACE BLOW-OFF NOZZLEG DESUPERHEATER INLET-H DESUPERHEATER OUTLET-J DESUPERHEATER- K - CHEMICAL FEED INLETL - CHEMICAL FEED PIPEM- SWASH PLATESN - BAFFLEP - SAFETY VALVE NOZZLESCROSS SECTIONAL ELEVATIONFigure 11-1.— Arrangement of internal fittingsheader-type boiler.in38.42the drumhead to the surface blow-off nozzle (F).When the surface blow valve is opened, the pressurein the drum forces the water above theblow-off pipe to go into the pipe through theholes on the top surface; the water from thesurface blow-off pipe then leaves the boiler byway of the surface blow valve.The desuperheater (J) is an assembly of pipelengths and return bends located below the waterlevel of the drum. The superheater steam entersthe desuperheater through the desuperheaterinlet (G), gives up its superheat to the water inthe steam drum, and then— once again at or veryclose to saturation temperature — passes throughthe desuperheater outlet (H) before entering theauxiliary steam line.The chemical feed inlet (K) is connected tothe internal chemical feed pipe (L). The chemicalfeed pipe has holes drilled in it to alloweven distribution of chemicals used for boilerwater treatment.Swash plates (M) are used to reduce thesurging or swashing of water from one end ofthe drum to the other as the ship moves. Inaddition, the swash plates act as supports forthe internal feed pipe and for the desuperheater.The safety valve nozzles (P) are not normallyconsidered internal fittings. These nozzles277