CHAPTER 4 BOILERS The function of a boiler in the steam cycle is to   convert   water   into   steam.   Reliability   in operating  naval  boilers  and  associated  equipment is  important  for  the  power  plant  to  operate  at maximum efficiency. The complex design of naval boilers   requires   a   high   degree   of   technical knowledge and skill on the part of the fireroom personnel  responsible  for  boiler  operations.  All engineers  should  have  some  knowledge  of  the principles of combustion, how combustion occurs in a boiler, and the combustion requirements for operating a boiler more efficiently. You may want to review combustion in chapters 2 and 3 of this textbook. This chapter describes boilers commonly used in   propulsion   plants   of   naval   steam-driven surface   ships.   This   information   is   general   in nature and does not relate to any one class of ship. Chapter 221 of the  Naval  Ships’  Technical  Manual is  the  basic  doctrine  reference  on  boilers.  For detailed   information   on   the   boilers   in   any particular  ship, consult   the   manufacturer’s technical  manuals  furnished  with  the  boilers. Upon  completion  of  this  chapter,  you  will have  the  knowledge  to  be  able  to  identify  and understand boiler terminology, the basic types of naval   boilers   and   their   operating   principles, interpret  gauges  and  indicators  that  aid  in monitoring  operating  parameters  of  naval  boilers, and  understand  boiler  construction.  You  should be able to identify the major parts of a boiler and its  functions.  Also,  you  will  learn  about  safety precautions that must be observed during boiler light-off. BOILER  TERMINOLOGY Before  studying  the  types  of  boilers  used  in propulsion  plants  aboard  Navy  ships,  you  need to know the boiler terms and definitions used most frequently  by  shipboard  personnel.  In  this  section we  have  listed  some  of  the  terms  used  in  this chapter and by fireroom personnel on the job. It is  not  an  all-inclusive  list,  but  it  will  help  form a basis for your understanding of the information presented  on  boilers. Fireroom—  The  fireroom  is  a  compartment containing boilers and the operating station for  firing  the  boilers. Boiler   room—   The  boiler  room  is  a compartment  containing  boilers  but  not containing   the   station   for   firing   or operating  the  boiler. Main   machinery   room—   The   main machinery  room  is  a  compartment  con- taining boilers and the station for firing or operating the boilers and main propulsion engines. Boiler  operating  station—  The  boiler operating station is a station from which a boiler or boilers are operated, applying particularly  to  the  compartment  from which  the  boilers  are  operated. Steaming hours— Steaming hours is the time  during  which  the  boilers  have  fires lighted until fires are secured. Boiler full-power capacity—  Boiler  full- power capacity is specified in the contract specifications of a ship. It is expressed as the number of pounds of steam generated per hour at the pressure and temperature required  for  all  purposes  to  develop  con- tract  shaft  hp  of  the  ship  divided  by  the number  of  boilers  installed.  Boiler  full- power capacity is listed in the design data section   of   the   manufacturer’s   technical manual  for  the  boilers  in  each  ship.  It may be listed either as the capacity at full power  or  as  the  designed  rate  of  actual evaporation  per  boiler  at  full  power. 4-1