CHAPTER 4 STEAM-POWERED CATAPULTS Steam  is  the  principal  source  of  energy  and  is supplied  to  the  catapults  by  the  ship's  boilers.  The steam is drawn from the ship's boilers to the catapult wet steam accumulator, where it is stored at the desired pressure. From the wet accumulator, it is directed to the launch valve, and provides the energy to launch aircraft. The  most  significant  differences  between  the  various types of steam catapults are the length and capacity. See table 4-1 for the differences. Each steam catapult consists of eight major systems: ·  Steam System ·  Launching Engine System ·  Lubrication System ·  Bridle Tensioning System ·  Hydraulic System ·  Retraction Engine System ·  Drive System ·  Catapult Control System STEAM SYSTEM LEARNING   OBJECTIVES:   Describe   the components of the steam system. Describe the function of the steam system. The catapult steam system (fig. 4-1) consists of the steam wet accumulator, accumulator fill and blowdown valves,   trough   warm-up   system,   steam   smothering system and the associated valves and piping. The seam system is under the technical cognizance of NAVSEASYSCOM and is operated and maintained by engineering  department  personnel.  An  explanation  of the  steam  system  major  components  will  provide  a better understanding of catapult operations. Figure 4-2 is  a  simplified  schematic  of  a  typical  catapult  steam piping  arrangement.  The  schematic  only  shows  the piping  and  valves  associated  with  a  single  catapult when   lined   up   with   the   steam   plant   that   normally supplies  that  catapult.  Valves  and  piping  that  allow cross connecting of catapults with all steam plants are not shown. Cross connecting provides the capability of operating any catapult from any power plant. WET ACCUMULATOR WARM-UP The accumulator warm-up procedure allows valves and piping between the steam plant and the catapult to initially slowly warm up to bring the metal temperatures   to   operating   level.   Hot   feed   water   is admitted into the steam accumulator to approximate the low  operating  level.  The  launch  valve  is  opened  to purge  air  from  the  accumulator  and  steam  is  slowly admitted  into  the  accumulator  feed  water  to  raise  the water    temperature.    When    the    water    temperature reaches approximately 225 degrees, the launch valve is closed   and   accumulator   heating   continues.   Steam pressure  is  increased  in  increments  allowing  enough time  at  each  increment  for  the  water  temperature  to increase  to  a  predetermined  temperature.  This  slow increase  in  temperature  and  pressure  will  ensure  a thermally stable accumulator when operating parameters are reached. TROUGH WARM -UP The  trough  warm-up  procedure  allows  valves  and piping  between  the  steam  plant  and  the  catapult  to slowly  warm  -up  to  bring  the  metal  temperatures  to operating level. When steam is directed to a catapult for 4-1 Item C-13-0 C-13-1 C-13-2 Power stroke (in feet) 249-10" 309-8 3/4" 306-9" blTrack length (in feet) 264-10" 324-10" 324-10" Weight of shuttle and pistons (in pounds) 6,350 6,350 6,350 Cylinder bore (in inches) 18 18 21 Power stroke displacement (in cubic feet) 910 1,148 1,527 Table 4-1.—Steam Catapult Data