number  of  rpm  ordered.  Major  speed recorded  using  the  following  symbols: 1/3–ahead  1/3  speed 2/3-ahead  2/3  speed I-ahead  standard  speed II-ahead  full  speed III-ahead flank speed Z-stop B1/3–back  1/3 B2/3-back  2/3 BF–back full speed changes are BEM–back  emergency  speed 4. The number of revolutions corresponding to the major speed change ordered is entered in column 3. When the order received is recorded as rpm in column 2  (minor  speed  changes),  do  not  make  an  entry  in column 3. 5. The shaft revolution counter reading at the time of the speed change is recorded in column 4. The shaft revolution counter reading is taken hourly on the hour while  underway  and  entered  in  column  4. Ships  and  craft  with  controllable  reversible  pitch propellers also use column 4 to record responses to speed change orders. However, they record changes in the propeller pitch in feet and fractions of feet. Entries for astern pitch are preceded by the letter  B. Entries are made of counter readings each hour on the hour. This information  helps  in  the  calculation  of  miles  steamed during  those  hours  when  the  propeller  pitch  remains constant. On ships with gas turbine propulsion plants, a bell logger provides an automatic printout each hour. It shows when propeller rpm or pitch change by more than 5 percent, when the engine order telegraph is changed, or when the controlling station is shifted. Before going off watch, the EOOW signs the Bell Book on the line following the last entry for his or her watch  and  the  next  officer  of  the  watch  continues  the record on the following line. In machinery spaces where an EOOW is not stationed, the watch supervisor signs the bell sheet. NOTE:  A  common  practice  is  to  have  the throttleman also sign the Bell Book before the EOOW or his relief. In ships or crafts with controllable pitch propellers, bridge personnel control the engines and maintain the Bell  Book. Some  smaller  ships  with  controllable  pitch propellers  sometimes  need  to  switch  control  of  the engines  between  the  engine  room  and  the  bridge.  For that purpose they maintain two Bell Books, and the personnel in control of the engines at any one time make entries in the Bell Book. When control shifts from one to the other, say from the bridge to the engine room, bridge personnel enter the time they gave control to the engine room. At the same time, engine-room personnel enter the time they assumed control. When the Bell Book  is  maintained  by  bridge  personnel,  the  officer  of the deck (OOD) signs it. When it is maintained by engine-room personnel, the EOOW signs it. At the end of the day, the two sets of Bell Sheets are consolidated and approved so there is only  one official set for the day. There can be no alterations or erasures in the Bell Book.  An  incorrect  entry  should  be  corrected  by drawing a single line through the entry and recording the correct entry on the following line. The EOOW, the OOD, or the watch supervisor should initial changes. OPERATING RECORDS Engineering operating records help ensure regular inspection  of  operating  machinery  and  provide  data  for performance analysis. They should be reviewed daily at the  level  specified  by  appropriate  directives.  Operating records are not intended to replace frequent inspections of  operating  machinery  by  supervisory  personnel.  Also, they  are  not  to  be  trusted  to  warn  of  impending casualties.  Personnel  who  maintain  operating  records must be properly indoctrinated. They must be trained to correctly obtain, interpret, and record data and to report any  abnormal  conditions.  Acceptable  high  and  low readings and abnormal readings must be permanently recorded on operating logs for each machinery type. Abnormal readings should be circled in red and reported to the watch supervisor. The  type  commander’s  directives  specify  which engineering  operating  records  will  be  maintained  and prescribe the forms to be used when no standard record forms  are  provided.  The  engineer  officer  may  require additional operating records if he finds them necessary. The operating records discussed in this chapter are generally retained on board for 2 years. They may then be destroyed according to current disposal regulations. Complete  records  must  be  stowed  where  they  will  be properly preserved and easily located in case of need. PROPULSION STEAM TURBINE AND REDUCTION GEAR OPERATING RECORD The Propulsion Steam Turbine and Reduction Gear Operating  Record,  NAVSEA  9231/1  (fig.  2-3),  is  a daily  record  maintained  for  each  main  engine  in 2-8