Chapter 12- PROPULSION STEAM TURBINES 



SPEED- 

 GOVERNING 

 VALVES 



COMBINED 

 FIELD a 

 REVERSING 

 LEVER 



PROPULSION 

 MOTOR 



GENERATOR-FIELD 

 CONTACTORS 



\main 

 condenser 



47.2 



Figure 12-29.— Diagram of turboelectric drive installation. 



show the various plant arrangements (split plant, 

 cross-connected steaming, cruising arrange- 

 ment, etc.) for the different speeds. Eachwatch- 

 stander must read and understand the steaming 

 orders and any additional orders issued by the 

 engineer officer. At this point the engineering 

 officer of the watch will request permission to 

 light fires under the superheater if two- furnace 

 single-uptake superheater control boilers is in- 

 stalled. 



On large combatant ships, there is usually 

 sufficient steam flow (even when steaming for 

 auxiliary purposes) to maintain fires under the 

 superheater side. However, in most installa- 

 tions, and particularly in destroyers, it is 

 usually necessary to be underway and making 

 about 12 knots before the fires can be lighted 



under the superheater side of the boiler. When, 

 the superheater is operating and the steam flow 

 drops below a safe minimum, the superheater 

 fires must be secured immediately. On de- 

 stroyers the superheater fires are usually 

 secured when the speed of the ship drops below 

 10 knots. 



From the standpoint of maintenance and re- 

 pairs to the steam piping, turbine casings, 

 and superheater handhole plates, it is not 

 feasible to put superheaters into operation until 

 it is expected that the ship's speed will be 

 more than 10 knots for a considerable period 

 of time. Furthermore, continually lighting off 

 and securing the superheater fires will cause 

 extensive steam leaks throughout the sys- 

 tem subjected to fast changing temperature 



343 



