Chapter 12- PROPULSION STEAM TURBINES 



ASTERN STUM 



Win 



ASTWM »K*D 

 BUOE ttACTWH 

 GROUP BUWM 



STEAM INLET 



\ FROM H.P. TUIMNE 



ASTERN STEAM INLH 



ASTERN 

 N0Z21I 



BLOCK 

 CARBON 

 PACKING o 

 GIANO 



6UND STEAM 

 S£AL^^ 



BEARING OIL 

 INLET . 



ASTERN NOZZlf BLOCK 



ASTERN BUDE GROUP 



ROTOR POSITION 

 I MICROMETER 



BEARING 

 OIL DRAIN 



EXHAUST FLANGE 

 TO CONDENSER 



BLADE EXHAUST STEAM DRAIN EXHAUST STEAM 

 SHIELD DEFLECTOR OEFIICTOR 



BUDE BAFFLE GLANO \ 



SHKLD CENTERING PM DRAIN 



Figure 12-27.— Low pressure turbine 

 (with astern elements). 



EMERGENCY OIL 

 \f7lG0VERN0R 



BEARING & 



I GOVERNOR 



PUMP OIL 



. INLET 



BEARING OIL 

 DRAIN 



147,101 



or CPO in charge of an engineroom watch, can 

 contribute a great deal to the economical and 

 safe operation of the boilers if they use the 

 acceleration and deceleration charts provided 

 for that particular propulsion plant. 



Acceleration and deceleration charts are 

 posted at each main engine throttle board. These 

 charts give the exact amount of time that the 

 throttleman should use in changing speed. When 

 a speed change is ordered, the throttleman can 

 tell instantly, by checking the chart, the minutes 

 and seconds necessary for him to accelerate 

 or decelerate to the new speed. Main engine 

 control has tachometers indicating the number 

 of rpm each shaft is doing. By means of the 

 tachometers, the engineeringofficer of the watch 

 can coordinate the rpm of the shafts; if one 

 throttleman accelerates or decelerates too 

 rapidly or too slowly, the engineering officer 

 of the watch can detect the trouble and have 

 it corrected. 



Improper acceleration or deceleration 

 wastes fuel, leads to uneconomical operation of 

 the propulsion plant, and may cause operational 



problems in the fire room. Each throttleman 

 should have a revolution - pressure table which 

 gives the approximate pressure required in the 

 first stage of the high pressure turbine to de- 

 velop a certain rpm. By using such a table, 

 together with the acceleration and deceleration 

 charts, the throttleman can make his watch- 

 standing much easier and, at the same time, 

 contribute to economical and efficient operation 

 of the plant. There must always be complete 

 understanding between the engineroom and the 

 bridge as to how many rpm are to be maintain- 

 ed for one-third, two-thirds, standard, and full 

 speed. The throttleman should never relieve 

 the watch without knowing the rpm for these 

 speeds. 



For most efficient turbine operation, the 

 highest possible vacuum must be maintained 

 in the condenser. Air must not be allowed to 

 leak into the condenser, exhaust trunks, throt- 

 tles, lines to air ejectors, gage lines, idle 

 condensate pump packing, makeup feed lines, 

 or any other part of the system under vacuum. 

 A steam pressure of 1/2 to 2 psi must be 



341 



