THE PROPELLING MACHINERY OF THE U. S. S. LEVIATHAN. 227 



hydraulic cylinders. Above each will be seen a small rectangular box having an 

 electric light and name plate stating clearly what position the change valve is in. 



No interlocking gear is fitted between the ahead and astern valves, and this 

 appears to be unnecessary in view of the precautions taken to ensure the proper op- 

 eration of the turbines. 



On again referring to Fig. 13, above the second and third wheels (steam to 

 high-pressure ahead), a small hydraulic cylinder will be noticed, the purpose of 

 which is as follows: — 



Under "Maneuvering Connection" it is essential that not more than one-half 

 of the steam from the boilers should be allowed to pass through the high-pressure 

 ahead and port low-pressure ahead turbines, otherwise these engines could be 

 heavily overloaded. On switching the change valve into maneuvering connection, a 

 cam connected with levers opens valves operating the two hydraulic cylinders and 

 locks the high-pressure ahead valve from the starboard side steam lines, and the 

 other valve will only open a limited amount. 



Interconnecting Pipes and Change Valves between the Turbines. — The dif- 

 ferent ways in which the turbines can be operated and the means taken to do this 

 have features of interest. Dealing with the high-pressure ahead, this unit can be 

 operated in three different ways: — 



1. The exhaust steam can pass over to the mid-pressure turbine, as in "triple- 

 series" connection. 



2. It can exhaust directly to the port low-pressure ahead, as under "Ma- 

 neuvering." 



3. The exhaust steam can pass directly to the condensers of the port side. 

 Fig. 15, Plate 102, illustrates the change valve, the forward chest of which is 



bolted to the inlet branch of the mid-pressure and the aft chest to the inboard nozzle 

 at the exhaust steam belt of this casing. The valves are of the piston type, hy- 

 draulically operated, and the two views indicate the way the steam flows under the 

 different methods of operation. Another change valve of similar design (port No. 

 2 on engine-room arrangement. Fig. 2, Plate 96) either allows the steam to pass over 

 to port low-pressure ahead or to condenser. This valve is operated hydraulically 

 from the working platform. A gate valve is fitted on the pipe opening to the con- 

 densers ; this is worked by hand and is always kept closed. 



The mid-pressure ahead turbine can be worked as follows : — 



1. Triple-series, receiving exhaust steam from the high-pressure ahead. 



2. Maneuvering; live steam is admitted to the nozzles of the impulse wheel, 

 passes through the reaction blades and over to starboard low-pressure ahead. 



3. The exhaust steam can pass directly to the condensers of both port and 

 starboard sets through the change valves on port and starboard side (No. 2). 



The high-pressure astern turbines of the inboard shafts can be used as 

 follows : — 



The exhaust steam from each of these units can pass over to the low-pressure 

 astern, or, for emergency conditions, change valves are installed (No. 3, Fig. 2) 



