224 STEAM TURBINES 



56 Of 



.about 26 in.; but the economy of the turbine in the use 

 steam increased rapidly as the vacuum was increased above 

 26 in. The conclusion is that high degrees of vacuum are more 

 desirable for turbines than for engines. 



Advantages of Turbines. The steam turbine possesses the 

 following advantages over the reciprocating engine: 



1. The ability to use highly superheated steam, resulting 

 in greater economy. 



2. Reduced cost per unit capacity of the electric genera- 

 tor because of increased speed and smaller weight per horse- 

 power. 



3. Reduced floor space, resulting in less cost for land and 

 power-station building. 



4. Reduced cost of lubrication, as no cylinder oil is needed 

 and less oil is used for bearings. 



5. Saving in labor, as no oilers are required and one engineer 

 can attend to more output than on reciprocating engines. 



6. Reduced cost of foundations, as the turbine is balanced 

 -and has no reciprocating parts. 



7. Good steam economy over a wider range of load than 

 the reciprocating engine. This is particularly advantageous 

 in power stations, where the load is variable; thus, a turbine 

 can be operated at one-fourth or one-half load with smaller 

 increase of steam consumption than would be the case with 

 a reciprocating engine under the same renditions. Also, the 

 turbine is more efficient than the engine under overloads. 



The foregoing advantages apply mainly to turbines used on 

 land. The steam turbine, however, is also used for the pro- 

 pulsion of ships. Among the advantages claimed for it in this 

 class of service are the following: 



1. For the same power, the turbine plant has less weight 

 than the engine installation. 



2. There is less danger of breakdowns, because of the smaller 

 number of parts in a turbine installation. 



3. The balancing obtained almost eliminates vibration. 



4. With fast vessels, it is possible to obtain a higher 

 speed than with reciprocating engines, at the same steam 

 consumption. 



5. Less headroom is required than with steam engines. 



