PROGRESS IN TURBINE SHIP PROPULSION. 73 



should be regularly observed to be sure that the water is not entering the system 

 from any source. 



8. The system which provides a settling tank, capable of taking a complete 

 charge of oil for the system, is to be recommended. 



9. It is considered desirable that the oil coolers should be arranged, if possible, 

 to have the oil pressure superior to the water pressure, so that a loss of oil will 

 occur rather than the admixture of salt water. The former would be shown by the 

 oil level indicator in the lower tank. 



There are installations, such as destroyers, where there is but little head room 

 and where a gravity oiling system is impracticable, and a pressure oiling system 

 must be employed. In this case twin strainers or their equivalent must be resorted 

 to. These are of course dangerous because of them becoming choked and interrupt- 

 ing the service, or bursting and letting dirt through if the pumps are sufficiently 

 powerful. If they must be employed they should invariably be by-passed through 

 a spring-loaded check valve, loaded to say one-half pound, so that with a slight 

 increase of resistance of the strainers the oil will by-pass them and the service 

 never be interrupted. 



Concerning arrangements of the turbines themselves, a design of a single com- 

 plete expansion unit has already been referred to. The general design of the cross 

 compound units is shown in Fig. 16, Plate 43, and Fig. 17, Plate 44. The re- 

 ceiver pressure between the high and low-pressure elements approximates 5 pounds 

 gauge at full power, rendering it adaptable for connection to the auxiliary exhaust 

 steam and the feed heater as has previously been discussed. The detail construction 

 of these turbines, method of inserting blades, etc., etc., will not be dealt with in 

 detail here as already much has been written concerning them,* except those details 

 which apply particularly to marine work. 



The turbines illustrated in Figs. 16 and 17 are essentially for vessels always 

 operating at their maximum speed and are subject to modifications on ships where 

 cruising speeds are involved. One of these, known as the "divided flow" type, is 

 shown in Figs. 18 and 19, Plates 45 and 46, and are the turbines applied to a 

 Swedish cruiser. The combination comprises an impulse element in the high- 

 pressure turbine through which passes all the steam to the system. The nozzles 

 are arranged in groups, each under valve control so that the turbine may realize sub- 

 stantially full, pressure at the nozzles with widely differing volumes of steam flow. 

 The general arrangement of this combination is shown in Fig. 20, Plate 47. After 

 passing the impulse element the steam divides, one portion continuing through the 

 same turbine to condenser pressure ; and a slightly greater portion passing over to 

 the low-pressure element through which it expands to the condenser. For cruising 

 the one low-pressure element may be cut out of service, the steam closed to certain 

 nozzles, and the turbine operated with fair economy at the reduced power. The rea- 

 son for a greater proportion of steam passing to the low pressure is in order that 

 the work may be equal on the two pinions at full power. 



*See Electric Journal for January, February, March, April, 1918. 



