158 THE APPLICATION OF SMALL STEAM TURBINES 



the total steam consumed was 2,200 pounds per hour exhausting against 5 pounds 

 back pressure at 1,550 revolutions per minute. 



Plates 75, 76 and yy show typical types of forced-draft fans used by the Ger- 

 man, British, and Greek navies respectively. 



PUMPS. 



The reliability demonstrated by six years of actual service with destroyer fans 

 resulted in the Navy Department widening the application of the small turbine, 

 and in 191 1 specified turbine-driven centrifugal pumps on the battleship Arkansas. 

 A serious proposition at first presented itself here on the grounds of economy 

 owing to the slow speed necessary for the pump and the limitations of weight and 

 diameter of turbine wheel. However, this individual turbine efficiency is not of 

 such prime importance as would be at first imagined, and (as will be explained 

 later) that while the turbine itself could not at first be called an efficient machine 

 operating under the conditions at which it does, the eflfect of the poor efficiency 

 when considered in conjunction with the whole performance of the ship is of little 

 if any importance. 



For reasons that will be fully dealt with later and taken into consideration in 

 conjunction with the reliability in service, it will be seen that the lack of unit ef- 

 ficiency is of minor importance This is demonstrated by the fact that the latest 

 boats have been or are being equipped with similar apparatus. 



The advantages of the turbine-driven boiler feed pump have long been well 

 known to the marine profession, but certain difficulties in their installation pre- 

 sented themselves, necessitating, as it was considered, special designs to suit ship- 

 board requirements. This, together with the satisfactory service given by any 

 good make of reciprocating pump, resulted in rather slow progress along these 

 lines. 



However, in 191 2, the Navy Department decided to run exhaustive tests on a 

 unit specially designed for their work (Plate 78). The turbine was built by the 

 Terry Steam Turbine Co., and the pump by the Worthington Company, and tests 

 were conducted on this apparatus at Annapolis and reported in the November, 

 1912, issue of the Journal of the A. S. Naval Engineers. Some interesting ex- 

 tracts from the official report of these tests are given below : — 



"The fact that a turbine-driven centrifugal pump can be quickly started from 

 a cold condition and put into service constitutes one of its advantages (p. 1226). 



"Pumping warm water there is little difference between the economy of this 

 centrifugal pump and the simplex pump. For cold water up to 33 per cent of full 

 load the simplex pump is more efficient. As the values quoted are based upon a 

 careful regulation of the number of nozzles in use according to load, the com- 

 parison will be less favorable to the centrifugal pump at light loads if such regula- 

 tion is not carried out. On the other hand, the test of the simplex pump was con- 



