186 NEW DEVELOPMENTS IN HIGH VACUUM APPARATUS. 



was groundless. The amount of air absorbed in the feed water, when using the 

 ejector, was 35 per cent less than that when using the twin-beam air pump. 



With this obstacle removed, the air ejector rapidly gained the confidence of 

 shipbuilders and marine engineers, so that there are to-day to the writer's knowl- 

 edge over five hundred ships built in this country equipped with steam-air ejectors. 

 About one-third of these have been in successful operation for periods up to two 

 years. 



From this it would appear that the steam-air ejector to-day occupies a position 

 among the air pumps similar to that occupied by the steam turbine among steam- 

 operated prime movers. Its advantages, reliability and simplicity are dominating fac- 

 tors which will gradually make its adoption as universal as that of the steam turbine. 



DISCUSSION. 



Thb President: — Mr. Kothny's paper, "New Developments in High Vacuum Appa- 

 ratus," is now open for discussion. 



Mr. Martin L. Katzenstein, Member: — I have been unable, since the receipt of this 

 paper, to prepare a complete reply, and the limited time for discussion would hardly permit 

 such a presentation, even if considered desirable. In many ways the paper is interesting, 

 and I agree with certain features in the discussion of the operation of the ejector itself. In 

 other respects the paper, while interesting, is misleading and quite incorrect. In order to 

 save the time of the members, I have outlined briefly a discussion of the principal points to 

 which I would like to call attention. 



The development of the marine condensing unit has not kept pace with stationary prac- 

 tice. A vacuum corresponding to an absolute pressure of .5 to .6 pound is maintained in 

 many of the more important public utilities installations during the winter months, and the 

 vacuum producing apparatus has reached the highest stage of efficiency. With full appre- 

 ciation of the modifying conditions, I see no reason why, as stated on page 175, the limit for 

 marine condenser performance should be placed at IJ-a inches for 60 degrees or 3 inches for 

 70 degrees, whereas a stationary plant is designed for and readily maintains 1^ and in some 

 cases iy2 inches with 70 degrees, the latter corresponding to a saving of 2j4 to 3 per cent 

 in the steam consumption of the main turbine. 



On page 176 reference is made to air leakage, and Plate 68 gives curves stated to show 

 "permissible air leakage for marine surface condensers." Why the word "permissible" is 

 used, I do not understand. The condenser must handle all the air, including leakage coming 

 through from the turbine. Possibly the curve limits the air capacity of the ejectors as fig- 

 ured by the author, or it may have reference to the condenser efficiency which is definitely 

 known to be reduced upon a straight line curve in direct ratio to the amount of air leakage. 

 For discussion of this feature, I would refer you to the paper presented in May, 1916, at the 

 Chicago meeting of the National Electric Light Association. 



