48 DISCUSSION ON MAY MEETING PAPERS. 



ful Diesel-engine installations of the horizontal type operating at moderately high speeds, 

 such as I have in mind; they are driving oil line pumps, electric generators, and have pro- 

 vided power generally for many years, and apparently they are entirely satisfactory. In 

 vertical designs the operation at moderately high speed can certainly be accomplished to 

 better advantage than with the horizontal type. 



No. 12, as to higher first cost and maintenance charges — the figures that I have seen 

 do not bear this out, and as a matter of weights the Diesel electric drive shows weights 

 that run from 65 to 70 per cent of the weight per shaft horse-power of the direct coupled 

 Diesel twin-screw installation. 



In the statement that follows No. 12, reference is made to the higher consumption of 

 fuel and lubricating oil, which, combined with electrical losses, calls for a total expendi- 

 ture of about 50 per cent over the direct-drive system. While there may be the 15 per 

 cent of electrical losses, the latest designs do not show such excesive consumption of fuel 

 and lubricating oils to justify this figure, and I should say that this item, instead of SO per 

 cent, should be reduced to a maximum of 20 per cent. 



The authors refer to the oil consumption of the direct-drive as 0.31 pound per indi- 

 cated horse-power of the main engines. Would it be possible to state what shaft horse- 

 power was developed? 



I would appreciate very much the authors' comments on the foregoing. 



Mr. H. B. Oatley, Member (Communicated) : — Mr. Warriner's paper has been 

 read with much interest, and he is to be congratulated on the interesting facts brought 

 out and the progressive ideas advanced. 



With particular reference to that part of the paper which refers to the infrequent use 

 of superheated steam in marine practice in the United States, it may not be out of place 

 to mention that in Europe there recently have been constructed, or are on order at pres- 

 ent, 147 vessels equipped with geared turbines of several different makes, which total 754,- 

 000 shaft horse-power and 28 vessels with reciprocating engines, developing 86,000 indi- 

 cated horse-power. These geared-turbine vessels range from the small converted sailing 

 vessel of 750 horse-power to the 20,000 horse-power passenger vessel Guilio Cesare. All 

 of these vessels are or will be fitted with superheaters, the majority of which are capable 

 of delivering from 200 to 225 degrees of superheat at the throttle. 



The almost universal adoption of highly superheated steam on the vessels now under 

 construction by European builders is proof that the vessel owner has found it profitable to 

 specify its use and that such procedure has the full approval and cooperation of the turbine 

 builders. With geared turbines it usually is thought necessary to use saturated steam on 

 the reversing turbine on account of the increased temperature generated, as the result of 

 the work done upon the steam by the rotor's movement in the opposite direction to the 

 flow of steam when the astern throttle is opened. There may be some slight action of this 

 kind, but the European turbine builders have not found it of enough importance to pro- 

 vide a means of reducing the temperature of the steam to the astern turbine, and in all of 

 the above-mentioned cases the full degree of superheat will be used on the astern turbine. 



In all, there have been approximately 2,000 vessels equipped with superheaters which 

 deliver steam within the temperature range above mentioned. About 75 per cent of these 

 vessels have reciprocating engines, and the use of superheated steam on reciprocating en- 

 gines dates back nearly twenty years. 



