32 DISCUSSION ON MAY MEETING PAPERS. 



knots, due to cutting out the low-pressure turbine. The load carried on the starboard gear- 

 ing was, of course, higher than it should have been; but, on the other hand, this further 

 emphasizes the importance of conservative tooth loading. The unit pressures on the teeth 

 of this gear under normal conditions are 52 pounds for the high-speed and 58 for the low- 

 speed pinion. Under the emergency conditions the load on the teeth was increased about 

 30 per cent. The above pressure is the pressure per inch of face per inch of diameter. 



This accident also emphasizes the importance of cross compound turbines. As it was, 

 the loss of time was only about two days. With a single turbine the loss of time would prob- 

 ably have been over a month and with the possibility of a salvage claim in addition. 



Attention is called to Mr. Warriner's observations in regard to superheated steam, 

 which are fully concurred in. In Table II herewith a comparison is made between the 

 ordinary type of steam-engine installation and a steam-turbine installation using super- 

 heated steam. This table shows that the saving in weight is 133 tons; that the cost of the 

 turbine installation is about three-fourths of the engine, and that there is a saving of 32 

 per cent in fuel consumption. The economic advantages of the turbine are very great and 

 are too important to be ignored by American owners, and especially so since foreign owners 

 are rapidly adopting turbines with superheated steam. 



Table II. — Comparison Between Steam Engine with Saturated Steam and Steam Turbine 



with Superheated Steam,. 



For a cargo vessel of 11 knots speed, and 2,900 S. H. P. Deadweight capacity 10,000 tons. 



Engine. Turbine. 



Weight of machinery installation, net, tons 596 463 



Same, lbs. per S. H. P 461 358 



Cost of machinery installation in per cent 100 75.5 



Steam pressure at engine, lbs. gauge 200 200 



Superheat at engine, deg. F 200 



Vacuum, inches 26 28^4 



Steam consumption for all purposes per S. H. P., lbs 16.8 11.5 



Fuel oil consumption per S. H. P., lbs 1.25 .85 



Same in per cent 100 68 



It is also possible to reduce the steam consumption of steam engines by using super- 

 heated steam. By using 200° superheat in the steam-engine vessel given in the table, the fuel 

 consumption would be reduced about 17 per cent. 



The comparison given by Mr. Warriner on page 19 is of great interest. We have made 

 a number of comparisons of this kind which verify closely the data given, with due con- 

 sideration to the type of installation. It should be noted, however, that this comparison is 

 based on a twin-screw installation, which is considerably different from the single-screw 

 installations of most cargo vessels. In addition to this the comparison, as pointed out, is 

 unfavorable to the geared-turbine machinery, since the boilers and auxiliaries are consider- 

 ably larger than required. 



It should also be noted that the oil engines are of the two-cycle type. The weight 

 of this installation is less and the fuel consumption greater than for the four-cycle type. 



The length of the round voyage is not given, but I presume it is about 10,000 miles. 

 This feature has a considerable influence on the expenses and earnings. 



