68 PROGRESS IN TURBINE SHIP PROPULSION. 



The engineer of our large central stations is subject to keen competition and 

 is confronted almost solely with the problem of producing reliable energy for the 

 least cost, including fixed charges. He has before him daily statements showing his 

 overall power costs with a high degree of accuracy, resulting in considerable suc- 

 cess on his part in the production of low power costs. 



It is therefore not unreasonable that the marine engineer might look to the cen- 

 tral station engineer for advancement from some of the latter's best practice. It 

 is of course understood that complete standby machinery is not available for the 

 marine engineer, neither can the superintending engineer direct those in immediate 

 charge of the machinery by frequent visits. Hence there is the more urgent call 

 for the greatest reliability and simplicity of the marine installation; though, after 

 all, perhaps not more than that which the central stations have in our big cities. 

 An interruption to service, however brief, is regarded most seriously. 



FEED WATER HEATING SYSTEMS. 



It is common practice on shipboard to provide a closed or tubular heater to 

 which is led the exhaust steam from the auxiliary machinery, which latter exhausts 

 at a pressure between 5 and 10 pounds gauge. The exhaust system is provided 

 with a connection to let any proportion of this steam to the condenser. Some- 

 times again there is a hand valve, permitting any surplus of this steam to be taken 

 to a low pressure stage of the turbine, all of which calls for hand manipulation 

 where the conditions are sometimes quite variable, owing to more or less inter- 

 mittent operation of the feed pump. Sometimes the connection to the condenser 

 is provided with a spring loaded valve so that when the exhaust pressure reaches 

 a predetermined pressure, higher than that within the condenser, steam may pass 

 to the condenser. The construction of the valves usually employed is such that 

 the higher the pressure in the condenser, the higher is the pressure at which the 

 steam will pass to the condenser, which is of course undesirable. A system which 

 will automatically maintain a predetermined temperature in the feed heater at 

 all times, bleeding the main turbine for this purpose, at high powers if necessary, 

 and at the same time automatically permit any surplus steam not condensed in the 

 feed water heater to do useful work in the turbine, is much to be desired. 



Heat balance systems have for some time been available for land purposes, 

 there being provided automatic valves so that whenever there is a surplus of auxil- 

 iary exhaust steam this surplus may pass through a low pressure stage of the tur- 

 bine, doing work therein at the rate of 20 to 22 pounds per horse-power. Other 

 types of valves are available for land installations which will not only take surplus 

 steam into the turbine at times of light loads on the main unit at which time the 

 auxiliaries will obviously furnish too much exhaust steam ; but, on the other hand, 

 they are arranged to deliver steam from the turbine to the feed water heater at 

 times of heavy loads when the stage pressures in the turbine are relatively high and 

 there is a deficiency of steam for feed water heating. The latter should particu- 



