ENGINEERING GOSS. 



165 



maintenance of the locomotive. The values quoted in the preceding para- 

 graphs assume a high order of maintenance. If this is lacking, it may 

 easily happen that the saving which is anticipated through the adoption of 

 higher pressures will entirely disappear. 



(8) The diflSculties to be met in the maintenance both of boiler and cylin- 

 ders increase with increase of pressure. 



(9) The results supply an accurate measure by which to determine the 

 advantage of increasing the capacity of a boiler. For the development of a 

 given power, any increase in boiler capacity brings its return in improved 

 performance without adding to the cost of maintenance or opening any new 

 avenues for incidental losses. As a means to improvement, it is more cer- 

 tain than that which is offered by increase of pressure. 



Table 2. 



(10) As the scale of pressure is ascended an opportunity to further 

 increase the weight of a locomotive should in many cases find expression in 

 the design of a boiler of increased capacity rather than in one for higher 

 pressures. 



(11) Assuming i8o pounds pressure to be accepted as standard, and 

 assuming the maintenance to be of the highest order, it will be found good 

 practice to utilize any allowable increase in weight by providing a larger 

 boiler rather than by providing a stronger boiler to permit higher pressures. 



(12) Wherever the maintenance is not of the highest order the standard 

 running pressure should be below i8o pounds. 



(13) Wherever the water which must be used in boilers contains foaming 

 or scale-making admixtures, best results are likely to be secured by fixing 

 the running pressure below the limit of i8o pounds. 



(14) A simple locomotive using saturated steam will render good and 

 efl&cient service when the running pressure is as low as 1 60 pounds. Under 

 most favorable conditions no argument is to be found in the economic per- 

 formance of a machine which can justify the use of pressures greater than 

 200 pounds. 



