166 APPLICATION OF STANDARDIZATION AND GRAPHICAL 



mine upon the dimensions of a boiler to give a predetermined heating surface. While 

 the determination of the heating and grate surface required ought to be based upon 

 actual steam consumption it is to be regretted that there exists very little published 

 data, determined by actual trial, as to the real consumption of steam by different 

 types of marine propelling machinery, or as to the actual evaporation of water by 

 boilers of the type under consideration. 



On the other hand, there are so many successful vessels in operation to-day 

 that the determination of the heating and grate surface is fairly simple, even though 

 methods are used which are perhaps not quite as scientific as they might be; and 

 while the possession of more accurate data might enable the designer to more 

 closely approximate his requirements with the actual performance of the boilers, in 

 merchant vessels reasonable excess of boiler power can never be considered a fault. 

 The life of a boiler constantly forced to the limit is bound to be shorter than 

 that of a boiler which readily keeps the machinery supplied with steam at a con- 

 stant pressure, and it would also appear that, where fires are forced, the losses due 

 to imperfect combustion would be greater. 



Another very probable cause for the failure of boilers to steam properly lies 

 in the fact that if the designer is limited to diameter of boiler he is apt to over- 

 estimate the amount of heating surface that can be placed in a boiler of a given 

 size; and while there is no doubt that the heating surface which is contained in 

 most boilers could be considerably increased by reducing the available steam space 

 or by crowding the tubes, it is very much to be doubted whether the boilers would 

 be improved thereby. 



The writer has come across cases where the heating surface had been increased 

 by keeping the tubes very close to the furnaces, and while the calculated heating 

 surface was thereby increased it is quite possible that the elimination of all the 

 tubes which were in close proximity to the furnaces would not have had any appre- 

 ciable efifect on the steaming qualities of the boiler. 



One of the causes of the great differences existing in designs lies in the fact 

 that prior to the war, when the individual shipyards of this country were engaged 

 on many different types of vessels at the same time, ranging from ferry-boats to 

 big passenger liners, the conditions were not favorable to the development of stand- 

 ard designs. 



A design for a lo- foot-diameter boiler might be followed by another for a 15- 

 foot boiler, and this again by a design for a 13-foot boiler. 



Each case being developed upon its own merits, it was to be expected that regu- 

 lar progression of the various proportions of different boilers would be given but 

 scant consideration, with the result that in some cases boilers of varying diameters 

 have had the same heating surface and diameter of furnace. 



With this condition in mind the writer at one time made a series of designs 

 progressing at the rate of 3 inches in diameter of boiler, which designs proved that 

 a regular progression of dimensions could be maintained and that the resultant de- 

 signs would have well-balanced proportions. 



