METHODS TO CYLINDRICAL RETURN TUBULAR BOILERS. 169 



writer would again point to the comparative scarcity of published data on the per- 

 formance and eflkiency of Scotch boilers. 



The different authorities on the subject give figures for heating surface re- 

 quired that vary widely, and there is no doubt that the tendency to keep the boilers 

 too small is somewhat of a temptation when costs have to be kept down. 



After all, the most reliable data for desigiiing boilers are not the result of build- 

 ers' trials when all conditions are favorable, but rather the average result of actual 

 long voyages of vessels which are no longer new but which have been in operation 

 some time. 



There is no doubt but that it might mean some expense to the shipowner to 

 obtain these results, as in many vessels the apparatus for indicating the engines is 

 taken down after the builders' trials and never used again. On the other hand, a 

 careful investigation of the performance of a vessel not giving satisfactory service 

 would probably result in the adverse conditions being eliminated, with consequent 

 advantage to the owners. 



As a guide to what can be accomplished the writer offers the following data 

 taken from actual performance during long voyages of a tramp steamer: — 



Boiler's. Auxiliaries. 



No Two Air pump Lever driven 



Type S. E. cyl. ret. tubular Circulating pump Lever driven 



Draft Howdens Feed pump Lever driven 



Heating surface total, 4,464 square feet Bilge pumps Lever driven 



Grate surface total. . . . 104 square feet Blower engine, 



Mi|i 44 square feet . Independent reciprocating 



G. S. Electric generator, 



Independent reciprocating 

 Steering engine Independent 



Engines. Consiimption of Fuel. 



Cylinders 24-60-67 Type of coal Welsh 



Stroke 45 Coal in 24 hours 24 tons 



Average revolutions 65 I. H. P. per sq. ft. grate surface. . 15.4 



Pressure at throttle 195 Coal per I. H. P. 1.4 lbs. 



I. H. P 1,600 Air pressure at blower i^-inch 



The above figures are given as the writer is thoroughly familiar with the par- 

 ticular case and knows that this vessel gave very satisfactory results on voyages 

 of from eighteen to twenty-one days' duration from port to port. 



In addition to the diagrams giving the characteristics of designs of a series of 

 boilers, the writer has added diagrams for obtaining the weight of material enter- 

 ing into construction of a boiler and also the weight of water. 



The weights of materials are gross weights and do not include fittings. 



