222 STEAM EXGINES 



Effect of External Heat on Bearings. Bearings may get hot 

 by the application of external heat. This may be the case 

 if the engine is placed too near furnaces or an uncovered 

 boiler, or in an atmosphere heated by uncovered steam pipes 

 or other means. The excessive heat of the atmosphere 

 will then expand the brasses until they nip the journals, 

 which will generate additional heat and cause further expan- 

 sion of the brasses, and so on until a hot bearing is the 

 result. The remedy obviously depends upon the conditions 

 of each case. 



Brasses Too Long. If the brasses are too long and bear 

 against the collars of the journal when cold, they will mosjt 

 surely heat after the engine has been running a while. It is 

 hardly possible to run bearings stone cold. They will warm 

 up a little and the brasses will be expanded thereby, which 

 will cause them to bear still harder against the collars. This, 

 in turn, will induce greater friction and more expansion of the 

 brasses. The evil may be obviated by chipping or filing a little 

 off each end of the brasses until they cease to bear against the 

 collars while running. A little side play is a good thing for 

 another reason, which is that it promotes a better distribution 

 of the oil and prevents the journal and brasses from wearing 

 into concentric parallel grooves. 



Springing of Bedplate. If the bedplate of an engine is not 

 rigid enough to resist the vibration of the moving parts, or if 

 it is sprung by uneven settling or the instability of the founda- 

 tion, the engine will be thrown out of line either intermittently 

 or permanently, and the bearings will heat. But it will do no 

 good to refit the brasses unless the engine bed is stiffened in 

 some way and leveled up. 



Springing or Shifting of Pillow-Block. The effect of the 

 springing or shifting of the pedestal or pillow-block is similar 

 to the springing of the engine bed; that is, the bearing will 

 be thrown out of line, with the consequent danger of heating. 

 As the pedestal is usually adjustable, it is an easy matter to 

 readjust it, after which the holding-down bolts should be 

 screwed down hard. If a pedestal is not stiff enough to resist 

 the strains upon it and it springs, measures should be taken to 

 stiffen it. 





