The Babcock Test. 



61 



20 and 21) ; in cog-geared machines the bottles are al- 

 ways whirled at the speed which the number of turns 

 made by the crank would indicate. 



70. Power testers. For factory purposes, steam tur- 

 bine machines (figs. 22-24) are most satisfactory when 

 well made and well cared for. They should be pro- 

 vided with a speed indi- 

 cator and steam gauge, both 



for the purpose of knowing 

 that sufficient speed is at- 

 tained, and to prevent what 

 may be serious accidents 

 from a general smash-up, if 

 the turbine "runs wild" by 

 turning on too much steam. 

 The revolving wheel of the 

 tester should be made of FIG. 22. 

 wrought or malleable iron, or 

 of wire, so that it will not be broken by the centrifugal 

 force and cause accidents. The swinging pockets 

 which hold the test bottles in most machines should 

 be so made that the bottles will not strike the 

 center of the revolving frame when in a horizontal posi- 

 tion. Tests have often been lost by the end of the neck 

 catching at the center, the bottles thus failing to take 

 an upright position when the whirling stops. 



71. The exhaust steam pipe of turbine testers should 

 not have too many turns or be much reduced in size 

 from that of the opening in the tester. A free escape 

 of the exhaust steam is necessary to prevent the steam 

 from collecting in the test bottle chamber and overheat- 

 ing the test bottles when whirled (41). 



Type of Babcock steam 

 turbine testers. 



